全文获取类型
收费全文 | 554307篇 |
免费 | 5073篇 |
国内免费 | 1731篇 |
专业分类
化学 | 272727篇 |
晶体学 | 8575篇 |
力学 | 28020篇 |
综合类 | 16篇 |
数学 | 84906篇 |
物理学 | 166867篇 |
出版年
2021年 | 4229篇 |
2020年 | 4670篇 |
2019年 | 5266篇 |
2018年 | 16452篇 |
2017年 | 16485篇 |
2016年 | 15595篇 |
2015年 | 6615篇 |
2014年 | 9952篇 |
2013年 | 23098篇 |
2012年 | 20640篇 |
2011年 | 30251篇 |
2010年 | 20208篇 |
2009年 | 20573篇 |
2008年 | 24467篇 |
2007年 | 26304篇 |
2006年 | 17211篇 |
2005年 | 16140篇 |
2004年 | 15248篇 |
2003年 | 14139篇 |
2002年 | 13106篇 |
2001年 | 14670篇 |
2000年 | 11161篇 |
1999年 | 8545篇 |
1998年 | 7112篇 |
1997年 | 6890篇 |
1996年 | 6623篇 |
1995年 | 5871篇 |
1994年 | 5680篇 |
1993年 | 5431篇 |
1992年 | 6306篇 |
1991年 | 6406篇 |
1990年 | 6139篇 |
1989年 | 6135篇 |
1988年 | 5896篇 |
1987年 | 6008篇 |
1986年 | 5656篇 |
1985年 | 7218篇 |
1984年 | 7271篇 |
1983年 | 5928篇 |
1982年 | 6135篇 |
1981年 | 5949篇 |
1980年 | 5658篇 |
1979年 | 6185篇 |
1978年 | 6230篇 |
1977年 | 6303篇 |
1976年 | 6130篇 |
1975年 | 5714篇 |
1974年 | 5584篇 |
1973年 | 5627篇 |
1972年 | 3972篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
The paper discusses the applicability of quasi-crystalline approximation to describing the thermal motion of water molecules in their normal and supercooled states. The problem is subjected to the critical analysis of experimental data on incoherent scattering of slow neutrons based on theories developed by Singwi-Sjolander [1] and Oskotsky [2] modified to duly take into account the limited applicability range of diffusion approximation. The applicability conditions of quasi-crystalline approximation are shown to be consistently satisfied only when water is in supercooled state and within a narrow temperature range above the melting temperature. 相似文献
12.
A. Foussats C. Repetto O. P. Zandron O. S. Zandron 《International Journal of Theoretical Physics》2002,41(6):1053-1082
In order to describe the dynamics of the t–J model, two different families of first-order Lagrangians in terms of the generators of the Hubbard algebra are found. Such families correspond to different dynamical second-class constrained systems. The quantization is carried out by using the path-integral formalism. In this context the introduction of proper ghost fields is needed to render the model renormalizable. In each case the standard Feynman diagrammatics is obtained and the renormalized physical quantities are computed and analyzed. In the first case a nonperturbative large-N expansion is considered with the purpose of studying the generalized Hubbard model describing N-fold-degenerate correlated bands. In this case the 1/N correction to the renormalized boson propagator is computed. In the second case the perturbative Lagrangian formalism is developed and it is shown how propagators and vertices can be renormalized to each order. In particular, the renormalized ferromagnetic magnon propagator coming from our formalism is studied in details. As an example the thermal softening of the magnon frequency is computed. The antiferromagnetic case is also analyzed, and the results are confronted with previous one obtained by means of the spin-polaron theories. 相似文献
13.
Experimental data on the effect of thallium and sodium impurities on the lattice heat conductivity of PbTe at room temperature
are reported. Because the lattice of lead chalcogenides is strongly polarized near charged impurities, the effect of impurities
on the lattice heat conductivity depends substantially on their charge state. This property of the material has been used
to determine the charge state of the thallium impurity in PbTe. The results obtained argue for a model of quasi-local thallium-impurity
states which assumes low electron-correlation energy at an impurity center.
Fiz. Tverd. Tela (St. Petersburg) 40, 1206–1208 (July 1998) 相似文献
14.
15.
E. Jackiewicz M. Lukasiak M. Kopcewicz K. Szpila N. Bakun-Czubarow 《Hyperfine Interactions》1992,70(1-4):993-996
Terrestrial basalt rocks considered to be a good analogues of the Martian regolith were studied by using the Mössbauer spectroscopy and X-ray diffraction. The weathering of basalts was followed by the changes of the Fe2+/Fe3+ ratio. The basalt rock undergoes alteration from primary mineral composition (olivine+pyroxene+plagioclase) through smectite to kaolinite clay with oxides and hydroxides with the increase of the Fe2+/Fe3+ ratio. 相似文献
16.
17.
18.
Myagchenkov V. A. Chichkanov S. V. Proskurina V. E. Myagchenkov A. V. 《Russian Journal of Applied Chemistry》2002,75(9):1485-1488
The Thoms effect observed with water-soluble cationic copolymer of acrylamide was studied in relation to the concentration, molecular weight, and molecular weight polydispersity of the polymeric additive, with its composition and composition polydispersity being constant. 相似文献
19.
20.
A. K. Lopatin 《Ukrainian Mathematical Journal》1997,49(1):51-74
We consider the method of normal forms, the Bogolyubov averaging method, and the method of asymptotic decomposition proposed by Yu. A. Mitropol’skii and the author of this paper. Under certain assumptions about group-theoretic properties of a system of zero approximation, the results obtained by the method of asymptotic decomposition coincide with the results obtained by the method of normal forms or the Bogolyubov averaging method. We develop a new algorithm of asymptotic decomposition by a part of the variables and its partial case — the algorithm of averaging on a compact Lie group. For the first time, it became possible to consider asymptotic expansions of solutions of differential equations on noncommutative compact groups. 相似文献