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排序方式: 共有117条查询结果,搜索用时 31 毫秒
1.
Diana C. Skigin Miriam L. Gigli Marina E. Inchaussandague Néstor E. Bonomo Claudio I. Valencia 《International Journal of Infrared and Millimeter Waves》1993,14(6):1323-1339
Theoriginal and theenhanced Maxwell-Garnett estimates for the permittivity of a particulate medium are applied to the reflection of light by a composite dielectric slab. The reflection coefficients for incident s and p polarizations are calculated and some curves are plotted and discussed. 相似文献
2.
G. Balducci L. Bencivenni G. De Rosa R. Gigli B. Martine S.Nunziante Cesaro 《Journal of Molecular Structure》1980
The infrared and Raman spectra of some cyclopentadienyl compounds of the transition metals, namely Ti(C5H5)Cl3 and M(C5H5)2Cl2 (M = Ti, Zr and Hf), are reported and discussed. The infrared spectra of the gaseous species isolated in argon matrices at 10 K provide structural information about the single molecules. Particular attention has been paid to the low-frequency region in order to achieve more reliable assignments for the internal-rotation modes. The structural data and the fundamental frequencies derived from the spectra are employed in a calculation of the thermodynamic functions for these compounds in the ideal gas state. 相似文献
3.
Gómez-Balderas R Raffa DF Rickard GA Brunelle P Rauk A 《The journal of physical chemistry. A》2005,109(24):5498-5508
A systematic study of the binding motifs of Cu(II) and Cu(I) to a methionine model peptide, namely, N-formylmethioninamide 1, has been carried out by quantum chemical computations. Geometries of the coordination modes obtained at the B3LYP/6-31G(d) level of theory are discussed in the context of copper coordination by the peptide backbone and the S atom of a methionine residue in peptides with special emphasis on Met35 of the amyloid-beta peptide (Abeta) of Alzheimer's disease. The relative binding free energies in the gas phase, DeltaG(g), are calculated at the B3LYP/6-311+G(2df,2p)//B3LYP/6-31G(d) level of theory, and the solvation affects are included by means of the COSMO model to obtain the relative binding energies in solution, DeltaG(aq). A free energy of binding, DeltaG(aq) = -19.4 kJ mol(-1), relative to aqueous Cu(II) and the free peptide is found for the most stable Cu(II)/Met complex, 12. The most stable Cu(I)/Met complex, 23, is bound by -15.6 kJ mol(-1) relative to the separated species. The reduction potential relative to the standard hydrogen electrode is estimated to be E degrees (12/23) = 0.41 V. On the basis of these results, the participation of Met35 as a low affinity binding site of Cu(II) in Abeta, and its role in the redox chemistry underlying Alzheimer's disease is discussed. 相似文献
4.
Tedesco E Della F Favaretto L Barbarella G Albesa-Jové D Pisignano D Gigli G Cingolani R Harris KD 《Journal of the American Chemical Society》2003,125(40):12277-12283
The "rigid-core" material 3,5-dimethyl-2,3'-bis(3-methylthiophene)-dithieno[3,2-b:',3'-d]thiophene-4,4-dioxide (DTTOMe4) has the highest photoluminescence ever reported for thiophene-based molecules in the solid state. We report the structure of this material, determined directly from powder X-ray diffraction data using the Genetic Algorithm method for structure solution, followed by Rietveld refinement, and the structural properties are discussed in relation to the structures of the corresponding subsystems DTTO and DTTOMe. While the crystal structures of the latter compounds contain cofacial dimers, the crystal structure of DTTOMe4 comprises layers of molecules aligned in an antiparallel fashion. Intermediate neglect of differential overlap with single configuration interaction (INDO/SCI) calculations on the intermolecular interactions in the three crystal structures show that the different solid-state photoluminescence efficiencies of DTTOMe4, DTTOMe, and DTTO cannot be correlated with the different types of dipole-dipole alignment in the solid state. Instead, photoluminescence efficiencies correlate well with the rate of formation of nonradiatively decaying charge-transfer pairs upon photoexcitation. Because of larger intermolecular distances in DTTOMe4, the photoluminescence is less effectively quenched by charge-transfer processes than in DTTOMe and DTTO. 相似文献
5.
Raganato MF Vitale V Della Sala F Anni M Cingolani R Gigli G Favaretto L Barbarella G Weimer M Görling A 《The Journal of chemical physics》2004,121(8):3784-3791
Modifications of the optical properties of dimethyl-dithienothiophenes due to the oxygen functionalization of the central sulfur atom are investigated. We have measured the absorption, photoluminescence (PL) and PL excitation spectra, the PL quantum efficiencies, and the PL decay times. These experimental results are interpreted and compared with first-principles time-dependent density-functional theory calculations, which predict, for the considered systems, excitation and emission energies with an accuracy of 0.1 eV. It is found that the oxygenation strongly changes optical and photophysical properties. These effects are related to the modifications of the energetically lowest-unoccupied molecular orbital and the energetically second highest occupied one, which change the relative position of the two lowest singlet and triplet excited states. 相似文献
6.
The thermal functions S0T, -(G0T-H0O)/T and (H0T-H0O) have been calculated from structural and spectroscopic data for the gaseous organometallics C5H5BeX (X = Cl, Br and BH4), C5H5MX3 (M = Ti and Ge; X = Cl, Br and I) and CH3TiX3 (X = Cl, Br and I). The rotational barriers of the C5H5 and CH3 groups have been evaluated and discussed. 相似文献
7.
Nicola Gigli 《Geometric And Functional Analysis》2012,22(4):990-999
We prove existence of optimal maps in non branching spaces with Ricci curvature bounded from below. The approach we adopt makes no use of Kantorovich potentials. 相似文献
8.
A. GabrielliI. D?Antone F.M. GiorgiI. Lax M. LolliR. De Leo G. De RobertisM. Foresta F. LoddoA. Ranieri G. CosentinoP. Finocchiaro A.D. PappalardoR. Fonte C. CalviniP. Musico P. OttonelloF. Cusanno F. GaribaldiT. Gigli F. GioveB. Maraviglia F. MeddiA. Rivetti 《Nuclear Physics B - Proceedings Supplements》2011,215(1):165-167
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