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   215224篇
  免费   1774篇
  国内免费   626篇
化学   117847篇
晶体学   3270篇
力学   8365篇
综合类   6篇
数学   23318篇
物理学   64818篇
  2020年   1972篇
  2019年   2263篇
  2018年   3205篇
  2017年   3113篇
  2016年   4268篇
  2015年   2374篇
  2014年   3823篇
  2013年   9267篇
  2012年   6906篇
  2011年   8445篇
  2010年   6079篇
  2009年   5931篇
  2008年   8150篇
  2007年   8224篇
  2006年   7640篇
  2005年   6948篇
  2004年   6172篇
  2003年   5644篇
  2002年   5500篇
  2001年   5943篇
  2000年   4686篇
  1999年   3473篇
  1998年   3011篇
  1997年   3034篇
  1996年   2826篇
  1995年   2321篇
  1994年   2420篇
  1993年   2450篇
  1992年   2597篇
  1991年   2658篇
  1990年   2560篇
  1989年   2534篇
  1988年   2465篇
  1987年   2435篇
  1986年   2358篇
  1985年   3039篇
  1984年   3199篇
  1983年   2561篇
  1982年   2827篇
  1981年   2703篇
  1980年   2503篇
  1979年   2719篇
  1978年   2835篇
  1977年   2856篇
  1976年   2833篇
  1975年   2687篇
  1974年   2665篇
  1973年   2811篇
  1972年   1875篇
  1967年   1830篇
排序方式: 共有10000条查询结果,搜索用时 312 毫秒
51.
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   
52.
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   
53.
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   
54.
55.

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   
56.
Russian Physics Journal - The article describes the collocation method for the numerical solution of mathematical physics boundary value problems. By arranging the collocation nodes in a special...  相似文献   
57.
Crystallography Reports - The specific features of the formation of concentration inhomogeneities in crystals grown by the Czochralski method (GaSb:Te, Ge:Ga) and by the Bridgman method...  相似文献   
58.
Crystallography Reports - The studies of wide-gap semiconductor materials using electron-beam induced current (EBIC) method are reviewed. The main methods for measuring the diffusion length of...  相似文献   
59.
Vorob’ev  N. T.  Lantsetova  E. D. 《Mathematical Notes》2021,110(5-6):655-665
Mathematical Notes - It is proved that the lattice of all Fitting classes of finite groups is not distributive, and conditions under which Fitting classes satisfy the distributive and modular laws...  相似文献   
60.
Journal of Applied Spectroscopy - Aqueous solutions of human hemoglobin have been studied by the multi-angle static light scattering method. The tendency of sickle-shaped erythrocytes to aggregate...  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