全文获取类型
收费全文 | 1080篇 |
免费 | 8篇 |
专业分类
公路运输 | 320篇 |
综合类 | 43篇 |
水路运输 | 370篇 |
铁路运输 | 36篇 |
综合运输 | 319篇 |
出版年
2023年 | 10篇 |
2022年 | 20篇 |
2021年 | 8篇 |
2020年 | 9篇 |
2019年 | 13篇 |
2018年 | 36篇 |
2017年 | 15篇 |
2016年 | 35篇 |
2015年 | 8篇 |
2014年 | 31篇 |
2013年 | 197篇 |
2012年 | 35篇 |
2011年 | 53篇 |
2010年 | 42篇 |
2009年 | 52篇 |
2008年 | 51篇 |
2007年 | 29篇 |
2006年 | 18篇 |
2005年 | 19篇 |
2004年 | 20篇 |
2003年 | 7篇 |
2002年 | 17篇 |
2001年 | 10篇 |
2000年 | 17篇 |
1999年 | 13篇 |
1998年 | 25篇 |
1997年 | 15篇 |
1996年 | 21篇 |
1995年 | 19篇 |
1994年 | 6篇 |
1993年 | 8篇 |
1992年 | 16篇 |
1991年 | 10篇 |
1990年 | 13篇 |
1989年 | 10篇 |
1988年 | 7篇 |
1987年 | 9篇 |
1986年 | 8篇 |
1985年 | 10篇 |
1984年 | 9篇 |
1983年 | 15篇 |
1982年 | 8篇 |
1981年 | 16篇 |
1980年 | 14篇 |
1979年 | 19篇 |
1977年 | 18篇 |
1976年 | 14篇 |
1975年 | 11篇 |
1974年 | 12篇 |
1973年 | 7篇 |
排序方式: 共有1088条查询结果,搜索用时 250 毫秒
71.
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
72.
Robert Warren 《Coastal management》2013,41(1-2):119-125
This article reviews the history of esthetics and its role in the development of outdoor recreation policy. Current research is also reviewed, demonstrating the broad scope and complexity of esthetics as a focus for research. Finally, in the absence of sufficient research for formulating coastal recreation planning and management decisions, the ethics of coastal recreation “development”; is considered. 相似文献
73.
Abstract In southern Rhode Island, there is growing concern that housing and recreational demands will soon overwhelm the capacity of the coastal salt ponds to absorb wastes, produce seafood, and maintain scenic qualities. As a result, coastal towns have been studying the feasibility of using land controls such as downzoning to protect these coastal amenities. The paper presents an economic analysis of the downzoning program proposed in the town of South Kingstown. Hedonic price and contingent valuation methods are used to value coastal amenities. The estimated net present value of “swimmable” water is shown to be $3.1 million. 相似文献
74.
Chia-Juch Chang Robert D. Miles Kumares C. Sinha 《Transportation Research Part B: Methodological》1981,15(4):227-238
A regional railroad network is presented to evaluate the system's response to increased coal traffic. An optimal, multimodal, coal-shipping pattern is developed for the study region to minimize total costs and to efficiently use the existing network. A two-stage, general model allocates resources among demands and then assigns flows to the network according to efficiency criteria. The model is sufficiently general to permit modification for specific needs, assumptions and data. Government agencies and industries can apply the model in resource allocation decisions and transportation policy analysis. 相似文献
75.
The location of bus garages is a complex issue that has received recent attention in the literature. Given a bus system, the number of bus garages and their locations depend on garage cost, deadheading cost and environmental impacts. An approximate analytical model is used to determine the number of bus garages that minimizes the above costs. The concept of a slowly varying density of bus-route origins (hence deadheads) per unit area is used to model deadheading costs. The increased deadheading caused by breakdowns and accidents is also considered. The garage cost is modeled as a function of the number of buses stored. A closed-form solution is obtained for the optimal density of garages, when the garage cost function is linear. The actual locations of garages and the allocations of buses to the garages are found using a discrete space location-allocation model formulated so as to consider the environmental impact associated with buses deadheading through populated neighborhoods. 相似文献
76.
John Cooper D Nandhakuar 《经济导报》2009,(4):24-28
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
77.
The paper reports on simulation experiments conducted by the International Study Group on Land‐Use/Transport Interaction (ISGLUTI) for the metropolitan region of Dortmund in the Federal Republic of Germany. Three land‐use/transport simulation models were applied to the Dortmund region: the DORTMUND model developed at the University of Dortmund, the LILT model being used at University College London and the MEPLAN package developed by Marcial Echenique & Partners in Cambridge. The three models are briefly characterized and their ex‐post forecasts are compared with the actual development of the region. The final section of the paper compares how the three models respond to a common set of assumptions and policies from the fields of land‐use control, traffic management and transport investment. The differences in model response give insights into the validity of the theoretical foundations and internal structure of the models. 相似文献
78.
When using limited funds on bicycle facilities, it would be helpful to know the extent to which a new facility will be used. If a bicycle lane is added to a street, how many bicyclists will no longer use the adjacent sidewalk? If a separate bicycle path is constructed, how many bicyclists will move from the street or sidewalk? This study seeks to identify factors that explain a bicyclist’s choice between available facility choices—off-street (sidewalk and bicycle path) or on-street (bicycle lane and roadway). This paper investigates these issues through a survey of bicyclists headed to Purdue University in West Lafayette, IN, USA. The first data collected to address these questions were “site-based”. Bicyclists were interviewed on campus at the end of their trips and asked which part of the cross-sections along their routes they had used—on-street or off-street. The characteristics of a particular cross-section of street right-of-way were then compared against the characteristics of each bicyclist and his/her observed choice of street, sidewalk, lane, or path. Later, “route-based” serial data were also added. The study developed a mixed logit model to analyze the bicyclists’ facility preferences and capture the unobserved heterogeneity across the population. Effective sidewalk width, traffic signals, segment length, road functional class, street pavement condition, and one-way street configuration were found to be statistically significant. A bicycle path is found to be more attractive than a bicycle lane. Predictions from the model can indicate where investments in particular bicycle facilities would have the most desirable response from bicyclists. 相似文献
79.
This paper provides statistical evidence in support of the view, widely held in the tanker industry, that there are systematic differences in the degree of risk involved in investing in tankers of different sizes, and in operating tankers in spot and time charter markets. The industry view, broadly supported by the results of this paper, is that larger vessels are 'risker' assets than smaller vessels, and operating vessels in the time-charter market is less risky than employing them on a spot basis. The results are obtained by using a method derived from the financial economics literature, which models both the conditional mean and variance of a variable, known as GARCH modelling. Only one other paper has applied this method to the tanker market, and these results provide confirmatory support of those findings. 相似文献
80.
Computer Vision and Highway Automation 总被引:10,自引:0,他引:10
Ernst D. Dickmanns 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1999,31(5):325-343
A survey is given on the development of machine vision for road vehicle guidance. Through early work in real-time simulation with real hardware in the loop at UBM, and through the EUREKA-project 'Prometheus' from 1987 to 1994 following the 100 th anniversary of road vehicle developments since 1886, Europe has pioneered the field. Since first fully autonomous testdrives in 1986, and first participation in public traffic in 1992, considerable progress has been achieved. With continuous growth in computing power of microprocessors at a rate of about one order of magnitude every four to five years, sufficient performance levels for dynamic machine vision will be available within one or two decades. The principles of dynamic vision as developed at UBM and performance levels achieved are discussed. 相似文献