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   195621篇
  免费   1936篇
  国内免费   618篇
化学   108215篇
晶体学   3295篇
力学   7838篇
综合类   4篇
数学   18456篇
物理学   60367篇
  2016年   2289篇
  2015年   1702篇
  2014年   2402篇
  2013年   7856篇
  2012年   5294篇
  2011年   6655篇
  2010年   4453篇
  2009年   4388篇
  2008年   6015篇
  2007年   6184篇
  2006年   5936篇
  2005年   5435篇
  2004年   4976篇
  2003年   4441篇
  2002年   4318篇
  2001年   5794篇
  2000年   4408篇
  1999年   3522篇
  1998年   2752篇
  1997年   2789篇
  1996年   2736篇
  1995年   2523篇
  1994年   2400篇
  1993年   2300篇
  1992年   2792篇
  1991年   2678篇
  1990年   2621篇
  1989年   2647篇
  1988年   2585篇
  1987年   2595篇
  1986年   2405篇
  1985年   3276篇
  1984年   3293篇
  1983年   2720篇
  1982年   2923篇
  1981年   2852篇
  1980年   2759篇
  1979年   2904篇
  1978年   3149篇
  1977年   2962篇
  1976年   2896篇
  1975年   2764篇
  1974年   2705篇
  1973年   2720篇
  1972年   1760篇
  1971年   1468篇
  1968年   1932篇
  1967年   2132篇
  1966年   1920篇
  1965年   1497篇
排序方式: 共有10000条查询结果,搜索用时 12 毫秒
101.
We have investigated the low-lying collective states and electromagnetic transitions in 94Mo within the framework of the interacting boson model. The influence of model parameters on the energy levels and electromagnetic properties has been investigated. The analysis of the obtained results and the parameter values predict that the 23+state is the lowest mixed symmetry state with pure F = Fmax - 1 in this nucleus. The calculated results predicate that the 25+ (two-Q-phonon) mixed symmetry state is closed to the J = 2+ at 2.870 MeV in the experimental data, and the 2.965 MeV state is the lowest mixed symmetry with J = 3+.  相似文献   
102.
103.
104.
Utilization of metallic grids stacks for F.I.R filters needs a good knowledge of optical properties of each grid. We study here an experimental method in order to determine the wave's change of phase by reflection on a wire grid. We use a Perot-Fabry interferometer constituted by these grids.  相似文献   
105.
A new metastable liquid-crystalline phase BPS was observed in pure chiral compounds. The BPS is transformed reversibly from the supercooled BPI and is thermodynamically stable with respect to the BPI and metastable to the cholesteric phase. Rhombic single crystals of the BPS probably indicate a cubic lattice structure as in other BPs, but the lattice constant exhibits an anomalous temperature dependence.  相似文献   
106.
In this paper I speculate upon the potential of muon spin rotation/relaxation/resonance (μSR) for future refinement and/or exploitation at large accelerators like KAON, which might generate muon beams a hundred times more intense than today's best. Several schemes for efficient utilisation of such beams might be well worth implementing on existing muon channels. Work supported by NRC and NSERC.  相似文献   
107.
108.
Unsteady flow dynamics in doubly constricted 3D vessels have been investigated under pulsatile flow conditions for a full cycle of period T. The coupled non‐linear partial differential equations governing the mass and momentum of a viscous incompressible fluid has been numerically analyzed by a time accurate Finite Volume Scheme in an implicit Euler time marching setting. Roe's flux difference splitting of non‐linear terms and the pseudo‐compressibility technique employed in the current numerical scheme makes it robust both in space and time. Computational experiments are carried out to assess the influence of Reynolds' number and the spacing between two mild constrictions on the pressure drop across the constrictions. The study reveals that the pressure drop across a series of mild constrictions can get physiologically critical and is also found to be sensitive both to the spacing between the constrictions and the oscillatory nature of the inflow profile. The flow separation zone on the downstream constriction is seen to detach from the diverging wall of the constriction leading to vortex shedding with 3D features earlier than that on the wall in the spacing between the two constrictions. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   
109.
110.
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