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   38355篇
  免费   908篇
  国内免费   174篇
化学   22616篇
晶体学   250篇
力学   1122篇
综合类   10篇
数学   5206篇
物理学   10233篇
  2022年   381篇
  2021年   676篇
  2020年   559篇
  2019年   537篇
  2018年   594篇
  2017年   552篇
  2016年   1056篇
  2015年   833篇
  2014年   982篇
  2013年   1726篇
  2012年   2040篇
  2011年   2303篇
  2010年   1366篇
  2009年   1268篇
  2008年   1972篇
  2007年   1933篇
  2006年   1701篇
  2005年   2100篇
  2004年   2070篇
  2003年   1540篇
  2002年   1108篇
  2001年   903篇
  2000年   834篇
  1999年   523篇
  1998年   448篇
  1997年   411篇
  1996年   545篇
  1995年   463篇
  1994年   467篇
  1993年   502篇
  1992年   487篇
  1991年   375篇
  1990年   318篇
  1989年   328篇
  1988年   279篇
  1987年   263篇
  1986年   261篇
  1985年   351篇
  1984年   318篇
  1983年   243篇
  1982年   275篇
  1981年   264篇
  1980年   268篇
  1979年   223篇
  1978年   256篇
  1977年   221篇
  1976年   204篇
  1975年   178篇
  1974年   200篇
  1973年   190篇
排序方式: 共有10000条查询结果,搜索用时 672 毫秒
201.
We study computable trees with distinguished initial subtree (briefly, I-trees). It is proved that all I-trees of infinite height are computably categorical, and moreover, they all have effectively infinite computable dimension.  相似文献   
202.
We consider the dynamics of the lowest order transversal vibration mode of a suspension bridge, for which the hangers are treated as one-sided springs, according to the model of Lazer and McKeena [SIAM Review 58, 1990, 537]. We analyze in particular the multi-stability of periodic attractors and the basin of attraction structure in phase space and its dependence with the model parameters. The parameter values used in numerical simulations have been estimated from a number of bridges built in the United States and in the United Kingdom, thus taking into account realistic, yet sometimes simplified, structural, aerodynamical, and physical considerations.  相似文献   
203.
A time‐marching formulation is derived from the space–time integrated least squares (STILS) method for solving a pure hyperbolic convection equation and is numerically compared to various known methods. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   
204.
The effect of the vibration strain amplitude on the Young modulus and ultrasonic absorption (internal friction) in biomorphic SiC ceramics is investigated in the temperature range 116–296 K. The biomorphic SiC ceramics is prepared through pyrolysis of eucalyptus with subsequent infiltration of silicon. It is demonstrated that the vibration loading of samples in air and under vacuum is accompanied by a number of unexpected effects. The behavior of the studied ceramics is governed by at least two mechanisms, which, to a large extent, are responsible for the elastic and inelastic properties of the material. One mechanism is associated with the adsorption-desorption of environmental molecules (hypothetically, owing to the presence of pores and residual carbon), and the other mechanism involves microplastic deformation due to the motion of dislocations or other (similar) structural units.  相似文献   
205.
206.
In this work we show that the energy associated to the linear three-dimensional magneto-elastic system decays polynomially to zero as time goes to infinity, provided the initial data is smooth enough.  相似文献   
207.
This paper describes a robust and fast fitting procedure applicable for relaxing processes that cannot be understood as a discrete sum of single processes but require an activation energy distribution. The method is based on a set of closed-form expressions that allow the computation of the relaxation parameters directly from the isochronal curves obtained experimentally. The usefulness of this method is checked by analyzing the isochronal curves given by a theoretical energy distribution and the magnetic disaccommodation spectra observed in yttrium iron garnet (YIG) samples. PACS 02.60.Ed; 75.60.Lr; 75.50.Gg  相似文献   
208.
209.
H. J. Munkholm obtained a generalization for topological manifolds of the famous Borsuk–Ulam type theorem proved by Conner and Floyd. The purpose of this paper is to prove a version of Conner and Floyd's theorem for generalized manifolds.  相似文献   
210.
In finite dimensional Euclidean space, we prove the contractibility of the efficient frontier of simply shaded sets. This work extends the result of Peleg [7], which confirms the contractibility of the efficient frontier in the convex case.  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