全文获取类型
收费全文 | 403011篇 |
免费 | 5350篇 |
国内免费 | 1361篇 |
专业分类
电工技术 | 7566篇 |
综合类 | 316篇 |
化学工业 | 59812篇 |
金属工艺 | 16425篇 |
机械仪表 | 13488篇 |
建筑科学 | 8348篇 |
矿业工程 | 2154篇 |
能源动力 | 11523篇 |
轻工业 | 28454篇 |
水利工程 | 4266篇 |
石油天然气 | 7913篇 |
武器工业 | 17篇 |
无线电 | 49232篇 |
一般工业技术 | 82962篇 |
冶金工业 | 74954篇 |
原子能技术 | 9181篇 |
自动化技术 | 33111篇 |
出版年
2022年 | 2550篇 |
2021年 | 3881篇 |
2020年 | 2940篇 |
2019年 | 3801篇 |
2018年 | 6479篇 |
2017年 | 6474篇 |
2016年 | 6918篇 |
2015年 | 4316篇 |
2014年 | 7132篇 |
2013年 | 20022篇 |
2012年 | 11406篇 |
2011年 | 15260篇 |
2010年 | 12137篇 |
2009年 | 13709篇 |
2008年 | 14052篇 |
2007年 | 13813篇 |
2006年 | 12415篇 |
2005年 | 11114篇 |
2004年 | 10505篇 |
2003年 | 10417篇 |
2002年 | 9825篇 |
2001年 | 9732篇 |
2000年 | 9133篇 |
1999年 | 9522篇 |
1998年 | 24324篇 |
1997年 | 16708篇 |
1996年 | 12797篇 |
1995年 | 9516篇 |
1994年 | 8362篇 |
1993年 | 8379篇 |
1992年 | 6054篇 |
1991年 | 5694篇 |
1990年 | 5679篇 |
1989年 | 5317篇 |
1988年 | 5043篇 |
1987年 | 4420篇 |
1986年 | 4299篇 |
1985年 | 4812篇 |
1984年 | 4421篇 |
1983年 | 3994篇 |
1982年 | 3654篇 |
1981年 | 3730篇 |
1980年 | 3429篇 |
1979年 | 3326篇 |
1978年 | 3334篇 |
1977年 | 3750篇 |
1976年 | 4847篇 |
1975年 | 2850篇 |
1974年 | 2663篇 |
1973年 | 2730篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
982.
983.
This paper reviews our research on the electrophoretic deposition (EPD) of phosphors for the processing of monochromatic and color screens for information displays. Our investigation began with the study of the fundamentals of the EPD process for phosphors. The processing variables which enhance the adhesion strength of phosphor deposits were determined. The optical performance of phosphors deposited by EPD was shown to be not affected by the process itself nor by the conditions which enhance phosphor adhesion. Processes developed to produce high-resolution color screens by combining EPD and photolithography techniques are described. Also, a method to electrophoretically deposit phosphor in a thermo-reversible gel from mixtures of poly(butyl methacrylate) and isopropanol was examined. 相似文献
984.
985.
986.
Effect of anions on the textural and catalytic activity of titania-silica mixed oxide 总被引:1,自引:0,他引:1
An attempt has been made to review and study the effect of anions (phosphate, sulfate and fluoride) on titania-silica samples. A comparative study has been made on structural characteristics and physico-chemical properties between the unmodified and anion modified titania-silica mixed oxides. The stabilisations of phase, porosity and sulphate ion at higher activation temperatures are discussed. The increase and decrease of specific surface area, acid strength and surface acid sites with respect to anions are emphasised. The effect of preparation method and conditions with specific surface area, porosity and surface acid sites are also discussed. The generation of new catalytic active sites and effect of porosity are reported towards esterification of acetic acid and mono-nitration of toluene, respectively. 相似文献
987.
988.
New sulphides of transition metal ions [M+n = Cu+1, Cu+2 and Zn+2] have been synthesised in sunlight. XRD patterns show that these compounds are not MxSy but are mercaptyl, hydroxyl metal sulphides [M(SH)(OH)(H2O)2] which is further ascertained by I.R. spectra showing bands due to T
d-symmetry. ESCA of compound of copper in solid state shows presence of Cu1+ and Cu2+ ion. The presence of hydroxyl, mercaptyl, aqua and S–2 groups has finally been confirmed with TGA, DTA and ESCA. Conductivity and Seebeck coefficient measurements show that compound of copper is p-type semiconductor and compound of zinc is n-type semiconductor. The production of these low cost materials opens an interesting area of research and development for their use in solar cell devices. 相似文献
989.
The hydrogen gas pick-up problem that can occur during Lost Foam Casting was investigated with reduced pressure tests and real castings.The initial hydrogen concentration of the melt and the contact time between melt and polystyrene had a main effect on the hydrogen gas pick-up of Al melt. The hydrogen gas pick-up of Al alloy depended also on pouring temperature and a proper metal front temperature gave the minimum hydrogen pick-up. At a low pouring temperature, the hydrogen went into the melt mainly from entrapped liquid product of polystyrene but at high pouring temperature it was by the gas as well as the liquid product. The mold flask evacuation down to 710 torr decreased the gas porosity down by around 0.4 vol%. The permeability of coating thickness had a great effect because it affects the filling time and the easy removal of liquid polystyrene. 相似文献
990.