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21.
A general approach to the diastereoselective synthesis of Delta(2)-isoxazolines via magnesium-mediated, hydroxyl-directed diastereoselective nitrile oxide cycloadditions of homoallylic alcohols and monoprotected homoallylic diols is disclosed. A broad spectrum of aliphatic and aromatic nitrile oxides and a variety of homoallylic alcohols participate in the cycloaddition, thus expanding the scope of polyketide building blocks that can be accessed using this strategy. 相似文献
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Solid-phase synthesis of photochromic spiropyrans 总被引:2,自引:0,他引:2
[reaction: see text] A convenient solid-phase synthesis of spiropyrans is described. A succinate linker was employed, which allows base-catalyzed cleavage of the desired photochromophore derivatized with a succinimide. Excellent yields and purities were obtained for the compounds that comprise a library of 23 spiropyrans. Opening of the succinimide ring in spiropyran could be realized under mild conditions. 相似文献
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Recently, a new approach in the fine analysis of sample paths of stochastic processes has been developed to predict the evolution of the local regularity under (pseudo-)differential operators. In this paper, we study the sample paths of continuous martingales and stochastic integrals. We proved that the almost sure 2-microlocal frontier of a martingale can be obtained through the local regularity of its quadratic variation. It allows to link the Hölder regularity of a stochastic integral to the regularity of the integrand and integrator processes. These results provide a methodology to predict the local regularity of diffusions from the fine analysis of its coefficients. We illustrate our work with examples of martingales with unusual complex regularity behaviour and square of Bessel processes. 相似文献
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Dieter Muri Clémence Corminboeuf Erick M. Carreira Damien Jeannerat 《Magnetic resonance in chemistry : MRC》2009,47(11):909-916
We discuss and demonstrate the potential of HSQC‐TOCSY and HSQC‐NOESY experiments to offer solutions for overlap problems in COSY and NOESY spectra, leading to improved signals that can be unambiguously assigned to individual carbons. Direct comparison of experimental 1H and 13C chemical shielding with density functional theory (DFT)‐calculated values are uninformative; in contrast, the relative differences in experimental shielding between pairs of molecules correlates well with the relative differences in DFT‐GIAO shielding for the computed lowest energy conformers. A detailed application of both experimental and theoretical techniques is illustrated for slowly exchanging conformers of an erythronolide A derivative, which demonstrates that structure determination can strongly benefit from the interplay between experiment and theory. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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José Gustavo Ávila-Zárraga Ignacio Pérez Erick Beristain Irma Gavilan Moises Romero 《合成通讯》2017,47(4):364-367
Several new 6-(alkylamine)-6H-dibenz[c,e][1,2]oxaphosphinine-6-oxides were prepared through a one-pot reaction, starting with 2-phenylphenol, phosphorus trichloride, and a Zn catalyst, to form 6-chloro-6H-dibenz[c,e][1,2]oxaphosphine. The alkylamine derivatives were subsequently prepared through a nucleophilic substitution reaction involving aliphatic amines and H2O2 oxidation under soft conditions. This method has the advantages that it is a one-pot synthesis, does not require an inert atmosphere, and involves in situ catalyst formation. 相似文献