全文获取类型
收费全文 | 2294篇 |
免费 | 287篇 |
国内免费 | 99篇 |
专业分类
电工技术 | 59篇 |
综合类 | 131篇 |
化学工业 | 686篇 |
金属工艺 | 221篇 |
机械仪表 | 38篇 |
建筑科学 | 46篇 |
矿业工程 | 133篇 |
能源动力 | 72篇 |
轻工业 | 57篇 |
水利工程 | 1篇 |
石油天然气 | 35篇 |
武器工业 | 1篇 |
无线电 | 310篇 |
一般工业技术 | 538篇 |
冶金工业 | 294篇 |
原子能技术 | 13篇 |
自动化技术 | 45篇 |
出版年
2024年 | 8篇 |
2023年 | 39篇 |
2022年 | 39篇 |
2021年 | 69篇 |
2020年 | 78篇 |
2019年 | 70篇 |
2018年 | 55篇 |
2017年 | 108篇 |
2016年 | 82篇 |
2015年 | 90篇 |
2014年 | 104篇 |
2013年 | 113篇 |
2012年 | 156篇 |
2011年 | 195篇 |
2010年 | 102篇 |
2009年 | 134篇 |
2008年 | 113篇 |
2007年 | 182篇 |
2006年 | 141篇 |
2005年 | 117篇 |
2004年 | 87篇 |
2003年 | 89篇 |
2002年 | 80篇 |
2001年 | 79篇 |
2000年 | 62篇 |
1999年 | 43篇 |
1998年 | 39篇 |
1997年 | 27篇 |
1996年 | 29篇 |
1995年 | 15篇 |
1994年 | 35篇 |
1993年 | 13篇 |
1992年 | 15篇 |
1991年 | 13篇 |
1990年 | 16篇 |
1989年 | 9篇 |
1988年 | 3篇 |
1987年 | 8篇 |
1986年 | 5篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1977年 | 1篇 |
排序方式: 共有2680条查询结果,搜索用时 15 毫秒
31.
32.
Abstract— Coatings of indium tin oxide (ITO) nanoparticles on different flexible polymer substrates were investigated with respect to the achievable sheet resistance and their electrical behavior under oscillatory bending. As substrate materials, polyethyleneterephthalate (PET), polyethylenenaphthalate (PEN), polyetheretherketone (PEEK), and polyimide (PI) were chosen, the surface resistances on the different polymer substrates were compared as a function of annealing temperature and surface topography. The surface topography, which has a strong influence on the surface resistance, was characterized by means of a white‐light confocal (WL‐CF) microscope. On the PET substrate, which exhibits the smoothest surface, the coating of ITO nanoparticles shows the lowest sheet resistance of 2 kΩ/□ for a layer thickness of 3 μm and an annealing temperature of 200°C. Furthermore, the electrical behavior of coatings of ITO nanoparticles under oscillatory bending was investigated using a special device. These coatings show a cyclic change of the conductivity which can be explained by an alternating compression and extension of crack flanks under the applied stress. Due to the growing number of cracks with increasing number of cycles, a decrease of the conductivity is observed in the bent state as well as in the balanced state. For a small bending radii, the decrease of the conductivity is stronger due to more cracks caused by the higher tensile stresses in the layer. The electrical behavior of the coatings of the annealed ITO nanoparticles on PET films under oscillatory bending was compared with commercially available sputtered ITO coatings. The annealed coatings of ITO nanoparticles demonstrate better electrical properties under oscillatory bending than coatings of sputtered ITO. The different electrical behavior under oscillatory bending can be related to differences in crack formation. 相似文献
34.
铁矿石经HCl-KF HCO4溶样后,用二氯化锡还原Fe^3 为Fe^2 ,以甲基橙做指示剂指示还原终点,肺铈量法测定铁矿石中全铁的含量。方法简便,快速,终点每锐,精密度好,准确度高。 相似文献
35.
M. V. Peralta-Martinez M. J. Assael M. J. Dix L. Karagiannidis W. A. Wakeham 《International Journal of Thermophysics》2006,27(3):681-698
New measurements of the thermal conductivity of molten mercury, gallium, tin, and indium are reported up to 750 K. The measurements are performed in a novel transient hot-wire instrument described elsewhere. The present experimental technique overcomes problems of convection, and it is shown that it operates in an absolute way in accord with a theoretical model. The uncertainty of the thermal conductivity results is estimated to be ± 2%, which is superior to that achieved in most earlier work. The low uncertainty of the present experimental results has allowed us to test the only significant theory for the thermal conductivity of molten metals, which relates this property to the electrical conductivity. The pattern of results among the four metals indicates that further theoretical developments would be warranted. 相似文献
36.
A study on the low-temperature CO gas sensors based on Au/SnO2 thick film was reported. Au/SnO2 powders, with different Au loading from 0.36 to 3.57 wt%, were prepared by a deposition-precipitation method. Thick films were fabricated from Au/SnO2 powders. The Au/SnO2 thick-film sensors exhibited high sensitivity to CO gas at relatively low operating temperature (83-210 °C). We also reported the effect of the Au loading in Au/SnO2 on the CO gas sensing behavior. The optimal Au loading in as-prepared Au/SnO2 was 2.86 wt%. 相似文献
37.
AgSnO2触头材料在直流灯负载下的电侵蚀特点 总被引:1,自引:2,他引:1
通过模拟实验机对直流灯负载下汽车继电器用银氧化锡(AgSnO2)系列触头材料进行电性能实验。观察了不同成分、不同工艺的银氧化锡触头材料的电侵蚀情况,总结分析了它们在实验中表现出的电侵蚀特点。指出了影响银氧化锡触头材料电性能的主要因素。 相似文献
38.
苯芴酮-溴代十六烷基三甲胺分光光度法测定析出铅中的锡 总被引:2,自引:0,他引:2
用硝酸-酒石酸分解试样,在含有酒石酸(0.16mol/L)的盐酸溶液中,锡(Ⅳ)与苯芴酮-溴代十六烷基三甲胺(CTMAB)生成有色络合物,采用分光光度法直接测定析出铅中的锡.此络合物在波长530nm处有最大的吸光度,摩尔吸光系数ε=6.74×104,锡(Ⅳ)含量为0.25~80μg/50mL,符合比尔定律.该法快速、准确、重现性好,适应于析出铅中含锡0.005%~1.60%的测定. 相似文献
39.
Indium tin oxide (ITO) films with a smooth surface (root-mean-square roughness; Rrms=0.40 nm) were made using a combination of the deposition conditions in the ion beam-sputtering method. Sheet resistance was 13.8 Ω/sq for a 150-nm-thick film grown at 150 °C. Oxygen was fed into the growth chamber during film growth up to 15 nm, after which, the oxygen was turned off throughout the rest of the deposition. The surface of the films became smooth with the addition of ambient oxygen but electrical resistance increased. In films grown at 150 °C with no oxygen present, a rough surface (Rrms=2.1 nm) and low sheet resistance (14.4 Ω/sq) were observed. A flat surface (Rrms=0.5 nm) with high sheet resistance (41 Ω/sq) was obtained in the films grown with ambient oxygen throughout the film growth. Surface morphology and microstructure of the films were determined by the deposition conditions at the beginning of the growth. Therefore, fabrication of ITO films with a smooth surface and high electrical conductivity was possible by combining experimental conditions. 相似文献
40.
本文通过X—射线衍射分析及阻温特性别定等方法研究了SnO2导电陶瓷的晶相组成和电性能与烧成温度的关系。结果表明,随烧成温度提高试样中SnO2金红石型晶体的含量有所增加,试样的材料常数和活化能降低,材料导电性能增强,同时还对导电陶瓷的导电机理进行了探讨。 相似文献