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   529683篇
  免费   3587篇
  国内免费   1109篇
化学   241921篇
晶体学   7697篇
力学   30104篇
综合类   3篇
数学   81265篇
物理学   173389篇
  2020年   4567篇
  2019年   5435篇
  2018年   12667篇
  2017年   13027篇
  2016年   12707篇
  2015年   5660篇
  2014年   9567篇
  2013年   20068篇
  2012年   18437篇
  2011年   26427篇
  2010年   18865篇
  2009年   19106篇
  2008年   24146篇
  2007年   26295篇
  2006年   16336篇
  2005年   17618篇
  2004年   15191篇
  2003年   14433篇
  2002年   13477篇
  2001年   13239篇
  2000年   10508篇
  1999年   7807篇
  1998年   7018篇
  1997年   6827篇
  1996年   6503篇
  1995年   5780篇
  1994年   5754篇
  1993年   5853篇
  1992年   6024篇
  1991年   6459篇
  1990年   6248篇
  1989年   6211篇
  1988年   5986篇
  1987年   5951篇
  1986年   5536篇
  1985年   6958篇
  1984年   7421篇
  1983年   6105篇
  1982年   6498篇
  1981年   6061篇
  1980年   5757篇
  1979年   6253篇
  1978年   6472篇
  1977年   6420篇
  1976年   6586篇
  1975年   6061篇
  1974年   5946篇
  1973年   6196篇
  1972年   4794篇
  1971年   4191篇
排序方式: 共有10000条查询结果,搜索用时 546 毫秒
991.
The deformed quantum Calogero-Moser-Sutherland problems related to the root systems of the contragredient Lie superalgebras are introduced. The construction is based on the notion of the generalized root systems suggested by V. Serganova. For the classical series a recurrent formula for the quantum integrals is found, which implies the integrability of these problems. The corresponding algebras of the quantum integrals are investigated, the explicit formulas for their Poincare series for generic values of the deformation parameter are presented.  相似文献   
992.
Journal of Statistical Physics - We study high-energy asymptotics of the steady velocity distributions for model kinetic equations describing various regimes in dilute granular flows. The main...  相似文献   
993.
The kinetics of formation and relaxation of transient holographic gratings recorded in a system of saturable three-level centers is studied. Distortions in the shape of the profile of recorded and decaying structures of population and of the refractive index are taken into account. The analysis of the time dependences of diffraction efficiencies of different orders is performed for phase (thermal) and amplitude (concentration) gratings.  相似文献   
994.
995.
996.
A sequential scheme for calculating the polarizability of a pair of parallel cylinders with an arbitrary (but fairly symmetric) form is suggested. An infinite set of algebraic equations is derived for coefficients involved in an expression for the potential. The numerical solution of this set makes it possible to find the polarizability with any degree of accuracy. This method is unrelated to the cylinder shape. The electrostatic properties of the cylinders are described in terms of the multipolar polarizability matrix.  相似文献   
997.
The structure of bis-(2,3-pentamethylene-3,4-dihydro-4-oxoquinazolinium) tetrachlorocuprate (II) sesquihydrate, (C13H15N2O)2[CuCl4]·1.5H2O, was determined by single crystal X-ray diffraction. In contrast to the previously studied analogs, the compound contains crystallization water molecules.Original Russian Text Copyright © 2004 by K. K. Turgunov, B. Tashkhodzhaev, L. V. Molchanov, and Kh. M. Shakhidoyatov__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 5, pp. 955–959, September–October, 2004.  相似文献   
998.
Hexaphyrin(1.0.1.0.0.0) (isoamethyrin) undergoes a significant color change in the presence of UO22+, PuO22+, and NpO22+. The complexation of the first of these dioxo actinide cations was studied in semi-quantitative fashion in 1:1 MeOH-CH2Cl2. Under these conditions, the detection limit for UO22+ was found to be ca. 5.8 ppm by naked eye monitoring and <28 ppb by UV-vis spectroscopy. Isoamethyrin does not undergo a color change in the presence of most transition metals or when exposed to Gd(III). Isoamethyrin thus constitutes an attractive alternative to 2,2′(1,8-dihydroxy-3,6-disulfonaphthylene-2,7-bisazo)-bisbenzenarsonic acid (AzIII) and 2-(5-bromo-2-pyridylazo)-5-(diethylamino)phenol (BrPADAP), systems currently used as actinide cation sensors.  相似文献   
999.
1000.
Mechatronic subsystems have been extensively developed in automotive applications as they increase performance compared to passive components. The Hydractive CRONE suspension based on fractional differentiation is presented as a hybrid system undergoing an infinite sequence of autonomous switchings. The modelling and operation of Hydractive CRONE suspension as a hybrid system are presented. The stability of Hydractive CRONE suspension is demonstrated using the maximum principle extended to hybrid systems. Finally, comfort mode synthesis is proposed using the third generation CRONE control system design.  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