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   30392篇
  免费   849篇
  国内免费   1119篇
化学   11540篇
晶体学   141篇
力学   295篇
综合类   83篇
数学   17737篇
物理学   2564篇
  2024年   114篇
  2023年   327篇
  2022年   299篇
  2021年   327篇
  2020年   586篇
  2019年   894篇
  2018年   879篇
  2017年   580篇
  2016年   672篇
  2015年   778篇
  2014年   1220篇
  2013年   2071篇
  2012年   1306篇
  2011年   1753篇
  2010年   1450篇
  2009年   1953篇
  2008年   2037篇
  2007年   2011篇
  2006年   1547篇
  2005年   1103篇
  2004年   971篇
  2003年   871篇
  2002年   747篇
  2001年   620篇
  2000年   606篇
  1999年   648篇
  1998年   592篇
  1997年   422篇
  1996年   495篇
  1995年   534篇
  1994年   517篇
  1993年   390篇
  1992年   380篇
  1991年   236篇
  1990年   261篇
  1989年   255篇
  1988年   179篇
  1987年   166篇
  1986年   160篇
  1985年   221篇
  1984年   179篇
  1983年   92篇
  1982年   163篇
  1981年   125篇
  1980年   135篇
  1979年   97篇
  1978年   112篇
  1977年   82篇
  1976年   71篇
  1975年   42篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
Let(X i ) be a martingale difference sequence. LetY be a standard normal random variable. We investigate the rate of uniform convergence
  相似文献   
22.
Summary We continue our study ofd-dimensional Brownian motion in a soft repulsive Poissonian potential over a long time interval [0,t]. We prove here a pinning effect: for typical configuratons, with probability tending to 1 ast tends to , the particle gets trapped close to locations of near minima of certain variational problems. These locations lie at distances growing almost linearly witht from the origin, and the particle gets pinned within distance smaller than any positive power oft of one such location. In dimension 1, we can push further our estimates and show that in a suitable sense, the particle gets trapped with high probability, within time t and within distance (logt)2+ from a suitable location at distance of ordert/(logt)3 from the origin.This article was processed by the author using the LATEX style filepljour1m from Springer-Verlag  相似文献   
23.
Continuing the earlier work on soliton sectors, we determine all finite energy representations of the XY model for almost all parameter values. In the interior of unique vacuum regions of parameters (i.e. the large external magnetic field region ||>1), the unique irreducible vacuum representation is the only finite energy representation.At the critical values of the parameters (||=1 as well as theXY symmetric case =0, ||1), there is an infinite number of mutually nonequivalent irreducible finite energy representations. Apart from the unique irreducible ground state representation and another associated irreducible representation, these infinite number of representations arise from an infinite number of nearly zero energy excitations of the ground state with a finite total energy and may be called infrared representations.In the remaining cases, as have been studied earlier, there are two additional irreducible finite energy representations besides two irreducible ground state representations and they are topological soliton sectors with different ground state limits in positive and negative spatial infinity. (For two exceptional values of parameters (, )=(0, ±1), they also become ground state representations.)  相似文献   
24.
It is widely believed that order of exactness is a good measure of the quality of an algorithm for numerical quadrature. We show that this is not the case, by exhibiting a situation in which the optimal algorithm does not even integrate constants exactly. We also show that there are situations in which the penalty for using equidistant nodes is unbounded. Finally, we show that the complexity of obtaining an -approximation can be an arbitrary function of , i.e., there is no hardest quadrature problem.  相似文献   
25.
合成并表征了5-(4-乙酰氧基苯基),10,15,20-三苯基卟啉及其金属配合物,将它们作为修饰物,制得铂支撑的双层脂膜,用循环伏安法研究了抗坏血酸的氧化还原反应,并对其机理作了探讨。  相似文献   
26.
This paper contains applications of theorems of [1] for quadratic statistics which have constant regression on linear statistics. Two theorems are proved. The first is a sufficient condition which assumes that the characteristic function of a sample is an entire function. The second gives a new characterization of the normal distribution.  相似文献   
27.
Steroid polyols from the Far-Eastern starfish Henricia sanguinolenta   总被引:2,自引:0,他引:2  
A new polyhydroxylated steroid (20R,24S)-5-cholestane-3,6,15,24-tetraol and a known glycoside, laeviuscoloside G, was isolated from the Far-Eastern starfish Henricia sanguinolenta, collected in the sea of Okhotsk, and characterized.  相似文献   
28.
We show that, for the Chebyshev weight function (1–x 2)–1/2, the Cotes numbers for the quadrature rule with nodes at the zeros of the ultraspherical polynomialP n /() are nonnegative if and only if –1/2<1.  相似文献   
29.
30.
Sans résumé
The article is the text of a talk given at the Symposium on Differential Geometry in Debrecen, Hungary, on August 28–September 3, 1975.  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