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The Kirchhoff diffraction theory is applied to the multi-pinhole aperture diffraction screens, and the intensity, the zero-contour of the real and imaginary parts of complex amplitude and the phase distribution in deep Fresnel diffraction region are simulated. It is found that the number of bright spots, the zero-contours of the real and imaginary parts of complex amplitude and the phase singularities are all related to number of pinholes in diffraction screens. The brightness of bright spots in center of each pattern would become larger with increasing number of pinholes. In addition, there are many lines, on which the intensity value is close to 0.  相似文献
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GaMnN thin films were deposited on a sapphire (0001) substrate by using laser assisted molecular beam epitaxy. Subsequently, the samples were annealed in the ammonia ambience at 1000 °C for different time lengths. The crystalline quality was improved gradually, and the room temperature ferromagnetism of our samples becomes stronger with the increase of the annealing time within 25 min. The X-ray photoelectron spectra analysis confirmed that the Mn3+ concentration in the GaMnN films increased after annealing. The stronger ferromagnetism was observed in the sample with the higher Mn3+ concentration. However, too long annealing time, such as 35 min, will lead to the degradation of the crystalline quality and the decrease of Mn3+ concentration, which results in the weakened ferromagnetism. The optimal annealing time is 25 min at 1000 °C in our experiments. Finally, the origin of the room temperature ferromagnetism in our samples was discussed preliminarily.  相似文献
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The BiPO4/reduced graphene oxide (RGO) nanocomposites were prepared by a facile solvothermal approach. The prepared samples were characterized with Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, UV–vis diffuse reflectance spectroscopy, electrochemical impedance spectra, and Mott–Schottky and the photoluminescence spectra. A large quantity of BiPO4 nanoparticles with sizes of ca. 150 nm were well dispersed on the RGO nanosheets. The absorbance of the BiPO4/RGO nanocomposites is largely enhanced in the range of 400–800 nm compared with that of BiPO4, and the BiPO4/RGO showed better photocatalytic activities under simulated sunlight irradiation than the BiPO4 nanocrystals.  相似文献
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The novel orthorhombic InVO4 nanofibers have been successfully synthesized by annealing electrospun precursor fibers. Citric acid was used as a ligand for it could react with metal salts to get a transparent homogeneous precursor solution and homogeneous precursor sol for electrospining. Polyvinyl pyrrolidone (PVP, K-30) was used as a binder and a structure guide reagent because it was one kind of water-soluble polymers. It is easy to gain one-dimensional materials while the viscosity of the citrate/PVP sol was suitable. The structure, morphology and photocatalytic properties of the nanofibers were characterized by X-ray diffraction (XRD), thermogravimetry analysis (TGA), scanning electron microscopy (SEM) analysis, UV-vis spectrophotometer and fluorescence spectrophotometer. The nanofibers calcined at 700 °C were orthorhombic InVO4 with a width in the range of 30-100 nm and length in micron-grade. This one-dimensional pure orthorhombic InVO4 had the higher photocatalytic activity under visible light irradiation. The photo-degradation rate of nitrobenzene aqueous solution under visible light reached 69% after 6 h. It is obvious that the orthorhombic InVO4 nanofibers have a potential application in wastewater-treatment.  相似文献
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The ultrasonic degradation of p-nitrophenol (p-NP) in aqueous solution with CCl4 enhancement was studied. The effects of operating parameters such as CCl4 dosage, ultrasonic power, media temperature, the initial concentration of p-NP and initial pH value of the aqueous solution on the degradation of p-NP were investigated, and the enhancement mechanism of CCl4 for p-NP sonolysis was also discussed. The results showed that the sonochemical degradation of p-NP was obviously enhanced by adding CCl4. It attributed to the increase OH radicals concentration in the presence of CCl4 as a hydrogen atom scavenger, and the formation of some oxidizing agents such as free chlorine and chlorine-containing radicals. The degradation of p-NP follows a pseudo-first-order kinetics. The degradation rate of p-NP increased with decreasing the temperature, the initial pH value of the solution and decreasing the initial concentration of p-NP. It was also found that p-NP can be mineralized in this process.  相似文献
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We theoretically investigate the strong-field ionization of H+2 molecules in four different electronic states by calculating photoelectron angular distributions in circularly polarized fields. We find that the structure of photoelectron angular distribution depends on the molecular orbital as well as the energy of the photoelectron. The location of main lobes changes with the symmetric property of the molecular orbital. Generally, for molecules with bonding electronic states, the photoelectron's angular distribution shows a rotation of π/2 with respect to the molecular axis, while for molecules with antibonding electronic states, no rotation occurs. We use an interference scenario to interpret these phenomena. We also find that, due to the interference effect, a new pair of jets appears in the waist of the main lobes, and the main lobes or jets of the photoelectron's angular distribution are split into two parts if the photoelectron energy is sufficiently high.  相似文献
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刘曼 《光学学报》2012,32(9):926001-277
利用基尔霍夫衍射理论计算模拟了四圆孔径衍射屏在菲涅耳深区形成的衍射光场的强度、零值线和相位的分布,发现衍射光场亮斑关于中心呈对称分布,在距离衍射屏较近的观察面上,光强值为零的点组成光强零值线段,该线段上光强等值线的离心率都接近或等于1,其两侧的光强值变化非常剧烈。复振幅的实部和虚部零值线多为封闭的曲线,零值线交叉点的个数为偶数,并且正负相位奇异点的个数相等。特殊相位奇异点周围的相位不仅呈对称分布,而且该点的拓扑荷的值近似为零。随着光波的传播,在不同的观察面上光强零值线段逐渐变短,最终趋于一点。  相似文献
9.
实验提取了弱散射体产生的菲涅耳极深区的散斑场.发现当散射距离一定时,弱散射体光场的相位分布特征随散射体的粗糙度的变化而变化;对于某一弱散射体,相位分布特征随散射距离的变化而变化;当弱散射体的粗糙度大到一定程度时,才产生相位涡旋现象;散射体表面上存在相位涡旋;弱散射体产生的相位涡旋的密度随散射屏粗糙度的增大而增大,还随散射距离的增大而增大.研究结果对于认识弱散射体的相位及相位涡旋分布特征随粗糙度和散射距离的演化具有重要意义,而且对于认识散斑场随散射距离的演化有一定的帮助.  相似文献
10.
冷建材  邹斌  马红  李伟 《计算物理》2012,29(4):585-592
利用第一性原理计算金属电极下1,6-己二硫醇和1,4-二巯基苯分子结的非弹性电子隧穿谱,发现非弹性电子隧穿谱对金属电极的变化十分灵敏,并且非弹性电子隧穿谱的振动峰位置和强度与硫原子和金属电极表面的距离密切相关.结果表明电极材料和分子与金属成键的情况是影响分子结的非弹性电子输运的重要因素.理论分析进一步表明不同金属电极和有机分子的耦合能不同导致了谱峰强弱的调整.  相似文献
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