全文获取类型
收费全文 | 375969篇 |
免费 | 4125篇 |
国内免费 | 1519篇 |
专业分类
化学 | 203014篇 |
晶体学 | 5586篇 |
力学 | 16136篇 |
综合类 | 8篇 |
数学 | 42707篇 |
物理学 | 114162篇 |
出版年
2020年 | 2697篇 |
2019年 | 2995篇 |
2018年 | 3400篇 |
2017年 | 3343篇 |
2016年 | 5713篇 |
2015年 | 4162篇 |
2014年 | 5889篇 |
2013年 | 17412篇 |
2012年 | 13091篇 |
2011年 | 16305篇 |
2010年 | 10464篇 |
2009年 | 10555篇 |
2008年 | 14768篇 |
2007年 | 14855篇 |
2006年 | 13877篇 |
2005年 | 12920篇 |
2004年 | 11563篇 |
2003年 | 10191篇 |
2002年 | 10021篇 |
2001年 | 11608篇 |
2000年 | 8826篇 |
1999年 | 6870篇 |
1998年 | 5608篇 |
1997年 | 5556篇 |
1996年 | 5299篇 |
1995年 | 4907篇 |
1994年 | 4628篇 |
1993年 | 4599篇 |
1992年 | 5061篇 |
1991年 | 5081篇 |
1990年 | 4675篇 |
1989年 | 4647篇 |
1988年 | 4687篇 |
1987年 | 4532篇 |
1986年 | 4302篇 |
1985年 | 6146篇 |
1984年 | 6241篇 |
1983年 | 5116篇 |
1982年 | 5561篇 |
1981年 | 5354篇 |
1980年 | 5183篇 |
1979年 | 5221篇 |
1978年 | 5464篇 |
1977年 | 5269篇 |
1976年 | 5417篇 |
1975年 | 4996篇 |
1974年 | 5045篇 |
1973年 | 5347篇 |
1972年 | 3255篇 |
1971年 | 2424篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
Summary The main purpose of this paper is to introduce the concepts of η-sets, ηζ-sets,η-continuity and ηζ-continuity and to obtain
a decomposition of continuity. 相似文献
43.
44.
45.
J. C. Fabris S. V. B. Gonçalves P. E. de Souza 《General Relativity and Gravitation》2002,34(12):2111-2126
The mass power spectrum for a Universe dominated by the Chaplygin gas is evaluated numerically from scales of the order of the Hubble horizon to 100 Mpc. The results are compared with a pure baryonic Universe and a cosmological constant model. In all three cases, the spectrum increases with k, the wavenumber of the perturbations. The slope of the spectrum is higher for the baryonic model and smaller for the cosmological constant model, the Chaplygin gas interpolating these two models. The results are analyzed in terms of the sound velocity of the Chaplygin gas and the moment the Universe begins to accelerate. 相似文献
46.
Allen C. HirshfeldPeter Henselder 《Annals of Physics》2002,302(1):59-77
Deformation quantization, which achieves the passage from classical mechanics to quantum mechanics by the replacement of the pointwise multiplication of functions on phase space by the star product, is a powerful tool for treating systems involving bosonic degrees of freedom, both in quantum mechanics and in quantum field theory. In the present paper we show how these methods may be naturally extended to systems involving fermions. In particular we show how supersymmetric quantum mechanics can be formulated in this approach and consider examples involving both non-relativistic and relativistic systems. 相似文献
47.
The Wheeler–DeWitt equation of arbitrary Hartle–Hawking factor ordering for several minisuperspace universe models, such as the pure gravity Friedmann–Robertson–Walker and Taub ones, is mapped onto the dynamics of corresponding classical oscillators. The latter ones are studied by the classical Ermakov invariant method, which is a natural approach in this context. For the more realistic case of a minimally coupled massive scalar field, one can study, within the same type of approach, the corresponding squeezing features as a possible means of describing cosmological evolution. Finally, we comment on the analogy with the accelerator physics. 相似文献
48.
49.
R. J. Vanderbei 《Mathematical Programming》1989,43(1-3):31-44
The affine-scaling modification of Karmarkar's algorithm is extended to solve problems with free variables. This extended primal algorithm is used to prove two important results. First the geometrically elegant feasibility algorithm proposed by Chandru and Kochar is the same algorithm as the one obtained by appending a single column of residuals to the constraint matrix. Second the dual algorithm as first described by Adler et al., is the same as the extended primal algorithm applied to the dual. 相似文献
50.
A new geometrical method to determine the surface damage threshold for ultrashort pulses is presented. It consists in the formation of a surface damage profile by a movement of the sample across the laser beam focus. A single measurement of the maximum transversal dimension of this damage profile, which depends solely on the laser beam power, is used to calculate the local damage threshold intensity. It is also theoretically shown that the damage in the transverse dimension can be controlled under the diffraction-limited spot. 相似文献