全文获取类型
收费全文 | 527篇 |
免费 | 38篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 144篇 |
综合类 | 24篇 |
化学工业 | 16篇 |
金属工艺 | 9篇 |
机械仪表 | 38篇 |
建筑科学 | 9篇 |
矿业工程 | 14篇 |
能源动力 | 6篇 |
轻工业 | 10篇 |
水利工程 | 5篇 |
石油天然气 | 1篇 |
武器工业 | 6篇 |
无线电 | 120篇 |
一般工业技术 | 6篇 |
冶金工业 | 9篇 |
原子能技术 | 2篇 |
自动化技术 | 156篇 |
出版年
2023年 | 7篇 |
2022年 | 5篇 |
2021年 | 7篇 |
2020年 | 10篇 |
2019年 | 4篇 |
2018年 | 11篇 |
2017年 | 15篇 |
2016年 | 14篇 |
2015年 | 13篇 |
2014年 | 26篇 |
2013年 | 19篇 |
2012年 | 33篇 |
2011年 | 40篇 |
2010年 | 35篇 |
2009年 | 37篇 |
2008年 | 23篇 |
2007年 | 28篇 |
2006年 | 38篇 |
2005年 | 31篇 |
2004年 | 32篇 |
2003年 | 31篇 |
2002年 | 13篇 |
2001年 | 17篇 |
2000年 | 10篇 |
1999年 | 23篇 |
1998年 | 11篇 |
1997年 | 9篇 |
1996年 | 10篇 |
1995年 | 6篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1986年 | 2篇 |
排序方式: 共有575条查询结果,搜索用时 203 毫秒
1.
2.
Electric power systems are complex and commonly run near their operational limits. Power systems are basically designed based on the (N − 1) criterion. In these systems, total or partial blackouts are unavoidable. Cascading failures following an initial event is recognized as the main mechanism for power system blackouts. Undesirable activation of zone 3 of distance relays due to their local function has been identified as one of the major causes for propagation of cascading failures. In this paper, in order to mitigate the risk of power system blackouts, a novel approach is proposed for recognizing the critical line outages with the highest contribution in cascading failure and preventing their undesirable outage by blocking zone 3 of their distance relay. In this paper, based on the statistical activation of distance relays, a deterministic–probabilistic approach is developed for identifying the critical lines with the highest contribution in blackouts due to activation of zone 3 of their distance relays. In order to avoid interference of relay blocking with the main protection duty of distance relays, the proposed approach recognizes the minimum critical lines with the highest contribution in cascading failure for blocking zone 3 of their distance relays. The proposed approach is demonstrated on the New England 39-bus system and detailed simulation studies carried out to examine the validity and effectiveness of the proposed approach. 相似文献
3.
4.
System parameters of a microgrid change in its two operating modes primarily due to output current limitation of PWM based inverters connected with renewable energy sources. The unavailability of an appropriate protection scheme, which must be compatible with both modes of a microgrid operation, is a major problem in the implementation of a microgrid. Two important properties of the microgrid components are peer-to-peer, and plug-and-play. It means that there is no component like a master controller which is critical for the operation of a system, and a distributed-generation unit can be installed at any location in a microgrid. These properties further complicate the protection of a microgrid. This paper reports the MATLAB/SIMULINK model of a microgrid along with the models of the conventional protection schemes and renewable energy distributed-generation resources. Malfunctioning in the conventional protection schemes in islanding mode is identified and models of newly proposed protection schemes are developed. Different types of faults are simulated in all the protection zones of the system and the system parameters are analysed to identify the possible fault detection methods. Based on the simulation results, a protection scheme is recommended that can meet the protection standards such as selectivity, co-ordination and reliability. 相似文献
5.
本文在介绍了利用USB4751 DI/O模块和PCLD-785B继电器板构建多路信号转接器基础上,描述了开发24路电源负载调整率的自动测量系统组成框图,并针对继电器板接线示意图进行了工作原理说明,结合实际测量设计了在LabVIEW中如何实现自动控制的程序.该信号转接器已应用于实际测量工作中,克服手动测量、人工接线、手工... 相似文献
6.
A.M. El-Zonkoly 《Electric Power Systems Research》2011,81(7):1482-1490
The penetration of distributed generation (DG) in distribution power system would affect the traditional fault current level and characteristics. Consequently, the traditional protection arrangements developed in distribution utilities are difficult in coordination. Also, the reclosing scheme would be affected. With the rapid developments in distribution system automation and communication technology, the protection coordination and reclosing scheme based on information exchange for distribution power system can be realized flexibly. This paper proposes a multi-agent based scheme for fault diagnosis in power distribution networks with distributed generators. The relay agents are located such that the distribution network is divided into several sections. The relay agents measure the bus currents at which they are located such that it can detect and classify the fault, and determine the fault location. The proposed technique uses the entropy of wavelet coefficients of the measured bus currents. The performance of the proposed protection scheme is tested through simulation of two systems. The first system is a benchmark medium voltage (MV) distribution system and the second system is practical 66 kV system of the city of Alexandria. 相似文献
7.
Device-to-device (D2D) communications allow proximate cellular user equipments (UEs) to communicate with each other directly under the control of base station (BS). In this paper, considering the selection relaying (SR) rule which allows a subset of potential relays to forward the source’s data to the corresponding destination, we first establish a multi-relay system model where a D2D UE can act as not only a source but also a potential relay for another D2D link, and then analyze the cooperation behaviors among selfish UEs. Next a simple strategy is proposed to deal with the relay selection problem, and then the fair and efficient resource sharing problem among cooperating D2D UEs is formulated as a bargaining game. Since the game function is non-convex, we turn to an iterative method by introducing an auxiliary function to get the proportional fair resource allocation results. The system efficiency and fairness are proved by numeral simulation results. 相似文献
8.
9.
The proposed procedure is implemented without breaking the loop with the controller in operation, by activating a cascade of band-pass filters in series with a relay in the inner loop and a notch filter in the outer loop. A highly accurate estimate of the critical point of a process Gp(s) is obtained in the presence of measurement noise and load disturbance. The effectiveness of the proposed procedure is illustrated using a test batch consisting of stable, integrating and unstable processes, including dead-time. 相似文献
10.
In some applications, wireless sensor networks (WSNs) operate in very harsh environments and nodes become subject to increased risk of damage. Sometimes a WSN suffers from the simultaneous failure of multiple sensors and gets partitioned into disjoint segments. Restoring network connectivity in such a case is crucial in order to avoid negative effects on the application. Given that WSNs often operate unattended in remote areas, the recovery should be autonomous. This paper promotes an effective strategy for restoring the connectivity among these segments by populating the least number of relay nodes. Finding the optimal count and position of relay nodes is NP-hard and heuristics are thus pursued. We propose a Distributed algorithm for Optimized Relay node placement using Minimum Steiner tree (DORMS). Since in autonomously operating WSNs it is infeasible to perform a network-wide analysis to diagnose where segments are located, DORMS moves relay nodes from each segment toward the center of the deployment area. As soon as those relays become in range of each other, the partitioned segments resume operation. DORMS further model such initial inter-segment topology as Steiner tree in order to minimize the count of required relays. Disengaged relays can return to their respective segments to resume their pre-failure duties. We analyze DORMS mathematically and explain the beneficial aspects of the resulting topology with respect to connectivity, and traffic balance. The performance of DORMS is validated through extensive simulation experiments. 相似文献