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   46031篇
  免费   8340篇
  国内免费   1423篇
化学   47332篇
晶体学   335篇
力学   580篇
综合类   1篇
数学   4097篇
物理学   3449篇
  2021年   184篇
  2020年   1303篇
  2019年   2643篇
  2018年   1045篇
  2017年   672篇
  2016年   3468篇
  2015年   3612篇
  2014年   3549篇
  2013年   4384篇
  2012年   3154篇
  2011年   2365篇
  2010年   2966篇
  2009年   2921篇
  2008年   2599篇
  2007年   1951篇
  2006年   1672篇
  2005年   1855篇
  2004年   1663篇
  2003年   1524篇
  2002年   2180篇
  2001年   1479篇
  2000年   1377篇
  1999年   460篇
  1998年   164篇
  1997年   193篇
  1996年   174篇
  1995年   155篇
  1994年   171篇
  1993年   188篇
  1992年   179篇
  1991年   141篇
  1990年   155篇
  1989年   156篇
  1988年   169篇
  1987年   157篇
  1986年   128篇
  1985年   254篇
  1984年   218篇
  1983年   134篇
  1982年   195篇
  1981年   175篇
  1980年   211篇
  1979年   216篇
  1978年   211篇
  1977年   253篇
  1976年   200篇
  1975年   183篇
  1974年   142篇
  1973年   196篇
  1972年   104篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
Summary We discuss the limiting path measures of Markov processes with either a mean field or a polaron type interaction of the paths. In the polaron type situation the strength is decaying at large distances on the time axis, and so the interaction is of short range in time. In contrast, in the mean field model, the interaction is weak, but of long range in time. Donsker and Varadhan proved that for the partition functions, there is a transition from the polaron type to the mean field interaction when passing to a limit by letting the strength tend to zero while increasing the range. The discussion of the path measures is more subtle. We treat the mean field case as an example of a differentiable interaction and discuss the transition from the polaron type to the mean field interaction for two instructive examples.Research supported by the Swiss National Foundation (21-29833.90)This article was processed by the authors using the Springer-Verlag TEX ProbTh macro package 1991.  相似文献   
4.
5‐Amino‐4‐methyl‐2‐phenyl‐6‐substitutedfuro[2,3‐d]pyrimidines ( 2a‐c ) were reacted with 2,5‐dimethoxytetrahydrfuran to afford the pyrrolyl derivatives 3a‐c . Compound 3a was chosen as intermediate for the synthesis of poly fused heterocycles incorporated furopyrimidines moiety 4–11 . Some of the synthesized compounds were screened for their antibacterial and antifungal activities.  相似文献   
5.
Three new polyoxygenated steroids, muricesteroid ( 1 ), and menellsteroids A ( 2 ) and B ( 3 ), were isolated from two species of the South China Sea gorgonian Muricella flexuosa and Menella verrucosa Brundin , respectively. The structures of these new compounds were elucidated on the basis of extensive spectroscopic analysis, chemical methods and comparison with known related compounds.  相似文献   
6.
It is proved that the variety of relevant disjunction lattices has the finite embeddability property. It follows that Avron's relevance logic RMI min has a strong form of the finite model property, so it has a solvable deducibility problem. This strengthens Avron's result that RMI min is decidable. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
7.
8.
9.
A graph G is N2locally connected if for every vertex ν in G, the edges not incident with ν but having at least one end adjacent to ν in G induce a connected graph. In 1990, Ryjá?ek conjectured that every 3‐connected N2‐locally connected claw‐free graph is Hamiltonian. This conjecture is proved in this note. © 2004 Wiley Periodicals, Inc. J Graph Theory 48: 142–146, 2005  相似文献   
10.
The inhomogeneous Dirichlet problems concerning divergence form elliptic equations are studied. Optimal regularity requirements on the coefficients and domains for the W1,p theory, 1 < p < ∞, are obtained. The principal coefficients are supposed to be in the John‐Nirenberg space with small BMO seminorms. The domain is a Reifenberg domain. These conditions for the W1,p theory not only weaken the requirements on the coefficients but also lead to a more general geometric condition on the domains. In fact, these domains might have fractal dimensions. © 2004 Wiley Periodicals, Inc.  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