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   346篇
  免费   2篇
化学   336篇
数学   1篇
物理学   11篇
  2018年   5篇
  2017年   1篇
  2016年   6篇
  2015年   1篇
  2014年   5篇
  2013年   12篇
  2012年   12篇
  2011年   13篇
  2010年   19篇
  2009年   13篇
  2008年   21篇
  2007年   16篇
  2006年   10篇
  2005年   10篇
  2004年   4篇
  2003年   17篇
  2002年   15篇
  2001年   8篇
  2000年   1篇
  1999年   5篇
  1997年   5篇
  1996年   4篇
  1995年   3篇
  1994年   4篇
  1993年   6篇
  1992年   11篇
  1991年   7篇
  1990年   8篇
  1989年   12篇
  1988年   4篇
  1987年   6篇
  1986年   4篇
  1985年   6篇
  1984年   3篇
  1983年   4篇
  1982年   6篇
  1981年   3篇
  1980年   6篇
  1979年   6篇
  1978年   8篇
  1977年   11篇
  1976年   1篇
  1975年   4篇
  1974年   5篇
  1973年   1篇
  1972年   3篇
  1971年   2篇
  1967年   3篇
  1966年   5篇
  1964年   1篇
排序方式: 共有348条查询结果,搜索用时 865 毫秒
101.
Nanoporous (11–12 nm) crosslinked macrocyclic polyethers with vinyloxy and hydroxyl groups have been synthesized by the free-radical polymerization of diethylene glycol divinyl ether (AIBN, 80°C, i-octane), followed by acidic hydrolysis. It has been shown that the polymers react with KOH to form insoluble superbase complexes and alcoholates capable of catalyzing vinylation of ethylene glycol by acetylene.  相似文献   
102.
103.
We have studied the reaction of 1-vinyl-2-(2-furyl)- and -(2-thienyl)pyrroles with trifluoroacetic anhydride, with hydrogen in the presence of catalysts (Raney nickel, palladium black, palladous chloride), with propargyl alcohol in electrophilic conditions [catalysis by perfluorobutyric acid in the system azoisobutyrodinitrile (AIBN)-CCl4), and with alkane thiols with AIBN initiation. The products are novel substituted hetarylpyrroles.See [1] for Communication 40.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 337–342, March, 1991.  相似文献   
104.
(p-R-phenyl)-4-methyl-, 4-methoxy-, and 4-hydroxy-5-pyrimidinecarboxylates have been synthesized and their liquid crystal properties examined. Compounds containing methyl and methoxy groups in the lateral position of the molecule are nematic liquid crystals with a mesophase range of 30-50°C, but the 4-hydroxy derivatives are smectic liquid crystals. With variants of the substituents in a series of (p-R-phenyl)-4-substituted 5-pyrimidinecarboxylates the mp of individual representatives were successfully reduced by 50°C in comparison with the 4-unsubstituted analogs and the range of the mesomorphic state was extended to 190°C.  相似文献   
105.
106.
4,4′-Bis[2-(1-vinylpyrrolyl)]diphenyloxide, 4,4′-bis(2-pyrrolyl)diphenylsulfide, 4-(2-pyrrolyl)-4′-[2-(1-vinylpyrrolyl)]diphenylsulfide and 4,4′-bis[2-(1-vinylpyrrolyl)]diphenylsulfide have been synthesized in a one-pot procedure from oximes of corresponding diacetylphenylenoxide and -sulfide through their reaction with acetylene in the MOH-DMSO systems (M=Li, K) at 80-130 °C under pressure of 10-15 atm, thus illustrating applicability and general character of the reaction of synthesis of diverse dipyrrole-phenylene assemblies and their N-vinyl derivatives. Two of the pipyrroles are promising for creating new conducting polymers with sulfur and oxygen atoms in the conjugation chain and for the study of the influence of the diphenyleneheteroatom moiety on conductivity of final polymer products. For the dipyrroles with the diphenyleneheteroatom moieties and 1,4-phenylene spacer the luminescence characteristics were determined.  相似文献   
107.
4,5,6,7-Tetrahydroindole and its 1-vinyl derivative were obtained in overall yields of 30–60% by the reaction of cyclohexanone oxime with 1,2-dichloro- and 1,2-dibromoethane in the MOH-dimethyl sulfoxide (DMSO) superbase system (M = K, Na, Li). Nucleophilic substitution of the halogen in the dihaloethanes by the oximate anion to give the corresponding ethylene glycol bis (imido ether) is a side reaction. The effect of the reaction conditions on the yields of products and the selectivity of the process was examined.See [1] for communication 21.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1202–1204, September, 1982.  相似文献   
108.
109.
110.
In the presence of 2,2-azobisisobutyronitrile or in the absence of an initiator alkanethiols add to 1-vinylpyrroles exclusively counter to Markovnikov's rule to give 1-(2-alkylthioethyl)pyrroles (in yields up to 94%).Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1636–1639, December, 1977.  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