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   215491篇
  免费   1844篇
  国内免费   649篇
化学   117976篇
晶体学   2685篇
力学   8377篇
综合类   6篇
数学   23674篇
物理学   65266篇
  2020年   2003篇
  2019年   2287篇
  2018年   3233篇
  2017年   3147篇
  2016年   4321篇
  2015年   2426篇
  2014年   3870篇
  2013年   9376篇
  2012年   7048篇
  2011年   8591篇
  2010年   6185篇
  2009年   6025篇
  2008年   8277篇
  2007年   8353篇
  2006年   7774篇
  2005年   7128篇
  2004年   6293篇
  2003年   5750篇
  2002年   5605篇
  2001年   5957篇
  2000年   4707篇
  1999年   3485篇
  1998年   3019篇
  1997年   2990篇
  1996年   2633篇
  1995年   2270篇
  1994年   2357篇
  1993年   2391篇
  1992年   2531篇
  1991年   2602篇
  1990年   2521篇
  1989年   2478篇
  1988年   2410篇
  1987年   2398篇
  1986年   2309篇
  1985年   3000篇
  1984年   3157篇
  1983年   2511篇
  1982年   2786篇
  1981年   2667篇
  1980年   2471篇
  1979年   2693篇
  1978年   2799篇
  1977年   2835篇
  1976年   2803篇
  1975年   2659篇
  1974年   2637篇
  1973年   2790篇
  1972年   1853篇
  1967年   1830篇
排序方式: 共有10000条查询结果,搜索用时 834 毫秒
51.
Journal of Solid State Electrochemistry - In this work, the use of neodymium electrodes as a basis for the immobilization of magnetite nanoparticles has been carried out. The sensitivity and...  相似文献   
52.
Molecular dynamics simulation was performed to study the formation of cluster structure, interfaces, and surfaces with different curvature radii in a perfect nanocrystal passed through by a nonlinear wave. It is shown that this process is a type of nanostructure self-organization in response to an external energy flux with subsequent development of a strong rotational field.  相似文献   
53.
54.
55.
Algebras and Representation Theory - We introduce and study the category of twisted modules over a triangular differential graded bocs. We show that in this category idempotents split, that it...  相似文献   
56.
Journal of Solid State Electrochemistry - Due to their distinctive chemical, electronic, and environmental properties, polypyrrole is used as a blocking barrier for methanol leakage in direct...  相似文献   
57.
Bruzy  N.  Coret  M.  Huneau  B.  Kermouche  G.  Mondon  M.  Bertrand  E.  Stainier  L. 《Experimental Mechanics》2019,59(8):1145-1157

The allotropic phase change from ferrite to austenite represents a moment of massive interplay between the microstructural and mechanical states of iron. The difference of compacity between the two phases induces a microplastic accommodation in the material at grain scale. However, mechanical heterogeneities resulting from the transformation process remain challenging to characterise due to the high temperature conditions it is associated with. We developed experimental equipment for in situ observation of α ? γ and γ ? α transformations. Images of the surface of an iron sample taken by an optical camera were used as input for a Digital Image Correlation (DIC) routine. Special care was taken to maximize image resolution to capture sub-grain phenomena. Observations show that, at the mesoscopic scale, shear strain fields exhibit strong localisations that are evidence of transformations that are occurring.

  相似文献   
58.
Russian Journal of General Chemistry - Highly dispersed CaO has been synthesized by heating an aqueous solution of calcium nitrate and D-glucose up to 800°C. Calcium oxide is formed with an...  相似文献   
59.
60.

A procedure was suggested for preparing brominated polyols of reduced viscosity for the synthesis of foamed polyurethanes of reduced flammability. The flame-retarding action of the synthesized polyol tetrabromophthalate in polyurethane was studied in comparison with that of other widely used flame retardants. Evaluation of the effect exerted on the flammability of the polurethane compound by the polyol tetrabromophthalate synthesized, melamine, and aluminum hydroxide shows that all the samples containing flame retardants are self-extinguishing. The shortest combustion time was observed for the sample containing 6% polyol tetrabromophthalate synthesized. The sample containing as a flame retardant additive solely the synthesized polyole tetrabromophthalate also exhibits the highest performance as a heat-insulating material from the viewpoint of thermal conductivity.

  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