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排序方式: 共有120条查询结果,搜索用时 203 毫秒
1.
Alvarez Carrillo Pavel Anselmo Roselli Lucia Reis Peixoto Frej Eduarda Asfora de Almeida Adiel Teixeira 《Annals of Operations Research》2022,314(2):377-392
Annals of Operations Research - The aim of this paper is to solve an agricultural technology packages selection problem by considering multiple dimensions which influence a maize producer’s... 相似文献
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Wijkens P Jastrzebski JT van Der Schaaf PA Kolly R Hafner A van Koten G 《Organic letters》2000,2(11):1621-1624
A general method for the functionalization of Si-Cl terminated carbosilane dendritic molecules via organolithium or organomagnesium reagents is described. Quantitative exchange of the bromine atoms of 4-bromophenyl-functionalized dendrimers affords polylithiated species that are valuable starting materials for further functionalization, e.g., into pyridyl alcohols. The latter were successfully applied as catalyst precursors in a ruthenium-mediated ring-closure metathesis reaction. 相似文献
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Gordeev SN Zhukov AA de Groot PA Jansen AG Gagnon R Taillefer L 《Physical review letters》2000,85(21):4594-4597
We report on transport measurements of YBa 2Cu 3O (7-delta) single crystals with different oxygen contents in the geometry B, J ||ab (J perpendicularB). Our data show that the vortices become confined between the Cu-O planes below a well-defined temperature at which the effective size 2xi of the vortex core is approximately equal to the period of the Cu-O layers. This confinement strongly increases the vortex liquid freezing temperature. A new melting line is found separating a vortex liquid and a smectic phase, which shows an oscillatory field dependence reflecting differences between commensurate and incommensurate smectic states. 相似文献
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Jos Maximiano F. Pinheiro Jr. Paulo H.R. Peixoto Celso P. de Melo 《Chemical physics letters》2008,463(1-3):172-177
We have used ab initio methods to confirm the existence of an inversion in the photoinduced intramolecular electron transfer in large conjugated pyridinium betaines, by examining compounds where an imidazole ring and a pyridinic group are connected by polyenic chains of increasing size. As these intermediary conjugated bridges get longer, an unusual net charge transfer is observed. The conjugated chain becomes a channel for the photoinduced electronic density flow, and the amount of charge at the donor and acceptor groups is reduced, while an inversion in the spatial localization of the frontier orbitals occurs. We discuss the corresponding implications on the nonlinear optical, photochemical and solvatochromic properties of these molecules. 相似文献
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Ana R. Almeida Rui M.B. Carrilho Andreia F. Peixoto Artur R. Abreu Artur Silva Mariette M. Pereira 《Tetrahedron》2017,73(17):2389-2395
Different families of new amino compounds were efficiently synthesized, through optimized sequential processes, involving rhodium catalyzed hydroformylation as the key step. The selection of appropriate hydroformylation catalytic systems and reaction conditions allowed obtaining aldehydes derived from several n-alkyl olefins, cholest-4-ene and 3-vinyl-1H-indole, which were subsequently transformed, in one-pot, in to α-amino acids via hydroformylation/Strecker reaction, and in to tertiary amines via hydroaminomethylation, with excellent yields. 相似文献
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Ming Xia LI Yan Ming WANG Ru Ru CHEN* Research Institute of Elemento-Organic Chemistry Nankai University Tianjin Pittsburgh University Medical Center Pittsburgh PA U. S. A 《中国化学快报》2001,(6)
The chiral diols ((,(,((,((-Tetraaryl-1,3-dioxolane-4,5-dimethanols) have been used for the formation of cyclic titanates and similar derivatives of Mg, Al and Zr. These complexes of oxophilic metal centers were employed in catalytic and stiochiometric enantioselective reactions such as enantioselective addition reactions of carbon-centered nucleophiles to aldehydes1, [2+2] cycloadditions2, and Diels-Alder reactions3. So far, the two hydrogen atoms of all this type of diols are in trans form… 相似文献