全文获取类型
收费全文 | 741篇 |
免费 | 103篇 |
国内免费 | 26篇 |
专业分类
电工技术 | 12篇 |
综合类 | 23篇 |
化学工业 | 489篇 |
金属工艺 | 80篇 |
机械仪表 | 10篇 |
矿业工程 | 2篇 |
能源动力 | 35篇 |
轻工业 | 3篇 |
石油天然气 | 37篇 |
武器工业 | 2篇 |
无线电 | 26篇 |
一般工业技术 | 71篇 |
冶金工业 | 42篇 |
原子能技术 | 34篇 |
自动化技术 | 4篇 |
出版年
2023年 | 19篇 |
2022年 | 6篇 |
2021年 | 15篇 |
2020年 | 24篇 |
2019年 | 19篇 |
2018年 | 25篇 |
2017年 | 22篇 |
2016年 | 41篇 |
2015年 | 35篇 |
2014年 | 42篇 |
2013年 | 69篇 |
2012年 | 44篇 |
2011年 | 58篇 |
2010年 | 31篇 |
2009年 | 41篇 |
2008年 | 42篇 |
2007年 | 56篇 |
2006年 | 45篇 |
2005年 | 43篇 |
2004年 | 32篇 |
2003年 | 21篇 |
2002年 | 18篇 |
2001年 | 10篇 |
2000年 | 24篇 |
1999年 | 8篇 |
1998年 | 9篇 |
1997年 | 7篇 |
1996年 | 8篇 |
1995年 | 7篇 |
1994年 | 17篇 |
1993年 | 5篇 |
1992年 | 7篇 |
1991年 | 6篇 |
1990年 | 5篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有870条查询结果,搜索用时 15 毫秒
21.
《Journal of Nuclear Science and Technology》2013,50(8):633-634
Hydrogen gas evolution from water dispersing nanoparticles induced by 60Co γ-ray irradiation was studied. Nanoparticles of TiO2 and Al2O3 with average sizes of 7–33 nm supplied from several suppliers were examined. It was indicated that reactions enhancing the hydrogen evolution proceed on particle's surface. It was implied that the yield depends on size of agglomerated particle regardless of their primary particle size and chemical species. Reactions that enhance the hydrogen yields were discussed, and radiolysis process was concluded dominant in the total enhancement mechanism. 相似文献
22.
Combined generation and separation of hydrogen in an electrochemical water gas shift reactor (EWGSR)
Hydrogen rich gas, originating from fossil fuel reforming processes or biomass gasification, contains a significant amount of CO. Typically, the yield of H2 is increased with subsequent water gas shift units, converting CO to CO2 and additional H2. This study describes a new reactor concept enabling the water gas shift reaction and the separation of the generated hydrogen in one process step by using electrical energy. This electrochemical water gas shift reactor applies a H3PO4-doped Poly(2,5-benzimidazole) membrane as electrolyte and carbon supported Pt or PtRu as anode catalyst. The reactor operation was investigated at 130 °C and 150 °C with a H2 free anode feed stream of humidified CO and N2. The experimental results show the feasibility of the reactor concept, as H2 was generated at the cathode according to Faradays Law. Anodic PtRu led to lower power demands than Pt. The operation at the two temperatures showed that 130 °C results in a lower electrical power demand while generating an equal amount of H2. The feasibility of the reactor was assessed using exergy efficiency analysis. 相似文献
23.
24.
We report on the preparation and application of novel heterogeneous supported ruthenium catalysts. The catalysts are active in the synthesis of formic acid from the hydrogenation of carbon dioxide and are characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray powder diffraction analysis and transmission electron microscopy. Abundant hydroxyl groups, which interact with the ruthenium components, play an important role in the catalytic reactions. Highly dispersed ruthenium hydroxide species enhance the hydrogenation of CO2, while crystalline RuO2 species, which are formed from the relatively high ruthenium content or the pH of the solution during preparation of the catalyst, restrict the production of formic acid. Optimal activity of ruthenium hydroxide as a catalyst for the hydrogenation of CO2 to formic acid is achieved over a γ-Al2O3 supported 2.0 wt% ruthenium catalyst, which is prepared in a solution of pH 12.8 with NH3·H2O as a titration solvent. A possible hydrogenation mechanism for the hydroxide ruthenium catalyst is proposed. 相似文献
25.
采用沉积沉淀法制备了以活性炭(C)为载体的Ru催化剂,研究了Ru/C催化剂在苯选择加氢反应中的催化性能,并对Ru/C催化剂进行了表征.结果表明:Ru在催化剂中的分散性好,Ru/C催化剂具有较高的催化活性;适宜的反应条件为温度140℃,压力5.0 MPa,催化剂中Ru质量分数为4.0%,苯的转化率达40%以上,产物环己烯... 相似文献
26.
27.
28.
Pt-Ru/C catalyst (12 wt%) was prepared by the incipient wetness impregnation method followed by a redox heat-treatment. Transmission electron microscopy (TEM) results revealed uniformly distributed metallic crystallites of Pt-Ru alloy nanoparticles (dPtRu = 2.1 ± 1.0 nm). The effect of redox treatments of the impregnated catalysts on methanol oxidation reaction (MOR) was examined by cyclic voltammetry (CV). The MOR activity of the PtRu/C was significantly improved after each oxidation step of the redox treatment cycles. The enhanced catalytic activity was found to be quite stable in chronoamperometry (CA) measurements. CV, X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) results strongly suggested that the improved catalytic activity was due to the formation of a stable c-RuOx (x = 2-3) domain during the oxidation treatments. A bifunctional based mechanism was proposed for the MOR on the oxidized PtRu/C catalysts. Formation of Ru-OH species on the surface of c-RuOx domains was suggested as stale sites for the oxidation of carbon monoxide adsorbed on the Pt catalytic sites. 相似文献
29.
In this work a facile synthesis for a high-performance PtRuBi/C catalyst was presented through a simple mixture of commercial PtRu/C and Bi(NO3)3. Most of the Bimodified the PtRu particle surface via irreversible adsorption and deposition processes. X-ray photoelectron spectroscopy analysis indicated that Bi2O3 was the main form in the catalyst and that there exists an interaction between Bi2O3 and Pt. The current density of PtRuBi/C (1:1:0.2 for Pt:Ru:Bi) in the cyclic voltammograms for methanol or ethanol oxidation is over 2.6 times higher than that of PtRu/C. The anti-poisoning ability of this catalyst was also greatly improved. The Bi-containing catalyst had abundant oxygenated species and facilitated removal of poisonous intermediate species. 相似文献
30.
We synthesized new electropolymerizable [Ru(bpy)nLm](PF6)2 (L = 4,4 bis(3-pyrrol-1-ylpropyloxy)bipyridyl) derivatives. The introduction of electron donating ether groups in the bipyridine ligand induced a negative shift of the Ru(III)/(II) redox couple. The electrochemical behavior of complex Ru1 (n = 2, m = 1) and complex Ru2 (n = 0, m = 3) were compared using platinum and Multi-Walled Carbon Nanotube (MWCNT) electrode. Higher polymerization yields and surface concentrations were obtained at MWCNT electrodes. Furthermore, MWCNT electrodes increase polymer permeability and decrease the charge trapping phenomenon involved in the oxidation and reduction of the polypyrrolic skeleton of the Ru(II) functionalized polymers. 相似文献