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991.
Lepri Luciano Del Bubba Massimo Cincinelli Alessandra Boddi Laura 《平面色谱法杂志一现代薄层色谱法》2001,14(2):134-136
JPC – Journal of Planar Chromatography – Modern TLC - 相似文献
992.
Sandro Cacchi Cosmin L. Cotet Giovanni Forte Laura Martín Elies Molins Francesco Petrucci Adelina Vallribera 《Tetrahedron》2007,63(11):2519-2523
Electron-rich and electron-poor aryl iodides are converted, in high to excellent yields, into the corresponding carboxylic acids through a hydroxycarboxylation reaction catalyzed by a recoverable and reusable phosphine free palladium-carbon aerogel catalyst using lithium formate and acetic anhydride as an internal condensed source of carbon monoxide. The catalyst system can be reused several times without any appreciable loss of activity. 相似文献
993.
Adriana Isvoran Laura Pitulice Constantin T. Craescu Adrian Chiriac 《Chaos, solitons, and fractals》2008,35(5):960-966
The structures of EF-hand calcium binding proteins may be classified into two distinct groups: extended and compact structures. In this paper we studied 20 different structures of calcium binding proteins using the fractal analysis. Nine structures show extended shapes, one is semi-compact and the other 10 have compact shapes. Our study reveals different fractal characteristics for protein backbones belonging to different structural classes and these observations may be correlated to the physicochemical forces governing the protein folding. 相似文献
994.
Giovanni La Macchia Laura Gagliardi Geoffrey S. Carlson Ashley N. Jay Erik Davis Christopher J. Cramer 《Journal of Physical Organic Chemistry》2008,21(2):136-145
Values of σ and σ+, for use in linear free energy relationships, are determined for para hydrogen atoms having nuclear charges other than 1 (nucleomers). Hammett ρ values for a variety of free energies of activation, reaction, and other extrathermodynamic properties (e.g., vibrational frequencies) are computed therefrom and compared to those computed using typical para functional groups. The nucleomer correlations show excellent qualitative agreement with standard correlations but the quantitative agreement is less good, typically underestimating the standard ρ‐value by 10–60%. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
995.
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997.
Natalia Domracheva Anisoara Mirea Markus Schwoerer Laura Torre-Lorente Günter Lattermann 《Chemphyschem》2006,7(12):2567-2577
Copper(II) complexes formed by coordination of the Cu(II) ion with liquid-crystalline poly(propylene imine) dendrimer ligand (L) of the first (complex 1) and second (complex 2) generations with various Cu(II) contents (x = Cu/L) have been studied by electron paramagnetic resonance (EPR) spectroscopy. The existence of a redox-active blue complex 1 (x = 1.9) and the copper(II) nitrate electron transfer associated with the valence tautomerism are revealed for the first time in copper-based dendrimers. It has been shown that the electronic structure of the blue complex 1 (x = 1.9) is adequately described as a mixed-valence dimer containing d9- and diamagnetic d10-configurated copper ions, and an antiferromagnetically coupled NO3* radical arising on the nitrate-bridged counter ligand. The activation energy value found for the electron transfer is about 0.35 meV, which indicates a low-energy charge dynamic. The ability of the blue and green complexes 1 (x = 1.9) dissolved in isotropic solvents to orient themselves in the magnetic field was revealed by EPR spectroscopy. The degree of orientation of the molecular z axis (S(z)) of these complexes in the magnetic field differs, depending on the type of copper(II)-complexing site in the dendrimer ligand, and can reach 0.76, which is close to S(z) = 1 (completely aligned system). A combination of magnetic and orientational parameters indicates an NO4 environment of the Cu(II) ion in green complex 1 (x = 1.9), and confirms the chain structure with intermolecular Cu(II)-NO3-Cu(II) bridges between Cu(II) centres in columns. 相似文献
998.
Kelly A. Daniel Laura A. Kopff Eric V. Patterson 《Journal of Physical Organic Chemistry》2008,21(4):321-328
The reaction of the chemical warfare agent VX with hydroxide and hydroperoxide has been studied using a combination of correlated molecular orbital and density functional theory. It is found that the alkaline hydrolysis leads to a mixture of neurotoxic and non‐toxic products while hydroperoxidolysis leads to exclusive formation of non‐toxic products. Natural bond orbital (NBO) analysis is used to rationalize the observation that hydroxide will attack opposite the alkoxide ligand, while hydroperoxide will attack opposite the thiolate. The current results are in good agreement with previous experimental and computational work and serve to clarify the mechanism for destruction of this highly potent nerve agent. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
999.
Flavio Pressacco Marcellino Gaudenzi Antonino Zanette Laura Ziani 《European Journal of Operational Research》2008
With reference to the evaluation of the speed–precision efficiency of pricing and hedging of American Put options, we present and discuss numerical results obtained on the basis of four different large enough random samples according to the relevance of the American quality (relative importance of the early exercise opportunity) of the options. Here we provide a comparison of the best methods (lattice based numerical methods and an approximation of the American Premium analytical procedure) known in literature along with some key methodological remarks. 相似文献
1000.
Dr. Yonglong Xiao Prof. Joel T. Mague Prof. James P. Donahue Dr. Laura J. Wilson Dr. Christina M. Kraml Prof. Robert A. Pascal Jr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(38):8458-8464
1,2,3,4,5,6,7,8-Octaphenylphenanthrene ( 4 ) and decaphenylphenanthrene ( 5 ) were prepared by very short syntheses (two or three steps) from tetraphenylfuran and polybrominated benzene derivatives. The X-ray structures of compounds 4 and 5 show them to be quite crowded, with the phenanthrene cores twisted by about 40° due to the clash of the C4 and C5 phenyl groups. Compound 4 was resolved by chromatography on a chiral support, and its free energy of activation for racemization was determined to be 24.6 kcal mol−1 at 40 °C. Computational studies indicate that compound 5 has a racemization barrier approximately 6 kcal mol−1 lower than 4 , and thus 5 would not be configurationally stable at room temperature. 相似文献