全文获取类型
收费全文 | 329919篇 |
免费 | 3044篇 |
国内免费 | 933篇 |
专业分类
化学 | 164774篇 |
晶体学 | 5374篇 |
力学 | 15531篇 |
综合类 | 7篇 |
数学 | 38464篇 |
物理学 | 109746篇 |
出版年
2021年 | 3132篇 |
2020年 | 3330篇 |
2019年 | 3760篇 |
2018年 | 5198篇 |
2017年 | 5439篇 |
2016年 | 7368篇 |
2015年 | 4139篇 |
2014年 | 7028篇 |
2013年 | 15904篇 |
2012年 | 12375篇 |
2011年 | 14824篇 |
2010年 | 11012篇 |
2009年 | 10913篇 |
2008年 | 13236篇 |
2007年 | 13192篇 |
2006年 | 12137篇 |
2005年 | 10520篇 |
2004年 | 9832篇 |
2003年 | 8686篇 |
2002年 | 8672篇 |
2001年 | 10393篇 |
2000年 | 7655篇 |
1999年 | 5967篇 |
1998年 | 4973篇 |
1997年 | 4811篇 |
1996年 | 4479篇 |
1995年 | 3864篇 |
1994年 | 3820篇 |
1993年 | 3701篇 |
1992年 | 4096篇 |
1991年 | 4306篇 |
1990年 | 4096篇 |
1989年 | 4008篇 |
1988年 | 3779篇 |
1987年 | 3917篇 |
1986年 | 3683篇 |
1985年 | 4629篇 |
1984年 | 4681篇 |
1983年 | 3885篇 |
1982年 | 3973篇 |
1981年 | 3697篇 |
1980年 | 3647篇 |
1979年 | 3913篇 |
1978年 | 3901篇 |
1977年 | 3906篇 |
1976年 | 3879篇 |
1975年 | 3675篇 |
1974年 | 3615篇 |
1973年 | 3650篇 |
1972年 | 2603篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
111.
A new grid‐free upwind relaxation scheme for simulating inviscid compressible flows is presented in this paper. The non‐linear conservation equations are converted to linear convection equations with non‐linear source terms by using a relaxation system and its interpretation as a discrete Boltzmann equation. A splitting method is used to separate the convection and relaxation parts. Least squares upwinding is used for discretizing the convection equations, thus developing a grid‐free scheme which can operate on any arbitrary distribution of points. The scheme is grid free in the sense that it works on any arbitrary distribution of points and it does not require any topological information like elements, faces, edges, etc. This method is tested on some standard test cases. To explore the power of the grid‐free scheme, solution‐based adaptation of points is done and the results are presented, which demonstrate the efficiency of the new grid‐free scheme. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
112.
113.
114.
A. P. S. Selvadurai 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1987,38(5):674-688
The paper examines the problem related to the axisymmetric interaction between an external circular crack and a centrally placed penny-shaped rigid inclusion located in the plane of the crack. The interface between the inclusion and the elastic medium exhibits a Mindlin-type imperfect bi-lateral contact. Analytical results presented in the paper illustrate the manner in which the lateral translational stiffness of the inclusion and the stress intensity factor at the boundary of the external circular crack are influenced by the inclusion/crack radii ratio. 相似文献
115.
S. M. Dunaevskii A. L. Malyshev V. A. Trunov V. V. Popov 《Physics of the Solid State》1997,39(10):1636-1637
The results of investigating the temperature dependence of the resistivity, the differential magnetic susceptibility, and
the magnetoresistance of a partially substituted perovskite Sm1−x
SrxMnO3 (x=0.16–0.4) are presented. Colossal intrinsic magnetoresistance, reaching 90% in an external magnetic field of 30 kOe, is discovered
in the compound with x=0.30 at 77 K.
Fiz. Tverd. Tela (St. Petersburg) 39, 1831–1832 (October 1997) 相似文献
116.
S. Gukov 《JETP Letters》1997,65(8):694-700
The manifestly supersymmetric four-dimensional Wess-Zumino model with quenched disorder is considered at the one-loop level.
The infrared fixed points of a beta function form the moduli space ℳ=RP
2, where two types of phases are found: with and without replica symmetry. While the former phase possesses only a trivial
fixed point, this point become unstable in the latter phase, which may be interpreted as a spin glass phase.
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 8, 657–662 (25 April 1997)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
117.
It is shown that the potential perturbation that shifts a chosen standing wave in space is a block of potential barrier and well for every wave bump between neighbouring knots. The algorithms shifting the range of the primary localization of a chosen bound state in a potential well of finite width are as well applicable to the scattering functions if states of the continuous spectrum are considered as bound states normalized to unity but distributed on an infinite interval with vanishing density. The potential perturbations of the same type on the half-axis concentrate the scattering wave at the origin, thus creating a bound state embedded into the continuous spectrum (zero width resonance). 相似文献
118.
119.
N. P. Venediktov M. Yu. Glyavin V. E. Zapevalov A. N. Kuftin A. S. Postnikova M. V. Yulpatova 《Radiophysics and Quantum Electronics》1997,40(4):336-342
A scheme for automated study of current-voltage characteristics of gyroresonance devices is developed. The effective emission
spread at the cathodes of powerful gyrotrons is studied by analysis of current-voltage characteristics. Experimental data
on the effective emission spread parameter for different modes are given. The permissible emission spread at the cathodes
of powerful gyrotrons is estimated, and the dependence of the electron beam parameters on the cathode emission spread is presented.
A complex measurement technique showing the contribution of different physical mechanisms to the cathode emission spread is
proposed.
Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh
Zavedenii, Radiofizika, Vol. 40, No. 4, pp. 506–516, April, 1997. 相似文献
120.
Processing-induced residual strains in solid cylinders of Nickel 200 were investigated using phase shifting moiré interferometry. Two different experimental approaches were used to study the strains produced during Tungsten-inert gas spot welding. A comparison of results for a ‘hot/fast’ and a ‘cool/slow’ weld demonstrate the capabilities of the general approach. Both experimental methods revealed distinct differences in the residual displacement and strain fields between the two types of welds. 相似文献