排序方式: 共有35条查询结果,搜索用时 0 毫秒
31.
With several monoenergetic gamma-rays generated at low energy(p,γ)resonant nuclear reactions,the full-energy-peak intrinsic gamma-rays detecting efficiencies of a Φ 76 mm×100mm BGO scintilation detector were measured as below:7%、9%、22% at 17.65、17.23 and 6.13MeV gamma-rays energy,respectiviy. 相似文献
32.
Dr. Jinhu Wei Dr. Liangliang Wu Dr. Hai-Xu Wang Dr. Xiting Zhang Dr. Chun-Wai Tse Dr. Cong-Ying Zhou Dr. Jie-Sheng Huang Prof. Dr. Chi-Ming Che 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(38):16704-16714
Reliable methods for enantioselective cis-dihydroxylation of trisubstituted alkenes are scarce. The iron(II) complex cis-α-[FeII(2-Me2-BQPN)(OTf)2], which bears a tetradentate N4 ligand (Me2-BQPN=(R,R)-N,N′-dimethyl-N,N′-bis(2-methylquinolin-8-yl)-1,2-diphenylethane-1,2-diamine), was prepared and characterized. With this complex as the catalyst, a broad range of trisubstituted electron-deficient alkenes were efficiently oxidized to chiral cis-diols in yields of up to 98 % and up to 99.9 % ee when using hydrogen peroxide (H2O2) as oxidant under mild conditions. Experimental studies (including 18O-labeling, ESI-MS, NMR, EPR, and UV/Vis analyses) and DFT calculations were performed to gain mechanistic insight, which suggested possible involvement of a chiral cis-FeV(O)2 reaction intermediate as an active oxidant. This cis-[FeII(chiral N4 ligand)]2+/H2O2 method could be a viable green alternative/complement to the existing OsO4-based methods for asymmetric alkene dihydroxylation reactions. 相似文献
33.
鲁又文 《纯粹数学与应用数学》1994,(2)
设Ω为En中的无界,连通区域.在Ω×(0,∞)上考虑抛物型方程:设,B满足结构条件:设存在和,使对任何ρ0>ρ1>0:设u是方程的广义解,并且如果u在Ω×(0,T)为有界,那么u+≤0. 相似文献
34.
Trudinger和Gilbarg—Trudinger对椭园型方程的广义解推广了古典的最大值原理,唯一性定理也有新发展。现在我们把结果推广到一致抛物型方程的第一边值问题。 设Ω是n维欧氏空间E~n中的有界域,Ω为其边界,Q=Ω×(O,T),T是有限值。用(Q)记空间W_2~1(Q)的子空间,其函数在意义下满足如下边界条件: u(x,0)=0,x∈Ω和u(x,t)=0,x∈Ω,t∈(0,T)。 在Q考虑下面形状的方程 相似文献
35.
考虑一类对角型蜕化椭圆组,证明广义解的有界性和LФ-可积性. 相似文献