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   407363篇
  免费   3450篇
  国内免费   949篇
化学   189429篇
晶体学   6450篇
力学   21390篇
综合类   7篇
数学   59851篇
物理学   134635篇
  2021年   3117篇
  2020年   3329篇
  2019年   3762篇
  2018年   11918篇
  2017年   12617篇
  2016年   10500篇
  2015年   4817篇
  2014年   7122篇
  2013年   16002篇
  2012年   15762篇
  2011年   24769篇
  2010年   16808篇
  2009年   16792篇
  2008年   21813篇
  2007年   24596篇
  2006年   12304篇
  2005年   15892篇
  2004年   12517篇
  2003年   11452篇
  2002年   9859篇
  2001年   10518篇
  2000年   7932篇
  1999年   5998篇
  1998年   5002篇
  1997年   4823篇
  1996年   4645篇
  1995年   3958篇
  1994年   3904篇
  1993年   3777篇
  1992年   4159篇
  1991年   4374篇
  1990年   4167篇
  1989年   4083篇
  1988年   3862篇
  1987年   3994篇
  1986年   3756篇
  1985年   4713篇
  1984年   4777篇
  1983年   3975篇
  1982年   4055篇
  1981年   3781篇
  1980年   3734篇
  1979年   4015篇
  1978年   4016篇
  1977年   3931篇
  1976年   3940篇
  1975年   3722篇
  1974年   3663篇
  1973年   3723篇
  1972年   2638篇
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
201.
202.
The structure, chemical composition, and magnetic properties of electrochemically deposited nanocrystalline Co-Ni-Fe films were investigated using a number of techniques. A high saturation magnetic induction up to B s = 21 kG was attained. An enhancement of the saturation magnetization compared to the ideal anticipated one was revealed, which correlated with the nonlinear behavior of the structural phase composition and lattice parameters with the change of the composition. The text was submitted by the authors in English.  相似文献   
203.
Methods for phase stabilization of ammonium nitrate were sought for in order to considerably expand the application area of this oxidizing agent in various-purpose self-combustible formulations, including that in a new generation of gas-generating formulations for automobile air bags. New methods for stabilization of ammonium nitrate were studied and, in particular, a search was made for organic compounds that can stabilize ammonium nitrate even at their low content. The mechanism of phase state stabilization of ammonium nitrate by compounds of this kind was examined.  相似文献   
204.
Results from 5D induced-matter and membrane theory with null paths are extended to show that a particle obeys the 4D Klein-Gordon equation but with a variable mass. The Dirac equation also follows, but raises concerns about 4D quantization in the two natural 5D gauges, and reopens the question of a Regge-like trajectory for the spin angular momenta and squared masses of gravitationally-dominated systems.  相似文献   
205.
Kinetic, sorption and selectivity properties of commercial adsorbents are improved by adding petroleum residues (tar asphaltene concentrates) 13% of whole mass. Obtained adsorbents can be used for selective extraction of nobel metals from multicomponent polymetallic solutions of heavy metals and fro sewages purification for removing arsenic.  相似文献   
206.
Using the simplest (sinusoidal) corrugation profile in the approximation of absence of losses in the material as an example, we study the regimes of complete transformation of an incident wave to the diffraction lobe by a corrugated metal surface or a corrugated interface of two dielectric media. A numerical-intuitive pattern of appearance and evolution of such regimes with increasing corrugation amplitude is revealed. It is shown that the regimes of complete transformation of an incident wave to the diffraction lobe are possible in both the case of autocollimation and the case of a considerable deviation from it. The examination is based on a numerical method of solving the integral equation by means of a specially created interactive processing system in Visual Fortran.  相似文献   
207.
The European Physical Journal E - The isothermal gas adsorption of two hexane isomers (n-hexane and cyclohexane) in the mesopores of MCM-41 silica have been investigated by small angle neutron...  相似文献   
208.
All 3-dimensional convex polytopes are known to be rigid. Still their Minkowski differences (virtual polytopes) can be flexible with any finite freedom degree. We derive some sufficient rigidity conditions for virtual polytopes and present some examples of flexible ones. For example, Bricard's first and second flexible octahedra can be supplied by the structure of a virtual polytope.  相似文献   
209.
210.
Planar laser-induced fluorescence visualisation is used to investigate nonuniformities in the flow of a hypersonic conical nozzle. Possible causes for the nonuniformity are outlined and investigated, and the problem is shown to be due to a small step at the nozzle throat. Entrainment of cold boundary layer gas is postulated as the cause of the signal nonuniformity. PACS 47.80.Jk, 47.40.Ki, 47.60.+i  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