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排序方式: 共有199条查询结果,搜索用时 62 毫秒
1.
Crystallographic characteristics and microwave dielectric properties of Ni-modified MgTa2O6 ceramics
Liang Shi Xueying Wang Rui Peng Gang Wang Cheng Liu Xiaolei Shi Dainan Zhang Huaiwu Zhang 《Ceramics International》2021,47(16):22514-22521
Ni2+ modified MgTa2O6 ceramics with a trirutile phase and space group P42/mnm were obtained. The correlations between crystallographic characteristics and microwave dielectric performance of MgTa2O6 ceramics were systematically studied based on the chemistry bond theory (PVL theory) for the first time. The results indicate that the introduction of Ni2+ causes a change in polarizability and the Mg–O bond ionicity, which contributes to the variation of dielectric constant. Moreover, the lattice energy, and packing fraction, full width at half maximum of the Raman peak of Ta–O bond, as the quantitative characterization of crystallographic parameters, regulate the dielectric loss of MgTa2O6 ceramics in GHz frequency band. In addition, the study of sintering behavior shows that the densification and micromorphology are the crucial factors affecting the microwave dielectric performance. Typically, Ni2+ doping on the A-site of MgTa2O6 can effectively promote the Q × f values to 173,000 GHz (at 7.43 GHz), which ensures its applicability in 5G communication technology. 相似文献
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Liang Shi Dainan Zhang Rui Peng Cheng Liu Xiaolei Shi Xueying Wang Huaiwu Zhang 《Journal of the European Ceramic Society》2021,41(11):5526-5530
Mg(1-x)ZnxTa2O6 (x = 0.00?0.08) dielectric ceramics were synthesized via the traditional solid-state reaction method. We used XRD and Rietveld refinement to demonstrate that a pure Mg(1-x)ZnxTa2O6 phase with trirutile structure was formed. Zn2+ substitution helped to decrease the Raman full width at half width of the A1g mode at 703 cm?1, which resulted in an increase in the order and rigidity of the TaO6 octahedron, this in turn contributed to improving the Q×f values. Additionally, the introduction of Zn2+ significantly promoted grain growth and increased the dense, and the molecular polarizability, these factors lead to a higher permittivity. Moreover, enhanced Ta-O bond energy resulted in a more stable TaO6 octahedron in the Mg(1?x)ZnxTa2O6 system, which contributed to enhanced τf values via substitution of Zn2+ doped on the A-site. Correspondingly, the microwave dielectric properties were significantly improved for 0.04-doped samples, obtaining: εr = 27, Q × f = 185,000 GHz (at 7.47 GHz), τf =32 ppm/°C. 相似文献
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Xing Zhang Cheng Liu Liang Shi Wenhao Xu Hongyang Zhang Rui Zeng Huaiwu Zhang 《Journal of the American Ceramic Society》2021,104(11):6054-6063
Ti4+-modified MgZrNb2O8 (MgZr1-xTixNb2O8, x = 0, 0.1, 0.2, 0.3, 0.4) ceramics were synthesized using the traditional solid-state reaction method. Pure MgZr1–xTixNb2O8 was detected without any secondary phase via the X-ray diffraction patterns. According to the sintering behavior and the surface morphology results, the introduction of Ti4+ reduced the sintering temperature and promoted the grain growth. The correlations between the dielectric properties and the crystal structure were analyzed through the Rietveld refinement and Raman spectroscopy. The slight shifts of the Raman peaks, corresponding to different vibration modes, were induced by the substitution of Ti4+ for Zr4+ and related to the improved quality factor. In general, the sample of MgZr0.9Ti0.1Nb2O8 sintered at 1320°C for 4 h exhibited promising microwave dielectric properties with an ultra-high Q × f value of 130 123 GHz (at 7.308 GHz, 20°C), which is potential for 5G communication applications. 相似文献
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微型膜状高频变压器的设计及性能分析 总被引:1,自引:0,他引:1
基于高频变换器的设计基础,建立了一套膜状高频变压器的设计算法,并成功地运用计算机实现了这些算法,建立了基于Windows3.X的膜状变压器设计软件;。按理论设计模型,制作了不同尺寸的微型膜状变压器,其Q值曲线,电感曲线和输出电压曲线反映出该变压器有良好的性能。 相似文献
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Yulan JING Huaiwu ZHANG lijun JIA Yu SHI Yingli LIUInstitute of Information Materials University of Electronic Science Technology of China Chengdu China 《材料科学技术学报》2004,20(1):35-37
A new nanometer-scale ferrite thin film with excellent high-frequency characteristics has been developed by the spray-spin-heating-coating method. The effects of the ion synthesis mechanism, chemical stoichiometry, fabrication method, and doping content on the magnetic properties and microstructure of the thin films have been analyzed. The films formed between 75℃ and 90℃ by spray-spin-heating-coating methods was discovered with fine grain size of about 21 nm, high saturation magnetization (4πMs) of about 6.5 kGs, coercivity of about 9.8 Oe, as well as initial permeability of about 14.0. These films can be widely used in radio-frequency integrated circuit devices. 相似文献
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当机械臂执行位置/力的混合跟踪任务时,位置控制一般用于机械臂的自由运动阶段,力控制一般用于约束运动阶段。这种位置/力切换的控制结构既能实现与环境接触前对机械臂位置的精确控制,也能保证接触后对期望控制力的准确跟踪。由于开关系统本身存在的切换不稳定性,机械臂在以一定的速度与环境接触时,机械臂执行器会在环境表面振动甚至弹跳。针对此问题,提出了一种半主动阻尼阻抗学习方法,该方法主要包含两部分:基于位置/力切换控制的半主动阻尼控制器;基于一种逆秩拟牛顿法(broyden fletcher goldfarb shanno,简称BFGS)的阻抗学习算法,根据学习到的环境参数调节半主动阻尼,实现机械臂在接触面的振动抑制和平稳过渡。在仿真及实验中,应用提出的方法让机械臂与不同环境交互,结果表明:该方法能很好地抑制接触过渡阶段的超调力,并防止机械臂在切换过程中的振动,实现了柔顺接触和平稳过渡。 相似文献
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