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   63篇
  免费   1篇
测绘学   11篇
大气科学   3篇
地球物理   11篇
地质学   29篇
海洋学   4篇
天文学   3篇
自然地理   3篇
  2022年   3篇
  2020年   5篇
  2019年   2篇
  2018年   4篇
  2017年   2篇
  2016年   7篇
  2015年   2篇
  2014年   4篇
  2013年   7篇
  2012年   3篇
  2011年   1篇
  2010年   6篇
  2009年   5篇
  2007年   2篇
  2006年   3篇
  2005年   1篇
  2004年   2篇
  2002年   1篇
  2001年   1篇
  1999年   1篇
  1998年   2篇
排序方式: 共有64条查询结果,搜索用时 31 毫秒
51.
Three subspecies belong to middle-late Maastrichtian Bolivinoides draco group (B. draco aegyptiacus, B. d. draco, and B. d. dorreeni) are described of which one is new: Bolivinoides draco aegyptiacus from Abu Zenima section, west central Sinai, Egypt. This new subspecies differs from the other Bolivinoidid taxa in possessing well-developed two divergent medial longitudinal ribs along the smooth test surface, with another one rib in the central part between them. In this study, the early Maastrichtian B. miliaris is not related to this group. The other evolutionary trends are also distinguished and the paleogeographic distributions of Bolivinoides members in the Middle East are presented.  相似文献   
52.
53.
Within universities there has developed a clear theoretical convergence between Geographical Information Systems (GIS) and geography (Antenuccl, 1991). Studies have revealed that one of the qualified departments to teach GIS within universities is the geography department. This study focuses on: the importance of establishing GIS as a major curriculum element within universities. In geography departments, economic geography students require a strong statistical/mathematical background to allow them to work with major databases. They should know how to design a specific database for economic activities, such as agriculture and manufacturing, and tertiary industry and how to relate this database to a map, so that changes can be monitored more accurately. In any aspect of geography spatial location is a key factor and GIS allows spatial patterns to be interpreted with great facility. Therefore it is important that students have a good knowledge not only of computers and related software on economic geography, but also on GIS systems (Burrough, 1993). The work of geography students from the United Arab Emirates (UAE) and other Gulf Co-operation Council (GCC) geography departments is examined to evaluate the importance of training in GIS technology. This paper evaluates the effects of implementing GIS as a tool in teaching economic geography. At present there are 15 geography departments in the GCC which offer economic geography. Of those 15 departments, only 3 provide GIS courses within their curriculum, and 4 have basic equipment, although 6 additional departments are to introduce GIS in the near future. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   
54.
Ocean Science Journal - Seagrass meadows provide critical ecosystem services for coastal areas, e.g., as nursery habitats for various fish species, help with water filtration of suspended sediment,...  相似文献   
55.
Salim  H.  Torabi  Gh.  Shirdashtzadeh  N.  Sahlabadi  M.  Morishita  T. 《Geotectonics》2022,56(2):241-256
Geotectonics - The Early Oligocene alkalibasalts exposed in the Central Toveireh area located in the southwest of Jandaq city in Isfahan Province (Iran) and northwest of the Central-East Iranian...  相似文献   
56.
Geotechnical and Geological Engineering - The aim of this study is to optimize the geometric dimensions of the Koyna concrete weight dam with and without seismic forces using the grasshopper...  相似文献   
57.
Aerosol and water vapour are very important element in the Earth’s climate system which has direct role in the Earth’s radiation budget. In this paper the seasonality, latitudinal distribution and the relationship of aerosol optical thickness (AOD) and water vapour (WV) using MODIS Level 3 monthly data from 2001 to 2008 are analysed. The analysis shows that AOD (0.55 μm) values reach maximum during southwest monsoon and remain minimum during northeast monsoon period. The Equatorial Indian Ocean shows minimum AOD (0.115 to 0.153) throughout the year compared to Arabian Sea (0.208 to 0.613) and Bay of Bengal (0.214 to 0.351). Arabian Sea shows high variation and maximum value of AOD compared to Bay of Bengal and Equatorial Indian Ocean. During southwest monsoon WV over Bay of Bengal was found higher in concentration compared to Arabian Sea and Equitorial Indian Ocean throughout the study period. Comparison between Arabian Sea (2.98 cm to 5.07 cm) and Bay of Bengal (3.49 cm to 5.94 cm) shows that WV concentration is less in Arabian Sea throughout the year. The analysis of correlation between WV and AOD was found to be inconsistent. However, AOD and WV shows a strong positive correlation for whole year (Mean R2 =0.90) in the Equitorial Indian Ocean region except in the months of January, February and March. In general, the correlation between WV and AOD is found to be strongly positive for oceanic aerosol (sea salt) in low water vapour condition.  相似文献   
58.
Ibata et al. have recently discovered very faint, moving objects in the Hubble Deep Field (HDF). The number, apparent magnitudes and proper motions of these objects are consistent with old white dwarfs making up part of the Galactic dark halo. We review a number of ground-based proper motion surveys in which nearby dark-halo white dwarfs might be present, if they have the colours and absolute magnitudes proposed. No such objects have been found, whereas we argue here that several times more would be expected than in the HDF. We conclude that it is unlikely that hydrogen-atmosphere white dwarfs make up a significant fraction of the Galactic dark matter. No limits can be placed as yet on helium-atmosphere dwarfs from optical searches.  相似文献   
59.
The Luconia Province—offshore Sarawak—is a key hydrocarbon province in Malaysia. However, the gas reservoirs in Central Luconia pose unique problems and challenges as they have partially water-filled microporosity that overprint wireline logs. Microporosity in Central Luconia occurs throughout the Miocene carbonates and is a crucial element that influences fluid flow properties and ultimately the recovery of hydrocarbons. Quantification of macroporosity was achieved using petrographic analysis of thin sections and the FESEM images. The point counting technique was used to estimate the amount of macroporosity from the thin section, which was then subtracted from the total porosity to derive microporosity. The qualitative investigation of the Miocene carbonates indicates the presence of three different types of microporosity namely grain-based microporosity, matrix-based microporosity, and cement-based microporosity. Quantification of microporosity showed that the microporosity varies from sample to sample, ranging from 10 to 60% of the total measured porosity. The depositional texture, mineralogy, and microtexture control this microporosity variation including its abundance and type. The microporosity in Central Luconia is diagenetically controlled based on four major diagenetic mechanisms namely (1) mechanical process/endolithic grains/marine diagenesis; (2) leaching/meteoric diagenesis; (3) cementation/shallow diagenesis; and (4) deeper diagenesis environment.  相似文献   
60.
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