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   1243篇
  免费   23篇
  国内免费   1篇
化学   942篇
晶体学   3篇
力学   22篇
数学   174篇
物理学   126篇
  2022年   8篇
  2021年   13篇
  2020年   14篇
  2019年   17篇
  2018年   9篇
  2016年   20篇
  2015年   11篇
  2014年   21篇
  2013年   28篇
  2012年   43篇
  2011年   40篇
  2010年   23篇
  2009年   24篇
  2008年   54篇
  2007年   49篇
  2006年   40篇
  2005年   33篇
  2004年   31篇
  2003年   28篇
  2002年   39篇
  2001年   20篇
  2000年   19篇
  1999年   10篇
  1998年   9篇
  1997年   22篇
  1996年   24篇
  1995年   16篇
  1994年   22篇
  1993年   17篇
  1992年   9篇
  1991年   19篇
  1990年   22篇
  1989年   19篇
  1988年   20篇
  1987年   19篇
  1986年   25篇
  1985年   29篇
  1984年   21篇
  1983年   12篇
  1982年   27篇
  1981年   31篇
  1980年   28篇
  1979年   24篇
  1978年   24篇
  1977年   20篇
  1976年   14篇
  1975年   12篇
  1972年   10篇
  1966年   9篇
  1965年   11篇
排序方式: 共有1267条查询结果,搜索用时 15 毫秒
71.
The deep blue, paramagnetic Cs2[TcII(NO)F5] is formed during reactions of pertechnetate, acetohydroxamic acid, and CsF in aqueous HF. A reaction of Cs2[Tc(NO)F5] with BF3 · MeOH in acetonitrile gives yellow blocks of the fluorido‐bridged dimer [{TcI(NO)(CH3CN)4}2F](BF4)3. The compound is stable as solid and in acetonitrile solutions. The complex cation contains a bent μ‐F ligand and two linear nitrosyl groups.  相似文献   
72.
Benz[c]octalen     
An expedient new synthesis of benzo[c]octalene starting from the Diels-Alder adduct of benzocyclobutadiene to 7,8-dimethylenecycloocta-1,3,5-triene is described. This octalene derivative, in solution, exists as an equilibrating mixture of the double bond isomers (2) and (3) whereas in its crystalline state only the isomer (2) is present.  相似文献   
73.
74.
2,4,6-Trialkyl-1,3,5-triazines 1 can selectively be mono, bis or trisiminoformylated by reaction with trismorpholinomethane 2 or chloromethylene iminium salts 3 (Vilsmeier reagents), with each alkyl substituent reacting with only one molecule of the electrophile. The resulting aminoalkenyltriazines 4, 5 and 6 are partially or fully hydrolysed to corresponding formylation products. The latter exist either in enol or in unusual acylenamine tautomeric structures 10, 12 , and 13 , depending on the number of enamine or enol units found in the molecule. Reaction of triazines 1 with chlorobenzylidene iminium salts 16 gives monoiminobenzoylation to enaminotriazines 17 .  相似文献   
75.
76.
In [8] the author gave a report on some properties of flag space motions, especially of the composition of screw motions or rotations in flag space. Planet motions more generally are motions which can be composed by two one-parameter-groups. These motions are investigated with respect to their orbits, their multiple ways of construction and the tubular surfaces they can determine. Some of them yield tubular screw surfaces, some others move every sphere the way that it again envellopes a sphere. These motions, which have no Euclidean counterpart, determine non-trivial, kinematically generated LIE-transformations in flag space.  相似文献   
77.
78.
We investigate stationary and travelling wave solutions of a special lattice differential equation in one space dimension. Depending on a parameter λ, results are given on the existence, shape and stability for these kind of solutions. The analysis of travelling wave solutions leads us to a functional differential equation with both forward and backward shifts. The existence of solutions of this equation will be proved by use of the implicit function theorem. In particular, we consider kink solutions and periodic solutions.  相似文献   
79.
We employ a variables-in-common method for constructing multivariate Tweedie distributions, based on linear combinations of independent univariate Tweedie variables. The method lies on the convolution and scaling properties of the Tweedie laws, using the cumulant generating function for characterization of the distributions and correlation structure. The routine allows the equivalence between independence and zero correlation and gives a parametrization through given values of the mean vector and dispersion matrix, similarly to the Gaussian vector. Our approach leads to a matrix representation of multivariate Tweedie models, which permits the simulations of many known distributions, including Gaussian, Poisson, non-central gamma, gamma, and inverse Gaussian, both positively or negatively correlated.  相似文献   
80.
Journal of Theoretical Probability - We prove a functional limit theorem for vector-valued functionals of the fractional Ornstein–Uhlenbeck process, providing the foundation for the...  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