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   203707篇
  免费   1459篇
  国内免费   429篇
化学   105230篇
晶体学   3398篇
力学   10310篇
综合类   10篇
数学   21961篇
物理学   64686篇
  2021年   1981篇
  2020年   2013篇
  2019年   2584篇
  2018年   3664篇
  2017年   3676篇
  2016年   4823篇
  2015年   2357篇
  2014年   4317篇
  2013年   8605篇
  2012年   6886篇
  2011年   8079篇
  2010年   6482篇
  2009年   6657篇
  2008年   7668篇
  2007年   7622篇
  2006年   6734篇
  2005年   5953篇
  2004年   5666篇
  2003年   5182篇
  2002年   5181篇
  2001年   5623篇
  2000年   4159篇
  1999年   3139篇
  1998年   2711篇
  1997年   2766篇
  1996年   2555篇
  1995年   2224篇
  1994年   2345篇
  1993年   2236篇
  1992年   2528篇
  1991年   2655篇
  1990年   2557篇
  1989年   2632篇
  1988年   2543篇
  1987年   2556篇
  1986年   2427篇
  1985年   3041篇
  1984年   3118篇
  1983年   2612篇
  1982年   2574篇
  1981年   2541篇
  1980年   2342篇
  1979年   2715篇
  1978年   2680篇
  1977年   2881篇
  1976年   2888篇
  1975年   2678篇
  1974年   2611篇
  1973年   2716篇
  1972年   2088篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
We present theoretical studies of the temperature and magnetic field dependences of the Coulomb drag transresistivity between two parallel layers of two-dimensional electron gases in the quantum Hall regime near half-filling of the lowest Landau level. It is shown that Fermi-liquid interactions between the relevant quasi-particles can significantly affect the transresistivity, providing its independence of the interlayer spacing for spacings that take values reported in the experiments. The obtained results agree with the experimental evidence.  相似文献   
992.
An analysis of the preferable fission path manifesting itself as a fine structure of the total kinetic energy-mass distribution of the fission fragments compelled us to put forward an absolutely new shape of the fissioning system on the descent from the fission barrier. It is a multicomponent nuclear molecule constituted by two magic clusters and a torus-like neck between.  相似文献   
993.
Physics of Atomic Nuclei - The results of various experiments that measured a single-spin asymmetry in inclusive pion production are analyzed in the energy range between 13 and 200 GeV. The...  相似文献   
994.
The catalytic activity of three groups of acid catalysts different in the nature and strength of acid sites in the skeletal isomerization of n-butane was studied. It was found that the strength of the sites did not correlate with the rate of the reaction.  相似文献   
995.
We investigate necessary and sufficient conditions under which one estimate of exponential type is valid for large deviation probabilities of sums of independent identically distributed random variables. Bibliography: 3 titles.  相似文献   
996.
Experimental data obtained by studying the effect of internal waves with known space-time parameters on the propagation of a 240-Hz tone signal and on the space-time interference structure of the sound field generated by a noiselike sound source are presented.  相似文献   
997.
The behavior of inorganic macrocomponents (Fe3 +, Fe2 +, Cu2 +, and Cl-) and organic additives (judged from the relative concentration of total carbon) in regeneration and reuse of spent etching solutions used in fabrication of copper type-plates was studied. The conditions of electrochemical and sorption stages of the regeneration process were discussed.  相似文献   
998.
999.
The influence of the sequence of Cu and Pd introduction into zeolite matrice when preparing Cu, Pd-zeolite catalysts on their acidity and degree of metal reduction was studied. The mutual influence of Cu and Pd on their reducibility was analyzed. The selectivity of Cu, Pd-zeolite catalysts in conversion of synthesis gas to different products was elucidated.  相似文献   
1000.
N. Elgun  E. A. Davis 《Journal of Non》2003,330(1-3):226-233
Hydrogenated amorphous GaP films have been prepared by reactive rf sputtering. Infrared spectroscopy, optical transmission and reflection, photothermal deflection spectroscopy and dc conductivity have been studied to investigate the local bonding configurations, the optical absorption edges and the temperature dependence of the conductivity as a function of hydrogen content. The results are discussed and compared with the effects of hydrogenation on amorphous Si.  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