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971.
Sina Schwendemann Shunsuke Oishi Prof. Dr. Susumu Saito Dr. Roland Fröhlich Dr. Gerald Kehr Prof. Dr. Gerhard Erker 《化学:亚洲杂志》2013,8(1):212-217
D ‐(+)‐Camphor forms the enamine 2 with piperidine. Compound 2 adds HB(C6F5)2 at the enamine carbon atom C3 to form a Lewis acid/Lewis base adduct (exo‐/endo‐isomers of 3 ). Exposure of 3 to dihydrogen (2.5 bar, room temperature) leads to heterolytic splitting of H2 to form the H+/H? addition products ( 4 , two diastereoisomers) of the “invisible” frustrated Lewis pairs ( 5 , two diastereoisomers) that were apparently generated in situ by enamine hydroboration under equilibrium conditions. 相似文献
972.
Steven M. Schultz Gerald Kehr Roland Fröhlich Gerhard Erker Nadia Kapernaum Constanze Hägele 《Liquid crystals》2013,40(8):919-926
A series of 2‐(4‐n‐alkylphenyl)indenes (3) with different alkyl substituents (CH3 to C10H21) were synthesized and systematically characterized using differential scanning calorimetry, polarizing optical microscopy and X‐ray diffraction compared with 2‐phenylindene (3a). Depending on the alkyl chain length, highly ordered crystal‐smectic E mesophases were observed and confirmed by X‐ray diffraction for the derivatives 3h–3k with heptyl to decyl chains (n = 6?9). For 3f with a pentyl side chain (n = 4), an X‐ray crystal structure analysis was carried out. 相似文献
973.
974.
Francesco Aquilante Luca De Vico Nicolas Ferr Giovanni Ghigo Per‐ke Malmqvist Pavel Neogrdy Thomas Bondo Pedersen Michal Pitok Markus Reiher Bjrn O. Roos Luis Serrano‐Andrs Miroslav Urban Valera Veryazov Roland Lindh 《Journal of computational chemistry》2010,31(1):224-247
Some of the new unique features of the MOLCAS quantum chemistry package version 7 are presented in this report. In particular, the Cholesky decomposition method applied to some quantum chemical methods is described. This approach is used both in the context of a straight forward approximation of the two‐electron integrals and in the generation of so‐called auxiliary basis sets. The article describes how the method is implemented for most known wave functions models: self‐consistent field, density functional theory, 2nd order perturbation theory, complete‐active space self‐consistent field multiconfigurational reference 2nd order perturbation theory, and coupled‐cluster methods. The report further elaborates on the implementation of a restricted‐active space self‐consistent field reference function in conjunction with 2nd order perturbation theory. The average atomic natural orbital basis for relativistic calculations, covering the whole periodic table, are described and associated unique properties are demonstrated. Furthermore, the use of the arbitrary order Douglas‐Kroll‐Hess transformation for one‐component relativistic calculations and its implementation are discussed. This section especially focuses on the implementation of the so‐called picture‐change‐free atomic orbital property integrals. Moreover, the ElectroStatic Potential Fitted scheme, a version of a quantum mechanics/molecular mechanics hybrid method implemented in MOLCAS, is described and discussed. Finally, the report discusses the use of the MOLCAS package for advanced studies of photo chemical phenomena and the usefulness of the algorithms for constrained geometry optimization in MOLCAS in association with such studies. © 2009 Wiley Periodicals, Inc. J Comput Chem 2010 相似文献
975.
976.
Spectroscopic Observation of Calcium‐Induced Reorientation of Cellobiose Dehydrogenase Immobilized on Electrodes and its Effect on Electrocatalytic Activity 下载免费PDF全文
Patrycja Kielb Dr. Murat Sezer Sagie Katz Francesca Lopez Christopher Schulz Prof. Lo Gorton Dr. Roland Ludwig Prof. Ulla Wollenberger Dr. Ingo Zebger Prof. Inez M. Weidinger 《Chemphyschem》2015,16(9):1960-1968
Cellobiose dehydrogenase catalyzes the oxidation of various carbohydrates and is considered as a possible anode catalyst in biofuel cells. It has been shown that the catalytic performance of this enzyme immobilized on electrodes can be increased by presence of calcium ions. To get insight into the Ca2+‐induced changes in the immobilized enzyme we employ surface‐enhanced vibrational (SERR and SEIRA) spectroscopy together with electrochemistry. Upon addition of Ca2+ ions electrochemical measurements show a shift of the catalytic turnover signal to more negative potentials while SERR measurements reveal an offset between the potential of heme reduction and catalytic current. Comparing SERR and SEIRA data we propose that binding of Ca2+ to the heme induces protein reorientation in a way that the electron transfer pathway of the catalytic FAD center to the electrode can bypass the heme cofactor, resulting in catalytic activity at more negative potentials. 相似文献
977.
978.
The recently discovered scaling law for the relaxation times, tau(T,upsilon) = I(Tupsilon(gamma)), where T is temperature and upsilon the specific volume, is derived by a revision of the entropy model of the glass transition dynamics originally proposed by Avramov [J. Non-Cryst. Solids 262, 258 (2000)]. In this modification the entropy is calculated by an alternative route. The resulting expression for the variation of the relaxation time with T and upsilon is shown to accurately fit experimental data for several glass-forming liquids and polymers over an extended range encompassing the dynamic crossover. From this analysis, which is valid for any model in which the relaxation time is a function of the entropy, we find that the scaling exponent gamma can be identified with the Gruneisen constant. 相似文献
979.
Mitra L Smolin N Ravindra R Royer C Winter R 《Physical chemistry chemical physics : PCCP》2006,8(11):1249-1265
We used pressure perturbation calorimetry (PPC), a relatively new and efficient technique, to study the solvation and volumetric properties of amino acids and peptides as well as of proteins in their native and unfolded state. In PPC, the coefficient of thermal expansion of the partial volume of the protein is deduced from the heat consumed or produced after small isothermal pressure jumps, which strongly depends on the interaction of the protein with the solvent or cosolvent at the protein-solvent interface. Furthermore, the effects of various chaotropic and kosmotropic cosolvents on the volume and expansivity changes of proteins were measured over a wide concentration range with high precision. Depending on the type of cosolvent and its concentration, specific differences were found for the solvation properties and unfolding behaviour of the proteins, and the volume change upon unfolding may even change sign. To yield a molecular interpretation of the different terms contributing to the partial protein volume and its temperature dependence, and hence a better understanding of the PPC data, molecular dynamics computer simulations on SNase were also carried out and compared with the experimental data. The PPC studies introduced aim to obtain more insight into the basic thermodynamic properties of protein solvation and volume effects accompanying structural transformations of proteins in various cosolvents on one hand, as these form the basis for understanding their physiological functions and their use in drug designing and formulations, but also to initiate further valuable applications in studies of other biomolecular and chemical systems. 相似文献
980.
Dr. Weijin Li Song Xue Sebastian Watzele Shujin Hou Johannes Fichtner A. Lisa Semrau Prof. Liujiang Zhou Dr. Alexander Welle Prof. Aliaksandr S. Bandarenka Prof. Roland A. Fischer 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(14):5886-5892
Metal–organic frameworks (MOFs) and their derivatives are considered as promising catalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), which are important for many energy provision technologies, such as electrolyzers, fuel cells and some types of advanced batteries. In this work, a “strain modulation” approach has been applied through the use of surface-mounted NiFe-MOFs in order to design an advanced bifunctional ORR/OER electrocatalyst. The material exhibits an excellent OER activity in alkaline media, reaching an industrially relevant current density of 200 mA cm−2 at an overpotential of only ≈210 mV. It demonstrates operational long-term stability even at a high current density of 500 mA cm−2 and exhibits the so far narrowest “overpotential window” ΔEORR-OER of 0.69 V in 0.1 m KOH with a mass loading being two orders of magnitude lower than that of benchmark electrocatalysts. 相似文献