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We study theoretically radio-frequency/gamma-regime double resonance. In calculating the time dependent Mössbauer absorption Floquet states are used, which incorporate both the rf field andthe static splitting of nuclear levels. A novel concise expression results that encompasses all known cases of direct electromagnetic rf excitation. Methods for solving the theory numerically are discussed. Our computer programs are faster andmore flexible than the earlier matrix continued fraction programs. A comparison of time averaged andtime averaged andtime dependent absorption elucidates the role of transverse andlongitudinal rf fields. 相似文献
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Conformations of aliphatic diastereoisomers with vicinal asymmetric centers (2,3-disubstituted butanes and 5,6-disubstituted n-decanes) are discussed in terms of their 13C and, in some cases, 15N chemical shifts and spin-lattice relaxation times. Solvent and protonation effects are explained by conformational changes in the isomers. 相似文献
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J. Schraml V. Chvalovský M. Mägi E. Lippmaa R. Calas J. Dunoguès P. Bourgeois 《Journal of organometallic chemistry》1976,120(1):41-47
29Si and 13C NMR spectra of trimethylsilylbenzenes substituted at different positions by methyl and trimethylsilyl groups were investigated with special reference to steric interactions between the ortho-substituents. The steric effects, as measured by 13C and 29Si chemical shifts, are generally smaller in trimethylsilyl- than in t-butyl-substituted compounds. Both nuclei follow the same general trends in the benzene derivatives. 相似文献
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Thermal degradation of low-density polyethylene (LDPE) in the temperature range from 450 to 525°C has been studied using a sieve-bottom reactor with inert gas as heat-transferring agent bubbled through the PE melt. Temperature dependence of the degradation rate was determined. Full degradation of LDPE into gaseous and wax-like hydrocarbons (alkanes and 1-alkenes) was achieved. Temperature rise and prolonging of the contact time increased the yield of the gaseous hydrocarbons and decreased the molecular weight of the wax-like product. 相似文献
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K. Tamura T. Makino A. TsukazakiM. Sumiya S. FukeT. Furumochi M. Lippmaa C.H. Chia Y. Segawa H. Koinuma M. Kawasaki 《Solid State Communications》2003,127(4):265-269
We have grown nitrogen-doped ZnO (ZnO:N) films by laser molecular-beam epitaxy. The use of lattice-matched ScAlMgO4 substrates prevented the degradation of crystallinity induced by the nitrogen incorporation to the films. Despite this improvement, we have not obtained ZnO:N films which showed p-type conductivity. We studied the optical properties of these ZnO:N films. Donor-acceptor pair (DAP) luminescence was observed. The results indicate the formation of an acceptor state. The energy position of the DAP luminescence is lower than that reported by Look et al. [Appl. Phys. Lett. 81 (2002) 1830]. The DAP luminescence band shifts to lower energy with increasing nitrogen concentration. A photoluminescence recombination possibly due to the free-electron-to-acceptor (FA) transition was observed at temperatures higher than 40 K. The acceptor ionization energy was estimated from the energy position of the FA luminescence to be 266 meV. 相似文献