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   219542篇
  免费   1875篇
  国内免费   654篇
化学   120216篇
晶体学   3305篇
力学   8491篇
综合类   6篇
数学   24199篇
物理学   65854篇
  2020年   2016篇
  2019年   2305篇
  2018年   3236篇
  2017年   3149篇
  2016年   4333篇
  2015年   2427篇
  2014年   3897篇
  2013年   9466篇
  2012年   7062篇
  2011年   8680篇
  2010年   6189篇
  2009年   6014篇
  2008年   8324篇
  2007年   8388篇
  2006年   7829篇
  2005年   7137篇
  2004年   6299篇
  2003年   5780篇
  2002年   5619篇
  2001年   6039篇
  2000年   4789篇
  1999年   3530篇
  1998年   3052篇
  1997年   3086篇
  1996年   2901篇
  1995年   2385篇
  1994年   2505篇
  1993年   2545篇
  1992年   2675篇
  1991年   2742篇
  1990年   2628篇
  1989年   2610篇
  1988年   2512篇
  1987年   2496篇
  1986年   2402篇
  1985年   3123篇
  1984年   3264篇
  1983年   2600篇
  1982年   2896篇
  1981年   2756篇
  1980年   2558篇
  1979年   2779篇
  1978年   2894篇
  1977年   2906篇
  1976年   2890篇
  1975年   2739篇
  1974年   2725篇
  1973年   2905篇
  1972年   1908篇
  1967年   1848篇
排序方式: 共有10000条查询结果,搜索用时 31 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