全文获取类型
收费全文 | 98275篇 |
免费 | 10308篇 |
国内免费 | 6207篇 |
学科分类
工业技术 | 114790篇 |
出版年
2024年 | 371篇 |
2023年 | 1531篇 |
2022年 | 3088篇 |
2021年 | 4437篇 |
2020年 | 3247篇 |
2019年 | 2524篇 |
2018年 | 2652篇 |
2017年 | 2965篇 |
2016年 | 2909篇 |
2015年 | 4195篇 |
2014年 | 5196篇 |
2013年 | 6145篇 |
2012年 | 7160篇 |
2011年 | 7608篇 |
2010年 | 7207篇 |
2009年 | 6748篇 |
2008年 | 6761篇 |
2007年 | 6362篇 |
2006年 | 5920篇 |
2005年 | 5040篇 |
2004年 | 3681篇 |
2003年 | 2993篇 |
2002年 | 3262篇 |
2001年 | 2777篇 |
2000年 | 2246篇 |
1999年 | 1578篇 |
1998年 | 1102篇 |
1997年 | 923篇 |
1996年 | 833篇 |
1995年 | 725篇 |
1994年 | 616篇 |
1993年 | 475篇 |
1992年 | 348篇 |
1991年 | 271篇 |
1990年 | 202篇 |
1989年 | 167篇 |
1988年 | 135篇 |
1987年 | 83篇 |
1986年 | 64篇 |
1985年 | 41篇 |
1984年 | 31篇 |
1983年 | 17篇 |
1982年 | 27篇 |
1981年 | 33篇 |
1980年 | 29篇 |
1979年 | 19篇 |
1976年 | 8篇 |
1975年 | 8篇 |
1959年 | 12篇 |
1951年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
11.
基于柴油产品质量升级的需求,中国石化大连石油化工研究院(FRIPP)开发了FHIDW加氢改质技术及配套FF-46加氢精制催化剂、FC-14B加氢改质催化剂和FDW-3临氢降凝催化剂.该技术及催化剂级配体系在格尔木炼油厂0.8 Mt·a-1加氢改质装置上的工业应用情况表明,级配催化剂体系对原料适应性强,装置运转平稳,操作灵活性高,催化剂失活速率慢,产品分布合理且质量优异,在降低柴油产品凝点的同时可以明显改善其密度和十六烷值,解决了改造前装置生产重柴油密度偏低的问题,为炼油厂生产符合国V质量标准的柴油提供了技术保障. 相似文献
12.
13.
Yuelong Ma Le Zhang Tianyuan Zhou Bingheng Sun Chen Hou Shunshun Yang Jin Huang Rui Wang Farida A. Selim Zhongying Wang Ming Li Hao Chen Yun Wang 《Journal of the European Ceramic Society》2021,41(4):2834-2846
Ce:Y3Al5O12 transparent ceramics (TCs) with appropriate emission light proportion and high thermal stability are significant to construct white light emitting diode devices with excellent chromaticity parameters. In this work, strategies of controlling crystal-field splitting around Ce3+ ion and doping orange-red emitting ion, were adopted to fabricate Ce:(Y,Tb)3(Al,Mn)5O12 TCs via vacuum sintering technique. Notably, 85.4 % of the room-temperature luminescence intensity of the TC was retained at 150 °C, and the color rendering index was as high as 79.8. Furthermore, a 12 nm red shift and a 16.2 % increase of full width at half maximum were achieved owing to the synergistic effects of Tb3+ and Mn2+ ions. By combining TCs with a 460 nm blue chip, a warm white light with a low correlated color temperature of 4155 K was acquired. Meanwhile, the action mechanism of Tb3+ ion and the energy transfer between Ce3+ and Mn2+ ions were verified in prepared TCs. 相似文献
14.
Wireless Networks - In such mobile platforms as ships and aircraft, the detection and reconnaissance devices are near to the communication facilities. When working at the same time, they will... 相似文献
15.
16.
17.
18.
Chenxu Liu Shuguang Zhang Ruonan Ji Peng Wang Jin Zhang Yu Tian Yonggang Meng Yedong He 《Ceramics International》2019,45(4):4747-4755
Semiconductor particles doped Al2O3 coatings were prepared by cathode plasma electrolytic deposition in Al(NO3)3 electrolyte dispersed with SiC micro- and nano-particles (average particle sizes of 0.5–1.7?µm and 40?nm respectively). The effects of the concentrations and particle sizes of the SiC on the microstructures and tribological performances of the composite coatings were studied. In comparison with the case of dispersing with SiC microparticles, the dispersion of SiC nanoparticles in the coatings was more uniform. When the concentration of SiC nanoparticles was 5?g/L, the surface roughness of the composite coating was reduced by 63%, compared with that of the unmodified coating. Friction results demonstrated that the addition of 5?g/L SiC nanoparticles reduced the friction coefficient from 0.60 to 0.38 and decreased the wear volume under dry friction. The current density and bath voltage were measured to analyze the effects of SiC particles on the deposition process. The results showed that the SiC particles could alter the electrical behavior of the coatings during the deposition process, weaken the bombardment of the plasma, and improve the structures of the coatings. 相似文献
19.
20.