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991.
Q.D. Jiang D. Fujita H.Y. Sheng Z.C. Dong H. Nejoh 《Applied Physics A: Materials Science & Processing》1997,64(6):619-622
Received: 16 August 1996/Accepted: 6 March 1997 相似文献
992.
Guey‐Sheng Liou Sheng‐Huei Hsiao 《Journal of polymer science. Part A, Polymer chemistry》2003,41(1):94-105
A new triphenylamine‐containing aromatic dicarboxylic acid, N,N′‐bis(4‐carboxyphenyl)‐N,N′‐diphenyl‐1,4‐phenylenediamine, was synthesized by the condensation of N,N′‐diphenyl‐1,4‐phenylenediamine with 4‐fluorobenzonitrile, followed by the alkaline hydrolysis of the intermediate dinitrile compound. A series of novel triphenylamine‐based aromatic poly(amine amide)s with inherent viscosities of 0.50–1.02 dL/g were prepared from the diacid and various aromatic diamines by direct phosphorylation polycondensation. All the poly(amine amide)s were amorphous in nature, as evidenced by X‐ray diffractograms. Most of the poly(amine amide)s were quite soluble in a variety of organic solvents and could be solution‐cast into transparent, tough, and flexible films with good mechanical properties. They had useful levels of thermal stability associated with glass‐transition temperatures up to 280 °C, 10% weight‐loss temperatures in excess of 575 °C, and char yields at 800 °C in nitrogen higher than 60%. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 94–105, 2003 相似文献
993.
994.
拓扑遍历与拓扑双重遍历 总被引:24,自引:1,他引:23
令X为紧致度量空间,f:X→X为连续映射,U,V为X的任意非空开集,若{n>0|fn(U)∩V≠ )为正上密度集,则称f拓扑遍历.f拓扑双重遍历意味着f×f拓扑遍历.本文在[2]的基础上进一步讨论拓扑遍历与拓扑双重遍历映射的性质. 相似文献
995.
La0.82Sr0.18MnO3 have been investigated. With grain growth, both an evident decrease of magnetization and the lattice distortions have been simultaneously observed. The phenomenon suggests a structure-coupled change of magnetism in the hole-doped manganese perovskite. 相似文献
996.
ShuJieHOU ChuanChunZOU PingShengLEI DeQuanYU 《中国化学快报》2005,16(5):593-596
Using thioglycosides as donors, trimethylsilyl trifluoromethanesulfonate (TMSOTf) and N-iodosuccinimide(NIS) as promoter, a modified procedure for the glycosylation of spirostanol was developed. A series of saponins were synthesized in mild condition with excellent yields. 相似文献
997.
Ten organotin derivatives with dithiocarbamates of the formulae (4‐NCC6H4CH2)2Sn(S2CNEt2)2 (1), (4‐NCC6H4CH2)2Sn(S2CNBz2)2 (2), (4‐NCC6H4CH2)2Sn[S2CN(CH2CH2)2NCH3]2 (3), (2‐ClC6H4CH2)2 Sn(S2CNEt2)2 (4), (2‐ClC6H4CH2)2Sn(S2CNBz2)2 (5), (4‐NCC6H4CH2)2Sn(Cl)S2CNEt2 (6), (4‐NCC6H4CH2)2Sn(Cl)S2CNBz2 (7), (4‐NCC6H4CH2)2Sn(Cl)S2CN(CH2CH2)2NCH3 (8), (2‐ClC6H4CH2)2 Sn(Cl)S2CNEt2 (9) and (2‐ClC6H4CH2)2Sn(Cl)S2CNBz2 (10) have been prepared. All complexes were characterized by elemental analyses, IR and NMR. The crystal structures of complexes 1 and 10 were determined by X‐ray single crystal diffraction. For complex 1, the central tin atom exists in a skew‐trapezoidal planar geometry defined by two asymmetrically coordinated dithiocarbamate ligands and two 4‐cyanobenzyl groups. In addition, because of the presence of close intermolecular non‐bonded contacts, complex 1 is a weakly‐bridged dimer. In complex 10, the central tin atom is rendered pentacoordinated in a distorted trigonal bipyramidal configuration by coordinating with S atoms derived from the dithiocarbamate ligand. In vitro assays for cytotoxicity against five human tumor cell lines (MCF‐7, EVSA‐T, WiDr, IGROV and M226) furnished the significant toxicities of the title complexes. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
998.
Assembling Synthesis of ZnSe Orthohexagonal Slices through Emulsion Liquid Membrane System of Gas-liquid Transport 总被引:1,自引:0,他引:1
LuLIU QingShengWU YaPingDING HuaJieLIU 《中国化学快报》2005,16(3):375-378
Orthohexagonal slices assembled by ZnSe quantum dots were synthesized through emulsion liquid membrane system. These orthohexagonal slices were 1.5-3.5 μm in side length and were self-assembled by ZnSe quantum dots of 2-3 nm. It was proposed the surfactant molecules on ZnSe quantum dots played a key role in the self-assembly process. 相似文献
999.
Chun‐Hsiung Chien Yu‐Hsu Chang Chih‐Pin Tsai Chih‐Wei Peng Lung‐Shen Wang Pei‐Sun Sheng Chi‐Young Lee Hsin‐Tien Chiu 《中国化学会会志》2006,53(2):287-292
Black solid precursors obtained from reactions between MCl5 (M = Nb, Ta) and alkyllithiums, n‐butyllithium (nBuLi) and ethyllithium (EtLi), in tetrahydrofuran (THF) were heat treated under vacuum at 673–973 K to form nano‐sized particles (20–100 nm in diameter) of lithium niobate (LiNbO3) and lithium tantalate (LiTaO3). Stoichiometry of the reactants is critical and affects the phases of the products. Based on the volatile byproducts detected, a reaction pathway involving the activation of THF by alkyllithiums is proposed to be important for the formation of LiNbO3 and LiTaO3 precursors. 相似文献
1000.
Electroluminescent porous Si (PS) diodes exhibit various useful functions under a high-electric field. The experimental PS diodes are composed of thin semitransparent metal films, PS layers (about 500 nm thick in minimum), p- or n-type Si substrates and ohmic back contacts. Definite nonlinear electrical behavior (negative resistance and nonvolatile bistable memory effects) and cold electron emission phenomena appear in these PS diodes associated with the EL emission. Both the negative resistance and memory effects are related to the charging of Si nanocrystallites by field-induced carrier injection. The electron emission observed in the PS diodes formed on n+–Si substrates is caused by hot electrons tunnelling through the top contact. By an appropriate structural control of PS, the effective drift length under a high-field conduction is significantly increased, and then electrons are emitted ballistically. These functions reflect the activity of PS as a nanocrystalline confined system. 相似文献