全文获取类型
收费全文 | 53268篇 |
免费 | 5572篇 |
国内免费 | 3904篇 |
专业分类
电工技术 | 4232篇 |
综合类 | 5147篇 |
化学工业 | 6672篇 |
金属工艺 | 4071篇 |
机械仪表 | 3793篇 |
建筑科学 | 4236篇 |
矿业工程 | 2034篇 |
能源动力 | 1242篇 |
轻工业 | 5253篇 |
水利工程 | 1837篇 |
石油天然气 | 2414篇 |
武器工业 | 682篇 |
无线电 | 5445篇 |
一般工业技术 | 5232篇 |
冶金工业 | 2341篇 |
原子能技术 | 869篇 |
自动化技术 | 7244篇 |
出版年
2024年 | 258篇 |
2023年 | 820篇 |
2022年 | 1909篇 |
2021年 | 2457篇 |
2020年 | 1819篇 |
2019年 | 1349篇 |
2018年 | 1393篇 |
2017年 | 1688篇 |
2016年 | 1359篇 |
2015年 | 2293篇 |
2014年 | 2952篇 |
2013年 | 3429篇 |
2012年 | 4129篇 |
2011年 | 4224篇 |
2010年 | 4090篇 |
2009年 | 3896篇 |
2008年 | 3951篇 |
2007年 | 3883篇 |
2006年 | 3482篇 |
2005年 | 2993篇 |
2004年 | 2109篇 |
2003年 | 1461篇 |
2002年 | 1467篇 |
2001年 | 1321篇 |
2000年 | 1100篇 |
1999年 | 637篇 |
1998年 | 452篇 |
1997年 | 357篇 |
1996年 | 305篇 |
1995年 | 266篇 |
1994年 | 211篇 |
1993年 | 137篇 |
1992年 | 116篇 |
1991年 | 86篇 |
1990年 | 74篇 |
1989年 | 72篇 |
1988年 | 46篇 |
1987年 | 29篇 |
1986年 | 22篇 |
1985年 | 17篇 |
1984年 | 12篇 |
1983年 | 10篇 |
1982年 | 12篇 |
1981年 | 17篇 |
1980年 | 16篇 |
1979年 | 7篇 |
1976年 | 1篇 |
1959年 | 5篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
63.
64.
65.
66.
在概括了自蔓延高温合成陶瓷内衬钢管的制备原理基础上,从降低陶瓷层孔隙率,减少陶瓷层裂纹和提高陶瓷层结合强度等方面,论述了提高自蔓延高温合成陶瓷内衬钢管性能的措施,对自蔓延高温合成陶瓷内衬钢管的应用现状及展望进行了评述。 相似文献
67.
In the present paper, the reversible effects between energy-absorbing and energy-reflecting states of chameleon-type building coatings were studied through demonstration of the layers’ properties using infrared thermal imaging of the layers when exposed to a sunlamp or temperature measurements of the layers during exposure to sunlight at different ambient temperatures. The reversible transforming mechanism between the energy-absorbing and energy-reflecting states of the chameleon-type building coatings was investigated with IR, Raman and 1H NMR spectroscopy. The infrared thermal image results showed that when reversibly thermochromic pigments were added to normal white building coatings, the chameleon-type building coatings could absorb energy from the sunlamp below a switching temperature of about 18°C. Absorption of energy from the sunlamp stopped automatically above the switching temperature. The results from exposure to solar radiation showed that when the temperature was below the switching temperature, the chameleon-type building coating could absorb almost the same amount of solar energy as an ordinary coloured coating, and when the temperature was above the switching temperature, the chameleon-type building coating could reflect more solar energy than the ordinary coloured coating. The above results showed that chameleon-type building coatings could contribute to a thermally comfortable building environment. The IR spectroscopy results showed that when the environmental temperature was below the switching temperature of 18°C, the lactone ring of the thermochromic pigment molecule would open and the band of C=O would almost disappear. Raman spectra indicated that the band of C–O in
would move to the high wave number range. From 1H NMR spectra, it could be found that there was some action between the hydrogen of the hydroxyl and the structure of
. During the lactone ring opening, the electron in the non-bond orbital would transit to the higher orbital and it could elongate the conjugated bridge, which would produce visible absorption and hence produce an energy-absorbing effect. However, when the environmental temperature was above the switching temperature of 18°C, the lactone ring in the molecule of the thermochromic pigment would close, the transited electron would transit back to the original orbital, hence the visible absorption would disappear, which would make the coating have an energy-reflecting effect. 相似文献
68.
文章研究了三水草酸铀酰(UO_2C_2O_4·3H_2O)在兆瓦脉冲二氧化碳激光辐照下的红外激光化学反应,它与草酸铀酰的热分解反应不同,反应产物是二氧化铀和二氧化碳。反应的量子效率随激光波长不同而变化。 相似文献
69.
70.
介绍了古洞口工程泄洪洞工作弧门在特定地形下采用固定卷扬式启闭机和汽车吊配合闸室的预埋件进行闸门安装的施工工艺。对闸门的吊装、调整及焊接工艺的具体措施作了详细分析,解决了该工作弧门在洞内安装的关键施工技术问题。 相似文献