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141.
High‐Efficiency InP‐Based Photocathode for Hydrogen Production by Interface Energetics Design and Photon Management 下载免费PDF全文
Lu Gao Yingchao Cui Rene H. J. Vervuurt Dick van Dam Rene P. J. van Veldhoven Jan P. Hofmann Ageeth A. Bol Jos E. M. Haverkort Peter H. L. Notten Erik P. A. M. Bakkers Emiel J. M. Hensen 《Advanced functional materials》2016,26(5):679-686
The solar energy conversion efficiency of photoelectrochemical (PEC) devices is usually limited by poor interface energetics, limiting the onset potential, and light reflection losses. Here, a three‐pronged approach to obtain excellent performance of an InP‐based photoelectrode for water reduction is presented. First, a buried p–n+ junction is fabricated, which shifts the valence band edge favorably with respect to the hydrogen redox potential. Photoelectron spectroscopy substantiates that the shift of the surface photovoltage is mainly determined by the buried junction. Second, a periodic array of InP nanopillars is created at the surface of the photoelectrode to substantially reduce the optical reflection losses. This device displays an unprecedented photocathodic power‐saved efficiency of 15.8% for single junction water reduction. Third, a thin TiO2 protection layer significantly increases the stability of the InP‐based photoelectrode. Careful design of the interface energetics based on surface photovoltage spectroscopy allows obtaining a PEC cell with stable record performance in water reduction. 相似文献
142.
Isotropic Holographic Metasurfaces for Dual‐Functional Radiations without Mutual Interferences 下载免费PDF全文
The dual‐functional and/or multifunctional devices have huge fascinations and prospects to conveniently integrate complex systems with low costs. However, most of such devices are based on anisotropic media or anisotropic structures. Here, a new method is proposed to design planar dual‐functional devices using an isotropic holographic metasurface, in which two different functions are written on the same holographic interference pattern with no mutual coupling. When the metasurface is excited by two orthogonally ported sources, the corresponding dual functions can be controlled by the object waves, which are not affected by each other due to suppression of mutual interference. The proposed metasurface is composed of subwavelength‐scale isotropic metallic patches on a grounded dielectric. In this specific design, double‐beam and double‐polarization radiate devices are realized independently by the orthogonal excitations. Based on the theoretical analysis, scanning radiate beams that are only controlled by frequency with different performances under orthogonal polarizations are demonstrated. To the best of our knowledge, this is the first time for actualizing dual‐functional devices using isotropic textures. Full‐wave simulations and experimental results in the microwave frequencies are presented to validate the proposed theory and confirm the corresponding physical phenomena. 相似文献
143.
迭代树搜索(ITS)是一种有效的基于M-算法的软MIMO检测方案。然而ITS会遇到某些比特的对数似然比(LLR)无法确定的情况,虽可采用赋常数值方法(称为clipping)解决,但这会影响系统性能。为此,该文提出一种新的基于M-算法的软检测方案。该方案在树的每一级递推计算部分符号序列的后验概率,并基于此近似计算从第1级到该级的所有比特LLR,再采用M-算法保留部分符号序列延伸至下一级。该算法可确保每比特都可计算LLR,且能得到可靠性高的LLR值。考虑到某些比特LLR会多次计算,文中给出了算法的低复杂度实现。另外,该文还给出了一种计算符号序列后验概率的简单方法。最后,仿真结果表明所提算法相比ITS具有更好的性能,并使性能与复杂度达到较好的折中。 相似文献
144.
Zinc oxide (ZnO) thin films were grown on n-GaN/sapphire substrates by radio-frequency (RF) magnetron sputtering. The films were grown at substrate temperatures ranging from 400 to 700 ℃ for 1 h at a RF power of 80 W in pure Ar gas ambient. The effect of the substrate temperature on the structural and optical properties of these films was investigated by X-ray diffraction (XRD), atomic force microscopy (AFM) and photoluminescence (PL) spectra. XRD results indicated that ZnO films exhibited wurtzite symmetry and c-axis orientation when grown epitaxially on n-GaN/sapphire. The best crystalline quality of the ZnO film is obtained at a growth temperature of 600 ℃. AFM results indicate that the growth mode and degree of epitaxy strongly depend on the substrate temperature. In PL measurement, the intensity of ultraviolet emission increased initially with the rise of the substrate temperature, and then decreased with the temperature. The highest UV intensity is obtained for the film grown at 600 ℃ with best crystallization. oindent 相似文献
145.
SiC MESFET反向截止漏电流的研究 总被引:2,自引:0,他引:2
给出了一种减小SiC MESFET栅漏反向截止漏电流的工艺方法,通过采用LPCVD淀积厚SiO2和高温氧化工艺,使器件的性能得到一定的提升.从实验数据看出,器件在S波段工作时,器件的反向截止漏电流大幅度下降,且分散性得到改善,其功率附加效率和功率增益也分别提高了10%和1.5 dB.该方法充分发挥了SiC材料能形成自身氧化层的优势,结合Si工艺的特点,减小了氧化层的缺陷,并在一定程度上减小了器件的寄生电容. 相似文献
146.
OFDMA及其在IEEE802.16-2005中的应用 总被引:1,自引:0,他引:1
正交频分多址(OFDMA)是以正交频分复用(OFDM)调制为基础的新一代多址技术,具有很高的带宽利用率。文章介绍了它的基本原理,然后简单介绍了它在移动宽带无线接入中的应用,主要是关于信道编码,链路自适应技术,多天线技术。 相似文献
147.
This paper presents 3-D simulation of angled strike heavy-ion induced charge collection in domestic silicon-germanium heterojunction bipolar transistors (SiGe HBTs). 3D damaged model of SiGe HBTs single-event effects (SEE) is built by TCAD simulation tools to research ions angled strike dependence. We select several different strike angles at variously typical ions strike positions. The charge collection mechanism for each terminal is identified based on analysis of the device structure and simulation results. Charge collection induced by angled strike ions presents a complex situation. Whether the location of device ions enters, as long as ions track through the sensitive volume, it will cause vast charge collection. The amount of charge collection of SiGe HBT is not only related to length of ions track in sensitive volume, but also influenced by STI and distance between ions track and electrodes. The simulation model is useful to research the practical applications of SiGe HBTs in space, and provides a theoretical basis for the further radiation hardening. 相似文献
148.
摘要:作为火控产品,可靠性的设计已成为决定该产品生命力的重要指标。为此,主要介绍了光电隔离和变压器隔离两种信号隔离技术在某型火控计算机中的应用,该技术的应用对提高产品的可靠性起到了良好的效果。 相似文献
149.
150.
提出了一种光探测器芯片小信号等效电路模型及其建立方法,首先根据光探测器的物理结构确定其等效电路模型,模型考虑了影响光探测器高频性能的主要因素,然后精确测量了光探测器芯片的S参数,通过遗传算法对测量的S参数进行拟合,最终计算出模型的各个参量,在130MHz-20GHz范围内的实验结果表明,模型仿真结果与测量结果相吻合,证明了建模方法的可靠性。该模型有效地模拟了光探测器芯片的高频特性,利用该模型可以对光探测器及相应光电集成器件进行电路级仿真和优化。 相似文献