全文获取类型
收费全文 | 49篇 |
免费 | 0篇 |
专业分类
化学 | 46篇 |
数学 | 1篇 |
物理学 | 2篇 |
出版年
2022年 | 2篇 |
2020年 | 3篇 |
2013年 | 2篇 |
2012年 | 1篇 |
2011年 | 1篇 |
2010年 | 4篇 |
2009年 | 2篇 |
2008年 | 1篇 |
2007年 | 3篇 |
2006年 | 2篇 |
2005年 | 2篇 |
2004年 | 1篇 |
2003年 | 1篇 |
1994年 | 2篇 |
1990年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1976年 | 2篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1970年 | 2篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1965年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有49条查询结果,搜索用时 15 毫秒
1.
2.
Petar J. Petrov Alexi A. Alexiev Galin Petrov Gianluca Giorgi 《Journal of heterocyclic chemistry》2005,42(2):313-317
The coumarino‐[3,4‐c]‐3H‐10‐methyl‐2‐oxo‐2‐phenyl‐1,2‐oxaphosphole was prepared by the addition of PhPCl2 to 3‐acetylcoumarin in the presence of acetic anhydride. Its conversion to the isomeric coumarino‐[3,4‐c]‐9H‐9‐methyl‐2‐oxo‐2‐phenyl‐1,2‐oxaphosphole was studied in different reaction conditions. The structures of the two isomers were determined by X‐ray crystallography and by ab initio molecular orbital calculations. 相似文献
3.
Electrochemical Vicinal Difluorination of Alkenes: Scalable and Amenable to Electron-Rich Substrates
Sayad Doobary Alexi T. Sedikides Henry P. Caldora Dr. Darren L. Poole Dr. Alastair J. J. Lennox 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(3):1171-1176
Fluorinated alkyl groups are important motifs in bioactive compounds, positively influencing pharmacokinetics, potency and conformation. The oxidative difluorination of alkenes represents an important strategy for their preparation, yet current methods are limited in their alkene-types and tolerance of electron-rich, readily oxidized functionalities, as well as in their safety and scalability. Herein, we report a method for the difluorination of a number of unactivated alkene-types that is tolerant of electron-rich functionality, giving products that are otherwise unattainable. Key to success is the electrochemical generation of a hypervalent iodine mediator using an “ex-cell” approach, which avoids oxidative substrate decomposition. The more sustainable conditions give good to excellent yields in up to decagram scales. 相似文献
4.
Electrochemical Vicinal Difluorination of Alkenes: Scalable and Amenable to Electron‐Rich Substrates
Sayad Doobary Alexi T. Sedikides Henry P. Caldora Darren L. Poole Alastair J. J. Lennox 《Angewandte Chemie (International ed. in English)》2020,59(3):1155-1160
Fluorinated alkyl groups are important motifs in bioactive compounds, positively influencing pharmacokinetics, potency and conformation. The oxidative difluorination of alkenes represents an important strategy for their preparation, yet current methods are limited in their alkene‐types and tolerance of electron‐rich, readily oxidized functionalities, as well as in their safety and scalability. Herein, we report a method for the difluorination of a number of unactivated alkene‐types that is tolerant of electron‐rich functionality, giving products that are otherwise unattainable. Key to success is the electrochemical generation of a hypervalent iodine mediator using an “ex‐cell” approach, which avoids oxidative substrate decomposition. The more sustainable conditions give good to excellent yields in up to decagram scales. 相似文献
5.
Asbury JB Steinel T Stromberg C Gaffney KJ Piletic IR Goun A Fayer MD 《Physical review letters》2003,91(23):237402
Hydrogen bond dynamics are explicated with exceptional detail using multidimensional infrared vibrational echo correlation spectroscopy with full phase information. Probing the hydroxyl stretch of methanol-OD oligomers in CCl4, the dynamics of the evolving hydrogen bonded network are measured with ultrashort (<50 fs) pulses. The data along with detailed model calculations demonstrate that vibrational relaxation leads to selective hydrogen bond breaking on the red side of the spectrum (strongest hydrogen bonds) and the production of singly hydrogen bonded photoproducts. 相似文献
6.
7.
The activation of the catalytic persulphate oxidation of sulphanilic acid when the catalyst, silver(I), is suitably complexed, is discussed. 2,2'-Bipyridyl is proposed as activator as it accelerates the rate-determining step of the process-the oxidation of silver(I) to silver(II). The mechanism of activation is investigated and discussed in detail. On the basis of these investigations a catalytic method has been developed for the determination of silver(I), with a sensitivity of 4 x 10(-4)mug ml and +/-7.6% relative error. 相似文献
8.
Advanced multidimensional time-correlated single photon counting (mdTCSPC) and picosecond time-resolved fluorescence in combination with site-directed fluorescence labeling are valuable tools to study the properties of membrane protein surface segments on the pico- to nanoseconds time scale. Time-resolved fluorescence anisotropy changes of protein bound fluorescent probes reveal changes in protein dynamics and steric restriction. In addition, the change in fluorescence lifetime and intensity of the covalently bound fluorescent dye is indicative of environmental changes at the protein surface. In this study, we have measured the changes in fluorescence lifetime traces of the fluorescent dye fluorescein covalently bound to the first cytoplasmic loop of bacteriorhodopsin (bR) after light activation of protein function. The fluorescence is excited by a picosecond laser pulse. The retinylidene chromophore of bR is light-activated by a 10 ns laser pulse, which in turn triggers recording of a sequence of fluorescence lifetime traces in the mdTCSPC-module. The fluorescence decay changes upon protein function occur predominantly in the 100 ps time range. The kinetics of these changes shows two transitions between three intermediate states in the second part of the bR photocycle. Correlation with photocycle kinetics allows for the determination of reaction intermediates at the proteins surface which are coupled to changes in the retinal binding pocket. 相似文献
9.
Enhanced stability and bioconjugation of photo-cross-linked polystyrene-shell, Au-core nanoparticles
Chen Y Cho J Young A Taton TA 《Langmuir : the ACS journal of surfaces and colloids》2007,23(14):7491-7497
Encapsulating Au nanoparticles within a shell of photo-cross-linked block copolymer surfactant dramatically improves the physical and chemical stability of the nanoparticles, particularly when they are applied as bioconjugates. Photo-cross-linkable block copolymer amphiphiles [polystyrene-co-poly(4-vinyl benzophenone)]-block-poly(acrylic acid) [(PS-co-PVBP)-b-PAA] and [poly(styrene)-co-poly(4-vinyl benzophenone)]-block-poly(ethylene oxide) [(PS-co-PVBP)-b-PEO] were assembled around Au nanoparticles ranging from 12 to 108 nm in diameter. UV irradiation cross-linked the PVBP groups on the polymer to yield particles that withstood extremes of temperature, ionic strength, and chemical etching. Streptavidin was attached to [PS-co-PVBP]-b-PAA-coated particles using the same noncovalent and covalent conjugation protocols used to bind biomolecules to divinylbenzene-cross-linked PS microspheres. We expect that these particles will be useful as plasmonic, highly light-scattering and light-absorbing analogs to fluorescently labeled PS nanospheres. 相似文献
10.
Petar Y. Petrov Christo M. Angelov Galin Petrov Alexi Alexiev Ronald G. Cavell 《Heteroatom Chemistry》2004,15(5):413-417
The reaction of two‐coordinated (trimethylsilylamino)phosphines (Me3Si)2N PE SiMe3 1 (E = N) and 2 (E = CH) with hydroxycarbonyl compounds proceeded with four‐ or five‐member heterocyclization to yield derivatives of oxaphosphetane, oxaphospholanes, and oxaphospholes. The reaction rate depends on the structure of hydroxyketones as well as on the type of the two‐coordinated phosphorus compound in accordance with the polarity of the P=N and P=C bonds. Thus, reaction was completed in 30 min in the case of the ortho carbonyl phenoxy derivatives with the phosphine 1 , but required 2 h in the case of the alkyl hydroxy carbonyls. All reactions with the phosphine 2 took about 24 h. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:413–417, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20033 相似文献