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   205688篇
  免费   1545篇
  国内免费   431篇
化学   106728篇
晶体学   3350篇
力学   10331篇
综合类   10篇
数学   21988篇
物理学   65257篇
  2021年   1988篇
  2020年   2055篇
  2019年   2610篇
  2018年   3695篇
  2017年   3691篇
  2016年   4854篇
  2015年   2392篇
  2014年   4362篇
  2013年   8720篇
  2012年   6966篇
  2011年   8207篇
  2010年   6560篇
  2009年   6744篇
  2008年   7799篇
  2007年   7777篇
  2006年   6871篇
  2005年   6045篇
  2004年   5747篇
  2003年   5279篇
  2002年   5275篇
  2001年   5695篇
  2000年   4250篇
  1999年   3196篇
  1998年   2742篇
  1997年   2801篇
  1996年   2579篇
  1995年   2247篇
  1994年   2367篇
  1993年   2278篇
  1992年   2565篇
  1991年   2686篇
  1990年   2583篇
  1989年   2665篇
  1988年   2573篇
  1987年   2585篇
  1986年   2443篇
  1985年   3076篇
  1984年   3150篇
  1983年   2642篇
  1982年   2605篇
  1981年   2556篇
  1980年   2363篇
  1979年   2752篇
  1978年   2708篇
  1977年   2898篇
  1976年   2868篇
  1975年   2670篇
  1974年   2613篇
  1973年   2705篇
  1972年   2086篇
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
71.
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   
72.
73.
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   
74.
75.
Journal of Radioanalytical and Nuclear Chemistry - Extraction chromatography flow-sheet employing octyl(phenyl)-N,N-diisobutylcarbonoylmethylphosphine oxide and bis(2-ethylhexyl) hydrogen phosphate...  相似文献   
76.
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   
77.
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   
78.
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   
79.
80.
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