全文获取类型
收费全文 | 55376篇 |
免费 | 5473篇 |
国内免费 | 4476篇 |
专业分类
电工技术 | 4539篇 |
技术理论 | 3篇 |
综合类 | 7779篇 |
化学工业 | 2505篇 |
金属工艺 | 1621篇 |
机械仪表 | 4981篇 |
建筑科学 | 3428篇 |
矿业工程 | 1195篇 |
能源动力 | 1365篇 |
轻工业 | 2882篇 |
水利工程 | 1402篇 |
石油天然气 | 1182篇 |
武器工业 | 643篇 |
无线电 | 6471篇 |
一般工业技术 | 4423篇 |
冶金工业 | 1355篇 |
原子能技术 | 775篇 |
自动化技术 | 18776篇 |
出版年
2024年 | 193篇 |
2023年 | 619篇 |
2022年 | 1091篇 |
2021年 | 1221篇 |
2020年 | 1306篇 |
2019年 | 1191篇 |
2018年 | 1224篇 |
2017年 | 1506篇 |
2016年 | 1666篇 |
2015年 | 1806篇 |
2014年 | 2876篇 |
2013年 | 3219篇 |
2012年 | 3695篇 |
2011年 | 4184篇 |
2010年 | 3231篇 |
2009年 | 3363篇 |
2008年 | 3449篇 |
2007年 | 4163篇 |
2006年 | 3844篇 |
2005年 | 3476篇 |
2004年 | 2858篇 |
2003年 | 2493篇 |
2002年 | 2087篇 |
2001年 | 1674篇 |
2000年 | 1430篇 |
1999年 | 1296篇 |
1998年 | 1045篇 |
1997年 | 877篇 |
1996年 | 784篇 |
1995年 | 700篇 |
1994年 | 566篇 |
1993年 | 420篇 |
1992年 | 359篇 |
1991年 | 282篇 |
1990年 | 261篇 |
1989年 | 225篇 |
1988年 | 164篇 |
1987年 | 93篇 |
1986年 | 53篇 |
1985年 | 59篇 |
1984年 | 51篇 |
1983年 | 44篇 |
1982年 | 40篇 |
1981年 | 23篇 |
1980年 | 24篇 |
1979年 | 21篇 |
1978年 | 20篇 |
1977年 | 15篇 |
1976年 | 7篇 |
1975年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
虚拟演播室是传统视频技术与计算机虚拟现实技术相结合的产物 ,它可以把现场视频与计算机影像等实时、无缝地合成在—起 ,是对传统电视演播室的一次重大变革。主要讨论虚拟演播室的工作原理、功能及其应用 相似文献
42.
43.
论文从映射的角度,将哈希函数分为三类:严格哈希函数、计算哈希函数和实用哈希函数。在此基础上,根据二元域上二次方程x2 x c=0的部分不可解的性质,构造了一种计算哈希函数,它满足单向性和一一对应性,同时具有运算速度快的优点。 相似文献
44.
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
45.
Four methods that solve the Poisson, Helmholtz, and diffusion–convection problems on Cartesian grid by collocation with radial basis functions are presented. Each problem is split into a problem with an inhomogeneous equation and homogeneous boundary conditions, and a problem with a homogeneous equation and inhomogeneous boundary conditions. The former problem is solved by collocation with multiquadrics, whereas the latter problem is solved by collocation with either multiquadrics or fundamental solutions. It is found that methods that make use of fundamental solutions for collocation yield more accurate solutions that are less sensitive to the shape parameter of multiquadrics and node arrangement. Additional collocation appears to improve the quality of solutions. 相似文献
46.
An analysis is made of the characteristic features and problems of the optimal processing of the results of measurements in the case of a random observation function utilizing a nonlinear Kalman filter. A method is proposed for increasing the convergence domain of the filter with additional processing of measurements in the frequency domain. 相似文献
47.
在文献[1]的基础上,提出几个改进的模糊加权平均滤波器。本文的方案不仅同时考虑了相邻像素对中心像素的兼容性以及中心像素对相邻像素的兼容性,而且还考虑到了权系数对局部环境的适应性。实验结果表明,该方法相比文献[1]中的模糊加权平均滤波器以及标准的均值滤波器、中值滤波器在噪声消除与边缘保留方面具有更好的性能。 相似文献
48.
49.
一类Feistel密码的线性分析 总被引:5,自引:0,他引:5
该文提出一种新的求取分组密码线性偏差上界的方法,特别适用于密钥线性作用的Feistel密码.该分析方法的思路是,首先对密码体制线性偏差进行严格的数学描述,分别给出密码线性偏差与轮函数F及S盒的线性偏差的数学关系;然后通过求取线性方程组最小重量解,确定密码线性偏差的上界. 相似文献
50.
文章主要讨论了自动交换光网络(ASON)控制平面的两种不同结构:控制平面在网元外部的结构和控制平面部分集成在网元内部的结构,并对这两种结构进行了比较. 相似文献