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161.
Ortiz M Torréns M Fragoso A O'Sullivan CK 《Analytical and bioanalytical chemistry》2012,403(1):195-202
In this paper, we describe the development of an enzyme-linked oligonucleotide assay for the detection of a human leukocyte
antigen allele associated with celiac disease based on cyclodextrin-modified polymeric surfaces. The surface of maleimide-pre-coated
plates was modified with a layer of thiolated cyclodextrin polymer and used for the supramolecular capture of adamantane or
ferrocene-modified carboxymethylcellulose polymers bearing DNA probes. The assay was optimised in terms of incubation time,
temperature, and surface chemistry and applied to the highly sensitive and selective detection of HLA sequences with a limit
of detection of 0.7 nM. A real sample analysed using this platform showed an excellent correlation with maleimide-activated
plates using thiolated DNA probes. 相似文献
162.
Nanograin sizes and crystal lattice microstrains in nanocrystalline materials are typically evaluated from the broadening of their x-ray diffraction (XRD) peaks under the assumption of symmetrical diffraction profiles. Since this assumption is not entirely satisfactory, we formulate a line-broadening analysis model of a single peak that considers explicitly the XRD peak asymmetry. The model is a generalization of the variance method in which the shape of the XRD peaks is idealized through asymmetrical split pseudo-Voigt functions. The model is validated on two nanocrystalline powders. 相似文献
163.
Zaragoza A Teruel JA Aranda FJ Marqués A Espuny MJ Manresa Á Ortiz A 《Langmuir : the ACS journal of surfaces and colloids》2012,28(2):1381-1390
One major application of surfactants is to prevent aggregation during various processes of protein manipulation. In this work, a bacterial trehalose lipid (TL) with biosurfactant activity, secreted by Rhodococcus sp., has been identified and purified. The interactions of this glycolipid with selected model proteins have been studied by using differential scanning calorimetry (DSC), Fourier-transform infrared (FTIR) spectroscopy, isothermal titration calorimetry (ITC), and fluorescence spectroscopy. Bovine serum albumin (BSA) and cytochrome c (Cyt-c) have been chosen because of their quite different secondary structures: BSA contains essentially no β-sheets and an average 66% α-helix, whereas Cyt-c possesses up to 25% β-sheets and up to 45% α-helical structure. Differential scanning calorimetry shows that addition of TL to BSA at concentrations below the critical micelle concentration (cmc) shifts the thermal unfolding temperature to higher values. FTIR indicates that TL does not alter the secondary structure of native BSA, but the presence of TL protects the protein toward thermal denaturation, mainly by avoiding formation of β-aggregates. Studies on the intrinsic Trp fluorescence of BSA show that addition of TL to the native protein results in conformational changes. BSA unfolding upon thermal denaturation in the absence of TL makes the Trp residues less accessible to the quencher, as shown by a decrease in the value of Stern-Volmer dynamic quenching constant, whereas denaturation in the presence of the biosurfactant prevents unfolding, in agreement with FTIR results. In the case of Cyt-c, interaction with TL gives rise to a new thermal denaturation transition, as observed by DSC, at temperatures below that of the native protein, therefore facilitating thermal unfolding. Binding of TL to native BSA and Cyt-c, as determined by ITC, suggests a rather nonspecific interaction of the biosurfactant with both proteins. FTIR indicates that TL slightly modifies the secondary structure of native Cyt-c, but protein denaturation in the presence of TL results in a higher proportion of β-aggregates than in its absence (20% vs 3.9%). The study of Trp fluorescence upon TL addition to Cyt-c results in a completely opposite scenario to that described above for BSA. In this case, addition of TL considerably increases the value of the dynamic quenching constant, both in native and denatured protein; that is, the interaction with the glycolipid induces conformational changes which facilitate the exposure of Trp residues to the quencher. Considering the structures of both proteins, it could be derived that the characteristics of TL interactions, either promoting or avoiding thermal unfolding, are highly dependent on the protein secondary structure. Our results also suggest the rather unspecific nature of these interactions. These might well involve protein hydrophobic domains which, being buried into the protein native structures, become exposed upon thermal unfolding. 相似文献
164.
We present a time-reversal invariant s-wave superconductor supporting Majorana edge modes. The multiband character of the model together with spin-orbit coupling are key to realizing such a topological superconductor. We characterize the topological phase diagram by using a partial Chern number sum, and show that the latter is physically related to the parity of the fermion number of the time-reversal invariant modes. By taking the self-consistency constraint on the s-wave pairing gap into account, we also establish the possibility of a direct topological superconductor-to-topological insulator quantum phase transition. 相似文献
165.
Maria J. Ortiz Antonia R. Agarrabeitia Gonzalo Duran-Sampedro Jorge Bañuelos Prieto Teresa Arbeloa Lopez Walter A. Massad Hernán A. Montejano Norman A. García Iñigo Lopez Arbeloa 《Tetrahedron》2012,68(4):1153-1162
A theoretical and experimental study on the iodination of BODIPY dyes with different degrees of substitution has been developed. Polyhalogenated BODIPYs synthesized in this work are the first examples of this type of dyes with more than two halogen atoms in the BODIPY core and they can be selectively functionalized. Surprisingly, the position in which halogen is attached has a marked effect in the photophysical properties and modulates the fluorescence capacity of the resulting BODIPY. These iodinated BODIPYs are efficient singlet oxygen generators. 相似文献
166.
Yahia Didane Rocio Ponce Ortiz Jian Zhang Keijyu Aosawa Toshinori Tanisawa Hecham Aboubakr Frédéric Fages Jörg Ackermann Noriyuki Yoshimoto Hugues Brisset Christine Videlot-Ackermann 《Tetrahedron》2012,68(24):4664-4671
Solution and solid-state properties of two new perfluoroalkyl end-substituted analogues of distyryl-bithiophene (CF3-DS2T and diCF3-DS2T) are presented. Vacuum deposited thin films were investigated by atomic force microscopy, X-ray diffraction, and implemented as active layers into organic thin film transistors. While physicochemical measurements in solution suggest a preferential hole injection and transport inside CF3-DS2T and diCF3-DS2T films, electrical measurements performed under high vacuum show that CF3-DS2T behaves as n-type semiconductor while no charge transport was measured in diCF3-DS2T. The results highlighted the importance of substituents on conjugated backbone and on the resulting fine ordering in solid state to control the charge transport. 相似文献
167.
María A. Ramírez Gisela M. Ortiz Alejandra Salerno Isabel A. Perillo María M. Blanco 《Tetrahedron letters》2012,53(11):1367-1369
In this work, we describe the synthesis of a series of 1,2,3-trisubstituted-1,4,5,6,7,8-hexahydro-1,3-diazocinium salts (1) by alkylation of the corresponding 1,2-diaryl-1,4,5,6,7,8-hexahydro-1,3-diazocines (2). Compounds 2 were obtained by ethyl polyphosphate-promoted cyclocondensation of N-aroyl-N′-arylpentamethylenediamines (3). Reaction of compounds 2 with alkyl iodides led to 1,2,3-trisubstituted 1,4,5,6,7,8-hexahydro-1,3-diazocinium iodides (1), a new family of cyclic amidinium salts. The best yields for the alkylation were achieved using a mixture of DCM–DMSO (10:1) as solvent. The reaction times of both, the cyclocondensation of compounds 3 and the reaction of 2 with alkyl halides, are dramatically decreased when using microwave irradiation. 相似文献
168.
el Hajjouji H Belmonte E García-López J Fernández I Iglesias MJ Roces L García-Granda S El Laghdach A López Ortiz F 《Organic & biomolecular chemistry》2012,10(29):5647-5658
ortho-Lithiation of N,N-diisopropyl-P,P-diphenylphosphinothioic amide using n-BuLi in the presence of TMEDA in diethyl ether followed by electrophilic trapping is described as an efficient method for the synthesis of ortho-functionalised derivatives in high yields. The structural modification of the phosphinothioic amide includes C-X (X = P, S, Si, Sn, I) and C-C bond forming reactions with a large variety of electrophiles. Additional applications based on functional group transformations are also reported. They include imine formation, desulfurization and Suzuki cross-coupling reactions on selected compounds. 相似文献
169.
Recently measured photoelectron spectra of the Na(3)O(-) anion have been interpreted with the aid of ab initio electron propagator calculations. As in the case of the Li(3)O(-), we propose that the photoionization of ground and excited neutral states, in a sequential two photon absorption mechanism, plays a role in the interpretation of the observed spectrum. The lowest vertical electron detachment energy of Na(3)O(-) corresponds to a Dyson orbital that is composed chiefly of diffuse Na s functions and connects a D(3h) singlet anion to an uncharged species with the same point group. Electron binding energies of isomers of the anion with different point groups or multiplicities have been considered. The relative magnitudes of the ionization energies of the neutral Li(3)O and Na(3)O species are also discussed. Whereas the most recent experimental data hold that Na(3)O has the higher ionization energy, this work asserts the opposite trend. 相似文献
170.
C. J. Larsen M. Ortiz C. L. Richardson 《Archive for Rational Mechanics and Analysis》2009,193(3):539-583
Crack fronts play a fundamental role in engineering models for fracture: they are the location of both crack growth and the
energy dissipation due to growth. However, there has not been a rigorous mathematical definition of crack front, nor rigorous
mathematical analysis predicting fracture paths using these fronts as the location of growth and dissipation. Here, we give
a natural weak definition of crack front and front speed, and consider models of crack growth in which the energy dissipation
is a function of the front speed, that is, the dissipation rate at time t is of the form
where F(t) is the front at time t and v is the front speed. We show how this dissipation can be used within existing models of quasi-static fracture, as well as
in the new dissipation functionals of Mielke–Ortiz. An example of a constrained problem for which there is existence is shown,
but in general, if there are no constraints or other energy penalties, this dissipation must be relaxed. We prove a general
relaxation formula that gives the surprising result that the effective dissipation is always rate-independent. 相似文献