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841.
Fluid and plastic flow dynamics of the critical state for a strongly pinned 2D superconductor 总被引:2,自引:0,他引:2
D. Monier L. Fruchter 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(2):201-205
The frequency of the Raman active A1g radial breathing mode has been widely used as a tool to estimate the distribution of diameters of single wall carbon nanotubes
(SWNT). However, the relation between frequency and diameter is not straightforward and results are model-dependent. Because
most of the experiments are performed on bundles and not on isolated tubes, the model should especially take into account
the van der Waals intertube interactions. Here, we use a pair-potential approach to account for such interactions and we derive
a nonlinear relation between the SWNT diameter and the frequency of the A1g radial breathing modes. We demonstrate a good agreement between calculations and the diameters derived from diffraction experiments
on the same samples.
Received 22 December 1999 and Received in final form 17 July 2000 相似文献
842.
M. Konôpka V. Bužek 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,10(2):285-293
We propose a method for entangling a system of two-level atoms in photonic crystals. The atoms are assumed to move in void
regions of a photonic crystal. The interaction between the atoms is mediated either via a defect mode or via a resonant dipole-dipole interaction. We show that these interactions can produce pure entangled atomic states. We analyze the problem with parameters typical
for currently existing photonic crystals and Rydberg atoms and we show that the atoms can emerge from photonic crystals in
entangled states. Depending on the linear dimensions of the crystal we estimate that a pair of atoms entangled in a photonic
crystal can be separated by tens of centimeters.
Receive 11 June 1999 and Received in final form 4 October 1999 相似文献
843.
M. Belhadi O. Rafil R. Tigrine A. Khater J. Hardy A. Virlouvet K. Maschke 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(3):435-443
The influence of linear defect boundaries on the transmission and scattering of elastic waves in quasi-two-dimensional wave-guides
is studied using the matching method. A linear defect boundary separating two wave-guide crystalline lattice domains is characterised
here by a linear chain of defect masses and by modified elastic constants in the boundary, different from their values in
the bulk of the domains. In particular a square lattice is considered to model the domains of the two-dimensional planar wave-guide
containing the linear defect. The reflection and transmission probabilities, and the total transmission probabilities are
calculated numerically and presented for the scattering processes in a variety of cases. We show that the interaction between
the localised modes introduced by the defect boundary and the propagating modes of the system leads to Fano resonances. These
resonances shift to higher (lower) frequencies for smaller (larger) defect masses, and for the same mass as function of the
angle of the incident wave. Other spectral features shown to exist are due to interference effects especially at oblique incidence
and when modifying the boundary elastic constants.
Received 8 November 1999 and Received in final form 14 January 2000 相似文献
844.
M. Novellani R. Santini L. Tadrist 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(3):571-578
The aim of this work is to study the porosity of three-dimensional and two-dimensional packing of stiff cylindrical fibres
according to their aspect ratio. First, we have carried out an experimental study of the porosity for 3D and 2D packing. In
this last case, the elementary representative surfaces have been determined. Then, an attempt of interpretation of the porosity
variations for 2D stacks has been realized on the basis of the excluded volume theory and a variation law has been proposed.
To conclude, we have studied the relevance of a simplified packing model based on a single geometry of the defects.
Received 12 April 1999 and Received in final form 4 August 1999 相似文献
845.
Tadamasa Toma Yoshio Furuya Wataru Watanabe Kazuyoshi Itoh Junji Nishii Kenichi Hayashi 《Optical Review》2000,7(1):14-17
It is known that local refractive index change occurs when femtosecond laser pulses with extremely high peak power are launched into glass. We focused 130-femtosecond laser pulses of 800 nm into the bulk of glass and examined the shape of the induced refractive index change. We found that the length of the spot of the refractive index change along the optical axis reached about 30 μm despite the diameter being about 2 μm. To estimate the distribution of induced refractive index change, we fabricated Bragg grating by scanning the focused spot and calculated the amount of the change by applying Kogelnik’s coupled mode theory to the measured diffraction efficiencies of the higher order diffracted beams. 相似文献
846.
The specific features of the triplet-triplet (T-T) transfer of electronic excitation energy in a gas phase upon nonequilibrium
vibrational excitation of the triplet molecules of a donor were studied for an anthraquinone-diacetyl donor-acceptor pair
using the time-resolved slow fluoresence of anthraquinone and sensitized phosphorescence of diacetyl. It is shown that in
the gas phase, which allows regular control of the number of collisions, competition between the processes of T-T transfer
and intermolecular vibrational relaxation is observed for nanosecond time resolution. The T-T transfer rate for the molecular
system investigated exceeded the rate of intermolecular vibrational relaxation kV in the triplet state T1 of the donor. The effectiveness of the T-T transfer of energy by vibrationally excited molecules turned out to be higher
than the effectiveness of transfer by thermalized ones, but even the highest of them was much less than unity. An increase
in the equilibrium temperature of vapors led to a decrease in the effectiveness of transfer for both vibrationally excited
and thermalized triplet molecules, thus indicating the importance of the collisional complex in the intermolecular process
studied.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 4, pp. 474–479, July–August, 2000. 相似文献
847.
Th. Cabioc'h S. Camelio L. Henrard Ph. Lambin 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(3):535-540
Concentric-shell fullerenes, also called carbon onions, produced by carbon ion implantation into silver thin films, and subsequently
deposited on a silica substrate, were studied by optical transmission spectroscopy in the wavelength range 0.2 - 1.2 μm. In
this interval, the strongest absorption is due to the π-plasmon of sp2-like carbon. The position of the plasmon absorption band clearly evolved from 265 nm at low fluence to 230 nm at high implantation
fluences. A simulation of the optical spectra based on dielectric models of the concentric-shell fullerenes layer allowed
us to identify the first peak as due to disordered graphite and the latter to the carbon onions. The concentration of residual
graphite and the filling fraction of the carbon onions produced at high fluences could be estimated by fitting the optical
spectra with computed transmittance curves.
Received 13 July 2000 相似文献
848.
By taking into account all the irreducible representations
and their components in the electron-phonon interaction (EPI) as well as all the levels and the admixtures of wavefunctions within d3 electronic configuration, the thermal shifts (TS) of the ground-state zero-field-splitting (GSZFS) due to EPI for
ruby have microscopic-theoretically been calculated; the contribution
to TS of GSZFS from thermal expansion has also been calculated. The results are in very good agreement with experiments. It is found that the contributions from the first-order perturbation of the second-order term in EPI Hamiltonian are dominant in the
Raman term and optical-branch term for TS of GSZFS; the different between the TS due to EPI of
t23
4A2±(1/2)
e2 (G2) level and the TS due to EPI of
t23
4A2±(3/2)
e2 (G1) level
gives rise to the TS due to EPI of GSZFS, which is very small in
comparison with the TS due to EPI of
G2 or G1 level.
Among various terms in TS of GSZFS, Raman term is the largest one and the signs of the Raman term and optical-branch term are opposite to the sign of the thermal-expansion term; the optical-branch term plays an important role in TS of GSZFS and increases rapidly with temperature; all various contributions
to TS of GSZFS have to be taken into account, since the subtle balance among them determines the total result. The comparison between the features of TS of GSZFS and those of TS of
R1 and R2 lines has been made. For TS of GSZFS, the contribution from thermal expansion is especially important; the neighbor-level term is insignificant. 相似文献
849.
从理论上计算具有两个作用区的互泵浦相位区轭器的阈值耦合强度(γL)th,给出了(γL)th与输入光强比q、光折变晶体内部通道强度传输系数Tt的规律。 相似文献
850.