全文获取类型
收费全文 | 705143篇 |
免费 | 15852篇 |
国内免费 | 5920篇 |
专业分类
电工技术 | 16800篇 |
技术理论 | 3篇 |
综合类 | 8039篇 |
化学工业 | 102057篇 |
金属工艺 | 32118篇 |
机械仪表 | 26396篇 |
建筑科学 | 20832篇 |
矿业工程 | 4955篇 |
能源动力 | 17975篇 |
轻工业 | 55739篇 |
水利工程 | 8437篇 |
石油天然气 | 13242篇 |
武器工业 | 737篇 |
无线电 | 79709篇 |
一般工业技术 | 133945篇 |
冶金工业 | 111368篇 |
原子能技术 | 12260篇 |
自动化技术 | 82303篇 |
出版年
2022年 | 4894篇 |
2021年 | 7999篇 |
2020年 | 5816篇 |
2019年 | 6346篇 |
2018年 | 26931篇 |
2017年 | 26566篇 |
2016年 | 21209篇 |
2015年 | 9179篇 |
2014年 | 12981篇 |
2013年 | 28662篇 |
2012年 | 23641篇 |
2011年 | 38270篇 |
2010年 | 32296篇 |
2009年 | 31504篇 |
2008年 | 32356篇 |
2007年 | 33806篇 |
2006年 | 19418篇 |
2005年 | 20749篇 |
2004年 | 18074篇 |
2003年 | 17357篇 |
2002年 | 15693篇 |
2001年 | 14866篇 |
2000年 | 13549篇 |
1999年 | 13661篇 |
1998年 | 33521篇 |
1997年 | 23465篇 |
1996年 | 17925篇 |
1995年 | 13393篇 |
1994年 | 11585篇 |
1993年 | 11195篇 |
1992年 | 8100篇 |
1991年 | 7582篇 |
1990年 | 7348篇 |
1989年 | 7094篇 |
1988年 | 6533篇 |
1987年 | 5808篇 |
1986年 | 5676篇 |
1985年 | 6290篇 |
1984年 | 5919篇 |
1983年 | 5178篇 |
1982年 | 4914篇 |
1981年 | 4978篇 |
1980年 | 4719篇 |
1979年 | 4615篇 |
1978年 | 4409篇 |
1977年 | 5335篇 |
1976年 | 6976篇 |
1975年 | 3797篇 |
1974年 | 3552篇 |
1973年 | 3665篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
3.
4.
采用直流磁控溅射和后退火氧化工艺在p型GaAs单晶衬底上成功制备了n-VO_2/pGaAs异质结,研究了不同退火温度和退火时间对VO_2/GaAs异质结性能的影响,并分析其结晶取向、化学组分、膜层质量以及光电特性。结果表明,在退火时间2 h和退火温度693 K下能得到相变性能最佳的VO_2薄膜,相变前后电阻变化约2个数量级。VO_2/GaAs异质结在308 K、318 K和328 K温度下具有较好的整流特性,对应温度下的阈值跳变电压分别为6.9 V、6.6 V和6.2 V,该结果为基于VO_2相变特性的异质结光电器件的设计与应用提供了可行性。 相似文献
5.
6.
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
7.
Journal of Computer and Systems Sciences International - It is shown that the Lyapunov theorem on the distribution properties of the sum of random variables with different distribution densities... 相似文献
8.
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
9.
Kuznetsov Yu. A. Markov M. A. Kravchenko I. N. Krasikov A. V. Bykova A. D. 《Refractories and Industrial Ceramics》2021,62(4):421-425
Refractories and Industrial Ceramics - The paper introduces a promising technology for utilizing a traditional scheme for implementing a flow-through micro-arc oxidation method to restore localized... 相似文献
10.
Multimedia Tools and Applications - Recently, many concepts in technology has been changed. According to the digital transformation trends, Internet of Things (IoT) represents an interested... 相似文献