全文获取类型
收费全文 | 1143篇 |
免费 | 18篇 |
专业分类
公路运输 | 372篇 |
综合类 | 40篇 |
水路运输 | 384篇 |
铁路运输 | 36篇 |
综合运输 | 329篇 |
出版年
2023年 | 4篇 |
2022年 | 27篇 |
2021年 | 6篇 |
2020年 | 5篇 |
2019年 | 12篇 |
2018年 | 39篇 |
2017年 | 33篇 |
2016年 | 35篇 |
2015年 | 8篇 |
2014年 | 52篇 |
2013年 | 184篇 |
2012年 | 64篇 |
2011年 | 67篇 |
2010年 | 62篇 |
2009年 | 49篇 |
2008年 | 50篇 |
2007年 | 32篇 |
2006年 | 26篇 |
2005年 | 28篇 |
2004年 | 14篇 |
2003年 | 21篇 |
2002年 | 19篇 |
2001年 | 21篇 |
2000年 | 11篇 |
1999年 | 15篇 |
1998年 | 22篇 |
1997年 | 19篇 |
1996年 | 25篇 |
1995年 | 14篇 |
1994年 | 8篇 |
1993年 | 12篇 |
1992年 | 15篇 |
1991年 | 11篇 |
1990年 | 12篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1986年 | 4篇 |
1985年 | 8篇 |
1984年 | 9篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 13篇 |
1980年 | 13篇 |
1979年 | 16篇 |
1978年 | 9篇 |
1977年 | 8篇 |
1976年 | 9篇 |
1975年 | 9篇 |
1974年 | 5篇 |
1973年 | 6篇 |
排序方式: 共有1161条查询结果,搜索用时 131 毫秒
781.
Abstract local wastewater management policies can be important tools for protecting marine water quality when coordinated with sound land use and environmental planning. that relationship is examined through a review of the point and nonpoint source pollution issues associated with centralized versus decentralized wastewater management approaches, sewerage extension and plant expansion effects, and sewerage management practices. we use information provided by 161 local jurisdictions in coastal regions of the southeastern united states and various secondary regions of the southeastern united states and various secondary sources. the article concludes with a discussion of policy implications and recommendations to improve the coordination of local sewerage extension/expansion practices and land use planning. 相似文献
782.
Abstract Section 312 of the Clean Waters Act was implemented in 1980 and requires all vessels including recreational boats already equipped with Marine Heads (toilets) to install one of three types of USCG approved Marine Sanitation Devices. These regulations govern all lakes and coastal waters extending to the end of the U.S. territorial sea and is intended to prevent untreated effluent from reaching the marine environment. As provisions of the Clean Water Act are exempt from provisions of the National Environmental Policy Act, no Environmental Impact Statement was written concerning the impacts to the marine environment and the cost to the boating public. The study based on a small survey conducted on Narragansett Bay during the summer of 1980 develops several empirical models to estimate the total costs of MSD conversions. These estimates assume that all recreational boats longer than 21 feet were to comply with Section 312 regulations. Biological Oxygen Demand generated waste by both the resident and visiting fleets have also been estimated and costs per lbs. of BOD equivalent made. Based on these estimates the quantity of waste prevented from entering the receiving waters equals that of a community with less than 700 people. The capital investments of on‐board treatment approximates 30 ¢/gallon, nearly 1000 times the cost of treating municipal waste. 相似文献
783.
The choice behaviour of low cost travel (LCT) modes is very sensitive to travel distance. A line haul system designed on the basis of current planning practice of locating widely spaced stations to cater auto and bus feeder modes with the primary objective of gaining travel speed is hostile to non‐motorized and low cost feeder modes. With the revival of interest in promoting the use of walk'n ride and bike'n ride modes, there is a need to develop an appropriate tool to examine the effect of their specific characteristics in establishing the number and location of stations. A generic normative behavioural hybrid model for locating the cost minimizing number and location of stations is developed for an LCT‐fed line haul system. The model considers the system with many to many two dimensional line haul demand density function in which the density varies in both x‐ and y‐directions. The feeder mode choice behaviour is incorporated in the model by integrating probability‐access/egress distance function with the objective function. Explicit functional relationships among the parameters of these feeder modes such as modal share as a function of access/egress distance with the parameters of line haul systems are developed. Dynamic programming is used to minimize the system cost. The generic model is shown to collapse into several simplified models capable of yielding approximate solutions for several well known special cases. It has been shown that location of stations is sensitive to the through load on board as well as users’ cost that defines the choice behaviour at large. Numerical examples are presented to demonstrate the applicability of the model. 相似文献
784.
785.
Abstract Designing environmental monitoring programs to deal with widespread, subtle, and/or cumulative impacts on a regional basis is challenging. It requires a shift away from focusing primarily on individual point sources to a more regional perspective. It also necessitates involving scientists and managers together in a cooperative effort to establish priorities and articulate clear objectives. In our view, this objective‐setting task is neither a strictly scientific nor a strictly management activity. It depends on effective communication between scientists and managers but is confounded by differing perspectives, value systems, and behaviors. We present a conceptual framework to assist managers and scientists in this process. This is intended to structure such communication by helping to create a context that permits fruitful give‐and‐take between the two groups. We then describe a six‐part model for specifying the key elements of regional monitoring objectives. 相似文献
786.
Abstract Over 90 percent of British Columbia's annual log harvest enters into complex water‐based systems of transportation, storage, and handling. These systems have considerable impacts on a wide range of coastal resources and uses. A number of site‐specific conflicts have arisen between forestry and preexisting or emerging values including fisheries, mariculture, recreational boating, and harbor redevelopment. Specific data on the impacts leading to conflict are often fragmentary. However, concerns about highly valued and fragile areas‐particularly estuariesalong with industrial concerns regarding log losses and handling efficiency, have prompted changes in log handling. These include moves to dryland sorting, log bundling, and a redistribution of forestry activities in estuaries to accommodate other values. Conflict adjustments and responses have in the past been largely ad hoc and attempted in a jurisdictional vacuum concerning control of coastal management. A more inclusive strategy is now slowly emerging, which involves the coordinated participation of federal, provincial, and industrial interests. 相似文献
787.
C. A. Nash 《运输评论》2013,33(4):383-384
Improving Railway Financial Performance. By M. E. Beesley and P. B. Kettle. (Aldershot: Gower, 1985.) [Pp. 108.] £15–00. 相似文献
788.
789.
J. C. Sutton 《运输评论》2013,33(2):167-182
The changing role of Dial‐a‐Ride systems in the period 1969 to 1985 is reviewed as a case study in transport innovation. The first phase Dial‐a‐Ride systems were conceived and planned as transport services to complement and even replace conventional transit. However, their failure to attract any sizeable part of the public transport market combined with their high operating costs led to their demise in the mid‐1970s, to be superseded by the second phase Dial‐a‐Ride systems as paratransit services to the elderly and handicapped. These later systems were often initiated by community‐based transport agencies which have demonstrated their ability as transport innovators in meeting passenger needs. It is suggested that other transport services could learn valuable lessons from the experiences of community Dial‐a‐Ride, and that Dial‐a‐Ride itself will prove historically to be an important transitional agent in the reorganization of passenger transport services in the post‐deregulation environment of the late 1980s and 1990s. 相似文献
790.
Abstract An analysis of ecological systems that both sustain and are sustained by coastal waters provides the key to a biophysical procedure for delineating inland coastal management boundaries. This analysis entails two basic tasks: (1) mapping the ecosystems that compose coastal waters and adjacent areas, and (2) charting sustaining flows among these systems. The resulting boundary encompasses all environments of coastal waters (subaqueous areas containing a measurable quantity of seawater) and all shore‐lands (either emergent or submergent environments that interchange sustaining materials, energy, or biota with coastal waters). As this biophysical procedure depends on the precise location of, and functional transfers among, coastal ecosystems, it provides a means both for assessing the consequences of human actions and for establishing a landward boundary for a management program. Alternative boundaries not based on locations and operations of coastal ecosystems would probably be either arbitrary or of undue extent, nor would such “alternative”; boundaries be an integral part of an ongoing management process. 相似文献