全文获取类型
收费全文 | 8960篇 |
免费 | 901篇 |
国内免费 | 513篇 |
专业分类
电工技术 | 351篇 |
综合类 | 725篇 |
化学工业 | 1076篇 |
金属工艺 | 1047篇 |
机械仪表 | 1004篇 |
建筑科学 | 833篇 |
矿业工程 | 444篇 |
能源动力 | 426篇 |
轻工业 | 419篇 |
水利工程 | 188篇 |
石油天然气 | 566篇 |
武器工业 | 90篇 |
无线电 | 940篇 |
一般工业技术 | 1089篇 |
冶金工业 | 586篇 |
原子能技术 | 223篇 |
自动化技术 | 367篇 |
出版年
2024年 | 38篇 |
2023年 | 119篇 |
2022年 | 242篇 |
2021年 | 304篇 |
2020年 | 336篇 |
2019年 | 257篇 |
2018年 | 257篇 |
2017年 | 339篇 |
2016年 | 394篇 |
2015年 | 393篇 |
2014年 | 597篇 |
2013年 | 615篇 |
2012年 | 650篇 |
2011年 | 701篇 |
2010年 | 581篇 |
2009年 | 548篇 |
2008年 | 414篇 |
2007年 | 485篇 |
2006年 | 565篇 |
2005年 | 377篇 |
2004年 | 346篇 |
2003年 | 297篇 |
2002年 | 239篇 |
2001年 | 202篇 |
2000年 | 185篇 |
1999年 | 164篇 |
1998年 | 133篇 |
1997年 | 90篇 |
1996年 | 90篇 |
1995年 | 69篇 |
1994年 | 60篇 |
1993年 | 58篇 |
1992年 | 49篇 |
1991年 | 46篇 |
1990年 | 35篇 |
1989年 | 24篇 |
1988年 | 16篇 |
1987年 | 7篇 |
1986年 | 13篇 |
1985年 | 12篇 |
1984年 | 12篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1959年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
简要介绍了WZDQ30C型真空加压气淬炉的结构及其特点,总结了在调诗过程中的一些体会,对典型软磁材料进行了真空热处理并测定了热处理后的磁性能。 相似文献
952.
该文通过黄河西霞院夹砂层勘察存在的问题,引出了地层薄层地震反射同相轴出现的理论依据,从而计算出在本地区探测地层薄层厚度的分辨率。 相似文献
953.
954.
955.
本研究在通过国内外调研分析基础上,结合上海道路路面设计实践,对预制块路面设计,提出采用等效厚度及典型结构经验法;对有关技术标准作了充实完善;对用于人行道和车行道预制块路面提出了质量要求和规定的探讨 相似文献
956.
The electric power generation and oil/gas production industries have a strong interest in the physical characterization of conducting and non-conducting liquid films that are formed during the flow of liquids in pipes. Conducting and non-conducting liquid films do not lend themselves to the same characterization techniques due to the different requirements originating from their electrical properties. Techniques based on the use of ultrasound are extremely attractive for that purpose as they do not depend on the electrical properties of the liquid and are also non-invasive. This paper presents the application of ultrasonic techniques for measuring the thickness of wavy thin liquid films (<6 mm) in vertical pipes. Initial benchtop experiments were performed, and different signal processing methods were implemented in order to identify the most suitable depending on the film thickness. For a film thickness >0.5 mm a time of flight method was utilized whereas for a film thicknesses <0.5 mm a frequency method and time domain method were utilized. These methods were validated using a theoretical volume measurement on a static system. The studied methods were then tested on downward and upward vertical flow experimental rigs with pipe diameters of 127 mm and 34.5 mm respectively. The results of the experiments using ultrasonic methods showed good agreement with the measurements obtained using a multi pin film sensor and a concentric conductance probe, highlighting the potential that ultrasound offers in thin film measurements. 相似文献
957.
基于Fluent软件,建立高炉冷却壁三维稳态传热模型,通过对不同结构参数下的铸铁冷却壁温度场的计算,分析了水管直径、水管中心线距冷却壁热面距离、槽深度、壁体厚度等因素对高炉冷却壁温度分布的影响。计算结果表明:在一定范围内,增大水管直径、减小水管中心线距冷却壁热面距离、减小槽深度、减小壁体厚度都可以降低冷却壁热面温度,延长冷却壁寿命。优化后的冷却壁与原冷却壁相比,相应的冷却壁热面温度降低了51.2℃,冷面温度降低了14.0℃,冷热面温差降低了37.2℃,冷却性能有较大幅度的提高。 相似文献
958.
959.
Mode I fatigue crack growth tests were conducted on joints bonded with a filled adhesive (A) at 20 Hz and 2 Hz and on joints bonded with a filled and toughened adhesive (B) at 20 Hz, 2 Hz, 0.2 Hz and 0.02 Hz. Strain energy release rate, G, and J-integral were evaluated based on elastic and elastoplastic finite element analyses (FEA) of the joints bonded with adhesive A and B, respectively. For the configurations considered, J was found to be path-independent and did not differ much from G. The fatigue crack growth rate (FCGR), da/dN, in the joints bonded with adhesive A was relatively independent of frequency while it increased with decreasing frequency at given δ for the joints bonded with adhesive B. The fatigue processes in both adhesives involved the cracking of the filler particles and subsequent linkage of the resultant microcracks. The process zone in adhesive B is larger than that in adhesive A and it increases with decreasing frequency. It is suggested that this variation in process zone size can account for the observed fatigue behaviour. The fatigue crack growth velocity, da/dt, was also calculated for the joints bonded with adhesive B and the variation of da/dt with test frequency at given δG is much smaller than the variation in da/dN, suggesting a creep effect in the fatigue crack growth. 相似文献
960.