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   1489671篇
  免费   32086篇
  国内免费   8175篇
化学   643265篇
晶体学   20081篇
力学   74001篇
综合类   102篇
数学   238583篇
物理学   359488篇
无线电   194412篇
  2021年   14703篇
  2020年   17333篇
  2019年   17464篇
  2016年   29210篇
  2015年   21612篇
  2014年   32659篇
  2013年   78466篇
  2012年   38243篇
  2011年   33699篇
  2010年   38495篇
  2009年   43714篇
  2008年   37454篇
  2007年   34031篇
  2006年   42033篇
  2005年   33485篇
  2004年   35484篇
  2003年   33684篇
  2002年   34996篇
  2001年   33186篇
  2000年   30152篇
  1999年   28272篇
  1998年   27195篇
  1997年   27070篇
  1996年   26751篇
  1995年   24554篇
  1994年   24035篇
  1993年   23404篇
  1992年   22897篇
  1991年   23133篇
  1990年   21918篇
  1989年   21569篇
  1988年   20730篇
  1987年   19512篇
  1986年   18292篇
  1985年   24863篇
  1984年   26095篇
  1983年   22119篇
  1982年   23576篇
  1981年   22782篇
  1980年   22038篇
  1979年   21830篇
  1978年   23164篇
  1977年   22690篇
  1976年   22257篇
  1975年   20942篇
  1974年   20540篇
  1973年   21070篇
  1972年   15273篇
  1968年   13010篇
  1967年   13070篇
排序方式: 共有10000条查询结果,搜索用时 78 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