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   3002篇
  免费   412篇
  国内免费   461篇
化学   1384篇
晶体学   8篇
力学   79篇
综合类   3篇
数学   1348篇
物理学   1053篇
  2024年   1篇
  2023年   102篇
  2022年   107篇
  2021年   154篇
  2020年   162篇
  2019年   115篇
  2018年   104篇
  2017年   118篇
  2016年   119篇
  2015年   129篇
  2014年   227篇
  2013年   225篇
  2012年   266篇
  2011年   274篇
  2010年   229篇
  2009年   274篇
  2008年   194篇
  2007年   253篇
  2006年   206篇
  2005年   127篇
  2004年   105篇
  2003年   68篇
  2002年   65篇
  2001年   42篇
  2000年   35篇
  1999年   28篇
  1998年   32篇
  1997年   39篇
  1996年   15篇
  1995年   20篇
  1994年   11篇
  1993年   6篇
  1992年   6篇
  1991年   2篇
  1990年   4篇
  1989年   3篇
  1988年   1篇
  1987年   3篇
  1985年   1篇
  1984年   1篇
  1983年   1篇
  1976年   1篇
排序方式: 共有3875条查询结果,搜索用时 17 毫秒
1.
Cheng  Hongmei  Fang  Qinhe  Xia  Yang 《Applications of Mathematics》2022,67(5):615-632
Applications of Mathematics - We focus on the free boundary problems for a Leslie-Gower predator-prey model with radial symmetry in a higher dimensional environment that is initially well populated...  相似文献   
2.
Nonlinear feedback shift registers (NFSRs) are widely used in stream cipher design as building blocks. The cascade connection of NFSRs, known as an important architecture, has been adopted in Grain family of stream ciphers. In this paper, a new sufficient condition under which an NFSR cannot be decomposed into the cascade connection of two smaller NFSRs is presented, which is easy to be verified from the algebraic normal form (ANF) of the characteristic function. In fact, our results are also applicable to nonsingular Boolean functions, which actually improve a previous research of Rhodes [6] where the characteristic functions of NFSRs cannot be contained.  相似文献   
3.
In this paper we investigated the stability of fractional order fuzzy cellular neural networks with leakage delay and time varying delays. Based on Lyapunov theory and applying bounded techniques of fractional calculation, sufficient criterion are established to guarantee the stability. Hybrid feedback control is applied to derive the proposed results. Finally, numerical examples with simulation results are given to illustrate the effectiveness of the proposed method.  相似文献   
4.
屈彪  徐伟  王新艳 《运筹学学报》2021,25(2):144-148
Yair Censor,Aviv Gibali和Simeon Reich为求解变分不等式问题提出了2-次梯度外梯度算法。关于此算法的收敛性,作者给出了部分证明,有一个问题:由算法产生的迭代点列能否收敛到变分不等式问题的一个解上,没有得到解决。此问题作为一个公开问题在文章“Extensions of Korpelevich's extragradient method for the variational inequalityproblem in Euclidean space”(Optimization,61(9):1119-1132,2012)中被提出。在这篇简短的补注性文章中,对所提出的问题给出了答案:由算法产生的迭代点列能收敛到变分不等式问题的一个解上。给出2-次梯度外梯度算法的全局收敛性的一个完整证明,证明了从任意起始点开始,由算法产生的迭代点列都能收敛到变分不等式问题的一个解上。  相似文献   
5.
Li  Qingtao  Du  Guangzhi 《Numerical Algorithms》2021,88(4):1915-1936
Numerical Algorithms - In this paper, some local and parallel finite element methods based on two-grid discretizations are proposed and investigated for the unsteady Navier-Stokes equations. The...  相似文献   
6.
The analytical infinite series solution of submicron particle transport in a circular tube bounded by a porous wall, such as a pinhole, is determined under the slip velocity boundary condition, and the solution is verified by using the experimental data in the previous studies for the specific cases. The results show that particle penetration rate increases with the increase of the porous parameter, the axial pressure drop, and the pinhole radius, whereas it decreases with increasing the pinhole length. The penetration rate of nano-particles are more sensitive to the variation of these parameters. However, the differences between the penetrations of particles ranging from 0.3 μm to 1 μm are not evident because the diffusion becomes weak gradually in this size range. In addition, a further comparison is performed between the analytical solution and the existing studies, and approximate expressions are presented for accurate calculation of particle penetration rate through pinholes appearing in porous materials including filter devices and masks.  相似文献   
7.
Fuzzy Optimization and Decision Making - Linguistic information processing exists in multi-criteria decision making, and linguistic truth-valued lattice implication algebra (LTV-LIA) has definite...  相似文献   
8.
9.
Let k be a positive integer. In this paper, we prove that for a graph G with at least 4k vertices, if max{d(x),d(y)}2k for any pair of nonadjacent vertices {x,y}?V(G), then G contains k disjoint cycles. This generalizes the results given by Corrá di and Hajnal (1963), Enomoto (1998), and Wang (1999).  相似文献   
10.
The first part of this paper considers the controllability for a functional semilinear differential inclusion governed by a family of operators {A(t):t[0,b]} generating an evolution operator in a Banach space in the presence of noninstantaneous impulse effects. In the second part of this paper we study the controllability for a fractional noninstantaneous impulsive semilinear differential inclusion with delay, where the linear part is an infinitesimal generator of a C0?semigroup. Using a weakly convergent criterion in the space of piecewise continuous functions and weak topology theory (for weak sequentially closed graph operators) we establish sufficient conditions to guarantee controllability results. Examples are given to illustrate the abstract results.  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