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排序方式: 共有1477条查询结果,搜索用时 625 毫秒
991.
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993.
In the paper, for the contamination distribution model F(x) = (1-α)F1(x)+αF2(x), the estimates of α and F1 (x) are studied using two different ways when F2 (x) is known and the strong consistency of the two estimates is proved. At the same time the consistency rate of estimate α is also given. 相似文献
994.
主要讨论了具有限时滞的非自治三种群扩散捕食系统的周期解的存在性.方法是运用Yoshizawa型周期解定理的推广,得出该系统至少有一个ω周期解. 相似文献
995.
Xiao Lan LIU* Qing Yan CHENG Xia YANG Zhi Wei MIAO Wei LIU Fang Ming MIAO College of Chemistry Life Science Tianjin Normal University Tianjin 《中国化学快报》2001,(6)
Histidine is known to be an important biological ligand present at the active site of superoxide dismutases (SOD)1-2 and other metalloproteins. It appears to play a crucial role in the coordination chemistry of numerous metalloproteins. The ligand of di(2-benzimidazolyl-methyl)amine (L3) was chosen as the model compound of histidine. This paper reports the synthesis and crystal structure of Zn-L3 complex which is as the model compound of SOD.The complex, Zn(L3)2((ClO4)2(C2H5OH(C32H30N1… 相似文献
996.
ChangXiMIAO MingSHAN 《中国化学快报》2004,15(1):93-96
The incorporation of ZnO into Fe2O3-K2O system increases its activity, enhances its moisture stability and mechanical strength. The origin of the enhancement in activity and moisture stability is discussed in the light of experimental results obtained by BET, XRD, XPS. It was found that the addition of ZnO to Fe2O3-K2O system strengthens the interaction between Fe2O3 and K2O, reduces the formation temperature of KFe11O17 at least by 50℃, and promotes the transformation of Fe^3 to Fe^2 further. 相似文献
997.
998.
The main achievements in our research on the physical phenomena of the excited-state nonlinear absorption in a molecular system and its applications in photonic technology are described. In the first part of this paper, some energy-level models and rate-equations are used to explain various mechanisms of the excited-state nonlinear absorption under differ-ent conditions, such as reverse saturable absorption caused by the triplet and/or the singlet excited-state absorption; saturable absorption due to the first and/or the second singlet excited-state absorption; and the excited-state nonlinear absorption induced by two-photon absorption. The experimental results for metal-organic and C60 materials irradiated by ps and ns laser pulses are consistent with the simulated curves of the transmittance versus flu-ences. In the second part, the applications of excited-state nonlinear absorption in photonic techniques including optical bistability, optical switching, optical limiting, optical modula-tion, optical logic and optical storage are introduced. The working principles of the photonic devices based on the excited-state nonlinear absorption are presented. The experimental characteristic curves are found in good agreement with the theoretical simulations for these devices. 相似文献
999.
信息能力国际比较的主成分分析法 总被引:32,自引:1,他引:31
本文利用主成分分析方法对世界主要国家的信息能力进行了排序比较 ,并对所得结果进行了简要的分析。 相似文献
1000.