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   29篇
  免费   0篇
化学   24篇
力学   1篇
物理学   4篇
  2018年   1篇
  2017年   1篇
  2012年   1篇
  2011年   4篇
  2010年   1篇
  2009年   6篇
  2008年   3篇
  2007年   4篇
  2006年   1篇
  2005年   1篇
  2004年   2篇
  2003年   1篇
  2002年   1篇
  2001年   1篇
  1987年   1篇
排序方式: 共有29条查询结果,搜索用时 15 毫秒
1.
Acid-catalyzed reactions of 2,3-epoxy derivatives of citral (which is a widely spread naturally occurring unsaturated aldehyde) with alcohols were studied under conditions of heterogeneous catalysis and in fluorosulfonic acid. A number of new products were obtained, and possible mechanisms of their formation were proposed.  相似文献   
2.
Isoflavonoids (-)-medicarpin, (-)-vestitol, and formononetin and butylphenols raspberry ketone and rhododendrol were isolated for the first time from the ethylacetate extract of Hedysarum thienum roots by column chromatography. GC-MS showed that the ethylacetate extract contained fatty acids, the principal ones being palmitic, linoleic, oleic, behenic, and lignocerinic. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 6–9, January–February, 2007.  相似文献   
3.
4.
The condensation of amino acids with (+)-usnic acid involves the 2-positioned acetyl group of the latter and gives derivatives containing an enamine fragment. Dedicated to the memory of Academician N. N. Vorozhtsov on the 100th anniversary of his birth. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1203–1205, June, 2007.  相似文献   
5.
6.
Results of an experimental study of low-frequency broadband pulsed signal propagation in a waveguide that includes the shelf zone, the continental slope, and the deep sea region are presented. Using phase-manipulated signals with central frequencies of 366 and 600 Hz, pulsed characteristics are measured at six points along the propagation track, the maximal distance from the source being 368 km. It is experimentally demonstrated that, in the presence of a negative sound velocity gradient in the near bottom layer on the shelf with a small bottom slope, the choice of the source position at the shelf bottom near the shoreline provides the formation of a continuous illumination zone in the deep sea near the USC axis and a stable pulsed characteristic with two main sound energy arrivals. The propagation velocity of the pulse that is last to arrive is identical (within the measurement error) to the velocity of sound on the USC axis at the point of reception. Possibilities for practical application of the results obtained from the experiment are discussed.  相似文献   
7.
Transformations of diepoxy derivatives of limonene under conditions of homogeneous acid catalysis were studied, and their results were compared with those obtained over heterogeneous catalysts. A number of previously unknown compounds were isolated. The most possible transformation pathways were analyzed by computer simulation using molecular-mechanics and quantum-chemical methods.  相似文献   
8.
Isoflavonoids (−)-medicarpin, (−)-vestitol, formononetin, 8-hydroxydaidzein, and 6″-O-acetylononin were isolated for the first time in addition to (−)-catechin, (−)-epicatechin, protocatechoic acid, raspberry ketone, and rhododendrol from the alcohol extract of Hedysarum theinum roots. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 26–28, January–February, 2008.  相似文献   
9.
Reactions of (+)-usnic acid with a number of substituted (halo, alkyl, alkoxy, nitro) phenylhydrazines led to the formation of the corresponding benzofuro[3,2-f]indazole derivatives or hydrazones at the acetyl group on C2, depending on the initial hydrazine.  相似文献   
10.
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