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   7145篇
  免费   285篇
  国内免费   330篇
化学   550篇
晶体学   41篇
力学   778篇
综合类   12篇
数学   4001篇
物理学   2378篇
  2024年   11篇
  2023年   71篇
  2022年   68篇
  2021年   79篇
  2020年   126篇
  2019年   122篇
  2018年   125篇
  2017年   154篇
  2016年   163篇
  2015年   164篇
  2014年   400篇
  2013年   567篇
  2012年   333篇
  2011年   532篇
  2010年   426篇
  2009年   484篇
  2008年   535篇
  2007年   550篇
  2006年   325篇
  2005年   262篇
  2004年   252篇
  2003年   235篇
  2002年   187篇
  2001年   155篇
  2000年   179篇
  1999年   155篇
  1998年   140篇
  1997年   135篇
  1996年   106篇
  1995年   111篇
  1994年   87篇
  1993年   56篇
  1992年   45篇
  1991年   28篇
  1990年   33篇
  1989年   20篇
  1988年   16篇
  1987年   20篇
  1986年   29篇
  1985年   33篇
  1984年   32篇
  1983年   25篇
  1982年   25篇
  1981年   26篇
  1980年   36篇
  1979年   35篇
  1978年   22篇
  1977年   21篇
  1976年   7篇
  1975年   4篇
排序方式: 共有7760条查询结果,搜索用时 18 毫秒
31.
The analysis is carried out of the response of the center of gravity (dipole moment) of the distribution of noninteracting thermalized nonlinear oscillators to a sinusoidal driving force. Heat bath coupling is modeled by damping and noise. The driving is weak, but the frequency is resonant, so that there is a nonlinear resonance in the phase space. The response has a linear part that can be obtained from the perturbation analysis and a small nonlinear correction that is specific for the resonant structure.  相似文献   
32.
OSCILLATION OF A FORCED SECOND ORDER NONLINEAR EQUATION ¥KONGQINGKAI;ZHANGBINGGENAbstract:Thispapergivesseveralcriteriaontheo...  相似文献   
33.
We consider a spatially distributed hybrid system consisting of a convection/reaction system in which the reaction switches discontinuously in time between modes, independently at each spatial point on reaching “switching thresholds”. The model involves a novel formulation for evolution of the free boundary between the modal regions.  相似文献   
34.
We give a linear time algorithm for the continuous quadratic knapsack problem which is simpler than existing methods and competitive in practice. Encouraging computational results are presented for large-scale problems. The author thanks the Associate Editor and an anonymous referee for their helpful comments.  相似文献   
35.
In this paper a class of impulsive differential inclusions is investigated. The existence of solution bundle is proved. And we also construct a nonlinear semigroup of operators on cb(E) (closed-bounded subset of E) to describe the set of attainable states.  相似文献   
36.
We consider several synchronous and asynchronous multisplitting iteration schemes for solving aclass of nonlinear complementarity problems with the system matrix being an H-matrix.We establish theconvergence theorems for the schemes.The numerical experiments show that the schemes are efficient forsolving the class of nonlinear complementarity problems.  相似文献   
37.
This paper presents an efficient approach based on recurrent neural network for solving nonlinear optimization. More specifically, a modified Hopfield network is developed and its internal parameters are computed using the valid subspace technique. These parameters guarantee the convergence of the network to the equilibrium points that represent an optimal feasible solution. The main advantage of the developed network is that it treats optimization and constraint terms in different stages with no interference with each other. Moreover, the proposed approach does not require specification of penalty and weighting parameters for its initialization. A study of the modified Hopfield model is also developed to analyze its stability and convergence. Simulation results are provided to demonstrate the performance of the proposed neural network.  相似文献   
38.
How can the basic compatibility of theory and observations be investigated for nonlinear processes without requiring stochastic characterizations for residual error terms? The present paper proposes a flexible least-cost approach. For each possible estimatex for the sequence of process states, letc D (x) andx M(x) denote the costs incurred for deviations away from the prior dynamic specifications and prior measurement specifications, respectively. Define the cost-efficiency frontier to be the greatest lower bound for the set of all possible cost pairs [c D (x),c M(x)], conditional on the given observations. State sequence estimatesx that attain the cost-efficiency frontier indicate the possible ways that the actual process could have developed over time in a manner minimally incompatible with the prior dynamic and measurement specifications. An algorithm is developed for the exact sequential updating of the cost-efficient state sequence estimates as the duration of the process increases and additional observations are obtained.  相似文献   
39.
We give sufficient conditions for a sequence to have theQ-order and/or theR-order of convergence greater than one. If an additional condition is satisfied, then the sequence has an exactQ-order of convergence. We show that our results are sharp and we compare them with older results.This work was supported in part by the National Science Foundation under Grant No. DMS-85-03365. The author wishes to thank J. E. Dennis and R. A. Tapia for helpful comments, and the referee for pointing out a number of typographical and mathematical errors in the original version of this paper.  相似文献   
40.
对G.Ladas的一个开问题的解答   总被引:3,自引:0,他引:3  
本文获得了一个高阶非线性差分方程具有无界正解的充分条件,所得结果解决了G.Ladas提出的一个开问题。  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