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   1499236篇
  免费   32189篇
  国内免费   8203篇
化学   649737篇
晶体学   20026篇
力学   74136篇
综合类   103篇
数学   239071篇
物理学   361578篇
无线电   194977篇
  2021年   14725篇
  2020年   17337篇
  2019年   17482篇
  2016年   29190篇
  2015年   21640篇
  2014年   32734篇
  2013年   78603篇
  2012年   38384篇
  2011年   33605篇
  2010年   38364篇
  2009年   43536篇
  2008年   37427篇
  2007年   34123篇
  2006年   42420篇
  2005年   33563篇
  2004年   35700篇
  2003年   33940篇
  2002年   35305篇
  2001年   34587篇
  2000年   30966篇
  1999年   28674篇
  1998年   27363篇
  1997年   27219篇
  1996年   26806篇
  1995年   24619篇
  1994年   24099篇
  1993年   23467篇
  1992年   23259篇
  1991年   23392篇
  1990年   22238篇
  1989年   21861篇
  1988年   21014篇
  1987年   19798篇
  1986年   18599篇
  1985年   25154篇
  1984年   26284篇
  1983年   22237篇
  1982年   23648篇
  1981年   22855篇
  1980年   22099篇
  1979年   22042篇
  1978年   23260篇
  1977年   22875篇
  1976年   22437篇
  1975年   21130篇
  1974年   20752篇
  1973年   21266篇
  1972年   15436篇
  1968年   13205篇
  1967年   13278篇
排序方式: 共有10000条查询结果,搜索用时 328 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