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   469篇
  免费   15篇
  国内免费   9篇
测绘学   3篇
大气科学   25篇
地球物理   95篇
地质学   145篇
海洋学   119篇
天文学   70篇
综合类   14篇
自然地理   22篇
  2022年   3篇
  2021年   6篇
  2020年   15篇
  2019年   5篇
  2018年   8篇
  2017年   15篇
  2016年   8篇
  2015年   7篇
  2014年   19篇
  2013年   22篇
  2012年   18篇
  2011年   17篇
  2010年   14篇
  2009年   25篇
  2008年   29篇
  2007年   17篇
  2006年   23篇
  2005年   29篇
  2004年   13篇
  2003年   14篇
  2002年   16篇
  2001年   6篇
  2000年   17篇
  1999年   13篇
  1998年   9篇
  1997年   6篇
  1996年   4篇
  1995年   4篇
  1994年   6篇
  1993年   6篇
  1992年   3篇
  1991年   4篇
  1990年   4篇
  1988年   7篇
  1987年   5篇
  1986年   6篇
  1985年   8篇
  1984年   8篇
  1983年   11篇
  1982年   4篇
  1981年   6篇
  1980年   4篇
  1979年   4篇
  1978年   8篇
  1977年   2篇
  1976年   5篇
  1975年   1篇
  1974年   2篇
  1973年   3篇
  1971年   3篇
排序方式: 共有493条查询结果,搜索用时 15 毫秒
491.
492.
Coastal Oyashio Water (COW), defined as a water mass with a temperature lower than 2 °C and a salinity lower than 33.0, is distributed in the North Pacific Ocean off southeastern Hokkaido, Japan, from winter to spring. COW is rich in macronutrients and dissolved iron and is thus considered to affect the spring phytoplankton blooms in the Oyashio region. Although river water and sea-ice melt water have been considered freshwater end-members of COW, the contributions of these freshwater sources to COW have not been well described. In this study, the humic-like components in dissolved organic matter were first applied as a parameter to evaluate the freshwater end-members of COW in March 2015. Linear regressions with negative slopes were determined between the humic-like components and the salinity of COW. The intercepts of the regressions against the humic-like components were within the ranges of those observed for the local rivers of Hokkaido but were very different from those of sea ice. These findings suggest that river water contributed to the COW observed here as a freshwater end-member, although the contribution of sea-ice melt water to COW could not be evaluated. This novel approach also highlighted two different less-saline water masses in COW. The first was characterized by a lower temperature and relatively high levels of humic-like components, while the second was higher in temperature and had higher levels of humic-like components. It is suggested that these different characteristics are due to the contributions of water from different rivers and/or different effects of sea-ice melt water.  相似文献   
493.
The non-marine Cretaceous-Paleogene boundary ( KPgB) in Jiayin of Heilongjiang was first defined and reported in China by the authors' research team in 2011 . Thereafter the continuous research on the KPgB and its related Late Cretaceous biota in Jiayin has been made by the authors in 2012-2020 . The achievements of the research are mainly reflected as follows:(1) a new drilling borehole with 60 m in depth carried out in the Xiaoheyan of Jiayin in 2016 , supplemented new palynological evidence for the KPgB definition in 2011;( 2 ) some radiometric dating newly made on the strata related to the KPgB in Jiayin and its neighboring Russian area, provided the supplemental evidence for the KPgB definition in Jiayin;( 3 ) many new fossils found by the au-thors, represented by the angiosperms Dalembia and Nelumbo, refresh understanding the Late Cretaceous envi-ronment of Jiayin;and (4) the TEM method is applied in the study of pollen exine ultrastructure of Pseudoin-tegricorpus, Wodehouseia, and Aquilapollenites, promoting the late Maastrichtian ecological study in Jiayin, re-lated to the KPgB.  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