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351.
Staluszka J Steblecka M Szajdzinska-Pietek E Kohl I Salzmann CG Hallbrucker A Mayer E 《The journal of physical chemistry. A》2008,112(37):8678-8685
Hyperquenched glassy water (HGW) has been suggested as the best model for liquid water, to be used in low-temperature studies of indirect radiation effects on dissolved biomolecules (Bednarek et al. J. Am. Chem. Soc. 1996, 118, 9387). In the present work, these effects are examined by X-band electron spin resonance spectroscopy (ESR) in gamma-irradiated HGW matrix containing 2'-deoxyguanosine-5'-monophosphate. Analysis of the complex ESR spectra indicates that, in addition to OH(*) and HO2(*) radicals generated by water radiolysis, three species are trapped at 77 K:(i) G(C8)H(*) radical, the H-adduct to the double bond at C8; (ii) G(- *) radical anion, the product of electron scavenging by the aromatic ring of the base; and (iii) dR(-H)(*) radicals formed by H abstraction from the sugar moiety, predominantly at the C'5 position. We discuss the yields of the radicals, their thermal stability and transformations, as well as the effect of photobleaching. This study confirms our earlier suggestion that in HGW the H atom addition/abstraction products are created at 77 K in competition with HO2(*) radicals, in a concerted process following ionization of water molecule at L-type defect sites of the H-bonded matrix. The lack of OH(*) reactivity toward the solute suggests that the H-bonded structure in HGW is much more effective in recombining OH(*) radicals than that of aqueous glasses obtained from highly concentrated electrolyte solutions. Furthermore, complementary experiments for the neat matrix have provided evidence that HO2(*) radicals are not the product of H atom reaction with molecular oxygen, possibly generated by ultrasounds used in the process of sample preparation. 相似文献
352.
Brasuń J Cebrat M Sochacka A Gładysz O Swiatek-Kozłowska J 《Dalton transactions (Cambridge, England : 2003)》2008,(37):4978-4980
A new vasopressin analogue, [His(1,6)]AVP, was synthesized and characterized by potentiometric measurements as well as by UV-Vis, CD and EPR spectroscopy. At the physiological pH the peptide forms a stable complex with Cu(2+) ions which is characterized by the {NH(2), N(Im), N(Im(macrochelate))} binding mode. The replacement of both Cys by His residues in the vasopressin sequence results in a very significant increase in the efficiency of Cu(2+) binding. 相似文献
353.
Marlien van Mever Magdalena Fabjanowicz Maricruz Mamani-Huanca Ángeles López-Gonzálvez Justyna Płotka-Wasylka Rawi Ramautar 《Electrophoresis》2022,43(18-19):1814-1821
The composition of wine is determined by a complex interaction between environmental factors, genetic factors (i.e., grape varieties), and winemaking practices (including technology and storage). Metabolomics using NMR spectroscopy, GC-MS, and/or LC-MS has shown to be a useful approach for assessing the origin, authenticity, and quality of various wines. Nonetheless, the use of additional analytical techniques with complementary separation mechanisms may aid in the deeper understanding of wine's metabolic processes. In this study, we demonstrate that CE-MS is a very suitable approach for the efficient profiling of polar ionogenic metabolites in wines. Without using any sample preparation or derivatization, wine was analyzed using a 10-min CE-MS workflow with interday RSD values for 31 polar and charged metabolites below 3.8% and 23% for migration times and peak areas, respectively. The utility of this workflow for the global profiling of polar ionogenic metabolites in wine was evaluated by analyzing different cool-climate Polish wine samples. 相似文献
354.
355.
J. N. Latosińska M. Latosińska M. A. Tomczak J. Seliger V. Žagar J. K. Maurin 《Magnetic resonance in chemistry : MRC》2012,50(2):89-105
Two antibacterial and antifungal agents, chloroxylenol (4‐chloro‐3,5‐dimethyl‐phenol) and triclosan (5‐chloro‐2‐(2’,4’‐dichlorophenoxy)‐phenol), were studied experimentally in solid state with an X‐ray, 35Cl‐nuclear quadrupole resonance (NQR) and 17O‐nuclear quadrupole double resonance (NQDR) spectroscopies and, theoretically, with the density functional theory/quantum theory of atoms in molecules (DFT/QTAIM). The crystallographic structure of triclosan, which crystallises in space group P31 with one molecule in the asymmetric unit [a = 12.64100(10), b = 12.64100(10), c = 6.71630(10) Å], was solved with an X‐ray and refined to a final R‐factor of 2.81% at room temperature. The NQR frequencies of 35Cl and 17O were detected with the help of the density functional theory (DFT) assigned to particular chlorine and oxygen sites in the molecules of both compounds. The NQR frequencies at 35Cl sites in chloroxylenol and triclosan were found to be more differentiated than frequencies at the 17O site. The former better describes the substituent withdrawing effects connected to π‐electron delocalization within the benzene rings and the influence of temperature; whereas, those at the 17O site provide more information on O‐H bond and intermolecular interactions pattern. The conformation adopted by diphenyl ether of triclosan in solid state was found to be typical of diphenyl ethers, but the opposite to those adopted when it was bound to different inhibitors. According to an X‐ray study, temperature had no effect on the conformation of the diphenyl ring of triclosan, which was the same at 90 K and at room temperature (RT). The scattering of NQR frequencies reproduced by the DFT under assumption of the X‐ray data at 90 K and RT is found to be a good indicator of the quality of resolution of the crystallographic structure. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
356.
Intramolecular Ti-mediated alkene-amide couplings of a range of N-alk-3-enyl amides fitted with a substituent at the homoallylic position are described. CF3-substituted compounds are suitable substrates and bicyclic aminocyclopropanes bearing a CF3 group can be prepared in this way. Good diastereoselectivities can be observed depending on the substitution pattern, and best results are obtained in diethyl ether rather than in THF. 相似文献
357.
Aequationes mathematicae - Let X, Y be linear spaces over a field $${\mathbb {K}}$$ . Assume that $$f :X^2\rightarrow Y$$ satisfies the general linear equation with respect to the first... 相似文献
358.
Ravon U Aguado S Pawlesa J Bergeret G Tagliabue M Zanardi S Rizzo C Paillaud JL Farrusseng D 《Combinatorial chemistry & high throughput screening》2012,15(2):152-160
Combinatorial screening using precipitation methods at room temperature can lead to a great diversity of carboxylate based Metal Organic Frameworks (MOFs) including already known or original porous solids. The investigation of the synthesis of MOFs in different solvent and solvent mixtures includes the use of solvents such as alcohols and tetrahydrofuran (THF) which would greatly facilitate large scale production. We also show the application of Principal Component Analysis (PCA) and clustering techniques on large libraries of XRD diffraction files in order to identify classes of similar phases and peculiar phases. The combinatorial screening of 105 samples in the La/btc system has led to the identification of two phases which are solvent depending. On the La(btc) compound, the CO? adsorption measurements reveal a guest-host interactions as supported by XRD phase transformation upon thermal treatment. The mass transport can be assigned to a "single file diffusion" regime due to the one dimensional channel porous structure associated to small pore size. 相似文献
359.
Justyna Wiedemair Jong-Seok Moon Felix Reinauer Boris Mizaikoff Christine Kranz 《Electrochemistry communications》2010,12(7):989-991
In the present study, ion beam induced deposition (IBID) of platinum carbon (PtC) composite electrodes is evaluated for combined atomic force microscopy–scanning electrochemical microscopy (AFM–SECM) probes. After deposition, the PtC composite materials are post-treated using focused ion beam (FIB) milling to decrease the carbon content of the material. It is shown that this treatment leads to an improvement of electrode characteristics for selected analytes, including the oxidation of potassium hexacyanoferrate(II) trihydrate (Fe(CN)64?) and hydrogen peroxide (H2O2). Moreover, the proposed approach is compatible with microfabricated AFM–SECM probes for increasing the AFM tip-integrated electroactive area while maintaining the geometric dimensions, which is important for imaging biosensor development. 相似文献
360.
Justyna Jarczyk 《Journal of Mathematical Analysis and Applications》2009,353(1):134-96
Let I⊂R be a non-trivial interval and let . We present some results concerning the following functional equation, generalizing the Matkowski-Sutô equation,
λ(x,y)φ−1(μ(x,y)φ(x)+(1−μ(x,y))φ(y))+(1−λ(x,y))ψ−1(ν(x,y)ψ(x)+(1−ν(x,y))ψ(y))=λ(x,y)x+(1−λ(x,y))y, 相似文献