全文获取类型
收费全文 | 272943篇 |
免费 | 29966篇 |
国内免费 | 20708篇 |
专业分类
电工技术 | 23917篇 |
技术理论 | 6篇 |
综合类 | 26148篇 |
化学工业 | 36512篇 |
金属工艺 | 18273篇 |
机械仪表 | 18496篇 |
建筑科学 | 22643篇 |
矿业工程 | 9588篇 |
能源动力 | 7955篇 |
轻工业 | 24580篇 |
水利工程 | 8431篇 |
石油天然气 | 10655篇 |
武器工业 | 3496篇 |
无线电 | 30918篇 |
一般工业技术 | 25844篇 |
冶金工业 | 10422篇 |
原子能技术 | 4410篇 |
自动化技术 | 41323篇 |
出版年
2024年 | 1251篇 |
2023年 | 4015篇 |
2022年 | 8789篇 |
2021年 | 12078篇 |
2020年 | 8733篇 |
2019年 | 6982篇 |
2018年 | 7337篇 |
2017年 | 8361篇 |
2016年 | 7429篇 |
2015年 | 11530篇 |
2014年 | 14535篇 |
2013年 | 17073篇 |
2012年 | 20875篇 |
2011年 | 22411篇 |
2010年 | 21046篇 |
2009年 | 20545篇 |
2008年 | 20774篇 |
2007年 | 20231篇 |
2006年 | 18338篇 |
2005年 | 14844篇 |
2004年 | 11248篇 |
2003年 | 8901篇 |
2002年 | 9329篇 |
2001年 | 8256篇 |
2000年 | 5880篇 |
1999年 | 3400篇 |
1998年 | 1788篇 |
1997年 | 1484篇 |
1996年 | 1302篇 |
1995年 | 1066篇 |
1994年 | 843篇 |
1993年 | 653篇 |
1992年 | 508篇 |
1991年 | 363篇 |
1990年 | 289篇 |
1989年 | 272篇 |
1988年 | 185篇 |
1987年 | 121篇 |
1986年 | 116篇 |
1985年 | 61篇 |
1984年 | 52篇 |
1983年 | 46篇 |
1982年 | 37篇 |
1981年 | 37篇 |
1980年 | 57篇 |
1979年 | 48篇 |
1977年 | 8篇 |
1976年 | 3篇 |
1959年 | 44篇 |
1951年 | 33篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
142.
Frequency Insertion Strategy for Channel Assignment Problem 总被引:1,自引:0,他引:1
This paper presents a new heuristic method for quickly finding a good feasible solution to the channel assignment problem
(CAP). Like many other greedy-type heuristics for CAP, the proposed method also assigns a frequency to a call, one at a time.
Hence, the method requires computational time that increases only linear to the number of calls. However, what distinguishes
the method from others is that it starts with a narrow enough frequency band so as to provoke violations of constraints that
we need to comply with in order to avoid radio interference. Each violation is then resolved by inserting frequencies at the
most appropriate positions so that the band of frequencies expands minimally. An extensive computational experiment using
a set of randomly generated problems as well as the Philadelphia benchmark instances shows that the proposed method perform
statistically better than existing methods of its kind and even yields optimum solutions to most of Philadelphia benchmark
instances among which two cases are reported for the first time ever, in this paper.
Won-Young Shin was born in Busan, Korea in 1978. He received B.S. in industrial engineering from Pohang University of Science and Technology
(POSTECH) in 2001 and M.S in operation research and applied statistics from POSTECH in 2003. Since 2003 he has been a researcher
of Agency for Defense Development (ADD) in Korea. He is interested in optimization of communication system and applied statistics.
Soo Y. Chang is an associate professor in the Department of Industrial Engineering at Pohang University of Science and Technology (POSTECH),
Pohang, Korea. He teaches linear programming, discrete optimization, network flows and operations research courses. His research
interests include mathematical programming and scheduling. He has published in several journals including Discrete Applied
Mathematics, Computers and Mathematics with Application, IIE Transactions, International Journal of Production Research, and
so on. He is a member of Korean IIE, and ORMSS.
Jaewook Lee is an assistant professor in the Department of Industrial Engineering at Pohang University of Science and Technology (POSTECH),
Pohang, Korea. He received the B.S. degree in mathematics with honors from Seoul National University, and the Ph.D. degree
from Cornell University in applied mathematics in 1993 and 1999, respectively. He is currently an assistant professor in the
department of industrial engineering at the Pohang University of Science and Technology (POSTECH). His research interests
include nonlinear systems, neural networks, nonlinear optimization, and their applications to data mining and financial engineering.
Chi-Hyuck Jun was born in Seoul, Korea in 1954. He received B.S. in mineral and petroleum engineering from Seoul National University in
1977, M.S. in industrial engineering from Korea Advanced Institute of Science and Technology in 1979 and Ph.D. in operations
research from University of California, Berkeley, in 1986. Since 1987 he has been with the department of industrial engineering,
Pohang University of Science and Technology (POSTECH) and he is now a professor and the department head. He is interested
in performance analysis of communication and production systems. He has published in several journals including IIE Transactions,
IEEE Transactions, Queueing Systems and Chemometrics and Intelligent Laboratory Systems. He is a member of IEEE, INFORMS and
ASQ. 相似文献
143.
当前脉冲发生器里的脉冲形成器件,大部分是用火花气隙(spark gap)和高压电子开关(high voltageswitch).采用火花气隙充当脉冲形成器件有很多弊病:(1)火花气隙在低于1kV时,在机械和电气上不稳定,所以对低于2kV的试验电压要通过分压器来得到. 相似文献
144.
145.
Ye Wan Jun Tan Guangling Song Chuanwei Yan 《Metallurgical and Materials Transactions A》2006,37(7):2313-2316
The focused ion beam technique was employed to investigate the atmospheric corrosion morphology of AZ91D. It was found that
the α matrix of the alloy was preferentially corroded in the areas adjacent to intermetallic phases. The most interesting
finding was that the corrosion products in corrosion cavities were pelletlike, which has never been reported before. 相似文献
146.
Providing reliable group communication is an ever recurring topic in distributed settings. In mobile ad hoc networks, this problem is even more significant since all nodes act as peers, while it becomes more challenging due to highly dynamic and unpredictable topology changes. In order to overcome these difficulties, we deviate from the conventional point of view, i.e., we "fight fire with fire," by exploiting the nondeterministic nature of ad hoc networks. Inspired by the principles of gossip mechanisms and probabilistic quorum systems, we present in this paper PILOT (probabilistic lightweight group communication system) for ad hoc networks, a two-layer system consisting of a set of protocols for reliable multicasting and data sharing in mobile ad hoc networks. The performance of PILOT is predictable and controllable in terms of both reliability (fault tolerance) and efficiency (overhead). We present an analysis of PILOT's performance, which is used to fine-tune protocol parameters to obtain the desired trade off between reliability and efficiency. We confirm the predictability and tunability of PILOT through simulations with ns-2. 相似文献
147.
Al2O3陶瓷激光铣削试验研究 总被引:9,自引:1,他引:8
采用Nd∶YAG脉冲激光器对Al2 O3陶瓷进行铣削加工试验。系统研究了工艺参数对铣削量和铣削面质量的影响规律 ,并利用优化的铣削工艺对Al2 O3陶瓷进行多种形状的铣削加工。 相似文献
148.
本文探讨了系统级简化形式的电磁兼容性预测分析方法,该方法对于只有几对发-收干扰对的系统EMI的预测分析简洁有效,它避免了大系统间繁复的建模与大量的数据采集及其计算工作,从而对于只考虑其结果的系统间的EMC预测分析提高了效率。 相似文献
149.
概述了Windows2000即插即用系统组成及其实现过程,结合实例介绍了Windows2000设备驱动程序如何支持用户即插即用的功能。 相似文献
150.