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   1541531篇
  免费   32227篇
  国内免费   8291篇
化学   678047篇
晶体学   20173篇
力学   74629篇
综合类   105篇
数学   240602篇
物理学   371682篇
无线电   196811篇
  2021年   14758篇
  2020年   17384篇
  2019年   17539篇
  2016年   29675篇
  2015年   21761篇
  2014年   32839篇
  2013年   78694篇
  2012年   40874篇
  2011年   37689篇
  2010年   39664篇
  2009年   44574篇
  2008年   41075篇
  2007年   38012篇
  2006年   45215篇
  2005年   37076篇
  2004年   38339篇
  2003年   35913篇
  2002年   36912篇
  2001年   37231篇
  2000年   32686篇
  1999年   29476篇
  1998年   27553篇
  1997年   27440篇
  1996年   26931篇
  1995年   24677篇
  1994年   24163篇
  1993年   23505篇
  1992年   23680篇
  1991年   23782篇
  1990年   22551篇
  1989年   22174篇
  1988年   21366篇
  1987年   20100篇
  1986年   18930篇
  1985年   25420篇
  1984年   26475篇
  1983年   22377篇
  1982年   23723篇
  1981年   22884篇
  1980年   22149篇
  1979年   22183篇
  1978年   23353篇
  1977年   22997篇
  1976年   22617篇
  1975年   21288篇
  1974年   20891篇
  1973年   21393篇
  1972年   15563篇
  1968年   13321篇
  1967年   13377篇
排序方式: 共有10000条查询结果,搜索用时 468 毫秒
11.
Journal of Communications Technology and Electronics - A quantitative comparison of the spectral characteristics of the human visual system and matrix photodetectors is carried out. Criteria for a...  相似文献   
12.
Wireless Personal Communications - Chronic kidney disease (CKD) is a gradual loss of kidney function over the period of time and it is irrevocable once functionality reaches the critical state....  相似文献   
13.
Xiao  Zhu  Chen  Yanxun  Jiang  Hongbo  Hu  Zhenzhen  Lui  John C. S.  Min  Geyong  Dustdar  Schahram 《Wireless Networks》2022,28(7):3305-3322
Wireless Networks - Unmanned aerial vehicles (UAV) have been widely used in various fields because of their high mobility and portability. At the same time, due to the rapid development of...  相似文献   
14.
Nikolaev  N. N. 《JETP Letters》2022,115(11):639-643
JETP Letters - A new approach to search for axions in the storage ring experiments, applicable at a short coherence time of the in-plane polarization as is the case for protons is discussed. The...  相似文献   
15.
Mathematical Programming - We provide a control-theoretic perspective on optimal tensor algorithms for minimizing a convex function in a finite-dimensional Euclidean space. Given a function...  相似文献   
16.
The artificially accurate design of nonmetal electrocatalysts’ active site has been a huge challenge because no pure active species with the specific structure could be strictly controlled by traditional synthetic methods. Species with a multiconfiguration in the catalyst hinder identification of the active site and the subsequent comprehension of the reaction mechanism. We have developed a novel electro-assisted molecular assembly strategy to obtain a pure pentagon ring on perfect graphene avoiding other reconstructed structures. More importantly, the active atom was confirmed by the subtle passivation process as the topmost carbon atom. Recognition of the carbon-defect electrocatalysis reaction mechanism was first downsized to the single-atom scale from the experimental perspective. It is expected that this innovative electro-assisted molecular assembly strategy could be extensively applied in the active structure-controlled synthesis of nonmetal electrocatalysts and verification of the exact active atom.  相似文献   
17.
Russian Journal of General Chemistry - Aminophosphabetaines, i.e., isobutyl {[alkyl(dimethyl)ammonio]methyl}phosphonates with higher alkyl substituents at the nitrogen atom, were obtained by a...  相似文献   
18.
The coordination chemistry of f-block elements (lanthanide and actinide) in molten salts has become a resounding topic in view of its great importance to the research and development (R&D) of molten salt reactors and pyroprocessing. In this Review article, a general overview of the coordination chemistry of f-block elements in molten salts is provided including past achievements and recent advances. Particular emphases are placed on the oxidation state, speciation, and solution structure of f-block metal ions in molten salts, as well as their relationships with the salt composition. Furthermore, this review briefly discusses the spectroscopic and theoretical methods that complement each other in revealing the coordination properties.  相似文献   
19.
20.
Chemistry of Natural Compounds - O- and N-propylamino-derivatives of betulin and betulonic acid oxime and methyl ester were synthesized. Their antitumor activity against a panel of 60 human cancer...  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