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   8741篇
  免费   1108篇
  国内免费   342篇
化学   752篇
晶体学   13篇
力学   1005篇
综合类   324篇
数学   5488篇
物理学   2609篇
  2024年   14篇
  2023年   86篇
  2022年   218篇
  2021年   263篇
  2020年   183篇
  2019年   195篇
  2018年   221篇
  2017年   334篇
  2016年   440篇
  2015年   282篇
  2014年   532篇
  2013年   587篇
  2012年   483篇
  2011年   535篇
  2010年   423篇
  2009年   562篇
  2008年   580篇
  2007年   594篇
  2006年   479篇
  2005年   429篇
  2004年   373篇
  2003年   312篇
  2002年   294篇
  2001年   250篇
  2000年   223篇
  1999年   194篇
  1998年   179篇
  1997年   158篇
  1996年   127篇
  1995年   104篇
  1994年   71篇
  1993年   82篇
  1992年   71篇
  1991年   38篇
  1990年   44篇
  1989年   28篇
  1988年   30篇
  1987年   23篇
  1986年   29篇
  1985年   29篇
  1984年   28篇
  1983年   9篇
  1982年   18篇
  1981年   5篇
  1980年   5篇
  1979年   5篇
  1978年   3篇
  1977年   5篇
  1959年   5篇
  1957年   2篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
11.
The affine-scaling modification of Karmarkar's algorithm is extended to solve problems with free variables. This extended primal algorithm is used to prove two important results. First the geometrically elegant feasibility algorithm proposed by Chandru and Kochar is the same algorithm as the one obtained by appending a single column of residuals to the constraint matrix. Second the dual algorithm as first described by Adler et al., is the same as the extended primal algorithm applied to the dual.  相似文献   
12.
In this paper, finite-dimensional recursive filters for space-time Markov random fields are derived. These filters can be used with the expectation maximization (EM) algorithm to yield maximum likelihood estimates of the parameters of the model.  相似文献   
13.
双色激光场中1维共线氢分子离子的经典动力学研究   总被引:3,自引:0,他引:3       下载免费PDF全文
 运用经典理论方法,并采用辛算法数值求解了双色激光场作用下1维共线氢分子离子(H2+)的哈密顿正则方程,得到了氢分子离子在激光场下的经典轨迹。计算了单色场和双色场下氢分子离子(H2+)的存活几率、电离几率、解离几率、库仑爆炸几率随时间的演化,分析了双色场的相位、强度、强度比及倍频的变化对氢分子离子动力学行为的影响,并给出了相应的物理解释。  相似文献   
14.
For a discrete linear stochastic dynamical system, computation of the response matrix to the external action from a subspace using given observational data is examined. An algorithm is proposed and substantiated that makes it possible to improve the numerical accuracy and to reduce the amount of observational data compared to the general case where an arbitrary external action is allowed. As an illustration, a discrete system arising in the analysis of a linear stochastic dynamical continuous-time system is considered more thoroughly. Some numerical results are presented.  相似文献   
15.
A new method for calculating the radial spheroidal functions of the first kind is proposed for the arguments that are greater than unity in modulus. A well-known representation of these functions is refined and used for this purpose. The constructs and the software implementation proposed in the paper provide an efficient tool for the calculation of the functions with a desired accuracy in a wide range of parameters.  相似文献   
16.
Alternative procedures for representing a stochastic signal as a denumerable series with uncorrelated terms are developed. The study includes considerations about parametric rescaling and its repercussions on the orthogonal expansion, as well as numerical techniques for approaching such an expansion. In addition, applications to the Gaussian characterization of stochastic signals, filtering and stochastic modelling are treated.  相似文献   
17.
When an organization solves a portfolio problem with public projects evaluated by multiple criteria, in which the economic dimension is not essential or not well characterized, the classical methods are not useful. We propose a non-linear preference model developed from normative Value Theory and using fuzzy sets to model some sources of imprecision. This model can be considered as a generalization of the classical approaches. However, the optimization problem is very complex in order to be solved with non-linear programming techniques. Therefore, the model is exploited by an evolutionary algorithm, able to achieve a strong improvement of the quality of solution.  相似文献   
18.
Toward Fuzzy Optimization without Mathematical Ambiguity   总被引:15,自引:0,他引:15  
Fuzzy programming has been discussed widely in literature and applied in such various disciplines as operations research, economic management, business administration, and engineering. The main purpose of this paper is to present a brief review on fuzzy programming models, and classify them into three broad classes: expected value model, chance-constrained programming and dependent-chance programming. In order to solve general fuzzy programming models, a hybrid intelligent algorithm is also documented. Finally, some related topics are discussed.  相似文献   
19.
本文对有界变量线性规划的算法进行了研究,得到了一种解此问题的新算法。文中根据基线算法的算法原理,通过对BL表的旋转,在各变量满足界约束的条件下,使目标函数值不断增大,直至得到有界硬上界,从而得到问题的最优解。文中给出了有界变量线性规划基线算法的计算步骤,并给出了一个例子。与单纯形法相比,采用基线算法解有界变量线性规划操作更简单。迭代次数少,解题速度更快。  相似文献   
20.
平行机半在线排序问题研究(Ⅰ)   总被引:15,自引:1,他引:14  
对半在线平行机排序问题的研究进展作了详细综述和进一步探讨。文章给出半在线排序问题的背景、定义、分类和求解。介绍它们定义和在不同机器环境和目标函数下半在线排序问题分类,以及第一类半在线模型的近似算法的设计及其竞争比分析。  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