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   1049篇
  免费   25篇
  国内免费   7篇
测绘学   20篇
大气科学   56篇
地球物理   205篇
地质学   391篇
海洋学   65篇
天文学   240篇
综合类   2篇
自然地理   102篇
  2021年   10篇
  2019年   10篇
  2018年   15篇
  2017年   21篇
  2016年   21篇
  2015年   15篇
  2014年   21篇
  2013年   47篇
  2012年   30篇
  2011年   31篇
  2010年   42篇
  2009年   37篇
  2008年   44篇
  2007年   42篇
  2006年   33篇
  2005年   23篇
  2004年   37篇
  2003年   28篇
  2002年   31篇
  2001年   15篇
  2000年   23篇
  1999年   26篇
  1998年   24篇
  1997年   9篇
  1996年   16篇
  1995年   22篇
  1994年   13篇
  1993年   11篇
  1992年   15篇
  1991年   20篇
  1990年   11篇
  1989年   15篇
  1988年   14篇
  1987年   14篇
  1986年   18篇
  1985年   24篇
  1984年   18篇
  1983年   12篇
  1982年   20篇
  1981年   9篇
  1980年   13篇
  1979年   13篇
  1978年   12篇
  1977年   14篇
  1976年   15篇
  1975年   21篇
  1974年   18篇
  1973年   14篇
  1972年   10篇
  1970年   7篇
排序方式: 共有1081条查询结果,搜索用时 31 毫秒
991.
992.
Seven new radar brightness and altitude images are presented. They are each of a small circular region within the equatorial belt of Venus. Resolution is, typically, 10 by 10 km; altitude contour spacing is 500 m. In addition, an image of the large rough feature β is presented with 25 by 25 km resolution.  相似文献   
993.
994.
995.
996.
997.
998.
A number of coastal and ocean observation systems exist throughout the Gulf of Mexico (GOM), but the network of systems is not currently linked or integrated and at present not fully implemented. The network of local systems are diverse, typically involving unique mandates and several different funding sources at various levels of permanence. The purpose of this paper is to describe the ocean observation systems that currently exist in the GOM, and to identify and quantify the expected economic benefits that may result from the implementation of an integrated regional network. Improved ocean observation systems are expected to reduce the uncertainty of ocean/weather forecasting and to enhance the value of ocean/weather information throughout the Gulf region. The source of benefits and the size of activity from which improved ocean observation benefits may be derived are estimated for private sector, non-market, and public sector activities categorized according to marine transportation, commercial fishing, recreational fishing, search and rescue operations, and pollution management. The benefits of improved ocean observation systems to energy exploration, development, and production activities are estimated, and a discussion of potential benefits to lightering activities, environmental monitoring, royalty payments, and engineering design are highlighted.  相似文献   
999.
We present the first data release from the second epoch Molonglo Galactic Plane Survey (MGPS-2). MGPS-2 was carried out with the Molonglo Observatory Synthesis Telescope at a frequency of 843 MHz and with a restoring beam of 45 × 45      arcsec2, making it the highest resolution large-scale radio survey of the southern Galactic plane. It covers the range  | b | < 10° and 245° < l < 365°  , and is the Galactic counterpart to the Sydney University Molonglo Sky Survey (SUMSS) which covers the whole southern sky with  δ≤−30° (| b | > 10°  ).
In this paper, we present the MGPS-2 compact source catalogue. The catalogue has 48 850 sources above a limiting peak brightness of 10 mJy beam−1. Positions in the catalogue are accurate to 1–2 arcsec. A full catalogue including extended sources is in preparation. We have carried out an analysis of the compact source density across the Galactic plane and find that the source density is not statistically higher than the density expected from the extragalactic source density alone.
We also present version 2.0 of the SUMSS image data and catalogue which is now available online. The data consist of 629 4.3°× 4.3° mosaic images covering the 8100 deg2 of sky with  δ≤−30° and | b | > 10°  . The catalogue contains 210 412 radio sources to a limiting peak brightness of 6 mJy beam−1 at  δ≤−50°  and 10 mJy beam−1 at  δ > −50°  . We describe the updates and improvements made to the SUMSS cataloguing process.  相似文献   
1000.
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