全文获取类型
收费全文 | 652391篇 |
免费 | 7152篇 |
国内免费 | 2144篇 |
专业分类
化学 | 316650篇 |
晶体学 | 9201篇 |
力学 | 32724篇 |
综合类 | 8篇 |
数学 | 108989篇 |
物理学 | 194115篇 |
出版年
2020年 | 3821篇 |
2019年 | 3955篇 |
2018年 | 20042篇 |
2017年 | 20418篇 |
2016年 | 15742篇 |
2015年 | 7099篇 |
2014年 | 8726篇 |
2013年 | 23602篇 |
2012年 | 23650篇 |
2011年 | 39087篇 |
2010年 | 24288篇 |
2009年 | 24283篇 |
2008年 | 33155篇 |
2007年 | 37530篇 |
2006年 | 19540篇 |
2005年 | 24203篇 |
2004年 | 19749篇 |
2003年 | 18216篇 |
2002年 | 15591篇 |
2001年 | 15513篇 |
2000年 | 12175篇 |
1999年 | 9540篇 |
1998年 | 7892篇 |
1997年 | 7686篇 |
1996年 | 7815篇 |
1995年 | 7048篇 |
1994年 | 6786篇 |
1993年 | 6796篇 |
1992年 | 7165篇 |
1991年 | 7072篇 |
1990年 | 6631篇 |
1989年 | 6400篇 |
1988年 | 6770篇 |
1987年 | 6338篇 |
1986年 | 6026篇 |
1985年 | 8560篇 |
1984年 | 8728篇 |
1983年 | 7229篇 |
1982年 | 7623篇 |
1981年 | 7594篇 |
1980年 | 7278篇 |
1979年 | 7541篇 |
1978年 | 7618篇 |
1977年 | 7490篇 |
1976年 | 7467篇 |
1975年 | 7116篇 |
1974年 | 7023篇 |
1973年 | 7251篇 |
1972年 | 4573篇 |
1971年 | 3608篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
A self-consistent, completely quantum calculation of the structure of the inner crust of neutron stars is carried out in the Wigner-Seitz approximation with a realistic phenomenological nuclear energy functional, where pair correlations of neutrons and protons are included in the explicit form. It has been shown that the superfluidity of neutrons and protons affects the structure of the ground state of the crust. 相似文献
992.
The deformed quantum Calogero-Moser-Sutherland problems related to the root systems of the contragredient Lie superalgebras are introduced. The construction is based on the notion of the generalized root systems suggested by V. Serganova. For the classical series a recurrent formula for the quantum integrals is found, which implies the integrability of these problems. The corresponding algebras of the quantum integrals are investigated, the explicit formulas for their Poincare series for generic values of the deformation parameter are presented. 相似文献
993.
The kinetics of formation and relaxation of transient holographic gratings recorded in a system of saturable three-level centers is studied. Distortions in the shape of the profile of recorded and decaying structures of population and of the refractive index are taken into account. The analysis of the time dependences of diffraction efficiencies of different orders is performed for phase (thermal) and amplitude (concentration) gratings. 相似文献
994.
Gowravaram Sabitha G.S.Kiran Kumar ReddyK.Bhaskar Reddy J.S. Yadav 《Tetrahedron letters》2003,44(34):6497-6499
The three component condensation of an aldehyde, a β-keto ester and urea (thiourea) in the presence of a catalytic amount of VCl3 is disclosed for the solution phase synthesis of dihydropyrimidinones. The ease of synthesis and work-up allowed the parallel synthesis of a 48-membered library of dihydropyrimidinones quickly and efficiently in good yields. 相似文献
995.
We examine several interesting relationships and expressions involving Fourier-Feynman transform, convolution product and
first variation for functionals in the Fresnel class F(B) of an abstract Wiener space B. We also prove a translation theorem and Parseval's identity for the analytic Feynman integral.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
996.
997.
In this work, we elucidate the effect of the less mobile ions on the dynamics of the more mobile ions by molecular dynamics simulations of lithium ions motion in lithium metasilicate glass by freezing some randomly chosen lithium ions (5%, 10% and 25%) at their initial locations at 700 K. A remarkable slowing down of the dynamics of the majority mobile Li ions was observed both in the self-part of the density–density correlation function, Fs(k,t), and in the diffusion coefficients. On the other hand, there is no significant change in the structure. These results show many similarities to the mixed alkali effect (MAE) with mixing of the small content of foreign alkali (10% and 25% of K2O), where large reduction of the dynamics was also observed in both experiments and MD simulations. This immobilization of faster ions causes the large MAE as already discussed in relation to the mechanism of the cooperative ion jump motions. Although of lesser importance, the ion dynamics are influenced by the matrix of oxygen atoms, because the jump motions of Li ions are assisted by the localized motions of oxygen atoms. 相似文献
998.
999.
B. Ya. Balagurov 《Technical Physics》2003,48(8):945-951
A sequential scheme for calculating the polarizability of a pair of parallel cylinders with an arbitrary (but fairly symmetric) form is suggested. An infinite set of algebraic equations is derived for coefficients involved in an expression for the potential. The numerical solution of this set makes it possible to find the polarizability with any degree of accuracy. This method is unrelated to the cylinder shape. The electrostatic properties of the cylinders are described in terms of the multipolar polarizability matrix. 相似文献
1000.
K. K. Turgunov B. Tashkhodzhaev L. V. Molchanov Kh. M. Shakhidoyatov 《Journal of Structural Chemistry》2004,45(5):912-916
The structure of bis-(2,3-pentamethylene-3,4-dihydro-4-oxoquinazolinium) tetrachlorocuprate (II) sesquihydrate, (C13H15N2O)2[CuCl4]·1.5H2O, was determined by single crystal X-ray diffraction. In contrast to the previously studied analogs, the compound contains crystallization water molecules.Original Russian Text Copyright © 2004 by K. K. Turgunov, B. Tashkhodzhaev, L. V. Molchanov, and Kh. M. Shakhidoyatov__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 5, pp. 955–959, September–October, 2004. 相似文献