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   4094篇
  免费   81篇
  国内免费   16篇
化学   2527篇
晶体学   16篇
力学   281篇
数学   842篇
物理学   525篇
  2023年   20篇
  2022年   79篇
  2021年   104篇
  2020年   84篇
  2019年   73篇
  2018年   59篇
  2017年   46篇
  2016年   122篇
  2015年   115篇
  2014年   111篇
  2013年   204篇
  2012年   223篇
  2011年   244篇
  2010年   169篇
  2009年   151篇
  2008年   205篇
  2007年   218篇
  2006年   204篇
  2005年   185篇
  2004年   164篇
  2003年   113篇
  2002年   141篇
  2001年   44篇
  2000年   51篇
  1999年   44篇
  1998年   33篇
  1997年   42篇
  1996年   47篇
  1995年   39篇
  1994年   33篇
  1993年   43篇
  1992年   48篇
  1991年   31篇
  1990年   14篇
  1989年   21篇
  1988年   21篇
  1987年   33篇
  1986年   16篇
  1985年   40篇
  1984年   40篇
  1983年   39篇
  1982年   34篇
  1981年   47篇
  1980年   50篇
  1979年   42篇
  1978年   27篇
  1977年   30篇
  1976年   23篇
  1975年   19篇
  1967年   13篇
排序方式: 共有4191条查询结果,搜索用时 0 毫秒
1.
2.
Derivatives containing the thieno[2,3‐d]pyrimidin‐4‐one system, potential selective COX‐2 inhibitors, were prepared starting from ethyl ester of 2‐isothiocyanato‐5‐phenyl‐3‐thiophenecarboxylic acid ( 2 ); their structural elucidation is also reported.  相似文献   
3.
4.
The paper proves the existence of solutions to the magneto-hydrodynamics equations driven by random exterior forcing terms both in the velocity and in the magnetic field. The existence and uniqueness of an invariant measure is also obtained via coupling methods.  相似文献   
5.
We give a criterion to compare the physical content of different mathematical structures derived from a preparation-question structure. Then this criterion is used in order to compare the physical content of the (Jauch-Piron's) property lattice with the physical content of the poset of testable properties. We prove that for complete preparation-question structures these two structures carry the same physical content; moreover the set of testable properties has the algebraic structure of the Brouwer-Zadeh lattice. For more general preparation-question structures the physical content of the poset of testable property can be larger than that of the property lattice. Physically relevant examples of the possible cases are given.  相似文献   
6.
An adaptive pruning algorithm for the discrete L-curve criterion   总被引:1,自引:0,他引:1  
We describe a robust and adaptive implementation of the L-curve criterion. The algorithm locates the corner of a discrete L-curve which is a log–log plot of corresponding residual norms and solution norms of regularized solutions from a method with a discrete regularization parameter (such as truncated SVD or regularizing CG iterations). Our algorithm needs no predefined parameters, and in order to capture the global features of the curve in an adaptive fashion, we use a sequence of pruned L-curves that correspond to considering the curves at different scales. We compare our new algorithm to existing algorithms and demonstrate its robustness by numerical examples.  相似文献   
7.
8.
Control of light intensity and colour are two of the major features required in the realization of smart windows. We designed a bi-functional polymer dispersed liquid crystal (PDLC) film in order to satisfy such requirements, i.e. it is able both to modulate the optical transmission, if an external electric field is applied, and to change colour if exposed to sunlight. A monomer/liquid crystal mixture was doped with a small amount of photochromic material and homeotropically aligned by means of rough surfaces. A transparent and pale pink coloured film was achieved after photopolymerization. Such a film changes colour upon exposure for some seconds to sunlight or ultraviolet radiation in a persistent but reversible manner. In addition, the film appears transparent without the application of an electric field (OFF state) and becomes opaque on application of a driving voltage of about 75 V (ON state), and thus the film operates in reverse mode with respect to conventional PDLCs.  相似文献   
9.
10.
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