全文获取类型
收费全文 | 1772篇 |
免费 | 149篇 |
国内免费 | 133篇 |
专业分类
化学 | 654篇 |
晶体学 | 3篇 |
力学 | 22篇 |
综合类 | 9篇 |
数学 | 1214篇 |
物理学 | 152篇 |
出版年
2023年 | 14篇 |
2022年 | 29篇 |
2021年 | 23篇 |
2020年 | 38篇 |
2019年 | 50篇 |
2018年 | 39篇 |
2017年 | 32篇 |
2016年 | 54篇 |
2015年 | 56篇 |
2014年 | 73篇 |
2013年 | 151篇 |
2012年 | 60篇 |
2011年 | 70篇 |
2010年 | 76篇 |
2009年 | 95篇 |
2008年 | 123篇 |
2007年 | 113篇 |
2006年 | 102篇 |
2005年 | 105篇 |
2004年 | 77篇 |
2003年 | 68篇 |
2002年 | 61篇 |
2001年 | 63篇 |
2000年 | 50篇 |
1999年 | 36篇 |
1998年 | 45篇 |
1997年 | 32篇 |
1996年 | 23篇 |
1995年 | 18篇 |
1994年 | 22篇 |
1993年 | 16篇 |
1992年 | 10篇 |
1991年 | 11篇 |
1990年 | 20篇 |
1989年 | 9篇 |
1988年 | 5篇 |
1987年 | 13篇 |
1986年 | 4篇 |
1985年 | 13篇 |
1984年 | 11篇 |
1983年 | 12篇 |
1982年 | 20篇 |
1981年 | 10篇 |
1980年 | 17篇 |
1979年 | 17篇 |
1978年 | 11篇 |
1977年 | 17篇 |
1976年 | 22篇 |
1975年 | 4篇 |
1974年 | 7篇 |
排序方式: 共有2054条查询结果,搜索用时 171 毫秒
201.
Existence of a pareto equilibrium 总被引:9,自引:0,他引:9
S. Y. Wang 《Journal of Optimization Theory and Applications》1993,79(2):373-384
In this paper, we investigate the existence of Pareto equilibria in multicriteria games. The investigation is carried out in two ways: one follows the fixed-point technique, and the other utilizes other tools. Several sufficient conditions are presented to guarantee the existence of a Pareto equilibrium.This research was supported by NSFC under Grant No. G-78-900011 and by BMADIS. The author is grateful to the referees for supplying several valuable comments and suggestions. 相似文献
202.
203.
We study the limit behavior of the canonical (i.e., degenerate) von Mises statistics based on samples from a sequence of weakly dependent stationary observations satisfying the ψ-mixing condition. The corresponding limit distributions are defined by the multiple stochastic integrals of nonrandom functions with respect to the nonorthogonal Hilbert noises generated by Gaussian processes with nonorthogonal increments. 相似文献
204.
Sehie Park 《Proceedings of the American Mathematical Society》1996,124(10):3109-3114
We present a simple proof of the Leray-Schauder type theorem for approximable multimaps given recently by Ben-El-Mechaiekh and Idzik. We apply this theorem to obtain a Schaefer type theorem, the Birkhoff-Kellogg type theorems, a Penot type theorem for non-self-maps, and quasi-variational inequalities, all related to compact closed approximable maps.
205.
The reaction of phenyliodonium bis(phenylsulfonyl)methylide with flavones affords insertion products into the alkenyl carbon-hydrogen bond of the flavone, presumably by an electrophilic attack of the iodonium ylide on the double bond of the flavone. 相似文献
206.
P. Shumyatsky’s question 11.126 in the “Kourovka Notebook” is answered in the affirmative: it is proved that there exist a
constant c and a function of a positive integer argument f(m) such that if a finite group G admits an automorphism ϕ of order
4 having exactly m fixed points, then G has a normal series G ⩾ H ⩽ N such that |G/H| ⩽ f(m), the quotient group H/N is nilpotent
of class ⩽ 2, and the subgroup N is nilpotent of class ⩽ c (Thm. 1). As a corollary we show that if a locally finite group
G contains an element of order 4 with finite centralizer of order m, then G has the same kind of a series as in Theorem 1.
Theorem 1 generalizes Kovács’ theorem on locally finite groups with a regular automorphism of order 4, whereby such groups
are center-by-metabelian. Earlier, the first author proved that a finite 2-group with an almost regular automorphism of order
4 is almost center-by-metabelian. The proof of Theorem 1 is based on the authors’ previous works dealing in Lie rings with
an almost regular automorphism of order 4. Reduction to nilpotent groups is carried out by using Hall-Higman type theorems.
The proof also uses Theorem 2, which is of independent interest, stating that if a finite group S contains a nilpotent subgroup
T of class c and index |S: T | = n, then S contains also a characteristic nilpotent subgroup of class ⩽ c whose index is bounded
in terms of n and c. Previously, such an assertion has been known for Abelian subgroups, that is, for c = 1.
__________
Translated from Algebra i Logika, Vol. 45, No. 5, pp. 575–602, September–October, 2006. 相似文献
207.
N. S. Bakhvalov A. V. Knyazev R. R. Parashkevov 《Numerical Linear Algebra with Applications》2002,9(2):115-139
We prove extension theorems in the norms described by Stokes and Lamé operators for the three‐dimensional case with periodic boundary conditions. For the Lamé equations, we show that the extension theorem holds for nearly incompressible media, but may fail in the opposite limit, i.e. for case of absolutely compressible media. We study carefully the latter case and associate it with the Cosserat problem. Extension theorems serve as an important tool in many applications, e.g. in domain decomposition and fictitious domain methods, and in analysis of finite element methods. We consider an application of established extension theorems to an efficient iterative solution technique for the isotropic linear elasticity equations for nearly incompressible media and for the Stokes equations with highly discontinuous coefficients. The iterative method involves a special choice for an initial guess and a preconditioner based on solving a constant coefficient problem. Such preconditioner allows the use of well‐known fast algorithms for preconditioning. Under some natural assumptions on smoothness and topological properties of subdomains with small coefficients, we prove convergence of the simplest Richardson method uniform in the jump of coefficients. For the Lamé equations, the convergence is also uniform in the incompressible limit. Our preliminary numerical results for two‐dimensional diffusion problems show fast convergence uniform in the jump and in the mesh size parameter. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
208.
Let G be a graph. An independent set Y in G is called an essential independent set (or essential set for simplicity) if there is {y1,y2} (?) Y such that dist (y1,y2) = 2. In this paper, we use the technique of the vertex insertion on l-connected (l = k or k + 1, k≥ 2) graphs to provide a unified proof for G to be hamiltonian, or hamiltonian-connected. The sufficient conditions are expressed 相似文献
209.
有限局部环Z/q~kZ上矩阵广义逆的几个计数结果 总被引:2,自引:1,他引:1
吴炎 《数学的实践与认识》2004,34(10):159-164
设 R =Z/ qk Z是模整数 qk的有限局部环 ,其中 q是素数 ,k>1 .对 R上给定的 n阶矩阵 A,设 W1={X∈ Mn( R) |PAXP- 1=Q- 1XAQ, 1 P,Q∈ GLn( R) },W2 ={X∈ Mn( R) |AX =XA},W3={X∈ Mn( R) |AXA =A},W4 ={X∈ Mn( R) |XAX =X}.若 Wi≠Φ( i=1 ,2 ,3 ,4) ,用 n( Wi)表示 Wi中所有元素的个数 ,主要计算出 n( Wi) ( i =1 ,2 ,3 ,4) 相似文献
210.
We obtain simultaneous approximation equivalence theorem for Száz-Mirakian quasi-interpolants. 相似文献