全文获取类型
收费全文 | 5587篇 |
免费 | 138篇 |
国内免费 | 155篇 |
专业分类
电工技术 | 87篇 |
技术理论 | 1篇 |
综合类 | 411篇 |
化学工业 | 1030篇 |
金属工艺 | 331篇 |
机械仪表 | 890篇 |
建筑科学 | 339篇 |
矿业工程 | 251篇 |
能源动力 | 222篇 |
轻工业 | 463篇 |
水利工程 | 69篇 |
石油天然气 | 357篇 |
武器工业 | 26篇 |
无线电 | 282篇 |
一般工业技术 | 354篇 |
冶金工业 | 168篇 |
原子能技术 | 101篇 |
自动化技术 | 498篇 |
出版年
2024年 | 6篇 |
2023年 | 40篇 |
2022年 | 82篇 |
2021年 | 100篇 |
2020年 | 109篇 |
2019年 | 73篇 |
2018年 | 79篇 |
2017年 | 64篇 |
2016年 | 91篇 |
2015年 | 122篇 |
2014年 | 215篇 |
2013年 | 280篇 |
2012年 | 241篇 |
2011年 | 348篇 |
2010年 | 241篇 |
2009年 | 298篇 |
2008年 | 265篇 |
2007年 | 289篇 |
2006年 | 292篇 |
2005年 | 293篇 |
2004年 | 263篇 |
2003年 | 261篇 |
2002年 | 254篇 |
2001年 | 213篇 |
2000年 | 192篇 |
1999年 | 176篇 |
1998年 | 177篇 |
1997年 | 150篇 |
1996年 | 156篇 |
1995年 | 114篇 |
1994年 | 76篇 |
1993年 | 60篇 |
1992年 | 54篇 |
1991年 | 41篇 |
1990年 | 55篇 |
1989年 | 42篇 |
1988年 | 28篇 |
1987年 | 14篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 8篇 |
1983年 | 5篇 |
1982年 | 2篇 |
1980年 | 2篇 |
1964年 | 1篇 |
1960年 | 1篇 |
排序方式: 共有5880条查询结果,搜索用时 15 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(65):28152-28164
The combustion characteristics of ammonia/methanol mixtures were investigated numerically in this study. Methanol has a dramatic promotive effect on the laminar burning velocity (LBV) of ammonia. Three mechanisms from literature and another four self-developed mechanisms constructed in this study were evaluated using the measured laminar burning velocities of ammonia/methanol mixtures from Wang et al. (Combust.Flame. 2021). Generally, none of the selected mechanisms can precisely predict the measured laminar burning velocities at all conditions. Aiming to develop a simplified and reliable mechanism for ammonia/methanol mixtures, the constructed mechanism utilized NUI Galway mechanism (Combust.Flame. 2016) as methanol sub-mechanism and the Otomo mechanism (Int. J. Hydrogen. Energy. 2018) as ammonia sub-mechanism was optimized and reduced. The reduced mechanism entitled ‘DNO-NH3’, can accurately reproduce the measured laminar burning velocities of ammonia/methanol mixtures under all conditions. A reaction path analysis of the ammonia/methanol mixtures based on the DNO-NH3 mechanism shows that methanol is not directly involved in ammonia oxidation, instead, the produced methyl radicals from methanol oxidization contribute to the dehydrogenation of ammonia. Besides, NOx emission analysis demonstrates that 60% methanol addition results in the highest NOx emissions. The most important reactions dominating the NOx consumption and production are identified in this study. 相似文献
2.
《International Journal of Project Management》2020,38(1):27-35
26 interviews were conducted with a snowball sample of project managers to explore how project managers were influenced by accountability arrangements and how they responded to accountability demands. Using a grounded theory approach to code the interview data, this study revealed that project managers develop new skills to respond to accountability demands. These effects are facilitated by the interaction of resource-based mechanisms and reflexivity that interact with the contextual factors of the project. The study broadens the understanding of accountability in project management and suggests a model for further empirical examination. 相似文献
3.
Fatigue crack growth behaviour of Ti–6Al–2Zr–1.5Mo–1.5V (VT-20 a near-α Ti alloy) was studied in lamellar, bimodal and acicular microstructural conditions. Fatigue crack growth tests at both increasing and decreasing stress intensity factor range values were performed at ambient temperature and a loading ratio of 0.3 using compact tension samples. Lamellar and acicular microstructures showed lower fatigue crack growth rates as compared to the bimodal microstructure due to the tortuous nature of cracks in the former and the cleavage of primary α in the latter. The threshold stress intensity factor range was highest for acicular microstructure. 相似文献
4.
乙烯齐聚催化剂研究进展 总被引:1,自引:0,他引:1
乙烯齐聚是合成直链低碳α-烯烃最先进的方法,直链低碳α-烯烃可用于生产低密度聚乙烯和高密度聚乙烯等多种精细化学品。本文综述了乙烯齐聚催化体系的研究进展,重点介绍了镍、锆、钛催化剂的组成以及反应时间、反应温度、溶剂、助催化剂等因素对乙烯齐聚活性和选择性的影响,并讨论了典型镍的催化机理。 相似文献
5.
6.
水泥土桩已普遍用于多层住宅的地基处理,根据水泥土和夯扩挤密施工法的特点,在对夯扩挤密水泥土桩用于高层建筑地基处理进行研究、阐明其经济合理且安全可行的基础上,在高层住宅工程中进行了尝试,已取得令人满意的效果。 相似文献
7.
采用晶种技术,能有效地改善熟料的煅烧过程和熟料的质量。晶种和复合矿化剂的作用机理不同,在某些方面具有互补性。 相似文献
8.
9.
多元羧酸防皱机理的探讨 总被引:15,自引:2,他引:13
多元羧酸的防皱机理是近期织物防皱整理研究讨论的热点。其中,催化剂在体系中所起的作用现有多种说法,如催化成酐,催化成酯,以及既催化成酐又催化成酯和其他一些观点。本文就多元羧酸的防皱机理作一分析和归纳,并提出一些看法。 相似文献
10.
A framework of virtual prototyping environment for the design and analysis of mechanical mechanism with clearance 总被引:7,自引:0,他引:7
Mechanical mechanisms with clearance abound in technological fields such as robotics, machine and steam turbine industry. The dynamic performance of these mechanisms in working condition can be achieved provided that the effects of the different on the mechanisms (such as mechanism dynamics, technological effects and thermal behaviour) are thoroughly understood. Virtual prototyping provides an integration of multi-domain dynamic simulation for the design and analysis process. In the current paper, a framework of virtual prototyping environment for the design and analysis of mechanical mechanism with clearance is presented. A case study with such a simulation strategy is studied for the optimum design and analysis of the technological parameter. 相似文献