全文获取类型
收费全文 | 57189篇 |
免费 | 5726篇 |
国内免费 | 3193篇 |
专业分类
电工技术 | 3957篇 |
技术理论 | 2篇 |
综合类 | 4573篇 |
化学工业 | 8980篇 |
金属工艺 | 3317篇 |
机械仪表 | 3718篇 |
建筑科学 | 4866篇 |
矿业工程 | 1615篇 |
能源动力 | 1591篇 |
轻工业 | 3967篇 |
水利工程 | 1245篇 |
石油天然气 | 2775篇 |
武器工业 | 603篇 |
无线电 | 6801篇 |
一般工业技术 | 6610篇 |
冶金工业 | 2441篇 |
原子能技术 | 658篇 |
自动化技术 | 8389篇 |
出版年
2024年 | 191篇 |
2023年 | 900篇 |
2022年 | 1526篇 |
2021年 | 2429篇 |
2020年 | 1779篇 |
2019年 | 1571篇 |
2018年 | 1725篇 |
2017年 | 1759篇 |
2016年 | 1532篇 |
2015年 | 2329篇 |
2014年 | 2821篇 |
2013年 | 3261篇 |
2012年 | 3773篇 |
2011年 | 4036篇 |
2010年 | 3783篇 |
2009年 | 3629篇 |
2008年 | 3448篇 |
2007年 | 3327篇 |
2006年 | 3331篇 |
2005年 | 2730篇 |
2004年 | 2074篇 |
2003年 | 2175篇 |
2002年 | 2512篇 |
2001年 | 2172篇 |
2000年 | 1454篇 |
1999年 | 1313篇 |
1998年 | 899篇 |
1997年 | 715篇 |
1996年 | 653篇 |
1995年 | 563篇 |
1994年 | 403篇 |
1993年 | 355篇 |
1992年 | 257篇 |
1991年 | 149篇 |
1990年 | 129篇 |
1989年 | 115篇 |
1988年 | 97篇 |
1987年 | 51篇 |
1986年 | 20篇 |
1985年 | 27篇 |
1984年 | 18篇 |
1983年 | 13篇 |
1982年 | 14篇 |
1981年 | 13篇 |
1980年 | 18篇 |
1979年 | 7篇 |
1978年 | 1篇 |
1959年 | 6篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Quality of service (QoS) support for multimedia services in the IEEE 802.11 wireless LAN is an important issue for such WLANs
to become a viable wireless access to the Internet. In this paper, we endeavor to propose a practical scheme to achieve this
goal without changing the channel access mechanism. To this end, a novel call admission and rate control (CARC) scheme is
proposed. The key idea of this scheme is to regulate the arriving traffic of the WLAN such that the network can work at an
optimal point. We first show that the channel busyness ratio is a good indicator of the network status in the sense that it
is easy to obtain and can accurately and timely represent channel utilization. Then we propose two algorithms based on the
channel busyness ratio. The call admission control algorithm is used to regulate the admission of real-time or streaming traffic
and the rate control algorithm to control the transmission rate of best effort traffic. As a result, the real-time or streaming
traffic is supported with statistical QoS guarantees and the best effort traffic can fully utilize the residual channel capacity
left by the real-time and streaming traffic. In addition, the rate control algorithm itself provides a solution that could
be used above the media access mechanism to approach the maximal theoretical channel utilization. A comprehensive simulation
study in ns-2 has verified the performance of our proposed CARC scheme, showing that the original 802.11 DCF protocol can
statically support strict QoS requirements, such as those required by voice over IP or streaming video, and at the same time,
achieve a high channel utilization.
Hongqiang Zhai received the B.E. and M.E. degrees in electrical engineering from Tsinghua University, Beijing, China, in July 1999 and January
2002 respectively. He worked as a research intern in Bell Labs Research China from June 2001 to December 2001, and in Microsoft
Research Asia from January 2002 to July 2002. Currently he is pursuing the PhD degree in the Department of Electrical and
Computer Engineering, University of Florida. He is a student member of IEEE.
Xiang Chen received the B.E. and M.E. degrees in electrical engineering from Shanghai Jiao Tong University, Shanghai, China, in 1997
and 2000, respectively, and the Ph.D. degree in electrical and computer engineering from the University of Florida, Gainesville,
in 2005. He is currently a Senior Research Engineer at Motorola Labs, Arlington Heights, IL. His research interests include
resource management, medium access control, and quality of service (QoS) in wireless networks. He is a Member of Tau Beta
Pi and a student member of IEEE.
Yuguang Fang received a Ph.D degree in Systems and Control Engineering from Case Western Reserve University in January 1994, and a Ph.D
degree in Electrical Engineering from Boston University in May 1997.
From June 1997 to July 1998, he was a Visiting Assistant Professor in Department of Electrical Engineering at the University
of Texas at Dallas. From July 1998 to May 2000, he was an Assistant Professor in the Department of Electrical and Computer
Engineering at New Jersey Institute of Technology. In May 2000, he joined the Department of Electrical and Computer Engineering
at University of Florida where he got the early promotion with tenure in August 2003 and has been an Associate Professor since
then. He has published over one hundred (100) papers in refereed professional journals and conferences. He received the National
Science Foundation Faculty Early Career Award in 2001 and the Office of Naval Research Young Investigator Award in 2002.
He is currently serving as an Editor for many journals including IEEE Transactions on Communications, IEEE Transactions on
Wireless Communications, IEEE Transactions on Mobile Computing, and ACM Wireless Networks. He is also actively participating
in conference organization such as the Program Vice-Chair for IEEE INFOCOM’2005, Program Co-Chair for the Global Internet
and Next Generation Networks Symposium in IEEE Globecom’2004 and the Program Vice Chair for 2000 IEEE Wireless Communications
and Networking Conference (WCNC’2000). 相似文献
82.
83.
84.
介绍了土卡河水电站可研阶段通过方案比选后确定的工程规模(特征水位、装机容量)。为保证2006年底第一台机组发电,根据目前的施工进度,需要采用围堰挡水发电,文章简要介绍了第一台机组发电的运行方式。 相似文献
85.
基于子波域空间相关的多分辨图像滤波方法 总被引:2,自引:1,他引:1
从静态子波变换入手,提出了一种有效的图像滤波算法。通过计算相邻尺度下细节信号的空间相关性来区分噪声和信号,如果子波系数的空间相关性大,则认为此位置的系数含有特征及边缘信息予以保留。实现这种理论的完整方法包括两部分:空间滤波和子波收缩。仿真结果表明这个算法有很好的降噪性能。 相似文献
86.
87.
88.
松辽盆地南部深层火山岩识别及成藏条件分析 总被引:14,自引:0,他引:14
松辽盆地北部徐深1井在营城组火山岩获得油气突破后,在松辽盆地南部长岭断陷针对火山岩部署了长深1井。在长深1井营城组火山岩地层测试获4.6×105m3/d的工业气流,推算无阻流量1.5×106m3/d以上,预示松辽盆地南部深层火山岩气藏是下步勘探开发的主要领域。通过大量的火山岩岩心资料,利用岩石学、矿物学、测井和地震地层学等多学科技术,首次在松辽盆地南部建立了火山岩识别标准,在东南隆起区部署探井1口,在火山岩中见到了较好的气显示,取得很好的效果。 相似文献
89.
金属泡沫材料研究进展 总被引:14,自引:2,他引:12
综述了金属泡沫材料的各种制备方法。液相法制备金属泡沫材料包括气体吹入法、固体发泡剂法和固体—气体共晶凝固法、熔模铸造法、渗流铸造法、喷射沉积法以及粉末加压熔化法等制备方法。采用金属粉末烧结法、浆料发泡法等制备工艺可以从固相制备金属泡沫材料。电沉积法以及气相沉积法可用于制备高孔隙率的金属泡沫材料。最后简要总结了金属泡沫材料的应用。 相似文献
90.
基于GIS的水电工程可视化辅助设计理论与方法 总被引:2,自引:0,他引:2
针对当前水电工程设计领域存在的计算机应用水平还有待于提高,设计过程复杂且不直观等情况,在探讨工程可视化辅助设计(VCAD)基本概念及其理论构成体系的基础上,提出了基于GIS的水电工程可视化辅助设计理论与方法,实现了直观方便的设计建模和设计过程的交互控制,以及设计成果的直观形象表达,从而有助于提高工程设计的效率和质量,也为大型水利水电工程设计提供了一种新的辅助手段. 相似文献