全文获取类型
收费全文 | 3941篇 |
免费 | 631篇 |
国内免费 | 429篇 |
专业分类
电工技术 | 475篇 |
综合类 | 518篇 |
化学工业 | 36篇 |
金属工艺 | 70篇 |
机械仪表 | 314篇 |
建筑科学 | 39篇 |
矿业工程 | 96篇 |
能源动力 | 46篇 |
轻工业 | 17篇 |
水利工程 | 27篇 |
石油天然气 | 32篇 |
武器工业 | 34篇 |
无线电 | 1243篇 |
一般工业技术 | 196篇 |
冶金工业 | 26篇 |
原子能技术 | 8篇 |
自动化技术 | 1824篇 |
出版年
2024年 | 16篇 |
2023年 | 47篇 |
2022年 | 74篇 |
2021年 | 84篇 |
2020年 | 101篇 |
2019年 | 81篇 |
2018年 | 76篇 |
2017年 | 136篇 |
2016年 | 138篇 |
2015年 | 191篇 |
2014年 | 282篇 |
2013年 | 278篇 |
2012年 | 334篇 |
2011年 | 368篇 |
2010年 | 331篇 |
2009年 | 297篇 |
2008年 | 319篇 |
2007年 | 345篇 |
2006年 | 308篇 |
2005年 | 292篇 |
2004年 | 224篇 |
2003年 | 165篇 |
2002年 | 146篇 |
2001年 | 121篇 |
2000年 | 65篇 |
1999年 | 36篇 |
1998年 | 22篇 |
1997年 | 24篇 |
1996年 | 27篇 |
1995年 | 27篇 |
1994年 | 11篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有5001条查询结果,搜索用时 15 毫秒
1.
Jianhuai Dong Zhixuan Dong 《International Journal of Adaptive Control and Signal Processing》2020,34(10):1466-1482
This article studies the optimal filtering and control for wireless networked control systems (WNCSs). In WNCSs, packets may be lost in both control and feedback channels and user datagram protocol is usually used to improve the performance of the real-time control. Relevant literature indicates that the conventional optimal filtering for such a system cannot be applied in practice due to the complex calculation with Gaussian mixtures. This paper proposes a novel scheme to realize the optimal filtering and the linear quadratic Gaussian control for WNCSs, in which the controlled node performs a local estimation and the remote-control node performs the final estimation and control, and a synchronization of two estimators is guaranteed by a communication mechanism. An optimal filtering algorithm is developed, the stability condition of the filtering error covariance is obtained, optimal finite-horizon and infinite-horizon control are derived, and the stability of the closed-loop control system is proved. Numerical simulations show the validity and feasibility of the theoretical results. 相似文献
2.
Kicheon Kim 《ETRI Journal》2006,28(1):31-44
In a packet switching network, congestion is unavoidable and affects the quality of real‐time traffic with such problems as delay and packet loss. Packet fair queuing (PFQ) algorithms are well‐known solutions for quality‐of‐service (QoS) guarantee by packet scheduling. Our approach is different from previous algorithms in that it uses hardware time achieved by sampling a counter triggered by a periodic clock signal. This clock signal can be provided to all the modules of a routing system to get synchronization. In this architecture, a variant of the PFQ algorithm, called digitized delay queuing (DDQ), can be distributed on many line interface modules. We derive the delay bounds in a single processor system and in a distributed architecture. The definition of traffic contribution improves the simplicity of the mathematical models. The effect of different time between modules in a distributed architecture is the key idea for understanding the delay behavior of a routing system. The number of bins required for the DDQ algorithm is also derived to make the system configuration clear. The analytical models developed in this paper form the basis of improvement and application to a combined input and output queuing (CIOQ) router architecture for a higher speed QoS network. 相似文献
3.
4.
The multihop optical network is the most appropriate solution to satisfy the increasing applications of Internet services. This paper extends the regular Kautz graph to one with multiple layers in order to produce more architectural variations. The connectivity between adjacent layers utilizes the systematic connection patterns of a regular Kautz graph. A routing algorithm based on its property is presented. Optical passive star (OPS) couplers are adopted to implement our new topologies. Three scheduling criteria that can solve the contention problem in the intermediate nodes are evaluated and compared in terms of their capability to improve the accessibility. 相似文献
5.
本文重点研究基于包错误率测量的链路自适应算法,分析了包错误率与信道参数的关系,提出了一种有别于固定门限值方案的优化门限值方案。仿真结果表明,优化门限值方案的网络吞吐量要大于固定门限值方案和基于信干比估计的链路自适应算法,最大增幅可达12Mbit/s。在系统引入重传机制后,网络吞吐量将有所损失,但最大不超过1Mbit/s,相比较服务质量的提高是值得的。需指出的是,虽然分析和仿真均以HIPERLAN/2为例,但不失一般性,它们同样适合于WPAN/WLAN等类似系统。 相似文献
6.
传统的多载波调制都是采用对传输信道进行等带宽划分的方式。为了更好地适应信道传输特性,一个很有应用前景的发展方向是采用非等带宽划分信道的多载波调制方式。本文提出了一种利用正交小波包变换实现的非等带宽划分信道的多载波调制方法。理论分析和实验结果表明,这种方法对于提高信道的传输性能有很大的潜力。 相似文献
7.
Didier Lemoine 《Computer Physics Communications》1996,97(3):331-344
A quantum wave packet code for studying nonreactive scattering of closed-shell atoms or diatomic molecules from a rigid surface is described. The time evolution relies on the Chebychev propagator. Up to 5 collider degrees of freedom, 3 in translation and 2 in rotation, are treated in a pseudospectral way with the momentum or finite basis representation as the primary space. Potential matrix elements are efficiently evaluated by means of sequential 1D transformations between momentum and coordinate spaces. Fast Fourier transforms are performed for the translational and azimuthal coordinates whereas a Gauss-Legendre transform is used for the polar coordinate. This pseudospectral strategy minimizes memory requirements because no off-diagonal Hamiltonian matrix elements need to be stored. In addition, a wide variety of physical systems can be studied since no particular functional form is imposed for the interaction potential. 相似文献
8.
探讨了地震数据经小波包变换压缩后对后续处理过程的影响,以及经过某些处理后的数据会对小波包变换压缩产生什么影响等问题。将小波包变换压缩地震数据的结果与快速傅里叶变换压缩地震数据的结果进行了对比,其结果表明:应用小波包变换压缩地震数据,有效信号的损失非常小,压缩比大于快速傅里叶变换的压缩比。在大批量地震数据处理中可以使用小波包变换压缩地震数据。 相似文献
9.
本文针对调制阶数大于4的MPSK和MQAM调制,在重传中采用非均匀星座图和符号比特重新排序,提出了一种改进的ARQ方案。通过对AWGN信道下ARQ方案进行理论分析和数值仿真,表明基于非均匀星座的新方案在信道条件较差时能有效地提高重要比特的可靠性,若重传中结合符号比特重排和分组合并,则可使接收端解调合并后的比特可靠性趋于均匀且总体得到提高,从而有效地减少重传次数,提高系统的吞吐率。由于本文所提方案并不改变调制解调规则和数据分组长度,故容易实现和控制。 相似文献
10.
以ATM实现分组话音通信,需要解决两个基本问题:传输时延和分组丢失。针对这两个基本问题,本文着重讨论了ATM分组话音通信中32kb/sADPCM话音分组丢失的重建技术--于模式匹配的波形替代技术和静默重建技术,分别用以补偿由于网络阻塞造成的分组话音信息丢失而产生的失真和改善重建话音的自然性。 相似文献