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   330134篇
  免费   3389篇
  国内免费   934篇
化学   165091篇
晶体学   5375篇
力学   15597篇
综合类   7篇
数学   38512篇
物理学   109875篇
  2021年   3149篇
  2020年   3347篇
  2019年   3773篇
  2018年   5214篇
  2017年   5454篇
  2016年   7402篇
  2015年   4162篇
  2014年   7048篇
  2013年   15932篇
  2012年   12409篇
  2011年   14857篇
  2010年   11048篇
  2009年   10945篇
  2008年   13259篇
  2007年   13215篇
  2006年   12159篇
  2005年   10541篇
  2004年   9855篇
  2003年   8704篇
  2002年   8687篇
  2001年   10401篇
  2000年   7663篇
  1999年   5975篇
  1998年   4977篇
  1997年   4812篇
  1996年   4483篇
  1995年   3871篇
  1994年   3825篇
  1993年   3706篇
  1992年   4098篇
  1991年   4308篇
  1990年   4096篇
  1989年   4009篇
  1988年   3780篇
  1987年   3919篇
  1986年   3685篇
  1985年   4629篇
  1984年   4682篇
  1983年   3885篇
  1982年   3973篇
  1981年   3697篇
  1980年   3650篇
  1979年   3913篇
  1978年   3902篇
  1977年   3906篇
  1976年   3882篇
  1975年   3678篇
  1974年   3615篇
  1973年   3652篇
  1972年   2603篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
Experimental data on the effect of thallium and sodium impurities on the lattice heat conductivity of PbTe at room temperature are reported. Because the lattice of lead chalcogenides is strongly polarized near charged impurities, the effect of impurities on the lattice heat conductivity depends substantially on their charge state. This property of the material has been used to determine the charge state of the thallium impurity in PbTe. The results obtained argue for a model of quasi-local thallium-impurity states which assumes low electron-correlation energy at an impurity center. Fiz. Tverd. Tela (St. Petersburg) 40, 1206–1208 (July 1998)  相似文献   
62.
The investigation of the 1s HFS provides a good possibility for testing QED effects in a combination of a strong electric and magnetic field. Here, we report about the laserspectroscopic measurements of the ground state hyperfine splitting in 207Pb81+. To handle this M1-transition in the infrared optical regime with its long lifetime, we developed a new detection technique using a bunched ion beam. For the observation of fluorescence light, a new mirror system is adapted to the emission characteristics from an ion beam at relativistic velocities. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   
63.
64.
65.
66.
We have recently demonstrated that polarization transfer using an adiabatic passage through the Hartmann-Hahn condition (APHH-CP) by a variation of the radio-frequency amplitude can substantially improve the transfer efficiency over Hartmann-Hahn cross polarization. Here we show that APHH-CP can be combined with fast magic angle sample spinning (MAS). The heteronuclear dipolar order, established in the course of the transfer, can indeed be created and preserved.  相似文献   
67.
The Thoms effect observed with water-soluble cationic copolymer of acrylamide was studied in relation to the concentration, molecular weight, and molecular weight polydispersity of the polymeric additive, with its composition and composition polydispersity being constant.  相似文献   
68.
69.
New lower bounds for probabilities of large deviations of tests and estimators are proposed. These bounds cover the cases of moderate and Cramér-type large deviations. Bibliography: 12 titles. Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 216, 1994, pp. 52–61. Translated by the author.  相似文献   
70.
Using a system based on non-dispersive infrared (NDIR) detectors, evolved gas analysis (EGA) was able to identify and quantify the principal volatiles produced by heating powdered samples of UK brick clays. From these results, atmospheric emissions likely to result from brick production can be predicted. In addition, EGA results for extruded brick clay test pieces are significantly different from those of powdered samples. Within an extruded brick clay body, evolved gases are contained within a pore system and evolved gas-solid phase reactions also occur. This EGA study provides further evidence on the nature of firing reactions within brick clay bodies. The qualitative and quantitative influence of heating rate — a key process condition in brick manufacture — on gas release is also outlined.Dedicated to Dr. Robert Mackenzie on the occasion of his 75th birthday  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