全文获取类型
收费全文 | 1185篇 |
免费 | 122篇 |
国内免费 | 37篇 |
专业分类
电工技术 | 14篇 |
综合类 | 44篇 |
化学工业 | 6篇 |
金属工艺 | 3篇 |
机械仪表 | 39篇 |
建筑科学 | 47篇 |
矿业工程 | 8篇 |
能源动力 | 32篇 |
轻工业 | 12篇 |
水利工程 | 18篇 |
石油天然气 | 5篇 |
武器工业 | 25篇 |
无线电 | 513篇 |
一般工业技术 | 74篇 |
冶金工业 | 7篇 |
原子能技术 | 8篇 |
自动化技术 | 489篇 |
出版年
2024年 | 5篇 |
2023年 | 15篇 |
2022年 | 27篇 |
2021年 | 32篇 |
2020年 | 38篇 |
2019年 | 22篇 |
2018年 | 18篇 |
2017年 | 20篇 |
2016年 | 46篇 |
2015年 | 38篇 |
2014年 | 58篇 |
2013年 | 42篇 |
2012年 | 57篇 |
2011年 | 63篇 |
2010年 | 57篇 |
2009年 | 66篇 |
2008年 | 75篇 |
2007年 | 77篇 |
2006年 | 77篇 |
2005年 | 48篇 |
2004年 | 48篇 |
2003年 | 47篇 |
2002年 | 32篇 |
2001年 | 26篇 |
2000年 | 21篇 |
1999年 | 41篇 |
1998年 | 26篇 |
1997年 | 22篇 |
1996年 | 17篇 |
1995年 | 18篇 |
1994年 | 27篇 |
1993年 | 21篇 |
1992年 | 13篇 |
1991年 | 25篇 |
1990年 | 19篇 |
1989年 | 12篇 |
1988年 | 6篇 |
1987年 | 5篇 |
1986年 | 10篇 |
1985年 | 4篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 8篇 |
1977年 | 1篇 |
1972年 | 1篇 |
1971年 | 2篇 |
排序方式: 共有1344条查询结果,搜索用时 7 毫秒
51.
针对电力系统内部作为应急通信手段的卫星数据通信系统,提出了一种将其与现有的广域网相结合,提高系统利用率的一种方法。 相似文献
52.
卫星机载发射机属于薄壁复杂结构件,其整体精确热分析因为多种原因而无法进行,因此有必要对发射机热分析策略予以研究。本文通过对类似于发射机结构的模拟结构件热分析研究,提出了可用于卫星机载发射机热分析的策略技术,采用这种策略技术对实际卫星机载发射机进行的热分析,获得了可贵工程设计应用的有关数据。 相似文献
53.
Beekeeping plays an important role in increasing and diversifying the incomes of many rural communities in Kingdom of Saudi Arabia. However, despite the region’s relatively good rainfall, which results in better forage conditions, bees and beekeepers are greatly affected by seasonal shortages of bee forage. Because of these shortages, beekeepers must continually move their colonies in search of better forage. The aim of this paper is to determine the actual bee forage areas with specific characteristics like population density, ecological distribution, flowering phenology based on color satellite image segmentation. Satellite images are currently used as an efficient tool for agricultural management and monitoring. It is also one of the most difficult image segmentation problems due to factors like environmental conditions, poor resolution and poor illumination. Pixel clustering is a popular way of determining the homogeneous image regions, corresponding to the different land cover types, based on their spectral properties. In this paper Hopfield neural network (HNN) is introduced as Pixel clustering based segmentation method for agriculture satellite images. 相似文献
54.
Recently, earth observation system by using satellite network has attracted much attention due to its wide coverage and disaster resistance. Although the system is useful for collecting various data, which have an effect on a natural disaster, ecology and so forth, earth observation satellite hardly send the collected observation data to the ground station. This is because that the earth observation satellite needs to orbit near surface of the earth to get high-precision data, and it limited the time that can be used to send the observed data traffic to the ground station. Additionally, the amount of the observed data drastically increase in these days. Thus, we focus on the data relay satellite using optical communication in this network. By relaying observed data to traffic to the relay satellite, which has geostationary orbit, it is possible to increase the chance of sending data for the observation satellite due to the wide coverage of the relay satellite. In addition, laser light that is used in optical communication in satellite network has high frequency and it can deliver large data compared with radio wave. However, laser light is greatly influenced by atmosphere, and optical link capacity between satellite and ground station drastically changes according to weather condition. Therefore, we propose a new data traffic control method to use the network constructed by satellites which has mass storage device effectively according to the condition of optical downlink between satellite and optical ground station. The effectiveness of the proposed method is evaluated with numerical result. 相似文献
55.
Alberto Reyna Marco A. Panduro Carlos del Rio-Bocio 《Expert systems with applications》2012,39(8):6872-6878
The design of an aperiodic planar array is presented in this research. This design of aperiodic arrays considers the reduction of the side lobe level and the isoflux radiation requirements for GEO (Geostationary Earth Orbit) satellite applications. In this way, it is considered four different optimization cases. The first two cases are optimizations of amplitude and phase excitations for the antenna elements in a uniform antenna array and the last two cases are optimizations of positions of the antenna elements and certain number of levels of amplitude excitation in an aperiodic array. In this case, it is proposed a simple new approach combining the main idea of both thinned theory and random arrays approaches. For this optimization problem, the well-known method of Genetic Algorithms (GA) is utilized. The obtained results show the proper performance of the array factor to provide the isoflux radiation and low side lobe level. Depending on the performance requirements, the design of the aperiodic array could lead the satellite hardware to be reduced significantly even more that results presented previously in the literature. 相似文献
56.
X. Li W. Pichel P. Clemente-Colón V. Krasnopolsky J. Sapper 《International journal of remote sensing》2013,34(7):1285-1303
An interactive validation monitoring system is being used at the NOAA/NESDIS to validate the sea surface temperature (SST) derived from the NOAA-12 and NOAA-14 polar orbiting satellite AVHRR sensors for the NOAA CoastWatch program. In 1997, we validated the SST in coastal regions of the Gulf of Mexico, Southeast US and Northeast US and the lake surface temperatures in the Great Lakes every other month. The in situ 相似文献
57.
简要阐述了国内外露天矿山信息化建设的发展现状,分析了卫星技术、导航定位技术、遥感技术在露天矿山信息化建设中的应用需求与发展前景,论述了基于卫星技术等新技术手段建设数字化矿山综合信息系统的建设思路、实施方案以及对促进矿业及相关产业可持续发展的重要意义。 相似文献
58.
59.
60.