全文获取类型
收费全文 | 20208篇 |
免费 | 1899篇 |
国内免费 | 693篇 |
专业分类
电工技术 | 132篇 |
技术理论 | 1篇 |
综合类 | 1068篇 |
化学工业 | 8479篇 |
金属工艺 | 3975篇 |
机械仪表 | 553篇 |
建筑科学 | 907篇 |
矿业工程 | 426篇 |
能源动力 | 242篇 |
轻工业 | 1058篇 |
水利工程 | 110篇 |
石油天然气 | 712篇 |
武器工业 | 78篇 |
无线电 | 335篇 |
一般工业技术 | 2574篇 |
冶金工业 | 1945篇 |
原子能技术 | 141篇 |
自动化技术 | 64篇 |
出版年
2024年 | 103篇 |
2023年 | 260篇 |
2022年 | 493篇 |
2021年 | 613篇 |
2020年 | 695篇 |
2019年 | 563篇 |
2018年 | 535篇 |
2017年 | 686篇 |
2016年 | 683篇 |
2015年 | 758篇 |
2014年 | 1086篇 |
2013年 | 1139篇 |
2012年 | 1285篇 |
2011年 | 1424篇 |
2010年 | 1054篇 |
2009年 | 1118篇 |
2008年 | 931篇 |
2007年 | 1283篇 |
2006年 | 1311篇 |
2005年 | 1132篇 |
2004年 | 977篇 |
2003年 | 766篇 |
2002年 | 656篇 |
2001年 | 561篇 |
2000年 | 509篇 |
1999年 | 398篇 |
1998年 | 355篇 |
1997年 | 225篇 |
1996年 | 221篇 |
1995年 | 175篇 |
1994年 | 169篇 |
1993年 | 124篇 |
1992年 | 98篇 |
1991年 | 65篇 |
1990年 | 71篇 |
1989年 | 67篇 |
1988年 | 25篇 |
1987年 | 33篇 |
1986年 | 24篇 |
1985年 | 16篇 |
1984年 | 30篇 |
1983年 | 25篇 |
1982年 | 28篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1979年 | 3篇 |
1976年 | 5篇 |
1975年 | 3篇 |
1959年 | 2篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(40):17737-17748
Due to problems such as pores on surface-treated coatings, the corrosion resistance of pure titanium bipolar plates for proton-exchange membrane fuel cells can be further improved by increasing the corrosion resistance of pure titanium by using differential speed-rolling (DSR); however, these materials have not yet reached the standard requirements of bipolar plates (corrosion current density icorr<103 nA·cm?2). In this work, the corrosion resistance of pure titanium was improved by optimizing the DSR process while the strength was maintained. The best corrosion resistance of the DSR pure titanium was achieved when the roller speed ratio was 2, while icorr was 429 nA·cm?2 in a solution of 0.5 M H2SO4 and 2 mg/L HF at room temperature. The formability of the DSR pure titanium for bipolar plates was verified. The optimal holding pressure range was 6.8–7.0 kN. 相似文献
2.
This study deals with the anodisation of titanium grade 2 in 0.5-M sulphuric acid using a pulsed signal in a unipolar regime. The electrical parameters investigated are voltage, frequency and duty cycle. The use of duty cycles with a high percentage of anodic polarisation (90%), combined with high frequencies (1000 Hz) and the higher voltage tested (220 V), favoured the establishment of a plasma regime involving strong dielectric discharges, allowing the growth of thicker oxides but with rough architecture. The corrosion resistance of the formed film has been characterised by potentiodynamic tests in 0.5-M NaBr for localised corrosion resistance and by immersion tests in 10% v/v sulphuric acid solution for a uniform corrosion assessment. Current–time curves, visual observations and electron microscope analysis (scanning electron microscopy, energy-dispersive X-ray spectroscopy) were the tools selected to provide a correlation between technological parameters and oxide growth mechanism. For localised and uniform corrosion, anodisation at 220 V with a high level of anodic polarisation (90%) and frequency (1000 Hz) was verified to be particularly advantageous. 相似文献
3.
Naw Rutha PAW Takuma KIMURA Tatsuo ISHIJIMA Yasunori TANAKA Yusuke NAKANO Yoshihiko UESUGI Shiori SUEYASU Shu WATANABE Keitaro NAKAMURA 《等离子体科学和技术》2021,23(10):105505-203
Titanium dioxide (TiO2) nanopowder (P-25;Degussa AG) was treated using dielectric barrier discharge (DBD) in a rotary electrode DBD (RE-DBD) reactor.Its electrical and optical characteristics were investigated during RE-DBD generation.The treated TiO2 nanopowder properties and structures were analyzed using x-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR).After RE-DBD treatment,XRD measurements indicated that the anatase peak theta positions shifted from 25.3° to 25.1°,which can be attributed to the substitution of new functional groups in the TiO2 lattice.The FTIR results show that hydroxyl groups (OH) at 3400 cm-1 increased considerably.The mechanism used to modify the TiO2 nanopowder surface by air DBD treatment was confirmed from optical emission spectrum measurements.Reactive species,such as OH radical,ozone and atomic oxygen can play key roles in hydroxyl formation on the TiO2 nanopowder surface. 相似文献
4.
There are many potential causes of corrosion in animal buildings. Animals exhale large quantities of moisture into the air creating high relative humidity in the building if the moisture is not properly vented. High humidity increases the potential for condensation. In addition, ammonia may be found in large quantities in animal buildings. Ammonia is released from manure and urine. In addition, ammonium chloride is used as a nitrogen source in fertilisers. In this study, the atmospheric corrosion of hot-dip-galvanised steel and zinc alloy-coated steel such as zinc–aluminium and zinc–aluminium–magnesium has been studied in atmospheres containing different levels of ammonia. Investigations have also been conducted at different levels of ammonium chloride. The results are discussed in view of the mechanisms of corrosion of zinc and zinc alloy-coated steel in ammonia and ammonium chloride-containing environments. 相似文献
5.
6.
7.
8.
This DFG-funded research project aimed to gain a better understanding of the mechanisms of the W-Cl repair principle within the framework of fundamental investigations, to contribute to the creation of the necessary basis for a broader application of the repair principle in practice. The focus was on the development of a model to describe the chloride redistribution after the application of a system sealing surface protective coating. On the basis of Fick's second law of diffusion, a mathematical model with a self-contained analytical solution was developed, with the help of which the chloride redistribution after application of a system sealing surface protective coating can be calculated under the idealized assumption of complete water saturation of the concrete. Furthermore, the influence of the dehydration of the concrete, expected as a result of the application of the repair principle W-Cl, on the chloride redistribution was investigated. On the basis of laboratory tests and numerical simulations, material-specific reduction functions were developed to quantify the relationship between the chloride diffusion coefficient and the ambient humidity. 相似文献
9.
10.
《稀有金属材料与工程》2019,36(1):25-29
研究了轧制变形量对WSTi544221合金棒材显微组织和力学性能的影响,并对Φ10 mm规格的棒材进行不同制度的固溶+时效处理,对比了不同热处理状态下棒材的组织和力学性能。结果表明,随着轧制变形量的增大,WSTi544221合金棒材的晶粒细化程度增大,强度逐渐提高,但塑性变化不大。经870℃×1 h/WC+520℃×6 h/AC固溶+时效处理后,强度与塑性可以获得良好匹配,当抗拉强度达到1 610 MPa、屈服强度达到1 531 MPa时,延伸率和断面收缩率可分别保持在12%和43%。 相似文献