全文获取类型
收费全文 | 19988篇 |
免费 | 2655篇 |
国内免费 | 1468篇 |
专业分类
电工技术 | 1633篇 |
技术理论 | 1篇 |
综合类 | 1697篇 |
化学工业 | 2832篇 |
金属工艺 | 1212篇 |
机械仪表 | 1161篇 |
建筑科学 | 1656篇 |
矿业工程 | 494篇 |
能源动力 | 558篇 |
轻工业 | 1754篇 |
水利工程 | 489篇 |
石油天然气 | 940篇 |
武器工业 | 246篇 |
无线电 | 2576篇 |
一般工业技术 | 2732篇 |
冶金工业 | 714篇 |
原子能技术 | 265篇 |
自动化技术 | 3151篇 |
出版年
2024年 | 174篇 |
2023年 | 477篇 |
2022年 | 862篇 |
2021年 | 1022篇 |
2020年 | 816篇 |
2019年 | 675篇 |
2018年 | 716篇 |
2017年 | 766篇 |
2016年 | 713篇 |
2015年 | 935篇 |
2014年 | 1091篇 |
2013年 | 1305篇 |
2012年 | 1412篇 |
2011年 | 1475篇 |
2010年 | 1339篇 |
2009年 | 1222篇 |
2008年 | 1142篇 |
2007年 | 1103篇 |
2006年 | 1084篇 |
2005年 | 804篇 |
2004年 | 596篇 |
2003年 | 607篇 |
2002年 | 773篇 |
2001年 | 691篇 |
2000年 | 431篇 |
1999年 | 421篇 |
1998年 | 262篇 |
1997年 | 236篇 |
1996年 | 201篇 |
1995年 | 164篇 |
1994年 | 128篇 |
1993年 | 123篇 |
1992年 | 107篇 |
1991年 | 58篇 |
1990年 | 47篇 |
1989年 | 32篇 |
1988年 | 21篇 |
1987年 | 20篇 |
1986年 | 16篇 |
1985年 | 10篇 |
1984年 | 9篇 |
1983年 | 10篇 |
1982年 | 5篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1965年 | 1篇 |
1959年 | 2篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
The structure and properties of high density polyethylene (HDPE) functionalized by ultraviolet irradiation at different light intensities in air were studied by electron analysis, FTIR spectroscopy, contact angle with water, differential scanning calorimetry and mechanical properties measurement. The results show that oxygen‐containing groups such as C?O, C—O and C(?O)O were introduced onto the molecular chain of HDPE following irradiation, and the rate and efficiency of HDPE functionalization increased with enhancement of irradiation intensity. After irradiation, the melting temperature, contact angle with water and notched impact strength of HDPE decreased, the degree of crystallinity increased, and their variation amplitude increased with irradiation intensity. Compared with HDPE, the yield strength of HDPE irradiated at lower light intensity (32 W m?2 and 45 W m?2) increases monotonically with irradiation time, and the yield strength of HDPE irradiated at higher light intensity (78 W m?2) increases up to 48 h and then decreased with further increase in irradiation time. The irradiated HDPE behaved as a compatibilizer in HDPE/polycarbonate (PC) blends, and the interface bonding between HDPE and PC was ameliorated. After adding 20 wt% HDPE irradiated at 78 W m?2 irradiation intensity for 24 h to HDPE/PC blends, the tensile yield strength and notched Izod impact strength of the blend were increased from 26.3 MPa and 51 J m?1 to 30.2 MPa and 158 J m?1, respectively. Copyright © 2003 Society of Chemical Industry 相似文献
22.
23.
Supermedia-enhanced Internet-based telerobotics 总被引:4,自引:0,他引:4
Elhajj I. Ning Xi Wai Keung Fung Yun-Hui Liu Hasegawa Y. Fukuda T. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》2003,91(3):396-421
This paper introduces new planning and control methods for supermedia-enhanced real-time telerobotic operations via the Internet. Supermedia is the collection of video, audio, haptic information, temperature, and other sensory feedback. However, when the communication medium used, such as the Internet, introduces random communication time delay, several challenges and difficulties arise. Most importantly, random communication delay causes instability, loss of transparency, and desynchronization in real-time closed-loop telerobotic systems. Due to the complexity and diversity of such systems, the first challenge is to develop a general and efficient modeling and analysis tool. This paper proposes the use of Petri net modeling to capture the concurrency and complexity of Internet-based teleoperation. Combined with the event-based planning and control method, it also provides an efficient analysis and design tool to study the stability, transparency, and synchronization of such systems. In addition, the concepts of event transparency and event synchronization are introduced and analyzed. This modeling and control method has been applied to the design of several supermedia-enhanced Internet-based telerobotic systems, including the bilateral control of mobile robots and mobile manipulators. These systems have been experimentally implemented in three sites test bed consisting of robotic laboratories in the USA, Hong Kong, and Japan. The experimental results have verified the theoretical development and further demonstrated the stability, event transparency, and event synchronization of the systems. 相似文献
24.
25.
26.
27.
28.
29.
堇青石基玻璃陶瓷的制备与展望 总被引:2,自引:0,他引:2
介绍了制备堇青石基玻璃陶瓷的三种方法:熔融法、烧结法和溶胶-凝胶法,综述了玻璃组成、添加剂和成核剂对堇青石基玻璃陶瓷的烧结及性能的影响,并对其未来的发展进行了展望。 相似文献
30.