全文获取类型
收费全文 | 264篇 |
免费 | 21篇 |
国内免费 | 21篇 |
专业分类
电工技术 | 5篇 |
综合类 | 23篇 |
化学工业 | 85篇 |
金属工艺 | 60篇 |
机械仪表 | 10篇 |
矿业工程 | 10篇 |
能源动力 | 7篇 |
轻工业 | 4篇 |
石油天然气 | 4篇 |
武器工业 | 2篇 |
无线电 | 2篇 |
一般工业技术 | 68篇 |
冶金工业 | 22篇 |
自动化技术 | 4篇 |
出版年
2023年 | 4篇 |
2022年 | 5篇 |
2021年 | 7篇 |
2020年 | 10篇 |
2019年 | 9篇 |
2018年 | 6篇 |
2017年 | 6篇 |
2016年 | 3篇 |
2015年 | 5篇 |
2014年 | 10篇 |
2013年 | 11篇 |
2012年 | 11篇 |
2011年 | 18篇 |
2010年 | 19篇 |
2009年 | 14篇 |
2008年 | 12篇 |
2007年 | 16篇 |
2006年 | 14篇 |
2005年 | 15篇 |
2004年 | 19篇 |
2003年 | 15篇 |
2002年 | 8篇 |
2001年 | 8篇 |
2000年 | 8篇 |
1999年 | 8篇 |
1998年 | 13篇 |
1997年 | 8篇 |
1996年 | 2篇 |
1995年 | 5篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 1篇 |
排序方式: 共有306条查询结果,搜索用时 31 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(47):20494-20506
Proton exchange membrane fuel cells (PEMFCs) durability has been severely hindered by carbon support poor stability in the cathodic Pt-based catalyst. Herein, a high-surface-area nitrogen-doped graphitic nanocarbon (N-G-CA) with mesopores is developed as Pt support to address PEMFCs durability challenge. Resorcinol-formaldehyde aerogel pyrolyzed carbon aerogel is selected as N-G-CA raw material. Nitrogen atoms are introduced into carbon aerogel via NH3 heat treatment. Then, nitrogen-doped carbon aerogel is transferred into N-G-CA via heating together with transition-metal salts (one of FeCl3, FeCl2, CoCl2, or MnCl2, etc.) at 1200 °C. As ORR catalyst, Pt/N-G-CA half-wave potential only lost 10 mV, after 30, 000 cycles accelerated aging test in the rotating-desk-electrode. Only 12 mV voltage loss at 1.5 A/cm2 is observed, after 5, 000 cycles for membrane electrode. Pt/N-G-CA exhibits superior durability and activity than commercial Pt/C. High durability of Pt/N-G-CA is due to N-G-CA high graphitization extent, as well as the interactions between doping nitrogen and Pt. N-G-CA is promising as stable support for durable Pt-based catalysts in PEMFCs, thanks to enhanced carbon corrosion resistance, uniformly dispersed Pt, and strong support-metals interaction. 相似文献
2.
《Ceramics International》2020,46(5):5733-5744
To improve the self-adaptability of MoS2 coating in different environments, the coatings were doped with functional C and Ti by unbalanced magnetron sputtering system. The clear superlattice structure with minimal modulation period was investigated by High Resolution Transmission Electron Microscope (HRTEM). The co-doped coatings have better mechanical properties due to the special structure and the formation of C–Mo, Ti–S and Ti–O bonds, and better lubrication performance in both high humidity and vacuum than those of the single-doped ones. The doped Ti not only facilitates the formation of the MoS2 (002) basal plane, but also improves the oxidation resistance of the composite film. The degree of friction-induced graphitization on the wear tracks and the quality of transfer films on the wear scars are key factors affecting the lubrication performance of the composite film. In the high-humidity environment, the reasonable doping elements can promote the formation the high-quality transfer film by interacting with H2O water molecules, which will benefit the lubrication of the coating better. Our findings deepen the understanding of MoS2 composite coating and provide a new solution for improving the self-adaptability of the coating. 相似文献
3.
4.
5.
石墨化率不同的自焙炭块的热膨胀 总被引:1,自引:0,他引:1
采用精密垂直拉杆膨胀仪在14~1000℃范围内测量了具有不同石墨化率的自焙炭块的相对热伸长量,并由此获得了热线膨胀系数α。结果表明:石墨化率一定时,α值在较低温度下随温度升高而增加,在较高温度下,α值随温度变化不明显;恒温时,石墨化率越高,α值越低。讨论了单位热应力下的弹性模量概念 相似文献
6.
将高温煤沥青和浸溃荆沥青在92MPa下炭化,在2500℃下对所得沥青炭进行石墨化处理;测试了所得沥青炭的体积密度、开孔率、比表面积(SBET);利用扫描电子显微镜(SEM)观察了所得沥青炭的显微结构;利用X射线衍射方法(XRD)检测了所得沥青炭石墨化处理后的石墨化度;测试了所得沥青炭的氧化性能;测试了沥青炭试样的比热容、导热系数、热扩散率和线膨胀系数。结果表明:在92MPa下,两种沥青炭有着相近的密度和开孔率;浸渍剂沥青炭的SBEt高于高温煤沥青炭;浸渍荆沥青炭为流线型结构,高温煤沥青炭为镶嵌型和域型并存的结构;流线型结构沥青炭石墨化度较高;高温煤沥青炭的抗氧化性能要好于浸溃荆沥青炭;随着沥青炭石墨化程度的增大,比热客、导热系数、热扩散率都增大,而线膨胀系数减小。 相似文献
7.
Evolution with heat treatment of crystallinity in carbons 总被引:1,自引:0,他引:1
F. G. Emmerich 《Carbon》1995,33(12)
The variation with heat treatment of the dimensions La and Lc of the graphite-like crystallites of graphitizable and non-graphitizable carbons is studied. The increases of La and Lc with heat treatment temperature (HTT) owing to three processes (crystallite growth in-plane, coalescence of crystallites along the c-axis and coalescence of crystallites along the a-axis) are functionally separated. The evolution with HTT of the number of crystallites (Ncr), the mean volume of the crystallites (vcr) and the total volume occupied by the crystallites (Vcr) are determined in terms of the changes of La, Lc and d002. Since among other characteristics the crystallites form the electrical and thermal conducting phase of the carbon, Ncr, vcr and Vcr are important parameters in many physical properties of these materials. The developed expressions were applied to a non-graphitizable and to a graphitizable carbon. 相似文献
8.
9.
10.
To investigate the effects of introducing the iron compound on the carbonization behavior polyacrylonitile (PAN)-based electrospun nanofibers were carbonized with or without iron(III) acetylacetonate (AAI) over the temperature range of 900–1500 °C in nitrogen atmosphere. The morphological characteristics of the carbon nanofibers were investigated using X-ray diffractometer (XRD), Raman spectroscopy, field emission scanning electron microscopy, and transmission electron microscopy. The electrical conductivity of the carbon nanofiber web was measured by four-point probe method. The iron catalyst had a profound effect on the crystal structure of the carbonized nanofiber. In the presence of AAI the nanofibers carbonized at 1300 °C developed graphite structure, which could be obtained at the temperature higher than 2000 °C in the absence of the catalyst. The in-plane size of the graphite crystals (La) was measured to be about 6.5 nm by Raman spectroscopy and the (0 0 2) spacing by XRD was 0.341 nm. 相似文献