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   234457篇
  免费   2891篇
  国内免费   516篇
化学   129030篇
晶体学   3797篇
力学   8706篇
综合类   11篇
数学   25012篇
物理学   71308篇
  2020年   2156篇
  2019年   2202篇
  2018年   2608篇
  2017年   2697篇
  2016年   4359篇
  2015年   2879篇
  2014年   4337篇
  2013年   10830篇
  2012年   7822篇
  2011年   9597篇
  2010年   6559篇
  2009年   6346篇
  2008年   8729篇
  2007年   8577篇
  2006年   8022篇
  2005年   7240篇
  2004年   6486篇
  2003年   5873篇
  2002年   5605篇
  2001年   6717篇
  2000年   5189篇
  1999年   3894篇
  1998年   3094篇
  1997年   3023篇
  1996年   3024篇
  1995年   2822篇
  1994年   2737篇
  1993年   2655篇
  1992年   3225篇
  1991年   3044篇
  1990年   2991篇
  1989年   2973篇
  1988年   3011篇
  1987年   3008篇
  1986年   2858篇
  1985年   3710篇
  1984年   3703篇
  1983年   2961篇
  1982年   3085篇
  1981年   3163篇
  1980年   2889篇
  1979年   3181篇
  1978年   3209篇
  1977年   3313篇
  1976年   3103篇
  1975年   2828篇
  1974年   2761篇
  1973年   2723篇
  1972年   1842篇
  1968年   1858篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
191.
Time-dependent reorientations of resorcinol-based acridinidione (ADR) dyes in glycerol were studied using steady-state and time-resolved fluorescence studies. The difference between fluorescence anisotropy decays recorded at 460 nm when exciting at 250 nm and those obtained when exciting at 394 nm are reported. When exciting at 394 nm, the fluorescence anisotropy decay is bi-exponential, while on exciting at 250 nm a mono-exponential fluorescence anisotropy decay is observed. We interpret this in terms of different directions of the absorption dipole at 394 and 250 nm with the emission dipole respectively, which is experimentally validated and further analysed as a prolate model of ellipsoid.  相似文献   
192.
The recently proposed Harbola–Sahni local potential in its exchange-only version [Phys. Rev. Lett. 62 , 689 (1989)] is found to give the static dipole and quadrupole polarizabilities for the Neisoelectronic series in excellent agreement with the corresponding Hartree–Fock estimates. © 1992 John Wiley & Sons, Inc.  相似文献   
193.
    
Summary Flow injection analysis associated with a gradient mixing technique can be used for the determination of free acidity and total acidity (sum of free and bonded hydrogen ions) in a few microliters by reaction with suitable acid/base indicators and UV/VIS-detection. A rapid analysis of the two parameters in single raindrops in dependence on their size is possible [1].  相似文献   
194.
Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 3, pp. 87–91, May–June, 1991.  相似文献   
195.
The NA22 data onπ ? π ? correlations are analyzed in terms of a number of two- and three-dimensional parametrizations (Gaussian space-time, Goldhaber, Bowler string-like, Bertsch hydrodynamical, Kopylov-Podgoretskii, etc.). Contrary to the results obtained for e+e? andµp collisions, the Goldhaber parametrization, as well as string-like models, fail in describing the hadron-hadron data. Better fits are obtained in the framework of surface-emitting fireball-like models, both when including and excluding hydrodynamical expansion of nuclear matter. Our results indicate that pion radiation occurs at earlier stages of matter evolution than in nuclear collisions.  相似文献   
196.
Institute of High-Molecular-Weight Compounds, Russian Academy of Sciences. Leningrad State University Translated from Zhurnal Strukturnoi Khimii, Vol. 33, No. 5, pp. 20–27, September–October, 1992.  相似文献   
197.
The leading logarithmic corrections to the critical behavior of a dilute uniaxial (Ising) ferromagnet in the disordered phase are derived using renormalization group methods. The values of the exponents in the logarithmic terms differ from those given by previous authors.  相似文献   
198.
199.
Electrochemical oxidation of thio/carbohydrazide and their hydrazone derivatives Benzaldehyde thiocarbohydrazone [BTCH] diacetylene thiocarbohydrazone [DATCH] have been studied in Brit-ton Robinson buffer in aqueous and nonaqueous media at a glassy carbon electrode. The effects of pH, sweep rate, concentration, temperature and surfactants have been studied. The complex bis (carbo/thiocabohydrazide) Zn(II) chloride was also subjected to voltammetric analysis in order to understand the reactivity both in free and metal bound states. The reaction conditions were optimized for the determination of above compounds in micrograms quantities by differential pulse voltammetry, analytical utility of this investigation is also highlighted.  相似文献   
200.
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