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排序方式: 共有514条查询结果,搜索用时 15 毫秒
21.
T. Koga X. Sun S.B. Cronin M.S. Dresselhaus K.L. Wang G. Chen 《Journal of Computer-Aided Materials Design》1998,4(3):175-182
Enhanced thermoelectric performance, expressed in terms of the thermoelectric figure of merit (ZT), has been predicted theoretically for low-dimensional electronic systems under appropriate experimental conditions. Enhanced ZT has been observed experimentally within 2D quantum wells of PbTe, and good agreement between theory and experiment has been obtained. The advantages of low-dimensional systems for thermoelectric applications are described, and prospects for further enhancement of ZT are discussed. 相似文献
22.
Polycrystalline Cd0.96Zn0.04Te thin films are deposited onto glass substrates (Corning 7059) kept at room temperature by vacuum evaporation. The films exhibit zinc blende structure with predominant (1 1 1) orientation. The rms roughness of the films evaluated by atomic force microscope is 3.7 nm. The band gap energy of the films measured by optical transmittance measurement is 1.539 eV. The photoluminescence (PL) spectrum of the films shows intense emission due to free and bound exciton recombination and no emission associated with crystal imperfection and PL line shapes give indications of the high quality of the layers. These films have been implanted with properly mass analyzed Boron ions (10B+) and the effect of implantation has been analyzed by X-ray diffraction, Raman scattering and optical transmittance measurements and the results are explained on the basis of the implantation induced surface roughness and lattice disorder. 相似文献
23.
A. Maghraby 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2007,262(1):46-50
There is a need for a sensitive dosimeter using electron paramagnetic resonance spectroscopy (EPR) for use in medical applications, since with this method non-destructive read-out and dose archival could be achieved. Sulfamic acid as a possible detector substance was investigated before and after irradiation, its EPR spectra were recorded and analyzed, some dosimetric characteristics were studied: microwave power saturation behavior, the effect of modulation amplitude on peak-to-peak signal intensity and the line width. Energy-dependence parameters were compared to soft tissue and alanine, and the response to ionizing radiation was studied, also the decay behavior along 133 days after irradiation is presented. It is found that sulfamic acid possesses high-sensitivity and reasonable signal stability which may make it useful as a sensitive dosimeter for medical applications. 相似文献
24.
分别采用溅射和蒸发镀膜法在Hg1-xMnxTe试样表面形成了Au/Hg1-xMnxTe和Al/Hg1-xMnxTe接触,并用Aligent4155c I-V测试仪对其I-V特性进行了测量,随后对试样在10%NH4F:10%H2O2:H2O中进行了钝化处理,并对处理后的试样再次进行了I-V测量,对于测试结果用热电子发射-扩散理论进行了分析.结果表明:Au与Hg1-xMnxTe形成了良好的欧姆接触,而Al与Hg1-xMnxTe形成了具有整流特性的肖特基接触,其肖特基势垒的理论推算值为0.38eV.钝化处理后的试样,其表面漏电现象明显降低,Au/Hg1-xMnxTe接触的电流下降幅度在0.1V时最大,为76.1%;而Al/Hg1-xMnxTe接触在0.2V时最大,为93.2%.随着偏压的进一步增大,两种接触的电流减小的幅度都逐渐变小. 相似文献
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27.
M. Daraselia C. H. Grein S. Rujirawat B. Yang S. Sivananthan F. Aqariden H. D. Shih 《Journal of Electronic Materials》1999,28(6):743-748
Optical real-time in-situ sensors play a very important role in the processing of semiconductor devices because of their noncontact remote nature and
excellent compatibility with UHV systems. In this work, we report on progress in developing an in-situ temperature sensor for HgCdTe structures grown by molecular beam epitaxy (MBE). Based on the Fourier transform infrared (FTIR)
spectrometer, this sensor is capable of continuous real-time monitoring of the surface temperature, thickness and alloy composition
of HgCdTe epilayers. The accuracy and sensitivity of this FTIR technique were studied in all temperature ranges of interest.
Also compared are two different methods of temperature determination obtained from the normalized spectral radiance. The influence
of stray radiation and of sample holder rotation on the measurement accuracy have been studied. Reflectivity spectra for HgCdTe/CdZnTe(211)
and HgCdTe/CdTe(211)/Si(211) structures have been analyzed in real time in order to determine the layer thickness and alloy
composition for growing layers. Also discussed is a multilayer-structure optical model developed to solve the problem of composition
determination at early stages of growth. The application of this model for fitting the transmission spectra is demonstrated. 相似文献
28.
Variable temperature Hall effect measurements have been made down to 9–10K on p-type Hg1−xCdxTe grown by liquid phase epitaxy on both CdTe and sapphire substrates. Carrier freeze-out was usually observed throughout
the measured temperature range. For most samples, the hole mobility was well-behaved and exhibited a maximum at ˜ 35K. Values
of acceptor ionization energy EA and donor concentration ND were estimated from the data, using a model assuming significant compensation, which provided a good fit to the low temperature
data. In addition, values of ND were also estimated from an analysis of the low temperature mobility using the hole effective mass as a parameter to provide
reasonable agreement between the ND values calculated from the Hall coefficient and mobility data. The measured carrier concentration is a result of close compensation
between stoichiometric acceptors and donors, with ND usually in the low-1017 cm−3 range. Average values of EA for as-grown, undoped x = 0.32 layers on CdTe and sapphire substrates are 7.4 and 6.6 meV, respectively. An activation energy
of 0.84 meV was determined for a Cu-doped x = 0.32 layer that was annealed in Hg vapor to reduce the number of Hg vacancies.
The average EA for undoped Hg-annealed x = 0.22 layers on CdTe substrates is 2.35 meV. Layers with x = 0.32 grown on sapphire substrates
have average carrier concentrations of 2.92 (σ = 0.54) × 1016 cm−3, compared with 4.64 (θ = 1.26) × 1016 cm−3 for the same composition layers grown on CdTe substrates. 相似文献
29.
用分析电子显微镜观察了碲镉汞晶体的显微结构。发现在大剂量电子辐射下,显微结构有较强的损伤。进一步用 X线能谱分析和高分辨电子显微术研究表明,大剂量电子辐射引起了碲镉汞晶体的超结构、叠栅、无序化和 Hg 含量减少。 相似文献
30.