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   121篇
  免费   15篇
  国内免费   44篇
地球物理   7篇
海洋学   160篇
综合类   9篇
自然地理   4篇
  2023年   5篇
  2022年   2篇
  2021年   8篇
  2020年   9篇
  2019年   6篇
  2018年   5篇
  2017年   11篇
  2016年   12篇
  2015年   7篇
  2014年   12篇
  2013年   8篇
  2012年   6篇
  2011年   3篇
  2010年   10篇
  2009年   14篇
  2008年   11篇
  2007年   6篇
  2006年   6篇
  2005年   5篇
  2004年   3篇
  2003年   1篇
  2001年   2篇
  2000年   7篇
  1999年   3篇
  1998年   3篇
  1996年   3篇
  1993年   2篇
  1992年   1篇
  1990年   1篇
  1985年   3篇
  1984年   1篇
  1983年   1篇
  1982年   3篇
排序方式: 共有180条查询结果,搜索用时 31 毫秒
131.
132.
于2006、2007和2009年台州大陈岛猪腰屿资源增殖保护区建立前、后,对该保护区内潮间带大型底栖生物进行了采样调查,分析了大型底栖生物的种类组成、数量、群落结构及增殖放流品种对保护区建立的生态响应.结果显示:保护区建立后,大型底栖生物的物种数、生物量和丰度均比建区前有明显提高;增殖放流黄口荔枝螺Thais lute...  相似文献   
133.
2009年4月对舟山海域13个站位的大型底栖生物群落结构的生态特征进行了调查,并结合2001—2008年浙江近岸海域生态环境监测数据资料,分析了该海域大型底栖生物的变化趋势及其生存环境现状。结果表明,调查海域共鉴定出大型底栖生物84种,其中多毛类31种,甲壳类25种,软体动物12种,鱼类8种,腔肠动物4种,棘皮动物和其它类各2种。2009年春季该海域大型底栖生物的生物量平均值为11.62g/m2,丰度平均值为208.5个/m2,生物多样性指数(H′)为1.64,丰度呈由近岸向外海递增的趋势。根据Bray-Curtis相似性系数聚类分析和多维尺度排序分析,该海域大型底栖生物可划分为3个群落,分别为群落Ⅰ:双鳃内卷齿蚕-织纹螺-孔鰕虎鱼群;群落Ⅱ:色斑角吻沙蚕-脊尾白虾群落;群落Ⅲ:葛氏长臂虾-织纹螺群。通过丰度/生物量累积k-优势度曲线分析可知,该海域大型底栖生物群落已受到中度程度的污染或扰动,群落结构不稳定。比较分析2001—2009年舟山海域大型底栖生物生物量和丰度变化趋势可知,个体较小、生长周期较短的种类逐步成为舟山海域的优势类群。  相似文献   
134.
The impact of raft mussel-culture in Saldanha Bay, South Africa on macrobenthic community structure (abundance and biomass) was studied. Sampling was conducted in January between 1993 and 1996 to assess: (1) the composition of macrobenthos below rafts relative to outside the farm; (2) effects of raft position and age within the farm; and (3) recovery rate of benthos after raft removal. Analyses included ABC plots, hierarchical clustering and species diversity indices. Disturbed communities were found under 78% of raft sites sampled. The level of disturbance (Warwick Statistics) and the dominant opportunistic species (Bray–Curtis Similarities) changed from year to year, polychaetes and scavenging gastropods being most common. The degree of disturbance appeared related to raft sites positioned in the middle of the farm rather than raft age. Whereas ABC plots and hierarchical cluster analyses best identified the disturbance of benthic communities, diversity indices detected marginal recovery four years after raft removal. Although deposit feeders dominated all sites, suspension feeders increased in number and biomass at reference sites. This study presented a “yes/no” scenario that will be addressed in subsequent research in the modelling of culture ecosystems.  相似文献   
135.
The soft-bottom communities of eight Italian lagoons were analyzed for eight biological traits (feeding, mobility, adult life habitat, body size, life span, reproductive technique, type of larva and reproductive frequency) in order to identify the dominant traits in different transitional environments. We considered the ecological quality status (EcoQS) of the stations, assessed by two biotic indices, AMBI and Bentix. Stations were categorized into EcoQS classes to investigate the relationship between biological functions and ecological quality. The results indicate that the variability of the data was governed by traits linked to resource utilization rather than to life cycle. Lagoons affected by chronic disturbance displayed a poor functional composition, which usually corresponded to poor EcoQS in some cases, correlations between ecological groups and traits modalities were ecologically relevant; however, classes of EcoQS were found to be relatively independent from the functional structure of the considered stations.  相似文献   
136.
The effects of urban development cause substantial physical changes in coastal waterways through hardening and reclamation of river banks, alteration of water flow, and diffuse and point-source discharges of pollutants. The cumulative effects of urbanization on the fauna of estuaries are not well understood. This study examined the benthic infauna of two urban and three rural estuaries near Townsville, North Queensland. A range of univariate and multivariate statistics was used to relate variation in the benthic assemblages to concentrations of contaminants (heavy metals and hydrocarbons) within the sediments of each estuary. Sediments in the most developed estuary contained concentrations of heavy metals and petroleum hydrocarbons that were several orders of magnitude greater than those from non-urban waterways. The fauna at these sites was dominated by cirratulid and sternaspid polychaetes and lacked filter-feeding bivalves and other molluscs that were common in less developed estuaries. These differences were generally consistent throughout each estuary, indicating estuary-wide patterns of change, that were most strongly associated with spatial patterns in the distribution of Pb, Cu and hydrocarbons.  相似文献   
137.
138.
王丑明  黄代中  张屹  田琪  阴琨  熊莉  陈勇 《湖泊科学》2023,35(5):1765-1773
为客观跟踪洞庭湖水生态环境质量,掌握洞庭湖水生生物完整性状况和变化趋势,支撑长江流域水生态考核工作的开展,基于洞庭湖30多年(1988—2021)的大型底栖动物群落特征数据,构建洞庭湖大型底栖动物完整性指数(BIBI)。基于完整性评价结果,采用多元逐步回归分析识别30多年间影响洞庭湖B-IBI的主要环境因素和贡献率。以低压力期(1988—1994年)底栖动物特征确定参照状态,构建的B-IBI由总分类单元数、甲壳类和软体类分类单元数、H指数、总密度和BI指数5项核心参数构成;同时确定出5项参数的期望值,并建立起B-IBI评价的标准:B-IBI≥6.34,优秀;4.75≤B-IBI<6.34,良好;3.17≤B-IBI<4.75,中等;1.58≤B-IBI<3.17,较差;B-IBI<1.58,很差。经B-IBI在低、高压力组的箱线图分析,进一步验证了该指数的辨别力和适用性。根据研制的B-IBI评价标准,得到洞庭湖B-IBI从1988年的6.99(优)下降到2021年的2.97(较差),表明洞庭湖底栖动物完整性呈现显著的下降趋势。相关环境因素的分析显示,同期洞庭湖的...  相似文献   
139.
山东长岛潮间带大型底栖动物生态特征研究   总被引:4,自引:1,他引:3  
2015年11月(秋季)、2016年2月(冬季)、2016年6月(春季)、2016年9月(夏季)大潮期间对山东长岛列岛中南长山岛和北长山岛的3个不同底质类型的潮间带采样点进行了系统的大型底栖动物调查,研究了其数量特征和季节变化,包括群落种类组成、密度和生物量、优势种、物种多样性等,结果表明:本次调查共鉴定出大型底栖动物隶属7个门,共81种。其中环节动物门多毛类动物25种,软体动物门25种,节肢动物门22种,棘皮动物门6种,其他类群共3种(包括纽虫、腔肠动物和鱼类各1种)。潮间带大型底栖动物平均密度为118.97 ind./m~2,软体动物和甲壳动物占据了研究区域底栖群落的密度主要成分,两者分别占比为39.58%和36.68%。各采样点平均密度为北长山岛(BCS)(141.17 ind./m~2)避险角(NCS1)(122.33ind./m~2)明珠广场东(NCS2)(93.42ind./m~2);各采样点平均生物量为128.03g/m~2,软体动物和甲壳动物占据了研究区域底栖群落的生物量主要成分,两者分别占比为58.56%和35.32%。平均生物量北长山岛(BCS)(234.95g/m~2)避险角(NCS1)(99.99g/m~2)明珠广场东(NCS2)(49.13g/m~2)。从季节来看,各站点的物种数、平均密度和生物量季节变化的规律性不明显,总体为秋、春季较多,夏、冬季较少。3个站点物种多样性指数(H′)、丰富度指数(D)和均匀度指数(J′)平均值分别为2.30、1.99和0.79,各潮区中,均为中潮带低潮带高潮带,各季节变化不明显。优势种受底质类型和季节变化的影响明显,没有在各站点和季节均为优势种的种类,主要的优势种有平背蜞(Gaetice depressus)、绒螯近方蟹(Hemigrapsus penicillatus)、短滨螺(Littorina brevicula)等。与以往历史资料相比,长岛潮间带生物出现了一定变化,种类和数量减少,与烟台近岸潮间带大型底栖动物种类组成差别很大。  相似文献   
140.
Each year approximately 23–28 million tonnes of sand and gravel are removed from offshore sediments around England and Wales. This study was located in a licensed marine aggregate extraction site off Shoreham in the Eastern English Channel (EEC thereafter). Results from the multibeam survey showed the presence of dredged pits created by suction hopper dredging and elongated furrows created by trailer suction hopper dredging in the area where sand and gravel had been excavated. Electronic Monitoring System (EMS) contained the dredging intensity recorded annually at the site; this information was combined with particle size data providing interpreted maps, which informed the status of the sediments at the site.  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