全文获取类型
收费全文 | 3944篇 |
免费 | 28篇 |
专业分类
公路运输 | 1198篇 |
综合类 | 141篇 |
水路运输 | 1262篇 |
铁路运输 | 130篇 |
综合运输 | 1241篇 |
出版年
2023年 | 17篇 |
2022年 | 58篇 |
2021年 | 37篇 |
2020年 | 33篇 |
2019年 | 37篇 |
2018年 | 110篇 |
2017年 | 101篇 |
2016年 | 156篇 |
2015年 | 48篇 |
2014年 | 133篇 |
2013年 | 619篇 |
2012年 | 205篇 |
2011年 | 207篇 |
2010年 | 174篇 |
2009年 | 188篇 |
2008年 | 185篇 |
2007年 | 126篇 |
2006年 | 79篇 |
2005年 | 82篇 |
2004年 | 65篇 |
2003年 | 61篇 |
2002年 | 59篇 |
2001年 | 64篇 |
2000年 | 65篇 |
1999年 | 51篇 |
1998年 | 72篇 |
1997年 | 59篇 |
1996年 | 67篇 |
1995年 | 87篇 |
1994年 | 41篇 |
1993年 | 43篇 |
1992年 | 41篇 |
1991年 | 35篇 |
1990年 | 30篇 |
1989年 | 27篇 |
1988年 | 40篇 |
1987年 | 36篇 |
1986年 | 30篇 |
1985年 | 33篇 |
1984年 | 34篇 |
1983年 | 24篇 |
1982年 | 34篇 |
1981年 | 41篇 |
1980年 | 37篇 |
1979年 | 49篇 |
1978年 | 26篇 |
1977年 | 29篇 |
1976年 | 19篇 |
1975年 | 28篇 |
1974年 | 22篇 |
排序方式: 共有3972条查询结果,搜索用时 0 毫秒
991.
Contained herein are the results of research which quantifies the effects that various existing and projected truck configurations have as live loadings upon bridges which currently exist on the National Bridge Inventory (NBI). The truck configurations were determined from those actual or proposed vehicles which exhibit the highest GVW and which either are causing or are perceived to cause the highest levels of overstress on bridge superstructure elements. In order to simulate most accurately the actual field conditions, a criterion was defined which contained three major requirements: 1) The bridges utilized within the study shall be defined as being a statistically significant sample and be actual bridges taken from the NBI; 2) The analysis method shall be consistent with those actually used by engineers in designing and rating bridges, and; 3) The criteria utilized in evaluating the various bridge structures under the defined loadings shall be consistent with current practices. The results obtained indicates the acceptability of various truck configurations by GVW, size, and axle deployments, by system for the different criteria now in use. 相似文献
992.
Kuo-Shian Lin Debbie A. Niemeier 《Transportation Research Part D: Transport and Environment》1998,3(6):375-387
The commonly used photochemical air quality model, the Urban Airshed Model (UAM), requires emission estimates with grid-based, hourly resolution. In contrast, travel demand models, used to simulate the travel activity model inputs for the transportation-related emissions estimation, typically only provide traffic volumes for a specific travel period (e.g. the a.m. and p.m. peak periods). A few transportation agencies have developed procedures to allocate period-based travel demand data into hourly emission inventories for regional grid cells. Because there was no theoretical framework for disaggregating period-based volumes to hourly volumes, application of these procedures frequently relied upon a single hypothetical hourly distribution of travel volumes. This study presents a new theoretical modeling framework that integrates traffic count data and travel demand model link volume estimates to derive intra-period hourly volume estimates by trip purpose. We propose a new interpretation of the model coefficients and define hourly allocation factors by trip purpose. These allocation factors can be used to disaggregate the travel demand model ‘period-based’ simulation volumes into hourly resolution, thereby improving grid-based, hourly emission estimates in the UAM. 相似文献
993.
Transportation - Historically cities are formed to provide interaction and communication opportunities for communities. As cities become smarter, new forms of interactions are formed and the... 相似文献
994.
Encouraging pro-environmental behavior among protected area visitors and other stakeholders has become a priority for marine resource managers. However, there exists a lack of understanding of the human dimensions of resource management regarding the perceptions and attitudes of stakeholders. Using the value-belief-norm theory of environmentalism (VBN) as a framework, the purposes of this investigation were to: 1) test a model of variables that influence stakeholders' intentions to adopt pro-environmental behavior in two marine protected areas (i.e., the Great Barrier Reef Marine Park and the Florida Keys National Marine Sanctuary); and 2) using the relevant literature and information gleaned from the model, suggest techniques that managers can use to encourage pro-environmental intentions. Acceptable goodness-of-fit indices for both of the structural equation models (one for each protected area) provided empirical support for the usefulness of the VBN framework to guide both research in marine contexts and marine protected area management efforts to encourage stakeholders' intentions to engage in pro-environmental behavior. Specific suggestions include increasing stakeholders. knowledge about impacts via environmental education strategies, increasing their awareness of their impacts and their efficacy in mitigating those impacts (e.g., workshops), and developing interpersonal relationships among managers and stakeholders (e.g., implementation intention and follow-up strategies). 相似文献
995.
996.
997.
Vanessa J. Maxwell John Supan Lisa C. Schiavinato Stephanie Showalter Granvil D. Treece 《Coastal management》2013,41(3):241-253
The goal of this study is to apply industrial park concepts to the development of aquaculture parks in public waters. The objectives are to identify the permitting process, relevant agencies, and legislation needed to facilitate development. Gulf of Mexico states are surveyed: private parks exist in Florida, but no public parks have developed yet; plans for parks exist in Mississippi, but lack of funding prevents development; no regulations prohibit parks in Alabama, although none currently exist; Texas regulations hinder development of parks; and an experimental park has been proposed in Louisiana, but regulatory gaps have delayed permit issuance. 相似文献
998.
The twin forces of rising affluence and population are altering coastal communities around the world. High amenity, environmentally sensitive areas—particularly attractive, non-metropolitan coastal environments—are witnessing a tidal wave of in migration from former urbanites. As a result, these communities are struggling to accommodate growing numbers of people with urban tastes and rural dreams in areas with governance structures and physical infrastructure designed for occasional tourists. This article looks at how governance frameworks in coastal Australia respond to the profound environmental, social, and cultural implications of this process. We offer a typology of non-metropolitan coastal growth settings—from exurban contexts to isolated coastal hamlets—and identify the main environmental, social, economic, and governance issues they face. We then outline the policy and legislative framework governing coastal areas in Australia and show how this framework is interpreted at the local level through an analysis of five local plans covering different coastal settings. 相似文献
999.
1000.
R.J. O'brien 《Coastal management》2013,41(3):201-214
Abstract Western Australia is fortunate that there have been few natural disasters on the coast. However, low levels of coastal erosion during the 1970s demonstrated the need to establish coastal zone management in that state of Australia. The erosion was quickly contained because private ownership to the high water mark is almost nonexistent, private property being set back behind coastal reserves along most of the coast. The provision of coastal reserves has been part of a deliberate nonstatutory coastal planning and management approach. As a result Western Australia has been able to use existing acts, coordination between existing government agencies, and coastal policies rather than enact specific coastal legislation to manage the coast. 相似文献