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   6423篇
  免费   279篇
  国内免费   89篇
化学   4601篇
晶体学   29篇
力学   122篇
综合类   6篇
数学   1070篇
物理学   963篇
  2021年   74篇
  2020年   91篇
  2019年   81篇
  2018年   67篇
  2017年   65篇
  2016年   122篇
  2015年   131篇
  2014年   147篇
  2013年   247篇
  2012年   245篇
  2011年   321篇
  2010年   167篇
  2009年   170篇
  2008年   276篇
  2007年   260篇
  2006年   266篇
  2005年   275篇
  2004年   214篇
  2003年   183篇
  2002年   178篇
  2001年   97篇
  2000年   90篇
  1999年   85篇
  1998年   58篇
  1997年   77篇
  1996年   79篇
  1995年   80篇
  1994年   58篇
  1993年   58篇
  1992年   82篇
  1991年   56篇
  1990年   72篇
  1989年   49篇
  1988年   68篇
  1987年   71篇
  1986年   45篇
  1985年   97篇
  1984年   56篇
  1983年   64篇
  1982年   73篇
  1981年   64篇
  1980年   53篇
  1979年   69篇
  1978年   69篇
  1977年   55篇
  1976年   77篇
  1975年   76篇
  1974年   55篇
  1973年   47篇
  1970年   45篇
排序方式: 共有6791条查询结果,搜索用时 62 毫秒
121.
One-parameter semigroups occurring in operator-limit distributions are investigated. The topological-algebraic background of the relevant monoids is discussed and Lie semigroup theory is applied to the Urbanik Decomposability Semigroup.  相似文献   
122.
123.
124.
125.
126.
127.
Choquet expected utility which uses capacities (i.e. nonadditive probability measures) in place of-additive probability measures has been introduced to decision making under uncertainty to cope with observed effects of ambiguity aversion like the Ellsberg paradox. In this paper we present necessary and sufficient conditions for stochastic dominance between capacities (i.e. the expected utility with respect to one capacity exceeds that with respect to the other one for a given class of utility functions). One wide class of conditions refers to probability inequalities on certain families of sets. To yield another general class of conditions we present sufficient conditions for the existence of a probability measureP with f dC= f dP for all increasing functionsf whenC is a given capacity. Examples includen-th degree stochastic dominance on the reals and many cases of so-called set dominance. Finally, applications to decision making are given including anticipated utility with unknown distortion function.  相似文献   
128.
A method is presented that can be used (a) to determine the several lowest eigenvalues and eigenvectors of large symmetric matrices, (b) to solve the generalized eigenvalue problem associated with energy-dependent operators, that arises in computations involving energy-dependent many-body Green's functions and in the evaluation of the true parameters of the effective valence shell hamiltonian, and (c) to directly evaluate the matrices associated with resolvent operators. The applicability to large configuration mixing calculations arises when the N-electron basis functions can be easily broken down to a few dominant configurations (the primary block) and their complement. Using the partitioning technique, the effective hamiltonian within the primary block is directly evaluated. The method is extended to evaluation of the dynamical polarizability tensor, which effectively contains the contributions from all of the eigenstates of a hamiltonian matrix, without the necessity of explicitly calculating its eigenvalues and eigenvectors.  相似文献   
129.
The highly explosive molecules As(N(3))(3) and Sb(N(3))(3) were obtained in pure form by the reactions of the corresponding fluorides with (CH(3))(3)SiN(3) in SO(2) and purification by sublimation. The crystal structures and (14)N NMR, infrared, and Raman spectra were determined, and the results compared to ab initio second-order perturbation theory calculations. Whereas Sb(N(3))(3) possesses a propeller-shaped, pyramidal structure with perfect C(3) symmetry, the As(N(3))(3) molecule is significantly distorted from C(3) symmetry due to crystal packing effects.  相似文献   
130.
p-Carborane has been vinylated on the 2-B-atom in high yields using the Heck reaction. Thus, the reaction between 2-iodo-p-carborane and various styrenes [4-H-, 4-C(6)H(4)-, 4-Cl-, 4-Br-, 4-NO(2)-, 4-CH(3)O-, and 4-CH(3)-] resulted in the production of the corresponding trans-beta-(2-B-p-carboranyl)styrene in DMF solution when reacted in the presence of silver phosphate and the palladacycle Herrmann's catalyst.  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