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   15095篇
  免费   1001篇
  国内免费   879篇
化学   427篇
晶体学   3篇
力学   1484篇
综合类   168篇
数学   13606篇
物理学   1287篇
  2024年   32篇
  2023年   155篇
  2022年   190篇
  2021年   207篇
  2020年   332篇
  2019年   336篇
  2018年   388篇
  2017年   393篇
  2016年   389篇
  2015年   281篇
  2014年   635篇
  2013年   1212篇
  2012年   683篇
  2011年   802篇
  2010年   710篇
  2009年   975篇
  2008年   1021篇
  2007年   1064篇
  2006年   924篇
  2005年   714篇
  2004年   629篇
  2003年   691篇
  2002年   592篇
  2001年   453篇
  2000年   462篇
  1999年   423篇
  1998年   380篇
  1997年   342篇
  1996年   269篇
  1995年   215篇
  1994年   154篇
  1993年   127篇
  1992年   125篇
  1991年   112篇
  1990年   84篇
  1989年   45篇
  1988年   44篇
  1987年   42篇
  1986年   42篇
  1985年   58篇
  1984年   54篇
  1983年   30篇
  1982年   33篇
  1981年   31篇
  1980年   22篇
  1979年   23篇
  1978年   14篇
  1977年   15篇
  1976年   10篇
  1936年   3篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
We study the corrections to the Clausius-Mossotti formula for the dielectric constant of a disordered system of polarizable spherical particles. Previously we have derived an exact cluster expansion for the correction terms. Here we study the three-body correction in detail. We derive an explicit expression for the integrand of the three-body cluster integral for a system of polarizable point dipoles.  相似文献   
82.
This paper presents a new scheduling method for manufacturing system based on the Timed Petri Net model and a reactive fast graph search algorithm. The following two typical problems are addressed in this paper. (1) Minimization of the maximum completion time. (2) Minimization of the total tardiness. As for the problem (1), a new search algorithm which combines the RTA and a rule-based supervisor is proposed. As for problem (2), the original Petri Net model is converted to its reverse model and the algorithm developed for the problem (1) is applied, regarding the due date as the starting time in the reverse model. Some numerical experiments are carried out to demonstrate usefulness of our algorithm.  相似文献   
83.
We consider the problem of maintaining a dynamic ordered set of n integers in a universe U under the operations of insertion, deletion and predecessor queries. The computation model used is a unit-cost RAM, with a word length of w bits, and the universe size is |U|=2w. We present a data structure that uses O(|U|/log|U|+n) space, performs all the operations in O(loglog|U|) time and needs O(loglog|U|/logloglog|U|) structural changes per update operation. The data structure is a simplified version of the van Emde Boas' tree introducing, in its construction and functioning, new concepts, which help to keep the important information for searching along the path of the tree, in a more compact and organized way.  相似文献   
84.
This paper presents branch-and-bound algorithms that can guarantee the simplest optimal cutting patterns of equal rectangles. An existing linear algorithm determines the global upper bound exactly. The branching process ends when a branch of a lower bound equal to the global upper bound is found.  相似文献   
85.
In this paper the algorithms for solving the p-median problem based on the Benders decomposition are investigated. A family of problems hard for solving with such algorithms is constructed and then generalized to a special NP-hard case of the p-median problem. It is shown that the effectiveness of the considered algorithms depends on the choice of the optimal values of the dual variables used in Benders cuts. In particular, the depth of the cuts can be equal to one.  相似文献   
86.
A direct central collision of two identical bodies of revolution is studied. A nonstationary mixed boundary-value problem with an unknown moving boundary is formulated. Its solution is represented by a series in term of Bessel functions. An infinite system of Volterra equations of the second kind for the unknown expansion coefficients is derived by satisfying the boundary conditions. The basic characteristics of the collision process are determined depending on the curvature of the frontal surface of the bodies  相似文献   
87.
This paper investigates the existence of positive solutions of a singular boundary value problem with negative exponent similar to standard Emden-Fowler equation. A necessary and sufficient condition for the existence of C[0, 1] positive solutions as well as C1[0, 1] positive solutions is given by means of the method of lower and upper solutions with the Schauder fixed point theorem.  相似文献   
88.
We consider the problem of determining the dielectric permittivity for a nonconducting and nonmagnetic medium. As information we take the traces of the tangential components of the electromagnetic field on the lateral surface of a cylindrical domain. These traces correspond to a solution to some direct problem for the Maxwell system. The impulse source of the current flux lies outside the domain in which the coefficient is sought. The main result of the article is a stability estimate for a solution to the inverse problem in question.  相似文献   
89.
Banach空间二阶周期边值问题解的存在性   总被引:2,自引:0,他引:2  
利用一些比较结果,讨论了Banach空间中二阶周期边值问题解的存在性,获得了若干解的存在性与唯一性结果。  相似文献   
90.
其中考虑下述泛函最小问题:求u∈W01,α(Ω),使F(u)=  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