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21.
Magnetic dipole and electric quadrupole responses of elliptic quantum dots in magnetic fields 总被引:1,自引:0,他引:1
E. Lipparini Ll. Serra A. Puente 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(3):409-415
The magnetic dipole (M1) and electric quadupole (E2) responses of two-dimensional quantum dots with an elliptic shape are
theoretically investigated as a function of the dot deformation and applied static magnetic field. Neglecting the electron-electron
interaction we obtain analytical results which indicate the existence of four characteristic modes, with different B-dispersion of their energies and associated strengths. Interaction effects are numerically studied within the time-dependent
local-spin-density and Hartree approximations, assessing the validity of the non-interacting picture.
Received 29 November 2001 Published online 6 June 2002 相似文献
22.
Verma S Ghosh A Das A Ghosh HN 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(12):3458-3464
Exciton-coupled charge-transfer (CT) dynamics in TiO(2) nanoparticles (NP) sensitized with porphyrin J-aggregates has been studied by femtosecond time-resolved transient absorption spectroscopy. J-aggregates of 5,10,15-triphenyl-20-(3,4-dihydroxyphenyl) porphyrin (TPPcat) form CT complexes on TiO(2) NP surfaces. Catechol-mediated strong CT coupling between J-aggregate and TiO(2) NP facilitates interfacial exciton dissociation for electron injection into the conduction band of the TiO(2) nanoparticle in pulse width limited time (<80 fs). Here, the electron-transfer (<80 fs) process dominates over the intrinsic exciton-relaxation process (J-aggregates: ca. 200 fs) on account of exciton-coupled CT interaction. The parent hole on J-aggregates is delocalized through J-aggregate excitonic coherence. As a result, holes immobilized on J-aggregates are spatially less accessible to electrons injected into TiO(2) , and thus the back electron transfer (BET) process is slower than that of the monomer/TiO(2) system. The J-aggregate/porphyrin system shows exciton spectral and temporal properties for better charge separation in strongly coupled composite systems. 相似文献
23.
Oleg L. Berman Yurii E. Lozovik David W. Snoke Rob D. Coalson 《Physica E: Low-dimensional Systems and Nanostructures》2006,34(1-2):268
The theory of what happens to a superfluid in a random field, known as the “dirty boson” problem, directly relates to a real experimental system presently under study by several groups, namely excitons in coupled semiconductor quantum wells. We consider the case of bosons in two dimensions in a random field, when the random field can be large compared to the repulsive exciton–exciton interaction energy, but is small compared to the exciton binding energy. The interaction between excitons is taken into account in the ladder approximation. The coherent potential approximation (CPA) allows us to derive the exciton Green's function for a wide range of the random field strength, and in the weak-scattering limit CPA results in the second-order Born approximation. For quasi-two-dimensional excitonic systems, the density of the superfluid component and the Kosterlitz–Thouless temperature of the superfluid phase transition are obtained, and are found to decrease as the random field increases. 相似文献
24.
Gustavo A. Narvaez Lixin He Gabriel Bester Alex Zunger 《Physica E: Low-dimensional Systems and Nanostructures》2006,32(1-2):93
We show how an atomistic pseudopotential plus many-body configuration interaction theory can address the main spectroscopic features of self-assembled dots including, excitons, trions, biexcitons, fine-structure, charging spectra as well as electric-field dependence of entanglement in dot molecules. 相似文献
25.
26.
L. A. Gribov 《Journal of Structural Chemistry》2006,47(2):201-205
A model is proposed describing the dynamics of radiationless transitions in the energy zones corresponding to excited electronic states in molecular crystals. In this model, the migration effect is explicitly reflected, which initially appears under pulse excitation of the systems with a periodical structure of a density distribution of states in separate parts of molecular crystals. 相似文献
27.
We have analyzed a linear molecular chain with exciton excitations when the number of excitons is not conserved. The dispersion law depends on two independent variables and it is surfaced in a 3D plot. The same conclusion is valid for the concentrations of excitons and exciton pairs. As it was expected, physical characteristics of the finite chain depend on spatial coordinates. All results are compared to the corresponding results of an infinite chain. 相似文献
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29.
Abstract A brief survey of our studies of free and self-trapped excitons (FE and STE) in alkali halide crystals under hydrostatic pressure up to 12.5 kbar at 4.2–140 K is presented. Main attention is paid to the following effects observed: (1) the strong coupling of three energy levels of FE in CsI revealing itself as an exciton analog of pressure-scanned Fermi resonance; (2) emergence of a new emission band of STE in CsI under pressure; (3) a large pressure shift of the thermal quenching curve for STE emission in NaCl. 相似文献
30.
Abstract In BaFCl two types of F centres can be produced, where the electron occupies a Cl? vacancy [F(Cl?)-centres] or an F? vacancy [F(F?)-centres]. When producing F(F?)-centres the simultaneous production of F(Cl?)-centres cannot be avoided. Both ESR spectra overlap strongly. The ENDOR spectra contain very many lines of both centres and have a very complicated angular dependence. It is shown that the angular dependence of the ENDOR spectra of both F centres can be measured separately by applying a double ENDOR technique (called also Triple Resonance). The ratio of the signal heights of the ENDOR lines compared to the double ENDOR lines is characteristic for the neighbour shell to which the nuclei involved belong. The use of this effect for the analysis of the spectra and its explanation are discussed. 相似文献