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171.
N. V. Sidorov M. N. Palatnikov A. A. Kruk A. A. Yanichev O. V. Makarova N. A. Teplyakova O. Yu. Pikoul 《Optics and Spectroscopy》2014,116(2):274-280
Using methods of electronic spectroscopy, laser conoscopy, photoinduced (photoreactive) light scattering, and Raman light-scattering spectroscopy, we have studied the optical homogeneity, optical transmission, and photorefractive properties of single crystals LiNbO3:Mg(5.21 mol %) and LiNbO3:Fe(0.009 mol %):Mg(5.04 mol %) that were grown from congruent melts. We have ascertained that doping with “nonphotorefractive” Mg2+ cations causes suppression of the photorefractive effect in a lithium-niobate crystal. Upon double doping (Fe:Mg), if the concentration of Mg2+ cations exceeds the threshold concentration, the photorefractive effect is almost not observed and the presence of “photorefractive” Fe cations does not affect the photorefractive effect as strongly as in congruent crystals doped with Fe. 相似文献
172.
Analytical potentialities of a chip-based CE in determination of ammonium in wastewaters were investigated. CZE with the electric field and/or ITP sample stacking was performed on a column-coupling (CC) chip with integrated conductivity detectors. Acetate background electrolytes (pH ~3) including 18-crown-6-ether (18-crown-6) and tartaric acid were developed to reach rapid (in 7-8 min) CZE and ITP-CZE resolutions of ammonium from other cations (sodium, potassium, calcium and magnesium) present in wastewater samples. Under preferred working conditions (suppressed hydrodynamic flow (HDF) and EOF on the column-coupling chip), both the employed methods did provide very good repeatabilities of the migration (RSD of 0.2-0.8% for the migration time) and quantitative (RSD of 0.3-4.9% for the peak area) parameters in the model and wastewater samples. Using a 900-nL sample injection volume, LOD for ammonium were obtained at 20 and 40 μg/L concentrations in CZE and ITP-CZE separations, respectively. Very good agreements of the CZE and ITP-CZE determinations of ammonium in six untreated wastewater samples (only filtration and dilution) with the results obtained by a reference spectrometric method indicate a very good accuracy of both the CE methods presented. 相似文献
173.
Abstract We report measurements of the molecular tilt angle of a ferroelectric liquid crystal mixture (ZLI 3654), using infra-red spectroscopy, and of the optical tilt angle using polarizing microscopy. The molecular tilt angle is found to be approximately the same for different molecular vibrations. The second rank orientational order parameter for the axis of molecular vibrations of different groups of the molecule for homogeneously aligned samples have been determined as a function of temperature. The order parameter depends slightly on the sample thickness and is about 8 per cent higher for a lower thickness (~ 7 μm) compared to a higher thickness (~ 12 μm). The order parameter does not change significantly at the SC?–SA transition. The order parameter of SC? is found to be unaffected by the application of a constant electric field. The order parameter for the alkyl chain is found to be about three times lower than for the molecular core. 相似文献
174.
The liquid crystalline and optical properties of four dicholesteryl derivatives having various linkage configurations, but with the same number of connecting carbons (18), have been investigated, using differential scanning calorimetry, polarizing optical microscopy, Fourier transform infrared (FTIR) spectroscopy and UV-Vis spectroscopy. Quite different phase behaviours and optical properties have been found for these compounds, while all of them exhibited the behaviour specific for a cholesteric phase. By rapid cooling from the cholesteric phase to 0°C, the iridescent colours of some of the dicholesteryl esters were fixed in the cholesteric glassy state. It was difficult but possible to fix various stable colours in the cholesteric glassy state of one compound with a polymethylene (CH2)18 linking chain. It was much easier to fix less stable colours for samples with the linking groups (CH2)6 and C=C double bonds between them. Very unstable colours could also be fixed for the compound with the (CH2)7 chains and a diyne group. The fourth compound with a branched linking chain gave a cholesteric phase which showed colours at room temperature. FTIR spectroscopy measurements provided interesting results concerning the average change in molecular configuration between the blue cholesteric glass and the crystal for the compound with the (CH2)7 polymethylene chains which crystallized within a few hours; also frequency changes associated with some bands were found and reported. 相似文献
175.
N. N. Kruk 《Journal of Applied Spectroscopy》2008,75(2):174-180
Quenching by molecular oxygen of excited states of water-soluble anionic 5,10,15,20-tetarkis-(4-sulfonatophenyl)-porphyrin
(H2TSPP) and cationic 5,10,15,20-tetrakis-(4-N-methylpyridyl)-porphyrin (H2TMPyP) in aqueous ethanol was investigated. It was found that fluorescence quenching of dissociated (in water) and undissociated
(in ethanol) forms of H2TSPP was diffusion-controlled and occurred at distances close to contact ones (0.5–0.8 nm). Fluorescence of the dissociated
form of H2TSPP was quenched with rate constant kS that was 1.7 times greater than that of the undissociated form. It was proposed that this was due to a decrease in the porphyrin
molecule oxidation potential on going from the undissociated to the dissociated form. It was shown that the most probable
reason for the dramatic increase in the rate constant of the fluorescence quenching of H2TMPyP in water compared with that of H2TSPP was the low-lying intramolecular charge-transfer state typical of H2TMPyP.
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Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 2, pp. 170–176, March–April, 2008. 相似文献