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   368684篇
  免费   2242篇
  国内免费   1097篇
化学   166328篇
晶体学   4974篇
力学   20171篇
综合类   6篇
数学   74126篇
物理学   106418篇
  2020年   2042篇
  2019年   2335篇
  2018年   18920篇
  2017年   19346篇
  2016年   12701篇
  2015年   3861篇
  2014年   4309篇
  2013年   10000篇
  2012年   13803篇
  2011年   27564篇
  2010年   16793篇
  2009年   17161篇
  2008年   22749篇
  2007年   27592篇
  2006年   8362篇
  2005年   14222篇
  2004年   10717篇
  2003年   10664篇
  2002年   7941篇
  2001年   6409篇
  2000年   5337篇
  1999年   3725篇
  1998年   3324篇
  1997年   3286篇
  1996年   3260篇
  1995年   2611篇
  1994年   2647篇
  1993年   2705篇
  1992年   2796篇
  1991年   2852篇
  1990年   2753篇
  1989年   2723篇
  1988年   2669篇
  1987年   2640篇
  1986年   2544篇
  1985年   3268篇
  1984年   3448篇
  1983年   2778篇
  1982年   3056篇
  1981年   2948篇
  1980年   2757篇
  1979年   2951篇
  1978年   3084篇
  1977年   2995篇
  1976年   3008篇
  1975年   2854篇
  1974年   2823篇
  1973年   3016篇
  1972年   1975篇
  1967年   1906篇
排序方式: 共有10000条查询结果,搜索用时 781 毫秒
71.
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   
72.
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   
73.
74.

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   
75.
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   
76.
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   
77.
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   
78.
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   
79.
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   
80.
Russian Journal of Organic Chemistry - A procedure has been proposed for the synthesis of a series of substituted N-(1,3-thiazol-2-yl)-pyrimidin-2-amines and N-(pyrimidin-2-yl)thioureas by...  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