全文获取类型
收费全文 | 560篇 |
免费 | 39篇 |
国内免费 | 29篇 |
专业分类
电工技术 | 7篇 |
综合类 | 31篇 |
化学工业 | 250篇 |
金属工艺 | 47篇 |
机械仪表 | 5篇 |
建筑科学 | 5篇 |
矿业工程 | 2篇 |
能源动力 | 120篇 |
轻工业 | 9篇 |
石油天然气 | 15篇 |
无线电 | 32篇 |
一般工业技术 | 69篇 |
冶金工业 | 10篇 |
原子能技术 | 21篇 |
自动化技术 | 5篇 |
出版年
2024年 | 4篇 |
2023年 | 27篇 |
2022年 | 21篇 |
2021年 | 26篇 |
2020年 | 34篇 |
2019年 | 12篇 |
2018年 | 23篇 |
2017年 | 18篇 |
2016年 | 11篇 |
2015年 | 9篇 |
2014年 | 20篇 |
2013年 | 36篇 |
2012年 | 36篇 |
2011年 | 50篇 |
2010年 | 26篇 |
2009年 | 31篇 |
2008年 | 27篇 |
2007年 | 38篇 |
2006年 | 26篇 |
2005年 | 23篇 |
2004年 | 16篇 |
2003年 | 15篇 |
2002年 | 20篇 |
2001年 | 15篇 |
2000年 | 5篇 |
1999年 | 10篇 |
1998年 | 9篇 |
1997年 | 4篇 |
1996年 | 8篇 |
1995年 | 3篇 |
1994年 | 7篇 |
1993年 | 3篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1984年 | 2篇 |
排序方式: 共有628条查询结果,搜索用时 0 毫秒
101.
The Ru-free and Ru-containing single crystal superalloys were cast in the directionally solidified furnace, while other alloying element contents were basically kept unchanged. The effects of Ru on the solidification characteristic and microstructures of single crystal superalloy were investigated with differential scanning calorimetry, electron probe micro analyzer, energy-dispersive X-ray spectroscope, scanning electron microscope and transmission electron microscope. The results show that the liquidus temperature of the single crystal superalloy decreases with Ru addition. The primary dendrite arm spacing and volume fraction of γ/γ′ eutectic both decrease with Ru addition. The sizes of γ′ phase of dendritic core and interdendritic region have no obvious change with Ru addition. Ru tends to segregate slightly in the dendritic core. The extent of elements segregation decreases with the Ru addition. Ru tends to partition preferentially into the γ matrix. The addition of Ru decreases the partition ratio (the ratio of the γ phases composition over the γ′ phases composition) of elements Re, W and Mo. 相似文献
102.
103.
M. Aulice Scibioh In-Hwan Oh Tae-Hoon Lim Seong-Ahn Hong Heung Yong Ha 《Applied catalysis. B, Environmental》2008,77(3-4):373-385
High-performance fuel cell electrodes require architectures that offer appropriate electrochemical and nanoscopic catalytic reaction zones. In this direction, ionomer (perfluoro sulfonic acid)-coated carbon supports were prepared by adopting a simple and cheap synthetic strategy to offer both electronic and protonic contacts to the catalyst particulates. Pt–Ru bimetallic anode catalysts were prepared on these modified carbon supports by a colloidal method. The role of surface area of carbon supports and the influence of ionomer content in them towards the catalytic activities of Pt–Ru catalysts has been probed by using three kinds of carbon black powders with different physical properties. Their electrocatalytic efficiencies toward methanol oxidation were scrutinized via half-cell measurements in cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. Catalysts particulates dispersed on carbon supports coated with ionomer exhibited better performance than those on the plain carbon supports, owing to the reduced micropores and increased interfacial area between catalyst particles and ionomer. Plain and modified carbon (MC) supports were characterized by using FTIR, BET-PSD and TEM techniques. Physico-chemical characterizations of supported catalyst systems were done by using XRD and TEM. 相似文献
104.
The hydrodechlorination (HDC) of chlorobenzene (abbreviated as CLB) and seven types of para-substituted chlorobenzenes (para-amino, -methoxy, -methyl, -chloro, -trifluoromethyl, -acetyl and -cyano: abbreviated as CLAN, CLAS, CLTN, DCLB, CLTF, CLAP and CLBN, respectively) were performed over 5%-ruthenium/carbon (Ru/C) under a hydrogen pressure of 0.5–1.5 MPa at 523 K.In the HDC of these model compounds, except for CLAP and CLBN, reductive cleavage between the carbon and chlorine atoms took place and dechlorinated compounds were produced preferentially. In the reaction of CLAP and CLBN, on the other hand, hydrogenation and/or hydrogenolysis of the substituent coincided with the HDC and a wide variety of products was observed accompanying the HDC product.For the chlorobenzenes of the simple HDC, the HDC reaction rate constants decreased in the orders of CLAN CLB ≈ CLTN ≈ CLAS and CLB > DCLB CLTF, respectively.In the reaction of the chlorobenzenes of the electron-donating substituent, the reaction constant (ln k/k0) has no relevance to the Hammett substituent constant (). In the case of the chlorobenzenes possessing the electron-withdrawing substituent, on the other hand, it was indicated that the electron-withdrawing substituent suppressed the HDC reactivity of chlorobenzenes, although no proportional relationship was observed between the reaction rate constant and the Hammett substituent constant.To explore the factors affecting the HDC reactivity, quantum calculation according to the DFT method (B3LYP/LANL2DZ) was applied to the “chlorobenzenes-Ru10” complex. As a result of the calculation, chlorobenzenes were adsorbed through a chlorine atom on the edge atom of the Ru10 cluster. The magnitude of the adsorption energy, moreover, decreased in the order of CLAN > CLAS ≈ CLB ≈ CLTN and CLB > DCLB > CLTF, respectively. These orders of adsorption energy are similar to that of the HDC reaction rate constant. It was concluded that adsorption energy is a useful parameter for the reactivity index of the HDC. 相似文献
105.
106.
引言 对14MeV中子诱发~(238)U裂变的质量分布已做了很多研究,这是因为氘-氚聚变反应(D T→n α)提供了一个极好的14MeV的单能中子源。但对其它单能中子诱发~(238)U裂变的质量分布研究得就不够充分,已报道的结果中有些彼此分歧较大。我们用放化法测量了D(d,n)~3He反应产生的5MeV中子诱发~(238)U裂变时几个核素的绝对产额。 相似文献
107.
Antonio Vita Giuseppe Cristiano Cristina Italiano Stefania Specchia Francesco Cipitì Vito Specchia 《International Journal of Hydrogen Energy》2014
The in situ deposition of 1.5 wt.% Ru/γ-Al2O3 catalytic layers on cordierite monoliths (400 cpsi, diameter 1 cm, length 1.5 cm), combining Solution Combustion Synthesis (SCS) with Wet Impregnation (WI), was addressed. First of all, the physicochemical properties of the catalyst at powder level were investigated by X-ray Diffraction (XRD), N2 adsorption (BET), and H2 chemisorption, while the morphology of final structured catalysts was evaluated by SEM analysis and mechanical strength tests by sonication. The catalytic activity towards methane Oxy-Steam Reforming (OSR) reaction was studied after the choice of the most suitable catalyst load, carrying out tests varying the temperature (500–800 °C), the oxygen-to-carbon ratio (O/C = 0.45–0.75, oxygen as moles), the steam-to-carbon ratio (S/C = 1.0–2.4), and the weight space velocity (WSV = 34,000–400,000 N ml gcat−1 h−1), in order to identify the optimum operative conditions. The results showed that a total catalytic layer load (active metal plus oxide carrier) equal to 6.5 mg cm−2 was enough to achieve excellent performances, while no substantial improvements were obtained at higher catalytic layer loads. Moreover, the coated Ru/γ-Al2O3 monolith exhibited a good catalytic activity towards the studied reaction also at considerably high WSV values (till 400,000 N ml gcat−1 h−1). 相似文献
108.
109.
Minoru Inaba Masashi SugishitaJunpei Wada Koichi MatsuzawaHirohisa Yamada Akimasa Tasaka 《Journal of power sources》2008
A long-term accelerated test (4600 h) of a 25 cm2 single cell with excess air bleeding (5%) was carried out to investigate the effects of air bleeding on membrane degradation in polymer electrolyte fuel cells. The rate of membrane degradation was negligibly low (fluoride-ion release rate = 1.3 × 10−10 mol cm−2 h−1 in average) up to 2000 h. However, membrane degradation rate was gradually increased after 2000 h. The CO tolerance of the anode gradually dropped, which indicated that the anode catalyst was deteriorated during the test. The results of the rotating ring–disk electrode measurements revealed that deterioration of Pt–Ru/C catalyst by potential cycling greatly enhances H2O2 formation in oxygen reduction reaction in the anode potential range (∼0 V). Furthermore, membrane degradation rate of the MEA increased after the anode catalyst was forced to be deteriorated by potential cycling. It was concluded that excess air bleeding deteriorated the anode catalyst, which greatly enhanced H2O2 formation upon air bleeding and resulted in the increased membrane degradation rate after 2000 h. 相似文献
110.
A simple procedure was developed for the preparation of glassy carbon electrodes modified with single wall carbon nanotubes (SWCNTs) and multilayers of SiΜο12Ο404−-[Ru(bpy)(tpy)Cl]+(byp; bipyridine, tpy; terpyridine). Layer-by-layer deposition technique was used for the multilayer formation of SiΜο12Ο404−-[Ru(bpy)(tpy)Cl]+ onto SWCNTs films. Based on the strong electrostatic attraction of oppositely charged species a Ru-complex/poly oxometalate hybrid film strongly and irreversibly adsorbed on the glassy carbon electrode modified with single walled carbon nanotubes. The multilayer assembly exhibited good stability and excellent electrochemical reversibility for both redox systems in the pH range1-7. It was found that up to fifteen monolayers could be deposited onto a carbon nanotube film with well defined redox behavior. The modified electrode shows excellent electrocatalytic activity towards sulfite oxidation. Due to synergistic effect between SWCNTs and oppositely charged species the repeated alternate adsorption of anions and cations by this simple dipping method leads to molecular sandwiches with interesting redox activity and remarkable stability. 相似文献