全文获取类型
收费全文 | 4221篇 |
免费 | 396篇 |
国内免费 | 205篇 |
专业分类
电工技术 | 159篇 |
综合类 | 266篇 |
化学工业 | 1270篇 |
金属工艺 | 662篇 |
机械仪表 | 266篇 |
建筑科学 | 96篇 |
矿业工程 | 255篇 |
能源动力 | 197篇 |
轻工业 | 163篇 |
水利工程 | 4篇 |
石油天然气 | 55篇 |
武器工业 | 48篇 |
无线电 | 142篇 |
一般工业技术 | 789篇 |
冶金工业 | 285篇 |
原子能技术 | 150篇 |
自动化技术 | 15篇 |
出版年
2024年 | 18篇 |
2023年 | 64篇 |
2022年 | 101篇 |
2021年 | 114篇 |
2020年 | 129篇 |
2019年 | 118篇 |
2018年 | 121篇 |
2017年 | 174篇 |
2016年 | 147篇 |
2015年 | 171篇 |
2014年 | 200篇 |
2013年 | 264篇 |
2012年 | 291篇 |
2011年 | 281篇 |
2010年 | 184篇 |
2009年 | 241篇 |
2008年 | 191篇 |
2007年 | 303篇 |
2006年 | 259篇 |
2005年 | 217篇 |
2004年 | 185篇 |
2003年 | 191篇 |
2002年 | 127篇 |
2001年 | 131篇 |
2000年 | 108篇 |
1999年 | 80篇 |
1998年 | 71篇 |
1997年 | 53篇 |
1996年 | 41篇 |
1995年 | 39篇 |
1994年 | 46篇 |
1993年 | 35篇 |
1992年 | 26篇 |
1991年 | 14篇 |
1990年 | 19篇 |
1989年 | 13篇 |
1988年 | 22篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 8篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1959年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有4822条查询结果,搜索用时 15 毫秒
91.
非金刚石相碳成分对金刚石薄膜晶形的影响 总被引:1,自引:0,他引:1
应用Raman光谱和SEM方法研究了在用热丝CVD方法生长金刚石薄膜中,生长膜中非金刚石相碳成分对金刚石晶粒晶形的影响。还讨论了生长条件如碳源浓度、衬底温度等对生长膜中非金刚石相碳成分的影响 相似文献
92.
93.
94.
将铁水用75FeSi孕育后液淬,终止其溶解过程,在溶解区中出现已经生长石墨相的非金属夹杂物,它们随后又溶回铁水中去.但已经复盖有石墨相的晶核能存在较长的时间孕育剂的作用是提供一个碳的过冷溶液,使位于其中的非金属夹杂物活化成为晶核 相似文献
95.
Jianqiang Zhang 《Corrosion Science》2003,45(2):281-299
Cementite decomposition and coke formation in the metal dusting process of iron were investigated at 700 °C in CO-H2-H2O gas mixtures. The presence of graphite deposited on the surface initiates the decomposition of cementite into iron and graphite. The morphology of the reaction products varies with gas composition. For CO concentrations less than 5 vol%, particles of iron or even closed iron layers have been observed at the cementite/graphite interface. With increasing CO content the amount of iron in the interface decreases. At CO concentrations higher than 30 vol%, iron could not be detected at the interface by optical microscopy. Thermo-gravimetric analysis shows that the rate of carbon take-up increases with increasing CO concentration reaching a maximum at about 60-75 vol%.The morphologies of graphite in the coke layer can be identified as three types: porous graphite clusters with embedded iron-containing particles, compact bulk graphite with a uniform thickness and a columnar layered structure, and filamentous carbon with iron-containing phases at the tip or along its length. For gas mixtures with low CO concentrations, e.g. 5 vol%, porous graphite clusters are the main form of carbon although filamentous carbon can be seen at the early stage of reaction. With increasing CO concentrations to, e.g. 30 vol%, a compact bulk graphite is formed on the top of the surface. Under this compact graphite, there is an inner layer of graphite which is the combination of porous graphite clusters and filaments. These two layers of graphite are clearly distinguishable when CO content reaches more than 75 vol%. In this case, the main form of graphite in the inner layer is filamentous carbon. The compact graphite layer suffers a serious deformation and forms many cracks because of the growth of catalytic filamentous carbon underneath. These filaments grow outside from compact graphite crevices and finally cover the whole surface. The higher the CO content in the gas, the more the tendency of filamentous carbon formation. The interplay between morphologies of carbon formation and metal dusting has been discussed. 相似文献
96.
97.
98.
The pressing bonding of steel plate to QTi3.5-3.5graphite slurry was studied. The bonding conditions were 620℃ for preheating temperature of steel plate, 530℃ for preheating temperature of dies, 50 MPa for pressure and 2 min for pressing time. The relationship between the solid fraction of QTi3.5-3.5graphite slurry and the interracial mechanical property of bonding plate was obtained. The results show that when the solid fraction of QTi3.5-3.5graphite slurry is smaller than 45.8%, the interracial shear strength of bonding plate increases with the increasing of solid fraction. When the solid fraction is larger than 45.8%, the interracial shear strength decreases with the increasing of solid fraction. When the solid fraction is 45.8%, the largest interracial shear strength of bonding plate 127 MPa can be got, and the interface is made up of Fe-Cu solid solution. 相似文献
99.
100.
从国外引进的低液位组合结晶器,内置水套,石墨环镶嵌在结晶器四周内壁上,分上下两级水道。在铸造中,由于水质原因会造成喷水水眼堵塞,人为因素也会造成石墨环损坏,结晶器缺陷会造成铸造缺陷,严重时会生产不合格产品。从生产实践出发,对结晶器故障诊断、排除及日常维护技术进行了研究。 相似文献