全文获取类型
收费全文 | 11736篇 |
免费 | 1426篇 |
国内免费 | 927篇 |
专业分类
化学 | 673篇 |
晶体学 | 21篇 |
力学 | 1637篇 |
综合类 | 237篇 |
数学 | 8777篇 |
物理学 | 2744篇 |
出版年
2024年 | 30篇 |
2023年 | 116篇 |
2022年 | 140篇 |
2021年 | 236篇 |
2020年 | 305篇 |
2019年 | 286篇 |
2018年 | 363篇 |
2017年 | 367篇 |
2016年 | 442篇 |
2015年 | 297篇 |
2014年 | 510篇 |
2013年 | 929篇 |
2012年 | 551篇 |
2011年 | 635篇 |
2010年 | 596篇 |
2009年 | 681篇 |
2008年 | 728篇 |
2007年 | 716篇 |
2006年 | 707篇 |
2005年 | 633篇 |
2004年 | 557篇 |
2003年 | 512篇 |
2002年 | 491篇 |
2001年 | 374篇 |
2000年 | 398篇 |
1999年 | 346篇 |
1998年 | 268篇 |
1997年 | 274篇 |
1996年 | 197篇 |
1995年 | 216篇 |
1994年 | 147篇 |
1993年 | 150篇 |
1992年 | 136篇 |
1991年 | 103篇 |
1990年 | 95篇 |
1989年 | 54篇 |
1988年 | 49篇 |
1987年 | 40篇 |
1986年 | 43篇 |
1985年 | 46篇 |
1984年 | 50篇 |
1983年 | 23篇 |
1982年 | 49篇 |
1981年 | 27篇 |
1980年 | 32篇 |
1979年 | 28篇 |
1978年 | 22篇 |
1977年 | 25篇 |
1976年 | 20篇 |
1974年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
91.
Computability and computational complexity were first considered over the fields of real and complex numbers and generalized to arbitrary algebraic systems. This article approaches the theory of computational complexity over an arbitrary algebraic system by taking computability over the list extension for a computational model of it. We study the resultant polynomial complexity classes and mention some NP-complete problems. 相似文献
92.
Bing-sheng He Zhen-hua Yang Xiao-ming Yuan 《Journal of Mathematical Analysis and Applications》2004,300(2):139-374
Proximal point algorithms (PPA) are attractive methods for monotone variational inequalities. The approximate versions of PPA are more applicable in practice. A modified approximate proximal point algorithm (APPA) presented by Solodov and Svaiter [Math. Programming, Ser. B 88 (2000) 371–389] relaxes the inexactness criterion significantly. This paper presents an extended version of Solodov–Svaiter's APPA. Building the direction from current iterate to the new iterate obtained by Solodov–Svaiter's APPA, the proposed method improves the profit at each iteration by choosing the optimal step length along this direction. In addition, the inexactness restriction is relaxed further. Numerical example indicates the improvement of the proposed method. 相似文献
93.
This work is concerned with the maximum principle for optimal control problem governed by magnetohydrodynamic equations, which describe the motion of a viscous incompressible conducting fluid in a magnetic field and consist of a subtle coupling of the Navier-Stokes equation of viscous incompressible fluid flow and the Maxwell equation of electromagnetic field. An integral type state constraint is considered. 相似文献
94.
On Covariant Phase Space and the Variational Bicomplex 总被引:1,自引:0,他引:1
Enrique G. Reyes 《International Journal of Theoretical Physics》2004,43(5):1267-1286
The notion of a phase space in classical mechanics is well known. The extension of this concept to field theory however, is a challenging endeavor, and over the years numerous proposals for such a generalization have appeared in the literature. In this paper We review a Hamiltonian formulation of Lagrangian field theory based on an extension to infinite dimensions of J.-M. Souriau's symplectic approach to mechanics. Following G. Zuckerman, we state our results in terms of the modern geometric theory of differential equations and the variational bicomplex. As an elementary example, we construct a phase space for the Monge–Ampere equation. 相似文献
95.
The authors give the necessary and sufficient conditions for a generalized circle in a Weyl hypersurface to be generalized circle in the enveloping Weyl space. They then obtain the neccessary and sufficient conditions under which a generalized concircular transformation of one Weyl space onto another induces a generalized transformation oil its subspaces. Finally, it is shown that any totally geodesic or totally umbilical hypersurface of a generalized concircularly flat Weyl space is also generalized concircularly flat. 相似文献
96.
97.
Young Ja Park 《Proceedings of the American Mathematical Society》2004,132(7):2075-2083
A logarithmic Sobolev trace inequality is derived. Bounds on the best constant for this inequality from above and below are investigated using the sharp Sobolev inequality and the sharp logarithmic Sobolev inequality.
98.
100.
§ 1 IntroductionLetRn×mdenotetherealn×mmatrixspace ,Rn×mr itssubsetwhoseelementshaverankr ,ORn×nthesetofalln×northogonalmatrices,SRn×n(SRn×n≥ ,SRn×n>)thesetofalln×nrealsymmetric (symmetricpositivesemidefinite ,positivedefinite)matrices.ThenotationA>0 (≥ 0 ,<0 ,≤ 0 )m… 相似文献