全文获取类型
收费全文 | 60篇 |
免费 | 9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
31.
Xiaobo Xie Dr. Long Zhang Qing He Jian Hou Changming Xu Ning Zhang Prof. Dr. Sanzhong Luo Prof. Dr. Zongxiu Nie 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(41):14630-14637
We present herein a mechanistic investigation by nanoelectrospray ionization mass spectrometry of copper‐catalyzed aerobic oxidative processes involved in the N‐nitrosocarbonyl aldol reaction of N‐hydroxycarbamates. Protonated amine and copper as charge‐tags aided the detection of reaction intermediates, which verified the enamine mechanism together with a competing enol process. Our experimental results reveal that the copper‐catalyzed aerobic oxidation of N‐hydroxycarbamates may proceed through an autoxidation catalytic mechanism in which a CbzNHO. radical abstracts a hydrogen from the bound N‐hydroxycarbamate to release the nitroso intermediate through a bimolecular hydrogen‐atom transfer. In this process, the chiral diamine also works as a ligand for copper to facilitate the aerobic oxidative step. The dual role of the chiral vicinal diamine as both an aminocatalyst and a bidentate ligand was finally uncovered. 相似文献
32.
Dr. Riccardo Amorati Philip T. Lynett Dr. Luca Valgimigli Prof. Dr. Derek A. Pratt 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(20):6370-6379
Sulfenic acids play a prominent role in biology as key participants in cellular signaling relating to redox homeostasis, in the formation of protein‐disulfide linkages, and as the central players in the fascinating organosulfur chemistry of the Allium species (e.g., garlic). Despite their relevance, direct measurements of their reaction kinetics have proven difficult owing to their high reactivity. Herein, we describe the results of hydrocarbon autoxidations inhibited by the persistent 9‐triptycenesulfenic acid, which yields a second order rate constant of 3.0×106 M ?1 s?1 for its reaction with peroxyl radicals in PhCl at 30 °C. This rate constant drops 19‐fold in CH3CN, and is subject to a significant primary deuterium kinetic isotope effect, kH/kD=6.1, supporting a formal H‐atom transfer (HAT) mechanism. Analogous autoxidations inhibited by the Allium‐derived (S)‐benzyl phenylmethanethiosulfinate and a corresponding deuterium‐labeled derivative unequivocally demonstrate the role of sulfenic acids in the radical‐trapping antioxidant activity of thiosulfinates, through the rate‐determining Cope elimination of phenylmethanesulfenic acid (kH/kD≈4.5) and its subsequent formal HAT reaction with peroxyl radicals (kH/kD≈3.5). The rate constant that we derived from these experiments for the reaction of phenylmethanesulfenic acid with peroxyl radicals was 2.8×107 M ?1 s?1; a value 10‐fold larger than that we measured for the reaction of 9‐triptycenesulfenic acid with peroxyl radicals. We propose that whereas phenylmethanesulfenic acid can adopt the optimal syn geometry for a 5‐centre proton‐coupled electron‐transfer reaction with a peroxyl radical, the 9‐triptycenesulfenic is too sterically hindered, and undergoes the reaction instead through the less‐energetically favorable anti geometry, which is reminiscent of a conventional HAT. 相似文献
33.
酮类化合物的碱催化自氧化反应受底物的结构和反应条件的影响较大。不同的底物或不同的反应条件,可得不同类型的产物。在油菜甾醇内酯 B 环的合成中,曾探索了用该反应来合成内酯环。本文报道一些与三元环共 相似文献
34.
Dmitry V. Moiseev Brian R. James 《Phosphorus, sulfur, and silicon and the related elements》2020,195(9):687-712
AbstractTetrakis(hydroxymethyl)phosphonium (HOCH2)4P+ salts, particularly the chloride (THPC) and sulfate (THPS), are among the most accessible organophosphorus compounds that can be made quantitatively from PH3 and formaldehyde in aqueous media under ambient conditions. These phosphonium salts are air-stable, and are widely used as reactants in organic syntheses, as well as in textile or oil industries. Synthesis of tris(hydroxymethyl)phosphine (THP), an active component of the salts, is more complicated because direct synthesis from PH3 and CH2O requires either pressure and high temperature, at which THP rearranges into bis(hydroxymethyl)methylphosphine oxide, CH3P(O)(CH2OH)2, or a metal catalyst that is usually difficult or impossible to recover. Syntheses of THP based on neutralization of the salts are more convenient but require pH control and additional steps to separate THP from CH2O. This review summarizes literature data on syntheses and purification of the salts and THP, and side reactions such as thermal rearrangement and oxidation. 相似文献
35.
36.
Nils Herrmann Norah Heinz Michael Dolg Xiaoyan Cao 《Journal of computational chemistry》2016,37(20):1914-1923
Reactions involved in the autoxidation of ascorbate have been investigated with quantum chemical first‐principles and ab initio methods. Reaction energies and Gibbs energies of the reactions were calculated at the density functional theory level applying the gradient‐corrected BP86 and the hybrid B3LYP functionals together with def2‐TZVP basis sets. Results of single‐point CC2, CCSD, and CCSD(T) calculations were used for calibration of the density functional theory data and show excellent agreement with the B3LYP values. Based on the Gibbs energy ascorbic acid AscH2 is found to be the energetically lowest species in aqueous solution, whereas the monoanion ascorbate AscH is the most abundant one near pH = 7. Asc was found to be the preferred reducing agent for autoxidation and oxidation processes. The results also support a metal‐catalyzed synthesis of the reactive oxygen species H2O2 according to a redox cycling mechanism proposed in literature. © 2016 Wiley Periodicals, Inc. 相似文献
37.
38.
Justine Pallu Dr. Charlie Rabin Geordie Creste Dr. Mathieu Branca Dr. François Mavré Dr. Benoît Limoges 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(31):7534-7546
Herein, a new molecular autocatalytic reaction scheme based on a H2O2-mediated deprotection of a boronate ester probe into a redox cycling compound is described, generating an exponential signal gain in the presence of O2 and a reducing agent or enzyme. For such a purpose, new chemosensing probes built around a naphthoquinone/naphthohydroquinone redox-active core, masked by a self-immolative boronic ester protecting group, were designed. With these probes, typical autocatalytic kinetic traces with characteristic lags and exponential phases were obtained by using either UV/Visible or fluorescence optical detection, or by using electrochemical monitoring. Detection of concentrations as low as 0.5 μm H2O2 and 0.5 nm of a naphthoquinone derivative were achieved in a relatively short time (<1 h). From kinetic analysis of the two cross-activated catalytic loops associated with the autocatalysis, the key parameters governing the autocatalytic reaction network were determined, indirectly showing that the analytical performances are currently limited by the slow nonspecific self-deprotection of boronate probes. Collectively, the present results demonstrate the potential of this new exponential molecular amplification strategy, which, owing to its generic nature and modularity, is quite promising for coupling to a wide range of bioassays involving H2O2 or redox cycling compounds, or for use as a new building block in the development of more complex chemical reaction networks. 相似文献
39.
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
40.
Structural Characterization of a Hydroperoxo Nickel Complex and Its Autoxidation: Mechanism of Interconversion between Peroxo,Superoxo, and Hydroperoxo Species
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Christoph A. Rettenmeier Prof. Hubert Wadepohl Lutz H. Gade 《Angewandte Chemie (International ed. in English)》2015,54(16):4880-4884
Pincer‐stabilized nickel(I) complexes readily react with molecular oxygen to form dinuclear 1,2‐μ‐peroxo‐bridged nickel(II) complexes, which are the major components of a dynamic equilibrium with the corresponding mononuclear superoxo species. The peroxo complexes further react with hydrogen peroxide to give the corresponding nickel(II) hydroperoxides. One of these hitherto elusive species was characterized by X‐ray diffraction for the first time [O–O bond length: 1.492(2) Å]. 相似文献