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   667276篇
  免费   5766篇
  国内免费   1523篇
化学   328276篇
晶体学   9600篇
力学   35678篇
综合类   19篇
数学   95832篇
物理学   205160篇
  2021年   6224篇
  2020年   6735篇
  2019年   7701篇
  2018年   10526篇
  2017年   10752篇
  2016年   14685篇
  2015年   7735篇
  2014年   13330篇
  2013年   29159篇
  2012年   22896篇
  2011年   27091篇
  2010年   20739篇
  2009年   20661篇
  2008年   25761篇
  2007年   25568篇
  2006年   23340篇
  2005年   20767篇
  2004年   19402篇
  2003年   17601篇
  2002年   17554篇
  2001年   18250篇
  2000年   14226篇
  1999年   11006篇
  1998年   9770篇
  1997年   9544篇
  1996年   8912篇
  1995年   7945篇
  1994年   8026篇
  1993年   7820篇
  1992年   8121篇
  1991年   8664篇
  1990年   8380篇
  1989年   8269篇
  1988年   7977篇
  1987年   7823篇
  1986年   7408篇
  1985年   9321篇
  1984年   9838篇
  1983年   8299篇
  1982年   8647篇
  1981年   8090篇
  1980年   7633篇
  1979年   8393篇
  1978年   8589篇
  1977年   8635篇
  1976年   8645篇
  1975年   8239篇
  1974年   8053篇
  1973年   8279篇
  1972年   6353篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
The study of the interaction between collisionless plasma flow and stagnant plasma revealed the presence of an outer boundary layer at the border of a geomagnetic trap, where the super-Alfvén subsonic laminar flow changes over to the dynamic regime characterized by the formation of accelerated magnetosonic jets and decelerated Alfvén flows with characteristic relaxation times of 10–20 min. The nonlinear interaction of fluctuations in the initial flow with the waves reflected from an obstacle explains the observed flow chaotization. The Cherenkov resonance of the magnetosonic jet with the fluctuation beats between the boundary layer and the incoming flow is the possible mechanism of its formation. In the flow reference system, the incoming particles are accelerated by the electric fields at the border of boundary layer that arise self-consistently as a result of the preceding wave-particle interactions; the inertial drift of the incoming ions in a transverse electric field increasing toward the border explains quantitatively the observed ion acceleration. The magnetosonic jets may carry away downstream up to a half of the unperturbed flow momentum, and their dynamic pressure is an order of magnitude higher than the magnetic pressure at the obstacle border. The appearance of nonequilibrium jets and the boundary-layer fluctuations are synchronized by the magnetosonic oscillations of the incoming flow at frequencies of 1–2 mHz.  相似文献   
962.
Russian Journal of Organic Chemistry -  相似文献   
963.
Thermal oxidation of polyethylene filled with dispersed copper and containing an amine antioxidant was studied. The concentration ranges in which the catalytic effect of the metal on the polymer oxidation or the stabilizing effect of the antioxidant prevails were determined. Under certain conditions, dispersed copper enhances the stabilizing effect of the antioxidant.  相似文献   
964.
 Nešetřil and Sopena introduced the concept of oriented game chromatic number. They asked whether the oriented game chromatic number of partial k-trees was bounded. Here we answer their question positively. Received: January 12, 2001 Final version received: February 25, 2002  相似文献   
965.
966.
It is a well-known feature of odd space-time dimensions d that there exist two inequivalent fundamental representations A and B of the Dirac gamma matrices. Moreover, the parity transformation swaps the fermion fields living in A and B. As a consequence, a parity-invariant Lagrangian can only be constructed by incorporating both the representations. Based upon these ideas and contrary to long-held belief, we show that in addition to a discrete exchange symmetry for the massless case, we can also define chiral symmetry provided the Lagrangian contains fields corresponding to both the inequivalent representations. We also study the transformation properties of the corresponding chiral currents under parity and charge-conjugation operations. We work explicitly in 2 + 1 dimensions and later show how some of these ideas generalize to an arbitrary number of odd dimensions.  相似文献   
967.
Evaporation of chromium ore and concentrates was studied using high-temperature differential mass-spectrometry. The data obtained, concerning the component vapor pressures in evaporation of complex oxide systems in the range 1700-2100 K, can be used to calculate the evaporation loss in melting and to assess the possibility of utilization of the sublimates formed.  相似文献   
968.
A review is given of the literature over the period from the middle of the 1950s to the beginning of the 1980s on the distribution in nature, the biological activity, the conformation, and the chemical transformations of sesquiterpenes of the caryophyllene type.  相似文献   
969.
970.
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