全文获取类型
收费全文 | 5370篇 |
免费 | 327篇 |
国内免费 | 199篇 |
专业分类
电工技术 | 66篇 |
技术理论 | 1篇 |
综合类 | 165篇 |
化学工业 | 843篇 |
金属工艺 | 1331篇 |
机械仪表 | 324篇 |
建筑科学 | 57篇 |
矿业工程 | 272篇 |
能源动力 | 81篇 |
轻工业 | 89篇 |
水利工程 | 5篇 |
石油天然气 | 21篇 |
武器工业 | 30篇 |
无线电 | 74篇 |
一般工业技术 | 1219篇 |
冶金工业 | 1251篇 |
原子能技术 | 23篇 |
自动化技术 | 44篇 |
出版年
2024年 | 4篇 |
2023年 | 68篇 |
2022年 | 133篇 |
2021年 | 154篇 |
2020年 | 162篇 |
2019年 | 116篇 |
2018年 | 148篇 |
2017年 | 171篇 |
2016年 | 158篇 |
2015年 | 145篇 |
2014年 | 284篇 |
2013年 | 365篇 |
2012年 | 244篇 |
2011年 | 442篇 |
2010年 | 259篇 |
2009年 | 254篇 |
2008年 | 232篇 |
2007年 | 297篇 |
2006年 | 325篇 |
2005年 | 260篇 |
2004年 | 230篇 |
2003年 | 229篇 |
2002年 | 171篇 |
2001年 | 181篇 |
2000年 | 133篇 |
1999年 | 135篇 |
1998年 | 106篇 |
1997年 | 110篇 |
1996年 | 75篇 |
1995年 | 85篇 |
1994年 | 66篇 |
1993年 | 46篇 |
1992年 | 29篇 |
1991年 | 9篇 |
1990年 | 19篇 |
1989年 | 12篇 |
1988年 | 10篇 |
1987年 | 5篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有5896条查询结果,搜索用时 15 毫秒
41.
豆志河 《稀有金属材料与工程》2020,49(3):862-870
炉外铝热反应制备的高钛铁合金由于Al、O含量高,不能直接用于钢水精炼过程。本文研究了高铝高钛铁在钢液精炼过程中的热力学,以及高钛铁中铝和铁含量对钢液精炼过程的影响。结果表明:采用Ti和Al作为复合脱氧剂,在1873K当钢水中的aTi/aAl大于8时,脱氧产物为Ti2O3;但事实上,只有当液态钢中的aTi/aAl值高于10时,Ti2O3才会作为脱氧产物沉淀。采用高铝高钛铁作为脱氧剂,钢水中铝和钛的含量可以满足相关钢的成分要求。随着高钛铁含量的增加,精炼后的铸钢中夹杂物由硅酸盐转变为Ti-Al-Mn复合夹杂物;同时,在这些夹杂物周围形成径向针状铁素体,细化了钢的微观结构。实际系统中的aTi/aAl值为17.78(> 8),与理论结果一致。当钢液中的氧含量高时,控制钢水中aTi/aAl的值是至关重要的。 相似文献
42.
《中国有色金属学会会刊》2020,30(9):2339-2354
Al−2CNTs−xAl2O3 nanocomposites were manufactured by a hybrid powder metallurgy and microwave sintering process. The correlation between process-induced microstructural features and the material properties including physical and mechanical properties as well as ultrasonic parameters was measured. It was found that physical properties including densification and physical dimensional changes were closely associated with the morphology and particle size of nanocomposite powders. The maximum density was obtained by extensive particle refinement at milling time longer than 8 h and Al2O3 content of 10 wt.%. Mechanical properties were controlled by Al2O3 content, dispersion of nano reinforcements and grain size. The optimum hardness and strength properties were achieved through incorporation of 10 wt.% Al2O3 and homogenous dispersion of CNTs and Al2O3 nanoparticles (NPs) at 12 h of milling which resulted in the formation of high density of dislocations and extensive grain size refinement. Also both longitudinal and shear velocities and attenuation increase linearly by increasing Al2O3 content and milling time. The variation of ultrasonic velocity and attenuation was attributed to the degree of dispersion of CNTs and Al2O3 and also less inter-particle spacing in the matrix. The larger Al2O3 content and more homogenous dispersion of CNTs and Al2O3 NPs at longer milling time exerted higher velocity and attenuation of ultrasonic wave. 相似文献
43.
为改善边界润滑工况下铁基含油轴承材料的摩擦学性能,采用低温液体渗硫技术在材料表面形成一层固体渗硫层,微观检测渗硫层形貌与成分,并在端面摩擦磨损试验机上进行摩擦学实验,分析其摩擦磨损性能与自润滑机理。结果表明:渗硫层中固体润滑剂的主要成分为FeS,硫化物沿着基体孔道由材料表面向内部扩散,渗硫层的厚度约为15μm;与未硫化材料相比,硫化材料的摩擦因数明显降低,且硫化时间越长,轴承表面渗硫层的减摩性能越好;表面硫化改性后,利用轴承基体多孔含油与表面渗硫层的液固协同润滑作用,其综合摩擦磨损性能比单纯固体润滑或单纯油润滑的减摩性能都要好,边界润滑工况下的抗擦伤、抗咬合性能得到改善。 相似文献
44.
Additive manufacturing (AM) has rapidly changed both large- and small-scale production environments across many industries. By re-envisioning parts from the ground up, not limited to the challenges presented by traditional manufacturing techniques, researchers and engineers have developed new design strategies to solve large-scale materials and design problems worldwide. This is particularly true in the world of alloy design, where new metallic materials have historically been developed through tedious processes and procedures based primarily on casting methodologies. With the onset of directed energy deposition (DED) and powder bed fusion (PBF)-based AM, new alloys can be innovated and evaluated rapidly at a lower cost and considerably shorter lead time than has ever been achieved. This article details the advantages, challenges, applications, and perspectives of alloy design using primarily laser-based AM. It is envisioned that researchers in industry and academia can utilize this work to design new alloys leveraging metallic AM processes for various current and future applications. 相似文献
45.
Sandra Wieland 《粉末冶金学》2020,63(2):149-154
ABSTRACTThe sintering behaviour of LaFe11.0Si1.2Co0.8 powder produced by gas atomisation was examined to provide a basis for the application of powder metallurgical shaping technologies to magnetocaloric La(Fe,Si)13-alloys. The aim was to establish sintering parameters for attaining both high densification and good magnetocaloric properties for the investigated particle sizes <10 µm and <25?µm. Dilatometry measurements and sintering trials were carried out and density, microstructure and entropy change ΔS of the sintered samples were analysed. For the fine particles <10?µm, the lowest investigated sintering temperature 1150°C results in a relative density of 97%, a low α-Fe content and a high ΔS?=??5?J?kg?1?K?1 (ΔH=2?T). For powder <25?µm, a two-stage process is required to achieve similar properties. 相似文献
46.
文章通过冷压-烧结制备了掺杂EBS润滑剂的粉末冶金铝合金,比较了单/多温段脱脂工艺优劣,发现多温段脱脂优于单温段脱脂,脱脂更彻底,但由于气体流量不能无限大,导致气氛脱脂得到的样品碳含量无法达到碳剩余理论值0.02%。研究了真空脱脂和空气负压脱脂机制,真空脱脂可使得EBS热分解的气态有机物和灰分从压坯表面逸出,并被及时带出炉外,最终合金碳含量接近碳剩余理论值0.02%;空气负压脱脂可使得残余碳被氧化逸出,脱碳更彻底,使样品碳含量低于碳剩余理论值。研究了脱脂工艺对合金力学性能的影响,真空脱脂合金力学性能优于气氛脱脂,相对密度最大为97.86%,拉伸强度最大为218.06MPa,接近未添加润滑剂合金的力学性能;空气负压脱脂虽然可使碳含量更低,但因脱脂过程中样品暴露在空气中,使得原料粉末也被氧化,导致最终的合金力学性能严重下降。 相似文献
47.
Banu Barutça Levent Köroğlu Erhan Ayas A. Tansu Koparal 《Ceramics International》2018,44(7):8094-8099
The cytotoxicity of monticellite based bioactive ceramic powder, which was synthesized from boron derivative waste has been determined by in vitro assays of MTT, NRU, and JC-1 staining. The toxicity of powder on different mammalian cell lines (3T3-L1, HUVEC, CRL-2120) was evaluated at the concentrations of 10, 100, 200, 400 and 800?µg/mL to justify its potential for biomedical applications. The obtained results showed that monticellite based bioactive ceramic powder possesses not only bioactive feature but also biocompatible characteristic at the concentration range of 10–200?µg/mL. Hence, monticellite based bioactive ceramics have high potential as a bone graft substitute for bone void filling and coating applications. 相似文献
48.
49.
50.