全文获取类型
收费全文 | 2142篇 |
免费 | 115篇 |
国内免费 | 91篇 |
专业分类
电工技术 | 66篇 |
综合类 | 47篇 |
化学工业 | 978篇 |
金属工艺 | 143篇 |
机械仪表 | 28篇 |
建筑科学 | 5篇 |
矿业工程 | 9篇 |
能源动力 | 488篇 |
轻工业 | 13篇 |
石油天然气 | 90篇 |
无线电 | 129篇 |
一般工业技术 | 213篇 |
冶金工业 | 48篇 |
原子能技术 | 24篇 |
自动化技术 | 67篇 |
出版年
2024年 | 1篇 |
2023年 | 51篇 |
2022年 | 44篇 |
2021年 | 63篇 |
2020年 | 73篇 |
2019年 | 67篇 |
2018年 | 69篇 |
2017年 | 67篇 |
2016年 | 52篇 |
2015年 | 45篇 |
2014年 | 87篇 |
2013年 | 119篇 |
2012年 | 128篇 |
2011年 | 157篇 |
2010年 | 133篇 |
2009年 | 139篇 |
2008年 | 135篇 |
2007年 | 177篇 |
2006年 | 115篇 |
2005年 | 88篇 |
2004年 | 65篇 |
2003年 | 64篇 |
2002年 | 72篇 |
2001年 | 59篇 |
2000年 | 52篇 |
1999年 | 32篇 |
1998年 | 38篇 |
1997年 | 19篇 |
1996年 | 30篇 |
1995年 | 12篇 |
1994年 | 20篇 |
1993年 | 22篇 |
1992年 | 14篇 |
1991年 | 16篇 |
1990年 | 9篇 |
1989年 | 2篇 |
1988年 | 5篇 |
1986年 | 4篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有2348条查询结果,搜索用时 31 毫秒
91.
研究了硒、铜、银、砷作为共沉淀剂。富集分离地质样品中金、铂、钯的最佳条件。在3mol/L HCl介质中,以4mg硒和5mg铜、银、砷对金、铂、钯进行共沉淀富集,采用孔雀绿分光光度法测定金.DDO分光光度法测定铂、钯,回收率均在95%-102%之间。通过对含金矿样加入铂、钯标准样品的回收实验,结果令人满意。 相似文献
92.
The thermal behaviors of the deposits on supported noble metal catalysts for synthesizing 2, 3, 5-trimethylhydroquinone by
DSC were studied. The results show that the supported Pd catalysts have two exothermic peaks at around 312 °C and 435 °C in
the DSC thermograms, respectively, while the supported Pt catalysts have one exothermic peak at approximately 345 °C. Therefore,
it is supposed that the adsorptive states of deposits on supported Pt catalysts and supported Pd catalysts are different,
which may be one reason leading to the stability difference between supported Pt catalysts and supported Pd catalysts. 相似文献
93.
高效率多硫化钠/溴储能电池的研究 总被引:7,自引:2,他引:7
采用高温还原的方法制备了多硫化钠/溴储能电池负极用Ni/C催化剂,Ni/C、Pt/C分别是多硫化钠/溴储能电池负极和正极性能良好的电催化剂。系统地研究了Nafion膜的厚度、电催化剂含量、操作条件对电池充放电性能的影响。采用较厚的膜,电池性能稍微降低,但可减少阴离子的渗透。这种新型储能电池放电时功率密度达到0 7W/cm2(U=1 0V)。循环性能研究表明:采用较厚的膜,电池的充放电性能好,性能衰减很小,在100mA/cm2充放电,电压效率达到86 7%。 相似文献
94.
Hydrogenation of p‐Nitrophenol to p‐Aminophenol as a Test Reaction for the Catalytic Activity of Supported Pt Catalysts
下载免费PDF全文
![点击此处可从《化学工程与技术》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Michael Goepel Majd Al‐Naji Patrick With Gerald Wagner Oliver Oeckler Dirk Enke Roger Gläser 《化学工程与技术》2014,37(3):551-554
Hydrogenation of p‐nitrophenol (PNP) to p‐aminophenol (PAP) using NaBH4 as a reducing agent was studied as a test reaction for determining the catalytic activity of supported Pt catalysts. The initial reaction rate, which is accessible within less than 10 min via online UV‐vis spectroscopy at room temperature, ambient pressure, and in water as solvent, was applied as measure for catalytic activity. For three Pt catalysts supported on porous SiO2, porous glass, and Al2O3, respectively, significant differences in the catalytic activity by almost one order of magnitude were observed. However, especially in the case of very active catalysts, limitations of the reaction by internal or external mass transfer have to be considered. 相似文献
95.
Kaihua Su Xianyong Yao Sheng Sui Zhaoxu Wei Junliang Zhang Shangfeng Du 《International Journal of Hydrogen Energy》2014
The effects of ionomer contents were investigated in composite electrodes with in-situ grown single crystal Pt nanowires (Pt-NWs) for PEMFCs, including the amount in the carbon matrix and impregnated on the surface of the electrocatalyst layer. The electrocatalyst layer was prepared by growing Pt-NWs directly on the carbon matrix with a simple one-step wet chemical approach at room temperature. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), polarization curve tests, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) were employed to evaluate the ionomer effects. The experimental results showed that the ionomer in the carbon matrix had an influence on the ionic conductivity and aggregation and distribution of the Pt-NWs, and the ionomer impregnated on the surface of the electrocatalyst layer affected the mass transport and ionic conductivity. The performance of the MEA was improved by optimizing the ionomer contents. 相似文献
96.
《International Journal of Hydrogen Energy》2019,44(52):28123-28133
Using free and sustainable solar energy to produce hydrogen is the most promising strategy to resolve the environmental pollution and global energy crisis. The properties of sensitized matrix and co–catalyst, including the dispersibility, lattice structure and electrical performance, are usually two the decisive factors for photocatalytic hydrogen evolution. This paper reports a facile synthetic process of surface–clean monodisperse Pt(100) nanocubes supported on graphene surface using amide functional groups as induction sites. The prepared catalyst (AG/Pt(100)) not only incorporate plentiful amide functional groups that act as the dispersant and stabilizer into surface and edge of graphene, but also significantly dislodge the oxygen–containing functional groups, which hold strong promise for improving conductivity, carrier concentration and mobility of sensitized matrix. Simultaneously, the monodisperse Pt(100) nanocubes supported on graphene surface exposure more active sites. These results provide the necessary conditions for efficient catalysts. Without any pre–treatment, it exhibits high H2 generation activity (553.7 μmol for 2 h) and apparent quantum efficiency (AQE) (33.9% at 430 nm) under visible light irradiation when Eosin Y is used as photosensitizer. These superior production H2 activities can attribute to enhance the dispersion and conductivity of sensitized matrix, construct special geometry of Pt(100) nanocubes and prolong the lifetime of photogenerated electron. 相似文献
97.
Li‐Fang Wei Xian‐Jun Zheng Zhi‐Hong Zhang Yong‐Jie Wei Bing Xie Ming‐Bao Wei Xiao‐Li Sun 《国际能源研究杂志》2012,36(1):75-86
The propionic acid (HPr) is one of the main by‐products during fermentative H2 process. To efficiently convert HPr to H2 gas, photocatalytic H2 production from HPr solution with the use of Pt/TiO2 photocatalyst under ultraviolet light has been studied in this research. The Pt/TiO2 photocatalyst has been prepared by the sol–gel method and further characterized by X‐ray diffraction, TEM and XPS. Effects of Pt loading amount, HPr concentration, initial pH value on photocatalytic H2 production have been investigated in detail. From practical point of view, the H2 evolution from HPr solution under UV irradiation for prolonged time has been studied as well. The Langmuir model can be able to describe the relationship between HPr concentration with the maximum rate of H2 production. The apparent quantum efficiency and apparent energy conversion efficiency are found to 1.65 and 0.72%, respectively. To better understand the photocatalytic H2 process over Pt/TiO2, a possible mechanism for the degradation of HPr has been proposed as well. Based on our results, an efficient route for hydrogen production from renewable biomass can be established by coupling biological H2 production process with photocatalytic H2 production process. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
98.
《International Journal of Hydrogen Energy》2019,44(36):20336-20344
The interconnecred PtIr alloy nanowires were uniformly deposited on carbon cloth via One-step wet chemistry method, which diameter is averaged to be 5 nm with a length of 50–200 nm. The carbon cloth supported PtIr nanowire assembly (PtIr NA/CC) shows a larger electrochemical active surface area (ECSA) due to its 3D nanostructure and a high CO-resistance as a result from the synergistic effect of PtIr alloy. The PtIr NA/CC exhibits an extremely high mass activity and a reliable long-term stability toward methanol oxidation reaction (MOR). The superior catalytic performance on MOR can match and even surpass those best Pt-based nanowires reported recently in the literature. 相似文献
99.
《International Journal of Hydrogen Energy》2021,46(61):31202-31215
Direct methanol fuel cells (DMFCs) had been attracted considerable attention for its advantages of high energy density, simplified systems and readily transportation and storage of methanol. However, the notoriously sluggish kinetics of methanol oxidation reaction (MOR) of the anode reaction, had greatly affected the commercialization of DMFCs. On one hand, Pt based catalyst are still the most effective MOR catalysts, while the high cost caused by the high loadings of electrocatalyst to compensate the low MOR activity impedes the wide accessible of DMFCs. In addition, the occurrence of catalyst poisoning owing to the strong interaction between Pt and carbon monoxide (CO) generated during the MOR processing, further leading to the fast decay in the performance and stability of MOR electrocatalysts. Two-dimensional (2D) Pt based nanostructures is regarded to be one promising and effective class of MOR electrocatalysts, and attracted much attention due to the high electron mobility, highly exposed active sites, and extraordinary thermal conduction. In this review, the mechanism of MOR was firstly introduced, and then the synthesis conditions, structure characteristics and methanol oxidation performances both in acidic and alkaline dielectric of 2D Pt based nanocatalysts were introduced. Subsequently, we briefly analyzed the structural characteristics of 2D Pt based nanocatalysts and their advantages, including the low platinum loadings, high specific surface area and majority of atomic active sites exposed. Finally, the opportunities and challenges for designing of advanced 2D Pt based nanocatalysts was proposed and discussed. 相似文献
100.
The Pt oxide thin film and Pt thin film were prepared by reactive sputtering and the electrocatalytic activity of the ethanol oxidation reaction was investigated in a KOH solution for developing the alkaline direct ethanol fuel cells. After electrochemical reduction by passing a cathodic electric charge, the Pt oxide thin film showed 29 times larger ethanol oxidation current than the Pt thin film. This superior activity was caused by an increase in the electrochemical active surface area and the existence of residual oxygen, which was confirmed by cyclic voltammetry and XPS measurement. Due to the contribution of the residual oxygen, the rate-determining step of the ethanol oxidation reaction might change, because the Tafel slope of the Pt oxide thin film during the ethanol oxidation reaction was changed by electrochemical reduction. Despite the total Pt amount in the Pt oxide thin film being smaller than that in the Pt thin film, the Pt oxide thin film showed excellent ethanol oxidation activity. Therefore, the Pt oxide treated by electrochemical reduction may be a promising anode catalyst for the direct ethanol fuel cells. 相似文献