全文获取类型
收费全文 | 5809篇 |
免费 | 138篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 106篇 |
综合类 | 3篇 |
化学工业 | 917篇 |
金属工艺 | 104篇 |
机械仪表 | 109篇 |
建筑科学 | 111篇 |
矿业工程 | 32篇 |
能源动力 | 116篇 |
轻工业 | 368篇 |
水利工程 | 23篇 |
石油天然气 | 8篇 |
无线电 | 1064篇 |
一般工业技术 | 948篇 |
冶金工业 | 1195篇 |
原子能技术 | 51篇 |
自动化技术 | 800篇 |
出版年
2022年 | 45篇 |
2021年 | 65篇 |
2020年 | 44篇 |
2019年 | 42篇 |
2018年 | 73篇 |
2017年 | 56篇 |
2016年 | 70篇 |
2015年 | 60篇 |
2014年 | 117篇 |
2013年 | 399篇 |
2012年 | 203篇 |
2011年 | 240篇 |
2010年 | 178篇 |
2009年 | 209篇 |
2008年 | 251篇 |
2007年 | 213篇 |
2006年 | 196篇 |
2005年 | 173篇 |
2004年 | 158篇 |
2003年 | 170篇 |
2002年 | 127篇 |
2001年 | 139篇 |
2000年 | 119篇 |
1999年 | 158篇 |
1998年 | 370篇 |
1997年 | 257篇 |
1996年 | 198篇 |
1995年 | 143篇 |
1994年 | 134篇 |
1993年 | 123篇 |
1992年 | 81篇 |
1991年 | 87篇 |
1990年 | 72篇 |
1989年 | 56篇 |
1988年 | 63篇 |
1987年 | 35篇 |
1986年 | 42篇 |
1985年 | 41篇 |
1984年 | 43篇 |
1983年 | 50篇 |
1982年 | 52篇 |
1981年 | 45篇 |
1980年 | 42篇 |
1979年 | 39篇 |
1978年 | 29篇 |
1977年 | 62篇 |
1976年 | 56篇 |
1975年 | 40篇 |
1973年 | 26篇 |
1972年 | 30篇 |
排序方式: 共有5955条查询结果,搜索用时 0 毫秒
11.
A Gopal G Li Mandri DL King C Marboe S Homma 《Canadian Metallurgical Quarterly》1994,105(6):1885-1887
Cardiac papillary fibroelastomas are unusual, frond-like growths typically found on cardiac valves, diagnosed incidentally on autopsy or cardiac surgery, but rarely during life. We report a rare case of an aortic valve papillary fibroelastoma detected by transthoracic echocardiography and confirmed by histologic study. 相似文献
12.
13.
Jing-Sin Liu King Yuan Wei-Sung Lin 《Automatic Control, IEEE Transactions on》1989,34(7):767-770
The minimum-fuel control problem is investigated for a class of multiinput affine nonlinear systems whose associated Lie algebra is nilpotent. After preliminary notions and definitions are presented, emphasis is on the solution to the optimal control problem of the Lie algebra generated by certain system vector fields is nilpotent. Consequences of the maximum principle are deduced for such systems 相似文献
14.
15.
16.
17.
D. M. Van Wie D. G. Drewry Jr. D. E. King C. M. Hudson 《Journal of Materials Science》2004,39(19):5915-5924
Hypersonic flight powered by airbreathing engines offers the potential for faster response time at long ranges, and reduced cost for access-to-space. In the present paper the operating environment of typical hypersonic vehicles are discussed, including results for the radiation equilibrium wall temperature of external vehicle surfaces and the flow properties through three sample engines spanning the range of hydrocarbon-fueled Mach 4-8 flight and hydrogen-fueled flight at speeds up to Mach 17. Flow conditions at several locations through the sample engines were calculated to provide indications of the required operating flow environment. Additional system consideration such a seals, joints, vehicle integration and in-service engineering are addressed. 相似文献
18.
Dynamic bandwidth allocation for multimedia traffic with rate guarantee and fair access in WCDMA systems 总被引:1,自引:0,他引:1
Packet scheduling in a WCDMA system poses a new challenge due to its nature of variable bit rates and location-dependent, time-varying channel conditions. In this work, three new downlink scheduling algorithms for a WCDMA base station are proposed to support multimedia transmissions. Using a credit management and a compensation mechanism, our algorithms provide rate guarantee and fair access to mobile terminals. In particular, we propose to allow a user to simultaneously use multiple OVSF codes in a time-sharing manner, which we call a multicode, shared model. Using multiple codes allows us to compensate those users suffering from bad communication quality or even errors. The proposed schemes can tolerate a multistate link condition (compared to the typically assumed two-state, or good-or-bad, link condition) by adjusting the number of OVSF codes and the spreading factor of each code. Simulation results show that the proposed schemes do achieve higher bandwidth utilization while keeping transmission delay low. 相似文献
19.
Wei-Cheng Lin Tsung-Chien Wu Yi-Hung Tsai Long-Jei Du Ya-Chin King 《Electron Devices, IEEE Transactions on》2005,52(7):1478-1483
Circuit reliability of class-E and class-A power amplifiers is investigated based on a newly developed degradation subcircuit model. Measured degradation characteristics on the fabricated circuits agree well with the simulation predictions. Using this model, we have found that the class-E amplifier degrades faster than a class-A amplifier, due to a much higher stress level during switching. With a drastic decrease of PAE, a shorter lifetime is expected for a class-E amplifier. 相似文献
20.
Digant Gupta Christopher G Lis Sadie L Dahlk Jessica King Pankaj G Vashi James F Grutsch Carolyn A Lammersfeld 《Nutrition journal》2008,7(1):19