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   24001篇
  免费   1706篇
  国内免费   1082篇
化学   1540篇
晶体学   30篇
力学   2577篇
综合类   310篇
数学   19762篇
物理学   2570篇
  2024年   44篇
  2023年   238篇
  2022年   362篇
  2021年   527篇
  2020年   513篇
  2019年   539篇
  2018年   611篇
  2017年   704篇
  2016年   668篇
  2015年   506篇
  2014年   1037篇
  2013年   1675篇
  2012年   1236篇
  2011年   1217篇
  2010年   1117篇
  2009年   1482篇
  2008年   1529篇
  2007年   1604篇
  2006年   1364篇
  2005年   1134篇
  2004年   942篇
  2003年   985篇
  2002年   863篇
  2001年   691篇
  2000年   707篇
  1999年   586篇
  1998年   571篇
  1997年   528篇
  1996年   393篇
  1995年   366篇
  1994年   275篇
  1993年   230篇
  1992年   227篇
  1991年   186篇
  1990年   155篇
  1989年   102篇
  1988年   93篇
  1987年   82篇
  1986年   84篇
  1985年   115篇
  1984年   106篇
  1983年   43篇
  1982年   59篇
  1981年   49篇
  1980年   40篇
  1979年   62篇
  1978年   37篇
  1977年   45篇
  1976年   26篇
  1974年   8篇
排序方式: 共有10000条查询结果,搜索用时 58 毫秒
991.
多目标规划的整体解   总被引:2,自引:0,他引:2  
本文在较弱的广义凸性假定下讨论多目标规划的几种整体有效性.给出的定理统一了目前已有的一些关于多目标规划局部解为整体解的充分条件.  相似文献   
992.
本文对具有状态终端约束、控制受限的非线性连续最优控制问题给出一种新的可实现的离散方法,此方法通过求解非线最小二乘问题避免这类问题离散后出现的不可行现象,文中给出这种做法的理论证明和实现方案。  相似文献   
993.
Extended well-posedness of optimization problems   总被引:8,自引:0,他引:8  
The well-posedness concept introduced in Ref. 1 for global optimization problems with a unique solution is generalized here to problems with many minimizers, under the name of extended well-posedness. It is shown that this new property can be characterized by metric criteria, which parallel to some extent those known about generalized Tikhonov well-posedness.This work was partially supported by MURST, Fondi 40%, Rome, Italy.  相似文献   
994.
995.
Test examples for nonlinear programming codes   总被引:3,自引:0,他引:3  
The increasing importance of nonlinear programming software requires an enlarged set of test examples. The purpose of this note is to point out how an interested mathematical programmer could obtain computer programs of more than 120 constrained nonlinear programming problems which have been used in the past to test and compare optimization codes.  相似文献   
996.
Optimal control problems with a vector performance index and uncertainty in the state equations are investigated. Nature chooses the uncertainty, subject to magnitude bounds. For these problems, a definition of optimality is presented. This definition reduces to that of a minimax control in the case of a scalar cost and to Pareto optimality when there is no uncertainty or disturbance present. Sufficient conditions for a control to satisfy this definition of optimality are derived. These conditions are in terms of a related two-player zero-sum differential game and suggest a technique for determining the optimal control. The results are illustrated with an example.This research was supported by AFOSR under Grant No. 76-2923.  相似文献   
997.
The deterministic linear-system, quadratic-cost optimal control problem is considered when the only state information available is a partial linear observation of the initial statex 0. Thus, it is only known that the initial condition belongs to a particular linear variety. A control function is found which is optimal, in the sense (roughly) that (i) it can be computed using available information aboutx 0 and (ii) no other control function which can be found using that information gives lower cost than it does for every initial condition that could have given rise to the information. The optimal control can be found easily from the conventional Riccati equation of optimal control. Applications are considered in the presence of unknown exponential disturbances and to the case with a sequence of partial state observations.  相似文献   
998.
The Chow—Yorke algorithm is a nonsimplicial homotopy type method for computing Brouwer fixed points that is globally convergent. It is efficient and accurate for fixed point problems. L.T. Watson, T.Y. Li, and C.Y. Wang have adapted the method for zero finding problems, the nonlinear complementarity problem, and nonlinear two-point boundary value problems. Here theoretical justification is given for applying the method to some mathematical programming problems, and computational results are presented.This work was partially supported by NSF Grant MCS 7821337.  相似文献   
999.
The convergence properties of different updating methods for the multipliers in augmented Lagrangians are considered. It is assumed that the updating of the multipliers takes place after each line search of a quasi-Newton method. Two of the updating methods are shown to be linearly convergent locally, while a third method has superlinear convergence locally. Modifications of the algorithms to ensure global convergence are considered. The results of a computational comparison with other methods are presented.This work was supported by the Swedish Institute of Applied Mathematics.  相似文献   
1000.
A differential geometric approach to the constrained function maximization problem is presented. The continuous analogue of the Newton-Raphson method due to Branin for solving a system of nonlinear equations is extended to the case where the system is under-determined. The method is combined with the continuous analogue of the gradient-projection method to obtain a constrained maximization method with enforced constraint restoration. Detailed analysis of the global behavior of both methods is provided. It is shown that the conjugate-gradient algorithm can take advantage of the sparse structure of the problem in the computation of a vector field, which constitutes the main computational task in the methods.This is part of a paper issued as Stanford University, Computer Science Department Report No. STAN-CS-77-643 (Ref. 45), which was presented at the Gatlinburg VII Conference, Asilomar, California, 1977. This work was supported in part by NSF Grant No. NAT BUR OF ECON RES/PO No. 4369 and by Department of Energy Contract No. EY-76-C-02-0016.The main part of this work was presented at the Japan-France Seminar on Functional Analysis and Numerical Analysis, Tokyo, Japan, 1976. The paper was prepared in part while the author was a visitor at the Department of Mathematics, North Carolina State University, Raleigh, North Carolina, 1976–77, and was completed while he was a visitor at the Computer Science Department, Stanford University, Stanford, California, 1977. He acknowledges the hospitality and stimulating environment provided by Professor G. H. Golub, Stanford University, and Professors N. J. Rose and C. D. Meyer, North Carolina State University.  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