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   1508712篇
  免费   32639篇
  国内免费   8716篇
化学   655474篇
晶体学   20084篇
力学   74385篇
综合类   146篇
数学   240262篇
物理学   363378篇
无线电   196338篇
  2021年   14930篇
  2020年   17505篇
  2019年   17655篇
  2016年   29455篇
  2015年   21880篇
  2014年   33032篇
  2013年   79072篇
  2012年   38978篇
  2011年   34268篇
  2010年   38797篇
  2009年   43911篇
  2008年   38036篇
  2007年   34761篇
  2006年   42926篇
  2005年   34073篇
  2004年   36153篇
  2003年   34419篇
  2002年   35862篇
  2001年   35005篇
  2000年   31273篇
  1999年   28853篇
  1998年   27476篇
  1997年   27297篇
  1996年   26905篇
  1995年   24697篇
  1994年   24171篇
  1993年   23547篇
  1992年   23334篇
  1991年   23443篇
  1990年   22285篇
  1989年   21922篇
  1988年   21055篇
  1987年   19843篇
  1986年   18623篇
  1985年   25212篇
  1984年   26338篇
  1983年   22262篇
  1982年   23674篇
  1981年   22882篇
  1980年   22123篇
  1979年   22071篇
  1978年   23279篇
  1977年   22897篇
  1976年   22468篇
  1975年   21153篇
  1974年   20770篇
  1973年   21284篇
  1972年   15448篇
  1968年   13213篇
  1967年   13285篇
排序方式: 共有10000条查询结果,搜索用时 351 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