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   472308篇
  免费   5831篇
  国内免费   1568篇
化学   248132篇
晶体学   6762篇
力学   20666篇
综合类   25篇
数学   60881篇
物理学   143241篇
  2021年   3851篇
  2020年   4312篇
  2019年   4644篇
  2018年   7573篇
  2017年   7706篇
  2016年   9840篇
  2015年   6306篇
  2014年   9197篇
  2013年   21236篇
  2012年   19020篇
  2011年   21924篇
  2010年   15099篇
  2009年   14767篇
  2008年   18550篇
  2007年   18540篇
  2006年   17257篇
  2005年   20159篇
  2004年   18688篇
  2003年   14956篇
  2002年   12471篇
  2001年   13710篇
  2000年   10243篇
  1999年   8104篇
  1998年   6713篇
  1997年   6456篇
  1996年   6242篇
  1995年   5603篇
  1994年   5498篇
  1993年   5308篇
  1992年   6011篇
  1991年   6085篇
  1990年   5841篇
  1989年   5591篇
  1988年   5601篇
  1987年   5471篇
  1986年   5190篇
  1985年   6679篇
  1984年   6802篇
  1983年   5380篇
  1982年   5481篇
  1981年   5465篇
  1980年   5055篇
  1979年   5430篇
  1978年   5590篇
  1977年   5456篇
  1976年   5434篇
  1975年   4994篇
  1974年   4947篇
  1973年   4973篇
  1972年   3506篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
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   
122.
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   
123.
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   
124.
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   
125.
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   
126.
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   
127.
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   
128.
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   
129.
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   
130.
Syrovatka  R. A.  Lipaev  A. M.  Naumkin  V. N.  Klumov  B. A. 《JETP Letters》2022,116(12):869-874
JETP Letters - A quasi-two-dimensional plasma crystal in (3 + 1) dimensions has been experimentally observed for the first time; i.e., three spatial coordinates of each microparticles of the...  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