全文获取类型
收费全文 | 25112篇 |
免费 | 3516篇 |
国内免费 | 2517篇 |
专业分类
电工技术 | 1381篇 |
技术理论 | 2篇 |
综合类 | 2815篇 |
化学工业 | 647篇 |
金属工艺 | 463篇 |
机械仪表 | 606篇 |
建筑科学 | 894篇 |
矿业工程 | 314篇 |
能源动力 | 1018篇 |
轻工业 | 144篇 |
水利工程 | 5495篇 |
石油天然气 | 634篇 |
武器工业 | 140篇 |
无线电 | 7281篇 |
一般工业技术 | 966篇 |
冶金工业 | 392篇 |
原子能技术 | 317篇 |
自动化技术 | 7636篇 |
出版年
2024年 | 125篇 |
2023年 | 382篇 |
2022年 | 670篇 |
2021年 | 786篇 |
2020年 | 818篇 |
2019年 | 689篇 |
2018年 | 704篇 |
2017年 | 959篇 |
2016年 | 965篇 |
2015年 | 1201篇 |
2014年 | 1673篇 |
2013年 | 1701篇 |
2012年 | 2112篇 |
2011年 | 2143篇 |
2010年 | 1701篇 |
2009年 | 1699篇 |
2008年 | 1696篇 |
2007年 | 1921篇 |
2006年 | 1625篇 |
2005年 | 1452篇 |
2004年 | 1209篇 |
2003年 | 990篇 |
2002年 | 857篇 |
2001年 | 694篇 |
2000年 | 498篇 |
1999年 | 382篇 |
1998年 | 300篇 |
1997年 | 247篇 |
1996年 | 199篇 |
1995年 | 174篇 |
1994年 | 163篇 |
1993年 | 107篇 |
1992年 | 86篇 |
1991年 | 42篇 |
1990年 | 38篇 |
1989年 | 33篇 |
1988年 | 21篇 |
1987年 | 21篇 |
1986年 | 13篇 |
1985年 | 12篇 |
1984年 | 12篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 5篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1959年 | 8篇 |
1958年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Koji Yamada Noboru Miura Chihiro Hamaguchi Norihiko Kamata 《Solid-state electronics》1989,32(12):1113-1117
Hot carrier magnetophonon resonances of n-type Si, short channel InP and p-type InSb were investigated in pulsed high magnetic fields up to 40 T. Using a recently developed high resolution technique in pulsed high fields, many new features of the hot carrier-phonon interactions in high magnetic fields were found. 相似文献
82.
Costas Chaikalis 《Wireless Personal Communications》2007,41(1):77-97
Reconfiguration concept represents reconfigurable functionalities of the radio interface for mobile radio systems. Particularly
for the physical layer, some possible reconfigurable architectures can be identified. We focus on outer interleaving for turbo
codes, which can improve their performance in flat Rayleigh fading environment. The larger the number of columns in the outer
interleaver, the better is the performance, but with the penalty of more complexity and delay. Furthermore, an incorrect choice
of the number of columns can increase the bit and frame error rates. Therefore, it would be advantageous to reconfigure the
outer interleaver in different operating environments with the optimum number of columns. Using two different data frame lengths,
in this contribution simulation results are presented for the four possible outer block interleaver configurations specified
for the 3GPP mobile standard in the case of flat Rayleigh fading channel. It is shown that different operating environments
require an optimum number of columns in terms of bit error rate and frame error rate performance. Finally, frame fade duration
is considered and the effect of the product of the Doppler frequency with the frame duration on the performance for the four
different 3GPP outer block interleaver configurations is discussed.
Costas Chaikalis was born in Athens, Greece, on March 7, 1973. He received the B.Sc. degree in electrical engineering in 1995 from Technological
Educational Institute of Lamia, Greece. He also received the M.Sc. and Ph.D. degrees from Department of Electronics and Telecommunications,
University of Bradford, Bradford, UK in 1999 and 2003, respectively. During his doctoral studies he worked as a Research Assistant
for Mobile Virtual Center of Excellence (Mobile VCE), Terminals Group, UK. Since 2003, he is a lecturer in the Department
of Electrical Engineering, Technological Educational Institute of Lamia, Greece. His research interests are in all areas of
mobile communications but especially in forward error correction coding, reconfigurable (software radio) architectures, cross
layer architectures and DSP applications. 相似文献
83.
Huayi Wu Xiaohua Jia Yanxiang He Chuanhe Huang 《International Journal of Communication Systems》2005,18(9):803-816
This paper investigates the issues of QoS routing in CDMA/TDMA ad hoc networks. Since the available bandwidth is very limited in ad hoc networks, a QoS request between two nodes will be blocked if there does not exist a path that can meet the QoS requirements, even though there is enough free bandwidth in the whole system. In this paper, we propose a new scheme of using multiple paths between two nodes as the route for a QoS call. The aggregate bandwidth of the multiple paths can meet the bandwidth requirement of the call and the delays of these paths are within the required bound of the call. We also propose three strategies by which to choose a set of paths as the route, namely, shortest path first (SPF), largest bandwidth first (LBF), and largest hop‐bandwidth first (LHBF). Extensive simulations have been conducted to evaluate the performance of the three strategies in comparison with a traditional single path routing algorithm. The simulation results show that the proposed multiple paths routing scheme significantly reduces the system blocking rates in various network environments, especially when the network load is heavy. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
84.
85.
指出了国有粮食企业存在的主要问题,提出了在市场竞争中发挥国有粮食企业主渠道作用的基本对策。 相似文献
86.
简要介绍了哈锅300MW机组高压加热器发展概况及给水入口管端、过热蒸气冷却段出口部、疏水冷却段入口部、上级疏水入口等部件的结构特点。 相似文献
87.
洋葱路由技术在公网上提供双向、实时的匿名通信,其面向连接和严格的源路由方式导致效率低、扩展性差。利用分布式的概念,采用分段连接技术思想提出了一种安全、高效的分布式洋葱路由机制(DORS),给出了DORS路由实现算法,并从方案实现效率、安全性方面对DORS进行了分析。分析结果表明DORS具有良好的扩展性、鲁棒性、简单性和有效性。 相似文献
88.
KaziTakpaya 《电子科学学刊(英文版)》2003,20(6):439-445
An increasing demand for high data rate transmission and protection over bandlimited channels with severe inter-symbol interference has resulted in a flurry of activity to improve channel equalization. In conjunction with equalization, channel coding-decoding can be employed to improve system performance. In this letter, the performance of the three stageturbo-equalization-decoding employing log maximum a posteriori probability is experimentally evaluated by a fading simulator. The BER is evaluated using various information sequence and interleaver sizes taking into account that the communication medium is a noisy inter symbol interference channel. 相似文献
89.
90.