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71.
进行了基于光纤预啁啾和自相位调制的多模/单模组合式全光纤啁啾谱压缩研究.提出利用多模光纤模式估计群速度色散均值的方法,并将该估计值作为啁啾参量分析的计算参数,仿真计算了50/125μm折射率渐变多模光纤的群速度色散均值及其与单模光纤在不同长度比值下的光谱压缩效果.采用三种折射率渐变多模光纤进行实验,对比分析了折射率渐变多模光纤的芯径大小及其与单模光纤的长度比值对光谱压缩效果的影响.实验结果表明使用50/125μm折射率渐变多模光纤获得光谱最大压缩比为5.796,谱宽为2.243 nm,与理论仿真一致;使用105/125μm折射率渐变多模光纤,可进一步提高压缩比至152.941,输出谱宽为0.085 nm的光脉冲.将此脉冲用于相干反斯托克斯拉曼散射光谱探测,理论光谱分辨率可达1.386 cm~(-1). 相似文献
72.
Liangshun Han Song Liang Can Zhang Liqiang Yu Lingjuan Zhao Hongliang Zhu Baojun Wang Chen Ji Wei Wang 《中国光学快报(英文版)》2014,12(9):91402-44
We report the fabrication of widely tunable ridge waveguide distributed Bragg reflector(DBR) lasers with InGaAsP butt-joint as grating material. The shape of the butt–joint interface is found to have significant effect on the properties of the lasers. It is shown that irregular mode jumps during wavelength tuning can be avoided by a V-shaped butt–joint interface. From the fabricated device, 23 channels with 0.8 nm spacing and greater than 35 dB side mode suppression ratios are obtained. The different tuning characteristics of the ridge waveguide and the previously reported buried ridge stripe DBR lasers are discussed. Combined with the wide tuning range and the simple structure, the ridge waveguide DBR lasers are promising for use in wavelength division multiplexing passive optical networks(WDM-PONs). 相似文献
73.
Ali Ghasemi Andrea Paesano Jr. Carla Fabiana Cerqueira Machado 《Journal of magnetism and magnetic materials》2012
Co1−xNix/2Srx/2Fe2O4 (x=0–0.5 in steps of 0.1) ferrite nanoparticles have been synthesized at room temperature, without calcination, using a reverse micelle process. The site preference was determined by Mössbauer spectroscopy at 300 K. The hyperfine parameters were obtained, for the whole series of solid solutions. For the X≤0.20 samples, the spectra were fitted with two discrete sextets and for the X>0.20 samples, a magnetic hyperfine field distribution and a doublet were also imposed in the fit procedure. Hysteresis loops were measured using a superconducting quantum interference device magnetometer at 2 K and 300 K. The results indicate that the relative decrease in saturation magnetization of nanoparticles compared to the submicron particles could be attributed to a surface spin termination and disorder. Magnetic dynamics of the nanoparticles was studied by the measurement of ac magnetic susceptibility versus temperature at different frequencies and it is found that the results are well described by the Vogel–Fulcher model. 相似文献
74.
S. Zerroug F. Ali Sahraoui N. Bouarissa 《Applied Physics A: Materials Science & Processing》2009,97(2):345-350
Using first principles total energy calculations within the full-potential linearized augmented plane wave method, we have
studied the structural and electronic properties of yttrium nitride (YN) in the three phases, namely wurtzite, caesium chloride
and rocksalt structures. The calculations are performed at zero and under hydrostatic pressure. In agreement with previous
findings, it is found that the favored phase for YN is the rocksalt-like structure. We predict that at zero pressure YN in
the rocksalt structure is a semiconductor with an indirect bandgap of 0.8 eV. A phase transition from a rocksalt to a caesium
chloride structure is found to occur at ∼134 GPa. Besides, a transition from an indirect (Γ−X) bandgap semiconductor to a direct (X−X) one is predicted at pressure of ∼84 GPa. For the electron effective mass of rocksalt YN, these are the first results, to
our knowledge. The information derived from the present study may be useful for the use of YN as an active layer in electronic
devices such as diodes and transistors. 相似文献
75.
This paper presents a new numerical model to investigate the vibro-acoustic behaviour of two laminated glass plates enclosing a thin viscothermal fluid cavity. The aim of this work is to develop an original five layer (two skins plies, two adhesive films and a core ply) laminated plate finite element by mixing Kirchhoff and Mindlin plate’s theory. The formulation is based on the theory that accounts for the transverse shear in the adhesive films and in the core. The acousto-elastic model is established in dimensionless appropriate form including the effects of viscosity and thermal conductivity of fluid and by taking into account the fluid-structure interaction. The discretization of the energy functional by finite element method gives after minimisation a symmetrical coupled matrix system in which the acoustic matrices are frequency dependent. Therefore, an iterative procedure is derived to determine the eigenmodes of the coupled system. The modal approach is adopted to determine the vibro-acoustic system’s response. Then, the validation of the new laminate finite element model is achieved by comparing the sandwich plate results against data obtained from literature. Subsequently, predicted responses, such as the vibration transmissibility and the transmission loss of the coupled system, for a given laminated double glazing under an imposed homogeneous pressure are presented and discussed. Numerical results show the importance of both lamination and viscothermal fluid effects on double glazing vibro-acoustic behaviour. 相似文献
76.
Temperature-insensitive Mach-Zehnder interferometric strain sensor based on concatenating two waist-enlarged fiber tapers 总被引:2,自引:0,他引:2
A novel temperature-insensitive strain sensor,based on an in-line Mach-Zehnder interferometer,is fabricated by concatenating two waist-enlarged fiber tapers separated by a short piece of photonic crystal fiber. The interference spectrum of the proposed sensor is analyzed in detail.Experimental results demonstrate that this sensor has a strain sensitivity of.3.02 pm/μεand maintains the temperature insensitivity feature. The proposed sensor has great potential in diverse sensing applications due to its advantages,such as its compact size,low cost,and simple fabrication process. 相似文献
77.
78.
79.
A simple and compact multi-wavelength tunable Brillouin fiber laser (BFL) in conjunction with dual-pass approach is proposed
and experimentally compared with the output of a conventional single ring cavity architecture. This BFL source is demonstrated
using 10 km long non-zero dispersion shifted fiber (NZ-DSF) as a Brillouin gain medium. By single ring cavity configuration,
odd-order Brillouin Stokes lines appear in the backward direction with the line spacing 0.16 nm (∼20 GHz) between each two
consecutive waves. However, this single ring cavity in conjunction with dual-pass configuration is able to generate Brillouin
Stokes lines with 0.08 nm spacing by providing bi-directional oscillations of Brillouin waves in both forward and backward
directions. With a Brillouin pump power of 15.3 dBm, approximately up to 17 Brillouin Stokes lines are generated which is
tunable over 40 nm tuning range. 相似文献
80.
Ali Akbar Ashkarran 《Applied Physics A: Materials Science & Processing》2012,107(2):401-410
Ag:ZnO hybrid nanostructures were successfully prepared by a twice arc discharge method in liquid. The visible light photocatalytic
activities were successfully demonstrated for the degradation of Rhodamine B (Rh. B), Methyl orange (MO), and Methylene blue
(MB) as standard organic compounds under the irradiation of 90 W halogen light for 2 h. The Ag:ZnO nanostructures were characterized
by X-Ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and ultraviolet-visible
absorption spectroscopy (UV-Vis). The results revealed that the Ag:ZnO nanostructures extended the light absorption spectrum
toward the visible region and significantly enhanced the Rh. B photodegradation under visible light irradiation. 3 mM Ag:ZnO
nanostructures exhibited highest photocatalytic efficiency. It has been confirmed that the Ag:ZnO nanostructures could be
excited by visible light (E<3.3 eV). The significant enhancement in the Ag:ZnO nanostructures photocatalytic activity under visible light irradiation
can be ascribed to the effect of physisorbed noble metal Ag by acting as electron traps in ZnO band gap. A mechanism for photocatalytic
degradation of organic pollutant over Ag:ZnO photocatalyst was proposed based on our observations. 相似文献