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排序方式: 共有355条查询结果,搜索用时 15 毫秒
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Hiller W Brüll A Argyropoulos D Hoffmann E Pasch H 《Magnetic resonance in chemistry : MRC》2005,43(9):729-735
The application of HPLC-NMR for the analysis of a mixture of fatty alcohol ethoxylates (FAEs) is described. The use of the new generation, cryogenically cooled probes is investigated in respect of the sensitivity advantage that they provide. The FAE mixture is separated using liquid chromatography at the critical point of adsorption. The ability of the method to differentiate between the different end groups and the degree of polymerization of the mixture constituents is investigated. Both on-flow and stop-flow HPLC-NMR techniques were used together with two-dimensional NMR spectroscopy. The results are compared with those obtained by using an evaporative light scattering detector for the HPLC. 相似文献
5.
Cédric Kalinski Michael Umkehrer Nadine Jäger Wolfgang Hiller 《Tetrahedron letters》2006,47(12):2041-2044
A combinatorial synthetic route yielding fused tetrazolo[1,5-a]quinoxalines is described. The use of 2-fluorophenylisocyanide in the Ugi-tetrazole reaction (tetrazole-U-4CR) followed by a nucleophilic aromatic substitution (SNAr) affords the tricylic tetrazolo[1,5-a]quinoxaline moiety in good yields and with high diversity. 相似文献
6.
M. Friedrich K. Hiller M. Wiemer T. Geßner D. R. T. Zahn 《Analytical and bioanalytical chemistry》1998,361(6-7):558-559
Basic investigations have been carried out on the characterization of different processing steps in bond preparation using
etched <111> faces of silicon wafers for the incidence of the infrared beam to a multiple internal reflection geometry. The
method is very sensitive to the surface coverage and interface. Surface activation by RCA cleaning yields an increase of water
coverage and a decrease of SiH and CH groups. The detection limit for an oxide layer between silicon wafers has been found
to be about 3 nm.
Received: 18 July 1997 / Revised: 15 August 1997 / Accepted: 19 August 1997 相似文献
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In solvents of different polarities, the lactam-lactim tautomeric equilibrium of isoxazoli-din-3-one is strongly displaced in the direction of the lactam. The lactim form cannot be detected. It has been concluded that there is no connection between the dual chemical behavior of isoxazolidin-3-one and its potassium salt in the alkylation reaction with the equilibrium isomerization of these compounds. It has been shown that the mechanism of alkylation is connected with the structure of the lactam anion. Evidence is given in favor of a mesomeric structure of the anion with the main charge on the nitrogen at which substitution chiefly takes place.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 898–901, July, 1973. 相似文献
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Kolesnikov EM Böttger T Hiller A Junge FW Kolesnikova NV 《Isotopes in environmental and health studies》1996,32(4):347-361
Abstract Peat profiles from the area of the Tunguska explosion epicentre indicate significant carbon and hydrogen isotopic effects which are clearly associated with the zone of the 1908 "catastrophe", and which cannot be attributed to any known terrestrial processes. We explain them with the presence of extraterrestrial matter similar to carbonaceous chondrites or, more probably, to cometary matter. Initial data on nitrogen content and its isotope composition are consistent with the assumption of acid rainfall following the passage and explosion of the Tunguska cosmic body, as is known to have occurred during the Cretaceous-Tertiary boundary. 相似文献
9.
I. V. Turovskii V. T. Glezer L. Ya. Avota Ya. P. Stradyn S. A. Hiller 《Chemistry of Heterocyclic Compounds》1973,9(7):914-916
The protolysis constants of pyridazin-6-one and some of its derivatives have been determined by the spectrophotometric method. The influence of substituents on the value of the protonation constants is discussed.Translated from Khimiya Geterots iklicheskikh Soedinenii, No. 7, pp. 993–995, July, 1973. 相似文献
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