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   146篇
  免费   39篇
  国内免费   25篇
化学   197篇
晶体学   2篇
物理学   11篇
  2022年   6篇
  2021年   4篇
  2020年   11篇
  2019年   6篇
  2018年   5篇
  2017年   3篇
  2016年   6篇
  2015年   9篇
  2014年   13篇
  2013年   9篇
  2012年   8篇
  2011年   12篇
  2010年   8篇
  2009年   8篇
  2008年   14篇
  2007年   9篇
  2006年   4篇
  2005年   6篇
  2004年   12篇
  2003年   6篇
  2002年   4篇
  2001年   4篇
  2000年   3篇
  1999年   3篇
  1998年   2篇
  1997年   5篇
  1996年   2篇
  1995年   2篇
  1994年   3篇
  1993年   3篇
  1992年   4篇
  1991年   3篇
  1990年   4篇
  1989年   2篇
  1988年   2篇
  1987年   2篇
  1986年   1篇
  1985年   2篇
排序方式: 共有210条查询结果,搜索用时 15 毫秒
21.
核黄素光敏氧化噻吩脱硫研究   总被引:4,自引:5,他引:4  
以噻吩的正辛烷溶液模拟FCC汽油,以水为萃取剂,以空气中的O2为氧化剂,以核黄素为光敏剂,研究了噻吩在500W高压汞灯照射下的光化学氧化。实验结果表明,在通气量为150mL/min、水油比为1∶1、核黄素加入量为30μmol/L的条件下,反应3h后噻吩的脱硫率能够达到85.4%。核黄素的敏化作用是通过激发基态氧为单线态氧实现的,噻吩氧化脱硫为一级动力学反应,加入光敏剂时反应速率常数k=9.10×10-5s-1,半衰期t1/2=2.12h。  相似文献   
22.
The rate constants for the reaction between chlorine atoms and either 5-methyl-2-hexanol, 2,2-dimethyl-3-hexanol, or 2,4,4-trimethyl-1-pentanol at 298 K were determined using the relative method with 2-butanol and 1-pentanol as reference compounds. The values obtained for 5-methyl-2-hexanol, 2,2-dimethyl-3-hexanol, and 2,4,4-trimethyl-1-pentanol (k × 1010 cm3 molec−1 s−1) were, respectively, (2.64 ± 0.5), (2.72 ± 0.5), and (2.50 ± 0.4), in agreement with the values of the rate constants reported in bibliography for similar alcohols and the values estimated by structure activity relationship methods. The photooxidation products of 2,4,4-trimethyl-1-pentanol initiated by chlorine atoms were identified (formaldehyde, 2-propanone, 2,2-dimethyl propanal, 4,4,-dimethyl-2-pentanone, and 3,3-dimethylbutanal), and the reaction mechanism was determined.  相似文献   
23.
The photooxidation of a mustard‐gas simulant, 2‐chloroethyl ethyl sulfide (CEES), is studied using a porphyrin‐based metal–organic framework (MOF) catalyst. At room temperature and neutral pH value, singlet oxygen is generated by PCN‐222/MOF‐545 using an inexpensive and commercially available light‐emitting diode. The singlet oxygen produced by PCN‐222/MOF‐545 selectively oxidizes CEES to the comparatively nontoxic product 2‐chloroethyl ethyl sulfoxide (CEESO) without formation of the highly toxic sulfone product. In comparison to current methods, which utilize hydrogen peroxide as an oxidizing agent, this is a more realistic, convenient, and effective method for mustard‐gas detoxification.  相似文献   
24.
The formation of CF3C(O)CF2N(O.)O2CF2C(O)CF3 free radicals upon the UV irradiation of nitropentafluoroacetone (1) in toluene and mesitylene is established by ESR. The most likely cause of their formation is the one-electron oxidation of the solvents by photoexcited1 followed by decay of the radical anion formed from1 with the expulsion of an NO2 anion and attachment of the radical to a molecule of original1. The irradiation of 1 in triethylsilane results in the elimination of a fluoride ion and fixation of a CF3COCFN(O)O' radical. UV irradiation of ketone1 in pentane results in the abstraction of a hydrogen atom from the solvent and the formation of a CF3COCF2N(OH)O ' radical.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 512–514, March, 1993.  相似文献   
25.
Novel profluorescent mono‐ and bis‐isoindoline nitroxides linked to napthalimide and perylene diimide structural cores are described. These nitroxide‐fluorophore probes display strongly suppressed fluorescence in comparison to their corresponding non‐radical diamagnetic methoxyamine derivatives. The perylene‐based probe possessing two isoindoline systems tethered through ethynyl linkages was shown to be the most photostable in solution, demonstrating significantly enhanced longevity over the 9,10‐bis(phenylethynyl)anthracene fluorophore used in previous profluorescent nitroxide probes.  相似文献   
26.
27.
The functionalization of fullerene has been extensively studied and various fullerene derivatives have been synthesized. We have succeeded in the functionalization of [60]fullerene by using α‐aminoalkyl radicals generated by visible‐light‐mediated single‐electron oxidation of α‐silylamines as synthetic intermediates. In these reactions, the introduction of diarylamino groups, which are useful electron donors, has been easily achieved.  相似文献   
28.
29.
The pH effect on the one-electron photooxidation of 5-methyl-2'-deoxycytidine (d(m)C) by sensitization with 2-methyl-1,4-naphthoquinone (NQ) was investigated. Photoirradiation of an aqueous solution containing d(m)C and NQ under slightly acidic conditions of pH 5.0 efficiently produced 5-formyl-2'-deoxycytidine, whereas similar NQ-photosensitized oxidation of d(m)C proceeded to a lesser extent under more acidic or basic conditions. Fluorescence-quenching experiments revealed that the less-efficient photooxidation at pH values below 4.5 is attributed to the decreased rate of one-electron oxidation of d(m)C owing to protonation at the N(3)-position. The NQ-photosensitized oxidation of an N(4)-dimethyl-substituted d(m)C derivative under various pH conditions also suggests that the pH change in the range of 5.0 to 8.0 may be responsible for a reversible deprotonation-protonation equilibrium at the N(4)-exocyclic amino group of the d(m)C radical cation. In accord with the photochemical reactivity of monomeric d(m)C, the 5-methylcytosine residue in oligodeoxynucleotides was oxidized efficiently by photoexcited NQ-tethered oligodeoxynucleotides under slightly acidic conditions to form an alkali-labile 5-formylcytosine residue.  相似文献   
30.
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