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   699077篇
  免费   7059篇
  国内免费   2127篇
化学   346550篇
晶体学   9582篇
力学   34870篇
综合类   19篇
数学   112704篇
物理学   204538篇
  2021年   4836篇
  2020年   5439篇
  2019年   5967篇
  2018年   21016篇
  2017年   21133篇
  2016年   18582篇
  2015年   8228篇
  2014年   11273篇
  2013年   26775篇
  2012年   25405篇
  2011年   39768篇
  2010年   26073篇
  2009年   26266篇
  2008年   34245篇
  2007年   37919篇
  2006年   21530篇
  2005年   24225篇
  2004年   20826篇
  2003年   19369篇
  2002年   17152篇
  2001年   17263篇
  2000年   13490篇
  1999年   10307篇
  1998年   8727篇
  1997年   8467篇
  1996年   8261篇
  1995年   7190篇
  1994年   7133篇
  1993年   7027篇
  1992年   7677篇
  1991年   7838篇
  1990年   7450篇
  1989年   7282篇
  1988年   7317篇
  1987年   7161篇
  1986年   6806篇
  1985年   8829篇
  1984年   9107篇
  1983年   7252篇
  1982年   7543篇
  1981年   7410篇
  1980年   6927篇
  1979年   7461篇
  1978年   7752篇
  1977年   7475篇
  1976年   7443篇
  1975年   6921篇
  1974年   6890篇
  1973年   7050篇
  1972年   4873篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
Azepane rings have been constructed diastereoselectively upon a carbohydrate derivative utilising reductive amination and RCM. The stereochemistry of the ring junctions was confirmed by X-ray crystallography and NMR. Diastereoselective dihydroxylation has also been employed to afford a tetrahydroxylated azepane carbohydrate derivative with potential biological activity.  相似文献   
982.
Summary Literature data on the radiolytic generation of hydrogen in nitric acid solutions of plutonium are used to construct a model that predicts G(H2) as a function of the nitric acid and plutonium concentrations. The model indicates that G(H2) decreases with increasing concentration of nitric acid, in agreement with most experimental observations. The effect of the plutonium concentration on G(H2) is secondary to the effect of the acid concentration. An equation for interpolating Gvalues for total gas is included.  相似文献   
983.
984.
985.
We report the recent development on the SUSY calculations with the help of GRACE system. GRACE/SUSY/1LOOP is the computer code which can generate Feynman diagrams in the MSSM automatically and compute one-loop amplitudes in the numerical way. We present new results of various two-body decay widths and chargino pair production at ILC (international linear collider) at one-loop level.   相似文献   
986.
The vibrational dynamics of protein folding is analyzed in the framework of Tsallis statistics. We employ exact expressions for classical harmonic oscillators by considering the unnormalized constraints. As q→1, we show that these approximations agree with the result of Gaussian network model.  相似文献   
987.
Experimental study of low-frequency dynamics of an intracavity frequency-doubled Nd:YAG laser demonstrates the influence of the interaction of orthogonally polarized modes, participating in frequency doubling (type II phase matching), on the stability of the laser output. At a sufficiently low pump rate and low conversion efficiency, the laser shows stable operation with a low noise level at the frequencies of relaxation oscillations. At a high pump power and/or a high conversion efficiency, the laser emission becomes unstable as a result of Hopf bifurcation at the frequencies of relaxation oscillations that are responsible for the anti-phase polarization dynamics of the laser.  相似文献   
988.
B. Roessli  P. Böni 《Pramana》2004,63(1):125-132
A brief account of applications of polarized inelastic neutron scattering in condensed matter research is given. We show that full polarization analysis is the only tool allowing to discriminate unambiguously between different magnetic modes in various magnetic materials. We show by means of recent results in the Heisenberg ferromagnet EuS that the effects of dipolar interactions can be studied on a microscopic scale. Moreover, we have found for the first time indications for the divergence of the longitudinal fluctuations belowT c. In the itinerant antiferromagnet chromium we demonstrate that the dynamics of the longitudinal and transverse excitations are very different, resolving a long standing puzzle concerning the slope of their dispersion. Finally, we show that a measurement of the polarization-dependent part of the cross section of non-centrosymmetric MnSi proves directly that the chirality of the magnetic fluctuations is left-handed.  相似文献   
989.
    
Ohne Zusammenfassung  相似文献   
990.
    
Ohne Zusammenfassung  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