全文获取类型
收费全文 | 2985篇 |
免费 | 541篇 |
国内免费 | 403篇 |
专业分类
化学 | 351篇 |
晶体学 | 23篇 |
力学 | 318篇 |
综合类 | 61篇 |
数学 | 2253篇 |
物理学 | 923篇 |
出版年
2024年 | 26篇 |
2023年 | 38篇 |
2022年 | 54篇 |
2021年 | 52篇 |
2020年 | 82篇 |
2019年 | 96篇 |
2018年 | 116篇 |
2017年 | 111篇 |
2016年 | 125篇 |
2015年 | 102篇 |
2014年 | 160篇 |
2013年 | 297篇 |
2012年 | 162篇 |
2011年 | 198篇 |
2010年 | 171篇 |
2009年 | 183篇 |
2008年 | 185篇 |
2007年 | 201篇 |
2006年 | 186篇 |
2005年 | 158篇 |
2004年 | 127篇 |
2003年 | 117篇 |
2002年 | 133篇 |
2001年 | 119篇 |
2000年 | 105篇 |
1999年 | 102篇 |
1998年 | 74篇 |
1997年 | 75篇 |
1996年 | 48篇 |
1995年 | 49篇 |
1994年 | 41篇 |
1993年 | 26篇 |
1992年 | 33篇 |
1991年 | 17篇 |
1990年 | 13篇 |
1989年 | 12篇 |
1988年 | 16篇 |
1987年 | 8篇 |
1986年 | 11篇 |
1985年 | 15篇 |
1984年 | 13篇 |
1983年 | 10篇 |
1982年 | 11篇 |
1981年 | 12篇 |
1980年 | 9篇 |
1979年 | 10篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1974年 | 3篇 |
1973年 | 3篇 |
排序方式: 共有3929条查询结果,搜索用时 171 毫秒
21.
María G. Armentano Ricardo G. Durn 《Numerical Methods for Partial Differential Equations》2003,19(5):653-664
In this article we analyze the effect of mass‐lumping in the linear triangular finite element approximation of second‐order elliptic eigenvalue problems. We prove that the eigenvalue obtained by using mass‐lumping is always below the one obtained with exact integration. For singular eigenfunctions, as those arising in non convex polygons, we prove that the eigenvalue obtained with mass‐lumping is above the exact eigenvalue when the mesh size is small enough. So, we conclude that the use of mass‐lumping is convenient in the singular case. When the eigenfunction is smooth several numerical experiments suggest that the eigenvalue computed with mass‐lumping is below the exact one if the mesh is not too coarse. © 2003 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 19: 653–664, 2003 相似文献
22.
Let Um be an m×m Haar unitary matrix and U[m,n] be its n×n truncation. In this paper the large deviation is proven for the empirical eigenvalue density of U[m,n] as m/n→λ and n→∞. The rate function and the limit distribution are given explicitly. U[m,n] is the random matrix model of quq, where u is a Haar unitary in a finite von Neumann algebra, q is a certain projection and they are free. The limit distribution coincides with the Brown measure of the operator quq. 相似文献
23.
It has been observed that a quantum theory need not be Hermitian to have a real spectrum. We study the non-Hermitian relativistic quantum theories for many complex potentials, and obtain the real relativistic energy eigenvalues and corresponding eigenfunctions of a Dirac-charged particle in complex statically and spherically symmetric potentials. Complex Dirac–Eckart, complex Dirac–Rosen–Morse II, complex Dirac–Scarf and complex Dirac–Poschl–Teller potential are investigated. 相似文献
24.
25.
Wuqing Ning 《Journal of Mathematical Analysis and Applications》2007,327(2):1396-1419
In this paper, an algorithm is established to reconstruct an eigenvalue problem from the given data satisfying certain conditions. These conditions are proved to be not only necessary but also sufficient for the given data to coincide with the spectral characteristics corresponding to the reconstructed eigenvalue problem. 相似文献
26.
1846年,刘维尔在自己主办的杂志“纯粹与应用数学杂志”首次出版了伽罗瓦的数学研究,这对于伽罗瓦理论的传播与发展是具有决定意义的事件.伽罗瓦去世14年后,刘维尔发表伽罗瓦数学研究的原因是什么?采用数学历史文献分析法,得出四个重要原因:①伽罗瓦的朋友和弟弟的请求;②力图弥补科学院曾经造成的不公正;③刘维尔积极扶持年轻人的高贵品质使然;④刘维尔与利布里学术论战的促进. 相似文献
27.
Measurement of the First Hyperpolarizability of Substituted Ketene N,S-acetals by Hyper-Rayleigh Scattering in Solution 总被引:1,自引:1,他引:0
MeasurementoftheFirstHyperpolarizabilityofSubstitutedKeteneN,S-acetalsbyHyper-RayleighScatteringinSolutionGAOXingyu;CHENJingb... 相似文献
28.
A multidimensional version of the first Darboux problem is considered for a model second-order degenerating hyperbolic equation. Using the technique of functional spaces with a negative norm, the correct formulation of this problem in the Sobolev weighted space is proved. 相似文献
29.
Marco Marletta 《Advances in Computational Mathematics》1994,2(2):155-184
This paper discusses the numerical solution of eigenvalue problems for Hamiltonian systems of ordinary differential equations.
Two new codes are presented which incorporate the algorithms described here; to the best of the author’s knowledge, these
are the first codes capable of solving numerically such general eigenvalue problems. One of these implements a new new method
of solving a differential equation whose solution is a unitary matrix. Both codes are fully documented and are written inPfort-verifiedFortran 77, and will be available in netlib/aicm/sl11f and netlib/aicm/sl12f. 相似文献
30.
Using a generalization of the classical ballot theorem, Niu and Cooper [7] established a duality relation between the joint
distribution of several variables associated with the busy cycle inM/G/1 (with a modified first service) and the corresponding joint distribution of several related variables in its dualGI/M/1. In this note, we generalize this duality relation toGI/G/1 queues with modified first services; this clarifies the original result, and shows that the generalized ballot theorem
is superfluous for the duality relation. 相似文献