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   30篇
  免费   2篇
化学   14篇
物理学   18篇
  2020年   1篇
  2019年   3篇
  2018年   1篇
  2017年   1篇
  2016年   3篇
  2014年   1篇
  2013年   1篇
  2011年   1篇
  2008年   1篇
  2006年   2篇
  2005年   2篇
  2004年   3篇
  2003年   1篇
  1999年   1篇
  1986年   1篇
  1984年   2篇
  1983年   2篇
  1976年   1篇
  1975年   2篇
  1965年   1篇
  1964年   1篇
排序方式: 共有32条查询结果,搜索用时 15 毫秒
1.
2.
The new data concerning the reaction between substituted arylenedioxy trihalogenophosphoranes and monoalkyl- or arylacetylenes are summarized. The reaction leads to formation of six-membered heterocycles-2-oxo-4-R-benzo[ e ]-1,2-oxaphosphorin-3-enes. The substituent effects in the phosphorane and acetylene molecules on the ipso -substitution and halogenation regiochemistry are discussed. The ipso -substitution of tert -butyl group on chlorine and the exchange of bromine on chlorine and iodine on hydrogen have been observed, along with formation of benzophosphorines. The interaction of tetrachloro- ortho -benzoquinone with phosphorus trichloride and arylacetylenes is proposed as a new modification of the reaction leading to the formation of benzo[ e ]-1,2-oxaphosphorines. The structures of some benzo[ e ]-1,2-oxaphosphorines are determined by the single crystal X-ray diffraction.  相似文献   
3.
4.
Abstract

FeCl3·6H2O-catalyzed Ritter amidation of deltacyclene and hexacyclic norbornadiene dimers containing both a double bond and a three-carbon ring in the molecule with acetonitrile and water was performed. Depending on the hydrocarbon structure, the reaction proceeds via C-C bond cleavage in the three-carbon ring or at the double bond to form the corresponding N-acetamides.  相似文献   
5.
6.
The author shows that the ring form of the diffusion effects observed in the initial stages of decomposition of many alloys, including AlZn and AlAg, is due not to a form effect and not to a correlation effect of the spherical Guinier groups, but mainly to their internal structure — scattering from their isotropic modulated structure.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 7–13, October, 1976.  相似文献   
7.
8.
In this paper, we developed a simple approach to predict the APD/PMT (avalanche photodiode/photomultiplier) lidar detector performance in the presence of residual skylight background. By normalizing all relevant photodetector noise sources to the quantum noise, we obtain quantitative expressions for the degradation of the signal-to-noise ratio (SNR), the increasing threshold sensitivity of and decreasing lidar operation range. To apply the formalism to any lidar photodetectors operating in the ultra violet, visible and near-infrared spectral regions and to perform a comparative analysis of PMT and APD capabilities as the best photodetectors for ultra-violet (UV), visible (Vis) and near infra-red (NIR) lidar, we utilize a set of spectral characteristics that are built from an envelope of individual PMT and APD component responses. On this basis, the general analysis of system performance under intense background conditions is developed, and practical recommendations on detector use for each spectral region are given. The dimensionless formalism and the generalized detector spectral models used allows our analysis to be applied to nearly any lidar receiver operating over very different signal/background situations.  相似文献   
9.
The synthesis of quinoline derivatives by cyclocondensation of anilines with 1,2‐ethanediol, 1,2‐propanediol, and 1,2‐butanediol in the presence of iron‐containing catalysts was performed for the first time.  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