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排序方式: 共有78条查询结果,搜索用时 15 毫秒
1.
Ortica F Moustrou C Berthet J Favaro G Samat A Guglielmetti R Vermeersch G Mazzucato U 《Photochemistry and photobiology》2003,78(6):558-566
A photophysical and photochemical study of a biphotochromic compound where two naphthopyran units are linked by an acetylene-thiophene-acetylene bridge has been carried out in toluene. Both fluorescence and intersystem crossing to the triplet manifold were found to compete with the photocoloration process. Two photoproducts (transoid-trans and transoid-cis stereoisomers), absorbing at approximately 480 nm and corresponding to the opening of a single photochromic unit, were detected by spectrophotometric analysis after short irradiation time in diluted solution and identified by 1H-nuclear magnetic resonance (NMR) spectroscopy. After prolonged irradiation at 228 K of highly concentrated solutions (up to 3 x 10(-3) mol dm(-3)), two additional isomers, absorbing at approximately 550 nm, were formed. Their NMR spectra indicate the opening of both photochromic units. An interesting effect of selective vibronic excitation was found, showing that the photoreaction is favored at excited vibronic levels to the detriment of the radiative relaxation. 相似文献
2.
Under the action of nucleophile reagents such as water, hydrogen sulfide and sodium borohydride, the saturated azaheterocyclic spirochromenes are opened either on the azaheterocyclic side or on the benzopyran side or on both parts simultaneously. The merocyanines are either partially reduced or decomposed by the sodium borohydride. 相似文献
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5.
Jean Luc Derocque Pierre Appriou Robert Guglielmetti Heinz Dürr 《Journal of mass spectrometry : JMS》1977,12(10):606-618
The mass spectra of 12 benzodithiolic spiropyrans are reported. Their fragmentation pathways have been determined by exact mass and metastable transition measurements. The nature of the fragmentation is strongly dependent upon the position and nature of the substituents. A comparison is made with their photo and thermochemical decompositions. 相似文献
6.
Benzothiazolinic spiropyrans, merocyanines and photomerocyanines, thermally stabilised to a high degree, have been studied by means of Fourier transform 1H and 13C NMR. The results show the polarity of open forms such as merocyanines and photomerocyanines, their trans configuration, the alternation of the electronic density on the dimethine bridge between the ‘benzothiazolinic’ and ‘phenolate’ part of these molecules, and also a favoured configuration when photomerocyanines have an alkoxy or aryloxy group on the 3 position. 相似文献
7.
B. Luccioni-Houzé P. Nakache M. Campredon R. Guglielmetti G. Giusti 《Research on Chemical Intermediates》1996,22(5):449-457
This paper deals with the synthesis of photochromic compounds containing a spin-trap or a spinlabel. Structural assignments are based on NMR studies and the EPR spectrum of the radical species was recorded. The photochromic performance of the compounds was also investigated and the influence of the substituents is discussed. 相似文献
8.
C. Signorini D. Pierroutsakou B. Martin M. Mazzocco T. Glodariu R. Bonetti A. Guglielmetti M. La Commara M. Romoli M. Sandoli E. Vardaci H. Esbensen F. Farinon P. Molini C. Parascandolo F. Soramel S. Sidortchuk L. Stroe 《The European Physical Journal A - Hadrons and Nuclei》2010,44(1):63-69
The interaction of loosely bound (S p = 600 keV) 17F ions with a 208Pb target was studied at E lab = 86 MeV, below the Coulomb barrier, by measuring the differential cross-section for the quasi-elastic scattering and the cross-section for the exclusive breakup process 17F $ \rightarrow$ 16O + p . The small reaction and exclusive breakup cross-sections confirm the small reactivity of this system, even at low energy, and indicates that the 17F small binding energy plays a minor role in the reaction dynamics. 相似文献
9.
Maurel F Aubard J Millie P Dognon JP Rajzmann M Guglielmetti R Samat A 《The journal of physical chemistry. A》2006,110(14):4759-4771
Ab initio and semiempirical quantum mechanical calculations were performed to study the electronic spectra of spiroxazine photochromic compounds as well as the corresponding photoisomers. Ground-state geometries were optimized based on density functional theory (DFT). Excitation energies of the different forms were calculated using the time-dependent density functional theory (TD-DFT) method. Semiempirical calculations including configuration interactions were performed to detail the mechanism of ring opening in excited states. On the basis of the obtained potential energy profile, a complete mechanism of photocoloration able to clarify some experimental findings is provided. A correlation of the experimental quantum yield of photocoloration with the calculated properties as a function of substituent effects is proposed. 相似文献
10.
M.Manuel Oliveira LuisM. Carvalho Corinne Moustrou Andr Samat Robert Guglielmetti AnaM.F. Oliveira‐Campos 《Helvetica chimica acta》2001,84(5):1163-1171
The synthesis and photochromic properties of new 2,2‐diphenyl‐2H‐1‐benzopyrans, fused to an indole moiety, are described. All compounds exhibit photochromic behaviour in solution at room temperature. The heteroanellation effects are variable and depend on the position and geometry of the fused indole moiety. A general bathochromic shift in the spectra of the open forms is observed. The presence of a N‐methyl group prevents the broadening of the absorption spectra and promotes the instability of some photoinduced forms of compounds with the indole moiety fused at the 5,6 positions of the 2H‐1‐benzopyran skeleton. The enhanced photocolouration efficiency in the near‐UV and the kinetics of thermal bleaching indicate that the novel compounds with an indole moiety fused at the 6,7 positions, particularly those with a linked thiophene moiety, are very interesting molecules for applications in the field of variable optical absorption systems. 相似文献