全文获取类型
收费全文 | 9535篇 |
免费 | 424篇 |
国内免费 | 415篇 |
专业分类
电工技术 | 27篇 |
综合类 | 409篇 |
化学工业 | 511篇 |
金属工艺 | 6097篇 |
机械仪表 | 466篇 |
建筑科学 | 37篇 |
矿业工程 | 155篇 |
能源动力 | 24篇 |
轻工业 | 28篇 |
水利工程 | 3篇 |
石油天然气 | 14篇 |
武器工业 | 212篇 |
无线电 | 137篇 |
一般工业技术 | 1470篇 |
冶金工业 | 720篇 |
原子能技术 | 4篇 |
自动化技术 | 60篇 |
出版年
2024年 | 54篇 |
2023年 | 202篇 |
2022年 | 262篇 |
2021年 | 318篇 |
2020年 | 242篇 |
2019年 | 237篇 |
2018年 | 132篇 |
2017年 | 245篇 |
2016年 | 224篇 |
2015年 | 333篇 |
2014年 | 664篇 |
2013年 | 479篇 |
2012年 | 683篇 |
2011年 | 808篇 |
2010年 | 694篇 |
2009年 | 843篇 |
2008年 | 786篇 |
2007年 | 723篇 |
2006年 | 723篇 |
2005年 | 495篇 |
2004年 | 391篇 |
2003年 | 260篇 |
2002年 | 189篇 |
2001年 | 96篇 |
2000年 | 51篇 |
1999年 | 28篇 |
1998年 | 34篇 |
1997年 | 20篇 |
1996年 | 17篇 |
1995年 | 20篇 |
1994年 | 28篇 |
1993年 | 18篇 |
1992年 | 17篇 |
1991年 | 13篇 |
1990年 | 19篇 |
1989年 | 17篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
Al5TiB对Mg-8Zn-4Al-0.3Mn镁合金阻尼性能的影响 总被引:1,自引:1,他引:1
研究了变质剂Al5TiB对Mg-8Zn-4Al-O.3Mn镁合金阻尼性能的影响。结果表明:Al5TiB的加入显著细化了Mg-8Zn-4Al-O.3Mn镁合金晶粒,增大了界面面积,提高了合金的界面阻尼。但是,Al5TiB的加入又促进了Al、Zn原子向基体中的扩散,降低了合金的位错阻尼。加入变质剂Al5TiB后Mg-8Zn-4Al-O.3Mn镁合金的阻尼机制主要是界面阻尼和位错阻尼。二者迭加的结果决定了ZA84镁合金的宏观阻尼行为。 相似文献
83.
84.
The deformation behavior of AZ31B magnesium alloy as extruded under hot compression conditions was characterized in the temperature range of 200 - 400 ℃ and strain rate range of 0. 001 - 1 s^-1. The processing maps were obtained at different strains. The results show that the map exhibits flow instabilities as two domains. The domain at beyond 300 ℃ and strain rate of 1 s^-1 appears with a peak efficiency of power dissipation about 56% occurring. This domain is expected to happen in a hot process, such as hot rolling, hot extrusion and hot forging. There is high efficiency of power dissipation at temperature beyond 350 ℃ and strain rate 0. 001 s^-1. Such domains suggest the occurrence of superplastic deformation. 相似文献
85.
Microstructure and mechanical properties of wrought magnesium alloy AZ31B welded by laser-TIG hybrid 总被引:5,自引:0,他引:5
The laser-TIG hybrid welding was mainly used to weld the wrought magnesium alloy AZ31B. The tech-nical characteristics of laser-TIG hybrid welding process was investigated and the interactional mechanism between laser and arc was discussed, at the same time the microstructure and mechanical properties of the wrought magnesi-um alloy AZ31B using laser-TIG hybrid welding were analyzed by optical microscope, EPMA, SEM, tensile ma-chine, hardness machine. The experimental results show that the presence of laser beam boosts up the stability of the arc during high speed welding and augments the penetration of weld; the crystal grains of magnesium alloy weld are fine without porosity and cracks in the best welding criterion and the microstructure of HAZ does not become coarse obviously. The elements profile analysis reveals that Mg content in the weld is lower than that of the base metal, but Al content is higher slightly. Under this experimental condition, the wrought magnesium alloy AZ31B joint can be achieved using laser-TIG hybrid process and the tensile strength of the joint is equivalent to that of the base metal. 相似文献
86.
表面扩渗Al,Zn处理对ZM5镁合金性能的影响 总被引:8,自引:0,他引:8
通过铝锌(Al,Zn)混合粉对ZM5镁合金进行了表面固态扩渗铝锌(Al,Zn)处理,在衬底形成了Mg-Al-Zn合金层.研究结果表明:Mg-Al-Zn合金层主要由Mg-Al-Zn固溶体和Mg-Al-Zn金属间化合物(Al6Mg10Zn,Al5MgllZn4)组成,该合金层不仅使ZM5镁合金表面合金层显微硬度显著提高,而且在盐水浸泡腐蚀过程中,在衬底与腐蚀介质之间起到了良好的屏障作用,从而赋予试样良好的腐蚀性能. 相似文献
87.
热化学反应法镁合金陶瓷涂层的制备及性能的影响 总被引:4,自引:0,他引:4
采用热化学反应法在镁合金基体上制备陶瓷涂层,并对涂层进行耐磨、耐蚀等性能分析.通过XRD物相分析,涂层中有新相生成.且涂层相对基体耐磨、耐蚀性能均有所提高. 相似文献
88.
Friction stir welding of AZ31 magnesium alloy 总被引:3,自引:0,他引:3
Friction stir welding (FSW) is an new solid-phase joining technology which has more advantages over fusion welding methods in welding of aluminum and other non-ferrous metals. The effects of welding parameters on mechanical properties and microstructure during friction stir welding of AZ31 magnesium alloy were studied in this paper. Microstructures and mechanical properties of the joints were investigated by means of optical microscopy, scanning electric microscopy ( SEM ) , micro-hardness analysis, and tensile test. Experimental results show that the magnesium alloy can be successfully welded by FSW method, and the ultimate tensile strength (UTS) of FSW joint reaches up to 90 percent of base metal. The microstructures of welded joints exhibit the variation from dynamically recrystallized fine grains to greatly deformed grains. Hardness in nugget zone was found lower than the base metal but not too obvious. 相似文献
89.
Sb对Mg-4Al-2Si合金显微组织和力学性能的影响 总被引:9,自引:0,他引:9
研究了合金元素Sb对Mg-4Al-2Si合金显微组织和力学性能的影响。结果表明,加入少量的Sb(0.25%~0.75%)能有效细化汉字状Mg2Si相颗粒和α(Mg)基体组织,并在合金中形成Mg3Sb2相,提高合金的力学性能:当Sb含量为0.25%时,Mg2Si颗粒显著细化;当Sb含量为0.75%时,α(Mg)基体组织的细化效果最佳,形成了细小、均匀的α(Mg)等轴晶组织,此时合金的抗拉强度和屈服强度达到最大值;当Sb含量大于0.75%时,Mg2Si相颗粒向晶界大量偏聚并粗化,导致材料力学性能迅速下降。 相似文献
90.