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   205237篇
  免费   1658篇
  国内免费   513篇
化学   106345篇
晶体学   3080篇
力学   10429篇
综合类   16篇
数学   22507篇
物理学   65031篇
  2021年   2066篇
  2020年   2134篇
  2019年   2677篇
  2018年   3763篇
  2017年   3746篇
  2016年   4942篇
  2015年   2451篇
  2014年   4433篇
  2013年   8841篇
  2012年   7060篇
  2011年   8297篇
  2010年   6617篇
  2009年   6788篇
  2008年   7835篇
  2007年   7778篇
  2006年   6848篇
  2005年   6088篇
  2004年   5762篇
  2003年   5276篇
  2002年   5253篇
  2001年   5669篇
  2000年   4168篇
  1999年   3172篇
  1998年   2728篇
  1997年   2786篇
  1996年   2561篇
  1995年   2233篇
  1994年   2344篇
  1993年   2237篇
  1992年   2530篇
  1991年   2654篇
  1990年   2558篇
  1989年   2629篇
  1988年   2503篇
  1987年   2508篇
  1986年   2372篇
  1985年   3000篇
  1984年   3072篇
  1983年   2585篇
  1982年   2537篇
  1981年   2509篇
  1980年   2302篇
  1979年   2689篇
  1978年   2648篇
  1977年   2857篇
  1976年   2856篇
  1975年   2649篇
  1974年   2585篇
  1973年   2695篇
  1972年   2074篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
71.
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   
72.
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   
73.
74.
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   
75.
76.
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   
77.
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   
78.
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   
79.
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   
80.
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