全文获取类型
收费全文 | 6413篇 |
免费 | 111篇 |
国内免费 | 159篇 |
专业分类
电工技术 | 87篇 |
综合类 | 111篇 |
化学工业 | 1207篇 |
金属工艺 | 1114篇 |
机械仪表 | 515篇 |
建筑科学 | 187篇 |
矿业工程 | 207篇 |
能源动力 | 1029篇 |
轻工业 | 190篇 |
水利工程 | 17篇 |
石油天然气 | 69篇 |
武器工业 | 24篇 |
无线电 | 322篇 |
一般工业技术 | 1168篇 |
冶金工业 | 223篇 |
原子能技术 | 80篇 |
自动化技术 | 133篇 |
出版年
2024年 | 4篇 |
2023年 | 83篇 |
2022年 | 170篇 |
2021年 | 205篇 |
2020年 | 193篇 |
2019年 | 164篇 |
2018年 | 142篇 |
2017年 | 156篇 |
2016年 | 108篇 |
2015年 | 126篇 |
2014年 | 299篇 |
2013年 | 387篇 |
2012年 | 305篇 |
2011年 | 507篇 |
2010年 | 336篇 |
2009年 | 413篇 |
2008年 | 401篇 |
2007年 | 357篇 |
2006年 | 321篇 |
2005年 | 266篇 |
2004年 | 226篇 |
2003年 | 246篇 |
2002年 | 165篇 |
2001年 | 149篇 |
2000年 | 151篇 |
1999年 | 153篇 |
1998年 | 125篇 |
1997年 | 84篇 |
1996年 | 118篇 |
1995年 | 79篇 |
1994年 | 51篇 |
1993年 | 51篇 |
1992年 | 27篇 |
1991年 | 30篇 |
1990年 | 18篇 |
1989年 | 27篇 |
1988年 | 8篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 9篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1977年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有6683条查询结果,搜索用时 15 毫秒
991.
Satya Sekhar Bhogilla Hiroshi Ito Takehiko Segawa Atsushi Kato Akihiro Nakano 《International Journal of Hydrogen Energy》2017,42(19):13827-13838
The renewable energy source like wind energy generates electric power with intermittent nature. Hydrogen energy system can help to solve the fluctuation problem of the wind power. Totalized Hydrogen Energy Utilization System (THEUS) consists of a Unitized Reversible Fuel Cell (URFC), a hydrogen storage tank, and other auxiliary components. Wind power is inherently variable; the URFC will be subjected to a dynamic input power profile in water electrolyzer mode operation. This paper describes the THEUS operation and performance at different variations in intermittent wind power. The performance of the THEUS was evaluated in water electrolyzer and fuel cell mode operation. The stack efficiency, system efficiency, and system efficiency including heat output from the URFC were presented at each operation. The total efficiency of the URFC and THEUS were also investigated. The maximum total efficiency of the URFC and THEUS were 53% and 66%, respectively. 相似文献
992.
M. Stange E. Stefan C. Denonville Y. Larring P.M. Rørvik R. Haugsrud 《International Journal of Hydrogen Energy》2017,42(19):13454-13462
Metal supports for planar MS-PCEC were manufactured using tape-casting of low-cost ferritic stainless steel. A coating protecting the metal support against oxidation was applied by vacuum infiltration and a buffer layer of La0.5Sr0.5Ti0.75Ni0.25O3–δ (LSTN) was further deposited to smoothen the surface. The BaZr0.85Y0.15O3–δ–NiO (BZY15–NiO) cathode and the BaZr0.85Y0.15O3–δ (BZY15) electrolyte were applied by pulsed laser deposition (PLD) at elevated substrate temperatures (at 700 °C and 600 °C, respectively). The main challenges are related to the restrictions in sintering temperature and atmosphere induced by the metal support, as well as strict demands on the roughness of substrates used for PLD. Reduction treatment of the half cells confirmed that NiO in the BZY15–NiO layer was reduced to Ni, resulting in increased porosity of the BZY15–Ni cathode, while keeping the columnar and dense microstructure of the BZY15 electrolyte. Initial electrochemical testing with a Pt anode showed a total resistance of 40 Ω·cm2 at 600 °C. Through this work important advances in using metal supports and thin films in planar PCEC assemblies have been made. 相似文献
993.
Georgios Karagiorgis Chris N. Christodoulou Henrik von Storch Georgios Tzamalis Konstantinos Deligiannis Demetrios Hadjipetrou Marios Odysseos Martin Roeb Christian Sattler 《International Journal of Hydrogen Energy》2017,42(17):12364-12374
Metal Hydride Compressors (MHC) is a promising technology for thermal compression of hydrogen. Besides the absence of a necessity for significant mechanical or electrical energy input, this type of compressor has the advantage that no moving parts are involved. A brief review on the reported experimental set ups of metal hydride compressors is carried out and compared to the metal hydride compressor developed and constructed by HYSTORE Technologies Ltd in Cyprus. The compressor built by HYSTORE consists of 6 stages using AB2 and AB5 – type metal hydride alloys. The MHC is operated between 10 C and 80 °C, which is a temperature range that can be supplied by solar thermal collectors. Furthermore, the experimental results showed, that even lower temperatures of 17 C are sufficient thus reducing the demand for cooling capacity. During the operation, the compressor achieved stable compression of hydrogen from 7 bar more than 220 bar. The specific productivity of the compressor achieved values up to 67.2 lH2 kg?1 h?1. 相似文献
994.
Huijuan Han Shujun Chao Xiaoli Yang Xiaobing Wang Kui Wang Zhengyu Bai Lin Yang 《International Journal of Hydrogen Energy》2017,42(25):16149-16156
Recently, to improve the catalytic activity of oxygen evolution reaction (OER) electrocatalysts, some design strategies, such as the decrease of the catalyst particle size, the formation of the porous structure and the couple of carbon-based materials, are receiving increased attention in energy-related systems. Herein, based on metal organic framework (MOF), we develop an effective strategy to synthesize Ni nanoparticles embedded in N doped carbon nanotubes (Ni NPs@N-CNTs) catalyst. In consequence, the Ni NPs@N-CNTs integrates the advantageous features of NPs and N-CNTs towards OER, such as more catalytic sites, large surface area, pore-rich structure and good electrical conductivity. Benefiting from the favorable features, the Ni NPs@N-CNTs exhibits a better OER performance than commercial RuO2 in alkaline medium, which includes a lower onset potential (1.49 V), a smaller Tafel slope (106 mV dec?1). The present work opens a new window for the construction of the coupling materials between NPs and carbon-based materials to increase the electrocatalytic activity of transition metal catalysts. 相似文献
995.
Prangtip Kaewpengkrow Duangduen Atong Viboon Sricharoenchaikul 《International Journal of Hydrogen Energy》2017,42(31):19629-19640
Rapid catalytic thermal conversion of Physic nut (Jatropha curcas) residues for upgrading the released vapors was performed using analytical pyrolyzer-gas chromatography/mass spectrometry at 873 K. Conditioning of the evolved vapor product is required since the main vapor products formed without catalysts typically contained around 60% fatty acids, while the total hydrocarbon yields were only 12%. Catalysts tested were alumina (Al2O3) alone and modified by 5 wt% impregnation with various transition metal salts and then calcined to metal oxides. A significant decrease in the proportion of oxygenated compounds (including acids) from 73% without a catalyst to less than 10% with, and an increased conversion to hydrocarbons of more than 70% was obtained with the metal/Al2O3 catalysts at a Jatropha:catalyst (J:C) ratio of 1:10. The product selectivity was greatly increased as the J:C ratio was increased from 1:1 to 1:10. The total hydrocarbon selectivity of the metal/Al2O3 catalysts was increased in the order of Pd > Ni > Ce > Ru > La > none > Co > Mo, with the highest proportion of total hydrocarbons obtained being 75%. In addition, only a low yield (<2%) of polycyclic aromatic hydrocarbons was obtained from the conversion of Jatropha curcas residues. However, these catalysts adversely promoted N-containing compounds, suggesting that a further denitrogenation process is necessary. Nevertheless, the overall performance of these transition metal/Al2O3 catalysts is acceptable and they can be considered as good candidates for bio-oil upgrading. 相似文献
996.
997.
本文对两相同步原位自生型 Ni3Al-Cr7C3 金属陶瓷涂层中陶瓷相的第二相强化作用开展研究, 将复合材料
经典 Hall-Petch 关系适用范围扩展至金属陶瓷涂层材料, 建立了金属陶瓷样品的硬度随强化相尺寸变化的模型,
并采用粘结相平均自由程和相界面共格的结构取向关系对 Hall-Petch 关系公式进行校准。 研究发现, Ni3Al-Cr7C3
涂层内部的织网结构受粘结相 (Ni3Al) 平均自由程和相界面共格取向关系的共同影响, 符合弥散强化与相界面共
格效应协同作用的强化机理, 接近于第二相沉淀强化的作用。 相似文献
998.
汽车发动机曲轴断裂分析 总被引:3,自引:2,他引:1
某6缸发动机曲轴在运行8910km时,第六曲拐颈断裂。对断裂曲轴进行了断口观察、化学成分复验、基体硬度和显微组织检验。结果表明,曲轴的拐颈断裂为扭转疲劳断裂,断裂疲劳源位于油道孔与倒圆角曲面交接处,此处的切削加工刀痕及金属损伤形成应力集中且处于最大主应力面上,因而引发扭转疲劳断裂。 相似文献
999.
《International Journal of Hydrogen Energy》2020,45(21):12216-12224
In the production and storage processes of metal hydride material of TiH2, there are at least three kinds of explosion hazards, for example, TiH2 dust explosion, H2 explosion and hybrid H2/TiH2 dust explosion. In this study, combustion behaviors of TiH2 dust cloud under isobaric and isochoric conditions were studied using a visual dust combustion facility and a standard 20-L spherical explosion vessel bomb, respectively, and Ti dust and hybrid H2/Ti dust were used as the reference materials. Experimental results showed that at equal dust concentrations, the flame propagation speed Sf, burning velocity SL, maximum pressure rise Pex and maximum rate of pressure rise (dP/dt)ex of TiH2 dust were all higher than those of Ti dust, while much smaller than those of hybrid H2/Ti dust except the maximum pressure rise Pex. The hydrogen state and content were the primary factors for the combustion differences of dust explosions. The values of explosion index Kst showed that the explosion risks of these samples increased as follows: Ti ˂ TiH2 ˂ hybrid H2/Ti dust. 相似文献
1000.
CarolineK. Wilharm 《Propellants, Explosives, Pyrotechnics》2003,28(6):296-300
A model for the combustion of pyrophoric metal foils has been developed. The diffusive mass transport, heat transport, and chemical reactions of porous iron foils have been described. The temperature and radiated energy of these materials has been predicted as a function of the physical characteristics of the material (porosity, pore size, specific surface area) for different atmospheric conditions (temperatures and oxygen concentrations varied with altitude and wind velocity). 相似文献