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   95篇
  免费   2篇
测绘学   6篇
大气科学   3篇
地球物理   14篇
地质学   12篇
海洋学   7篇
天文学   51篇
自然地理   4篇
  2018年   1篇
  2016年   2篇
  2015年   1篇
  2013年   5篇
  2012年   1篇
  2011年   1篇
  2010年   2篇
  2009年   3篇
  2008年   6篇
  2007年   7篇
  2006年   2篇
  2005年   6篇
  2004年   12篇
  2003年   4篇
  2002年   4篇
  2001年   6篇
  2000年   4篇
  1999年   4篇
  1998年   8篇
  1996年   1篇
  1995年   2篇
  1985年   1篇
  1983年   2篇
  1982年   1篇
  1980年   2篇
  1978年   1篇
  1973年   1篇
  1962年   1篇
  1954年   1篇
  1951年   1篇
  1949年   3篇
  1937年   1篇
排序方式: 共有97条查询结果,搜索用时 15 毫秒
91.
We explore the feasibility of developing measures of area deprivation from routinely collected administrative data for the Auckland Region, based on the Scottish Indices of Multiple Deprivation. Using data from national health, social development, education, and police databases, geospatial data providers and the 2006 Census, we developed seven domains of deprivation: Employment; Income; Crime; Housing; Health; Education; and Geographical Access, which were combined to create an overall Index of Multiple Area‐Level Deprivation.Small areas developed for this research (‘Lower Zones’) highlight variations in deprivation for domains separately and combined, and validate the indices using smoking prevalence data.  相似文献   
92.
A common mechanism for both X-ray and-ray bursters is proposed on the basis that a window can be created transiently in the polar cap of a degenerate star, a white dwarf for X-ray bursts and a neutron star for-ray bursts. The window exposes transiently a hot degenerate sub-layer of the star at shallow depth, from which escapes blackbody flux for a source at temperature 3 kev with window radius 10 km in the case of X-ray bursts and for a source at temperature 300 kev with window radius 0.5 km in the case of-ray bursts.  相似文献   
93.
Four 40Ar/39Ar dates on mineral separates from fresh and hydrothermally altered volcanic and plutonic rocks from the Ngatamariki geothermal field indicate that andesitic volcanism took place in the eastern portion of the Taupo Volcanic Zone (TVZ) prior to 1.2 Ma and probably considerably earlier. These data significantly extend the onset and duration of andesitic volcanism in the east-central TVZ over previous estimates. Intrusive activity is represented at Ngatamariki by a dioritic pluton, the only such pluton yet recognized in the entire TVZ. Hornblende from the pluton yields a crystallization age of near 550 ka. Hydrothermal alteration spatially associated with the pluton produced sericite of a similar age. Overlying and postdating the most intense hydrothermal alteration zone is the Whakamaru Ignimbrite (or its equivalent) which was emplaced at 330 ka. Two distinct geothermal systems may have been active at nearly the same site from 550 ka to present. The most intense activity occurred before 330 ka and was associated with emplacement of the Ngatamariki diorite. This was followed by the less intense system that is currently active. The geothermal regime at Ngatamariki has, therefore, probably been active intermittently for at least 550 ka.  相似文献   
94.
    
  相似文献   
95.
96.
We have discovered a radio source (B2114+022) with a unique structure during the course of the JVAS gravitational lens survey. VLA, MERLIN, VLBA and MERLIN+EVN radio maps reveal four compact components, in a configuration unlike that of any known lens system, or, for that matter, any of the ∼15 000 radio sources in the JVAS and CLASS surveys. Three of the components are within 0.3 arcsec of each other while the fourth is separated from the group by 2.4 arcsec. The widest separation pair of components have similar radio structures and spectra. The other pair also have similar properties. This latter pair have spectra which peak at ∼5 GHz. Their surface brightnesses are much lower than expected for synchrotron self-absorbed components.
Ground-based and Hubble Space Telescope optical observations show two galaxies ( z =0.3157 and 0.5883) separated by 1.25 arcsec. The lower redshift galaxy has a post-starburst spectrum and lies close to, but not coincident with, the compact group of three radio components. No optical or infrared emission is detected from any of the radio components down to I =25 and H =23 . We argue that the most likely explanation of the B2114+022 system is that the post-starburst galaxy, assisted by the second galaxy, lenses a distant radio source producing the two wide-separation images. The other two radio components are then associated with the post-starburst galaxy. The combination of the angular sizes of these components, their radio spectra and their location with respect to their host galaxy still remains puzzling.  相似文献   
97.
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