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排序方式: 共有406条查询结果,搜索用时 185 毫秒
401.
A novel palladium-catalyzed allylation of H3PO2 with allylic alcohols is described. The phosphorus-carbon bond-forming reaction produces allylic-H-phosphinic acids and water, in the absence of additives. Primary H-phosphinic acids are obtained in excellent yields, whereas secondary H-phosphinic acids react sluggishly. A reusable polymer-supported catalyst is also described. The reaction provides an environmentally sound approach to H-phosphinic acids. 相似文献
402.
Representative organic vapors have been introduced into the flowing afterglow of a low power (<5 W) dc-glow discharge, coupled to a quadrupole mass spectrometer. When a positive bias was applied to the ion sampling orifice, the very surprising result was that molecular mass spectra were obtained with a high sensitivity. When a negative bias was applied to the ion sampling orifice, fragmentation of the analyte was observed with an increase in the extent of ion dissociation as the voltage was increased. The breakdown pattern is compound-specific and would be useful in confirming the identity of an unknown sample. When combined with chromatographic separation, the FFGD-MS technique could be used for chemical speciation studies at the sub-picogram level. 相似文献
403.
Ibrahim Narin Salih Sarioglan Beril Anilanmert Hayati Sari 《Journal of solution chemistry》2010,39(10):1582-1588
The pK
a constants and relative abundances of unionized and ionized forms of Montelukast sodium {the sodium salt of 2-[1-[[(1R)-1-[3-[2-(7-chloroquinolin-2-yl)ethenyl] phenyl]-3-[2-(2-hydroxypropan-2-yl)phenyl]propyl]sulfanylmethyl]cyclopropyl]acetic
acid} and Levodropropizine {(2S)-3-(4-phenylpiperazin-1-yl)propane-1,2-diol} were determined potentiometrically from measurements at various pHs. These determinations
were in order to relate their pK
a values with their bioavailability and to provide chemical data to be used in their analysis. 相似文献
404.
405.
Erick M. Larramendi Z-B Karla Gutiérrez Osvaldo de Melo Ulrike Woggon Detlef Schikora Klaus Lischka 《Journal of Crystal Growth》2010,312(11):1807-1812
The use of a selenium–tellurium (SeTe) mixed source in the isothermal close space sublimation growth of CdSe epilayers is considered. The epitaxial growth was performed in flowing helium by sequential exposures of the substrate to vapors of the mixed SeTe source and elemental cadmium at temperatures within 350–410 °C. In spite of the mixed source (proposed to decrease the partial pressure of Se), tellurium incorporation was small and CdSexTe(1−x) (x∼0.98) epilayers were obtained. X-ray diffraction reciprocal space mapping shows the existence of hexagonal inclusions mainly on the (1 1 1) facets of the cubic phase. Material deposition on areas of the graphite crucible exposed to the sources, contamination of the Cd source and large growth rates suggest the existence of a selenium transport process via graphite. This transport might be the result of the combination of selenium deposition on graphite with a subsequent activated desorption of selenium under cadmium exposure. It affects Cd source purity and growth kinetic bringing on a modification of the usual atomic layer deposition regimen; however, a reproducible growth rate of the epilayers was obtained. 相似文献
406.
Sanhueza Luis Garrido Karla Celis Freddy García Macarena Cáceres Cesar Moczko Ewa Díaz Ramiro J. Aguirre María García Camilo 《Journal of Solid State Electrochemistry》2023,27(6):1511-1521
Journal of Solid State Electrochemistry - Screen-printed electrodes (SPEs) have the advantage of being considered electrochemical cells that can be implemented in portable sensor applications. With... 相似文献