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   6237篇
  免费   319篇
  国内免费   435篇
化学   555篇
晶体学   18篇
力学   376篇
综合类   143篇
数学   5382篇
物理学   517篇
  2025年   10篇
  2024年   29篇
  2023年   75篇
  2022年   105篇
  2021年   124篇
  2020年   133篇
  2019年   145篇
  2018年   154篇
  2017年   161篇
  2016年   163篇
  2015年   134篇
  2014年   249篇
  2013年   424篇
  2012年   259篇
  2011年   320篇
  2010年   302篇
  2009年   389篇
  2008年   402篇
  2007年   380篇
  2006年   367篇
  2005年   290篇
  2004年   262篇
  2003年   286篇
  2002年   253篇
  2001年   226篇
  2000年   194篇
  1999年   188篇
  1998年   188篇
  1997年   167篇
  1996年   102篇
  1995年   70篇
  1994年   65篇
  1993年   55篇
  1992年   41篇
  1991年   30篇
  1990年   24篇
  1989年   18篇
  1988年   14篇
  1987年   13篇
  1986年   13篇
  1985年   29篇
  1984年   26篇
  1983年   13篇
  1982年   28篇
  1981年   18篇
  1980年   19篇
  1979年   8篇
  1978年   7篇
  1977年   6篇
  1976年   6篇
排序方式: 共有6991条查询结果,搜索用时 15 毫秒
61.
将强子-核碰撞的独立源模型推广到核-核碰撞,给出了核-核碰撞末态产生粒子横能量分布方程,将其与CERN的NA35合作组得到的实验数据相比较,模型较好地解释了实验结果.  相似文献   
62.
We consider the problem of approximating an optimal solution to a separable, doubly infinite mathematical program (P) with lower staircase structure by solutions to the programs (P(N)) obtained by truncating after the firstN variables andN constraints of (P). Viewing the surplus vector variable associated with theNth constraint as a state, and assuming that all feasible states are eventually reachable from any feasible state, we show that the efficient set of all solutions optimal to all possible feasible surplus states for (P(N)) converges to the set of optimal solutions to (P). A tie-breaking algorithm which selects a nearest-point efficient solution for (P(N)) is shown (for convex programs) to converge to an optimal solution to (P). A stopping rule is provided for discovering a value ofN sufficiently large to guarantee any prespecified level of accuracy. The theory is illustrated by an application to production planning.The work of Robert L. Smith was partially supported by the National Science Foundation under Grant ECS-8700836.  相似文献   
63.
We deal with periodic groups saturated with dihedral groups. In particular, it is proved that periodic groups of bounded period, and also periodic Shunkov groups, saturated with dihedral groups, are locally finite.Supported by RFBR grant No. 03-01-00356 and by the Krasnoyarsk Science Foundation, project 11F0202C.Translated from Algebra i Logika, Vol. 44, No. 1, pp. 114–125, January–February, 2005.  相似文献   
64.
We show that any non-zero Banach space with a separable dual contains a totally disconnected, closed and bounded subset S of Hausdorff dimension 1 such that every Lipschitz function on the space is Fréchet differentiable somewhere in S.  相似文献   
65.
《Optimization》2012,61(6):545-561
In this article we consider the boolean optimization problem of finding the set of Pareto optimal solutions. The vector objectives are the positive cuts of linear functions to the non-negative semi-axis. Initial data are subject to perturbations, measured by the l 1-norm in the parameter space of the problem. We present the formula expressing the extreme level (stability radius) of such perturbations, for which a particular solution remains Pareto optimal.  相似文献   
66.
We consider an infinite-dimensional isotonic regression problem which is an extension of the suitably revised classical isotonic regression problem. Given p-summable data, for p finite and at least one, there exists an optimal estimator to our problem. For p greater than one, this estimator is unique and is the limit in the p-norm of the sequence of unique estimators in canonical finite-dimensional truncations of our problem. However, for p equal to one, our problem, as well as the finite-dimensional truncations, admit multiple optimal estimators in general. In this case, the sequence of optimal estimator sets to the truncations converges to the optimal estimator set of the infinite problem in the sense of Kuratowski. Moreover, the selection of natural best optimal estimators to the truncations converges in the 1-norm to an optimal estimator of the infinite problem.  相似文献   
67.
Given an integer polyhedron , an integer point , and a point , the primal separation problem is the problem of finding a linear inequality which is valid for P I , violated by x *, and satisfied at equality by . The primal separation problem plays a key role in the primal approach to integer programming. In this paper we examine the complexity of primal separation for several well-known classes of inequalities for various important combinatorial optimization problems, including the knapsack, stable set and travelling salesman problems.Received: November 2002, Revised: March 2003,  相似文献   
68.
In this paper, we further develop the left-definite and right-definite spectral theory associated with the self-adjoint differential operator A in L2(-1,1), generated from the classical second-order Legendre differential equation, having the sequence of Legendre polynomials as eigenfunctions. Specifically, we determine the first three left-definite spaces associated with the pair (L2(-1,1),A). As a consequence of these results, we determine the explicit domain of both the associated left-definite operator A1, first observed by Everitt, and the self-adjoint operator A1/2. In addition, we give a new characterization of the domain D(A) of A and, as a corollary, we present a new proof of the Everitt-Mari result which gives optimal global smoothness of functions in D(A).  相似文献   
69.
70.
LetG be a domain in n ,n2, letA be a connected complex (n–1)-dimensional submanifold ofG, and let be a plurisubharmonic function inGA. We obtain conditions on the growth of that guarantee the local boundedness of at a point a A G and the existence of a plurisubharmonic extension of toG.Translated fromMatematicheskie Zametki, Vol. 64, No. 1, pp. 64–72, July, 1998.The author wishes to express her gratitude to Professor E. M. Chirka for numerous useful discussions and for his assistance in writing the present text.  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