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   83787篇
  免费   711篇
  国内免费   129篇
化学   45015篇
晶体学   1318篇
力学   3421篇
综合类   1篇
数学   8572篇
物理学   26300篇
  2021年   924篇
  2020年   1031篇
  2019年   1163篇
  2018年   1650篇
  2017年   1729篇
  2016年   2271篇
  2015年   1130篇
  2014年   1834篇
  2013年   3520篇
  2012年   3141篇
  2011年   3504篇
  2010年   2774篇
  2009年   2782篇
  2008年   3204篇
  2007年   3070篇
  2006年   2974篇
  2005年   2624篇
  2004年   2385篇
  2003年   2229篇
  2002年   2283篇
  2001年   2367篇
  2000年   1758篇
  1999年   1344篇
  1998年   1211篇
  1997年   1134篇
  1996年   1004篇
  1995年   934篇
  1994年   893篇
  1993年   913篇
  1992年   953篇
  1991年   1016篇
  1990年   936篇
  1989年   987篇
  1988年   899篇
  1987年   843篇
  1986年   810篇
  1985年   982篇
  1984年   1059篇
  1983年   896篇
  1982年   926篇
  1981年   844篇
  1980年   757篇
  1979年   847篇
  1978年   964篇
  1977年   994篇
  1976年   879篇
  1975年   852篇
  1974年   840篇
  1973年   815篇
  1972年   589篇
排序方式: 共有10000条查询结果,搜索用时 484 毫秒
171.
Ab initio MP2 calculations with several basis sets proved the existence of a stable benzonitrile dimer with a planar structure and a short contact between the H atom of one molecule and the N atom of another. The structure is greatly stabilized by attraction between the neighboring oppositely directed dipoles and donor-acceptor interaction between the orbital of the lone electron pair of the N′ atom and the vacant antibonding orbital localized on the C-H bond.Original Russian Text Copyright © 2004 by O. V. Sizova, E. P. Sokolova, V. I. Baranovskii, D. A. Rozmanov, and O. A. Tomashenko__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 5, pp. 807–815, September–October, 2004.  相似文献   
172.
In the paper we describe automorphisms and derivations of simple Lie algebras of family R. The Lie algebra of the automorphism group is found. Bibliography: 11 titles.__________Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 305, 2003, pp. 165–186.  相似文献   
173.
An improved procedure for modeling the operation of a light-gas gun is proposed. The motion of working bodies in both the firing chamber and the light-gas chamber is studied within the framework of the mechanics of heterogeneous media. The problem of barrel heating taking into account its melting and removal of thermal ablation products into the medium inside the bore is solved in a coupled formulation. Heat and mass transfer and friction on the barrel surface are calculated using empirical dependences. The deformable piston is considered compressible and elastoviscoplastic. Allowance is made for the presence of a clearance between the lateral surface of the piston and the barrel bore walls and the associated gas flow between the firing and the light-gas chamber. Calculation results are given.  相似文献   
174.
It is shown that the three-dimensional Navier-Stokes equation for incompressible fluid can be represented as an equation including only quaternions as co-ordinate operators and variables. Only the quaternion operations such as a quaternion product and a quaternion conjugation over these variables are used.  相似文献   
175.
Data on methods for the production of isatin and indole aldoximes, ketoximes, and amidoximes and their reactions are reviewed. Individual syntheses of new heterocycles from indole and isatin oximes are discussed. The principal results from investigation of the biological activity of derivatives of the oximes are also presented.  相似文献   
176.
The influence of ultrasonic shock treatment on variation in the pearlite structure and properties is studied in the surface layer of carburized steel. It is shown that plastic deformation results in carbon redistribution and formation of new phases.  相似文献   
177.
The PARRNe facility has been used to produce neutron-rich isotopes 83,84Gaby the ISOL method. Their decay has been studied, and β-γ coincidence and γ-γ coincidence data were collected as a function of time. The first two excited levels in 83Ge and the first excited level in 84Ge have been measured for the first time.  相似文献   
178.
Journal of Experimental and Theoretical Physics - The magnetoresistance effect in the SmCu3Mn4O12 compound with a perovskite-like structure is investigated for the first time. It is found that an...  相似文献   
179.
180.
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