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   26484篇
  免费   606篇
  国内免费   160篇
化学   17701篇
晶体学   216篇
力学   673篇
综合类   1篇
数学   4451篇
物理学   4208篇
  2021年   175篇
  2020年   214篇
  2019年   285篇
  2018年   235篇
  2017年   208篇
  2016年   446篇
  2015年   352篇
  2014年   457篇
  2013年   1337篇
  2012年   1204篇
  2011年   1520篇
  2010年   789篇
  2009年   637篇
  2008年   1383篇
  2007年   1434篇
  2006年   1433篇
  2005年   1428篇
  2004年   1253篇
  2003年   1055篇
  2002年   1037篇
  2001年   380篇
  2000年   309篇
  1999年   251篇
  1998年   290篇
  1997年   320篇
  1996年   399篇
  1995年   309篇
  1994年   301篇
  1993年   308篇
  1992年   297篇
  1991年   244篇
  1990年   228篇
  1989年   241篇
  1988年   273篇
  1987年   255篇
  1986年   247篇
  1985年   392篇
  1984年   444篇
  1983年   332篇
  1982年   432篇
  1981年   407篇
  1980年   345篇
  1979年   333篇
  1978年   352篇
  1977年   335篇
  1976年   280篇
  1975年   276篇
  1974年   266篇
  1973年   243篇
  1972年   146篇
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
1.
Journal of Fluorescence - This report describes a combined immunofluorescence and fluorescence viability stain applied as one staining solution for rapid detection of live Legionella...  相似文献   
2.
3.
4.
The complex interplay of restricted mass transport leading to local accumulation or depletion of educts, intermediates, products, counterions and co-ions influences the reactions at the active sites of electrocatalysts when electrodes are rough, three-dimensionally mesoporous or nanoporous. This influence is important with regard to activity, and even more to selectivity, of electrocatalytic reactions. The underlying principles are discussed based on the growing awareness of these considerations over recent years.  相似文献   
5.
A simple to use nuclear magnetic resonance analysis method has been tested on complex 1H, 19F, and 13C multiplets. This open-source line-shape analysis method analysis of total lineshape (ANATOLIA)1 provides some significant advantages over traditional assign-iterate methods of NMR spectral analysis by avoiding false minima and progressing optimisation to the global minimum. The target molecules are 1-perfluorotol-4-yl-2-perfluorotol-4-yl-oxymethyl-1H-benzimidazole (molecule-I) and 1-tetrafluoropyrid-4-yl-2-tetrafluoropyrid-4-yl-thio-1H-benzimidazole (molecule-II) which were produced as part of a family of fluorinated drug scaffolds prepared for anticancer and antiparasitic screening. Spectra display significant second-order effects with 1H Δδ = 3.68 and 4.67 Hz for the aromatic hydrogen “triplets”, with 19F 4JAA', 4JBB', 4JXX', and 4JYY' coupling constants range from +4.8 to −14.0 Hz and for 13C-isotopomers 19F Δδ of up to 111.56 Hz. A spin-system of six coupling nuclei (HaHbHcHd FYFY') was analysed in 12 s, a spin-system of nine coupling fluorine nuclei (AA'BB'CCC-YY') was analysed within 2 min, and 10 coupling nuclei (XX'YY'ZZZ-BB'-Hd) was optimised in 6 min using a laptop computer. ANATOLIA was also robust enough to be able to yield accurate spectral values from inaccurate input values. In both compounds, a fluorine–fluorine coupling constant was identified between the two fluoro-aromatic rings (FBB' and FYY') of +4.05 and +4.67 Hz and attributed to a through-space interaction. Ab initio structure optimisations and coupling constant calculations provided useful input data for spectral analysis. A modern 19F nuclear magnetic resonance spectrum of perfluorotoluene (octafluorotoluene) and analysis from 1975 was used as a test data set to assess ANATOLIA.  相似文献   
6.
7.
8.
Algebras and Representation Theory - We would like to correct two errors in our paper Involutions of type G2 over a field of characteristic 2 [2].  相似文献   
9.
10.
A set of exact conditions is compiled for the purpose of developing and testing approximations for the exchange-correlation energy as a functional of the electron density. Special emphasis is placed upon recently developed density-scaling relationships. Commonly used generalized gradient approximations are compared against several of these conditions. A direct tabular comparison of these functionals (not of calculated properties) with one another is also made. © 1994 John Wiley & Sons, Inc.  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