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991.
Dr. Karel Jeřábek Prof. Marco Zecca Dr. Paolo Centomo Federico Marchionda Dr. Luca Peruzzo Dr. Patrizia Canton Dr. Enrico Negro Prof. Vito Di Noto Prof. Benedetto Corain 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(28):9381-9387
Hyper‐cross‐linked resins stemming from a gel‐type poly‐chloromethylated poly(styrene‐co‐divinylbenzene) resin (GT) have been investigated by a multi‐methodological approach based on elemental analysis, scanning electron microscopy, X‐ray microanalysis, and solvent absorption. The hyper‐cross‐linking of the parent resin was accomplished by Friedel–Crafts alkylation of the phenyl rings of the resins with the chloromethyl groups. This produced a permanent pore system comprising both micropores (<2.0 nm in diameter) and mesopores (2.2 nm). The chloromethyl groups that did not react in the hyper‐cross‐linking step were transformed into methylmercaptan groups and the latter were then converted into sulfonic groups by oxidation with hydrogen peroxide. By this procedure the extensive permanent porosity of the parent unsulfonated hyper‐cross‐linked polymer (HGT) was retained by the sulfonated polymer (HGTS). The final exchange capacity of HGTS was determined to be 0.36 mmol g?1. HGTS was easily metalated with PdII and the subsequent reduction of the metal centers with either aqueous sodium borohydride, formaldehyde, or dihydrogen produced three Pd0/HGTS nanocomposites. The metal nanoparticles had diameters in the 1–6 nm range for all the nanocomposites, as determined by TEM, but with somewhat different distributions. When formaldehyde was used, more than 90 % of the nanoparticles were less than 3 nm and their radial distribution throughout the polymer beads was quite homogeneous. These findings show that with this reducing agent the metal nanoparticles are generated within the pore system of the polymer matrix, hence their size is controlled by the dimensions of the pores of the polymeric support. 相似文献
992.
Giuliana Blasi Annalisa Petruzzelli Donatella Ottaviani Stefano Fisichella Enrico Di Raimo Andrea Valiani Marinella Capuccella Stefania Scuota M. Naceur Haouet 《Accreditation and quality assurance》2013,18(2):143-148
The validation of food microbiology methods and assessment of measurement uncertainty are required for laboratories operating EN ISO/IEC 17025 accreditation systems. This paper aims to describes the statistical approach adopted by a multi-site laboratory to satisfy these requirements and to routinely check the performance of the methods. A validation protocol was performed, reflecting a great variability of experimental conditions, represented by the period of time during which determinations were made, the different laboratories concerned, the large number of technicians involved, the differences in the level of contamination of the matrix analyzed and the operating conditions (equipment, reagents, culture media, environmental conditions, etc.). Despite the very high variability of the experimental conditions, the values of repeatability and reproducibility obtained for the methods were lower than those stated in the respective regulations. In addition, the top-down approach adopted in this study is to be considered effective overtime and allows to randomize all variable factors, including the effects of sensitivity and specificity, in order to simulate the conditions of real reproducibility. A specific Excel spreadsheet was also developed for the routine expression of analytical results. This spreadsheet represents a very useful tool for operators to calculate and routinely check the results, as well as to assess the uncertainty of measurement. This particular quality assessment system is enabling the multi-site laboratory to implement the accuracy, reliability and comparability of the analytical results and to ensure the analytical control of data output. 相似文献
993.
Stefano Banfi Enrico Caruso Marzia Gariboldi Stefano Alemani Gianluca Nasini Ezio Bombardelli 《合成通讯》2013,43(7):1096-1109
A series of 5,10,15,20‐tetraarylporphyrins covalently linked to anthraquinones belonging to the class of emodin were synthesized following two different pathways. The first method exploits the functionalization of the methyl group in position 6 of O‐protected emodins, which can be converted either into a carboxylic acid or into a bromo‐methyl derivative. The modified emodins were then bound through amido or ether bonds to one of the tetraarylporphyrins meso phenyl rings bearing an amino or hydroxyl group, respectively. An alternative synthesis exploits the mixed condensation of triacetoxy‐emodinaldehyde (or trimethoxy‐emodinaldehyde) with pyrrole in the presence of variable amounts of benzaldehyde, thus affording two similar 5‐emodin‐10,15,20‐triphenylporphyrins differing from one another in the emodin hydroxyl group protection. These compounds are characterized by direct conjugation of the emodin moiety to the tetrapyrrolic ring. Preliminary experiments were performed in vitro on the human colon adenocarcinoma cell line HCT116 to evaluate the photocytotoxicity of the new compounds. 相似文献
994.
Serena Dipierro Andrea Pinamonti Enrico Valdinoci 《Journal of Functional Analysis》2019,276(3):785-814
We consider stable solutions of semilinear equations in a very general setting. The equation is set on a Polish topological space endowed with a measure and the linear operator is induced by a carré du champs (equivalently, the equation is set in a diffusion Markov triple).Under suitable curvature dimension conditions, we establish that stable solutions with integrable carré du champs are necessarily constant (weaker conditions characterize the structure of the carré du champs and carré du champ itéré).The proofs are based on a geometric Poincaré formula in this setting. From the general theorems established, several previous results are obtained as particular cases and new ones are provided as well. 相似文献
995.
Rubino FM Pitton M Di Fabio D Meroni G Santaniello E Caneva E Pappini M Colombi A 《Biomedical chromatography : BMC》2011,25(3):330-343
S‐methylcysteine (SMC) is a minor amino acid naturally excreted in human urine, a protective agent against oxidative stress and a biotransformation product of the fumigant biocide methyl bromide and of nicotine. A metabolic source of SMC is catabolism of the repair catalytic protein MGMT (EC 2.1.1.37), which specifically removes the methyl group from the modified DNA nucleotide O‐6‐methyl‐guanine to revert the normal GC base pairing. To assess the value of SMC and of S‐methylmercapturic acid (SMMA) as candidate biomarkers of proliferative phenomena, a sensitive analytical method by GC‐MS was applied in a pilot study of healthy subjects to assess their urinary elimination and the intra‐ and inter‐individual variability. Extractive alkylation with butylchloroformate‐n‐butanol‐pyridine (Husek technique) was employed for sample derivatization and isotope dilution GC‐MS with S‐[CD3]‐SMC and ‐SMMA was applied for specific and sensitive detection. To resolve the target analytes from the main coeluting interferents in the derivatized urine extract a medium‐polarity stationary phase was employed. SMMA was not detected in the morning urine of three healthy fertile‐age women followed for one month above the minimum detectable level of approx. 500 µg/L while SMC concentrations were in the 0.02–0.7 µg/mL range (n = 61) with large inter‐day and inter‐individual variations. In a young healthy male urine samples taken throughout a few days yielded concentrations in the same 90–810 µg/L range (n = 11). These preliminary results points at SMC as a candidate biomarker for the study of methylation turnover in several biochemical processes. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
996.
D'Angelo P Zitolo A Migliorati V Bodo E Aquilanti G Hazemann JL Testemale D Mancini G Caminiti R 《The Journal of chemical physics》2011,135(7):074505
X-ray absorption spectroscopy (XAS) has been used to unveil the bromide ion local coordination structure in 1-alkyl-3-methylimidazolium bromide [C(n)mim]Br ionic liquids (ILs) with different alkyl chains. The XAS spectrum of 1-ethyl-3-methylimidazolium bromide has been found to be different from those of the other members of the series, from the butyl to the decyl derivatives, that have all identical XAS spectra. This result indicates that starting from 1-buthyl-3-methylimidazolium bromide the local molecular arrangement around the bromide anion is the same independently from the length of the alkyl chain, and that the imidazolium head groups in the liquid ILs with long alkyl chains assume locally the same orientation as in the [C(4)mim]Br crystal. With this study we show that the XAS technique is an effective direct tool for unveiling the local structural arrangements around selected atoms in ILs. 相似文献
997.
Giorgina Corongiu Enrico Clementi 《International journal of quantum chemistry》2011,111(14):3517-3540
We present 140 accurate potential energy curves, PECs, for the Σ, Π, Δ, ?, and Γ manifolds for the H2 molecule, mapping all the states with energy below the H ground state. The full configuration interaction, nonrelativistic Born–Oppenheimer computations are performed with large and optimized basis sets of Slater‐type and spherical Gaussian functions; these new basis sets are somewhat larger than those used in recent published studies on the 60 Σ state PECs. The full CI computations are performed twice, with Hartree–Fock and with Heitler–London‐type functions, allowing the identification of the ionic component in the total energy. The computed energies are within 10?5 hartree from the most accurate PECs in literature. We aim (a) at the evaluation of the PECs starting at very short and unexplored internuclear distances (0.01 bohrs) and ending at full dissociation, (b) at the systematic prediction of high excited state PECs dissociating as 1s + 4l and 1s + 5l, and (c) at the characterization of the evolution of the 140 PEC electronic densities from united atom to dissociation. With this work we fill a gap in today literature, which has dealt mainly with low excited states, generally excluding short internuclear distances. The electronic configuration at the united atom persists as dominant configuration well beyond the equilibrium separation, and it switches to that at dissociation often with energy patterns seemingly irregular, in particular when the values of the principal quantum number at dissociation and at the united atom differ by one or more unit. The Hund's singlet‐triplet splitting, which propagates from the united atom to the molecule, is discussed. The singlet and triplet states are rather close in energy in the Π manifolds, and approach degeneracy in the Δ and ? manifolds, to become fully degenerate in the Γ manifolds. Discussions on the correlation energy correction, adiabatic correction, spectroscopic constants and on general features of the H2 excited states are presented. The H2 molecule is a system, which—to be understood—needs consideration of both the very short internuclear distances in approaching the united atom and of the very high excited states below H. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 相似文献
998.
Della Gaspera E Karg M Baldauf J Jasieniak J Maggioni G Martucci A 《Langmuir : the ACS journal of surfaces and colloids》2011,27(22):13739-13747
In this work, we provide a detailed study of the influence of thermal annealing on submonolayer Au nanoparticle deposited on functionalized surfaces as standalone films and those that are coated with sol-gel NiO and TiO(2) thin films. The systems are characterized through the use of UV-vis absorption, X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), and spectroscopic ellipsometry. The surface plasmon resonance peak of the Au nanoparticles was found to red-shift and increase in intensity with increasing surface coverage, an observation that is directly correlated to the complex refractive index properties of Au nanoparticle layers. The standalone Au nanoparticles sinter at 200 °C, and a relationship between the optical properties and the annealing temperature is presented. When overcoated with sol-gel metal oxide films (NiO, TiO(2)), the optical properties of the Au nanoparticles are strongly affected by the metal oxide, resulting in an intense red shift and broadening of the plasmon band; moreover, the temperature-driven sintering is strongly limited by the metal oxide layer. Optical sensing tests for ethanol vapor are presented as one possible application, showing reversible sensing dynamics and confirming the effect of Au nanoparticles in increasing the sensitivity and in providing a wavelength dependent response, thus confirming the potential use of such materials as optical probes. 相似文献
999.
Sedlmaier SJ Mugnaioli E Oeckler O Kolb U Schnick W 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(40):11258-11265
The oxonitridophosphate SrP3N5O has been synthesized by heating a multicomponent reactant mixture that consisted of phosphoryl triamide OP(NH2)3, thiophosphoryl triamide SP(NH2)3, SrS, and NH4Cl enclosed in evacuated and sealed silica‐glass ampoules up to 750 °C. The compound was obtained as nanocrystalline powder with needle‐shaped crystallites. The crystal structure was solved ab initio on the basis of electron diffraction data by means of automated electron diffraction tomography (ADT) and verified by Rietveld refinement with X‐ray powder diffraction data. SrP3N5O crystallizes in the orthorhombic space group Pnma (no. 62) with unit‐cell data of a=18.331(2), b=8.086(1), c=13.851(1) Å and Z=16. The compound is a highly condensed layer phosphate with a degree of condensation κ=1/2. The corrugated layers ${{{\hfill 2\atop \hfill \infty }}}The oxonitridophosphate SrP(3)N(5)O has been synthesized by heating a multicomponent reactant mixture that consisted of phosphoryl triamide OP(NH(2))(3), thiophosphoryl triamide SP(NH(2))(3), SrS, and NH(4)Cl enclosed in evacuated and sealed silica-glass ampoules up to 750 °C. The compound was obtained as nanocrystalline powder with needle-shaped crystallites. The crystal structure was solved ab initio on the basis of electron diffraction data by means of automated electron diffraction tomography (ADT) and verified by Rietveld refinement with X-ray powder diffraction data. SrP(3)N(5)O crystallizes in the orthorhombic space group Pnma (no. 62) with unit-cell data of a=18.331(2), b=8.086(1), c=13.851(1) ? and Z=16. The compound is a highly condensed layer phosphate with a degree of condensation κ=?. The corrugated layers (∞)(2){(P(3)N(5)O)(2-)} consist of linked, triangular columns built up from P(O,N)(4) tetrahedra with 3-rings and triply binding nitrogen atoms. The Sr(2+) ions are located between the layers and exhibit six-, eight-, and ninefold coordination. FTIR and solid-state NMR spectra of SrP(3)N(5)O are discussed as well. 相似文献
1000.
Denysenko D Grzywa M Tonigold M Streppel B Krkljus I Hirscher M Mugnaioli E Kolb U Hanss J Volkmer D 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(6):1837-1848
A highly porous member of isoreticular MFU‐4‐type frameworks, [Zn5Cl4(BTDD)3] (MFU‐4l(arge)) (H2‐BTDD=bis(1H‐1,2,3‐triazolo[4,5‐b],[4′,5′‐i])dibenzo[1,4]dioxin), has been synthesized using ZnCl2 and H2‐BTDD in N,N‐dimethylformamide as a solvent. MFU‐4l represents the first example of MFU‐4‐type frameworks featuring large pore apertures of 9.1 Å. Here, MFU‐4l serves as a reference compound to evaluate the origin of unique and specific gas‐sorption properties of MFU‐4, reported previously. The latter framework features narrow‐sized pores of 2.5 Å that allow passage of sufficiently small molecules only (such as hydrogen or water), whereas molecules with larger kinetic diameters (e.g., argon or nitrogen) are excluded from uptake. The crystal structure of MFU‐4l has been solved ab initio by direct methods from 3D electron‐diffraction data acquired from a single nanosized crystal through automated electron diffraction tomography (ADT) in combination with electron‐beam precession. Independently, it has been solved using powder X‐ray diffraction. Thermogravimetric analysis (TGA) and variable‐temperature X‐ray powder diffraction (XRPD) experiments carried out on MFU‐4l indicate that it is stable up to 500 °C (N2 atmosphere) and up to 350 °C in air. The framework adsorbs 4 wt % hydrogen at 20 bar and 77 K, which is twice the amount compared to MFU‐4. The isosteric heat of adsorption starts for low surface coverage at 5 kJ mol?1 and decreases to 3.5 kJ mol?1 at higher H2 uptake. In contrast, MFU‐4 possesses a nearly constant isosteric heat of adsorption of ca. 7 kJ mol?1 over a wide range of surface coverage. Moreover, MFU‐4 exhibits a H2 desorption maximum at 71 K, which is the highest temperature ever measured for hydrogen physisorbed on metal–organic frameworks (MOFs). 相似文献