全文获取类型
收费全文 | 831篇 |
免费 | 131篇 |
国内免费 | 22篇 |
专业分类
电工技术 | 25篇 |
综合类 | 29篇 |
化学工业 | 12篇 |
金属工艺 | 194篇 |
机械仪表 | 59篇 |
建筑科学 | 4篇 |
矿业工程 | 2篇 |
能源动力 | 7篇 |
轻工业 | 1篇 |
石油天然气 | 43篇 |
武器工业 | 2篇 |
无线电 | 394篇 |
一般工业技术 | 68篇 |
冶金工业 | 11篇 |
原子能技术 | 3篇 |
自动化技术 | 130篇 |
出版年
2023年 | 2篇 |
2022年 | 6篇 |
2021年 | 13篇 |
2020年 | 17篇 |
2019年 | 11篇 |
2018年 | 17篇 |
2017年 | 30篇 |
2016年 | 35篇 |
2015年 | 27篇 |
2014年 | 37篇 |
2013年 | 57篇 |
2012年 | 45篇 |
2011年 | 62篇 |
2010年 | 35篇 |
2009年 | 48篇 |
2008年 | 57篇 |
2007年 | 52篇 |
2006年 | 62篇 |
2005年 | 33篇 |
2004年 | 42篇 |
2003年 | 33篇 |
2002年 | 27篇 |
2001年 | 29篇 |
2000年 | 30篇 |
1999年 | 16篇 |
1998年 | 21篇 |
1997年 | 23篇 |
1996年 | 22篇 |
1995年 | 23篇 |
1994年 | 17篇 |
1993年 | 15篇 |
1992年 | 18篇 |
1991年 | 7篇 |
1990年 | 2篇 |
1989年 | 8篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1984年 | 1篇 |
排序方式: 共有984条查询结果,搜索用时 15 毫秒
41.
介绍了巴基斯坦恰希玛核电C-2工程安全壳钢衬里筒体的基本状况,论述了SAW焊接方法防止产生终端裂纹的方法,指出理顺主要工艺参数的匹配关系是消除焊缝宽度窄而余高大的基本控制方法,正确选择焊剂的颗粒度,并合理回收使用焊剂是减小气孔及焊缝表面压气、凹坑缺陷的重要途径,通过二次切割可减小翘曲等波浪变形现象。经验的总结可有效地指导大而薄钢板的拼焊生产,加强过程控制可保证焊缝的焊接质量。 相似文献
42.
针对现有变电站安全监测系统存在平台冗余、系统分散、信息无法共享等不足,设计了一种基于IEC61850的智能变电站安全在线监测系统,包括周界安防子系统和电气设备温度在线监测子系统,以及变电站安全信息管理子系统。将变电站周界安全信息和设备在线温度信息按照IEC 61850标准统一建模,实现安全测控系统平台的集成。采用激光围栏检测周界入侵信号;使用网络摄像机监视入侵动作;采用新型的声表面波温度传感器进行温度采集,实现了全自动、全天候的实时在线监测变电站周界安防入侵信息和运行设备在线温度信息,为智能变电站的发展提供一种有力的技术支撑与工程参考。 相似文献
43.
0 INTRODUCTIONItisstilldifficulttodetectsignalsfromtopsideofweldpoolforpenetrationcontroluptothepresent .Thestickingpointishowtoeffectivelyacquiresignalsthatre flectfullpenetration .Techniquesalreadyknownincludeultrasonicdetection ,infraredsensing ,weldpo… 相似文献
44.
This paper deals with propagation of Love type waves in a Piezomagnetic layer with corrugated boundaries overlying an inhomogeneous half-space. Inhomogeneity of elastic half-space is caused due to exponential variations in elastic parameters. Dispersion relations are obtained for magnetically open and short cases. Prominent effects of inhomogeneity, layer's width and corrugation on the phase velocity of considered wave are illustrated through graphs. Some particular cases are derived and exhibited through graphs. Also the influence of undulation parameter, elastic parameter, and piezomagnetic coefficient on phase velocity of considered wave has been marked separately. The present study finds its applications in designing and optimization of Love wave sensors and Seismic Acoustic Wave (SAW) devices. Findings may also be used for analytical study of wave propagation in piezomagnetic coupled structures. 相似文献
45.
46.
《Energy Materials: Materials Science and Engineering for Energy Systems》2013,8(4):1184-1190
AbstractDegradation of AISI 410 martensitic stainless steel, a typical alloy for many applications such as steam turbine blade, could impair its efficiency and lifetime. To overcome this problem, critical surfaces could be modified by weld cladding via gas tungsten arc welding technique. In the present research, a comparative study of Stellite 21 weld overlays deposited in three different thicknesses, i.e. dilutions, at various preheat and post-weld heat treatment temperatures on the surface of AISI 410 martensitic stainless steel, has been made. The surface of coatings has been examined to reveal their microstructures, phase characterisation and mechanical properties using XRD, microhardness tester and metallographic techniques. The results showed that the deposition of Stellite 21 coating on AISI 410 martensitic stainless steel improved its corrosion resistance. Moreover, the volumetric dilution had a considerable effect on the hardness, microstructure and electrochemical corrosion behaviour of Stellite 21 weld overlays. 相似文献
47.
A study of port plug distortion resulting from narrow gap combined GTAW & SMAW and Electron Beam Welding was carried out. Thermomechanical finite element analysis of port plug becomes virtually impossible because of the requirement of huge number of nodes and elements. Hence an analysis method based on the concept of inherent strain was used in this work. The computational time required was about 40-50 min only in a Core (TM) 2 Duo, 2.66 GHz computer with 2 GB RAM, which otherwise was not possible with other conventional computation techniques. As was expected the overall distortion due to EB welding was found to be less compared to that of narrow gap GTAW & SMAW. 相似文献
48.
A comparison has been made of the relationship between microstructure and microhardness developed by surface melting Nanosteel SHS 7170 Fe–Cr–B alloy powder onto a plain carbon steel surface. This powder was initially developed as a high velocity oxyfuel sprayed coating, giving a strength 10 times that of mild steel, and is particularly suitable for surface protection against wear and corrosion. In the present study, the alloy powder was injected into the laser melted surface, while a preplaced powder was melted using the gas tungsten arc welding (GTAW) technique. The laser track consisted of fine dendrites and needle-like microstructures, which produced a maximum hardness value of over 800 HV, while the GTAW track produced a mixture of equiaxed and columnar grain microstructures with a maximum hardness value of 670 HV. The lower hardness values are considered to be associated with dilution and grain size. 相似文献
49.
50.
提出了将纳米线技术与声表面波(SAW)技术相结合,分别利用纳米线气体敏感材料比表面积高,声表面波传感器质量敏感性高的优点,探索研制新一代声表面波气体传感器。该传感器具有响应速度快,灵敏度高,体积小,质量注和易集成等优点。该文主要从SAW专用芯片的研制、专用纳米线研制、专用纳米线的表面修饰与改性研究、检测电路设计等4方面进行了阐述。理论计算表明,相比传统二维结构的SAW气体传感器,三维纳米线结构的SAW气体传感器的在灵敏度和响应速度上都得到提高。 相似文献