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   1265293篇
  免费   32258篇
  国内免费   10063篇
化学   624667篇
晶体学   14703篇
力学   74439篇
综合类   291篇
数学   238713篇
物理学   354801篇
  2021年   13904篇
  2020年   16469篇
  2019年   16658篇
  2016年   27619篇
  2015年   21213篇
  2014年   31134篇
  2013年   75259篇
  2012年   35501篇
  2011年   29422篇
  2010年   35672篇
  2009年   38679篇
  2008年   29440篇
  2007年   24099篇
  2006年   32455篇
  2005年   23530篇
  2004年   25986篇
  2003年   25270篇
  2002年   26879篇
  2001年   24485篇
  2000年   22488篇
  1999年   21691篇
  1998年   20883篇
  1997年   20953篇
  1996年   21236篇
  1995年   18692篇
  1994年   18189篇
  1993年   17595篇
  1992年   17053篇
  1991年   17381篇
  1990年   16576篇
  1989年   16638篇
  1988年   16209篇
  1987年   16256篇
  1986年   15115篇
  1985年   21692篇
  1984年   23115篇
  1983年   19312篇
  1982年   21101篇
  1981年   20340篇
  1980年   19642篇
  1979年   19735篇
  1978年   21181篇
  1977年   20774篇
  1976年   20461篇
  1975年   19126篇
  1974年   18743篇
  1973年   19286篇
  1972年   13818篇
  1968年   11857篇
  1967年   12251篇
排序方式: 共有10000条查询结果,搜索用时 28 毫秒
11.
Crystallography Reports - The crystal structure and crystallochemical features of a Fe-deficient zirconium-rich analog of eudialyte from the Lovozero alkaline massif (Kola peninsula) have been...  相似文献   
12.
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   
13.
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   
14.
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   
15.
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   
16.
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   
17.
18.
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   
19.
Thin films with a nanometer-scale thickness are of great interest to both scientific and industrial communities due to their numerous applications and unique behaviors different from the bulk. However, the understanding of thin-film mechanics is still greatly hampered due to their intrinsic fragility and the lack of commercially available experimental instruments. In this review, we first discuss the progression of thin-film mechanical testing methods based on the supporting substrate: film-on-solid substrate method, film-on-water tensile tests, and water-assisted free-standing tensile tests. By comparing past studies on a model polymer, polystyrene, the effect of different substrates and confinement effect on the thin-film mechanics is evaluated. These techniques have generated fruitful scientific knowledge in the field of organic semiconductors for the understanding of structure–mechanical property relationships. We end this review by providing our perspective for their bright prospects in much broader applications and materials of interest.  相似文献   
20.
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