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   529030篇
  免费   4905篇
  国内免费   1324篇
化学   278057篇
晶体学   8119篇
力学   25730篇
综合类   24篇
数学   61864篇
物理学   161465篇
  2020年   4399篇
  2019年   5022篇
  2018年   6850篇
  2017年   6839篇
  2016年   9942篇
  2015年   5633篇
  2014年   9332篇
  2013年   22300篇
  2012年   16793篇
  2011年   20503篇
  2010年   15029篇
  2009年   14988篇
  2008年   19129篇
  2007年   19302篇
  2006年   17728篇
  2005年   15985篇
  2004年   14652篇
  2003年   13226篇
  2002年   13201篇
  2001年   14465篇
  2000年   11116篇
  1999年   8649篇
  1998年   7465篇
  1997年   7504篇
  1996年   6970篇
  1995年   6390篇
  1994年   6554篇
  1993年   6133篇
  1992年   7025篇
  1991年   7125篇
  1990年   6845篇
  1989年   6787篇
  1988年   6753篇
  1987年   6587篇
  1986年   6253篇
  1985年   8243篇
  1984年   8639篇
  1983年   7209篇
  1982年   7413篇
  1981年   7240篇
  1980年   6992篇
  1979年   7342篇
  1978年   7761篇
  1977年   7709篇
  1976年   7742篇
  1975年   7267篇
  1974年   7305篇
  1973年   7509篇
  1972年   5363篇
  1971年   4690篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
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   
142.
ABSTRACT

The authors present the results of an investigation in Fe–Ni-Cr austenitic alloys of the low-temperature deformation-induced segregations of nickel that form in the micro regions being (i) located close to grain- and subgrain boundaries and (ii) characteristic of the concentration and magnetic inhomogeneities indicated by the appearance of a dark diffraction contrast at the electron diffraction patterns taken from these regions typical (at the same time) of an enhanced value of Curie temperature. The observed effects were connected with the micro distortions caused by the local change of lattice parameter because of an increase in nickel concentration, as well as in the result of a magnetostriction dilatation. Using methods of the X-ray energy dispersive spectroscopy (XEDS) and atomic-probe body-section radiography (tomography – APT) has made it possible to determine the borders of those regions of austenite that were characteristic of an enhanced concentration of nickel in the fields of the localisation of a deformation-induced segregation of nickel in the vicinity of grain (subgrain) boundaries of austenitic alloys of the types Fe–13Cr–30Ni and Fe–37Ni–3Ti.  相似文献   
143.
144.
145.
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   
146.
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   
147.
Journal of Experimental and Theoretical Physics - The nature of the training effect in exchange-biased compounds is studied. This effect consists in a decrease in the exchange bias field (HEB)...  相似文献   
148.
149.
Journal of Thermal Analysis and Calorimetry - Novel porous carbon sheets were developed as green, renewable, cost-effective, and efficient flame retardant material for thermoplastic polymers....  相似文献   
150.
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   
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