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   66篇
  免费   5篇
  国内免费   26篇
测绘学   1篇
大气科学   1篇
地球物理   4篇
海洋学   84篇
综合类   7篇
  2024年   1篇
  2023年   2篇
  2022年   3篇
  2021年   3篇
  2020年   1篇
  2019年   3篇
  2018年   3篇
  2017年   5篇
  2016年   5篇
  2015年   4篇
  2014年   6篇
  2013年   6篇
  2012年   5篇
  2011年   2篇
  2010年   2篇
  2009年   1篇
  2008年   8篇
  2007年   3篇
  2006年   5篇
  2005年   6篇
  2004年   9篇
  2003年   2篇
  2002年   2篇
  2001年   2篇
  2000年   5篇
  1999年   1篇
  1997年   1篇
  1996年   1篇
排序方式: 共有97条查询结果,搜索用时 15 毫秒
21.
22.
23.
Interannual coupled Rossby waves in the extratropical Indian Ocean propagate westward in covarying pycnocline depth, sea surface temperature, and meridional surface wind anomalies from the west coast of Australia between 15°S and 35°S, taking 3–4 years to transit the interior ocean to Madagascar. In the interior subtropical gyre, where the tuna longline catch (TLC) mainly concerns two species (albacore and bigeye), these waves have been observed to affect year-to-year changes in catch, with wave crests (troughs) in the main pycnocline associated with high (low) TLC anomalies. This suggested that tuna longline catch is associated with the entrainment of nutrient-rich pycnocline water into the photic zone and a subsequent increase in primary productivity there. Here, this hypothesis is examined within the context of SeaWiFS chlorophyll concentration (CC). We find the situation the opposite of that expected, with wave crests (troughs) in the main pycnocline associated with low (high) CC anomalies averaged over the photic zone. These results are shown to be consistent with a model relating the anomalous CC tendency to upper-layer divergence in the wave, not unlike that relating surface slicks to upper-layer divergence in internal gravity waves. Thus, the connection between interannual coupled Rossby waves and TLC in the interior subtropical gyre does not appear to derive from wave-induced modulation of the pelagic food web. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   
24.
大眼金枪鱼的资源现状   总被引:4,自引:0,他引:4  
大眼金枪鱼的分布很广 ,在南、北纬 4 0°以内的太平洋、印度洋和大西洋均有分布 ,是金枪鱼渔业的重要捕捞种类之一。本文分别论述了大眼金枪鱼在大西洋、印度洋和太平洋的渔业概况、生物学特性、资源状况和管理对策。  相似文献   
25.
根据已开发鱼类种群的自然死亡率(M)在鱼类资源评估中的重要作用,讨论了1种应用实际种群分析(VPA)(亦即世代分析方法)估算鱼类自然死亡率的方法.文中假设了捕捞努力量(E)已知和未知2种情况,并同时求出了其他种群参数,如可捕系数,补充量等.在蒙特卡罗模拟分析中,假设了4种模拟渔业(管理良好的渔业,掠夺式渔业,恢复性渔业和稳定性渔业)对该方法进行了验证.并将von-Bertalanffy生长方程(VBGF)引入VPA模型来估算鱼类的自然死亡率.当CV等于20%时,在4种模拟渔业中鱼类各龄自然死亡率(Ma)的EP均小于10%.在已知单位捕捞努力量渔获量数据时,计算北大西洋长鳍金枪鱼(Thunnus alalunga)的M等于0.119,这个结果比先前假定的值(0.3)小,但考虑到该鱼种所承受的高的捕捞压力作者认为该估计值是合理的.  相似文献   
26.
27.
分析比较两种不同结构的延绳钓渔具 1998年 2~ 9月期间在印度洋东部作业的生产效果。结果显示 ,钓具 A(平均放钓水深 90 .8m)与钓具 B(平均放钓水深 72 .7m)相比 ,钓捕效果差异显著 ,在渔获尾数、渔获重量、上钓率三个指标上 ,A钓具分别高于后者 2 9.52 %、30 .2 1%和9.80 %。提出了符合印度洋生产需要的钓具优化设计方案。  相似文献   
28.
In recent decades there has been steady progress towards a risk-based management approach for fisheries. An important first step in a risk analysis framework is scoping to identify, describe and catalog the sources of uncertainty that might have an impact on a fishery. This paper introduces a methodology based on a range of tools to formalize the process of elicitation of uncertainties, from both experts and stakeholders, for the International Commission for the Conservation of Atlantic Tunas (ICCAT). ICCAT is a regional fisheries management organization responsible for the conservation of tunas and other highly migratory fish in the Atlantic Ocean and its adjacent seas. The aim of the elicitation was to identify and prioritize uncertainties for inclusion in Operating Models for Management Strategy Evaluation (MSE). The tool presented in this paper supports the qualitative prioritization of uncertainties, while also visualizing the degree of consensus among stakeholders on particular issues. Perceptions of uncertainty in fisheries often vary widely among scientists, industry and other interest groups, so tools that can facilitate inclusion and representation of different opinions are useful where decision-making depends on broad agreement and more generally, where effective management depends on commitment from stakeholders.  相似文献   
29.
In the western and central Pacific Ocean, upper strata waters exhibit highly dynamic oceanographic features under ENSO variability. This has been proved to be responsible for the dynamic change of both abundance and zonal distribution of skipjack tuna(Katsuwonus pelamis). Although causality has been suggested by researchers using physical–biological interaction models, cumulative evidence needs to be obtained and the tenability of assertion needs to be tested from an ecological habitat perspecti...  相似文献   
30.
The Western and Central Pacific Ocean is home to the world's most productive tuna fisheries, with the majority of tuna catches occurring inside the exclusive economic zones (EEZs) of the region's developing coastal States. It is important that these fisheries are managed effectively throughout their range, both within and between EEZs and on the high seas. Unrestrained exploitation in a particular EEZ or on the high seas has the potential to significantly impact on catches elsewhere with potentially devastating consequences for developing coastal States, some of which have few alternate resources. The Western and Central Pacific Fisheries Commission (WCPFC) was established in 2004 to manage the region's highly migratory tuna fisheries. However, the WCPFC has since repeatedly failed to adopt conservation and management measures that are sufficient to meet the WCPFC's conservation and sustainable use objectives. This paper analyses catch data from the WCPFC and suggests that the weak position of bigeye (in a strategic political context), the unwillingness of members to compromise their interests and the lack of a transparent framework for distributing the burden of conservation are key factors in the WCPFC's failure to adopt sufficiently strong conservation and management measures.  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