全文获取类型
收费全文 | 4958篇 |
免费 | 486篇 |
国内免费 | 538篇 |
专业分类
电工技术 | 116篇 |
技术理论 | 1篇 |
综合类 | 326篇 |
化学工业 | 90篇 |
金属工艺 | 94篇 |
机械仪表 | 235篇 |
建筑科学 | 334篇 |
矿业工程 | 58篇 |
能源动力 | 64篇 |
轻工业 | 28篇 |
水利工程 | 44篇 |
石油天然气 | 49篇 |
武器工业 | 13篇 |
无线电 | 809篇 |
一般工业技术 | 187篇 |
冶金工业 | 109篇 |
原子能技术 | 52篇 |
自动化技术 | 3373篇 |
出版年
2023年 | 27篇 |
2022年 | 49篇 |
2021年 | 66篇 |
2020年 | 71篇 |
2019年 | 53篇 |
2018年 | 69篇 |
2017年 | 95篇 |
2016年 | 111篇 |
2015年 | 163篇 |
2014年 | 319篇 |
2013年 | 294篇 |
2012年 | 413篇 |
2011年 | 430篇 |
2010年 | 409篇 |
2009年 | 411篇 |
2008年 | 426篇 |
2007年 | 460篇 |
2006年 | 445篇 |
2005年 | 389篇 |
2004年 | 280篇 |
2003年 | 272篇 |
2002年 | 166篇 |
2001年 | 115篇 |
2000年 | 132篇 |
1999年 | 75篇 |
1998年 | 52篇 |
1997年 | 50篇 |
1996年 | 37篇 |
1995年 | 27篇 |
1994年 | 13篇 |
1993年 | 9篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 5篇 |
1989年 | 2篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1973年 | 1篇 |
1963年 | 1篇 |
1962年 | 1篇 |
1959年 | 2篇 |
1958年 | 1篇 |
排序方式: 共有5982条查询结果,搜索用时 31 毫秒
91.
92.
93.
在无线传感器网络中,由于传感器节点的能源十分有限,节能是设计的首要因素。然而,无线传感器网络的多业务在现实生活应用中对QoS(服务质量)都有不同的需求,这就使得WSN网络的QoS研究成为了专家学者们的主要研究方向。在WSN网络拓扑结构和业务类型的研究基础上,使用网络模拟器(Network Simulator Version 2,NS2)来搭建基于多业务共存的星型以及对等结构两种WSN网络仿真平台,建立多种业务流量模型,实现以无线传感器网络协议、流量模型、拓扑为基础的功能模块化设计;并对无线传感器网络关键性能进行了仿真模拟,实现延时、吞吐量、能耗等关键性能的分析。 相似文献
94.
95.
《Expert systems with applications》2014,41(13):5702-5709
Context-aware applications, which consist of a sensor system, a reasoning system and service artifacts such as mobile devices, kiosks and robots, require data from the sensors to be queried on a continuous basis. The smaller the sensing interval and the greater the amount of service time, the more accurate the service, but the more energy is consumed. Thus, use of context-aware applications always involves a trade-off. In this paper, we propose an automatic method of optimizing the level of personalization involving the sensing cycle and service time of a personalized application. The method proposes a quadratic form of total cost curve which demonstrated that the minimum identified value is always the global optimum. This eliminates the necessity of an exhaustive search for the minimum value for all levels of personalization. 相似文献
96.
Determinants of energy demand in the French service sector: A decomposition analysis 总被引:1,自引:0,他引:1
This paper analyzes the changes in the energy consumption of the service sector in France over the period 1995–2006, using the logarithmic mean Divisia index I (LMDI I) decomposition method. The analysis is carried out at various disaggregation levels to highlight the specifics of each sub-sector and end-use according to their respective determinants. The results show that in this period the economic growth of the service sector was the main factor that led to the increase in total energy consumption. Structure, productivity, substitution and intensity effects restricted this growth, but with limited effect. By analyzing each end-use, this paper enables a more precise understanding of the impact of these factors. The activity effect was the main determinant of the increase in energy consumption for all end-uses except for air conditioning, for which the equipment rate effect was the main factor. Structural changes in the service sector primarily impacted energy consumption for space heating and cooking. Improvements in productivity limited the growth of energy consumption for all end-uses except for cooking. Finally, energy efficiency improvements mainly affected space-heating energy use. 相似文献
97.
本文简要介绍DR的成像原理和详细分析二例飞利浦Tele Diagnost X线影像系统的故障检查排除方法。 相似文献
98.
基于WEB三层结构开发的人才网站相当普遍,但由于行业、区域建设的独立性,目前我国的绝大多数人才网站都是以地区为基础,各系统自成体系,从而引起资源分散、信息共享困难。本系统运用WebService系统集成方案,面向对象设计方法和程序封特性,突出三层结构下的分布式资源共享、跨平台支持,满足大中型人才市场的功能需求。 相似文献
99.
Besides constructed quality and environmental quality, the quality of facilities in residential buildings is influential to the living quality of numerous residents there. The functional quality of the facilities, in turn, is dependent on the quality of their operation and management. A review of the relevant literature and a focus group discussion with Facility Management (FM) practitioners, which were parts of the study reported here, unveiled that prior performance evaluation studies focussed on assessing the outcome of FM services whereas an analytical method suitable for holistic evaluation of the services is lacking. An interview survey with 297 users of a typical residential estate in Hong Kong was carried out to solicit their perceived levels of importance and performance of FM services. The responses were tested using the Analytical Hierarchy Process (AHP) to isolate those with inconsistent judgments, followed by computing the weightings for various aspects of FM services based on the consistent responses. The calculation of a weighted performance score for benchmarking purposes and a critical evaluation of the cost-effectiveness of FM services, which are crucial for achieving a quality and sustainable built environment, are illustrated. 相似文献
100.
Companies frequently decide on the location and design for new facilities in a sequential way. However, for a fixed number of new facilities, the company might be able to improve its profit by taking its decisions for all the facilities simultaneously. In this paper we compare three different strategies: simultaneous location and independent design of two facilities in the plane, the same with equal designs, and the sequential approach of determining each facility in turn. The basic model is profit maximization for the chain, taking market share, location costs and design costs into account. The market share captured by each facility depends on the distance to the customers (location) and its quality (design), through a probabilistic Huff-like model. Recent research on this type of models was aimed at finding global optima for a single new facility, holding quality fixed or variable, but no exact algorithm has been proposed to find optimal solutions for more than one facility. We develop such an exact interval branch-and-bound algorithm to solve both simultaneous location and design two-facility problems. Then, we present computational results and exhibit the differences in locations and qualities of the optimal solutions one may obtain by the sequential and simultaneous approaches. 相似文献