首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1341篇
  国内免费   11篇
  完全免费   18篇
  数学   1370篇
  2019年   1篇
  2018年   26篇
  2017年   6篇
  2016年   9篇
  2015年   42篇
  2014年   57篇
  2013年   56篇
  2012年   52篇
  2011年   71篇
  2010年   78篇
  2009年   95篇
  2008年   92篇
  2007年   74篇
  2006年   58篇
  2005年   47篇
  2004年   59篇
  2003年   64篇
  2002年   46篇
  2001年   51篇
  2000年   37篇
  1999年   33篇
  1998年   28篇
  1997年   36篇
  1996年   31篇
  1995年   22篇
  1994年   19篇
  1993年   27篇
  1992年   24篇
  1991年   23篇
  1990年   12篇
  1989年   13篇
  1988年   12篇
  1987年   17篇
  1986年   7篇
  1985年   6篇
  1984年   8篇
  1982年   13篇
  1981年   5篇
  1980年   4篇
  1979年   2篇
  1978年   3篇
  1976年   2篇
  1972年   2篇
排序方式: 共有1370条查询结果,搜索用时 171 毫秒
1.
Beurling's Theorem for the Bergman space   总被引:15,自引:0,他引:15  
2.
A theorem on average Liapunov functions   总被引:7,自引:0,他引:7  
A theorem on average Liapunov functions for dynamical systems is generalized. As an illustration the result is used to establish a rather strong coexistence criterion for an ecological system.  相似文献
3.
Asymptotic bounds for some bipartite graph: complete graph Ramsey numbers   总被引:6,自引:0,他引:6  
The Ramsey number r(H,Kn) is the smallest integer N so that each graph on N vertices that fails to contain H as a subgraph has independence number at least n. It is shown that r(K2,m,Kn)(m−1+o(1))(n/log n)2 and r(C2m,Kn)c(n/log n)m/(m−1) for m fixed and n→∞. Also r(K2,n,Kn)=Θ(n3/log2 n) and .  相似文献
4.
Relative perturbation bounds for the unitary polar factor   总被引:5,自引:0,他引:5  
LetB be anm×n (mn) complex (or real) matrix. It is known that there is a uniquepolar decomposition B=QH, whereQ*Q=I, then×n identity matrix, andH is positive definite, providedB has full column rank. Existing perturbation bounds suggest that in the worst case, for complex matrices the change inQ be proportional to the reciprocal ofB's least singular value, or the reciprocal of the sum ofB's least and second least singular values if matrices are real. However, there are situations where this unitary polar factor is much more accurately determined by the data than the existing perturbation bounds would indicate. In this paper the following question is addressed: how much mayQ change ifB is perturbed to $\tilde B = D_1^* BD_2 $ , whereD 1 andD 2 are nonsingular and close to the identity matrices of suitable dimensions? It is shown that for a such kind of perturbation, the change inQ is bounded only by the distances fromD 1 andD 2 to identity matrices and thus is independent ofB's singular values. Such perturbation is restrictive, but not unrealistic. We show how a frequently used scaling technique yields such a perturbation and thus scaling may result in better-conditioned polar decompositions.  相似文献
5.
Numerical analysis of oscillations in multiple well problems   总被引:5,自引:0,他引:5  
Summary. Variational problems which fail to be convex occur often in the study of ordered materials such as crystals. In these problems, the energy density for the material has multiple potential wells. In this paper, we study multiple well problems by first, determining the analytic properties of energy minimizing sequences and then, by estimating the continuous problem by an approximation using piecewise linear finite elements. We show that even when there is no minimizer of the energy, the approximations still take on a predictable structure. Received May 18, 1994  相似文献
6.
Asymptotic Upper Bounds for Ramsey Functions   总被引:5,自引:0,他引:5  
 We show that for any graph G with N vertices and average degree d, if the average degree of any neighborhood induced subgraph is at most a, then the independence number of G is at least Nf a +1(d), where f a +1(d)=∫0 1(((1−t)1/( a +1))/(a+1+(da−1)t))dt. Based on this result, we prove that for any fixed k and l, there holds r(K k + l ,K n )≤ (l+o(1))n k /(logn) k −1. In particular, r(K k , K n )≤(1+o(1))n k −1/(log n) k −2. Received: May 11, 1998 Final version received: March 24, 1999  相似文献
7.
The Baum-Connes conjecture for hyperbolic groups   总被引:4,自引:0,他引:4  
We prove the Baum-Connes conjecture for hyperbolic groups and their subgroups. Oblatum 20-VI-2001 & 24-VIII-2001?Published online: 15 April 2002 RID="*" ID="*"The second author is partially supported by NSF and MSRI.  相似文献
8.
Edge Coloring of Embedded Graphs with Large Girth   总被引:3,自引:0,他引:3  
Let G be a simple graph embedded in the surface of Euler characteristic ()0. Denote e(G), and g the edge chromatic number, the maximum degree and the girth of the graph G, respectively. The paper shows that e(G)= if 5 and g4, or 4 and g5, or 3 and g9. In addition, if ()>0, then e(G)= if 3 and g8. Acknowledgments.The authors would like to thank Dr. C.Q. Zhang for carefully reading several versions of this paper during its preparation and for suggesting several stylistic changes that have improved the overall presentation.  相似文献
9.
Optimal Control of the Obstacle for an Elliptic Variational Inequality   总被引:3,自引:0,他引:3  
An optimal control problem for an elliptic obstacle variational inequality is considered. The obstacle is taken to be the control and the solution to the obstacle problem is taken to be the state. The goal is to find the optimal obstacle from H 1 0 (Ω) so that the state is close to the desired profile while the H 1 (Ω) norm of the obstacle is not too large. Existence, uniqueness, and regularity as well as some characterizations of the optimal pairs are established. Accepted 11 September 1996  相似文献
10.
Computer communication networks and telecommunication systems are growing at an explosive rate. Some of the major factors influencing this phenomenal growth rate have been technology driven, deregulation of the telecommunication industry and the breakup of AT&T, product and service introductions and competition, new application areas, price reductions and improved services. Corporations have discovered how to use telecommunication-based systems and computer networks as a strategic competitive weapon. Modern computer networks consist of backbone networks which serve as major highways to transfer large volumes of communication traffic, and local access networks which feed traffic between the backbone network and end user nodes. The design of the local access network is a complex process which builds on many difficult combinatorial optimization problems. This paper surveys many of the problems, presents the state of the art in solving them, and demonstrates a variety of solution procedures. The paper concludes with a list of open problems and areas open for further investigation.This research was partially supported by a Dean's grant for faculty research at the Owen Graduate School of Management, Vanderbilt University, Nashville, TN 37204, USA.  相似文献
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号