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   257篇
  免费   18篇
化学   246篇
晶体学   1篇
力学   4篇
数学   7篇
物理学   17篇
  2023年   1篇
  2022年   4篇
  2021年   3篇
  2020年   1篇
  2019年   9篇
  2018年   7篇
  2017年   4篇
  2016年   9篇
  2015年   10篇
  2014年   11篇
  2013年   11篇
  2012年   24篇
  2011年   28篇
  2010年   12篇
  2009年   12篇
  2008年   11篇
  2007年   30篇
  2006年   28篇
  2005年   13篇
  2004年   11篇
  2003年   16篇
  2002年   7篇
  2001年   1篇
  2000年   4篇
  1999年   1篇
  1996年   1篇
  1994年   1篇
  1993年   1篇
  1991年   2篇
  1990年   2篇
排序方式: 共有275条查询结果,搜索用时 15 毫秒
231.
The stereoselective reduction of symmetrical prochiral dicarbonyl compounds bearing enantiotopic carbonyl groups yields several stereogenic centers in one step. In a proof‐of‐concept study, a new approach is described for the enzymatic desymmetrization of 5‐nitrononane‐2,8‐dione via sequential biocatalytic reduction steps utilizing ketoreductases to yield all possible diastereomers of 5‐nitrononane‐2,8‐diol.  相似文献   
232.
233.
234.
235.
236.
237.
Benzene adsorption behavior in a large family of 12R window zeolites (X, Y, EMT, Beta and LTL) has been examined by means of in-situ FTIR spectroscopy and correlated with the zeolite structure, the type and number of counter-ions, and the negative charge on framework oxygen atoms of zeolites. The effect of coadsorption of HCl, NH3 and CH3NH2 on the benzene location has also been studied. The present work illustrates that besides the benzene adsorption on counter ions of zeolites, the 12R windows could also be the adsorption sites for benzene. Upon adsorption of coadsorbates such as HCl, NH3 and CH3NH2, the migration of preadsorbed benzene molecules from one type of adsorption sites towards another, i.e. from 12R windows towards the cations for HCl and opposite direction for NH3 and CH3NH2, has been evidenced. The lack of adsorption of benzene on 12R windows of NaBeta even upon coadsorption of a series of basic molecules reveals that benzene adsorption on 12R windows is most likely governed by a molecular recognition effect where benzene molecule and 12R window should have the adapted chemical and structural properties like in enzyme-substrate system and zeolites can be referred to as solid enzymes or zeo-enzymes. This paper indicates also that the adsorption properties of zeolites can be modified and accommodated by introduction of a co-adsorbate.  相似文献   
238.
The n‐butyllithium and lithium 2,2,6,6‐tetramethylpiperidide metalation and the halogen‐metal exchange of imidazo[1,2‐a]quinoxaline derivatives followed by quenching with various electrophiles were studied. The reaction conditions have been optimized and various C1 substituted imidazo[1,2‐a]quinoxalines were obtained in high yields.  相似文献   
239.
240.
Nitrone 3 analogue of 5-deoxy-l-lyxose was derived from d-ribose. Its reduction with aqueous SO2 gave the corresponding 4-amino-sugar 2, a potent α-l-fucosidase inhibitor. 1,3-Dipolar cycloaddition of 3 with alkenes allowed the synthesis of acetohydroxamic acid and ethane-phosphonate derivatives. Hydroxy-ethane derivative 15 is a nanomolar α-l-fucosidase inhibitor.  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