全文获取类型
收费全文 | 112篇 |
免费 | 5篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 21篇 |
综合类 | 5篇 |
化学工业 | 13篇 |
金属工艺 | 21篇 |
机械仪表 | 3篇 |
建筑科学 | 1篇 |
矿业工程 | 2篇 |
能源动力 | 4篇 |
轻工业 | 9篇 |
石油天然气 | 2篇 |
武器工业 | 1篇 |
无线电 | 6篇 |
一般工业技术 | 15篇 |
冶金工业 | 6篇 |
自动化技术 | 13篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 5篇 |
2020年 | 2篇 |
2019年 | 6篇 |
2018年 | 5篇 |
2017年 | 3篇 |
2015年 | 3篇 |
2014年 | 9篇 |
2013年 | 9篇 |
2012年 | 2篇 |
2011年 | 2篇 |
2010年 | 8篇 |
2009年 | 7篇 |
2008年 | 8篇 |
2007年 | 15篇 |
2006年 | 9篇 |
2005年 | 2篇 |
2004年 | 2篇 |
2003年 | 6篇 |
2002年 | 1篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有122条查询结果,搜索用时 15 毫秒
101.
Effect of sintering temperature and composition on microstructure and properties of PMS-PZT ceramics
The piezoelectric ceramics xPb(Mn1/3Sb2/3)O3-(1-x)Pb(Zr1/2Ti1/2)O3 (abbreviated as PMS-PZT) were synthesized by traditional ceramics process. The effect of sintering temperature and the amount of Pb(Mn1/3Sb2/3)O3 (abbreviated as PMS) on phase structure, microstructure, piezoelectric and dielectric properties of PMS-PZT ceramics was investigated. The results show that the pure perovskite phase is in all ceramics specimens, the phase structure of PMS-PZT ceramics changes from tetragonal phase to single rhombohedral phase with the increasing amount of PMS. The dielectric constant εr, Curie temperature Tc, electromechanical coupling factor kp and piezoelectric constant d33 decrease, whereas the mechanical quality factor Qm and dielectric loss tanδ increase with the increasing amount of PMS in system. The optimum sintering temperature is 1 200-1 250 ℃. It is concluded that the PMS-PZT (x=0.07) ceramics sintered at 1 250 ℃ is suitable for high-power piezoelectric transformer. These properties include εr=674.8, tanδ =0.005 25, kp=0.658, Qm= 1 520, d33=230 pC/N, Tc=275 ℃. 相似文献
102.
PLC控制系统的抗干扰分析 总被引:2,自引:0,他引:2
首先分析了PLC控制系统中干扰信号的来源、成因,并从硬件电路设计、软件程序编制、PLC选型、电缆布线等诸多方面研究探讨提高PLC控制系统抗干扰能力的方法和措施。随着PLC在自动控制领域的日益普及,这些方法和措施对于提高PLC控制系统的抗干扰能力具有重要的经济意义和实用价值。 相似文献
103.
YAl3 (BO3)4: Eu^3+ phosphors were prepared by the conventional solid state reaction. The phase structure and morphology were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). Doping YAl3(BO3)4: Eu^3+ phosphors with concentration of Eu^3+ ions of 0, 2, 5, 8 and 10 mol% were studied and their luminescent properties at room temperature were discussed. The excitation spectrum of Y0.95Eu0.05Al3(BO3)4 was composed of a broad band centered at about 252 nm and a group of lines in the longer wavelength region. In the emission spectra, the peak wavelength was about 614 nm under a 252 nm UV excitation. The optimal doping concentration of Eu^3+ ions in YAl3(BO3)4: Eu^3+ phosphors was 8 mol%. 相似文献
104.
采用机械共混法制备了淀粉/丙烯酸钠(NaAA)/氯丁橡胶(CR)吸水复合材料,考察了去离子水和3.5%(质量分数)NaCl溶液两种吸水介质对其力学性能和吸水性能的影响,并且观察了复合材料吸水前后的微观形貌。结果表明浸水后,随吸水量的增加,材料力学性能的降低;复合材料在盐溶液中的吸水率远小于在去离子水中的吸水率;在反复使用过程中,能够很好地保持其原有的吸水性能,具有优异的反复使用性能;通过扫描电子显微镜(SEM)观察了复合材料吸水前后的微观形态结构,吸水组分聚NaAA颗粒吸水干燥后表面发生褶皱。 相似文献
105.
106.
107.
108.
109.
Alkali metal(Li, Na, K) doped ZnO powders were synthesized by solid-state reaction at different calcination temperatures and holding time. Effects of holding time and K sources on the infrared emissivity of ZnO were investigated. The structure and surface morphologies of samples were characterized by X-ray diffraction(XRD) and scanning electron microscopy(SEM). The UV-Vis absorption and infrared emissivities were investigated by a UV-Vis spectrophotometer and an infrared emissometer, respectively. XRD patterns confirm the wurtzite structure of the as prepared samples with single phase. Smooth grain surfaces are detected in all doped ZnO samples, while ZnO:Li and ZnO:Na present the aggregation of grains. The redshifts in the optical band-gap are observed in K-, Na-, and Li-doped ZnO with the values 3.150, 3.144, and 3.142 eV. Due to better crystalline quality, ZnO:K shows a lower emissivity than others. The emissivity of K-doped ZnO decreases to the minimum value(0.804), at 1200 °C and holding 2 h. Compared with KNO3 as K source, K2CO3 doped ZnO has lower emissivities. 相似文献
110.