全文获取类型
收费全文 | 893篇 |
免费 | 12篇 |
专业分类
公路运输 | 153篇 |
综合类 | 299篇 |
水路运输 | 228篇 |
铁路运输 | 158篇 |
综合运输 | 67篇 |
出版年
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 1篇 |
2020年 | 12篇 |
2019年 | 10篇 |
2018年 | 13篇 |
2017年 | 14篇 |
2016年 | 15篇 |
2015年 | 15篇 |
2014年 | 42篇 |
2013年 | 40篇 |
2012年 | 41篇 |
2011年 | 60篇 |
2010年 | 60篇 |
2009年 | 95篇 |
2008年 | 60篇 |
2007年 | 87篇 |
2006年 | 101篇 |
2005年 | 60篇 |
2004年 | 46篇 |
2003年 | 44篇 |
2002年 | 35篇 |
2001年 | 20篇 |
2000年 | 13篇 |
1999年 | 7篇 |
1998年 | 1篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 1篇 |
排序方式: 共有905条查询结果,搜索用时 15 毫秒
301.
302.
303.
提出一种利用GPS载波信号相位差测量技术进行实时确定弹体姿态的方法。通过对载波相位差测量航向和姿态原理的分析,建立GPS姿态确定的单差模型,推导采用GPS多天线姿态测量技术实时获取弹体飞行姿态的解算算法,应用最小二乘法估计解算基线向量,然后对GPS姿态估计算法进行仿真计算。仿真结果验证了模型、算法的正确性和有效性。 相似文献
304.
Review of GPS Travel Survey and GPS Data-Processing Methods 总被引:1,自引:0,他引:1
AbstractGlobal positioning system (GPS) devices have been utilised in travel surveys since the late 1990s. Because GPS devices are very accurate at recording time and positional characteristics of travel, they can correct the trip-misreporting issue resulting from self-reports of travel and improve the accuracy of travel data. Although the initial idea of using GPS surveys in transport data collection was just to replace paper-based travel diaries, GPS surveys currently are being applied in a number of transport fields. Several general reviews have been done about GPS surveys in the literature review sections in some papers, but a detailed systematic review from GPS data collection to the whole procedure of GPS data processing has not been undertaken. This paper comprehensively reviews the development of GPS surveys and their applications, and GPS data processing. Different from most reviews in GPS research, this paper provides a detailed and systematic comparison between different methods from trip identification to mode and purpose detection, introduces the methods that researchers and planners are currently using, and discusses the pros and cons of those methods. Based on this review, researchers can choose appropriate methods and endeavour to improve them. 相似文献
305.
306.
随着GSM网络增值业务快速发展,GPRS成为数据终端和数据网络的一种新连接,它为终端用户提供了高速无线IP和X.25分组数据接入服务。本文介绍了实现基于GSM网络的嵌入式远程终端控制单元的设计方案,介绍了该设计的硬件模块和软件设计流程,采用S3C44BOX作为微控制器芯片,用GT47模块接人无线网络,实现了控制中心对远程终端的控制。 相似文献
307.
GPS坐标向北京54坐标转换的方法 总被引:1,自引:0,他引:1
GPS测量得到的是WGS-84的地心空间直角坐标,而工程中通常使用地方独立坐标系。两者的转换方法一般分为平面转换模型和空间转换模型。平面转换模型原理简单,数值稳定可靠,但只适用于小范围的CPS测量;空间转换模型可用于大范围的CPS测量,按实际情况又分为七参数转换和三参数转换两种。对这两种转换模型进行介绍。 相似文献
308.
GPS在高速公路工程施工测量中的应用 总被引:1,自引:0,他引:1
GPS(Global Positioning System)全球定位系统是美国研制并在1994年投入使用的卫星导航与定位系统,该系统已被广泛使用。重点介绍GPS-RTK在湖北宜巴高速公路松林坡大桥桩基测量中的应用,并根据实践总结了GPS-RTK在施工测量中的注意事项。 相似文献
309.
Over the past few years, GPS has been used in a number of surveys in the US to assess the accuracy of household travel surveys.
The results have been somewhat alarming in that most of these exercises have shown that the standard trip-based CATI survey
conducted in the US under-reports travel by about 20–25%. It was decided to use GPS to assess the accuracy of the Sydney Household
Travel Survey, a continuous survey conducted by face-to-face interviewing. The procedure used was for the interviewers to
recruit households for the household travel survey in the normal manner, and then, if the household met certain criteria,
to endeavour to recruit the household to also undertake a GPS survey. A small sample of about 50 households was obtained,
and GPS devices successfully retrieved that measured data on the same day as the travel diary was completed. In addition,
participants in the GPS survey completed a prompted recall survey a week or two later, using maps and tabulations of travel
obtained from the GPS devices, to identify mode, purpose and occupancy for trips measured by the GPS, and also to check for
accuracy in defining trip ends and total number of trips. Based on the analysis of the GPS compared to the diary results,
it was found that respondents under-reported their travel by about 7%, which is much less than in the US CATI results. Respondents
were also found to under-report travel distances and over-report travel times. There was also a high incidence of non-reporting
for VKT.
相似文献
Peter StopherEmail: |
310.