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1.
SiO2包覆Y2O3∶Er3+纳米粉的制备及发光性能   总被引:3,自引:3,他引:0  
用微乳液法合成出SiO2包覆的Er3+掺杂的Y2O3粉体。X射线衍射结果表明,所制备粉体为立方Y2O3结构。透射电镜照片显示,其颗粒形状近似为球形,粒径为20~50 nm。该粉体在波长为980 nm的半导体激光器激发下发射出中心波长为562 nm的绿色和660 nm的红色上转换荧光,分别对应于Er3+离子的4S3/2/2H11/2→4I15/2跃迁和4F9/2→4I15/2跃迁,发光强度和激发功率的关系揭示其均为双光子过程。Er3+掺杂的Y2O3粉体具有高效的上转换发光性能,而经过纳米复合后制成的Y2O3(核)/SiO2(壳)在水溶液中具有较好的悬浮性,这对于其在生物荧光标记的应用具有重要意义。  相似文献
2.
键合型铕-十一烯酸-硅橡胶复合材料的合成及其荧光性能   总被引:2,自引:1,他引:1  
纪乐  王庭慰  张其土 《发光学报》2011,32(2):134-137
以铕-十一烯酸配合物和含氢硅油为原料,在铂催化剂作用下制备稀土有机硅加成产物。对产物进行红外光谱和核磁共振分析。结果表明,配合物键接在有机硅高分子主链上,加成产物为一种键合型的铕-十一烯酸-硅橡胶复合材料。荧光光谱分析确定复合材料的最佳激发波长为393 nm;最强发射波长为616 nm,为铕离子的特征发射。同时,随着铕离子浓度的增大,复合材料没有荧光猝灭现象。  相似文献
3.
中波红外景象投影光学系统消热差设计   总被引:2,自引:2,他引:0  
针对红外成像系统性能测试与评估的应用需求,设计了一套基于数字微镜器件的消热差的中波红外景象投影光学系统.探讨了红外视景仿真用投影光学系统的像差特性和设计方法,并对投影系统的无热化进行了分析.采用分光板和补偿板方案,解决了大相对孔径条件下投影系统的远心照明分光和像差平衡问题,提高了分辨率和均匀性,增大了视场.系统由远心投影光学系统和像面倾斜的柯勒照明光学系统组成,使用光学被动消热差,提高了系统的稳定性.系统焦距为255mm,F/#为2.6,视场5.1°,出瞳距200mm,在空间频率17lp/mm处,在-20℃~60℃全温度范围内MTF>0.6,接近衍射极限.本文所设计的投影光学系统具有分辨率高、均匀性好、结构紧凑等优点.  相似文献
4.
基于光谱角度匹配方法提取黑土边界   总被引:2,自引:0,他引:2  
在RS与GIS环境下,用土地利用、土壤图等获取遥感监督分类的感兴趣区,基于MODIS反射率产品、运用光谱角度匹配等方法进行黑土边界提取研究.结果表明:基于MODIS反射率数据的土壤遥感分类方法,可以提取黑龙江省黑土边界,光谱角度匹配方法分类结果最好,黑龙江省黑土带北部分类精度高于南部;由于植被覆盖、光谱特征相似等原因,其他土壤分类结果相对较差;由于东北地区裸土时间相对较长,MODIS的高时间分辨率特性有利于提高土壤遥感分类精度;在GIS的支持下,充分利用辅助信息选择遥感分类的感兴趣区,可以提高土壤遥感分类精度;引入地形、气候等信息,分类精度得到显著提高、提取的黑土边界信息更准确.  相似文献
5.
Supercapacitor devices using porous silicon electrodes   总被引:1,自引:0,他引:1  
Electrical double layer (EDL) supercapacitors have been constructed using gold coated porous silicon (PSi) electrodes in a 0.25 M TEABF4/PC solution. As a comparison with the PSi, graphite paper, carbon cloth and ITO on glass electrodes have also been tested using the same electrolyte. The capacitors have been characterised using a.c. impedance spectroscopy and cyclic voltammetry (normal staircase mode). Devices using PSi electrodes showed a capacitance of approximately 0.2 mF cm−2 (equivalent to 5 mF g−1). In comparison, devices based on ITO on glass electrodes had a capacitance of 0.76 mF cm−2. Those based on graphite-paper electrodes gave 10 mF cm−2 (equivalent to 131 mF g−1) and those using carbon cloth gave 600 mF cm−2 (equivalent to 35 F g−1). Paper presented at the 6th Euroconference on Solid State Ionics, Cetraro, Calabria, Italy, Sept. 12–19, 1999.  相似文献
6.
Measurements are reported of the photoemission spectra and absolute yield of thin films of Eu, Ba and Yb for the photon energy range 2 to 21 eV. Transitions from the occupied 4f-states in Eu and Yb have been observed and the binding energies deduced. The excitation probability of the 4f electrons is found to be very low and an explanation based on their atomic-like nature is given. Transitions involving valence band states are compared with predictions based on published energy band schemes and the density of states for the unoccupied 5d band in Yb is deduced. The effect of chemisorbed oxygen on Ba and Eu surfaces is reported.  相似文献
7.
Accurate auxiliary field quantum Monte-Carlo (AFQMC) simulations of interacting electrons in quantum dots are reported. Two different formulations of this approach are presented both of which have been designed specifically for application to quantum dots. A deflation technique for calculation of anti-symmetrized traces is introduced. The auxiliary field is sampled with a hybrid algorithm and the artificial dynamics needed for use with the present formulation of AFQMC is described. The constrained path approximation is used to control the sign problem. Results for the ground state energy of two spin-polarised, interacting electrons are presented and are found to agree well with exact diagonalization results for a wide range of screening lengths. The sign problem does not appear in the regime of small screening length.  相似文献
8.
We have used cross-sectional scanning-tunneling microscopy (X-STM) to compare the formation of self-assembled InAs quantum dots (QDs) and wetting layers on AlAs (1 0 0) and GaAs (1 0 0) surfaces. On AlAs we find a larger QD density and smaller QD size than for QDs grown on GaAs under the same growth conditions (500 °C substrate temperature and 1.9 ML indium deposition). The QDs grown on GaAs show both a normal and a lateral gradient in the indium distribution whereas the QDs grown on AlAs show only a normal gradient. The wetting layers on GaAs and AlAs do not show significant differences in their composition profiles. We suggest that the segregation of the wetting layer is mainly strain-driven, whereas the formation of the QDs is also determined by growth kinetics. We have determined the indium composition of the QDs by fitting it to the measured outward relaxation and lattice constant profile of the cleaved surface using a three-dimensional finite element calculation based on elasticity theory.  相似文献
9.
10.
An error analysis of two-wavelength absorption-based fibre-optic sensors is presented in this paper. A general formulation to express the measurement error and the error induced by the instability of the light power input into the absorbing sample to be measured is derived. Using this formulation, two common and important errors in this type of sensor, temperature fluctuation of light sources and bending optical fibres, are numerically discussed as illustrative examples. The analyses can be applied to both transmission-type and reflection-type absorption-based fibre-optic sensors.  相似文献
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