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311.
In scattering calculations using the T-matrix method, the calculation of the T-matrix involves multiplication and inversion of matrices. These two types of matrix operations are time-consuming, especially for the matrices with large size. Petrov et al. [D. Petrov, Y. Shkuratov, G. Videen, Opt. Lett. 32 (2007) 1168] proposed an optimized matrix inversion technique, which suggests the inversion of two matrices, each of which contains half the number of rows. This technique reduces time-consumption significantly. On the basis of this approach, we propose another fast calculation technique for scattering in the T-matrix method, which obtains the scattered fields through carrying out only the operations between matrices and the incident field coefficient. Numerical results show that this technique can decrease time-consumption by more than half that of the optimized matrix inversion technique by Petrov et al. 相似文献
312.
We present a new analysis of the electron capture mechanism in polar molecules, based on von Neumann's theory of self-adjoint extensions. Our analysis suggests that it is theoretically possible for polar molecules to form bound states with electrons, even with dipole moments smaller than the critical value D0=1.63×10−18 esu cm. We argue that the quantum mechanical scaling anomaly is responsible for the formation of these bound states. 相似文献
313.
B. Shi X. Liu Z. Chen G. Jia K. Cao Y. Zhang S. Wang C. Ren J. Zhao 《Applied physics. B, Lasers and optics》2008,93(4):873-877
We fabricated a hemispherical nearly-intrinsic Si-based photodetector with (
plane. The photocurrent generated from the detector under a continuous wave laser at the wavelength of 1.3 μm was observed.
The photocurrent shows a quadratic dependence on the incident optical power. The dependence of the photocurrent on the azimuth
of the incident optical field is consistent with the anisotropy of the two-photon absorption in Si crystals. The ratio of
the two nonzero independent components of the third-order susceptibility of silicon is obtained to be 0.42 from the observed
result of the anisotropy of the photocurrent. 相似文献
314.
D. Zhang J. Jasinski M. Dunlap M. Badal V. J. Leppert V. Katkanant 《Applied Physics A: Materials Science & Processing》2008,92(3):595-599
Silica nanosprings were synthesized using a simple, low temperature, chemical vapor deposition method via a vapor–liquid–solid
mechanism. Nanosprings with excellent uniformity and helicity in high and repeatable yields have been observed. The morphology
and crystal structure of the nanosprings were characterized by scanning electron microscopy and transmission electron microscopy.
The chemical composition of the nanosprings was determined using the energy-filtered transmission electron microscopic method.
The as-grown nanomaterials were confirmed to be amorphous silica with irregularly shaped Au catalytic particles located at
the tips. In addition, we propose a spontaneous spinning growth model to explain the formation of such helical nanostructures. 相似文献
315.
L. Englert M. Wollenhaupt L. Haag C. Sarpe-Tudoran B. Rethfeld T. Baumert 《Applied Physics A: Materials Science & Processing》2008,92(4):749-753
Laser material processing of dielectrics with temporally asymmetric femtosecond laser pulses of identical fluence, spectrum,
and statistical pulse duration is investigated experimentally. To that end single shot structures at the surface of fused
silica as a function of fluence and pulse shape are analyzed with the help of scanning electron microscopy. Structures for
the bandwidth limited pulses show the known expansion in structure size with increasing laser fluence approaching the diffraction
limit, which is 1.4 μm for the 0.5NA microscope objective used. In contrast, structures from the asymmetric pulses are remarkably
stable with respect to variations in laser fluence and stay below 300 nm despite doubling the fluence. Different thresholds
for surface material modification with respect to an asymmetric pulse and its time reversed counterpart are attributed to
control of different ionization processes. 相似文献
316.
T. McAvoy J. Zhang C. Waldfried D.N. McIlroy P.A. Dowben O. Zeybek T. Bertrams S.D. Barrett 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(4):747-755
The experimental band structure of Mo(112) and the effects by temperature and adsorbate are presented. A surface resonance,
identified as crossing the Fermi level at about 1/3 from to of surface Brillouin zone, was observed to be very sensitive to both contamination and temperature. We find evidence of adsorbate
and temperature induced reconstruction of the Mo(112) surface. Examination of low-energy electron diffraction (LEED) and scanning
tunneling microscopy (STM) data provides evidence for an adsorbate induced reconstruction of the Mo(112) surface with periodicities
consistent with the Fermi level crossing of the surface resonance. The reconstruction is found to occur at coverages as low
as 0.03 Langmuirs of oxygen or carbon. The reconstruction and/or adsorbate affects the density of states and bands near the
Fermi level of a
1 symmetry.
Received 3 March 1999 and Received in final form 1 October 1999 相似文献
317.
J.-U. Sommer 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(3):537-542
We study the adsorption cross-over of ideal polymer chains in an environment of disordered traps. Starting from the assumption
of an optimal cluster size of traps (optimal fluctuation method) we derive a general scaling form of the free energy function
for arbitrary spatial dimensions. For small concentrations of traps we find a cross-over from localized (adsorbed) behavior
to delocalized behavior depending on the chain's length and on the depth of the traps; this is connected with the non-monotonic
behavior of the chain's extension. In terms of the free energy of the chain this cross-over resembles a first order transition
scenario, the chain gets localized at many traps at once.
Received 18 November 1998 相似文献
318.
T. Garel H. Orland E. Orlandini 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,12(2):261-268
We consider polymers made of magnetic monomers (Ising or Heisenberg-like) in a good solvent. These polymers are modeled as
self-avoiding walks on a cubic lattice, and the ferromagnetic interaction between the spins carried by the monomers is short-ranged
in space. At low temperature, these polymers undergo a magnetic induced first order collapse transition, that we study at
the mean field level. Contrasting with an ordinary point, there is a strong jump in the polymer density, as well as in its magnetization. In the presence of a magnetic field,
the collapse temperature increases, while the discontinuities decrease. Beyond a multicritical point, the transition becomes
second order and -like. Monte Carlo simulations for the Ising case are in qualitative agreement with these results.
Received 11 February 1999 相似文献
319.
M. Gartz C. Keutgen S. Kuenneke U. Kreibig 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,6(1):127-131
In this paper a detailed experimental study of Coherent Population Trapping (CPT) effect on sodium induced by a dye-laser
operating in a three-mode regime is presented and a detailed analysis of the role of velocity changing collisions is made.
These collisions show a very small relaxation effect on the dark resonances which are visible even at high pressures. For
the first time we demonstrate the persistence of the ground state coherence to pressures up to one atmosphere for a relatively
“heavy” buffer gas like argon. The experimental results have been compared with theory and a very good agreement has been
obtained. Preliminary results on the effect of Na-N2 collisions on Coherent Population Trapping are presented.
Received: 5 October 1998 / Received in final form: 3 December 1998 相似文献
320.
Xun-Li Feng Zhao-Yang Chen Zhi-Zhan Xu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,7(1):117-121
The nondegenerate two-photon interaction of a two-level atom with a broadband multimode squeezed vacuum is investigated. We
find that in the two-photon process the squeezed vacuum has a driving effect on the atom which can lead to an ac Stark effect
when the average photon number of the squeezed vacuum is larger than a critical value.
Received: 2 February 1999 / Received in final form: 20 April 1999 相似文献