全文获取类型
收费全文 | 63篇 |
免费 | 6篇 |
国内免费 | 5篇 |
专业分类
化学 | 70篇 |
晶体学 | 1篇 |
力学 | 1篇 |
综合类 | 1篇 |
物理学 | 1篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 1篇 |
2020年 | 1篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2017年 | 3篇 |
2016年 | 5篇 |
2015年 | 3篇 |
2014年 | 1篇 |
2013年 | 3篇 |
2012年 | 2篇 |
2010年 | 3篇 |
2009年 | 2篇 |
2008年 | 4篇 |
2007年 | 7篇 |
2006年 | 3篇 |
2005年 | 3篇 |
2004年 | 1篇 |
2003年 | 6篇 |
2002年 | 2篇 |
2001年 | 3篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1995年 | 1篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1984年 | 1篇 |
排序方式: 共有74条查询结果,搜索用时 15 毫秒
41.
沙棘黄酮的测定及其抗氧化作用 总被引:43,自引:3,他引:43
沙棘(HippophaerhamnoidesL.)是胡颓子科沙棘属植物,为灌木或乔木。沙棘果实含有多种生物活性物质,是我国古代藏医、蒙医用来治病的常用药[1]。本文采用三氯化铝比色法测定了沙棘根皮、茎皮和叶中黄酮类化合物含量,并考察其对羟自由基和超氧离子自由基的清除作用。1 实验部分1 1 仪器和试剂722型光栅可见分光光度计(上海分析仪器总厂);756MC型紫外可见分光光度计(上海分析仪器总厂);pHS 3TC型精密数显酸度计(上海天达仪器有限公司)。槲皮素(中国预防医学科学院劳卫所);邻苯三酚(贵州遵义市第二化工厂);三… 相似文献
42.
本文采用静态法研究了联氨浓度、氧气分压、碱度、温度及杂质金属离子对联氨稀溶液自氧化反应的影响,获得Cu~(2+)系联氨自氧化反应的有效催化剂,确立了无Cu~(2+)催化时,联氨自氧化反应的动力学方程为,在Cu~(2+)催化条件下联氨自氧化反应的动力学方程为. 相似文献
43.
Mechanism of the catalytic deperoxidation of tert-butylhydroperoxide with cobalt(II) acetylacetonate
Turrà N Neuenschwander U Baiker A Peeters J Hermans I 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(44):13226-13235
The Co(II)/Co(III)-induced decomposition of hydroperoxides is an important reaction in many industrial processes and is referred to as deperoxidation. In the first step of the so-called Haber-Weiss cycle, alkoxyl radicals and Co(III)-OH species are generated upon the reaction of the Co(II) ion with ROOH. The catalytic cycle is closed upon the regeneration of the Co(II) ion through the reaction of the Co(III)-OH species with a second ROOH molecule, thus producing one equivalent of the peroxyl radicals. Herein, the deperoxidation of tert-butylhydroperoxide by dissolved cobalt(II) acetylacetonate is studied by using UV/Vis spectroscopy in situ with a noninteracting solvent, namely, cyclohexane. Kinetic information extracted from experiments, together with quantum-chemical calculations, led to new mechanistic hypotheses. Even under anaerobic conditions, the Haber-Weiss cycle initiates a radical-chain destruction of ROOH propagated by both alkoxyl and peroxyl radicals. This chain mechanism rationalizes the high deperoxidation rates, which are directly proportional to the cobalt concentration up to approximately 75 μM at 333 K. However, at higher cobalt concentrations, a remarkable decrease of the rate is observed. The hypothesis put forward herein is that this remarkable autoinhibition effect could be explained by the hitherto overlooked chain termination of two Co(III)--OH species. The direct competition between the first-order Haber-Weiss initiation and the second-order termination can indeed explain this peculiar kinetic behavior of this homogeneous deperoxidation system. 相似文献
44.
Asim Maity Sung‐Min Hyun Alan K. Wortman Prof. David C. Powers 《Angewandte Chemie (International ed. in English)》2018,57(24):7205-7209
Hypervalent iodine(V) reagents, such as Dess–Martin periodinane (DMP) and 2‐iodoxybenzoic acid (IBX), are broadly useful oxidants in chemical synthesis. Development of strategies to generate these reagents from dioxygen (O2) would immediately enable use of O2 as a terminal oxidant in a broad array of substrate oxidation reactions. Recently we disclosed the aerobic synthesis of I(III) reagents by intercepting reactive oxidants generated during aldehyde autoxidation. In this work, aerobic oxidation of iodobenzenes is coupled with disproportionation of the initially generated I(III) compounds to generate I(V) reagents. The aerobically generated I(V) reagents exhibit substrate oxidation chemistry analogous to that of DMP. The developed aerobic generation of I(V) has enabled the first application of I(V) intermediates in aerobic oxidation catalysis. 相似文献
45.
Qing‐Bao Zhang Wen‐Liang Jia Yong‐Liang Ban Yong Zheng Prof. Dr. Qiang Liu Prof. Dr. Li‐Zhu Wu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(8):2595-2598
In the presence of tetrabutylammonium fluoride and molecular sieves (MS) 4 Å in DMF, an efficient autoxidation reaction of 2‐oxindoles with ketones under air at room temperature has been developed. This approach may provide a green, practical, and metal‐free protocol for a wide range of biologically important 3‐hydroxy‐3‐(2‐oxo‐alkyl)‐2‐oxindoles. 相似文献
46.
47.
48.
In this work, a complementary experimental and theoretical approach is used to unravel the formation of byproducts in the autoxidation of cyclohexane. The widely accepted vision that cyclohexanone would be the most important precursor of undesired products was found inconsistent with several experimental observations. However, the propagation reaction of cyclohexyl hydroperoxide, which we recently put forward as the missing source of cyclohexanol and cyclohexanone, is now unambiguously identified also as the dominant path leading to byproducts. Indeed, this overlooked reaction produces large amounts of cyclohexoxy radicals, able to ring-open via a beta-C--C cleavage to omega-formyl radicals. The pathway by which these radicals are converted into the observed and quantified byproducts is derived in this work. In this liquid-phase reaction, solvent cages were found very important, steering the fate of nascent species. 相似文献
49.
Fei He Qiu‐Hong Pan Ying Shi Xue‐Ting Zhang Chang‐Qing Duan 《Journal of mass spectrometry : JMS》2009,44(5):633-640
Autoxidation of flavan‐3‐ols was carried out in aqueous/methanol model solutions under mildly acidic conditions (pH 6.0), and these autoxidation products were analyzed by using high performance liquid chromatography (HPLC) coupled with tandem mass spectrometry (MS/MS). The results showed that (+)‐catechins and (?)‐epicatechins generated autoxidation reaction with each other to form a series of oligomers that had the same [M ? H]? molecular ions (MS1) as those of natural procyanidins, but had completely different fragment ions (MS2). According to MS/MS analysis, the major fragments of these oligomers were derived not only from the retro‐Diels–Alder (RDA) dissociations on the C‐rings of the flavan‐3‐ol units, but also from the quinone‐methide (QM) cleavage of the interflavan linkages (IFL), and thus they were identified as B‐type dehydrodicatechins, B‐type dehydrotricatechins and A‐type dehydrotricatechins, respectively. The potential structures of their [M ? H]? molecular ions and partial fragment ions were deduced on the basis of the MS/MS characterization and the oxidation of flavan‐3‐ols in previous reports. Some specific fragment ions were found to be very useful for identifying the autoxidation oligomers (the B‐type dehydrodicatechins at m/z 393, the B‐type dehydrotricatechins at m/z 681 and the A‐type dehydrotricatechins at m/z 725). Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
50.
Tao SUN Zhi Shen JIA Wei Xiang CHEN Ya Xu JIN Zhu De XU* Department of Chemistry Zhejiang University Hangzhou 《中国化学快报》2001,(11)
The bioactivity study of C60 and its relative derivatives is of considerable importance. Functional fullerenes have peculiar biological activities, such as enzymatic inhibition, anti-HIV activity, neuroprotection, antibacterial activity, DNA cleavage, and photodynamic therapy et al.1. Neuroprotective properties are based on the facts that functional fullerenes have antioxidant properties and high reactivity toward free radical2. Active oxygen radical in biological system mainly include… 相似文献