全文获取类型
收费全文 | 101篇 |
免费 | 3篇 |
国内免费 | 1篇 |
专业分类
化学 | 86篇 |
数学 | 2篇 |
物理学 | 17篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2020年 | 2篇 |
2019年 | 5篇 |
2017年 | 1篇 |
2016年 | 4篇 |
2015年 | 7篇 |
2014年 | 3篇 |
2013年 | 3篇 |
2012年 | 3篇 |
2011年 | 5篇 |
2010年 | 1篇 |
2009年 | 6篇 |
2008年 | 8篇 |
2007年 | 7篇 |
2006年 | 2篇 |
2005年 | 9篇 |
2004年 | 4篇 |
2003年 | 1篇 |
2002年 | 2篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1987年 | 1篇 |
1922年 | 1篇 |
排序方式: 共有105条查询结果,搜索用时 0 毫秒
1.
The total synthesis of an alkylcitrate secondary metabolite from the fungi Trichoderma viride is described. An ester dienolate [2,3]-Wittig rearrangement and a S. Julia-Kocienski olefination served as key C/C-connecting transformations. The highly convergent synthesis consists of a longest linear sequence of 17 steps. 相似文献
2.
3.
[reaction: see text] Nuclear amination of p-hydroquinones with primary aromatic amines was catalyzed by fungal laccases (EC 1.10.3.2) from Trametes spec. and Myceliophthora thermophila. This is the first report of laccase-catalyzed synthesis of aminoquinones. Incubation of two compounds with laccase in the presence of oxygen resulted in the formation of the corresponding monoaminated or diaminated quinones. No hydroquinonoids were formed. Observed differences in the reaction courses for different p-hydroquinones and aromatic amines with different laccases are discussed. 相似文献
4.
Structural transitions as determinants of the action of the calcium-dependent antibiotic daptomycin 总被引:14,自引:0,他引:14
Daptomycin is a cyclic anionic lipopeptide antibiotic recently approved for the treatment of complicated skin infections (Cubicin). Its function is dependent on calcium (as Ca2+). Circular dichroism spectroscopy indicated that daptomycin experienced two structural transitions: a transition upon interaction of daptomycin with Ca2+, and a further transition upon interaction with Ca2+ and the bacterial acidic phospholipid, phosphatidyl glycerol. The Ca2+-dependent insertion of daptomycin into model membranes promoted mild and more pronounced perturbations as assessed by the increase of lipid flip-flop and membrane leakage, respectively. The NMR structure of daptomycin indicated that Ca2+ induced a conformational change in daptomycin that increased its amphipathicity. These results are consistent with the hypothesis that the association of Ca2+ with daptomycin permits it to interact with bacterial membranes with effects that are similar to those of the cationic antimicrobial peptides. 相似文献
5.
6.
Silicone breast implants are used for breast augmentation and breast reconstruction. The issues of concern associated with such implants are: (a) the quality control of each implant before implantation, and (b) the detection of implant bleeding after implantation. We have studied the use of the Nuclear Magnetic Resonance-MObile Universal Surface Explorer (NMR-MOUSE) for the nondestructive testing of (a) the quality of implant shells, and (b) changes in implant gel due to leakage of body fluid into the implant. Depth profiles measured nondestructively through implant shells at different positions of each implant by the Profile NMR-MOUSE assured good reproducibility of the quality and thickness of different shell layers. The leakage of implants upon rupture was mimicked by observing changes in the transverse NMR relaxation time of the implant gel upon ingress of physiological saline solution and safflower oil through the rupture. Results demonstrate that nondestructive testing with unilateral NMR is a potential method for use in the quality control of implants and for the screening of implants for rupture after implantation. 相似文献
7.
8.
Cíntia Salomão Pinto Zarth Andreas Koschella Annett Pfeifer Susann Dorn Thomas Heinze 《Cellulose (London, England)》2011,18(5):1315-1325
The homogeneous conversion of cellulose dissolved in N-methyl-2-pyrrolidone/LiCl and 1-N-butyl-3-methylimidazolium chloride with N-methyl-2-pyrrolidone, ε-caprolactam, N-methyl-ε-caprolactam, and N-methyl-2-piperidone in the presence of p-toluenesulphonic acid chloride was studied. Depending on the reaction conditions, novel cellulose esters with degree of substitution
(DS) values ranging from 0.12 to 1.17 could be prepared. The structure of the amino group containing cellulose esters was
elucidated by elemental analysis, FTIR- and NMR spectroscopy. NMR spectroscopy revealed an almost complete esterification
of position 6 of the anhydroglucose unit at DS of 1. The conversion can be conducted between room temperature and 40 °C, while
side-reactions became predominant at 60 °C. Starting with DS of 0.24, the samples were soluble both in water and dimethyl
sulphoxide. The derivatives described are capable of forming polyelectrolyte complexes. The samples were stable at room temperature
in aqueous solution at pH 2 and 7. Lower viscosities were found for samples with higher DS in aqueous solution at comparable
molar mass. 相似文献
9.
Scope and limitations of the Pd(II)-catalyzed cycloisomerization of functionalized 1,5-hexadienes have been studied. In situ NMR experiments indicate a challenging competition between various reaction pathways. A careful balance between substrate structure, nature of the precatalyst, and reaction conditions was required to gain access to a useful building block for sesquiterpene total synthesis. 相似文献
10.
Dr. Nicolai Wagner Milena Schuhmacher Annett Lohmann Dr. André Nadler 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(68):15483-15487
Photorelease of caged compounds is among the most powerful experimental approaches for studying cellular functions on fast timescales. However, its full potential has yet to be exploited, as the number of caged small molecules available for cell biological studies has been limited by synthetic challenges. Addressing this problem, a straightforward, one-step procedure for efficiently synthesizing caged compounds was developed. An in situ generated benzylic coumarin triflate reagent was used to specifically functionalize carboxylate and phosphate moieties in the presence of free hydroxy groups, generating various caged lipid metabolites, including a number of GPCR ligands. By combining the photo-caged ligands with the respective receptors, an easily implementable experimental platform for the optical control and analysis of GPCR-mediated signal transduction in living cells was developed. Ultimately, the described synthetic strategy allows rapid generation of photo-caged small molecules and thus greatly facilitates the analysis of their biological roles in live cell microscopy assays. 相似文献