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11.
MOVPE-preparation of highly ordered InP(100) and GaP(100) surfaces was monitored with in-situ reflectance difference spectroscopy
(RDS). Specific ordered P-terminated and ordered cation-terminated surface reconstructions were identified with specific structured
RD spectra with the highest peaks. After contamination-free transfer of the samples to UHV, RDS measurements were performed
also at 20 K. The experimental RD spectrum for the In-terminated, (2×4) reconstructed InP(100) surface shows a remarkable
similarity to a recently published theoretical spectrum, whereas there is only moderate similarity between the experimental
RD spectrum for the (2×4) reconstructed Ga-terminated GaP(100) surface and a recently proposed theoretical spectrum. 相似文献
12.
J. R. Gong S. Nakamura M. Leonard S. M. Bedair N. A. El-Masry 《Journal of Electronic Materials》1992,21(10):965-970
AIGaP and GaP films were deposited on the (100) Si substrates by atomic layer epitaxy (ALE) in the temperature range between
450 and 600°C. Under optimum growth conditions, the growth of GaP and AIGaP was observed to proceed in a two-dimensional (2-D)
fashion in the initial growth stages. These ALE-grown films have better surface morphology when compared with the corresponding
MOCVD-grown films. With an AIGaP buffer layer grown on Si, the subsequent growth of GaAs on the AlGaP-coated Si substrates
tends to proceed as 2-D growth. This avoids island growth and the two-step growth process currently used. 相似文献
13.
We present a study of the real-time monitoring of the homoepitaxial growth of GaP, InP, and the growth of InP/GaP and GaP/Si(001)
heterostructures, combining single wavelength p-polarized reflectance (PRS), reflectance-difference spectroscopy (RDS), and
laser light scattering (LLS) during pulsed chemical beam epitaxy with tertiarybutylphosphine, triethylgallium, and trimethylindium
sources. The growth rate and the bulk optical properties are revealed by PRS with submonolayer resolution over 1000A of film
growth. The surface topography is monitored by LLS providing additional information on the evolution of the surface roughness
as well as the nucleation/growth mechanism. The optical surface anisotropy, which is related to surface reconstruction and/or
surface morphology, is monitored by RDS and compared with the results of PRS and LLS. The results are discussed with respect
to the deposition kinetics, in particular as a function of the V:III flux ratio. The pulsed supply of chemical precursors
causes a periodic alteration of the surface composition, which is observed as correlated periodic changes in the RD and PR
signals, confirming the high sensitivity of both methods to surface chemistry. 相似文献
14.
Photocapacitance (PHCAP) measurements have been carried out on GaP crystals grown by the liquid-encapsulated Czochralski (LEC)
method with heat treatment under various phosphorus-vapor pressures at different temperatures. Electron traps of EC−1.1 eV, EC−1.6 eV, EC−1.9 eV, and a hole trap of EV+2.26 eV are mainly detected. The phosphorus-vapor pressure dependence of the EC−1.9 eV trap density and their diffusion behavior indicate that they are interstitial phosphorus atoms. The densities of both
EC−1.1 eV and EC−1.6 eV traps are strongly dependent on the shallow impurity concentrations. Moreover, the density of EC−1.1 eV traps increases with increasing phosphorus-vapor pressure. From these results, we suggest that EC−1.1 eV traps are the complexes of shallow donors and antisite phosphorus atoms. Deep-level densities in GaP crystals after
annealing at 860°C or 960°C for 60 min are decreased almost one order of magnitude lower than those in untreated substrate
crystals, which should have occurred via out-diffusion of interstitial phosphorus atoms. However, such an effect is not prominent
for 800°C treatment for 60 min. 相似文献
15.
The effect of nitrogen doping on the 300°K quantum efficiency and luminescence spectra of VPE-grown gallium phosphide has
been investigated. The range of nitrogen concentrations studied was 2 × 1018 –1.5 × 1019 cm{−3 on the corrected Lightowlers scale. Over this range, the external quantum efficiency of contactless dice at 40 amp/cm2 in air varied from 0.04% to 0.13%, increasing monotonically with increasing nitrogen concentration. The photoluminescence
spectra from as-grown epi layers and the electroluminescence spectra of contacted dice in reflecting cups were compared, and
were characterized by the parameters lumens/watt, radiometric center of gravity, and photometric center of gravity. The relationship
of these parameters to each other and their variation with nitrogen concentration in GaP has been determined. The problem
of filtering the spectra to obtain greener devices with acceptable brightness has been investi-gated using the transmission
spectra of two specific filters. 相似文献
16.
The degradation of light output with operating time has been studied for nitrogen doped GaP light emitting diodes fabricated
from vapor phase epitaxial material. The degradation is found to saturate at a non-zero value of efficiency. The process is
characterized in terms of a degradation rate constant and the saturation value of efficiency. The rate is found to be a strong
function of current density during operation and to a lesser degree materials parameters such as dislocation density. The
saturation value appears to be independent of these parameters.
The degradation is specifically associated with a decrease in the minority carrier lifetime in the p-side of these diffused
LEDs. A model for the generation of non-radiative recombination centers which describes the degradation process quantitatively
is presented. 相似文献
17.
Jun-ichi Nishizawa Tetsuo Sasaki Ken Suto Masahiko Ito Takashi Yoshida Tadao Tanabe 《International Journal of Infrared and Millimeter Waves》2008,29(3):291-297
We developed high-resolution GaP THz signal generator using Cr:Forsterite lasers with gratings as both a pump and a signal
beam for difference-frequency generation. A line width of less than 500 MHz and a wide tunable frequency range (0.6–6.2 THz)
provide sufficient resolution for measuring materials with sharp absorption bands using the generator as the light source
for a THz spectrometer. This is suitable for materials such as gases or solid samples at low temperatures. We demonstrated
the detection of defects in organic materials, as they appear as slight deviations in the absorption frequency in the THz
region. 相似文献
18.
Y.K. Liu Y.Y. Shan H.B. Wang Chun-Shen Lee Shu-Tong Lee 《Superlattices and Microstructures》2008,44(2):208-215
GaP nanochains have been synthesized by hydrogen-assisted thermal evaporation, and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL), and Raman spectroscopy. GaP nanochains possess a (111) twin crystal plane-modulated quasi-periodic structure, that gives a strong green photoluminescence at 618 nm. While the Raman spectrum of the nanochains is similar to that of the GaP crystal, the intensity of the longitudinal optical (LO) peak is stronger than that of the transverse optical (TO) peak, which is supposedly related to the nanochain microstructures. 相似文献
19.
20.