全文获取类型
收费全文 | 47238篇 |
免费 | 4068篇 |
国内免费 | 2117篇 |
专业分类
电工技术 | 2835篇 |
综合类 | 3160篇 |
化学工业 | 9641篇 |
金属工艺 | 9193篇 |
机械仪表 | 5229篇 |
建筑科学 | 3793篇 |
矿业工程 | 1454篇 |
能源动力 | 1379篇 |
轻工业 | 2654篇 |
水利工程 | 848篇 |
石油天然气 | 1573篇 |
武器工业 | 383篇 |
无线电 | 2169篇 |
一般工业技术 | 5591篇 |
冶金工业 | 2381篇 |
原子能技术 | 269篇 |
自动化技术 | 871篇 |
出版年
2024年 | 301篇 |
2023年 | 993篇 |
2022年 | 1770篇 |
2021年 | 1995篇 |
2020年 | 1779篇 |
2019年 | 1442篇 |
2018年 | 1433篇 |
2017年 | 1964篇 |
2016年 | 1813篇 |
2015年 | 1758篇 |
2014年 | 2386篇 |
2013年 | 2468篇 |
2012年 | 2953篇 |
2011年 | 3294篇 |
2010年 | 2350篇 |
2009年 | 2704篇 |
2008年 | 2188篇 |
2007年 | 2768篇 |
2006年 | 2769篇 |
2005年 | 2242篇 |
2004年 | 1952篇 |
2003年 | 1633篇 |
2002年 | 1384篇 |
2001年 | 1200篇 |
2000年 | 1011篇 |
1999年 | 878篇 |
1998年 | 723篇 |
1997年 | 664篇 |
1996年 | 515篇 |
1995年 | 499篇 |
1994年 | 375篇 |
1993年 | 257篇 |
1992年 | 214篇 |
1991年 | 174篇 |
1990年 | 131篇 |
1989年 | 114篇 |
1988年 | 85篇 |
1987年 | 62篇 |
1986年 | 30篇 |
1985年 | 25篇 |
1984年 | 28篇 |
1983年 | 19篇 |
1982年 | 23篇 |
1981年 | 7篇 |
1980年 | 12篇 |
1979年 | 5篇 |
1961年 | 2篇 |
1960年 | 3篇 |
1959年 | 6篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
72.
文章叙述了新型镍基耐蚀哈氏合金G-30在不同介质中的耐蚀性能以及工业应用,综合分析了该合金应用的经济性及前景。 相似文献
73.
74.
Janne Halme Minna Toivola Antti Tolvanen Peter Lund 《Solar Energy Materials & Solar Cells》2006,90(7-8):872-886
Electrochemical impedance spectroscopy was used to determine the effective charge transfer resistances of porous dye-sensitized solar cell counter electrodes prepared by low-temperature spray deposition and compression of conductive carbon and platinized Sb-doped SnO2 powders on indium tin oxide-coated plastic substrates. The charge transfer resistances were 0.5–2 and 8–13 Ω cm2, respectively, when using 3-methoxypropionitrile as the electrolyte solvent. The manufacturing method used lends itself to produce mechanically stable and even-quality electrodes in an easy and fast manner. 相似文献
75.
The formation of a low Cr-volatility and electrically conductive oxide outer layer atop an inner chromia layer via thermal oxidation is highly desirable for preventing chromium evaporation from solid oxide fuel cell (SOFC) metallic interconnects at the SOFC operation temperatures. In this paper, a number of ferritic Fe–22Cr alloys with different levels of Mn and Ti as well as a Ni-based alloy Haynes 242 were cyclically oxidized in air at 800 °C for twenty 100-h cycles. No oxide scale spallation was observed during thermal cycling for any of these alloys. A mixed Mn2O3/TiO2 surface layer and/or a (Mn, Cr)3O4 spinel outer layer atop a Cr2O3 inner layer was formed for the Fe–22Cr series alloys, while an NiO outer layer with a Cr2O3 inner layer was developed for Haynes 242 after cyclic oxidation. For the Fe–22Cr series alloys, the effects of Mn and Ti contents as well as alloy purity on the oxidation resistance and scale area specific resistance were evaluated. The performance of the ferritic alloys was compared with that of Haynes 242. The mismatch in thermal expansion coefficient between the different layers in the oxide scale was identified as a potential concern for these otherwise promising alloys. 相似文献
76.
In order to study the influence of cerium ion implantation on the aqueous corrosion behavior of zircaloy-4, specimens were implanted by cerium ions with a fluence range from 1×1016 to 1×1017 ions/cm2 at maximum 150°C, using MEVVA source at an extracted voltage of 40 kV. The valence and elements penetration distribution of the surface layer were analyzed by X-ray photoelectron spectroscopy (XPS) and auger electron spectroscopy (AES) respectively. Glancing angle X-ray diffraction (GAXRD) was employed to examine the phase transformation due to the cerium ion implantation in the oxide films. Three-sweep potentiodynamic polarization measurement was employed to value the aqueous corrosion resistance of zircaloy-4 in a 1 N H2SO4 solution. It was found that a significant improvement in the aqueous corrosion behavior of zircaloy-4 implanted with cerium ions compared with that of the as-received zircaloy-4. The improvement effect will declined with raising the implantation fluence. The bigger is the fluence, the less is the improvement. Finally, the mechanism of the corrosion behavior of the cerium-implanted zircaloy-4 is discussed. 相似文献
77.
目前在加筋边坡的极限平衡稳定分析中,认为加筋中产生的预应力能约束土体的运动或者能使抵抗土体运动的阻力增加,而对于加筋的切向阻力作用却没有考虑。主要讨论了在加筋土坡稳定分析时,加筋的切向阻力在加筋工程中起到的作用。认为在加筋边坡的极限平衡稳定分析中,也应考虑加筋的切向阻力作用;提出了计算公式,编制了相应的程序,给出了算例。 相似文献
78.
高硬度耐磨电弧喷涂管状丝材的研究 总被引:2,自引:0,他引:2
利用自熔性合金与非晶态材料的特点,研制了Fe—B系管状丝材作为电弧喷涂材料,其形成的涂层具有良好的结合强度、低的孔隙率、高的硬度和耐磨损性能。 相似文献
79.
本文提出基于切削振动相关性识别刀具磨损状态的研究思想,建立了车削中刀杆双向横振动系统及其单输入双输出系统的数学模型。理论和实验均表明,刀杆双向横振动之加速度响应在固有基频处的相干函数与刀具磨损状态之间有很好的规律性,它反映了两者之间的本质机理,并提供了识别刀具磨损状态的新途径。 相似文献
80.
H. -C. Chiao H. -L. Lin X. -T. Li C. -X. Ding 《Journal of Thermal Spray Technology》1992,1(2):111-115
Diamond growth with rates up to 100 to 140 μm/hr was achieved using an oxygen-acetylene combustion spraying technique in an
atmospheric environment. Investigations on the processing indicated that the gas flow ratio, substrate position, substrate
temperature, temperature distribution, and substrate pretreatment were the most important factors affecting the growth of
diamond crystals. Evaluation by means of X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and electron
probe microanalysis showed that the synthesized diamond was nearly perfect in morphology, structure, and purity. 相似文献