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   129篇
  免费   10篇
  国内免费   1篇
测绘学   3篇
大气科学   6篇
地球物理   20篇
地质学   60篇
海洋学   4篇
天文学   41篇
自然地理   6篇
  2024年   1篇
  2023年   1篇
  2021年   5篇
  2020年   1篇
  2019年   3篇
  2018年   4篇
  2017年   3篇
  2016年   8篇
  2015年   4篇
  2014年   3篇
  2013年   5篇
  2012年   9篇
  2011年   10篇
  2010年   11篇
  2009年   7篇
  2008年   6篇
  2007年   3篇
  2006年   7篇
  2005年   9篇
  2004年   6篇
  2003年   2篇
  2002年   3篇
  2001年   3篇
  2000年   3篇
  1998年   1篇
  1997年   2篇
  1996年   1篇
  1995年   2篇
  1994年   3篇
  1992年   1篇
  1991年   4篇
  1988年   3篇
  1987年   1篇
  1985年   1篇
  1984年   2篇
  1982年   1篇
  1976年   1篇
排序方式: 共有140条查询结果,搜索用时 15 毫秒
71.
72.
73.
This paper analyzes the determinants of international return migration intentions using survey data on guestworkers in Germany, 1970–1989. It is hypothesized that return migration intentions are influenced by personal attributes, residential and job satisfaction, and three time-dependent variables: a temporal trend, a duration effect, and years prior to retirement. The hypotheses are tested using logit models of the intention to return. The results indicate that return intention probabilities are strongly affected by satisfaction and time-dependent variables while the influence of personal attributes is of little importance.  相似文献   
74.
75.
This paper compares how well satellite versus weather station measurements of climate predict agricultural performance in Brazil, India, and the United States. Although weather stations give accurate measures of ground conditions, they entail sporadic observations that require interpolation where observations are missing. In contrast, satellites have trouble measuring some ground phenomenon such as precipitation but they provide complete spatial coverage of various parameters over a landscape. The satellite temperature measurements slightly outperform the interpolated ground station data but the precipitation ground measurements generally outperform the satellite surface wetness index. In India, the surface wetness index outperforms station precipitation but this may be reflecting irrigation, not climate. The results suggest that satellites provide promising measures of temperature but that ground station data may still be preferred for measuring precipitation in rural settings.  相似文献   
76.
International Journal of Earth Sciences - During the late Palaeozoic, lithospheric thinning in part of the Alpine realm caused high-temperature low-to-medium pressure metamorphism and partial...  相似文献   
77.
This bibliographic review gives an outline of publications in 2019 focusing on reference materials (RMs) used in geochemistry and related fields, such as palaeoclimate and environmental research.  相似文献   
78.
Although lignin is known to be not readily biodegradable the concentration of dissolved lignin decreased during aerobic biological treatment of paper mill wastewater performed in sequencing batch reactors (SBR). Systematic lab scale batch tests were conducted to clarify whether the observed removal of lignin was the result of biodegradation or adsorption onto the activated sludge. For the batch tests, sludge samples were taken from sequencing batch reactors operated at solid retention times (SRT) of 10, 15, 20, 30, and 40 days, respectively. The amount of lignin present in the bulk liquid and in the sludge samples was quantified by an analytical procedure comprising pyrolysis, gas chromatography and mass spectrometry (py‐GC/MS analysis). It was found that lignin adsorbs onto the activated sludge by up to 30%[TH]w/w. This demonstrates the sludge excellent adsorption properties. The ultimate removal of lignin is achieved by sludge wasting. The highest overall removal rate was found when sludge was used from the SBR run at SRT of 20 days.  相似文献   
79.
80.
Because it is located both on the Mid‐Atlantic Ridge and on a mantle plume, Iceland is a region of intense tectonics and volcanism. During the last glaciation, the island was covered by an ice sheet approximately 1000 m thick. A reconstruction of the ice flow lines, based on glacial directional features, shows that the ice sheet was partly drained through fast‐flowing streams. Fast flow of the ice streams has been recorded in megascale lineations and flutes visible on the currently deglaciated bedrock, and is confirmed by simple mass balance considerations. Locations of the major drainage routes correlate with locations of geothermal anomalies, suggesting that ice stream activity was favoured by lubrication of the bed by meltwater produced in regions of high geothermal heat flux. Similar control of ice flow by geothermal activity is expected in ice sheets currently covering tectonically and volcanically active area such as the West Antarctic ice sheet. Copyright © 2000 John Wiley & Sons, Ltd.  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