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121.
用光荧光(PL)和时间分辨光谱(TRPL)技术研究了GaAS/AIGaAS量子阱结构中荧光上升时间τf和激子谱线半宽(FWHM)随阱宽的变化关系,发现在窄阱中,τf,随阱宽的变化关系与宽阱时的情况恰恰相反,在窄阱中τf随着阱宽的减小而增加,归结为激子二维特性的退化导致声学声子对激子的散射作用减弱造成的.同时观测到窄阱中谱线半宽随着阱宽减小而增加,这也是因为激子特性由维二维向三维转化造成的. 相似文献
122.
123.
对As2和As4两种不同分子态下利用分子束外延技术(MBE)生长的单层AlGaAs薄膜和GaAs基InGaAs/AlGaAs量子阱红外探测器(QWIP)的性能进行了研究,发现As2条件下生长的单层AlGaAs材料荧光强度更大、深能级缺陷密度更低;相对于As4较为复杂的吸附、生长机制引入的缺陷,在As2条件下生长的InGaAs/AlGaAs QWIP具有更低的暗电流密度、更好的黑体响应、更高的比探测率和更优异的器件均匀性。生长制备的InGaAs/AlGaAs QWIP在60K的工作温度、-2V偏压下,暗电流密度低至7.8nA/cm2,光谱响应峰值波长为3.59μm,4V偏压下峰值探测率达到1.7×1011 cm·Hz1/2·W-1。另外,通过As元素的不同分子态下InGaAs/AlGaAs QWIP光响应谱峰位的移动可以推断出As元素的不同分子态也会影响In的并入速率。 相似文献
124.
F. A. Baiocchi T. Ambrose R. O. Miller S. Nakahara J. M. Brown C. L. Reynolds S. E. Lengle L. J. Peticolas 《Journal of Electronic Materials》1990,19(5):413-418
The Rutherford Backscattering (RBS) technique has been optimized for the measurement of thin (>85Å) alternating layers of A1(x)Ga(l-x)As and GaAs, which are at the limit of resolution of standard RBS measurements. RBS analysis of these structures provides both layer thicknesses and Al content. This information is useful for device processing since the layer thicknesses impact the FET threshold voltage and the Al content is important for proper selective chemical etching. Experimental conditions for the beam energy, detection angle, and sample rotation have been determined which allow measurement of the layer thicknesses to a precision of ±20-30Å (for layers >85A) and of the Al content,x, to a precision of ±.02. Comparison of the RBS data with Transmission Electron Microscopy (TEM), Cathodoluminescence (CL), and Reflection High Energy Electron Diffraction (RHEED) measurements on the same material showed very good agreement between the different techniques. The advantage of RBS is that it can measure much thinner layers than CL and it provides thickness and composition information at the same time whereas TEM only provides thickness for this particular material. RBS is currently used tocharacterize a monitor wafer from each day’s run to provide a processing baseline for the MBE growth. 相似文献
125.
We designed two transmission-mode GaAs/AlGaAs photocathodes with different AlxGa1-xAs layers, one has an AlxGa1-xAs layer with the Al component ranging from 0.9 to 0, and the other has a fixed Al component 0.7. Using the first-principle method, we calculated the electronic structure and absorption spectrum of AlxGa1-xAs at x=0, 0.25, 0.5, 0.75 and 1, calculation results suggest that with the increase of the Al component, the band gap of AlxGa1-xAs increases. Then we activated the two samples, and obtained the spectral response curves and quantum efficiency curves; it is found that sample 1 has a better shortwave response and higher quantum efficiency at short wavelengths. Combined with the band structure diagram of the transmission-mode GaAs/AlGaAs photocathode and the fitted performance parameters, we analyze the phenomenon. It is found that the transmission-mode GaAs/AlGaAs photocathode with variable Al component and various doping structure can form a two-stage built-in electric field, which improves the probability of shortwave response photoelectrons escaping to the vacuum. In conclusion, such a structure reduces the influence of back-interface recombination, improves the shortwave response of the transmission-mode photocathode. 相似文献
126.
We have studied the quantum transport of electrons in a three-step
single-barrier AlGaAs heterostructure under electric field. Using the
quantum transmitting boundary method and Tsu--Esaki approach, we have
calculated the transmission coefficient and current--voltage
characteristic.
The difference of the effective mass among the three barriers
is taken into account. Effects of the barrier width on transmission
coefficient and peak-to-valley current ratios are examined. The largest
peak-to-valley current ratio is obtained when the ratio of widths of the left,
middle, and right barrier is fixed at 4:2:1. The calculated results may
be helpful for designing devices based on three-step barrier
heterostructures. 相似文献
127.
采用气态源分子束外延(GSMBE)技术在InP衬底上生长发光波长为131μm的InAsP/InGaAsP应变补偿多量子阱和在GaAs衬底上生长GaAs/AlGaAs分布布拉格反射镜(DBR) ,并用直接键合技术将生长在InP基上的InAsP/InGaAsP应变补偿多量子阱结构组装到GaAs衬底上生长的DBR结构上,对其微结构和发光等特性进行了比较系统的研究.发现500~620℃的高温键合过程和后续的剥离工艺不仅没有引起量子阱发光效率的降低,反而由于键合过程中的退火改进了晶体质量,大大提高了量子阱的发光强度,其中620℃退火处理后的光致发光强度是原生样品的3倍. 相似文献
128.
Effect of AlGaAs barrier layer on the characteristics of InGaP/InGaAs/Ge triple junction solar cells
Sang Hyun Jung Chang Zoo Kim Dong Hwan Jun Wonkyu Park Ho Kwan Kang Jaejin Lee Hogyoung Kim 《Current Applied Physics》2014,14(11):1476-1480
As an effort to improve the conversion efficiency of InGaP/InGaAs/Ge triple junction solar cells, we investigated the effect of AlGaAs barrier layer on the cell performance under concentrated light condition. Three different solar cells having upper tunnel junctions (TJs) as n++-GaAs/p++-AlGaAs layers, n++-GaAs/p++-GaAs layers and n++-GaAs/p++-GaAs/p++-AlGaAs layers were prepared. Under concentrated light condition, open-circuit voltage (VOC), fill factor (FF) and conversion efficiencies were higher for the sample with an AlGaAs barrier layer than the samples without an AlGaAs barrier layer. For the sample with an AlGaAs barrier layer, external quantum efficiency was higher than other two samples. Most of all, the sample with a TJ as n++-GaAs/p++-GaAs layers showed a very poor electrical performance, which was associated with an imperfect crystalline quality of the InGaP top cell layers. 相似文献
129.
This paper shows the possibility to improve DC and RF electrical performances of AlGaAs/InGaAs PHEMTs by using low gamma radiation dose. The drain-source saturation current and the DC transconductance increase when the devices are irradiated with a gamma dose of 42.8 krad(GaAs) and then remain constant up to 0.85 Mrad(GaAs). This improvement is attributed to a reduction of access resistances. In the same time, the Schottky diode and the current-gain cut-off frequency of these components are not degraded by the gamma irradiation. Moreover, the maximum output power density is improved by 18%. This paper demonstrates that it is possible to improve the component electrical performances by using an original method. 相似文献
130.