首页 | 官方网站   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   40798篇
  免费   4764篇
  国内免费   2582篇
数理化   48144篇
  2024年   44篇
  2023年   415篇
  2022年   423篇
  2021年   638篇
  2020年   1203篇
  2019年   1185篇
  2018年   1084篇
  2017年   1024篇
  2016年   1267篇
  2015年   1103篇
  2014年   1875篇
  2013年   3676篇
  2012年   2068篇
  2011年   2476篇
  2010年   2308篇
  2009年   2683篇
  2008年   2762篇
  2007年   2685篇
  2006年   2273篇
  2005年   2156篇
  2004年   1864篇
  2003年   1787篇
  2002年   1531篇
  2001年   1148篇
  2000年   1062篇
  1999年   1008篇
  1998年   936篇
  1997年   856篇
  1996年   653篇
  1995年   542篇
  1994年   478篇
  1993年   324篇
  1992年   323篇
  1991年   271篇
  1990年   248篇
  1989年   159篇
  1988年   146篇
  1987年   139篇
  1986年   159篇
  1985年   168篇
  1984年   159篇
  1983年   75篇
  1982年   156篇
  1981年   121篇
  1980年   108篇
  1979年   109篇
  1978年   64篇
  1977年   63篇
  1976年   52篇
  1973年   19篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
1.
使用Galerkin方法,结合Sobolev空间理论和不等式技巧,给出了广义神经传播方程解的存在唯一性定理,然后利用吸引子存在性定理,采用半群方法证明了方程整体吸引子的存在性.  相似文献   
2.
3.
4.
A formal computation proving a new operator identity from known ones is, in principle, restricted by domains and codomains of linear operators involved, since not any two operators can be added or composed. Algebraically, identities can be modelled by noncommutative polynomials and such a formal computation proves that the polynomial corresponding to the new identity lies in the ideal generated by the polynomials corresponding to the known identities. In order to prove an operator identity, however, just proving membership of the polynomial in the ideal is not enough, since the ring of noncommutative polynomials ignores domains and codomains. We show that it suffices to additionally verify compatibility of this polynomial and of the generators of the ideal with the labelled quiver that encodes which polynomials can be realized as linear operators. Then, for every consistent representation of such a quiver in a linear category, there exists a computation in the category that proves the corresponding instance of the identity. Moreover, by assigning the same label to several edges of the quiver, the algebraic framework developed allows to model different versions of an operator by the same indeterminate in the noncommutative polynomials.  相似文献   
5.
In this article a coupled version of the improved divergence‐free‐condition compensated method will be proposed to simulate time‐varying geometries by direct forcing immersed boundary method. The proposed method can be seen as a quasi‐multi‐moment framework due to the fact that the momentum equations are discretized by both cell‐centered and cell‐face velocity. For simulating time‐varying geometries, a semi‐implicit iterative method is proposed for calculating the direct forcing terms. Treatments for suppressing spurious force oscillations, calculating drag/lift forces, and evaluating velocity and pressure for freshly cells will also be addressed. In order to show the applicability and accuracy, analytical as well as benchmark problems will be investigated by the present framework and compared with other numerical and experimental results.  相似文献   
6.
Due to their intrinsic link with nonlinear Fokker-Planck equations and many other applications, distribution dependent stochastic differential equations (DDSDEs) have been intensively investigated. In this paper, we summarize some recent progresses in the study of DDSDEs, which include the correspondence of weak solutions and nonlinear Fokker-Planck equations, the well-posedness, regularity estimates, exponential ergodicity, long time large deviations, and comparison theorems.  相似文献   
7.
8.
9.
10.
The gold-catalyzed ring-opening rearrangement of cyclopropenes affords an efficient route to either polysubstituted naphthols or aryl-substituted furans. Owing to the unique dichotomy of gold−carbenes, this protocol provides a switchable reaction selectivity between naphthols and furans enabled by the use of TFP−Au(MeCN)SbF6 (tri(2-furyl) phosphine) or PNP(AuNTf2)2 (bis(diphenylphosphino)(isopropyl) amine) as catalysts respectively. It is proposed that the gold−carbene intermediate might be involved in the cyclopropene→naphthol rearrangement while the gold-carbocation is more likely to be involved in the cyclopropene→furan rearrangement.  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-23

京公网安备 11010802026262号