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   332189篇
  免费   2426篇
  国内免费   915篇
化学   146738篇
晶体学   4090篇
力学   19084篇
综合类   8篇
数学   69574篇
物理学   96036篇
  2020年   1315篇
  2019年   1434篇
  2018年   18494篇
  2017年   19063篇
  2016年   11539篇
  2015年   3381篇
  2014年   3220篇
  2013年   7939篇
  2012年   12961篇
  2011年   27429篇
  2010年   16226篇
  2009年   16576篇
  2008年   22260篇
  2007年   27348篇
  2006年   7067篇
  2005年   14145篇
  2004年   10177篇
  2003年   9783篇
  2002年   7011篇
  2001年   5039篇
  2000年   4151篇
  1999年   2982篇
  1998年   2721篇
  1997年   2617篇
  1996年   2639篇
  1995年   2361篇
  1994年   2277篇
  1993年   2150篇
  1992年   2367篇
  1991年   2471篇
  1990年   2244篇
  1989年   2267篇
  1988年   2240篇
  1987年   2114篇
  1986年   2038篇
  1985年   2673篇
  1984年   2864篇
  1983年   2324篇
  1982年   2600篇
  1981年   2467篇
  1980年   2331篇
  1979年   2461篇
  1978年   2658篇
  1977年   2427篇
  1976年   2457篇
  1975年   2344篇
  1974年   2374篇
  1973年   2400篇
  1972年   1534篇
  1971年   1357篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Algebras and Representation Theory - We would like to correct two errors in our paper Involutions of type G2 over a field of characteristic 2 [2].  相似文献   
102.
103.
The structure, chemical composition, and magnetic properties of electrochemically deposited nanocrystalline Co-Ni-Fe films were investigated using a number of techniques. A high saturation magnetic induction up to B s = 21 kG was attained. An enhancement of the saturation magnetization compared to the ideal anticipated one was revealed, which correlated with the nonlinear behavior of the structural phase composition and lattice parameters with the change of the composition. The text was submitted by the authors in English.  相似文献   
104.
Methods for phase stabilization of ammonium nitrate were sought for in order to considerably expand the application area of this oxidizing agent in various-purpose self-combustible formulations, including that in a new generation of gas-generating formulations for automobile air bags. New methods for stabilization of ammonium nitrate were studied and, in particular, a search was made for organic compounds that can stabilize ammonium nitrate even at their low content. The mechanism of phase state stabilization of ammonium nitrate by compounds of this kind was examined.  相似文献   
105.
In this work the results of the statistical topometric analysis of fracture surfaces of soda-lime-silica glass with and without ionic exchange treatment are reported. In this case, the mechanism of substitution is K+-Na+. atomic force microscopy (AFM) was employed to record the topometric data from the fracture surface. The roughness exponent (ζ) and the correlation length (ξ) were calculated by the variable bandwidth method. The analysis for both glasses (subjected and non-subjected to ionic exchange) for ζ shows a value ∼0.8, this value agrees well with that reported in the literature for rapid crack propagation in a variety of materials. The correlation length shows different values for each condition. These results, along with those of microhardness indentations suggest that the self-affine correlation length is influenced by the complex interactions of the stress field of microcracks with that resulting from the collective behavior of the point defects introduced by the strengthening mechanism of ionic exchange.  相似文献   
106.
Kinetic, sorption and selectivity properties of commercial adsorbents are improved by adding petroleum residues (tar asphaltene concentrates) 13% of whole mass. Obtained adsorbents can be used for selective extraction of nobel metals from multicomponent polymetallic solutions of heavy metals and fro sewages purification for removing arsenic.  相似文献   
107.
The European Physical Journal E - The isothermal gas adsorption of two hexane isomers (n-hexane and cyclohexane) in the mesopores of MCM-41 silica have been investigated by small angle neutron...  相似文献   
108.
All 3-dimensional convex polytopes are known to be rigid. Still their Minkowski differences (virtual polytopes) can be flexible with any finite freedom degree. We derive some sufficient rigidity conditions for virtual polytopes and present some examples of flexible ones. For example, Bricard's first and second flexible octahedra can be supplied by the structure of a virtual polytope.  相似文献   
109.
110.
Planar laser-induced fluorescence visualisation is used to investigate nonuniformities in the flow of a hypersonic conical nozzle. Possible causes for the nonuniformity are outlined and investigated, and the problem is shown to be due to a small step at the nozzle throat. Entrainment of cold boundary layer gas is postulated as the cause of the signal nonuniformity. PACS 47.80.Jk, 47.40.Ki, 47.60.+i  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