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371.
ZnS nanorods were fabricated by annealing precursor ZnS nanoparticles, which were prepared by one-step, solid-state reaction of ZnCl2 and Na2S through grinding by hand at ambient temperature, in NaCl flux. The as-prepared ZnS nanorods have diameters of 40-80 nm, and lengths up to several micrometers. The structural features and chemical composition of the nanorods were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), high-resolution transmission electron microscopy (HRTEM), and Raman spectra. 相似文献
372.
In this work, we demonstrate the synthesis of various types of boron nanowire junctions in a self-assembled manner by simple closed-tube thermal vapor transfer method. The Y-type boron nano-junctions and lateral boron-silicon alloy nano-junctions were grown on Si substrates, based on the oxide assisted VLS growth mode at a relatively low processing temperature regime and the VLS growth mode at the high processing temperature regime, respectively. 相似文献
373.
A lattice of magneto-optical and magnetic traps for cold atoms 总被引:1,自引:0,他引:1
A. Grabowski T. Pfau 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(3):347-354
We describe basic periodic trapping configurations for ultracold atoms above surfaces. The approach is based on a simple wire
grid and can be scaled to provide large arrays of periodically arranged magnetic or magneto-optical traps. The unit cells
of the trap lattices are based on crossed wire segments. By alternating the current directions in the wires of the grid it
can be distinguished between 3 basic lattice configurations. As a first demonstration, we used macroscopic wires in a 2 layer
configuration to realize the unit cells of the lattices. With this experimental setup, we observe two of the basic unit cells
and an array of 2×2 magneto optical traps.
Received 29 August 2002 / Received in final form 12 December 2002 Published online 18 February 2003 相似文献
374.
The finite element method is employed to analyze photoacoustic cavitation and heat transfer occurring when modest temperature
jumps (T-jumps) are induced by a laser in D2O solution, which may contain a small concentration of a protein or peptide sample. Cavitation can be initiated through a
photoacoustic mechanism at intensities well below optical breakdown thresholds. Cavitation probability is related to test
medium properties, initial temperature, T-jump magnitude and test region geometry. Parameters affecting thermal conduction
losses are also examined because such losses limit the useful duration of the T-jump induced in protein folding experiments.
From this study, guidelines are offered for reducing the occurrence of cavitation and extending the useful duration of the
T-jump.
Received: 2 April 2001 / Revised version: 17 October 2001 / Published online: 29 November 2001 相似文献
375.
计算了在太阳核心从R=0到R=0.125R⊙处,7Be存在1个或2个K壳层束缚电子的概率约为4.54%.这表明7Be原子俘获的电子95.46%是自由电子.假定太阳中微子自产生后没有发生任何改变,并且太阳的其他参量不改变,那么7Be和8B太阳中微子流量的理论计算值分别约为4.04×109和6.12×106cm-2s-1.这将进一步扩大8B太阳中微子与superKamiokande太阳中微子实验测量值之间的差距
关键词:
K壳层束缚电子 电子俘获概率 7Be太阳中微子流量 8B太阳中微子流量 相似文献
376.
A. Liebsch T. A. Costi 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,51(4):523-536
The two-band Hubbard model involving subbands of different widths is
investigated via finite-temperature exact diagonalization (ED) and
dynamical mean field theory (DMFT). In contrast to the quantum Monte Carlo
(QMC) method which at low temperatures includes only Ising-like exchange
interactions to avoid sign problems, ED permits a treatment of Hund's
exchange and other onsite Coulomb interactions on the same footing.
The role of finite-size effects caused by the limited number of bath
levels in this scheme is studied by analyzing the low-frequency behavior
of the subband self-energies as a function of temperature, and by
comparing with numerical renormalization group (NRG) results for a
simplified effective model.
For half-filled, non-hybridizing bands, the metallic and insulating
phases are separated by an intermediate mixed phase with an insulating
narrow and a bad-metallic wide subband. The wide band in this phase
exhibits different degrees of non-Fermi-liquid behavior, depending on
the treatment of exchange interactions. Whereas for complete Hund's
coupling, infinite lifetime is found at the Fermi level, in the
absence of spin-flip and pair-exchange, this lifetime becomes finite.
Excellent agreement is obtained both with new NRG and previous
QMC/DMFT calculations. These results suggest that-finite temperature
ED/DMFT might be a useful scheme for realistic multi-band materials. 相似文献
377.
T. Sugibayashi 《Solid State Communications》2004,132(1):43-47
Optical conductivity in NaxCoO2 is calculated with tight binding approximation. The calculated gross features agree with the experimental findings. Interband transitions between nearly degenerate t2g bands bring about absorption in the mid-infrared and near infrared regions. Structures observed at higher energies are also quite well reproduced with the present calculation. Possible effects of electron correlation are also briefly discussed. 相似文献
378.
X.Z. Shang P.J. Niu W.L. Guo W.X. Wang Q. Huang J.M. Zhou 《Physica E: Low-dimensional Systems and Nanostructures》2005,30(1-2):36-40
Highly complex Npn AlGaAs/GaAs single heterojunction bipolar transistor (HBT) layers with Be-doped base were investigated by photoluminescence (PL) spectroscopy. Room temperature PL shows only a broad peak of GaAs due to thermalization; 15 K PL shows five peaks. The peak at 1.481 eV is from a p-type GaAs base, that at 1.517 eV is from a low-doped GaAs layer and that at 1.55 eV is from a high-doped GaAs collector. The that at 1.849 eV is due to bound exciton recombination in an AlGaAs emitter, and that at 1.828 eV is due to the acceptor-related transition from the AlGaAs layer. The integrated intensity ratio of these two peaks can be used to investigate the Be outdiffusion behavior, thus optimizing the growth conditions of base. The DC current gain of the HBT structure with different growth conditions was found to be in good agreement with the PL results. 相似文献
379.
N. Liu W. Gao J. Yin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(2):137-145
A new scheme to magnetically guide cold, neutral atoms using a V-shaped current-carrying conductor is proposed. The spatial
distributions of the magnetic fields, potentials and forces generated by the V-shaped current-carrying conductor are calculated,
and the relationship between the magnetic field and the parameters of the V-shaped current-carrying conductor are analyzed
in detail. Our study shows that the V-shaped current-carrying conductor proposed here can be used to guide cold atoms in the
weak-field-seeking state, and to construct various atom-optical elements, such as atomic funnel, atomic beam-splitter and
atom interferometer and so on, and even to realize a single-mode atomic waveguiding under certain conditions.
Received 17 November 2000 and Received in final form 26 May 2001 相似文献
380.