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41.
We perform a first-principles simulation to study the electronic and optical properties of wurtzite Zn1 xCuxO.The simulations are based upon the Perdew-Burke-Ernzerhof form of generalised gradient approximation within the density functional theory.Calculations are carried out in different concentrations.With increasing Cu concentration,the band gap of Zn1 xCuxO decreases due to the shift of valence band.The imaginary part of the dielectric function indicates that the optical transition between O 2p states in the highest valence band and Zn 4s states in the lowest conduction band shifts to the low energy range as the Cu concentration increases.Besides,it is shown that the insertion of Cu atom leads to redshift of the optical absorption edge.Meanwhile,the optical constants of pure ZnO and Zn0.75Cu0.25O,such as loss function,refractive index and reflectivity,are discussed. 相似文献
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采用传统的平板计数法作为对照,利用显微红外光谱技术(4000~400 cm!1)并结合化学计量学,研究了在55℃水浴中热激处理不同时间(0,2,4,6和8 min)对副溶血弧菌失活和亚致死损伤的作用效果。二维主成分分析(PCA)表明,正常细菌与受损细菌能够各自聚类,明显区分,而且损伤程度不同的细菌也能够基本区分。载荷图分析(LPA)发现,加热处理后,副溶血弧菌中的多糖、结构蛋白、脂质、核酸都发生了变化,其细胞壁、细胞膜和DNA皆遭受损伤。类模拟软独立建模(SIMCA)的结果表明,一般情况下,受不同程度热损伤的细菌均有80%以上的预测率,能够被有效区别开。研究表明,显微红外光谱技术具有检测热激后亚致死损伤的副溶血弧菌的潜力。 相似文献
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Self-organized GaN/AlN hexagonal quantum-dots:strain distribution and electronic structure 下载免费PDF全文
This paper presents a finite element method of calculating strain distributions in and around the self-organized GaN/AlN hexagonal quantum dots. The model is based on the continuum elastic theory, which is capable of treating a quantum dot with an arbitrary shape. A truncated hexagonal pyramid shaped quantum dot is adopted in this paper. The electronic energy levels of the GaN/AlN system are calculated by solving a three-dimension effective mass Shrodinger equation including a strain modified confinement potential and polarization effects. The calculations support the previous results published in the literature. 相似文献
46.
Hybrid plasmon waveguides with metamaterial substrate and dielectric substrate:A contrastive study 下载免费PDF全文
Hybrid plasmon waveguides, respectively, with metamaterial substrate and dielectric substrate are investigated and analyzed contrastively with a numerical finite element method. Basic properties, including propagation length Lp, effective mode area Aeff, and energy distribution, are obtained and compared with waveguide geometric parameters at 1.55 gin. For the waveguide with metamaterial substrate, propagation length Lp increases to several tens of microns and effective mode area Aeff is reduced by more than 3 times. Moreover, the near field region is expanded, leading to potential applications in nanophotonics. Therefore, it could be very helpful for improving the integration density in optical chips and developing functional components on a nanometer scale for all optical integrated circuits. 相似文献
47.
The optimal top structure of a nanowire quantum emitter single photon source is significant in improving performance. Based on the axial symmetry of a cylindrical nanowire, this paper optimizes the top profile of a nanowire for the maximum forward emission by combining the geometry projection method and the finite element method. The results indicate that the nanowire with a cambered top has the stronger emission in the forward direction, which is helpful to improve the photon collection efficiency. 相似文献
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Electronic structure and optical properties of the zinc-blende InxGa1 - xNyAs1-y system are calculated from the first-principles. Some relative simulations are performed using CA-PZ form of local density approximation in the framework of density functional theory. The supercell of intrinsic GaAs is calculated and optimized by using different methods, and the LDA-CA-PZ gives the most stable structure. The band gap of InxGa1 - xAs tends to decrease with the increasing In concentration. For the case of In0.0625Ga0.9375NyAs1 -y, the band gap will show slight difference when N concentration is larger than 18.75%. The optical transition of In dopant in GaAs exhibits a red shift, while it is a blue shift for the N dopant in InGaAs. Besides, dielectric function, reflectivity, refractive index and loss function in different doping model of InxGa1 - xNyAs1 - y are also discussed. 相似文献
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Influence of Strain-Reducing Layer on Strain Distribution of Self-Organized InAs/GaAs Quantum Dot and Redshift of Photoluminescence Wavelength 下载免费PDF全文
A systematic investigation about the strain distributions around the InAs/GaAs quantum dots using the finite element method is presented. A special attention is paid to influence of an Ino.2 Gao.sAs strain reducing layer. The numerical results show that the horizontal- and vertical-strain components and the biaz~ial strain are reinforced in the InAs quantum dot due to the strain-reducing layer. However, the hydrostatic strain in the quantum dot is reduced. In the framework of eight-band k · p theory, we study the band edge modifications due to the presence of a strain reducing layer. The results demonstrate that the strain reducing layer yields the decreasing band gap, i.e., the redshift phenomenon is observed in experiments. Our calculated results show that degree of the redshift will increase with the increasing thickness of the strain-reducing layer. The calculated results can explain the experimental results in the literature, and further confirm that the long wavelength emission used for optical fibre communication is realizable by adjusting the dependent parameters. However, based on the calculated electronic and heavy-hole wave function distributions, we find that the intensity of photoluminescence will exhibits some variations with the increasing thickness of the strain-reducing layer. 相似文献