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   7926篇
  免费   104篇
公路运输   1739篇
综合类   588篇
水路运输   2527篇
铁路运输   765篇
综合运输   2411篇
  2022年   112篇
  2021年   59篇
  2020年   45篇
  2019年   84篇
  2018年   194篇
  2017年   110篇
  2016年   145篇
  2015年   90篇
  2014年   241篇
  2013年   1221篇
  2012年   325篇
  2011年   398篇
  2010年   249篇
  2009年   366篇
  2008年   305篇
  2007年   268篇
  2006年   230篇
  2005年   269篇
  2004年   289篇
  2003年   179篇
  2002年   149篇
  2001年   132篇
  2000年   139篇
  1999年   98篇
  1998年   130篇
  1997年   111篇
  1996年   140篇
  1995年   149篇
  1994年   84篇
  1993年   189篇
  1992年   160篇
  1991年   77篇
  1990年   83篇
  1989年   57篇
  1988年   74篇
  1987年   65篇
  1986年   59篇
  1985年   77篇
  1984年   73篇
  1983年   73篇
  1982年   73篇
  1981年   95篇
  1980年   68篇
  1979年   91篇
  1978年   56篇
  1977年   69篇
  1976年   53篇
  1975年   65篇
  1974年   50篇
  1973年   45篇
排序方式: 共有8030条查询结果,搜索用时 15 毫秒
111.
Anecdotal evidence indicates that commercial and recreational water-dependent uses have been under development pressure in recent years, and in some cases have been converted to other uses. The conversion of water-dependent uses, which range from commercial shipyards to recreational marinas, may have many public costs, including the loss of access to public trust waters, the loss of jobs and associated economic activity, and the loss of traditional working waterfronts. This two-part study investigated the role of five coastal management programs in the northeastern United States in managing, monitoring, and protecting water-dependent uses. First, coastal managers in Massachusetts, Rhode Island, Connecticut, New York and New Jersey were interviewed to assess the conversion problem. Second, in collaboration with New York City-based Regional Plan Association, follow-up interviews were conducted with coastal managers and local planners in Connecticut, New York, and New Jersey to gain greater insight into the role of coastal management programs and local governments in managing and promoting water-dependent uses. This article presents select findings from this study and discusses recommendations for improving the capacity of coastal management programs and local governments to manage water-dependent uses for the benefit of the public.  相似文献   
112.
Green turtles (Chelonia mydas) are among the most high profile species in San Diego Bay, California, and understanding impacts of coastal development and industry is essential to the management and conservation of this local population. Here we describe power plant changing energy production and its impact on turtle habitat use and our ability to research and manage this population. For over 20 years, green sea turtles have been captured, assessed, and tagged near the South Bay Power Plant (SBPP) in the San Diego Bay; from 2002–2011, 104 turtles were captured on 212 occasions. As the 50-year-old SBPP generates less energy, effluent patterns change and water temperatures decrease, presumably to more natural conditions. There has been a concurrent decrease in turtle-capture success, perhaps due to lesser visitation to the effluent site where nets are tended. Seasonal catch-per-unit-effort declined from a high of 4.14 turtles per monitoring day, to a nine-year low of 1.33 during the 2010–2011 season. It is already apparent that management decisions related to energy policy are affecting the habitat and behavior of this stock of endangered turtles. Green turtles are expected to remain in the San Diego Bay after the SBPP becomes inoperative and continuing research will monitor future impacts and distribution shifts resulting from the expected changes in thermal pattern within south San Diego Bay. Research efforts to study this population (i.e., capture methods and locations) will require modification in response to these changes. Lessons learned here are applicable to the immediate coastal development of San Diego, as well as at similar interactions between marine turtles and industrial thermal effluent discharge throughout Southern California, the United States, and beyond.  相似文献   
113.
Book reviews     
Coastal Resources Management: Beyond Market and Bureaucracy by Robert B. Ditton, John L. Seymour, and Gerald C. Swanson. Published by D. C. Heath and Company, Lexington, Massachusetts, 1977, 191 pp., 6 figures.

The Urban Sea: Long Island Sound by Lee E. Koppelman, Peter K. Weyl, M. Grant Gross, and DeWitt S. Davies. Published by Praeger Publishers, 1976. 209 pp., 81 figures, 42 tables.  相似文献   
114.
The Bay Conservation and Development Commission (BCDC), has designated a number of shoreline sites around San Francisco Bay for exclusive use of water‐related industry. This is intended both to reduce future needs for Bay fill, and to reserve those waterfront sites needed for long‐term industrial growth. The Commission currently defines water‐related industries as those “requiring”; a shoreline site for water transportation. The Commission is now considering the use of an economic criterion for identifying water dependency. This involves comparisons of the uniquely water‐related benefits and costs to the firm to locate on the shoreline, as opposed to its location at an inland site. By limiting use of deepwater sites to those industries that are significantly water‐dependent under this criterion, long‐term economic efficiency is served, and the need for future Bay fill for industrial growth is reduced. The data and analysis required to implement an economic water‐dependency criterion do not appear to be a barrier to use of such a test in the regulatory process. Whereas water dependency is an important concern to BCDC, other factors, including environmental constraints, must also be weighed when evaluating industrial projects.  相似文献   
115.
116.
Abstract

Risk from the “natural event system”; of hurricanes varies greatly along the U.S. coastline, and so do the property and lives at risk. Damage potential from storm surge in the Miami area is less than a third that of the Tampa area. However, damage potential from winds in the Boston and New York areas exceeds that of either the Miami or Tampa areas. Passage of time since the great hurricane disasters near the turn of the century and improvements in the warning system may make coastal dwellers underestimate the likelihood of a hurricane catastrophe. But population growth near the coast has been more than three times the national average, and 10 of 58 coastal segments 50 miles in width more than doubled in population between 1960 and 1970. Twenty‐two segments increased by more than 25,000 people with six increasing by 150,000. Legislative response to the growing hazard has varied as widely as risk but is not clearly correlated with risk.  相似文献   
117.
Abstract

Most federal and state coastal laws were framed with a distinct emphasis on preservation of rural/recreational areas. Yet in recent years a rural/urban coastal dichotomy has emerged. This has been especially prominent in the siting of energy facilities since these operations are often water dependent; power plants, for example, need huge amounts of cooling water, and offshore oil and gas extraction requires onshore support facilities. Recently, this issue has gained special prominence on the East Coast with the commencement of offshore oil and gas exploration. A case study was conducted in Hudson County, New Jersey, in New York harbor. In this area five oil‐related facility proposals were rejected from 1972 to 1976, primarily due to citizen opposition. Citizen activists now see the urban waterfront as a special place to which they want access and amenity uses rather than a continuation of past, almost exclusive industrial development. Hudson County citizens share the aspirations of those in several urban coastal areas which have experienced waterfront revitalization, including Baltimore, Boston, Chicago, Detroit, New Haven, Philadelphia, San Francisco, Seattle, and Toronto. Innovative siting which utilizes inland, rather than coastal, locations is suggested as one way to lessen urban/rural siting tensions.  相似文献   
118.
This article reviews the historical development of the category of national park known as “national seashore,”; and traces the evolution of basic planning and management policies that are applied to such areas. Also reviewed is the current sequential approach applied by the National Park Service in all its planning efforts, including a discussion of the impact of the National Environmental Policy Act on park planning. Several examples are provided to illustrate a variety of planning problems common to the sashore environment. Finally, comments are provided on the future promise of seashore and barrier island conservation and development, as well as the future role of other agencies and private organizations.  相似文献   
119.
120.
Abstract

The coastal setback line program in Florida represents an effort to achieve more efficient location decisions, protect beachfront properties from storms, and control beach erosion. This article examines the reasons why the regulation of shoreline development might be necessary, describes the coastal setback program in Florida, discusses some of the problems encountered in its implementation, and examines its potential success.  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