全文获取类型
收费全文 | 16677篇 |
免费 | 1932篇 |
国内免费 | 1184篇 |
专业分类
电工技术 | 1736篇 |
技术理论 | 1篇 |
综合类 | 2330篇 |
化学工业 | 583篇 |
金属工艺 | 201篇 |
机械仪表 | 760篇 |
建筑科学 | 4232篇 |
矿业工程 | 1376篇 |
能源动力 | 535篇 |
轻工业 | 328篇 |
水利工程 | 1422篇 |
石油天然气 | 406篇 |
武器工业 | 216篇 |
无线电 | 1466篇 |
一般工业技术 | 822篇 |
冶金工业 | 412篇 |
原子能技术 | 54篇 |
自动化技术 | 2913篇 |
出版年
2024年 | 68篇 |
2023年 | 180篇 |
2022年 | 323篇 |
2021年 | 409篇 |
2020年 | 471篇 |
2019年 | 403篇 |
2018年 | 374篇 |
2017年 | 444篇 |
2016年 | 530篇 |
2015年 | 543篇 |
2014年 | 968篇 |
2013年 | 855篇 |
2012年 | 1178篇 |
2011年 | 1252篇 |
2010年 | 1020篇 |
2009年 | 1101篇 |
2008年 | 1137篇 |
2007年 | 1382篇 |
2006年 | 1191篇 |
2005年 | 1110篇 |
2004年 | 881篇 |
2003年 | 778篇 |
2002年 | 651篇 |
2001年 | 531篇 |
2000年 | 474篇 |
1999年 | 343篇 |
1998年 | 253篇 |
1997年 | 198篇 |
1996年 | 160篇 |
1995年 | 147篇 |
1994年 | 124篇 |
1993年 | 71篇 |
1992年 | 63篇 |
1991年 | 46篇 |
1990年 | 23篇 |
1989年 | 22篇 |
1988年 | 20篇 |
1987年 | 18篇 |
1986年 | 9篇 |
1985年 | 5篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 6篇 |
1979年 | 11篇 |
1977年 | 3篇 |
1962年 | 1篇 |
1959年 | 2篇 |
1955年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Although hybrid Petri net (HPN) is a popular formalism in modelling hybrid production systems, the HPN model of large scale systems gets substantially complicated for analysis and control due to large dimensionality of such systems. To overcome this problem, a typical approach is to decompose the net into subnets and then control the plant through hierarchical or decentralized structures. Although this concept has been widely discussed in the literature for discrete PNs, there is a lack of research for HPNs. In this paper, a new method of decomposition of first-order hybrid Petri nets (FOHPNs) is proposed first and then the hierarchical control of the subnets through a coordinator is introduced. The advantage of using the proposed approach is validated by an existing example. A sugar milling case study is analysed by using a decomposed FOHPN model and the optimization results are compared against the results of the approaches presented in other papers. Simulation results show not only an improvement in production rate, but also show the ability to control the plant online. In addition, by using the hierarchical control structure for an FOHPN model, it is possible to reduce the cost of communication links, improve the reliability of the system, maintain the plant locally, and partially redesign the system. 相似文献
2.
基于传统AI-EBG结构,提出了一种小尺寸的增强型电磁带隙结构,实现了从0.5~9.4 GHz的宽频带-40 dB噪声抑制深度,且下截止频率减少到数百MHz,可有效抑制多层PCB板间地弹噪声。文中同时研究了EBG结构在高速电路应用时的信号完整性问题,使用差分信号方案可改善信号完整性。 相似文献
3.
The falling down problem has become one of the very important issues of global public health in an aging society. The specific equipment was adopted as the detection device of falling-down in the early studies, but it is inconvenient for the elderly and difficult for future application. The smart phone more commonly used than the specific fall detection equipment is selected as a mobile device for human fall detection, and a fall detection algorithm is developed for this purpose. What the user has to do is to put the smart phone in his/her thigh pocket for falling down detection. The signals detected by the tri-axial G-sensor are converted into signal vector magnitudes as the basis of detecting a human body in a stalling condition. The Z-axis data sets are captured for identification of human body inclination and the occurrence frequencies at the peak of the area of use are used as the input parameters. A high-level fuzzy Petri net is used for the analysis and the development of identifying human actions, including normal action, exercising, and falling down. The results of this study can be used in the relevant equipments or in the field of home nursing. 相似文献
4.
Dong‐Wook Kim 《ETRI Journal》2006,28(1):84-86
This letter presents a small‐sized, high‐power single‐pole double‐throw (SPDT) switch with defected ground structure (DGS) for wireless broadband Internet application. To reduce the circuit size by using a slow‐wave characteristic, the DGS is used for the quarter‐wave (°/4) transmission line of the switch. To secure a high degree of isolation, the switch with DGS is composed of shunt‐connected PIN diodes. It shows an insertion loss of 0.8 dB, an isolation of 50 dB or more, and power capability of at least 50 W at 2.3 GHz. The switch shows very similar performance to the conventional shunt‐type switch, but the circuit size is reduced by about 50% simply with the use of DGS patterns. 相似文献
5.
运动会新闻发布系统的设计与实现 总被引:2,自引:0,他引:2
针对运动会比赛期间随时需要方便、快捷、高效地更新大量新闻的需求 ,研制和开发一套运动会新闻发布系统。利用微软最新推出的asp .net动态网页开发工具 ,采用web分布式三层设计模型设计实现了一套操作简单、功能完善、具有通用性的运动会新闻发布系统 相似文献
6.
7.
连续波半主动雷达制导空空导弹截获跟踪距离计算 总被引:1,自引:1,他引:0
分析了连续波半主动雷达制导导弹导引头工作电磁环境和对武器系统攻击区的影响,建立了热噪声和杂波干扰环境下导引头截获距离方程,分析推导了直波泄漏干扰,地杂波干扰的计算公式,并在此基础上给出了导弹允许攻击区计算公式。 相似文献
8.
Safety-critical software systems such as certain nuclear instrumentation and control (NI&C) systems should be developed with thorough verification. This study presents a method of software requirement verification with a case study for a nuclear power plant (NPP) protection system. The verification introduces colored petri net (CPN) for system modeling and prototype verification system (PVS) for mathematical verification. In order to aid flow-through from modeling by CPN to mathematical proof by PVS, an information extractor from CPN models has been developed in this paper. In order to convert the extracted information to the PVS specification language, a translator has also been developed. This combined method has been applied to the functional requirements of the Wolsong NPP Shut Down System #2 (SDS2); logical properties of the requirements were verified. Through this research, guidelines and a tool support for the use of formal methods have been developed for application to NI&C software verification. 相似文献
9.
织金电视台通过对有线电视网络进行双向改造,为Internet宽带接入、数字电视、VOD等多媒体应用提供了运行平台,介绍织金县城区HFC双向网络设计方案。 相似文献
10.