全文获取类型
收费全文 | 19577篇 |
免费 | 2251篇 |
国内免费 | 929篇 |
专业分类
化学 | 10072篇 |
晶体学 | 30篇 |
力学 | 887篇 |
综合类 | 91篇 |
数学 | 6641篇 |
物理学 | 5036篇 |
出版年
2024年 | 37篇 |
2023年 | 282篇 |
2022年 | 688篇 |
2021年 | 786篇 |
2020年 | 800篇 |
2019年 | 647篇 |
2018年 | 488篇 |
2017年 | 570篇 |
2016年 | 909篇 |
2015年 | 747篇 |
2014年 | 1025篇 |
2013年 | 1533篇 |
2012年 | 956篇 |
2011年 | 987篇 |
2010年 | 846篇 |
2009年 | 1116篇 |
2008年 | 1240篇 |
2007年 | 1237篇 |
2006年 | 1010篇 |
2005年 | 743篇 |
2004年 | 647篇 |
2003年 | 673篇 |
2002年 | 633篇 |
2001年 | 490篇 |
2000年 | 505篇 |
1999年 | 442篇 |
1998年 | 411篇 |
1997年 | 286篇 |
1996年 | 233篇 |
1995年 | 199篇 |
1994年 | 195篇 |
1993年 | 162篇 |
1992年 | 154篇 |
1991年 | 100篇 |
1990年 | 92篇 |
1989年 | 96篇 |
1988年 | 109篇 |
1987年 | 72篇 |
1986年 | 69篇 |
1985年 | 105篇 |
1984年 | 82篇 |
1983年 | 25篇 |
1982年 | 53篇 |
1981年 | 53篇 |
1980年 | 50篇 |
1979年 | 41篇 |
1978年 | 33篇 |
1977年 | 34篇 |
1976年 | 30篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
161.
We analyze the statistical behavior of signals in nonlinear circuits with delayed feedback in the presence of external Markovian noise. For the special class of circuits with intense phase mixing we develop an approach for the computation of the probability distributions and multitime correlation functions based on the random phase approximation. Both Gaussian and Kubo-Andersen models of external noise statistics are analyzed and the existence of the stationary (asymptotic) random process in the long-time limit is shown. We demonstrate that a nonlinear system with chaotic behavior becomes a noise amplifier with specific statistical transformation properties. 相似文献
162.
Upper bounds for survival probability of the contact process 总被引:3,自引:0,他引:3
163.
164.
Howel Tong 《应用数学学报(英文版)》2002,18(2):177-184
Abstract I reflect upon the development of nonlinear time series analysis since 1990 by focusing on five majorareas of development. These areas include the interface between nonlinear time series analysis and chaos,thenonparametric/semiparametric approach,nonlinear state space modelling,financial time series and nonlinearmodelling of panels of time series. 相似文献
165.
Endoscopic illumination systems conduct light down a built-in fibre-optic bundle to illuminate the object. Many modern endoscopes employ wide-field imaging optical systems and therefore require an illuminating beam of large divergence. This is commonly provided by placing a strong diverging lens at the far end of the fibre bundle, but it results in a poor uniformity of illumination in the object space. This paper describes the design of a telescopic illumination system to overcome this problem. 相似文献
166.
167.
Often, in engineering literature, we find control systems in which the open loop inputs are piecewise constant and take values in a finite set. Such open loop inputs cause the system to have fairly regular solutions. On the other hand, when acting in closed loop, feedback laws taking values in a finite set may not be reinterpreted as open loop inputs of the considered type. In fact, pathological behaviours such as the accumulation of discontinuities may appear (Zeno phenomenon). We give some conditions which can be used as tools for building finite valued feedback laws not causing such pathological behaviours. 相似文献
168.
In the inverse scattering transform (IST), the reflectionless Jost solutions are combined by their analytic properties in the complex spectrum parameter plane, and then can be shown to satisfy the two Lax equations indeed by Liouville theorem. So the corresponding soliton solutions certainly satisfy the nonlinear equation by compatibility condition. Especially the multi-soliton solutions of DNLS equation can be demonstrated in this way.
PACS Numbers: 05.45.Yv, 02.30.-f, 11.10.Ef 相似文献
169.
M. Maamache S. Menouar L. Krache 《International Journal of Theoretical Physics》2006,45(11):2191-2198
By using the Lewis-Riesenfeld theory and algebraic method, we present an alternative approach to obtain the exact solution of time-dependent Hamiltonian systems involving quadratic, inverse quadratic and (1/x)p+p(1/x) terms. This solution is discussed and compared with that obtained by Choi, J. R. (2003). International Journal of Theoretical Physics
42, 853].
PACS: 03.65Ge; 03.65Fd; 03.65Bz 相似文献
170.
We consider a two-dimensional Coulomb gas of positive and negative pointlike unit charges interacting via a logarithmic potential. The density (rather than the charge) correlation functions are studied. In the bulk, the form-factor theory of an equivalent sine-Gordon model is used to determine the density correlation length. At the surface of a rectilinear plain wall, the universality of the asymptotic behavior of the density correlations is suggested. A scaling analysis implies a local form of the compressibility sum rule near a hard wall. A symmetry of the Coulomb system with respect to the Möbius conformal transformation, which induces a gravitational source acting on the particle density, is established. Among the consequences, a universal term of the finite-size expansion of the grand potential is derived exactly for a disk geometry of the confining domain. 相似文献