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31.
32.
33.
Study of magnetoresistance and conductance of bicrystal grain boundary in La0.67Ba0.33MnO3 thin film
La0.67Ba0.33MnO3 (LBMO) thin film is deposited on a 36.7°C SrTiO3 bicrystal substrate using laser ablation technique. A microbridge is created across bicrystal grain boundary and its characteristics
are compared with a microbridge on the LBMO film having no grain boundary. Presence of grain boundary exhibits substantial
magnetoresistance ratio (MRR) in the low field and low temperature region. Bicrystal grain boundary contribution in MRR disappears
at temperature T>175 K. At low temperature, I-V characteristic of the microbridge across bicrystal grain boundary is nonlinear. Analysis of temperature dependence of dynamic
conductance-voltage characteristics of the bicrystal grain boundary indicates that at low temperatures (T<175 K) carrier transport across the grain boundary in LBMO film is dominated by inelastic tunneling via pairs of manganese
atoms and tunneling through disordered oxides. At higher temperatures (T>175 K), magnetic scattering process is dominating. Decrease of bicrystal grain boundary contribution in magnetoresistance
with the increase in temperature is due to enhanced spin-flip scattering process. 相似文献
34.
Pressure dependent UV-visible spectrophotometric measurements were used to determine \(\Delta \bar V^ * \) and \(\Delta \bar \kappa ^ * \) for the formation of alkali metal borate ion pairs. The association constant for each ion pair was measured at 25°C and at ionic strengths of 0.1 and 1.0m over a pressure range of 1 to 2000 atm. The pressure dependence of the apparent association constants, K A (P)/K A (1), have been fitted to $$[RT/(P - 1)]ln[K_A (P)]/[K_A (1)] = - \Delta \bar V^0 + \Delta \bar \kappa ^0 [(P - 1)/2]$$ to determine \(\Delta \bar V^0 and \Delta \bar \kappa ^0 \) . The \(\Delta \bar V^0 \) for the alkali metal borate ion pairs range from 5–9 cm3-mol?1. The association constants were also measured as a function of ionic strength at 1 atm. Extrapolation to I=0 yielded K A of 2.12, 0.66, 0.76 and 1.12 for [LiB(OH)4], [KB(OH)4], [RbB(OH)4] and [CsB(OH)4], respectively. The trend generally indicates less ion pairing and a smaller volume change for the ion pair formation as the size of the cation increases. The concept of localized hydrolysis is used to explain the trend observed in the equilibrium constant of the ion pair as the cation size is changed. 相似文献
35.
The application of multiple experimental techniques to silicon surface studies is discussed. Two specific cases are considered: the chemisorption of oxygen on silicon at coverages up to one monolayer and the intrinsic surface states on cleaved and on annealed Si (111) surfaces. It is shown that by combining electron energy loss spectroscopy and ultraviolet photoemission spectroscopy, one can obtain an approximate energy level model for both occupied and unoccupied states 相似文献
36.
The systematics of the giant dipole resonance have been calculated in the open-shell RPA for all the self-conjugate sd-shell nuclei, using (i) a phenomenological Rosenfeld interaction, (ii) Barret, Hewitt and McCarthy G-matrix elements and (iii) Kuo G-matrix elements. The excitations are based on shell model ground states for all nuclei except 28Si for which a projected Hartree-Fock ground state was used. 相似文献
37.
Molar extinction coefficients of some carbohydrates viz. l-arabinose (C5H10O5), d-glucose (C6H12O6), d-mannose (C6H12O6), d-galactose (C6H12O6), d(-) fructose (C6H12O6) and maltose (C12H24O12) in aqueous solutions have been determined at 81, 356, 511, 662, 1173 and 1332 keV by gamma ray transmission method in a
narrow beam good geometry set-up. These coefficients have been found to depend upon the photon energy following a 4-parameter
polynomial. These extinction coefficients for different sugars having the same molecular formula have same values varying
within experimental uncertainty. Within concentration ranges studied, Beer-Lambert law is obeyed very well. 相似文献
38.
39.
Harrison E. Rowe 《Applied Scientific Research》1984,41(3-4):237-255
We study the mathematical treatment of transmission statistics of coupled wave devices with random imperfections. Such devices include multi-mode waveguides or optical fibers, directional couplers at waveguide or optical frequencies, dominant-wave transmission lines (with the reflected wave the spurious mode), lumped filters composed of circuit or of waveguide elements, multi-layer optical coatings to achieve high or low reflectivity.If the random parameters have very rapid spatial variations, we assume they have white spectra. Exact results for transmission statistics are obtained in such cases. These exact results can be extended to random parameters with almost-white spectra, and narrow-band spectra that are far from white.These calculations are carried out in a simple way by using Kronecker matrix products. 相似文献
40.
The giant piezoresistance (PZR) previously reported in silicon nanowires is experimentally investigated in a large number of depleted silicon nano- and microstructures. The resistance is shown to vary strongly with time due to electron and hole trapping at the sample surfaces independent of the applied stress. Importantly, this time-varying resistance manifests itself as an apparent giant PZR identical to that reported elsewhere. By modulating the applied stress in time, the true PZR of the structures is found to be comparable with that of bulk silicon. 相似文献