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   48635篇
  免费   1809篇
  国内免费   255篇
化学   29957篇
晶体学   266篇
力学   846篇
综合类   40篇
数学   9105篇
物理学   10485篇
  2023年   346篇
  2022年   336篇
  2021年   519篇
  2020年   738篇
  2019年   694篇
  2018年   1009篇
  2017年   932篇
  2016年   1781篇
  2015年   1477篇
  2014年   1457篇
  2013年   3206篇
  2012年   3020篇
  2011年   2849篇
  2010年   1893篇
  2009年   1623篇
  2008年   2500篇
  2007年   2267篇
  2006年   2020篇
  2005年   2083篇
  2004年   1828篇
  2003年   1547篇
  2002年   1385篇
  2001年   1090篇
  2000年   1041篇
  1999年   730篇
  1998年   536篇
  1997年   454篇
  1996年   603篇
  1995年   434篇
  1994年   510篇
  1993年   459篇
  1992年   494篇
  1991年   409篇
  1990年   460篇
  1989年   368篇
  1988年   382篇
  1987年   339篇
  1986年   326篇
  1985年   467篇
  1984年   418篇
  1983年   334篇
  1982年   334篇
  1981年   352篇
  1980年   286篇
  1979年   280篇
  1978年   273篇
  1977年   269篇
  1976年   287篇
  1974年   259篇
  1973年   266篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
221.
We present two different approaches to detect and quantify phase synchronization in the case of coupled non-phase coherent oscillators. The first one is based on the general idea of curvature of an arbitrary curve. The second one is based on recurrences of the trajectory in phase space. We illustrate both methods in the paradigmatic example of the R?ssler system in the funnel regime. We show that the second method is applicable even in the case of noisy data. Furthermore, we extend the second approach to the application of chains of coupled systems, which allows us to detect easily clusters of synchronized oscillators. In order to illustrate the applicability of this approach, we show the results of the algorithm applied to experimental data from a population of 64 electrochemical oscillators.  相似文献   
222.
Quivers over a fixed base set form a monoidal category with tensor product given by pullback. The quantum Yang–Baxter equation, or more properly the braid equation, is investigated in this setting. A solution of the braid equation in this category is called a “solution” for short. Results of Etingof–Schedler–Soloviev, Lu–Yan–Zhu and Takeuchi on the set-theoretical quantum Yang–Baxter equation are generalized to the context of quivers, with groupoids playing the role of groups. The notion of “braided groupoid” is introduced. Braided groupoids are solutions and are characterized in terms of bijective 1-cocycles. The structure groupoid of a non-degenerate solution is defined; it is shown that it is a braided groupoid. The reduced structure groupoid of a non-degenerate solution is also defined. Non-degenerate solutions are classified in terms of representations of matched pairs of groupoids. By linearization we construct star-triangular face models and realize them as modules over quasitriangular quantum groupoids introduced in papers by M. Aguiar, S. Natale and the author.  相似文献   
223.
224.
225.
The rate of pertraction of Sr2+ by 18-crown-6 (18-C-6) ether and picric acid in bulk liquid membrane systems containing various surface-active substances depends not only on the concentration of 18-C-6 and picric acid but also on the presence of various surface-active substances.  相似文献   
226.
Ferric ferrocyanides synthesized from different sources of ferric cations and ferrocyanide anions and those derived from ferrous ferricyanide, ferrous ferrocyanide and ferric ferricyanide have been studied using Mössbauer and XRD techniques. Structural information of the effect of the provenance on the properties of the final compound is obtained. Significant correlations between isomer shift and quadrupole splitting of inner and outer iron cations have been observed.  相似文献   
227.
The preparation, spectroscopic properties, and crystal structure of [Cu(ind)(mco)] [ind is the anion of 1,3-bis(2-pyridylimino)isoindoline and mco is the anion of 3-hydroxy-(4H)-benzopyran-4-one] are reported. The complex exhibits a distorted square pyramidal geometry. The oxygenation of the title compound results in oxidative cleavage of the heterocyclic ring to give the (acetylsalicylato)copper(II) complex [Cu(asp)(ind)] (asp is the anion of acetylsalicylic acid) and CO as primary products, which reaction resembles the enzymatic reaction of quercetinase.  相似文献   
228.
229.
230.
We prove that the tolerance lattice TolA of an algebra A from a congruence modular variety V is 0-1 modular and satisfies the general disjointness property. If V is congruence distributive, then the lattice Tol A is pseudocomplemented. If V admits a majority term, then Tol A is 0-modular. This revised version was published online in June 2006 with corrections to the Cover Date.  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