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   118篇
  免费   4篇
  国内免费   26篇
化学   136篇
综合类   2篇
数学   1篇
物理学   9篇
  2022年   1篇
  2021年   2篇
  2020年   2篇
  2019年   5篇
  2018年   5篇
  2017年   3篇
  2016年   4篇
  2015年   1篇
  2014年   3篇
  2013年   18篇
  2012年   12篇
  2011年   12篇
  2010年   7篇
  2009年   5篇
  2008年   5篇
  2007年   7篇
  2006年   7篇
  2005年   3篇
  2004年   3篇
  2003年   3篇
  2002年   10篇
  2001年   1篇
  2000年   3篇
  1999年   9篇
  1998年   5篇
  1996年   2篇
  1995年   2篇
  1994年   1篇
  1993年   3篇
  1992年   3篇
  1987年   1篇
排序方式: 共有148条查询结果,搜索用时 0 毫秒
11.
The Vilsmeier reaction of nickel(II) chlorin P6 trimethyl ester with 3-dimethyl-aminoacrolein yielded nickel(II) chlorin P6 20-(2-formylvinyl) trimethyl ester and nickel(II) chlorin P6 3-(1-hydroxyethyl)-3-devinyl-20-(2-formylvinyl) trimethyl ester. Also, the outgrowths of nickel(II) chlorin P6 20-(2-formyl) trimethyl ester and nickel(II) chlorin P6 3-(2-formylvinyl)-3-devinyl-20-(2-formyl) trimethyl ester were obtained by Vilsmeier reaction with dimethylformamide. By treating the derivatives of nickel(II) 20-(2-formyl)-chlorin and nickel(II) 3-(2-formylvinyl)-20-(2-formyl)-chlorin with trifluoracetic acid, the removal of the central nickel(II) ion was accomplished. The derivatives of 20-(2-formyl)-chlorin and 3-(2-formylvinyl)-20-(2-formyl)-chlorin demonstrated considerable bathochromic shift of the major absorption band in the red region of the optical spectrum.  相似文献   
12.
The procedure of microphase adsorption–spectral correction is applied to the interaction of eosine Y (EO) to the micelles of cetyl trimethyl ammonium bromide (CTAB). The Langmuir aggregation of EO on CTAB occurs owing to microelectrostatic attraction. The results have shown that at pH 3.8, monomeric and micellar aggregates have the structure EO5·CTAB2 and (EO5·CTAB2)39. The adsorption constant of an aggregate is 7.01·105, its molar absorption coefficient is = 8.8·104 liters·mole–1·cm–1 at 550 nm. Application of the aggregation of EO on CTAB gives satisfactory results for quantitative determination of cation surfaceactive agents (surfactants).  相似文献   
13.
选用聚乙二醇二丙烯酸酯(PEGDA)为扩链剂,以丙烯酰胺(AM)、2-甲基-2-丙烯酰胺基丙磺酸(AMPS)、甲基丙烯酰氧乙基三甲基氯化铵(DMC)为主单体,采用水溶液聚合方法合成了两性三元共聚物AM/AMPS/DMC;测定了共聚物的性能,并利用红外光谱研究了其分子结构.结果表明,所合成的共聚物具有良好的耐酸和高温稳定性,以及高抗剪切率.  相似文献   
14.
Reactions of hexafluoroacetone dialkoxyphosphorylimines with NH-, PH-, and CH-nucleophiles, trimethyl phosphite, andN,N-dimethylaniline, and [2+4]-cycloaddition reaction have been studied. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1408–1412, July, 1998.  相似文献   
15.
A sensitive, accurate, and cost effective method for the quantification of trimethyl phosphate, which is highly polar and volatile, in environmental water is presented. Trimethyl phosphate was headspace solid‐phase microextracted on a molecularly imprinted polymeric fiber, and then the fiber was thermally desorbed in the gas chromatograph injector, and the compound was determined. The trimethyl phosphate imprinted polymeric fiber was prepared by copolymerization in a fused silica capillary tube and obtained by removal of the wall of fused silica capillary tube. The monolithic fiber displayed good selectivity toward trimethyl phosphate among its structural analogues. It was thermally stable up to 320°C so that it can withstand the high temperature of the gas chromatograph injector for desorption. The factors influencing the performance of its headspace solid‐phase microextraction were studied. Under the optimal conditions, the method for quantification of trimethyl phosphate in environmental water was well developed. It exhibited significant linearity, the lowest limit of quantification to date, and good recoveries. Using this method, trimethyl phosphate was detected in five out of seven environmental water samples at concentration levels from 0.28 to 1.22 μg/L, illustrating the heavy pollution of trimethyl phosphate in environmental water.  相似文献   
16.
The liquid membrane oscillation of a novel water (aqueous tetradecyl trimethyl ammoniumbromide, TTAB and alcohol solution)/oil (picric acid in chloroform solution)/water (aqueous glucose solution) system was investigated. By using homemade device, the curves of various liquid membranes oscillation with different concentration of TTAB and picric acid, types of alcohol and other organic solvents at different temperature were measured. The results show that the water (aqueous 7 mmol/L of TTAB and 0.5 mol/L of n-propanol solution)/oil (0.5 mmol/L of picric acid in chloroform solution)/water (aqueous glucose solution) system performed sustained and stable oscillation at 30 ℃. And the novel system can recognise added amino acid.  相似文献   
17.
CTAB-己醇-辛烷体系分离纯化醇脱氢酶的反萃研究   总被引:2,自引:0,他引:2  
本文报道了用反胶束体系萃取醇脱氢酶(ADH)的研究结果。在此萃取体系中,以十六烷基三甲基溴化铵(CTAB)作为表面活性剂,辛烷和己醇作为溶剂和助溶剂。考察了表面活性剂及助溶剂浓度,水相pH值对ADH萃取的影响。详细讨论了离子强度、异丙醇浓度和振荡时间对ADH反萃的影响。确定了最佳反向萃取条件。  相似文献   
18.
Yu F  Ding Y  Gao Y  Zheng S  Chen F 《Analytica chimica acta》2008,625(2):195-200
A new spectrofluorimetric method was developed for the determination of trace amounts of DNA using the calcein as a fluorescent probe. In the presence of appropriate amounts of the cationic surfactant cetyl trimethyl ammonium bromide (CTAB), the anionic dye calcein dimerizes. The weak fluorescence intensity of the dimer was enhanced by adding DNA at pH 6–7. The interaction between calcein–CTAB and DNA was studied on the basis of this behavior and a new method was developed for determining DNA. Under the optimal conditions, the enhanced fluorescence intensity was in proportion to the concentration of DNA in the range of 4.0 × 10−6 to 8.0 × 10−5 g L−1 for fsDNA and thermally denatured ctDNA (4.5 × 10−6 to 9.0 × 10−5 g L−1). The detection limits (S/N = 3) were 2.0 × 10−6 and 2.2 × 10−6 g L−1, respectively. This method was used for determining the concentration of DNA in synthetic samples with satisfactory results.  相似文献   
19.
两亲分子由于具有自组装性质,如表面活性剂分子自组装形成胶束,囊泡,天然的磷脂分子自组装形成脂质体,继而参于生物膜的形成,这是大家所熟悉的.高分子两亲分子尤其是两亲性两嵌段高分子具有自组装性质,并形成规整性好的聚集体[1~3].聚电介质表面活性剂体系...  相似文献   
20.
两亲分子由于具有自组装性质,如表面活性剂分子自组装形成胶束,囊泡,天然的磷脂分子自组装形成脂质体,继而参于生物膜的形成,这是大家所熟悉的.高分子两亲分子尤其是两亲性两嵌段高分子具有自组装性质,并形成规整性好的聚集体[1~3].聚电介质 表面活性剂体系...  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