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   89篇
  免费   4篇
  国内免费   4篇
测绘学   19篇
大气科学   14篇
地球物理   11篇
地质学   24篇
海洋学   16篇
天文学   5篇
综合类   1篇
自然地理   7篇
  2021年   1篇
  2020年   1篇
  2019年   2篇
  2018年   1篇
  2017年   2篇
  2016年   7篇
  2015年   3篇
  2014年   7篇
  2013年   3篇
  2012年   4篇
  2011年   12篇
  2010年   3篇
  2009年   7篇
  2008年   7篇
  2007年   4篇
  2006年   7篇
  2005年   5篇
  2004年   2篇
  2003年   3篇
  2002年   6篇
  2001年   6篇
  2000年   2篇
  1997年   1篇
  1995年   1篇
排序方式: 共有97条查询结果,搜索用时 0 毫秒
71.
测量工作中,经常需要进行不同椭球下的高斯投影正算、反算与换带计算,如果用手工完成,不仅计算量庞大,而且容易出错。文中首先介绍了高斯投影的公式,然后利用Access在处理批量数据的优势,结合VBA编写了计算程序,实现了任意椭球下的高斯投影正算、反算与邻带坐标换算的单点和批量计算。通过实例验证了程序的准确性及实用性,可以满足工程需要。  相似文献   
72.
The declaration of exclusive economic zones (EEZs) granted coastal states sovereign rights over the marine resources in their EEZs and enabled developing coastal states to legally charge access fees to distant water fishing (DWF) nations for access to the resources in these waters. Despite the potential for economic gains, however, the ability of coastal states to benefit from the granting of sovereign rights and to ensure the sustainable use of their fisheries resources depends on how domestic fishing effort responds to the harvesting decisions of the DWF nations. We develop a stylized bioeconomic model to explore the change in fishing behavior of host and DWF nations when the two nations enter into an access agreement with varying levels of access fee. We further conduct an econometric analysis of changes in Pacific island nations’ harvesting behavior in response to the harvest decisions of DWF nations using data from the Western and Central Pacific tuna fishery. Our model results show that there is a range of variable access payment levels over which the host nation substitutes benefits from its domestic fishing activity with access payments from the DWF nation and that setting fees in this range can create a trap whereby host nations are forced to trade-off receiving a fair return to their fishery resources through access fees and retaining their own active fleet capacity. Our empirical analysis further shows a gradual shift in the way in which Pacific island host nations responded to the harvest decision of DWF nations as a result of the creation of the 200-nautical-mile EEZ.  相似文献   
73.
In Zambia’s Copperbelt as in most of the developing world, the water sector is undergoing reforms targeted at promoting an active participation of the private sector. Conventional wisdom suggests that the private sector will be better able to achieve universal access as opposed to the public sector which hitherto has failed to deliver. Using archival materials from the Copperbelt Province, this paper however argues that in countries like Zambia where economic enterprise was driven by private capital, access to water has always been tied to an active involvement of the private sector. The full story of failure to provide universal access to potable water cannot be told without examining this historical role of the private sector and its relationship with the public sector. At the same time, contemporary policy debates can benefit from the resonance of historical debates around economic efficiency, demand management, health and access in the production and consumption of water.  相似文献   
74.
地下管线信息管理系统建成后,进行数据更新以保证各类管线的现势性和准确性是该项建设后续的棘手问题.地下管线竣工测馈是对地下管线信息管理系统数据更新的一个重要手段.结合<宁波市地下管线探测技术规程>,叙述地下管线竣工测量前端数据采集系统开发的原理和方法,保证竣丁更新管线的数据质量,提高工作效率.  相似文献   
75.
Tsunami boulders deposited along the coast constitute important geological evidence for paleotsunami activity. However, boulders can also be deposited by large storm waves. Although several sedimentological and theoretical methods have been proposed to differentiate tsunami and storm wave affected boulders, no appropriate numerical method exists for their differentiation. Therefore, we developed a new numerical scheme to differentiate tsunami and storm wave boulders for coastal boulders on Ishigaki Island, Japan. In this area, tsunami and storm waves have emplaced numerous boulders on the reef and the coast. By conducting numerical calculations of storm waves in this region, we estimated the size of a storm wave that can explain the maximum clast size distribution of boulders on the reef. Consequently, we showed that a wave with a combination of 8 m in initial wave height and 10 s period can satisfy the above conditions when we assume mean sea level. In contrast to the boulders on the reef, all boulders deposited along the shore are heavier than the calculated possible maximum clast size distribution by the storm wave. Therefore, we confirmed these boulders as being of tsunami origin. Results of previous studies showed that they were most likely deposited or reworked by the 1771 Meiwa tsunami. Then, using the tsunami boulders, we numerically estimated the wave period and amplitude of the 1771 Meiwa tsunami, which should have had a 4–5 min period and 5.6–5.9, 6.3–7.0 m amplitude, respectively. Using the proposed scheme, it is possible to differentiate tsunami and storm wave boulders and estimate the size of past storm waves and tsunami waves, although it is noteworthy that there are exceptions for which the scheme cannot be applied.  相似文献   
76.
The Marine and Coastal Access Bill, when it becomes law, may well be considered a welcome addition to the legislation protecting the marine coastal environment. It is argued, however, in this paper that the Bill could have addressed a number of issues including the matter of shipowners’ privileges, locus standi, the designation and setting up of an environmental fund, and the difficulties associated with places of refuge for vessels in distress.  相似文献   
77.
中国虚拟天文台数据访问服务   总被引:1,自引:1,他引:1  
随着科学技术的进步和大批天文观测项目的实施,天文数据正在呈现爆炸式的增长,天文学正进入一个数据富庶的时代。虚拟天文台项目的首要目标就是要解决这些高度分散、复杂、海量的天文数据的统一访问和管理,实现全球天文数据资源的融合,使天文学家能够高效快捷的获取所需的天文数据。中国虚拟天文台项目基于目前的网格技术,设计和实现网格环境下天文数据的查询访问服务,并为客户应用提供统一的访问接口。本文重点介绍了我们采用GlobusToolkit网格开发工具包,按照国际虚拟天文台联盟最新制订的天文数据标准,完成对天文星表数据资源的网格服务封装,实现天文星表锥形查询(Cone Search)和星表查询网格两个数据服务的工作,并介绍了如何使用天文数据服务搭建其他网格服务。  相似文献   
78.
This paper reports on three-dimensional reconstruction of the Yaolin Cave in the Karst Region of Zhejiang, China. An object-oriented method was used to represent two cave classes—the class Boundary and the class Inside. The class Boundary included objects of the cave ceiling and the cave floor which are part of the topographical trend of the cave. This trend was determined by integrating topography with landform using TIN modeling. The inside of the cave with stalagmites, stalactites, dripstone-columns, and other objects was built using surveying data, photographs, and such computer graphics techniques as texture mapping and transparency. A stand-alone, 3-D visualization system—Cave3D—was developed on the Windows 98/NT platform to produce 3-D graphics and implement graphics-based computation, spatial query, and analyses. A virtual Yaolin cave was created using VRML97 and Java and posted on the Web.  相似文献   
79.
Roman Grynberg   《Marine Policy》2003,27(6):499-511
The paper considers the WTO negotiations on fisheries subsidies and the implications that envisaged disciplines will have on coastal developing countries. This is considered in relation to fisheries access agreements in the Central and Western Pacific where several least developed but resource rich island states such as Kiribati and Tuvalu are highly exposed to the risks associated with new WTO fisheries subsidies disciplines that do not consider their particular vulnerabilities. The paper considers some of the issues that coastal developing countries should incorporate into their emerging negotiating positions at the WTO. State-to-Sate fisheries access agreements which are often highly subsidised but where fishing vessel owners pay the equivalent of lump sum tax are paradoxically, the least distortionary and damaging to the environment. Strategies for managing the possible new disciplines are considered.  相似文献   
80.
给出一种用RAM扩充程序存贮器的方法,以及具体的硬件线路。这种简便实用的方法可为用户提供一种根据需要自行修改或编写应用程序的环境.  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