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排序方式: 共有357条查询结果,搜索用时 15 毫秒
91.
引入一个复阶星象函数类S(λ,b,A,B),讨论了函数类的Fekete-Szeg不等式,得到准确结果,推广了一些作者的相关结果,并给出Hadamard卷积在该函数类的Fekete-Szeg不等式上的应用. 相似文献
92.
[reaction: see text] Electrophilic nitration, formylation or bromination of metalated 5-fluoroalkyl-10,20-diphenylporphyrin (fluoroalkyl = CF3, ClCF2CF2, n-C6F13) proceeded with high regioselectivity, exclusively affording corresponding meso-substituted porphyrins, while the iodination reaction mainly took place at the adjacent beta site giving 2-iodo-10-fluoroalkyl-5,15-diphenylporphyrin. Suzuki, Sonogashira, and trifluoromethylation reactions of the obtained 5-bromo-15-fluoroalkyl-10,20-diphenylporphyrins or 2-iodo-10-fluoroalkyl-5,15-diphenylporphyrins could perform smoothly to give the corresponding various meso- or beta-functionalized fluoroalkylated porphyrin derivatives. Accordingly, two meso-to-meso butadiyne-bridged bisporphyrin dimers and two beta-to-beta butadiyne-linked dimeric porphyrins were prepared by the coupling reactions of 5-ethynyl-15-fluoroalkyl-10,20-diphenylporphyrins and 2-ethynyl-10-fluoroalkyl-5,15-diphenylporphyrins, respectively. 相似文献
93.
In this paper, spatial patterns of predator-prey model with cross diffusion are investigated. The Hopf and Turing bifurcation critical line in a spatial domain are obtained by using mathematical theory. Moreover, exact Turing space is given in two parameters space. Our results reveal that cross diffusion can induce stationary patterns, which may be useful to help us better understand the dynamics of the real ecosystems. 相似文献
94.
半环R被称为实半环,若对于任意的n∈N,方程x1^2+…+xn^2=0在R中只有零解:x1=…=xn=0.为了刻画实半环,引入了实理想和极小素理想的概念,利用同余的方法,得到了可减半环类中实半环的结构定理. 相似文献
95.
96.
GAO Xiang HUI Yue-jun XUE Yi-qun FU Yang AO Man WANG Li 《高等学校化学研究》2007,23(2):187-190
Using the young inflorescence segments of Freesia refracta as explants, indirect somatic embryogenesis of somatic cells was induced in a N6 medium supplemented with some exogenous hormones. SDS-polyacrylamide gel electrophoresis(SDS-PAGE) was used for the analysis of soluble proteins produced during the somatic embryogenesis of this plant. There are six polypeptides, which might play some roles in the process of somatic embryo development. Tltree polypeptides(45, 53 and 55 kD) were detected in the stages of embryogenic callus, globular embryoid, and embryoid with coleoptiles, except the embryoid with leaf. One polypeptide( 83 kD) was specific for the stages of embryoid with eoleoptiles and embryoid with leaf. One polypeptide(37 kD) was detected in the first two stages, namely, embryogenic callus and globular embryoid. One polypeptide(35 kD) was regularly synthesized in each stage, from embryogenic callus to embryoid with leaf. 相似文献
97.
Treatment of 5,10,15,20-tetraarylporphyrins (1) with perfluoroalkyl iodides (2) in the presence of Na(2)S(2)O(4)/NaHCO(3) in DMSO-CH(2)Cl(2) at 30-40 degrees C for several hours gives the corresponding 2-perfluoroalkylporphyrins (3). Nucleophilic attack on 3 with dimethyl malonate, diethyl malonate, malonitrile, or cyano acetate (Nu) anion results in the formation of (E)-3-Nu-2-perfuoroalkyl(methylenyl)chlorins. Electrophilic substitution on 3 with NBS or NO(2) affords regioselectively the corresponding 12(or 13)-bromo- and 12,13-dibromo- or nitroporphyrins. 相似文献
98.
Electrochemical polymerization of aniline and 3-methylthiophene has been accomplished in 1-methylimidazium tetrafluoroborate (HMIMBF4) ionic liquid. Homopolymer and copolymers of aniline and 3-methylthiophene were obtained successfully. The copolymer was studied by cyclic voltammetry and electrochemical impedance spectroscopy. The formation of copolymer has been confirmed by FT-IR and UV spectra. The atomic force microscope (AFM) was used for microstructural analysis. Both the homopolymer and the copolymer had the catalytic activity for the hydroquinone. 相似文献
99.
磁头/盘界面超薄气膜挤压效应和动压效应研究 总被引:1,自引:0,他引:1
针对求解磁头/磁盘界面动态气膜力时出现的不易收敛和编程复杂的问题,本文提出了基于PDE工具求解气体润滑的瞬态和稳态雷诺方程的方法,计算了具有不同最小气膜厚度的Tri-pad正压型和Tri-pad负压型浮动块空气轴承在加载和卸载过程中的瞬态和稳态气膜压力分布,求解了作用面上的轴承力,并将2种状态下超薄气膜挤压效应和动压效应对轴承力的影响进行了对比.仿真结果表明:该方法具有足够的求解精度,且收敛速度快,为研究具有复杂磁头形貌特征的超薄气体润滑的动态特性提供了方便、准确的方法. 相似文献
100.
A special two-soliton solution of sine-Gordon equation is obtained by using
the Hirota direct method. It is shown in a mass-centre system how two kinks move and
interact with each other. 相似文献