全文获取类型
收费全文 | 7891篇 |
免费 | 876篇 |
国内免费 | 652篇 |
专业分类
化学 | 491篇 |
晶体学 | 2篇 |
力学 | 724篇 |
综合类 | 183篇 |
数学 | 6588篇 |
物理学 | 1431篇 |
出版年
2024年 | 12篇 |
2023年 | 78篇 |
2022年 | 90篇 |
2021年 | 108篇 |
2020年 | 185篇 |
2019年 | 192篇 |
2018年 | 227篇 |
2017年 | 251篇 |
2016年 | 290篇 |
2015年 | 162篇 |
2014年 | 308篇 |
2013年 | 696篇 |
2012年 | 335篇 |
2011年 | 425篇 |
2010年 | 366篇 |
2009年 | 481篇 |
2008年 | 527篇 |
2007年 | 493篇 |
2006年 | 498篇 |
2005年 | 440篇 |
2004年 | 394篇 |
2003年 | 329篇 |
2002年 | 340篇 |
2001年 | 253篇 |
2000年 | 307篇 |
1999年 | 225篇 |
1998年 | 197篇 |
1997年 | 196篇 |
1996年 | 144篇 |
1995年 | 144篇 |
1994年 | 92篇 |
1993年 | 101篇 |
1992年 | 75篇 |
1991年 | 48篇 |
1990年 | 62篇 |
1989年 | 35篇 |
1988年 | 31篇 |
1987年 | 34篇 |
1986年 | 30篇 |
1985年 | 26篇 |
1984年 | 30篇 |
1983年 | 13篇 |
1982年 | 23篇 |
1981年 | 14篇 |
1980年 | 17篇 |
1979年 | 16篇 |
1978年 | 20篇 |
1977年 | 19篇 |
1974年 | 9篇 |
1973年 | 9篇 |
排序方式: 共有9419条查询结果,搜索用时 31 毫秒
111.
The adaptive cross approximation (ACA) algorithm (Numer. Math. 2000; 86 :565–589; Computing 2003; 70 (1):1–24) provides a means to compute data‐sparse approximants of discrete integral formulations of elliptic boundary value problems with almost linear complexity. ACA uses only few of the original entries for the approximation of the whole matrix and is therefore well‐suited to speed up existing computer codes. In this article we extend the convergence proof of ACA to Galerkin discretizations. Additionally, we prove that ACA can be applied to integral formulations of systems of second‐order elliptic operators without adaptation to the respective problem. The results of applying ACA to boundary integral formulations of linear elasticity are reported. Furthermore, we comment on recent implementation issues of ACA for non‐smooth boundaries. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
112.
Two matrix approximation problems are considered: approximation of a rectangular complex matrix by subunitary matrices with
respect to unitarily invariant norms and a minimal rank approximation with respect to the spectral norm. A characterization
of a subunitary approximant of a square matrix with respect to the Schatten norms, given by Maher, is extended to the case
of rectangular matrices and arbitrary unitarily invariant norms. Iterative methods, based on the family of Gander methods
and on Higham’s scaled method for polar decomposition of a matrix, are proposed for computing subunitary and minimal rank
approximants. Properties of Gander methods are investigated in details.
AMS subject classification (2000) 65F30, 15A18 相似文献
113.
114.
Analogues of the well-known Kolosov–Muskhelishvili formulas of general representations are obtained for nonhomogeneous equations of statics in the case of the theory of elastic mixtures. It is shown that in this theory the displacement and stress vector components, as well as the stress tensor components, are represented through four arbitrary analytic functions.The usual Cauchy–Riemann conditions are generalized for homogeneous equations of statics in the theory of elastic mixtures. 相似文献
115.
In this paper, based on the Pauli matrices, a notion of augmented spinor space is introduced, and a uniqueness of such augmented spinor space of rank n is proved. It may be expected that this new notion of spaces can be used in mathematical physics and geometry. 相似文献
116.
在本文中,我们提出了双凹规划问题和更一般的广义凹规划问题。我们给出了双凹规划问题的整体最优性条件,并构造了一个有限终止外逼近算法。 相似文献
117.
半群K(n,r)中的幂等生成元 总被引:1,自引:0,他引:1
设Singn是由一个n元集上的所有奇异变换所构成的奇异变换半群,I是由Singn中一些亏数为1的幂等元组成的集合,Howie利用有向图证明了:I是Singn的一个生成集当且仅当与其相应的有向图D(I)是强连通的完全图,本文利用多重有向图将这一结果推广到Singn的每个理想K(,r)上。 相似文献
118.
The sum of the largest eigenvalues of a symmetric matrix is a nonsmooth convex function of the matrix elements. Max characterizations for this sum are established, giving a concise characterization of the subdifferential in terms of a dual matrix. This leads to a very useful characterization of the generalized gradient of the following convex composite function: the sum of the largest eigenvalues of a smooth symmetric matrix-valued function of a set of real parameters. The dual matrix provides the information required to either verify first-order optimality conditions at a point or to generate a descent direction for the eigenvalue sum from that point, splitting a multiple eigenvalue if necessary. Connections with the classical literature on sums of eigenvalues and eigenvalue perturbation theory are discussed. Sums of the largest eigenvalues in the absolute value sense are also addressed.This paper is dedicated to Phil Wolfe on the occasion of his 65th birthday.The work of this author was supported by the National Science Foundation under grants CCR-8802408 and CCR-9101640.The work of this author was supported in part during a visit to Argonne National Laboratory by the Applied Mathematical Sciences subprogram of the Office of Energy Research of the U.S. Department of Energy under contract W-31-109-Eng-38, and in part during a visit to the Courant Institute by the U.S. Department of Energy under Contract DEFG0288ER25053. 相似文献
119.
In this paper,applying the concept of generalized KKM map,we study problems ofvariational inequalities.We weaken convexity(concavity)conditions for a functional of two variables■(x,y)in the general variational inequalities.Last,we show a proof of non-topological degree meth-od of acute angle principle about monotone operator as an application of these results. 相似文献
120.
Steven J. Sepanski 《Journal of Theoretical Probability》1997,10(4):1053-1063
For independent identically distributed random vectors belonging to the generalized Domain of Attraction of the multivariate normal law, we define two partial sum processes analogous to that of Donsker's Theorem. We prove that each converges in distribution to a Brownian Motion in the space of continuous functions. One process uses nonrandom operator normalization, and the other is a studentization of the first, using normalization by the empirical covariance operator. 相似文献