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91.
The energies and lifetimes of the image potential resonances at the ? point on the Cu(110), Ag(110), and Au(110) surfaces are studied, and the energies of the image potential states on the Pd(110) surface are analyzed. It is shown that every quantum number n corresponds to a pair of image potential states (resonances) n + and n ? at the ? point. The average energy of a pair of eigenstates (resonances) at n ≥ 2 is well described by the formula ē n = (E n+ + E n?) = E 0 ? (0.85 eV)/(n + δ)2, where δ is the quantum defect, E 0 = (1/2m e )(?π/a)2, and a is the lattice parameter. The splitting energy of a pair of eigenstates (resonances) obeys the law ΔE n = E n+ — E n? ∝ n ?3. The lifetimes τ n± of image potential resonances are proportional to n 3. 相似文献
92.
We propose a first-principles method for evaluations of the time-dependent electron distribution function of excited electrons in the conduction band of semiconductors. The method takes into account the excitations of electrons by an external source and the relaxation to the bottom of the conduction band via electron-phonon coupling. The methods permit calculations of the non-equilibrium electron distribution function, the quasi-stationary distribution function with a steady-in-time source of light, the time of setting of the quasi-stationary distribution and the time of energy loss via relaxation to the bottom of the conduction band. The actual calculations have been performed for titanium dioxide in the anatase structure and zinc oxide in the wurtzite structure. We find that the quasi-stationary electron distribution function has a peak near the bottom of the conduction band and a tail whose maximum energy rises linearly with increasing energy of excitation. The calculations demonstrate that the relaxation of excited electrons and the setting of the quasi-stationary distribution occur within a time of no more than 500?fs for ZnO and 100?fs for anatase. We also discuss the applicability of the effective phonon model to energy-independent electron-phonon transition probability. We find that the model only reproduces the trends in the change of the characteristic times whereas the precision of such calculations is not high. The rate of energy transfer to phonons at the quasi-stationary electron distribution also have been evaluated and the effect of this transfer on the photocatalysis has been discussed. We found that for ZnO this rate is about five times less than in anatase. 相似文献
93.
D. G. Gromov S. A. Gavrilov E. N. Redichev I. S. Chulkov M. Y. Anisimov S. V. Dubkov S. I. Chulkov 《Applied Physics A: Materials Science & Processing》2010,99(1):67-71
The process of melting with consequent disintegration into droplets of various thickness Au thin films has been studied. An
unexpected character of the melting–disintegration temperature dependence on thin-film thickness has been found: a reduction
of the process temperature has been observed with thickness in the range from 100 to 20 nm; however, the disintegration temperature
starts to increase for Au film thicknesses lower than 20 nm. It is supposed that the observed non-monotonic behavior of the
process temperature is caused by the influence of the substrate interaction with the film, resulting in an entropy change
of the system. 相似文献
94.
N. L. Zaitsev I. A. Nechaev E. V. Chulkov 《Journal of Experimental and Theoretical Physics》2010,110(1):114-120
The change in the electronic structure of silver thin films of different thicknesses with the Ag( 111) orientation due to
the interaction with an adsorbed monolayer of ordered organic molecules of 3,4,9,10-perylene-tetracarboxylic acid dianhydride
(PTCDA) has been investigated in terms of density functional theory. It has been shown that one of the two surface states
of the pure films transforms into an unocc upied interface state due to the interaction so that all the main features of the
initial state are retained. The relation of the resulting state to the unoccupied state experimentally observed in the PTCDA/Ag(
111 ) system by scanning tunneling and two-photon photoemi ssion spectroscopy has been discussed. 相似文献
95.
Vibrational spectrum of the ordered Pt(111)–( ?3 ×?3 ) \left( {\sqrt {3} \times \sqrt {3} } \right)
R30°–K surface superstructure formed on the platinum surface with adsorption of 1/3 ML potassium is calculated with the use of the
interatomic interaction potentials obtained in the strong bond approximation. Relaxation of the surface, dispersion of the
surface phonons, local density of vibrational states, and polarization of phonon modes of adatoms and atoms of the substrate
are discussed in the work. The theoretical results obtained agree well with the available experimental data. 相似文献
96.
E. V. Chulkov A. Zugarramurdi S. S. Tsirkin X. Zubizarreta I. A. Nechaev I. Yu. Sklyadneva S. V. Eremeev 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,75(1):37-47
We present a brief overview of recent studies and new theoretical results for electron-phonon interaction in the $\overline{Y}$ surface states on FCC(110) noble metal surfaces as well as in surface and quantum-well states of thin films. We discuss the oscillations of electron-phonon coupling parameter λ and the respective contribution to the lifetime broadening of these states. We analyse the effect of spin-orbit splitting of surface states on an electron-electron contribution to lifetimes of excited electrons (holes). Oscillations of the electron-electron contribution and quadratic dependence of the linewidth on energy is discussed for ultrathin Pb(111) films. 相似文献
97.
98.
We report ab initio study of the electron-phonon coupling in a free standing Beryllium monolayer. The calculations were carried out using a linear-response approach in the plane-wave pseudopotential representation. The Eliashberg spectral function α2F(ω) and the electron-phonon coupling parameter λ are evaluated at the Fermi level. The obtained results show a large contribution to the electron-phonon coupling from the low-energy transverse mode scattering. 相似文献
99.
100.
We present a brief survey of the contemporary state of theoretical study of quasiparticles (excited electrons and holes) dynamics in bulk metals and at metal surfaces. Quasiparticle decay mechanisms are discussed in terms of electron-electron (e-e) and electron-phonon (e-ph) interactions. The e-ph decay channel is shown to be important for all materials considered. It is especially important for systems with the thickness of one monolayer. In the e-e decay channel the quasiparticle decay can be realized via one-electron transfer processes, via creation of electron-hole pairs, and via plasmon excitation. In ferromagnetic systems the electron (hole) decay via the Stoner pair excitation or/and magnon excitation is made possible. 相似文献