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   100篇
  免费   18篇
  国内免费   19篇
测绘学   2篇
大气科学   1篇
地球物理   16篇
地质学   18篇
海洋学   80篇
综合类   6篇
自然地理   14篇
  2024年   1篇
  2023年   2篇
  2022年   1篇
  2021年   2篇
  2020年   4篇
  2019年   4篇
  2018年   5篇
  2017年   2篇
  2016年   9篇
  2015年   1篇
  2014年   8篇
  2013年   5篇
  2012年   4篇
  2011年   4篇
  2010年   2篇
  2009年   10篇
  2008年   10篇
  2007年   6篇
  2006年   1篇
  2005年   3篇
  2004年   5篇
  2003年   6篇
  2002年   7篇
  2001年   2篇
  2000年   4篇
  1999年   2篇
  1998年   6篇
  1997年   1篇
  1996年   5篇
  1995年   3篇
  1994年   11篇
  1992年   1篇
排序方式: 共有137条查询结果,搜索用时 24 毫秒
1.
根据长山群岛 1965-2016 年渔业统计资料,分析长山群岛海域主要捕捞渔获物产量、平均营养级 (Mean trophic level, MTL)、渔业均衡指数 (Fishing in balance index,FiB) 年际变化,探讨其海洋渔业资源利用状况,并利用小波分析方法研究52年来渔获物 MTL 周期变化特征。研究表明: (1) 长山群岛捕捞产量、MTL 和 FiB 指数呈阶段性变化; (2) 长山群岛渔业资源开发经历初期开发、扩张捕捞、过度捕捞、资源破坏等四个阶段,渔业资源环境正在逐渐恶化;(3) 受人类捕捞活动影响,MTL 在 15~19 年和 24~34 年两种时间尺度下呈周期波动,30 年为第一主周期,17 年为第二主周期。长山群岛渔业资源破坏日益严重,未来几年平均营养级将呈下降趋势。为防止渔业资源进一步衰退,应加强捕捞活动管理力度,落实海洋渔业资源保护制度;完善预警机制,构建海洋渔业资源监测系统;同时应积极调整长山群岛渔业产业结构,提高资源产出效率.  相似文献   
2.
To understand the depositional processes and environmental changes during the initial flooding of the North China Platform, this study focuses on the Lower to Middle Cambrian Zhushadong and Mantou formations in Shandong Province, China. The succession in the Jinan and Laiwu areas comprises mixed carbonate and siliciclastic deposits composed of limestone, dolostone, stromatolite, thrombolite, purple and grey mudstone, and sandstone. A detailed sedimentary facies analysis of seven well‐exposed sections suggests that five facies associations are the result of an intercalation of carbonate and siliciclastic depositional environments, including local alluvial fans, shallowing‐upward carbonate–siliciclastic peritidal cycles, oolite dominant shoals, shoreface and lagoonal environments. These facies associations successively show a transition from an initially inundated tide‐dominated carbonate platform to a wave‐dominated shallow marine environment. In particular, the peritidal sediments were deposited during a large number of depositional cycles. These sediments consist of lime mudstone, dolomite, stromatolite and purple and grey mudstones. These shallowing‐upward cycles generally resulted from carbonate production in response to an increase of accommodation during rising sea‐level. The carbonate production was, however, interrupted by frequent siliciclastic input from the adjacent emergent archipelago. The depositional cycles thus formed under the influence of both autogenetic changes, including sediment supply from the archipelago, and allogenic control of relative sea‐level rise in the carbonate factory. A low‐relief archipelago with an active tidal regime allowed the development of tide‐dominated siliciclastic and carbonate environments on the vast platform. Siliciclastic input to these tidal environments terminated when most of the archipelago became submerged due to a rapid rise in sea‐level. This study provides insights on how a vast Cambrian carbonate platform maintained synchronous sedimentation under a tidal regime, forming distinct cycles of mixed carbonates and siliciclastics as the system kept up with rising relative sea‐level during the early stage of basin development in the North China Platform.  相似文献   
3.
A new approach towards the management of oil pollution accidents in marine sensitive areas is presented in this work. A set of nested models in a downscaling philosophy was implemented, externally forced by existing regional operational products. The 3D hydrodynamics, turbulence and the oil transport/weathering models are all linked in the same system, sharing the same code, exchanging information in real time and improving its ability to correctly reproduce the spill. A wind-generated wave model is also implemented using the same downscaling philosophy. Observations from several sources validated the numerical components of the system. The results obtained highlight the good performance of the system and its ability to be applied for oil spill forecasts in the region. The success of the methodology described in this paper was underline during the Costa Concordia accident, where a high resolution domain was rapidly created and deployed inside the system covering the accident site.  相似文献   
4.
南麂岛附近海域潮汐和潮流的特征   总被引:4,自引:2,他引:2  
以2008年冬季在浙江近海南麂岛附近投放的4个底锚系观测的水位和流速资料为依据,分析了潮汐和潮流特征。水位谱分析结果显示半日分潮最显著,全日分潮其次;近岸的浅水分潮比离岸大。水位调和分析结果表明:潮汐类型均为正规半日潮,近岸处的平均潮差大于3m,最大可能潮差大于6m,潮汐呈现出显著的低潮日不等和回归潮特征。流速谱分析结果显示半日分潮流最强,全日分潮流其次,且比半日分潮流小得多;近岸浅水分潮流比远离岸显著。流速调和分析结果表明:潮流类型均为正规半日潮流,靠近岸的两个站浅水分潮流较显著;最显著的半日分潮流是M2分潮流,其最大流速介于0.32~0.48m/s之间,全日分潮流均很弱,最大流速小于0.06m/s。M2分潮流均为逆时针旋转,椭圆率越靠近海底越大;最大分潮流流速分布为中上层最大、表层略小、底层最小;最大分潮流流速方向的垂向变化很小,底层比表层略为偏左;最大分潮流流速到达时间随深度的加深而提前,底层比中上层约提前30min。潮流椭圆的垂向分布显示这里的半日分潮流以正压潮流为主;日分潮流则表现出很强的斜压性。  相似文献   
5.
Seventy-eight marine fungal strains were isolated from sediment samples collected off the coast of Nanji Island,Wenzhou,Zhejiang Province,China.Antibacterial screening using the agar disc method showed that 19 of the isolated strains could inhibit at least one pathogenic Vibrio from Pseudosciaena crocea.Subsequent screening confirmed that nine strains produced antibacterial metabolites that had activity against one or several types of pathogenic Vibrio.Strain NJ0104 had the widest antimicrobial spectrum and strong activity,particularly against Vibrio parahaemolyticus-MM0810072.A preliminary study of NJ0104 antibacterial metabolites demonstrated that they had thermal stability up to 80°C,ultraviolet stability up to 40 min and pH stability between 4.0-7.0.In addition,the antibacterial metabolites were readily soluble in butanol.To identify the specific strain,the ITS-5.8S rDNA regions of NJ0104 were PCR amplified and sequenced.Based on the combination of phenotypic and genotypic data,the strain was identified as Arthrinium sp.  相似文献   
6.
南澎列岛及邻近海域地质地貌与灾害地质分析   总被引:2,自引:1,他引:2  
南澎列岛及邻近海域是广东沿海灾害地质因素较集中和类型较齐全的地区之一。根据野外调查资料,简要地分析了区内地质地貌以及活动断裂、地震活动、地面沉降、滑坡、地裂和沙土液化等基本特征和分布规律,同时还对区内地质灾害进行了初步分析。  相似文献   
7.
南麂列岛海洋自然保护区潮间带贝类资源时空分布   总被引:9,自引:0,他引:9       下载免费PDF全文
为了解南麂列岛海洋自然保护区潮间带贝类十多年来的动态变化,在1992年研究基础上,于2003年度再赴南麂列岛对岩、沙相贝类进行了研究.本次调查鉴定出贝类105种,其中岩相93种、沙相12种,6种为南麂列岛新记录种,对岩相、沙相贝类组合的生态特征进行了分析,岩相多样性和均匀度指数(1.25~2.20和0.54~0.70)高于沙相的(0.23~0.95和0.17~0.94).岩相贝类数量为3025.70g/m2和2660个/m2,生物量垂直分布为低潮区最高(6471.99g/m2),中潮区居中(3772.09g/m2),高潮区最小(78.35g/m2),栖息密度为中潮区最大(4245个/m2),低潮区居中(2973个/m2),高潮区最小(439个/m2).沙相贝类数量为16.81g/m2和11个/m2,低潮区(29.43g/m2和11个/m2)大于中潮区(14.01g/m2和10个/m2).通过与以往资料比对发现,岩礁贝类数量有所增加,沙滩贝类数量则明显下降,监控区贝类数量明显多于其他区域,对贝类资源变化产生影响的相关因子作了分析探讨.  相似文献   
8.
本文系根据1992年8月和1993年2月(夏、冬两季)对南麂列岛潮间带的环境本底调查以及对水质、底质、生物样监测结果的资料整理而成。调查结果表明,潮间带水质、底质除个别断面外,均处于良好状态。生物体重金属残留量全部低于全国海岸带调查时统一的标准,生态环境条件较好。  相似文献   
9.
This paper brings together unpublished historical data sets and published literature to review the role of climatic, oceanographic and ecological processes in the marine ecosystem of the eastern Canadian Archipelago. Physical data include characteristics of the water masses, circulation patterns, sea ice conditions, and climatic records from 1950s onward. Biological data include unpublished data sets on nutrients, primary and secondary production, and sedimentation, which were collected during the 1980–1990s in the eastern Canadian Archipelago. These results show high year-to-year variability in nutrient inventories and ratios, the magnitude of the ice algae and phytoplankton bloom, the timing of ice algae sedimentation in the spring, and the composition of the zooplankton community. The significance of this high interannual variability and its effect on pelagic–benthic coupling processes is discussed in the context of climatic and oceanographic forcing, with emphasis on recent (past decade) Arctic changes. An estimate of total primary production in the Archipelago is also presented, along with published production estimates for other Arctic shelves, showing that the Archipelago may support up to 32% of the total primary production of Arctic shelves. The high year-to-year variability in production and carbon transfer pathways (e.g. pelagic versus benthic) in the Archipelago suggest that the system might be resilient to the increased variability in climatic conditions occurring in the past decade. However, this increased variability combined with directional change in climatic and oceanographic conditions might also modify the existing balance of ecological processes. For example, shifts in the timing of events appear to have already occurred in the past decade, with potential cascading effects throughout the ecosystem.  相似文献   
10.
Abstract. The abundance, distribution, and species richness of the littoral sponges (0–55 m) from the Cabrera Archipelago (Balearic Islands) were studied along light gradients from the surface to the sea bottom and from cave mouths to their inner parts. A total of 98 species (11 Calcarea and 87 Demospongiae ) were recorded, 8 of which are new records for the Spanish coast.
Cluster and correspondence analyses enabled the identification of a sciophilous sponge group including three subgroups: sponges found only in semi-dark cave habitats, a subgroup common to the coralligenous, precoralligenous, and semi-dark cave biocoenoses, and a third subgroup exclusive to the coralligenous biocoenosis. A small number of photophilic species and other species having a wide bathymetric distribution made up another separate group. No species clusters for the different semi-sciophilous (either fleshy or carbonate) or photophilic seaweed communities were discernible. The number of sponge species was negatively correlated with the irradiance level.  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