全文获取类型
收费全文 | 19789篇 |
免费 | 2457篇 |
国内免费 | 2141篇 |
专业分类
化学 | 17945篇 |
晶体学 | 656篇 |
力学 | 795篇 |
综合类 | 138篇 |
数学 | 501篇 |
物理学 | 4352篇 |
出版年
2024年 | 36篇 |
2023年 | 213篇 |
2022年 | 385篇 |
2021年 | 611篇 |
2020年 | 843篇 |
2019年 | 679篇 |
2018年 | 646篇 |
2017年 | 687篇 |
2016年 | 914篇 |
2015年 | 924篇 |
2014年 | 978篇 |
2013年 | 1622篇 |
2012年 | 1275篇 |
2011年 | 1097篇 |
2010年 | 1048篇 |
2009年 | 987篇 |
2008年 | 1069篇 |
2007年 | 1187篇 |
2006年 | 1118篇 |
2005年 | 980篇 |
2004年 | 933篇 |
2003年 | 788篇 |
2002年 | 601篇 |
2001年 | 485篇 |
2000年 | 505篇 |
1999年 | 466篇 |
1998年 | 416篇 |
1997年 | 426篇 |
1996年 | 363篇 |
1995年 | 345篇 |
1994年 | 252篇 |
1993年 | 201篇 |
1992年 | 214篇 |
1991年 | 144篇 |
1990年 | 142篇 |
1989年 | 125篇 |
1988年 | 121篇 |
1987年 | 95篇 |
1986年 | 72篇 |
1985年 | 71篇 |
1984年 | 68篇 |
1983年 | 34篇 |
1982年 | 53篇 |
1981年 | 35篇 |
1980年 | 30篇 |
1979年 | 23篇 |
1978年 | 16篇 |
1977年 | 16篇 |
1976年 | 14篇 |
1973年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
S. Aravinda N. Shamala Rituparna S. Roy P Balaram 《Journal of Chemical Sciences》2003,115(5-6):373-400
An overview of the use of non-protein amino acids in the design of conformationally well-defined peptides, based on work from
the author’s laboratory, is discussed. The crystal structures of several designed oligopeptides illustrate the useα-aminoisobutyric acid (Aib) in the construction of helices, D-amino acids in the design of helix termination segments andDPro-Xxx segments for nucleating ofβ-hairpin structures.β- andγ-amino acid residues have been used to expand the range of designed polypeptide structures.
Dedicated to Professor C N R Rao on his 70th birthday 相似文献
52.
A fully quantum mechanical approach to the calculation and normalization of the Franck–Condon factors for diatomic species is described. The treatment is based on the fundamental demand of completeness of the energy eigenfunctions, which results in the rigorous sum rule for the Franck–Condon overlap integrals. The importance of this general rule has been discussed and thoroughly illustrated in the case of diatomic xenon molecules. Exactly solvable reference potentials for this system have been constructed and a complete basis of the actual energy eigenstates (including both bound and scattering states) has been created. Several direct spectroscopic applications to xenon excimers are presented, and their good agreement with relevant experimental data demonstrated. In particular, a kinetic model is proposed to explain the observed oscillatory structures in the fluorescence spectra of Xe2* [Chem. Phys. Lett. 117 (1985) 301] related to their classical left turning points. The same model gives a uniform explanation to the well-known first and second emission continua of rare gases. 相似文献
53.
54.
55.
Song Jiang 《Mathematische Nachrichten》1998,190(1):169-183
We consider initial boundary value problems for the equations of the one-dimensional motion of a viscous, heat-conducting gas with density-dependent viscosity that decreases (to zero) with decreasing density. We prove that if the viscosity does not decrease to zero too rapidly, then smooth solutions exist globally in time. 相似文献
56.
D. V. Kazakov A. I. Voloshin N. N. Kabal'nova V. V. Shereshovets V. P. Kazakov 《Russian Chemical Bulletin》1996,45(10):2452-2453
Chemiluminescence (CL) was found upon the isomerization of dimethyldioxirane in the gas phase under argon atmosphere. The intensity of CL increases as temperature increases and decreases with time at constant temperature. If Silipor is placed in a cell containing the dimethyldioxirane vapor in argon, the intensity of CL sharply increases (more than 10 times) and then decreases following the exponential law. In all cases tripletly excited methyl acetate is the emitter of chemiluminescence.[/ p]Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2582–2583, October 1996. 相似文献
57.
Semi-empirical molecular orbital calculations were carried out for the compounds (C2H5)3As, (C2H5)3Ga and RAsH2 (R = C2H5, i-C3H7, i-C4H9, and t-C4H9) by using the CNDO/2-U program, and their capability of β-elimination reaction is compared on the basis of the torsion energy to the transition state, electrostatic interactions and orbital overlapping between the central atom and the β-hydrogen, and bond order of the metal-carbon, and carbon-hydrogen bond. In the comparison of (C2H5)3As with (C2H5)3Ga, we found that the β-elimination of (C2H5)3As could hardly be expected to take place in the thermal decomposition. The capability of β-elimination would be smaller in C2H5AsH2 than that in (C2H5)3As. Moreover when the ethyl group is replaced by a t-butyl group in RAsH2, the β-elimination reaction appears to become more difficult and a large possibility for a radical process is suggested. 相似文献
58.
Christopher Batchelor-McAuley Craig E Banks Andrew O Simm Timothy G J Jones Richard G Compton 《Chemphyschem》2006,7(5):1081-1085
The benefits of using nanoparticle-modified electrodes are exemplified through the electrochemical detection of protons and/or hydrogen. It is shown that a palladium-nanoparticle-modified boron-doped diamond allows voltammetric information relating to the relative roles played by the surface and the bulk metal to be obtained for the proton-hydrogen system at palladium surfaces which is not accessible using palladium macroelectrodes or microelectrodes. 相似文献
59.
Alain Estve Adeline Bail Georges Landa Ahmed Dkhissi Marie Brut Mehdi Djafari Rouhani Jan Sudor Anne-Marie Gu 《Chemical physics》2007,340(1-3):12-16
Possible collapsed forms of poly(N-isopropylacrylamide) molecules are reviewed on the basis of first principle calculations. Various configurations and associated conformations are detailed. The calculated optimized structures exhibit different possibilities of creating networks of intra-molecular bonds of the hydrogen type. We show that the most remarkable one is able to form a local, self-saturated and well ordered helix. We also indicate in which direction the synthesis of the molecule should be oriented to improve its global behavior in term of hydrophobic/hydrophilic behavior. 相似文献
60.
S. V. Tyshkevich 《Mathematical Notes》2007,81(5-6):851-853