全文获取类型
收费全文 | 14770篇 |
免费 | 1036篇 |
国内免费 | 465篇 |
专业分类
电工技术 | 156篇 |
综合类 | 988篇 |
化学工业 | 1330篇 |
金属工艺 | 4494篇 |
机械仪表 | 4424篇 |
建筑科学 | 114篇 |
矿业工程 | 549篇 |
能源动力 | 180篇 |
轻工业 | 309篇 |
水利工程 | 70篇 |
石油天然气 | 450篇 |
武器工业 | 177篇 |
无线电 | 245篇 |
一般工业技术 | 1794篇 |
冶金工业 | 797篇 |
原子能技术 | 31篇 |
自动化技术 | 163篇 |
出版年
2024年 | 115篇 |
2023年 | 324篇 |
2022年 | 439篇 |
2021年 | 494篇 |
2020年 | 511篇 |
2019年 | 453篇 |
2018年 | 501篇 |
2017年 | 641篇 |
2016年 | 585篇 |
2015年 | 534篇 |
2014年 | 629篇 |
2013年 | 644篇 |
2012年 | 777篇 |
2011年 | 836篇 |
2010年 | 658篇 |
2009年 | 739篇 |
2008年 | 611篇 |
2007年 | 938篇 |
2006年 | 953篇 |
2005年 | 707篇 |
2004年 | 695篇 |
2003年 | 551篇 |
2002年 | 466篇 |
2001年 | 407篇 |
2000年 | 335篇 |
1999年 | 276篇 |
1998年 | 244篇 |
1997年 | 259篇 |
1996年 | 218篇 |
1995年 | 186篇 |
1994年 | 120篇 |
1993年 | 76篇 |
1992年 | 80篇 |
1991年 | 57篇 |
1990年 | 45篇 |
1989年 | 47篇 |
1988年 | 39篇 |
1987年 | 23篇 |
1986年 | 6篇 |
1985年 | 14篇 |
1984年 | 14篇 |
1983年 | 8篇 |
1982年 | 13篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
合金元素对低合金耐磨铸钢力学性能的影响 总被引:1,自引:3,他引:1
研究了低合金耐磨铸钢中台金元素C、Si、Mn、Mo,对钢的力学性能等的影响。结果表明,合金元素的合理有效搭配,可使钢在连续空冷条件下得到贝氏体为主的显微组织:钢中C、Mn含量增加,其硬度上升,冲击韧度下降,其中以Mn影响最大,C次之:Si、Mo对钢性能影响程度较小,均在研究的中等含量处取得性能的最佳值。 相似文献
82.
深冷处理与工模具的耐磨性 总被引:8,自引:2,他引:8
热处理后的金属材料再经低落曙处理,其力学能明显提高,尤其是高碳高合金工模具钢的耐磨性提高特别显著。本文着重研究了应用面较广的W6Mo5Cr4V2钢的处理工艺制度,组织性能及其磨损机理。 相似文献
83.
84.
FS-1化学镀Ni-P镀层的性能研究 总被引:4,自引:0,他引:4
采用XRD与SEM分析技术、电化学阳极极化曲线测试和 摩擦磨损试验等,系统地研究了FS-1化学镀Ni-P镀层的结构和性能.结果表明:该镀层具有 优良的耐蚀和耐磨性能,热处理虽可以显著地提高镀层的耐磨性能,但使其耐蚀性能有所降 低. 相似文献
85.
By use of X-ray diffractometry and scanning electron microscope(SEM),the friction and wear results obtained from MM-1000 dynamometer tests of CVI pitch/resin C/C composites were analyzed.By investigating the factors that affected the friction and wear properties,such as matrix carbon,applcation environment,graphitization degree and brake pressure,etc,friction and wear mechanism of carbon materials were probed.The results indicate that pitch densified CVI initially treated composite is more graphitizable with its graphitization degree up 59 62%,and which results in uniform small debris easier to generate,more smooth friction curves with the coefficient of 0.3-0.4 and relatively higher wear and mass loss,compared with CVI/resin C/C composites.It was further proved by SEM observation that tribological behavior of C/C composite was system dependent.Factors determining the friction and wear properties such as the size of debris and its influence on friction and wear,brake pressure,graphization degree and debris bilm formation interacted and affected each other.The friction and wear mechanism of C/C composites under different high temperature treatments needs further research. 相似文献
86.
It is well known that the mechanical properties such as strength and hardness of structural steel are usually enhanced by the martensite-phase transformation method. In many industrial applications, hardness has always been used as an index to reflect the wear-resistance performance. As a result, steel is quenched to a large extent in order to increase the hardness and wear-resistance performance. In general, from the wear mechanism, no exact relationship between the hardness and wear resistance of materials can be formulated. Also there are few conclusive studies on the effects of running procedures on wear-resistance performance. Therefore, the friction behavior of S45C carbon steel with and without a quenching process was evaluated by a rotating tribometer under various test conditions. The experimental results show that the running conditions cause a great influence on the wear-resistance performance of the materials. Under low speed and light apparent pressure conditions, the quenched specimens have high wear-resistance performance. Contrarily, at high speed and heavy loading, the wear-resistance performance of hardened specimens decreases due to tempering effects at the rubbing surface when the contact temperature becomes increased. Therefore, this causes more severe wear to the hardened specimens than to the unhardened specimens. 相似文献
87.
High-speed milling of titanium alloys using binderless CBN tools 总被引:4,自引:0,他引:4
Z. G. Wang Y. S. Wong M. Rahman 《International Journal of Machine Tools and Manufacture》2005,45(1):105-114
The performance of conventional tools is poor when used to machine titanium alloys. In this paper, a new tool material, which is binderless cubic boron nitride (BCBN), is used for high-speed milling of a widely used titanium alloy Ti–6Al–4V. The performance and the wear mechanism of the BCBN tool have been investigated when slot milling the titanium alloy in terms of cutting forces, tool life and wear mechanism. This type of tool manifests longer tool life at high cutting speeds. Observations based on the SEM and EDX suggest that adhesion of workpiece and attrition are the main wear mechanisms of the BCBN tool when used in high-speed milling of Ti–6Al–4V. 相似文献
88.
Cr3Si/Crl3Ni5Si2金属间化合物合金组织与高温滑动磨损性能的研究 总被引:2,自引:0,他引:2
利用水冷铜模激光熔炼炉制得了由初生枝晶Cr3Si和枝晶间Cr3Si/Crl3Ni5Si2共晶组成的金属间化合物合金。利用OM,SEM,TEM,EDS和XRD分析了该金属间化合物的显微组织,在400℃,500℃和600℃条件下测试了其耐磨性能。结果表明,由于Cr3Si和Crl3NisSi2硬度高、原子键合力强、组织细小、均匀,在高温滑动磨损条件下具有优良的耐磨性能。 相似文献
89.
90.