全文获取类型
收费全文 | 20587篇 |
免费 | 2526篇 |
国内免费 | 1141篇 |
专业分类
电工技术 | 6522篇 |
技术理论 | 2篇 |
综合类 | 1638篇 |
化学工业 | 2657篇 |
金属工艺 | 533篇 |
机械仪表 | 853篇 |
建筑科学 | 1847篇 |
矿业工程 | 495篇 |
能源动力 | 1037篇 |
轻工业 | 488篇 |
水利工程 | 701篇 |
石油天然气 | 1292篇 |
武器工业 | 263篇 |
无线电 | 1090篇 |
一般工业技术 | 778篇 |
冶金工业 | 454篇 |
原子能技术 | 182篇 |
自动化技术 | 3422篇 |
出版年
2024年 | 69篇 |
2023年 | 235篇 |
2022年 | 510篇 |
2021年 | 669篇 |
2020年 | 719篇 |
2019年 | 524篇 |
2018年 | 507篇 |
2017年 | 671篇 |
2016年 | 769篇 |
2015年 | 867篇 |
2014年 | 1684篇 |
2013年 | 1244篇 |
2012年 | 1908篇 |
2011年 | 2019篇 |
2010年 | 1493篇 |
2009年 | 1457篇 |
2008年 | 1274篇 |
2007年 | 1525篇 |
2006年 | 1288篇 |
2005年 | 988篇 |
2004年 | 827篇 |
2003年 | 580篇 |
2002年 | 455篇 |
2001年 | 359篇 |
2000年 | 312篇 |
1999年 | 285篇 |
1998年 | 194篇 |
1997年 | 192篇 |
1996年 | 127篇 |
1995年 | 117篇 |
1994年 | 98篇 |
1993年 | 60篇 |
1992年 | 44篇 |
1991年 | 32篇 |
1990年 | 24篇 |
1989年 | 21篇 |
1988年 | 33篇 |
1987年 | 27篇 |
1986年 | 7篇 |
1985年 | 10篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1980年 | 3篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 3篇 |
1975年 | 4篇 |
1973年 | 1篇 |
1959年 | 4篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
62.
阳离子型聚丙烯酰胺絮凝剂的开发与应用 总被引:8,自引:0,他引:8
阳离子型聚丙烯酰胺具有许多优点,极具开发研究价值,是重要的高分子絮凝剂。介绍了阳离子型聚丙烯酰胺絮凝剂的制备方法,应用及其絮凝作用机理,并分析了其发展方向。 相似文献
63.
在一定的压力作用下,将水泥浆注入松散的地基土中,浆液凝固后将松散的土粒固结在一起,对地基进行加固。这种方法具有省时、省工、省费用、使用简单方便等优点。特别是对已建油罐地基的处理更有其独到之处。由于钻孔可在任意角度下进行,因此可对罐基础任何区域进行加固并达到较好的效果。文章对钻孔布置、钻孔、注浆花管布置、压力灌浆、充水预压等几项关键技术进行了较详细的论述。 相似文献
64.
Thermal stratification in a mantled hot water storage tank is analysed numerically for different water inlet velocities. The aim is to obtain higher thermal stratification and supply hot water for usage as long as possible. Twelve different water inlet velocities to the hot water storage tank are considered. The numerical method is validated by comparing its results against experimental and numerical results from the literature. It turned out that the results obtained from the numerical analysis have shown very good agreements with the results from previous works. As a result, the water temperature in the tank increases with the increase of the water inlet velocities to the mantle but this increment is not proportional. After a period of operation of 7.2 h, which corresponds to the average sunshine duration in Turkey, temperature increments of 6.5 and 35 K have been estimated for the hot water inlet velocities of 0.01 and 0.3 m s?1, respectively, at a radial distance of 0.1 m and a height of 1 m inside the storage tank. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
65.
通过事故实例分析,阐述油罐冒罐事故的原因,并针对原因提出要加强操作人员的责任心教育,完善各项规章制度,不断提高操作人员素质,严格遵守岗位操作规程,及时消除设备缺陷、完善罐区硬件设施和罐区实行现代科学管理等项措施。 相似文献
66.
NUMERICAL SIMULATION OF TIP-CLEARANCE FLOW IN CASCADE 总被引:1,自引:1,他引:0
Chen Long Yang Chen jun Wang Guo qiangSchool of Naval Architecture Ocean Engineering Shanghai Jiaotong University Shanghai China 《水动力学研究与进展(B辑)》2003,15(1)
1 . INTRODUCTIONTip clearanceflowsoccurinvariousengineer ingapplicationssuchasaxial flow pumpsandduct edpropellers .Theinertialforcesactinguponthefluidinthenarrow gapbetweenbladetipandthesurroundingwallaresufficientto generateatipleakagevortexonthesuctions… 相似文献
67.
XU Li~ 《中国邮电高校学报(英文版)》2004,11(4)
MANET(Mobile Ad Hoc Network)is a collection of wireless mobile nodes forming a temporary communica-tion network without the aid of any established infrastructure or centralized administration.The lifetime of a MANETdepends on the battery resources of the mobile nodes.So energy consumption may one of important design criterions forMANET.With changing the idle model to sleep model in the grid environment,this paper proposes a new energy-awarerouting protocol.Performance simulation results show that the proposed strategy can dynamic balance the traffic load in-side the whole network,extend the lifetime of a MANET,and without decreasing the throughput ratio. 相似文献
68.
69.
Osasere Faraday F. Orumwense 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1994,60(4):405-411
Dispersion–flocculation studies on a Goethite–clay system using flocculants were carried out as a function of flocculant concentrations, pH of slurry, time of agitation and dispersant dosage. Also, the effects of pH and polymer concentrations on the adsorption behaviour of the system were investigated. Results show that well flocculated goethite was preferentially obtained from 4% goethite/kaolinite clay suspensions, with 50 ppm causticised starch in the slurry at pH values of 3–11·5 and with 50 ppm polyacrylamide at pH values of 3–8. Good flocs were also obtained on flocculation of the goethite suspension with 50 ppm polyacrylamide at pH values of 5–7, while the kaolinite suspension did not respond to the same dosage of causticised starch in the same pH range. Results further reveal that for the goethite/kaolinite suspension, the best results was obtained with 50 ppm polyacrylamide at pH values of 7–10. Based on the data generated in the study, it was concluded that causticised starch is a better flocculant than polyacrylamide for goethite suspensions although polyacrylamide is an excellent flocculant for kaolinite suspensions. 相似文献
70.
Several problems are encountered with asphaltenes during the exploitation, transportation, storage and treatment of crude oil. The purpose of the present work was to study the behaviour of the crude oil fraction (<210°C) by varying the temperature and doping with some hydrocarbons including solid paraffin and aromatic concentrate. The effect of flooding water was investigated. A preliminary characterization study on asphaltenes removed from the crude oil using two different solvents was performed. The state of the oil was determined by the stability factor which indicates the susceptibility of asphaltenes to agglomerate or to disperse in the continuous phase. 相似文献