首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   356篇
  免费   7篇
公路运输   23篇
综合类   14篇
水路运输   140篇
铁路运输   6篇
综合运输   180篇
  2022年   2篇
  2021年   2篇
  2020年   3篇
  2019年   9篇
  2018年   11篇
  2017年   13篇
  2016年   10篇
  2015年   4篇
  2014年   9篇
  2013年   90篇
  2012年   13篇
  2011年   11篇
  2010年   24篇
  2009年   16篇
  2008年   10篇
  2007年   12篇
  2006年   7篇
  2005年   10篇
  2004年   3篇
  2003年   2篇
  2002年   13篇
  2001年   2篇
  2000年   7篇
  1999年   2篇
  1998年   5篇
  1997年   3篇
  1996年   6篇
  1995年   4篇
  1994年   5篇
  1993年   5篇
  1992年   4篇
  1991年   4篇
  1989年   2篇
  1988年   1篇
  1987年   5篇
  1986年   1篇
  1985年   3篇
  1983年   3篇
  1982年   3篇
  1981年   2篇
  1980年   1篇
  1979年   2篇
  1978年   5篇
  1975年   5篇
  1974年   3篇
  1973年   5篇
  1972年   1篇
排序方式: 共有363条查询结果,搜索用时 9 毫秒
21.
There have been many efforts to develop a logistics information system in the Korean logistics industry. In spite of these efforts, there are many points which need improvement in the Logistics Information System, of which function is the electronic data communication without added value. This paper aims to describe some of the main problems and the successful factors which are being found in the evolution of the present EDI systems for clearing import/export container cargoes, with special reference to Singapore, Korea, and Japan. Following this, leaving legal issues aside, to suggest workable guidelines for designing a new efficient EDI system for container cargo logistics. As a result of the review, the following successful factors are drawn: (a) the planning, requirement analysis and design of EDI are critical, as it provides a framework for its implementation; (b) as the data of customs clearance are an integral part of a logistics EDI system, the inclusion of customs in the system design is essential; (c) the sharing system of cargo data as the framework of the logistics EDI is efficient for data interchange; (d) the EDI software for the user has been developed and provided by an EDI network operating company; and (e) to facilitate communication between trading partners and the transport sector, it is necessary to adopt a global message standard, such as EDIFACT.  相似文献   
22.
TBM及其在中国的应用(1)   总被引:3,自引:0,他引:3  
1前言 这篇报告援引了许多与中国未来工程有关的大型地下工程和特长深埋隧道工程实例.这些工程只有通过运用精湛的隧道施工技术(尤其是高度机械化的TBM)、特别的管理以及认识到采用这些方法所产生的能力的提高和费效比的增加才可能达到成功.这并不意味着毫无问题,而是因为在运用这些创新技术中所遇到的困难被相关部门顽强地克服了.  相似文献   
23.
This paper presents an off‐line forecasting system for short‐term travel time forecasting. These forecasts are based on the historical traffic count data provided by detectors installed on Annual Traffic Census (ATC) stations in Hong Kong. A traffic flow simulator (TFS) is developed for short‐term travel time forecasting (in terms of offline forecasting), in which the variation of perceived travel time error and the fluctuations of origin‐destination (O‐D) demand are considered explicitly. On the basis of prior O‐D demand and partial updated detector data, the TFS can estimate the link travel times and flows for the whole network together with their variances and covariances. The short‐term travel time forecasting by O‐D pair can also be assessed and the O‐D matrix can be updated simultaneously. The application of the proposed off‐line forecasting system is illustrated by a numerical example in Hong Kong.  相似文献   
24.
The plug-in hybrid electric vehicle (PHEV) may offer a potential near term, low-carbon alternative to today’s gasoline- and diesel-powered vehicles. A representative vehicle technology that runs on electricity in addition to conventional fuels was introduced into the MIT Emissions Prediction and Policy Analysis (EPPA) model as a perfect substitute for internal combustion engine (ICE-only) vehicles in two likely early-adopting markets, the United States and Japan. We investigate the effect of relative vehicle cost and all-electric range on the timing of PHEV market entry in the presence and absence of an advanced cellulosic biofuels technology and a strong (450 ppm) economy-wide carbon constraint. Vehicle cost could be a significant barrier to PHEV entry unless fairly aggressive goals for reducing battery costs are met. If a low-cost PHEV is available we find that its adoption has the potential to reduce CO2 emissions, refined oil demand, and under a carbon policy the required CO2 price in both the United States and Japan. The emissions reduction potential of PHEV adoption depends on the carbon intensity of electric power generation. Thus, the technology is much more effective in reducing CO2 emissions if adoption occurs under an economy-wide cap and trade system that also encourages low-carbon electricity generation.  相似文献   
25.
This article provides results on the net benefits generated from the natural resources in the Bohol Marine Triangle (BMT) in the Philippines. The BMT spans over 112,000 ha and its coastal ecosystems are rich in biodiversity and provide economic opportunities to the coastal communities. With a 10% discount rate, the accumulated total net benefits for the BMT resources over a 10-year period is US$11.54 million. Tourism and the municipal fisheries are the most important direct use values of the coastal and marine resources of the BMT accounting for 44% and 39% of the total net benefits. Annual revenues attributed to ecosystems were as follows: coral reefs, US$1.26 million; beach/intertidal area, US$1.12 million; marine waters, US$646,501; mangrove, US$239,561; and seagrass, US$105,990. The large market values indicate the dependence of the local community on the BMT coastal and marine resources. In the same way, non-market values show the important life-support functions of coastal and marine ecosystems. The net benefits reflect the magnitude of potential losses due to improper management of coastal and marine resources in the BMT. This valuation highlights the importance of the coastal services to the BMT economy and draws attention to the benefits the local stakeholders derive from BMT coastal resources. Policy measures can now take into account these values to justify a sufficient investment in coastal management efforts to sustain the flow of coastal services in the interest of current and future generations.  相似文献   
26.
Since 1992, coastal researchers at the University of North Carolina at Wilmington have been documenting the impacts of human recreational use on Masonboro Island, a component of the North Carolina National Estuarine Research Reserve, and the subsequent natural processes that mitigate these impacts. Both short-term and long-term natural mitigational processes were identified. The effects of these processes were found to be much more rapid than similar impacts on typical terrestrial settings. However, careful examination of the data suggests that both physical location of the impact site and natural variability of weather patterns and events play a role. Management implications of these findings are proposed.  相似文献   
27.
管道技术     
全世界正在以前所未有的速度消耗着石油和天然气,因此,需要以成本效益的方式开发新的资源。然而,最近管道设计公司面临更具挑战性的海上和海底环境,从而需要采取新的方式来克服不寻常的设计挑战  相似文献   
28.
This paper discusses a number of issues relating to the pre-analysis and cleaning of stated choice data, where we look specifically at the problems caused by non-trading, lexicographic and inconsistent response patterns. We argue that this process is considerably more complex and challenging than many in the field have hitherto acknowledged, with the standard practice being the use of rather ad hoc procedures for the identification of these phenomena. A detailed analysis on four different stated choice datasets highlights the potential impacts of these methods on model estimation results.  相似文献   
29.
Several authors have reported a strong linear relationship between daily phytoplankton production and the product of chlorophyll biomass, photic depth, and incident irradiance for a variety of estuaries. This “light · biomass” (BZpIo) formulation has been proposed as an alternative to traditional mechanistic approaches for computing phytoplankton production in numerical estuarine models. One limitation to their application in shallow systems is that the BZpIo models have been developed in relatively deep estuaries where light does not reach the bottom. We propose a nonlinear correction factor to adapt the BZpIo relationship to shallow systems where light does reach the bottom. Our function takes into account variations in incident irradiance, attenuation coefficient for light, photosynthetic efficiency, and maximum rate of photosynthesis. A series of correction polynomials are proposed for various ranges of incident irradiance, and are integrated into a single multiple polynomial which applies across all irradiance levels. Our new correction factor was tested against a 14C-based productivity dataset from shallow stations in Narragansett Bay, RI and an O2-based dataset from shallow (1.1 m) lagoon mesocosms at the University of Rhode Island. Results showed that our polynomials accurately correct BZpIo-predicted rates of production in shallow water columns. Application of our correction factor to a series of shallow water productivity datasets from the literature together with theoretical calculations show how significant the shallow water correction can be, especially in very shallow water columns with low turbidity.  相似文献   
30.
Choice of parking: Stated preference approach   总被引:2,自引:0,他引:2  
Over recent years, parking policy has become a key element of transport policy in many countries. Parking policy measures can affect many different dimensions of travel behaviour but are likely to be most significant in terms of travellers' choice of parking type and location. This dimension of travel choice has, to date, received comparatively little attention, yet is of vital importance if we are to properly understand and predict the effects of parking policy measures.This paper presents two studies addressing this issue carried out in the United Kingdom and Germany. Both studies used a stated preference approach in order to collect disaggregate data on travellers responses to changes in parking attributes and used these data to build simple logit models of parking type choice. The studies were designed in order to allow comparable choice models to be estimated from the two datasets. The results obtained strongly indicate the need to separately identify the costs associated with different components of the parking activity (e.g., general in-vehicle time, parking search time, egress time) and also point to the existence of significant differences in the relative valuation of these components across different journey purposes. Where possible, the results of the choice modelling exercises are also compared with existing revealed and stated preference results and are found to be generally in line with prior expectations.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号