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排序方式: 共有2001条查询结果,搜索用时 46 毫秒
991.
992.
Isabelle F. Clémençon 《Tetrahedron》2007,63(35):8665-8669
The combination of multicomponent condensations with post-condensation dipolar cycloaddition reactions provides a useful route to densely functionalized oxazoles and tetrazoles in just two synthetic steps. 相似文献
993.
We present a new result on the K+→π+π0γ decay measurement using stopped kaons. The best fit to the decay spectrum comprised of 10 k events gives a branching ratio
for the direct photon emission of [3.8±0.8 (stat)±0.7 (syst)]×10-6 in the π+ kinetic energy region of 55 to 90 MeV. This result has been obtained with the assumption that there is no component due to
interference with the inner bremsstrahlung.
PACS 13.20.Eb, 14.40.Aq 相似文献
994.
995.
T. Käämbre L. Qian J.-E. Rubensson J.-H. Guo C. Såthe J. Nordgren J.-P. Palmqvist U. Jansson 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):357-360
The interaction of oxygen with C60 molecules was studied on a C60 film which had been exposed simultaneously to oxygen and UV-light for 190 hours, producing an approximately C60O1 stoichiometry in the bulk of the sample. C K-edge and O K-edge NEXAFS (using total fluorescence yield detection) and resonant
X-ray inelastic scattering (RIXS) spectra from the sample film were measured and the C K-edge data were compared to the spectra
from pristine C60 as reference. The C K-edge absorption and emission spectral profiles of the oxygen-doped sample are similar to those of the
C60 reference, suggesting that cage breaking of C60 under these conditions, if any, is negligible. However, the redistribution of intensities in the spectra indicates changes
in the occupancies of different molecular orbitals, possibly due to changes in electron density upon reaction. Similarities
of the O K-edge soft X-ray emission (SXES) spectra to several small oxygen-containing molecules is being discussed in terms
of bonding models.
Received 4 December 2000 相似文献
996.
997.
Higgs boson production with subsequent decay to photons was searched for in the data collected by the DELPHI detector at centre-of-mass energies between 183 GeV and 209 GeV, corresponding to a total integrated luminosity of nearly 650 pb-1. No evidence for a signal was found, and limits were set on h
0
Z
0 and h
0
A
0 production with h
0 decay to photons. These results were used to exclude regions in the parameter space of fermiophobic scenarios of Two Higgs Doublet Models. 相似文献
998.
The preparation of diastereomerically pure cyclopropanoid muramyldipeptide analogues from suitable substituted cyclopropylamines is described. 相似文献
999.
CUI Xiao-bing ZHENG Shou-tian SUN Yan-qiong YANG Guo-yu ** . Coordination Hydrothermal Chemistry Group State Key Laboratory of Structural Chemistry Fujian Institute of Research on the Structure of Matter Chinese Academy of Sciences Fuzhou P. R. China . State Key Laboratory of Coordination Chemistry Nanjing University Nanjing P. R. China 《高等学校化学研究》2004,(3)
IntroductionBasedonarelativelylargenumberofdifferenttypesofbuildingblockswhichcorrespondtopolyhe dron {VOx} (x =4 ,5 ,6 ) ,polyoxovanadatesshowanextraordinaryvarietyofstructures ,suchascage ,basket ,belt ,ballandbarrelstructures[1— 5] .Further more,these polyoxovanadatesexhibita pronouncedtendencytoformcage likestructureswhichmayen capsulateneutralmoleculesaswellasionicguests ,afeaturesharedbysomeisopolyanionssuchas [V18O4 2·(H2 O) ]12 - [6 ] ,[H4 V18O4 2 (X) ]9- (X =Cl- ,Br- ,I- ) [2 ,… 相似文献
1000.
We present the final results of the search for stellar gravitational collapses obtained by the MACRO experiment. The detector was active for a stellar collapse search for more than 11 years and it was sensitive to collapses occurring all over in our galaxy for 8.6 years. A real time system for a prompt recognition of neutrino bursts was developed and was operating on-line for almost the whole life of the experiment. No signal compatible with a neutrino burst from a galactic supernova was observed.Received: 18 February 2003, Revised: 25 March 2004, Published online: 14 September 2004 相似文献