全文获取类型
收费全文 | 15087篇 |
免费 | 1641篇 |
国内免费 | 1243篇 |
专业分类
电工技术 | 836篇 |
技术理论 | 1篇 |
综合类 | 1325篇 |
化学工业 | 2362篇 |
金属工艺 | 448篇 |
机械仪表 | 698篇 |
建筑科学 | 1622篇 |
矿业工程 | 186篇 |
能源动力 | 532篇 |
轻工业 | 1020篇 |
水利工程 | 378篇 |
石油天然气 | 307篇 |
武器工业 | 162篇 |
无线电 | 1246篇 |
一般工业技术 | 2471篇 |
冶金工业 | 752篇 |
原子能技术 | 294篇 |
自动化技术 | 3331篇 |
出版年
2024年 | 87篇 |
2023年 | 401篇 |
2022年 | 610篇 |
2021年 | 753篇 |
2020年 | 623篇 |
2019年 | 552篇 |
2018年 | 525篇 |
2017年 | 614篇 |
2016年 | 626篇 |
2015年 | 596篇 |
2014年 | 936篇 |
2013年 | 1041篇 |
2012年 | 971篇 |
2011年 | 1038篇 |
2010年 | 753篇 |
2009年 | 816篇 |
2008年 | 819篇 |
2007年 | 856篇 |
2006年 | 742篇 |
2005年 | 684篇 |
2004年 | 559篇 |
2003年 | 495篇 |
2002年 | 453篇 |
2001年 | 357篇 |
2000年 | 302篇 |
1999年 | 266篇 |
1998年 | 221篇 |
1997年 | 195篇 |
1996年 | 150篇 |
1995年 | 165篇 |
1994年 | 107篇 |
1993年 | 91篇 |
1992年 | 84篇 |
1991年 | 71篇 |
1990年 | 73篇 |
1989年 | 71篇 |
1988年 | 62篇 |
1987年 | 31篇 |
1986年 | 15篇 |
1985年 | 22篇 |
1984年 | 19篇 |
1983年 | 21篇 |
1982年 | 15篇 |
1980年 | 9篇 |
1979年 | 8篇 |
1966年 | 6篇 |
1964年 | 6篇 |
1959年 | 7篇 |
1958年 | 5篇 |
1955年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
31.
32.
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
33.
GAO Qinglu~ WU Bo~ GUO Guang~ .School of Management Wuhan University of Technology Wuhan China .School of Mechanical Engineering Huazhong University of Science Technology Wuhan China 《武汉理工大学学报》2006,28(Z2)
This article puts forward a scheduling method for nonlinear process plan shop floor.Task allocation and load bal- ance are realized by bidding mechanism.Though the agent interaction process,the execution of tasks is determined and the coherence of manufacturing decision is verified.The employment of heuristic index can help to optimize the system performance. 相似文献
34.
G. Ranzi M. A. Bradford B. Uy 《International journal for numerical methods in engineering》2004,61(5):657-672
The use of the conventional semi-analytical stiffness method in finite element analysis, in which interpolation polynomials are used to develop the stiffness relationships, leads to problems of curvature locking when beam-type elements are developed for composite members with partial interaction between the materials of which it is comprised. The curvature locking phenomenon that occurs for composite steel–concrete members is quite well reported, and the general approach to minimizing the undesirable ramifications of curvature locking has been to use higher-order polynomials with increasing numbers of internal nodes. This paper presents an alternate formulation based on a direct stiffness approach rather than starting from pre-defined interpolation polynomials, and which does not possess the undesirable locking characteristics. The formulation is based on a more general approach for a bi-material composite flexural member, whose constituent materials are joined by elastic shear connection so as to provide partial interaction. The stiffness relationships are derived, and these are applied to a simply supported and a continuous steel–concrete composite beam to demonstrate the efficacy of the method, and in particular its ability to model accurately both very flexible and very stiff shear connection that causes difficulties when implemented in competitive semi-analytical algorithms. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
35.
36.
四种别藻蓝蛋白三聚体的时间分辨荧光光谱研究 总被引:6,自引:0,他引:6
研究了从Anabanavaribilis中提取的4种别藻蓝蛋白APCI,APCII,APCII及APCB三聚体的稳态光谱和皮秒荧光光谱。采用Monte-Carlo方法对瞬态荧光光谱进行拟合,实验结果表明:APCI荧光有两个带,其中第一个带位于662nm,有两个时间组分:35.8ps和1.67ns;第二个带位于680nm,有两个时间组分:34.2ps和1.64ns;APCII瞬态荧光位于660nm,有两个时间组分:20.4ps和1.64ns;APCII瞬态荧光位于660nm,有两个时间组分:23.8ps和1.76ns;APCB瞬态荧光有两个带,其中第一个带位于662nm,有两个时间组分:36.6ps和1.45ns;第二个带位于680nm,有两个时间组分:25.8ps和1.62ns。实验结果一方面说明了藻胆体核内4种别藻蓝蛋白形成能量传递的两条途径;另一方面瞬态荧光解叠结果揭示了APCI和APCB三聚体内能量传递的超快过程。 相似文献
37.
Al-Li alloys being developed as lighter, substitutes for conventional high strength Al alloys are to be processed by routine
methods. During extrusion of a 8090 Al-Li alloy, the extrusion die container failed causing some alarm. This failed die container
was analysed to examine if the failure was caused by interaction of Li diffusing out of Al-Li alloy with the carbides of die
steel. The evidence, although not conclusive, is sufficient to exercise caution during such processing. 相似文献
38.
Vladimir Kulyukin Chaitanya Gharpure John Nicholson Grayson Osborne 《Autonomous Robots》2006,21(1):29-41
We present a robot-assisted wayfinding system for the visually impaired in structured indoor environments. The system consists
of a mobile robotic guide and small passive RFID sensors embedded in the environment. The system is intended for use in indoor
environments, such as office buildings, supermarkets and airports. We describe how the system was deployed in two indoor environments
and evaluated by visually impaired participants in a series of pilot experiments. We analyze the system’s successes and failures
and outline our plans for future research and development. 相似文献
39.
ZRS-6.72—3型电收尘器原设计用于13.8kt/a锌冶炼烟气收尘制酸工艺中,因电收尘器使用时间长,电源控制柜故障率高和沸腾炉扩大更新,对电收尘器同步进行配套技术改造。改造为CRS-8.24—3型电收尘器后,又陆续使用了HL-Ⅲ型恒流源控制电柜,投产后的电收尘器具有收尘效率高、电场运行稳定等特点。 相似文献
40.
The paper presents experimental results of secondary ion energy distributions obtained for Ti and Si targets bombarded by 20-30 keV monoisotope Ar+ ion beam. The influence of the extraction voltages between target and a slit of the electrostatic energy analyzer entrance on the energy distributions of secondary ions was investigated. After optimization of the secondary ion extraction system, the mass spectra of secondary ions were also measured. The investigations were done using recently built experimental system. Experimental data are compared with the computer simulation results obtained using TRQR and SATVAL codes. 相似文献