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   392707篇
  免费   3143篇
  国内免费   1250篇
化学   183338篇
晶体学   5100篇
力学   20709篇
综合类   6篇
数学   77362篇
物理学   110585篇
  2021年   2134篇
  2020年   2458篇
  2019年   2732篇
  2018年   19103篇
  2017年   19555篇
  2016年   13290篇
  2015年   4468篇
  2014年   4958篇
  2013年   11342篇
  2012年   15205篇
  2011年   29273篇
  2010年   17611篇
  2009年   17874篇
  2008年   24255篇
  2007年   29069篇
  2006年   9863篇
  2005年   15631篇
  2004年   11955篇
  2003年   11697篇
  2002年   8870篇
  2001年   6737篇
  2000年   5664篇
  1999年   4005篇
  1998年   3544篇
  1997年   3543篇
  1996年   3601篇
  1995年   2863篇
  1994年   2874篇
  1993年   2921篇
  1992年   3031篇
  1991年   3038篇
  1990年   2910篇
  1989年   2888篇
  1988年   2831篇
  1987年   2790篇
  1986年   2690篇
  1985年   3553篇
  1984年   3688篇
  1983年   2946篇
  1982年   3283篇
  1981年   3174篇
  1980年   2937篇
  1979年   3145篇
  1978年   3247篇
  1977年   3151篇
  1976年   3126篇
  1975年   2990篇
  1974年   2967篇
  1973年   3170篇
  1972年   2054篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
81.
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   
82.
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   
83.
84.

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   
85.
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   
86.
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   
87.
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   
88.
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   
89.
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   
90.
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