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   34688篇
  免费   5260篇
  国内免费   3819篇
化学   13976篇
晶体学   210篇
力学   2009篇
综合类   595篇
数学   14911篇
物理学   12066篇
  2024年   79篇
  2023年   388篇
  2022年   761篇
  2021年   901篇
  2020年   1025篇
  2019年   1019篇
  2018年   906篇
  2017年   1073篇
  2016年   1463篇
  2015年   1351篇
  2014年   1940篇
  2013年   2841篇
  2012年   1992篇
  2011年   2275篇
  2010年   1984篇
  2009年   2303篇
  2008年   2504篇
  2007年   2574篇
  2006年   2128篇
  2005年   1999篇
  2004年   1563篇
  2003年   1527篇
  2002年   1253篇
  2001年   972篇
  2000年   1045篇
  1999年   918篇
  1998年   862篇
  1997年   682篇
  1996年   504篇
  1995年   396篇
  1994年   395篇
  1993年   265篇
  1992年   227篇
  1991年   185篇
  1990年   156篇
  1989年   145篇
  1988年   149篇
  1987年   114篇
  1986年   93篇
  1985年   152篇
  1984年   108篇
  1983年   57篇
  1982年   97篇
  1981年   59篇
  1980年   53篇
  1979年   59篇
  1978年   56篇
  1977年   41篇
  1976年   32篇
  1973年   20篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
A carousel is a dynamical system that describes the movement of an equilateral linkage in which the midpoint of each rod travels parallel to it. They are closely related to the floating body problem. We prove, using the work of Auerbach, that any figure that floats in equilibrium in every position is drawn by a carousel. Of special interest are such figures with rational perimetral density of the floating chords, which are then drawn by carousels. In particular, we prove that for some perimetral densities the only such figure is the circle, as the problem suggests.  相似文献   
32.
We construct a universal space for the class of proper metric spaces of bounded geometry and of given asymptotic dimension. As a consequence of this result, we establish coincidence of asymptotic dimension with asymptotic inductive dimension.  相似文献   
33.
New compactifications of symmetric spaces of noncompact type X are constructed using the asymptotic geometry of the Borel–Serre enlargement. The controlled K-theory associated to these compactifications is used to prove the integral Novikov conjecture for arithmetic groups.  相似文献   
34.
We consider a single server queue with disasters where the arrivals of customers and disasters are correlated. When a disaster occurs, it removes all the customers in the system and there requires repair time for the system to be operated normally. The stationary queue length distribution at the embedded points and at an arbitrary time are presented.  相似文献   
35.
The form of the probability density derived from the evolution in time of a previously truncated frequency distribution of animal Liveweights is of interest in animal husbandry. Truncated frequency distributions arise when the heavier animals are sold for slaughter and the lighter animals retained. The demands of modern quality assurance schemes require that, given information on animal growth, the farmer is able to estimate the number of animals that would meet the specifications at some time in the future after truncation. Assuming that animal growth can be described by a linear stochastic differential equation, we derive an explicit expression for the probability density of animal Liveweights at any time after the truncation of an initial Gaussian density. It is shown that this probability density converges rapidly to a Gaussian density, so that after about 20 days of typical growth rates for lambs, the resulting density is practically indistinguishable from Gaussian.  相似文献   
36.
马俊  高成修 《数学杂志》2003,23(2):181-184
本文通过研究匹配问题的实例空间,匈牙利算法和解空间三者之间的关系,指出S实例空间的数目与问题复杂度之间的关系既不是充分也不是必要的,而如何对问题的解空间进行合理的分解才能是问题的关键。  相似文献   
37.
Let Cld AW (X) be the hyperspace of nonempty closed subsets of a normed linear space X with the Attouch–Wets topology. It is shown that the space Cld AW (X) and its various subspaces are AR's. Moreover, if X is an infinite-dimensional Banach space with weight w(X) then Cld AW (X) is homeomorphic to a Hilbert space with weight 2 w(X).  相似文献   
38.
We give a characterization of Gaussian chaos laws on Banach function spaces which do not contain ℓ n 's uniformly. The result is applied to describe the convergence in law of U-processes with sample paths in certain Banach function spaces. __________ Published in Lietuvos Matematikos Rinkinys, Vol. 45, No. 4, pp. 553–566, October–December, 2005.  相似文献   
39.
In this paper, two classes of closely related multilinear singular and fractional integrals,which include the commutators as special cases, are studied and their boundedness on Herz type spaces is discussed. In fact, it is proved that these operators are actually not bounded in certain extreme cases.  相似文献   
40.
All the connected components of the moduli space of flat connections on SU (2) and SO (3) (trivial and non-trivial) bundles over closed oriented surfaces are determined. The symplectic structure and volumes of the non-maximal strata of the moduli space are also determined.  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