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排序方式: 共有430条查询结果,搜索用时 203 毫秒
21.
22.
J. Gaca M. Wójcik A. Jasik K. Pierściński M. Kosmala A. Turos A. M. Abdul-Kaderd 《Opto-Electronics Review》2008,16(1):12-17
GaAs/AlAs Bragg mirrors on GaAs with varied number of layer pairs were grown, by molecular beam epitaxy (MBE), to be applied
for semiconductor saturable absorber mirrors (SESAMs) and intensity modulators. Due to the random variation of the growth
rate, substrate surface roughness, and interdiffusion at the interfaces, precise control of the growth conditions of deposited
layers poses a serious problem. Usually, thickness variations and composition grading at the heterointefaces result in variations
of the mirror reflectivity. In this paper, the high resolution X-ray diffraction (HRXRD), optical reflectance, Rutherford
backscattering/channelling (RBS), supported by numerical evaluation methods were employed to determine both the exact thickness
of each layer and the composition grading at the interface between succeeding layers of GaAs/AlAs-based mirrors. To reduce
ambiguity and to speed up the analysis, the rocking curves and RBS spectra were simulated concurrently, using results of one
simulation to verify the others. This process was carried out until the best fit between experimental and calculated curves
was achieved. The complementary use of both methods results in improved sensitivity and makes the whole process of evaluation
of the thickness variation of each layer and the size of the composition grading at the interfaces less time consuming. 相似文献
23.
24.
WANG Zhanshan WANG Fengli ZHANG Zhong CHENG Xinbin QIN Shuji & CHEN Lingyan Institute of Precision Optical Engineering Department of Physics Tongji University Shanghai China 《中国科学G辑(英文版)》2005,48(5):559-574
With the development of the multiplayer technology, the multilayer mirrors have been widely used in many fields, such as the soft X-ray astronomical telescope, soft X-ray microscopy, extreme ultraviolet lithography, applications of synchrotron radiation, plasma diagnosis, and so on. However, in the hard X-ray region, especially for the wavelength shorter than 0.1 nm, the optical elements based on the traditional multilayers or the single high-Z metal coatings cannot accommodate the advancemen… 相似文献
25.
Xu Xiaoyong Zheng Guoguang Wang Qing-an 《Journal of Quantitative Spectroscopy & Radiative Transfer》2005,92(1):61-72
This paper experimentally and theoretically examines the scattering properties of simulated non-spherical hydrometeors including water oblates, ice oblates and ice sphere-cone-oblates, in terms of the backscattering cross-section and the differential reflectivity. The experimental measurements of the backscattering cross-sections of non-spherical hydrometeor samples were performed in the Electromagnetic Scattering Laboratory of China National Space Industrial Corporation. Meanwhile, the backscattering cross-sections have been computed with the transition (T) matrix method. The theoretical results are compared with the experimental data, showing that the calculations are consistent with the observations in general. Experimental and theoretical analyses indicate that the backscattering cross-section of non-spherical particles increases as the particle size parameter increases, and fluctuates when the sizes are larger under the effect of resonance scattering. Differential reflectivity ZDR of water oblates in natural rainfall is always greater than 0 dB whereas ZDR of hailstones may be negative. There is a good linear relationship between differential reflectivity and aspect ratio of a particle. These derivations agree with the literature and can be used to identify the presence of hail particles and distinguish between plate-type and columnar-type hydrometeors. In this study, the measuring experiment and the T-matrix method calculations for the scattering of simulated raindrop and ice particles are also briefly described. 相似文献
26.
研究了一种新型光纤环镜(FLM)的原理与特性,这种FLM由在普通光纤环镜中插入光纤型偏振控制器(PC)构成.通过等效光路分析建立了该FLM的理论模型,并对其反射特性进行了数值模拟.研究表明,通过改变PC的状态,即改变其双折射效应的快轴取向或强度,可连续调节FLM的反射率,反射率谱具有宽带特性,主要受光纤耦合器工作带宽的影响.此外,对FLM的反射特性还进行了实验研究.实验结果也证实,通过调节PC状态,FLM反射率可在其最大和最小值之间连续调节,实验测得FLM最大和最小反射率分别可达93%和2%.根据PC双折
关键词:
光纤环镜
偏振控制器
光纤耦合器
反射率 相似文献
27.
以GaAs材料为例,研究了半导体远红外反射镜中的反射率和相位.通过拟合不同掺杂浓度下样品的远红外反射谱,得到了自由载流子的弛豫时间随掺杂浓度变化的经验公式,并把该规律应用到数值计算中.详细讨论了反射镜的结构和材料参数对反射率R和相位φ的影响.根据腔体内吸收率最高的判据得到了最优的反射镜的参数,并计算了这种优化后的反射镜的波长选择特性.最后,通过远红外反射光谱的测量,从实验上验证了这种反射镜的实际效果. 所得结论为半导体远红外器件中的反射镜设计提供了参考.
关键词:
远红外反射镜
反射率
相位 相似文献
28.
We study the growth of Fe films on GaAs(1 0 0) at a low temperature, 140 K, by in situ X-ray reflectivity (XRR) using synchrotron radiation. The XRR curves are well modeled by a single Fe layer on GaAs both at the growth temperature and after annealed at the room temperature. We found that the surface became progressively rougher during the growth with the growth exponent, βS = 0.43 ± 0.14. The observed βS is attributed to the restricted interlayer diffusion at the low growth temperature. The change of the interface width during growth was minimal. When the Fe film was annealed to room temperature, the surface smoothed, keeping the interface width almost unchanged. The confinement of the interface derives from that the diffusion of Ga and As proceeds via the inefficient bulk diffusion, and the overlying Fe film is kinetically stabilized. 相似文献
29.
30.
The roughening of interfaces as a function of layer thickness and magneto transport properties have been investigated on sputter-deposited Fe/Ni75B25 multilayer films. X-ray reflectivity data were recorded for Ni75B25(72 nm) film and for [Fe(2 nm)/Ni75B25(2 nm)]16 and [Fe(4 nm)/Ni75B25(4 nm)]8 multilayer films. A power law dependence of the interfacial width of growing Fe/Ni75B25 interfaces was observed. The resulting growth exponents β were found to be in the range of 0.55–0.58 in the initial growth stage of the multilayer with lower Fe/Ni75B25 repetition thickness and at approximately 0.34 for multilayer with higher repetition thickness. The growth exponents were compared with theoretical calculations. High resolution electron microscopy revealed the columnar growth of the Fe/Ni75B25 multilayer. Additionally, an increase of magnetoresistance was observed by the multilayering of Ni75B25 films with Fe interlayers. 相似文献