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   357篇
  免费   16篇
公路运输   14篇
综合类   57篇
水路运输   278篇
铁路运输   6篇
综合运输   18篇
  2024年   1篇
  2023年   2篇
  2022年   1篇
  2021年   7篇
  2020年   6篇
  2019年   11篇
  2018年   15篇
  2017年   19篇
  2016年   11篇
  2015年   19篇
  2014年   16篇
  2013年   135篇
  2012年   22篇
  2011年   21篇
  2010年   15篇
  2009年   9篇
  2008年   9篇
  2007年   12篇
  2006年   15篇
  2005年   7篇
  2004年   4篇
  2003年   2篇
  2002年   2篇
  2001年   3篇
  2000年   1篇
  1998年   1篇
  1997年   4篇
  1995年   1篇
  1992年   1篇
  1990年   1篇
排序方式: 共有373条查询结果,搜索用时 234 毫秒
271.
从滨海地区盐渍土的工程应用角度出发,利用水泥对其进行改良。通过试验研究,分析探讨了改良盐渍土抗剪、抗压强度随改良剂含量、龄期、饱水条件的变化规律,并利用电镜对改良盐渍土的强度发展机理进行了研究。试验结果表明,滨海地区盐渍土经水泥固化处理后,其抗剪、抗压强度和水稳性能得到较大程度的提高,能用作公路路基填料。  相似文献   
272.
Abstract

This introductory piece traces the growth of knowledge and activity associated with visual resource management in general. A specific framework of questions regarding methods of coastal zone visual resource management is presented. The state‐of‐the‐art in methodological studies is listed for each question, and the methodological questions are related to the major articles with the special issue of the Coastal Zone Management Journal. Major legal federal statutes, state statutes, and court cases are reviewed in light of visual resource management in the coastal zone. The remaining articles within the special issue that deal with integration of VRM into decision‐making are then arrayed against a management framework. This framework includes regulatory situations for (1) public land management and planning, (2) public projects involving private lands, and (3) public regulation of private projects.  相似文献   
273.
郭伟 《交通标准化》2013,(13):98-99
通过对渤海湾地区环境的分析,针对桥梁混凝土不同部位的腐蚀程度,设定不同的耐久性要求。通过质量跟踪,找出高性能混凝土室内和现场的性能差别与原因,为以后滨海地区的工程建设提供参考。  相似文献   
274.
Book review     
Coastal Management: Readings and Notes. Edited by Marc J. Hershman and James H. Feldmann. Institute for Marine Studies, Coastal Resources Program, University of Washington, Seattle (January 1979), 806 pp. $22.50 (paper bound).

Tobey L. Winters, Deepwater Ports in the United States: An Economic and Environmental Impact Study. N.Y. Praeger, 1977, 201 pages.  相似文献   
275.
In Frank Capra's classic film It's a Wonderful Life, a despondent man takes a journey to see what life would have been like without him: the journey paints a bleak picture. In true Hollywood form, he is ultimately reassured of his impact even though his accomplishments were immeasurable. The film's protagonist, George Bailey, is the perfect metaphor for Connecticut's Coastal Management Program. The Program can measure quantifiable elements: the number of site plans reviewed, number of permits issued, acres of tidal wetlands restored. But coastal managers often lose sight of the accomplishments and ripple effects of management, possibly because accomplishments are taken for granted. Perhaps the true value of coastal management programs lies in that intangible, immeasurable idea of what coasts would be like without them.

This article takes readers on a George Bailey–esque journey by identifying the Connecticut Coastal Management Program's accomplishments since its adoption in 1980, reviewed in the context of several questions: What if the Program had never been adopted? What would public access look like? How many acres of tidal wetlands would be lost to development or Phragmites invasion? Hopefully, the results of the exercise will put coastal management into better context and highlight the successes.  相似文献   
276.
The coastal zone has critical natural, commercial, recreational, ecological, industrial, and esthetic values for current and future generations. Thus, there are increasing pressures from population growth and coastal land development. Local coastal land use planning plays an important role in implementing the U.S. Coastal Zone Management Act (CZMA) by establishing goals and performance policies for addressing critical coastal issues. This study extends the CZMA Performance Measurement System from the national level to the local land use level by measuring coastal zone land use plan quality and political context in fifty-three Pacific coastal counties. Plan quality is measured using an evaluation protocol defined by five components and sixty-eight indicators. The results indicate a reasonable correspondence between national goals and local coastal zone land use planning goals, but a slight gap might exist between the national/state versus local levels in the overall effectiveness of coastal zone management (CZM) efforts. The results show many U.S. Pacific coastal counties lack strong coastal zone land use plans because the average plan quality score was only 22.7 out of 50 points. Although these plans set relatively clear goals and objectives, they are somewhat weaker in their factual basis, identify a limited range of the available planning tools and techniques, and establish few coordination and implementation mechanisms. The regression analysis results indicate that CZM plan quality was not significantly related to any of the jurisdictional characteristics.  相似文献   
277.
To achieve the desired outcomes of ecosystem-based or integrated coastal management, paradigm shifts must occur in all stages of the policy process. This article focuses on the evaluative stage following policy implementation, specifically on the use of coastal ecosystem condition indicators. A review of the recent literature suggests that coastal ecosystem condition indicators with too broad a scale or too narrow a scope lose utility and applicability. An analysis of these problems of scale and scope reveals that the process through which an index is designed and selected can hinder or heighten its validity. Local and diverse stakeholder input can help to ameliorate weaknesses, increasing the evaluative validity of coastal ecosystem condition indicators.  相似文献   
278.
The integration of climate change adaptation considerations into management of the coast poses major challenges for decision makers. This article reports on a case study undertaken in Christchurch Bay, UK, examining local capacity for strategic response to climate risks, with a particular focus on issues surrounding coastal defense. Drawing primarily on qualitative research with local and regional stakeholders, the analysis identifies fundamental disjunctures between generic concerns over climate change and the adaptive capacity of local management institutions. Closely linked with issues of scale, the problems highlighted here are likely to have broad and continuing relevance for future coastal management elsewhere.  相似文献   
279.
The “no net wetland loss” goal has not been met in urban coastal regions where conditions continue to exacerbate wetland losses. Under the Clean Water Act (Section 404) the U.S. Army Corps of Engineers and U. S. Environmental Protection Agency share responsibility for regulating placement of fill material in wetlands. The `no discharge of fill' rules threaten coastal wetlands with continuing losses due to effects of changing climate, including rising sea levels, higher storm surges, and flooding. Where inland migration is limited by development, or where sediment accretion rates are lower than the rate of sea level rise, urban wetlands will be lost unless marsh topography is elevated. We explored regulatory and design approaches in recent Hudson-Raritan Estuary (HRE), San Francisco Bay Estuary and coastal Louisiana restorations, including creation of new marshland using dredge material. Questions related to sea level rise, ecological position within the landscape, or potential effects of extreme storm events were not addressed in the HRE restoration designs; these concerns were taken into account in other regions. We suggest benefits of marsh `replenishment' should be acknowledged in Federal regulatory policy and that consistent policies supportive of low-lying coastal marsh preservation in all regions should be enacted.  相似文献   
280.
对于海岸工程设计波要素可以应用多种方法进行推算,最理想的还是要依据所能取得的资料来选择合适的方法。采用历史台风天气图法推算海岸工程设计波要素,以如东人工岛设计波要素推算为例,利用该方法推求不同重现期设计波要素。结果表明,在缺少长期实测风数据的情况下,选择历史台风天气图推算法能推算工程区设计波要素,从而为工程提供设计依据。  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