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   41篇
  免费   1篇
  国内免费   1篇
化学   29篇
晶体学   2篇
数学   1篇
物理学   11篇
  2019年   3篇
  2018年   1篇
  2017年   1篇
  2016年   1篇
  2014年   2篇
  2013年   7篇
  2012年   3篇
  2011年   4篇
  2010年   3篇
  2009年   2篇
  2008年   2篇
  2007年   2篇
  2006年   3篇
  2004年   1篇
  2003年   2篇
  2002年   4篇
  2001年   1篇
  1973年   1篇
排序方式: 共有43条查询结果,搜索用时 156 毫秒
41.
The methods of gas-liquid chromatography and mass-selective detection were used to determine the composition of the volatile fraction of plant extracts included in herb mixtures used for treating parodontal disease. The following marker substances were found: naphthalene derivatives for pot marigold, furan derivatives for trifid bur-marigold and burnet, and the specific terpenoids for licorice, milfoil, and wild marjoram. All the plants used in the herb mixture, except for pot marigold and cinquefoil, were analyzed (ion-exclusion chromatography) for the content of lower carboxylic acids. It was established that the specific acids for the wild marjoram and licorice are ascorbic and the succinic acids, respectively.  相似文献   
42.
A technique for the quantitative determination of capsaicin in liniments by the microemulsion liquid chromatography method is proposed. Due to the absence of the homogenization, extraction and filtration stages, the procedure of sample pretreatment takes 5 minutes, which is much more rapid in comparison with the variants described in the literature (from 30 minutes to 12 hours). The full time of the analysis (including the procedure for sample pretreatment) is 20 minutes. The graduation curve is linear in the range from 0.02 to 240 mg/l. The limit of determination of capsaicin was 8 μg/I.  相似文献   
43.
An iron(III)-containing complex with the asymmetric tridentate azomethine ligand 4,4′-dodecyloxybenzoyloxybenzoyl-4-salicylidene-N′-ethyl-N-ethylenediamine with a PF 6 ? counterion is obtained. The presence of the complexing ion is confirmed by far IR Fourier spectra. The structure of the compounds is determined by matrix-assisted laser desorption/ionization with a time-of-flight mass analyzer (MALDI-ToF). The results of mass spectrometric studies are consistent with the elemental analysis data. It is found that the complexation of iron salt with an asymmetric tridentate ligand results in the formation of compounds of the composition 1:1 with octahedral packing of a metal ion in the complex. The electrochemical behavior of the compound in organic solvents is examined. The EPR study shows that iron(III) ions are in both low spin (LS) and high spin (HS) states in the complex. The LS and HS iron(III) centers are coupled into dimers in which a water molecule and the PF 6 ? counterion act as bridges. It is also found that for LS complexes in the lowtemperature phase (4.2–300 K), the (d xz ,d yz )4(d xy )1 electronic state is the ground state. It is revealed that the conversion of the sample into a high-temperature liquid crystalline (387–405 K) phase is accompanied by the conversion of the LS states of the Fe(III) ion: (d xz ,d yz )4(d xy )1 ? (d xy )2(d xz ,d yz )3. The conversion of LS states is temperature reversible and is driven by the temperature. X-ray crystallographic data confirm that the compound obtained consists of dimer formed by a hydrogen (O-H...F) bond.  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