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   276篇
  免费   40篇
  国内免费   59篇
测绘学   11篇
大气科学   5篇
地球物理   68篇
地质学   155篇
海洋学   105篇
综合类   10篇
自然地理   21篇
  2023年   3篇
  2022年   11篇
  2021年   7篇
  2020年   8篇
  2019年   16篇
  2018年   8篇
  2017年   4篇
  2016年   12篇
  2015年   11篇
  2014年   13篇
  2013年   26篇
  2012年   20篇
  2011年   22篇
  2010年   19篇
  2009年   18篇
  2008年   29篇
  2007年   16篇
  2006年   26篇
  2005年   12篇
  2004年   12篇
  2003年   10篇
  2002年   11篇
  2001年   3篇
  2000年   6篇
  1999年   13篇
  1998年   5篇
  1997年   9篇
  1996年   4篇
  1995年   3篇
  1994年   5篇
  1992年   3篇
  1990年   1篇
  1989年   2篇
  1985年   2篇
  1984年   2篇
  1981年   3篇
排序方式: 共有375条查询结果,搜索用时 15 毫秒
371.
Surveys were carried out over 16 months to assess the distribution of enteroviruses of human origin in sediments and mussels near two sewage outfalls on the North Taranaki Coast, New Zealand. Enteroviruses were present in high numbers in both sediments and shellfish near the New Plymouth sewage outfall with maximum virus levels of 32 000 pfu 100 g‐1 of wet mussel tissue and 59 pfu 100 g‐1 of wet sediment material. Viruses were recovered occasionally from sediments and mussels near the Waitara Borough outfall. Coxsackievirus B4 was the predominant virus type isolated but CB5 and Poliovirus types 1, 2, and 3 were also recovered. Attempts to depurate virus‐contaminated New Plymouth mussels, by keeping them in water for 8 days with daily water replacement, did not achieve a significant reduction in virus numbers.  相似文献   
372.
In a laboratory study of the ingestion and assimilation efficiency of larvae of Aeshna brevistyla Rambur and Hemicordulia australiae Rambur, ingestion was determined using Cerenkov radiation techniques and assimilation efficiency by a double‐labelled isotope technique. Of each prey item (Daphnia carinata), 30% was not ingested but lost as body fluids and as material within the alimentary canal of the prey. Assimilation efficiency was greater than 70% for both dragonfly species, which appears to be typical for most other invertebrate predators. The efficiency with which 12th‐15th‐instar Aeshna assimilated 14C did not increase with feeding rate, but Hemicordulia increased its efficiency through instars 12–14. When dragonfly larvae were pre‐fed before experimentation, assimilation efficiency decreased in both species.  相似文献   
373.
Throughout the shores of the world,a confluence of different sources of pollution is common,e.g.,through outlets releasing brine,industrial,and domestic sewage.In this study,we assessed whether a combined disposal of domestic sewage and brine altered the patterns of abundance and assemblage structure of subtidal macrofauna inhabiting sandy seabeds on the south coast of Gran Canaria(Canary Islands,NE Atlantic Ocean).Samples were collected in two surveys(May 2008 and January 2009)at three distances(0,15,and30 m)away from the discharge point.Macrofaunal abundances showed different patterns with varying proximity from the disposal point in the two surveys.In May 2008,lower abundances were observed at0 m(53.89±46.82 ind.)than at 15 m(120±91.7 ind.)and 30 m(283.89±189.33 ind.)away from the disposal point.In January 2009,however,higher abundances were observed at 0 m(131.33±58.69 ind.)than at 30 m(100±24.44 ind.)and 15 m(84.78±58.39 ind.)away from the disposal point.Significant differences in macrofaunal assemblage structure were found with varying proximity from the discharge point in both surveys.The effect of proximity from the disposal point was confounded by changes in sedimentary composition between surveys,which contributed to explain differences in macrofaunal abundances and assemblage structure with varying proximity from the discharge point.As a result,confounding drivers of macrofaunal assemblage structure,here,changes in sediment composition,accounted for changes in macrofaunal abundances and assemblage structure with varying proximity from a combined disposal point of brine and sewage.  相似文献   
374.
侯伟  郭纯青  孙志忠 《吉林地质》2010,29(2):112-116
研究区隔污层为厚1m的亚砂土,隔污性能差,污水、垃圾无固定放置场所,且以明渠排放。根据污染程度确定了轻度污染区2600km2、中度污染区510km2、重度污染区663km2,提出了建立暗管排污系统的治理对策。  相似文献   
375.
为了阐明平原区排污河渠对地下水水质的影响程度和影响范围,以鲁北平原一条未采取防渗措施的多年排污河渠为例,进行了河渠污水对两侧浅层地下水污染机理的研究。通过Mg^2+、Cl^-、1,2-二氯乙烷等主要污染指标在排污河渠两侧的扩散规律研究,初步确定排污河渠对两侧浅层地下水综合质量的影响范围约为100 m。此结论为平原区浅层地下水的防污、治污提供了一定的参考依据。  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