全文获取类型
收费全文 | 269篇 |
免费 | 71篇 |
专业分类
电工技术 | 29篇 |
综合类 | 75篇 |
化学工业 | 16篇 |
金属工艺 | 6篇 |
机械仪表 | 4篇 |
建筑科学 | 4篇 |
矿业工程 | 2篇 |
能源动力 | 18篇 |
轻工业 | 2篇 |
无线电 | 77篇 |
一般工业技术 | 20篇 |
自动化技术 | 87篇 |
出版年
2023年 | 6篇 |
2022年 | 1篇 |
2021年 | 1篇 |
2020年 | 9篇 |
2019年 | 2篇 |
2018年 | 16篇 |
2017年 | 47篇 |
2016年 | 4篇 |
2015年 | 11篇 |
2014年 | 17篇 |
2013年 | 22篇 |
2012年 | 16篇 |
2011年 | 28篇 |
2010年 | 31篇 |
2009年 | 23篇 |
2008年 | 15篇 |
2007年 | 31篇 |
2006年 | 17篇 |
2005年 | 19篇 |
2004年 | 2篇 |
2003年 | 4篇 |
2002年 | 1篇 |
2000年 | 1篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1993年 | 7篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1987年 | 3篇 |
1981年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有340条查询结果,搜索用时 15 毫秒
1.
《Computer Networks》2008,52(14):2779-2796
Wireless sensor and actor networks (WSANs) have recently emerged with the idea of combining wireless sensor networks (WSNs) and mobile ad hoc networks (MANETs). In addition to resource constrained sensors, resource rich and mobile actor nodes are employed in WSANs. These actors can collect data from the sensors and perform appropriate actions as a result of processing such data. To perform the actions at all parts of the region in a timely manner, the actors should be deployed in such a way that they might be able to communicate with each other and cover the whole monitored area. This requires that the actors should be placed carefully prior to network operation in order to maximize the coverage and maintain the inter-actor connectivity. In this paper, we propose a distributed actor deployment algorithm that strives to maximize the coverage of actors without violating the connectivity requirement. The approach applies repelling forces between neighboring actors and from the sensors that sit on the boundaries in order to spread them in the region. The spreading of the nodes is done using a tree of actors which can provide more freedom for the movement of the nodes but at the same time maintain the required connectivity among the nodes. We present two techniques for creation of such an actor tree which are based on local pruning of the actor links and spanning tree of the inter-actor network. The performance of our approach is validated both analytically and experimentally. 相似文献
2.
《Ceramics International》2020,46(5):5706-5714
In this study, we synthesized nanostructured zinc oxide (ZnO) by using various concentrations (0–0.05 M) of cetyltrimethylammonium bromide (CTAB) as a surfactant to optimize its morphology for gas sensor applications. The optimization process was used to elucidate the morphology effects (rod-shaped and flower-shaped morphologies). The morphologies were investigated through scanning electron microscopy, in which the assembly of nanorods leading to a spherical microstructure with a CTAB concentration of 0.005 M was observed. Brunauer–Emmett–Teller isotherm measurements revealed a surface area of 7.928 g/m2 for the flower-like morphology, which was relatively higher than those of other CTAB-assisted morphologies. Such morphological features were expected to contribute toward high-performance gas-sensing. The effect of morphology variation on the resistance of ZnO microstructures was used for gas measurements. Among the varied morphologies, a sample with a spherical flower-shaped morphology exhibited a very high response at low temperatures (~29 at 25 °C) toward NOX gas (0.75 ppm) and a high selectivity toward NOx among ammonia (NH3), toluene (C6H5CH3), carbon monoxide (CO), acetone (CH3COCH3), and ethanol (C2H5OH). Raman and photoluminescence spectroscopy analyses unraveled the presence of a high density of oxygen vacancies in the sample, thereby suggesting a close link between the defective nature of the sample and the high response of the flower-like ZnO at low temperatures. 相似文献
3.
Jose M. Algueta Antonio J. Lopez‐Martin Jaime Ramirez‐Angulo Ramon G. Carvajal 《International Journal of Circuit Theory and Applications》2014,42(8):831-841
A technique to improve the input and output range of CMOS transconductors with resistive current division for continuous tuning is presented. Using it, a tunable transconductor is proposed which features high linearity over a wide input range and simplicity. Measurement results of the transconductor, fabricated in a 0.5 µm CMOS process, show an IM3 of ?66 dB for a ±1.65 V supply and two input tones centered at 1 MHz of 1 Vpp each, and only 0.7 mW of power consumption. This represents an improvement of 13 dB versus the same transconductor using conventional current division. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
4.
一些功能不同的双口网络适当地连接在一起会实现某种特定的功能.双口网络间的连接方式有:串联、并联、串-并联、并-串联和级联.除级联方式外,其它互连方式都存在有效互连的问题,只有在有效连接的情况下,讨论双口网络的参数矩阵与各分双口网络参数矩阵的关系才有意义.以双口网络的串联连接为例,证明了双口网络有效互连与端口有效性检查互为充要条件的结论,并给出了当互连的双口网络不满足有效连接判据时如何实现有效连接.这对双口网络互连的教学具有一定的帮助. 相似文献
5.
Model-driven software engineering requires the refinement of abstract models into more concrete, platform-specific ones. To create and verify such refinements, behavioral models capturing recon- figuration or communication scenarios are presented as instances of a dynamic meta-model, i.e., a typed graph transformation system specifying the concepts and basic operations scenarios may be composed of. Possible refinement relations between models can now be described based on the corresponding meta-models.In contrast to previous approaches, refinement relations on graph transformation systems are not defined as fixed syntactic mappings between abstract transformation rules and, e.g., concrete rule expressions, but allow for a more loose, semantically defined relation between the transformation systems, resulting in a more flexible notion of refinement. 相似文献
6.
TangZhi ZhouYinqing LiJingwen 《电子科学学刊(英文版)》2004,21(2):152-158
Large range cell migration is a severe challenge to imaging algorithm for spaceborne SAR. Based on design of Finite Impulse Response (FIR) filter and Range Doppler (RD) algorithm,a realization of quicklook imaging for large range cell migration is proposed. It realized quick-look imaging of 8 times reduced resolution with parallel processing on memory shared 8 CPU SGI server. According to simulation experiment, this quick-look imaging algorithm with parallel processing can image 16384x16384 SAR raw data within 6 seconds. It reaches the requirement of real-time imaging. 相似文献
7.
I.D. Margaris A.D. HansenP. Sørensen N.D. Hatziargyriou 《Electric Power Systems Research》2011,81(4):880-887
Technical requirements set by the network operators nowadays include various aspects, such as fault ride-through capability of wind turbines during faults, voltage-reactive power control and overall control of the wind farms as conventional power plants. Detailed models for the power system as well as for the wind farms are therefore essential for power system studies related to these issues, especially when applied to non interconnected systems with high wind power penetration. Detailed generic models for three different wind turbine technologies - Active Stall Induction Generator (ASIG), Doubly Fed Asynchronous Generator (DFAG) and Permanent Magnet Synchronous Generator (PMSG) - are applied and issues regarding interaction with the power system are investigated. This paper provides conclusions about the dynamic security of non-interconnected power systems with high wind power penetration based on a complete model representation of the individual components of the system; three different types of conventional generators are included in the model, while the protection system is also incorporated. The load shedding following faults is finally discussed. 相似文献
8.
研究了一种应用CPPM结构的混合励磁风力外转同步发电机.简要介绍了其结构和原理,进行了三维磁场仿真,讨论了直流励磁结构的设计问题,给出了样机试验结果及相关分析. 相似文献
9.
提出一种图像中人体快速自动检测方法。提取图像的多尺度-多形状方向梯度直方图(HOG)特征向量,用于描述人体的形状特征,结合Adaboost机器学习法训练级联型分类器,以加速人体的检测过程。相比较传统算法,该方法没有采用静态背景模型,也不是仅仅依赖于易受外部环境因素干扰的颜色信息,从而一定程度地适应了人体姿态变化,以及非结构化环境下常见的光照波动、背景杂乱等不良因素所带来的干扰。实验验证了该方法的准确性和较高的计算效率。 相似文献
10.
脊波导在传播电磁波的过程中伴随有能量损耗,为了研究填充介质脊波导的衰减特性,本文采用有限元法借助Matlab软件计算了TE模式下部分填充介质倒梯形对称双脊波导的衰减常数和功率容量.分析了脊波导衰减常数和功率容量与脊波导尺寸、工作频率、填充介质相对介电常数之间的关系,给出关系曲线图.这些结果将丰富现有的填充非均匀介质脊波导的数据,为填充介质脊波导的设计和优化提供有价值的依据. 相似文献