全文获取类型
收费全文 | 103271篇 |
免费 | 11923篇 |
国内免费 | 8106篇 |
专业分类
电工技术 | 9016篇 |
技术理论 | 1篇 |
综合类 | 10752篇 |
化学工业 | 13264篇 |
金属工艺 | 6817篇 |
机械仪表 | 7751篇 |
建筑科学 | 8382篇 |
矿业工程 | 4305篇 |
能源动力 | 2758篇 |
轻工业 | 10346篇 |
水利工程 | 3102篇 |
石油天然气 | 4014篇 |
武器工业 | 1653篇 |
无线电 | 11469篇 |
一般工业技术 | 9109篇 |
冶金工业 | 4125篇 |
原子能技术 | 1567篇 |
自动化技术 | 14869篇 |
出版年
2024年 | 338篇 |
2023年 | 1776篇 |
2022年 | 4088篇 |
2021年 | 5533篇 |
2020年 | 3847篇 |
2019年 | 2689篇 |
2018年 | 2948篇 |
2017年 | 3283篇 |
2016年 | 2869篇 |
2015年 | 4655篇 |
2014年 | 5816篇 |
2013年 | 6750篇 |
2012年 | 8511篇 |
2011年 | 8828篇 |
2010年 | 8356篇 |
2009年 | 7783篇 |
2008年 | 7900篇 |
2007年 | 7705篇 |
2006年 | 6652篇 |
2005年 | 5351篇 |
2004年 | 3876篇 |
2003年 | 2899篇 |
2002年 | 2921篇 |
2001年 | 2585篇 |
2000年 | 2064篇 |
1999年 | 1023篇 |
1998年 | 466篇 |
1997年 | 360篇 |
1996年 | 285篇 |
1995年 | 225篇 |
1994年 | 167篇 |
1993年 | 167篇 |
1992年 | 116篇 |
1991年 | 65篇 |
1990年 | 70篇 |
1989年 | 79篇 |
1988年 | 49篇 |
1987年 | 30篇 |
1986年 | 19篇 |
1985年 | 20篇 |
1984年 | 19篇 |
1983年 | 14篇 |
1982年 | 11篇 |
1981年 | 16篇 |
1980年 | 25篇 |
1979年 | 18篇 |
1959年 | 17篇 |
1951年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
121.
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
122.
123.
运用非恒定的动量方程和时均值计算方法,对脉冲液体射流泵时均值基本方程中的流速系数进行了理论研究,推导出了喉管和喉管进口段流速系数φ2和φ5的计算式。通过与恒定射流的流速系数计算式对比,阐明了脉冲频率是影响φ2和φ5的主要因素,沟通了脉冲射流与恒定射流流速系数之间的关系。 相似文献
124.
125.
三级配混凝土输送泵在鱼塘水电站混凝土施工中的应用 总被引:1,自引:0,他引:1
鱼塘水电站溢洪道混凝土共计14.9万m3,由于受不良地质和洪水冲毁围堰等因素影响致使开挖结束时工期严重滞后,而整个电站安全度汛又迫在眉睫,故必须寻求加快溢洪道混凝土浇筑速度的办法。为此,采用国内首批HBT120A三级配混凝土输送泵作为混凝土主要的入仓手段,使施工进度明显加快,弥补了原已滞后的工期,保证了鱼塘水电站溢洪道工程安全度汛目标的实现,并为2005年9月底水库下闸蓄水目标的实现奠定了坚实的基础。本文主要介绍HBT120A三级配混凝土输送泵在该工程施工中的应用。 相似文献
126.
127.
本文讨论一个PCI总线主控制器IP核的设计与验证,描述了该IP核的控制通路和数据通路设计、电路的功能仿真、综合以及验证等过程。结果表明,该IP核在功能和时序上符合PCI技术规范2.2版本,达到了预定的目标。 相似文献
128.
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
129.
130.
在分析了双极型晶体管和场效应晶体管各自的特点和不足后,介绍了一种既具有双极型晶体管较大电流容量和功率输出,又具有场效应晶体管高输入阻抗的电子器件——双极MOS场效应晶体管(BJMOSFET),同时指出体硅BJMOSFET的阳极扩散区与衬底之间存在较大的漏电流,可产生较大的寄生效应。提出了一种新型固体电子器件——基于SOI的BJMOSFET,分析了其工作原理j与体硅BJMOSFET比较,由于SOI技术完整的介质隔离避免了体硅器件中存在的大部分寄生效应,使基于SOI的BJMOSFET在体效应、热载流子效应、寄生电容、短沟道效应和闩锁效应等方面具有更优良的特性。 相似文献