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   483100篇
  免费   5126篇
  国内免费   1270篇
化学   250333篇
晶体学   7061篇
力学   21574篇
综合类   15篇
数学   59563篇
物理学   150950篇
  2021年   4207篇
  2020年   4674篇
  2019年   5102篇
  2018年   7005篇
  2017年   7139篇
  2016年   10461篇
  2015年   6421篇
  2014年   9765篇
  2013年   23097篇
  2012年   18103篇
  2011年   21433篇
  2010年   15471篇
  2009年   15133篇
  2008年   19208篇
  2007年   19029篇
  2006年   17490篇
  2005年   15667篇
  2004年   14316篇
  2003年   12610篇
  2002年   12514篇
  2001年   14136篇
  2000年   10799篇
  1999年   8346篇
  1998年   7034篇
  1997年   6787篇
  1996年   6465篇
  1995年   5687篇
  1994年   5681篇
  1993年   5410篇
  1992年   6053篇
  1991年   6252篇
  1990年   5890篇
  1989年   5773篇
  1988年   5519篇
  1987年   5570篇
  1986年   5249篇
  1985年   6707篇
  1984年   6843篇
  1983年   5705篇
  1982年   5897篇
  1981年   5574篇
  1980年   5429篇
  1979年   5812篇
  1978年   5929篇
  1977年   5839篇
  1976年   5866篇
  1975年   5532篇
  1974年   5550篇
  1973年   5560篇
  1972年   3841篇
排序方式: 共有10000条查询结果,搜索用时 26 毫秒
11.
12.
Summary This paper presents some applications of cyclic voltammetry at the interface of two immiscible electrolyte solutions by means of an experimental set-up described in a former publication. When using special sample preparation good results are obtained for the determination of iodide and quinine in pharmaceutical products as well as for the determination of quinine in tonic water and dodecylsulfate in a tooth-salt.

Herrn Prof. Dr. Günther Tölg zum 60. Geburtstag gewidmet  相似文献   
13.
Crystalline materials that are transparent in the vacuum UV spectral region and currently used have been reviewed. Transmission of crystals of solid solutions with the fluorite structure Ca1?x R xF2+x (R = Sc, Y, La, Yb, Lu) in the UV and vacuum UV spectral regions has been investigated. It is shown that application of different methods of purification of fluorides from some impurities can significantly improve the optical quality of fluoride multicomponent crystals in the short-wavelength spectral region.  相似文献   
14.
15.
16.
Considering the importance of the X-ray production cross sections for the determination of the element concentrations in a given material, we have measured them experimentally for Al Si, Sc, Ti, V, Fe, Co, Ni and Cu bombarded by protons with energies ranging from 40 to 180 keV. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   
17.
We present all-atom molecular dynamics simulations ofn-hexane on the basal plane of graphite at monolayer and multilayer coverages. In keeping with experimental data, we find the presence of ordered adsorbed layers both at single monolayer coverage and when the adsorbed layer coexists with excess liquid adsorbate. Using a simulation method that does not impose any particular periodicity on the adsorbed layer, we quantitatively compare our results to the results of neutron diffraction experiments and find a structural transition from a uniaxially incommensurate lattice to a fully commensurate structure on increasing the coverage from a monolayer to a multilayer. The zig-zag backbone planes of all the alkane molecules lie parallel to the graphite surface at the multilayer coverage, while a few molecules are observed to attain the perpendicular orientation at monolayer coverage. Dedicated to Professor C N R Rao on his 70th birthday  相似文献   
18.
In this study, a novel stepwise extraction method has been examined. The guest molecules housed between the helices of the clathrate δ form of syndiotactic polystyrene can be removed completely with this method. A systematic study of the preparation of a solvent‐free mesophase (emptied clathrate) membrane, its helical and residual solvent contents, and its structural transformations has been performed. In this first attempt, an enhancement in the TTGG helical content has been observed in the extracted membrane, and a conceptual mechanism is proposed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 269–273, 2003  相似文献   
19.
20.
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