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   14477篇
  免费   692篇
  国内免费   445篇
化学   707篇
晶体学   43篇
力学   1148篇
综合类   93篇
数学   10783篇
物理学   2840篇
  2023年   96篇
  2022年   126篇
  2021年   155篇
  2020年   195篇
  2019年   215篇
  2018年   222篇
  2017年   280篇
  2016年   292篇
  2015年   275篇
  2014年   688篇
  2013年   909篇
  2012年   739篇
  2011年   841篇
  2010年   746篇
  2009年   935篇
  2008年   1007篇
  2007年   1049篇
  2006年   665篇
  2005年   575篇
  2004年   486篇
  2003年   470篇
  2002年   431篇
  2001年   378篇
  2000年   413篇
  1999年   358篇
  1998年   293篇
  1997年   284篇
  1996年   278篇
  1995年   269篇
  1994年   198篇
  1993年   192篇
  1992年   176篇
  1991年   145篇
  1990年   132篇
  1989年   85篇
  1988年   101篇
  1987年   69篇
  1986年   94篇
  1985年   141篇
  1984年   106篇
  1983年   44篇
  1982年   70篇
  1981年   61篇
  1980年   66篇
  1979年   55篇
  1978年   67篇
  1977年   58篇
  1976年   30篇
  1975年   13篇
  1974年   14篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
We consider applications of disjunctive programming to global optimization and problems with equilibrium constraints. We propose a modification of the algorithm of F. Beaumont for disjunctive programming problems and show its numerical efficiency.  相似文献   
12.
We present a new approach to study the convergence of Newton's method in Banach spaces, which relax the conditions appearing in the usual studies. The approach is based on the bound required for the second derivative of the operator involved. An application to a nonlinear integral equation is presented.  相似文献   
13.
Efficient measurement of the performance index (the distance of a loading parameter from the voltage collapse point) is one of the key problems in power system operations and planning and such an index indicates the severity of a power system with regard to voltage collapse. There exist many interesting methods and ideas to compute this index. However, some successful methods are not yet mathematically justified while other mathematically sound methods are often proposed directly based on the bifurcation theory and they require the initial stationary state to be too close to the unknown turning point to make the underlying methods practical.This paper first gives a survey of several popular methods for estimating the fold bifurcation point including the continuation methods, bifurcation methods and the test function methods (Seydel's direct solution methods, the tangent vector methods and the reduced Jacobian method) and discuss their relative advantages and problems. Test functions are usually based on scaling of the determinant of the Jacobian matrix and it is generally not clear how to determine the behaviour of such functions. As the underlying nonlinear equations are of a particular type, this allows us to do a new analysis of the determinants of the Jacobian and its submatrices in this paper. Following the analysis, we demonstrate how to construct a class of test functions with a predictable analytical behaviour so that a suitable index can be produced. Finally, examples of two test functions from this class are proposed. For several standard IEEE test systems, promising numerical results have been achieved.  相似文献   
14.
We present local sensitivity analysis for discrete optimal control problems with varying endpoints in the case when the customary regularity of boundary conditions can be violated. We study the behavior of the optimal solutions subject to parametric perturbations of the problem.  相似文献   
15.
We consider the problem of maximizing a linear fractional function on the Pareto efficient frontier of two other linear fractional functions. We present a finite pivoting-type algorithm that solves the maximization problem while computing simultaneously the efficient frontier. Application to multistage efficiency analysis is discussed. An example demonstrating the computational procedure is included.  相似文献   
16.
Dual fractional cutting plane algorithms, in which cutting planes are used to iteratively tighten a linear relaxation of an integer program, are well-known and form the basis of the highly successful branch-and-cut method. It is rather less well-known that various primal cutting plane algorithms were developed in the 1960s, for example by Young. In a primal algorithm, the main role of the cutting planes is to enable a feasible solution to the original problem to be improved. Research on these algorithms has been almost non-existent.  In this paper we argue for a re-examination of these primal methods. We describe a new primal algorithm for pure 0-1 problems based on strong valid inequalities and give some encouraging computational results. Possible extensions to the case of general mixed-integer programs are also discussed.  相似文献   
17.
This paper relates the author's personal experience with constraint programming and gives a personal assessment of the relationships between constraint programming and operations research.  相似文献   
18.
最速下降规则不失为一可用规则   总被引:5,自引:4,他引:1  
本从统计意义上平均迭代次数的观点出发,指出求解线性规划的最速下降规则是可取的,好用的。  相似文献   
19.
线性分式规划最优解集的求法   总被引:5,自引:0,他引:5  
本文使用多面集的表示定理,导出了线性分式规划最优解集的结构,并给出确定全部最优解的计算步骤。  相似文献   
20.
非光滑非凸多目标规划解的充分条件   总被引:4,自引:0,他引:4  
刘三阳 《应用数学》1991,4(1):58-63
Kuhn-Tucker型条件的充分性一直是最优化理论中引人注意的一个问题.本文对非光滑函数提出了几个非凸概念,然后,讨论了非光滑非凸多目标规划中Kuhn-Tucker型条件和Fritz John型条件的充分性,在很弱的条件下,建立了一系列充分条件.  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