全文获取类型
收费全文 | 318647篇 |
免费 | 30956篇 |
国内免费 | 27344篇 |
专业分类
电工技术 | 24537篇 |
技术理论 | 14篇 |
综合类 | 24680篇 |
化学工业 | 48637篇 |
金属工艺 | 13028篇 |
机械仪表 | 25869篇 |
建筑科学 | 39261篇 |
矿业工程 | 6186篇 |
能源动力 | 8919篇 |
轻工业 | 19392篇 |
水利工程 | 6215篇 |
石油天然气 | 8336篇 |
武器工业 | 3363篇 |
无线电 | 38048篇 |
一般工业技术 | 33850篇 |
冶金工业 | 7228篇 |
原子能技术 | 3910篇 |
自动化技术 | 65474篇 |
出版年
2024年 | 1507篇 |
2023年 | 4772篇 |
2022年 | 8402篇 |
2021年 | 9936篇 |
2020年 | 9857篇 |
2019年 | 8487篇 |
2018年 | 8106篇 |
2017年 | 10771篇 |
2016年 | 11819篇 |
2015年 | 13193篇 |
2014年 | 18808篇 |
2013年 | 19758篇 |
2012年 | 23343篇 |
2011年 | 25827篇 |
2010年 | 19887篇 |
2009年 | 20061篇 |
2008年 | 20315篇 |
2007年 | 23276篇 |
2006年 | 21025篇 |
2005年 | 18081篇 |
2004年 | 15073篇 |
2003年 | 12683篇 |
2002年 | 9889篇 |
2001年 | 7757篇 |
2000年 | 6460篇 |
1999年 | 5212篇 |
1998年 | 4321篇 |
1997年 | 3542篇 |
1996年 | 2875篇 |
1995年 | 2337篇 |
1994年 | 2001篇 |
1993年 | 1434篇 |
1992年 | 1163篇 |
1991年 | 955篇 |
1990年 | 727篇 |
1989年 | 592篇 |
1988年 | 461篇 |
1987年 | 312篇 |
1986年 | 250篇 |
1985年 | 314篇 |
1984年 | 313篇 |
1983年 | 215篇 |
1982年 | 282篇 |
1981年 | 125篇 |
1980年 | 130篇 |
1979年 | 50篇 |
1978年 | 28篇 |
1977年 | 34篇 |
1976年 | 21篇 |
1959年 | 29篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
Chris Harty 《Building Research & Information》2005,33(6):512-522
An alternative approach to understanding innovation is made using two intersecting ideas. The first is that successful innovation requires consideration of the social and organizational contexts in which it is located. The complex context of construction work is characterized by inter-organizational collaboration, a project-based approach and power distributed amongst collaborating organizations. The second is that innovations can be divided into two modes: 'bounded', where the implications of innovation are restricted within a single, coherent sphere of influence, and 'unbounded', where the effects of implementation spill over beyond this. Bounded innovations are adequately explained within the construction literature. However, less discussed are unbounded innovations, where many firms' collaboration is required for successful implementation, even though many innovations can be considered unbounded within construction's inter-organizational context. It is argued that unbounded innovations require an approach to understand and facilitate the interactions both within a range of actors and between the actors and technological artefacts. The insights from a sociology of technology approach can be applied to the multiplicity of negotiations and alignments that constitute the implementation of unbounded innovation. The utility of concepts from the sociology of technology, including 'system building' and 'heterogeneous engineering', is demonstrated by applying them to an empirical study of an unbounded innovation on a major construction project (the new terminal at Heathrow Airport, London, UK). This study suggests that 'system building' contains outcomes that are not only transformations of practices, processes and systems, but also the potential transformation of technologies themselves. 相似文献
142.
143.
Non-pinched, minimum energy solutions are important class of distillation designs that offer the potential advantage of a better trade-off between capital investment and operating costs. In this paper, two important tasks associated with non-pinched distillation designs are studied. Thus the novel contributions of this work to the literature are
- (1) A comprehensive methodology for finding non-pinched minimum energy designs.
- (2) Understanding of the reasons for the existence of non-pinched distillation designs.
144.
R. A. Borzooei M. Bakhshi M. Mashinchi 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2008,12(8):739-749
In this paper, we study the lattice structure of some fuzzy algebraic systems such as (G-)fuzzy groups, some fuzzy ordered
algebras and fuzzy hyperstructures. We prove that under suitable conditions, these structures form a distributive or modular
lattice.
This research partially is supported by the “ Fuzzy Systems and its Applications Center of Excelence, Shahid Bahonar University
of Kerman, Iran”. 相似文献
145.
146.
This research investigates the utility of passive microwave remote sensing instruments to accurately determine snow water equivalent (SWE) over large spatial extents. Three existing Special Sensor Microwave Imager (SSM/I) snow water equivalent algorithms produced by Chang, Tait and Goodison were evaluated for their ability to determine snow water equivalent in a snowpack containing substantial depth hoar, large faceted snow crystals. The Kuparuk River Watershed (8140 km2) test site on the North Slope of Alaska was chosen for its snowpack containing a think depth hoar layer and long history of ground truth data. A new regional snow water equivalent algorithm was developed to determine if it could produce better results than the existing algorithms in an area known to contain significant depth hoar. The four algorithms were tested to see how well they could determine snow water equivalent: (1) on a per pixel basis, (2) across swath-averaged spatial bands of approximately 850 km2, and (3) on a watershed scale. The algorithms were evaluated to see if they captured the annual spatial distribution in snow water equivalent over the watershed. Results show that the algorithms developed by Chang and from this research are generally within 3 cm of the spatially averaged snow water equivalents over the entire watershed. The algorithms produced by Chang, Tait, and in this research were able to predict the basin-wide ground measured snow water equivalent value within a percent error range from −32.4% to 24.4% in the years with a typical snowpack. None of the algorithms produce accurate results on a pixel-by-pixel scale, with errors ranging from −26% to 308%. 相似文献
147.
在Booth算法的基础上,结合MIPS 4KC微处理器中的流水线结构和乘法器的工作过程,提出了一种改进的Booth乘法器的设计方法,并采用全制定方法实现,用这种方法实现的乘法器单元具有面积小、单元电路可重复性好、版图设计工作量小、功耗低等特点. 相似文献
148.
149.
介绍了研制出其性能达国际先进公司同类产品水平的塑封双列直插式光耦合器的工作原理和提高绝缘耐压的技术难点,从引线框架设计、加工精度控制、内包封材料选型、理想内包封形状控制、塑封气密性的实现、环境条件的完善等方面讨论了提高绝缘耐压的设计和工艺要点。 相似文献
150.