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   30200篇
  免费   3141篇
  国内免费   1783篇
化学   11024篇
晶体学   606篇
力学   3039篇
综合类   416篇
数学   9146篇
物理学   10893篇
  2025年   82篇
  2024年   383篇
  2023年   381篇
  2022年   565篇
  2021年   711篇
  2020年   828篇
  2019年   838篇
  2018年   793篇
  2017年   920篇
  2016年   1079篇
  2015年   838篇
  2014年   1357篇
  2013年   2311篇
  2012年   1582篇
  2011年   1603篇
  2010年   1339篇
  2009年   1530篇
  2008年   1653篇
  2007年   1728篇
  2006年   1609篇
  2005年   1531篇
  2004年   1323篇
  2003年   1194篇
  2002年   1204篇
  2001年   1006篇
  2000年   944篇
  1999年   861篇
  1998年   698篇
  1997年   609篇
  1996年   541篇
  1995年   462篇
  1994年   419篇
  1993年   370篇
  1992年   308篇
  1991年   207篇
  1990年   176篇
  1989年   138篇
  1988年   136篇
  1987年   105篇
  1986年   93篇
  1985年   111篇
  1984年   104篇
  1983年   48篇
  1982年   88篇
  1981年   52篇
  1980年   49篇
  1979年   45篇
  1978年   26篇
  1977年   32篇
  1976年   35篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
An interior point method for monotone linear complementarity problems acting in a wide neighborhood of the central path is presented. The method has -iteration complexity and is superlinearly convergent even when the problem does not possess a strictly complementary solution. Mathematics Subject Classification (2000): 49M15, 65K05, 90C33 Work supported by the National Science Foundation under Grant No. 0139701. An erratum to this article is available at.  相似文献   
992.
We solve a problem proposed by Jacobson, Kézdy, and Lehel [4] concerning the existence of forbidden induced subgraph characterizations of line graphs of linear k-uniform hypergraphs with sufficiently large minimal edge-degree. Actually, we prove that for each k3 there is a finite set Z(k) of graphs such that each graph G with minimum edge-degree at least 2k2–3k+1 is the line graph of a linear k-uniform hypergraph if and only if G is a Z(k)-free graph.Acknowledgments. We thank the anonymous referees, whose suggestions helped to improve the presentation of the paper.Winter 2002/2003 DIMACS Award is gratefully acknowledged2000 Mathematics Subject Classification: 05C65 (05C75, 05C85)  相似文献   
993.
Multistage stochastic linear programming (MSLP) is a powerful tool for making decisions under uncertainty. A deterministic equivalent problem of MSLP is a large-scale linear program with nonanticipativity constraints. Recently developed infeasible interior point methods are used to solve the resulting linear program. Technical problems arising from this approach include rank reduction and computation of search directions. The sparsity of the nonanticipativity constraints and the special structure of the problem are exploited by the interior point method. Preliminary numerical results are reported. The study shows that, by combining the infeasible interior point methods and specific decomposition techniques, it is possible to greatly improve the computability of multistage stochastic linear programs.  相似文献   
994.
In this article, we study the effect of the chosen representation of a point value (and point evaluation) on the class of periodic signals realizable using a certain type of infinite-dimensional linear system. By suitably representing the point evaluation at the origin in a Hilbert space, we are able to give a complete characterization of its extensions. These extensions involve a new concept called δ-sequence, the use of which as an observation operator of an infinite-dimensional linear system is studied in this article. In particular, we consider their use in the realization of periodic signals. We also investigate how the use of δ-sequences affects the convergence properties of such realizations; we consider the rate and character of convergence and the removal of the Gibbs phenomenon. As still a further demonstration of the significance of the chosen concept of a point value, we discuss the use of distributional point values in the realization of periodic distributions. The possible applications of this work lie in regulator problems of infinite-dimensional control theory, as is indicated by the well-known internal model principle.  相似文献   
995.
We derive asymptotic expansions for tails of infinite weighted convolutions of some heavy-tailed distributions. Applications are given to tail expansion of the marginal distribution of ARMA processes, randomly stopped sums, as well as limiting waiting time distribution. AMS 2000 Subject Classifications. Primary—62E99, Secondary—41A60, 44A35, 60G50, 60K25  相似文献   
996.
王彦  徐吉华 《数学杂志》2004,24(1):89-92
Baskakov算子也是一类很重要的正线性算子,在其它领域(如概率及其它学科)都应用很广,本文利用多元分解技巧和已有的一元的结论得出多元Baskakov算子的等价一致逼近定理.  相似文献   
997.
陈建东 《大学数学》2004,20(5):45-49
研究了线性模型中回归参数 M估计的强相合性 ,在 dn=o( 1 / logn)情形下 ,给出了较弱的充分条件 .与 [1 ]中相应结论比较 ,我们将有界性条件改善为矩母函数存在性条件 ,因此作了实质性的改进  相似文献   
998.
Safe bounds in linear and mixed-integer linear programming   总被引:1,自引:0,他引:1  
Current mixed-integer linear programming solvers are based on linear programming routines that use floating-point arithmetic. Occasionally, this leads to wrong solutions, even for problems where all coefficients and all solution components are small integers. An example is given where many state-of-the-art MILP solvers fail. It is then shown how, using directed rounding and interval arithmetic, cheap pre- and postprocessing of the linear programs arising in a branch-and-cut framework can guarantee that no solution is lost, at least for mixed-integer programs in which all variables can be bounded rigorously by bounds of reasonable size. Mathematics Subject Classification (2000):primary 90C11, secondary 65G20  相似文献   
999.
1000.
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