全文获取类型
收费全文 | 264907篇 |
免费 | 3388篇 |
国内免费 | 934篇 |
专业分类
电工技术 | 5511篇 |
综合类 | 1209篇 |
化学工业 | 39074篇 |
金属工艺 | 10366篇 |
机械仪表 | 8049篇 |
建筑科学 | 6528篇 |
矿业工程 | 1683篇 |
能源动力 | 5622篇 |
轻工业 | 17713篇 |
水利工程 | 2514篇 |
石油天然气 | 4297篇 |
武器工业 | 20篇 |
无线电 | 34976篇 |
一般工业技术 | 48708篇 |
冶金工业 | 54900篇 |
原子能技术 | 4224篇 |
自动化技术 | 23835篇 |
出版年
2022年 | 4169篇 |
2021年 | 5378篇 |
2020年 | 4055篇 |
2019年 | 5105篇 |
2018年 | 3605篇 |
2017年 | 3152篇 |
2016年 | 2981篇 |
2015年 | 2194篇 |
2014年 | 3493篇 |
2013年 | 10140篇 |
2012年 | 5808篇 |
2011年 | 8664篇 |
2010年 | 6940篇 |
2009年 | 7980篇 |
2008年 | 7793篇 |
2007年 | 7793篇 |
2006年 | 7240篇 |
2005年 | 6947篇 |
2004年 | 7893篇 |
2003年 | 7566篇 |
2002年 | 7465篇 |
2001年 | 7305篇 |
2000年 | 6294篇 |
1999年 | 6649篇 |
1998年 | 16732篇 |
1997年 | 11317篇 |
1996年 | 8818篇 |
1995年 | 6603篇 |
1994年 | 5969篇 |
1993年 | 5820篇 |
1992年 | 4184篇 |
1991年 | 3801篇 |
1990年 | 3875篇 |
1989年 | 3778篇 |
1988年 | 3417篇 |
1987年 | 2832篇 |
1986年 | 2952篇 |
1985年 | 3302篇 |
1984年 | 2935篇 |
1983年 | 2703篇 |
1982年 | 2480篇 |
1981年 | 2509篇 |
1980年 | 2196篇 |
1979年 | 2111篇 |
1978年 | 2155篇 |
1977年 | 2494篇 |
1976年 | 3088篇 |
1975年 | 1857篇 |
1974年 | 1736篇 |
1973年 | 1617篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Multimedia Tools and Applications - Remote Sensing categorical signature classification has gained significant implications on spatial resolution image analysis due to differences in the... 相似文献
2.
Zienko S. I. Zhbanova V. L. 《Journal of Communications Technology and Electronics》2022,67(4):395-402
Journal of Communications Technology and Electronics - A quantitative comparison of the spectral characteristics of the human visual system and matrix photodetectors is carried out. Criteria for a... 相似文献
3.
4.
Xiao Zhu Chen Yanxun Jiang Hongbo Hu Zhenzhen Lui John C. S. Min Geyong Dustdar Schahram 《Wireless Networks》2022,28(7):3305-3322
Wireless Networks - Unmanned aerial vehicles (UAV) have been widely used in various fields because of their high mobility and portability. At the same time, due to the rapid development of... 相似文献
5.
6.
Journal of Signal Processing Systems - 相似文献
7.
Can Ercan S. Esra Safran Artuğ Türkmenoğlu Uğur Karabakal 《Journal of surfactants and detergents》2021,24(1):139-147
Garzan oil field is located at the south east of Turkey. It is a mature oil field and the reservoir is fractured carbonate reservoir. After producing about 1% original oil in place (OOIP) reservoir pressure started to decline. Waterflooding was started in order to support reservoir pressure and also to enhance oil production in 1960. Waterflooding improved the oil recovery but after years of flooding water breakthrough at the production wells was observed. This increased the water/oil ratio at the production wells. In order to enhance oil recovery again different techniques were investigated. Chemical enhanced oil recovery (EOR) methods are gaining attention all over the world for oil recovery. Surfactant injection is an effective way for interfacial tension (IFT) reduction and wettability reversal. In this study, 31 different types of chemicals were studied to specify the effects on oil production. This paper presents solubility of surfactants in brine, IFT and contact angle measurements, imbibition tests, and lastly core flooding experiments. Most of the chemicals were incompatible with Garzan formation water, which has high divalent ion concentration. In this case, the usage of 2-propanol as co-surfactant yielded successful results for stability of the selected chemical solutions. The results of the wettability test indicated that both tested cationic and anionic surfactants altered the wettability of the carbonate rock from oil-wet to intermediate-wet. The maximum oil recovery by imbibition test was reached when core was exposed 1-ethly ionic liquid after imbibition in formation water. Also, after core flooding test, it is concluded that considerable amount of oil can be recovered from Garzan reservoir by waterflooding alone if adverse effects of natural fractures could be eliminated. 相似文献
8.
Jincheng Yu Yabin Chang Ewa Jakubczyk Bing Wang Feridoon Azough Robert Dorey Robert Freer 《Journal of the European Ceramic Society》2021,41(9):4859-4869
Ca3Co4O9 is a promising p-type thermoelectric oxide material having intrinsically low thermal conductivity. With low cost and opportunities for automatic large scale production, thick film technologies offer considerable potential for a new generation of micro-sized thermoelectric coolers or generators. Here, based on the chemical composition optimized by traditional solid state reaction for bulk samples, we present a viable approach to modulating the electrical transport properties of screen-printed calcium cobaltite thick films through control of the microstructural evolution by optimized heat-treatment. XRD and TEM analysis confirmed the formation of high-quality calcium cobaltite grains. By creating 2.0 at% cobalt deficiency in Ca2.7Bi0.3Co4O9+δ, the pressureless sintered ceramics reached the highest power factor of 98.0 μWm?1 K-2 at 823 K, through enhancement of electrical conductivity by reduction of poorly conducting secondary phases. Subsequently, textured thick films of Ca2.7Bi0.3Co3.92O9+δ were efficiently tailored by controlling the sintering temperature and holding time. Optimized Ca2.7Bi0.3Co3.92O9+δ thick films sintered at 1203 K for 8 h exhibited the maximum power factor of 55.5 μWm?1 K-2 at 673 K through microstructure control. 相似文献
9.
Knaust Thiemo Felnhofer Anna Kothgassner Oswald D. Hllmer Helge Gorzka Robert-Jacek Schulz Holger 《Virtual Reality》2022,26(3):925-938
Virtual Reality - It is generally accepted that natural environments reduce stress and improve mood. Since access to natural environments is sometimes limited, virtual natural environments,... 相似文献
10.
Multimedia Tools and Applications - Mammograms are the images used by radiologists to diagnose breast cancer. Breast cancer is one of the most common cancers in women. The early detection of breast... 相似文献