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   473890篇
  免费   6182篇
  国内免费   1505篇
化学   251212篇
晶体学   6809篇
力学   20268篇
综合类   26篇
数学   61380篇
物理学   141882篇
  2021年   3913篇
  2020年   4455篇
  2019年   4774篇
  2018年   7313篇
  2017年   7379篇
  2016年   10114篇
  2015年   6521篇
  2014年   9457篇
  2013年   21798篇
  2012年   19217篇
  2011年   22176篇
  2010年   15337篇
  2009年   14993篇
  2008年   18927篇
  2007年   18868篇
  2006年   17516篇
  2005年   19158篇
  2004年   17570篇
  2003年   14405篇
  2002年   12541篇
  2001年   13847篇
  2000年   10421篇
  1999年   8206篇
  1998年   6791篇
  1997年   6505篇
  1996年   6320篇
  1995年   5638篇
  1994年   5588篇
  1993年   5359篇
  1992年   6079篇
  1991年   6137篇
  1990年   5868篇
  1989年   5642篇
  1988年   5663篇
  1987年   5516篇
  1986年   5212篇
  1985年   6709篇
  1984年   6839篇
  1983年   5396篇
  1982年   5484篇
  1981年   5476篇
  1980年   5070篇
  1979年   5443篇
  1978年   5573篇
  1977年   5474篇
  1976年   5437篇
  1975年   5005篇
  1974年   4957篇
  1973年   4972篇
  1972年   3514篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
Journal of Analytical Chemistry - Studies on the separation of the Se and Te trace components from Co, Ni, Cu, Fe, Cr, Mo, and W macrocomponents for their determination by inductively coupled...  相似文献   
132.
ABSTRACT

By applying the geometric models and the theoretical equation, the surface tension, the molar volume and the density were studied. The empirical calculations were carried out in temperature range 623?K?≤?T?≤?1123?K. Only few thermophysical properties were estimated for eight quinary alloys: Sn3.55Ag0.5Cu3Bi3Sb, Sn3.48Ag0.5Cu3Bi5Sb, Sn3.48 Ag0.5Cu5Bi3Sb, Sn3.40 Ag0.5Cu5Bi5Sb, Sn3.53Ag1Cu3Bi3Sb, Sn3.46Ag1Cu3Bi5Sb, Sn3.46Ag1Cu5Bi3Sb, Sn3.38Ag1Cu5Bi5Sb. The results show that surface tension and density have a linear appearance for all temperatures. We have also studied the influence of the composition and temperature in the studied alloys. The obtained theoretical results are compared with the experimental ones and with the conventional Pb–Sn welds.  相似文献   
133.
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   
134.
Echabaane  M.  Hfaiedh  S.  Smiri  B.  Saidi  F.  Dridi  C. 《Journal of Solid State Electrochemistry》2021,25(6):1797-1806
Journal of Solid State Electrochemistry - The fast and sensitive detection of copper ions would be essential for water monitoring. Herein, we report a novel development of an impedimetric sensor...  相似文献   
135.
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   
136.
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   
137.
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   
138.
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   
139.
Differential Equations - We consider an initial–boundary value problem for the heat equation in which the heat conduction coefficient and one of the functions occurring in the source depend...  相似文献   
140.
Russian Journal of Organic Chemistry - Methyl (Z)-3-[(2R,3R,4S,5S)-5-(2-methoxy-2-oxoethyl)-3,4-(isopropylidenedioxy)tetrahydrofuran-2-yl]-prop-2-enoate was synthesized, and its intramolecular...  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