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61.
Uniformity of deep levels in semi-insulating InP obtained by multiple-step wafer annealing 总被引:1,自引:0,他引:1
K. Kuriyama K. Ushiyama T. Tsunoda M. Uchida K. Yokoyama 《Journal of Electronic Materials》1998,27(5):462-465
The uniformity of deep levels in semi-insulating InP wafers, which have been obtained by multiple-step wafer annealing under
phosphorus vapor pressure, was studied using the thermally stimulated current (TSC) and photoluminescence (PL) methods. Only
three traps related to Fe, T0 (ionization energy Ei=0.19 eV), T1 (0.25 eV), and T2 (0.33 eV), probably forming complex defects, were observed in the wafer and they exhibited a relatively uniform distribution.
PL spectra relating to phosphorus vacancies observed in some regions of the wafer are correlated with a small TSC signal having
an ionization energy of 0.43 eV. 相似文献
62.
An EPR study of defects induced in 6H-SiC by ion implantation 总被引:1,自引:0,他引:1
R. C. Barklie M. Collins B. Holm Y. Pacaud W. Skorupa 《Journal of Electronic Materials》1997,26(3):137-143
Crystalline (0001) plane wafers of n-type 6H-SiC have been implanted at room temperature with 200 keV Ge+ ions in the dose range 1012 to 1015 cm−2. Electron paramagnetic resonance (EPR) measurements have been made on these samples both before and after annealing them
at temperatures in the range room temperature to 1500°C. The as-implanted samples have a single isotropic and asymmetric line
EPR spectrum whose width, ΔBpp, increases with ion dose before falling when a buried continuous amorphous layer is produced. This increase is interpreted
in terms of the change in the relative intensity of a line with g = 2.0028 ± 0.0002, ΔBpp = 0.4 mT associated primarily with carbon dangling bonds in a-SiC and a line with g in the range 2.0033 to 2.0039 of uncertain
origin. The variation with anneal temperature of the populations of these defects is reported. 相似文献
63.
The C49–C54 transformation has been studied in TiSi2 thin films having different concentration of defects. The defect concentration in the C49 phase has been varied using different thermal processes in the 460–540 °C temperature range; in fact, the defect concentration decreases with increasing the temperature and/or the duration of the thermal process as attested by the large variation of the silicide residual resistivity at 4 K. The kinetics of the transformation at 650 °C has been followed by in situ resistivity measurements and, for each sample, the transition time decreases as the defect concentration in the metastable phase decreases. 相似文献
64.
The presence of hole traps has been studied by deep level transient spectroscopy (DLTS) characterization of low carrier densityp-type GaAs grown by MBE on p+-GaAs substrates using Al and Co Schottky contacts. The results obtained indicate the presence of several hole traps with
energy levels of between 0.06 and 0.65 eV above the valence band in concentrations up to 2 × 1012/cm3. Some of these defects,e.g. Cu, are ascribed to system-, source-or substrate-related impurities, but the origin of several other defects is unknown. 相似文献
65.
Abanti Nag 《Journal of Physics and Chemistry of Solids》2005,66(1):191-199
SrAl12O19:Pr3+, Ti4+ phosphor suitable for field emission displays is prepared by the wet chemical gel-carbonate method and the mechanism of enhancement in red photoluminescence (PL) intensity with Ti4+ therein has been investigated. The PL spectra of Pr3+ show both 1D2-3H4 and 3P0-3H6 emission in the red region with very weak intensity when excited at 355 nm. The emission intensity has increased by about 100 times at room temperature in the compositional range SrAl12−xTixO19+x/2:Pr3+, with 0.1≤x≤0.3 in comparison to Ti-free SrAl12O19:Pr3+. TEM investigations show the presence of exsolved nanophase of SrAl8Ti3O19, the precipitation of which is preceded by the presence of defect centers at the interfacial regions between the semicoherent transient phase and the parent SrAl12O19 matrix. The presence of transitional nanophase and the associated defects modify the excitation-emission process by way of formation of electronic sub-levels at lower energy (3.5 eV) than the band gap of SrAl12O19 (∼7 eV) followed by non-resonance energy transfer to Pr3+ level, leading to magnetic-dipole related red emission with enhanced intensity. The PL intensity of Pr3+ decreases at high Ti4+ concentrations (x>0.3) due to higher extent of segregation of non-emissive SrAl8Ti3O19:Pr3+ phase. 相似文献
66.
K.Z RushchanskiiH Haeuseler D.M Bercha 《Journal of Physics and Chemistry of Solids》2002,63(11):2019-2028
For the compounds FeGa2S4 and NiGa2S4 band structure calculations have been performed by the ab initio plane wave pseudo-potential method. The valence charge density distribution points to an ionic type of chemical bonding between the transition metal atoms and the ligand atoms. Two models for the pseudo-potentials are used to calculate the band structures: (a) only s and p electrons and (b) also the d-shells of the transition metal atoms are included in the pseudo-potentials. The differences between these two cases of band structures are discussed. Energy gap formation peculiarities are analysed for both crystals. Zak's elementary energy band concept is demonstrated for the energy spectra of the considered crystals. 相似文献
67.
The interaction between particle-like sources of the
nematic director distortions (e.g., colloids, point
defects, macromolecules in nematic emulsions) allows for a useful
analogy with the electrostatic multipole interaction between
charged bodies. In this paper we develop this analogy to the level
corresponding to the charge density and consider the general
status of the pairwise approach to the nematic emulsions with
finite-size colloids. It is shown that the elastic analog of the
surface electric charge density is represented by the two
transverse director components on the surface imposing the
director distortions. The elastic multipoles of a particle are
expressed as integrals over the charge density distribution on
this surface. Because of the difference between the scalar
electrostatics and vector nematostatics, the number of elastic
multipoles of each order is doubled compared to that in the
electrostatics: there are two elastic charges, two vectors of
dipole moments, two quadrupolar tensors, and so on. The
two-component elastic charge is expressed via the vector of
external mechanical torque applied on the particle. As a result,
the elastic Coulomb-like coupling between two particles is found
to be proportional to the scalar product of the two external
torques and does not directly depend on the particles' form and
anchoring. The real-space Green function method is used to develop
the pairwise approach to nematic emulsions and determine its form
and restrictions. The pairwise potentials are obtained in the
familiar form, but, in contrast to the electrostatics, they
describe the interaction between pairs (dyads) of the elastic
multipole moments. The multipole moments are shown to be uniquely
determined by the single-particle director field, unperturbed by
other particles. The pairwise approximation is applicable only in
the leading order in the small ratio particle
size-to-interparticle distance as the next order contains
irreducible three-body terms. 相似文献
68.
69.
M. Houssa G. PourtoisM. Meuris M.M. Heyns V.V. Afanas’evA. Stesmans 《Microelectronic Engineering》2011,88(4):383-387
The identification of a nontrigonal Ge dangling bond at SiO2/Si1−xGex/SiO2 heterostructures and its electrical activity are discussed, both from experimental and theoretical points of view. This dangling bond is observed from multifrequency electron-spin resonance experiments performed at 4.2 K, for typical Ge concentrations in the range 0.4 ≤ x ≤ 0.85. The electrical activity of this defect is revealed from capacitance-voltage characteristics measured at 300 and 77 K, and is found to behave like an acceptor defect. First-principles calculations of the electronic properties of this Ge dangling bond indicate that its energy level approaches the valence band edge of the Si1−xGex layer as the Ge content increases, confirming its acceptor-like nature. 相似文献
70.
We have studied the adsorption of O2 on the Cu(1 0 0) surface using both static potential energy surface (PES) calculations and ab initio molecular dynamics. The dynamical calculations complement the PES results, revealing steering effects which could not be predicted based on the static calculations only. We study the effect of oxidation and Ag doping on O2 adsorption dynamics. The results are discussed in the light of recent molecular beam experiments. 相似文献