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   193篇
  免费   3篇
  国内免费   5篇
大气科学   129篇
地球物理   36篇
地质学   20篇
海洋学   1篇
天文学   4篇
自然地理   11篇
  2019年   3篇
  2018年   3篇
  2017年   3篇
  2016年   2篇
  2015年   2篇
  2014年   2篇
  2013年   4篇
  2012年   3篇
  2009年   5篇
  2008年   2篇
  2007年   2篇
  2006年   2篇
  2005年   4篇
  2002年   2篇
  1998年   3篇
  1997年   2篇
  1996年   3篇
  1995年   3篇
  1994年   3篇
  1993年   2篇
  1991年   5篇
  1990年   3篇
  1989年   3篇
  1988年   6篇
  1987年   7篇
  1986年   5篇
  1985年   6篇
  1984年   7篇
  1983年   6篇
  1982年   13篇
  1981年   5篇
  1980年   7篇
  1979年   8篇
  1978年   3篇
  1977年   4篇
  1975年   4篇
  1974年   4篇
  1972年   4篇
  1971年   6篇
  1970年   2篇
  1969年   9篇
  1968年   5篇
  1961年   2篇
  1960年   2篇
  1957年   1篇
  1956年   1篇
  1955年   2篇
  1954年   1篇
  1953年   2篇
  1951年   1篇
排序方式: 共有201条查询结果,搜索用时 560 毫秒
41.
Many recent studies have applied satellite remote sensing data to large-scale hydrologic and biospheric modeling. It is widely accepted that the thermal infrared observations from the Advanced Very High Resolution Radiometer (AVHRR) have the potential to estimate land surface conditions, such as surface temperature, near surface air temperature, and near surface water vapor. In this study, algorithms to estimate all three variables are presented and applied to an area covering the state of Oklahoma for a six day period in August, 1994. The results were validated using ground observations from the 111 station Oklahoma Mesonet. Validation of the remote sensing algorithms with Mesonet observations produced comparable results to previous validation studies. In addition, the validation process revealed inadequacies in thermal modeling that had not been detected in previous validation studies leading to the development of a new approach to estimate atmospheric water vapor.  相似文献   
42.
Despite the recognition of the need for mitigation approaches to landslide risk in developing countries, the delivery of ‘on-the-ground’ measures is rarely undertaken. With respect to other ‘natural’ hazards, it is widely reported that mitigation can pay. However, the lack of such an evidence base in relation to landslides in developing countries hinders advocacy amongst decision makers for expenditure on ex-ante measures. This research addresses these limitations directly by developing and applying an integrated risk assessment and cost–benefit analysis of physical landslide mitigation measures implemented in an unplanned community in the Eastern Caribbean. In order to quantify the level of landslide risk reduction achieved, landslide hazard and vulnerability were modelled (before and after the intervention), and project costs, direct and indirect benefits were monetised. It is shown that the probability of landslide occurrence has been substantially reduced by implementing surface-water drainage measures and that the benefits of the project outweigh the costs by a ratio of 2.7–1. This paper adds to the evidence base that ‘mitigation pays’ with respect to landslide risk in the most vulnerable communities—thus strengthening the argument for ex-ante measures. This integrated project evaluation methodology should be suitable for adoption as part of the community-based landslide mitigation project cycle, and it is hoped that this resource, and the results of this study, will stimulate further such programmes.  相似文献   
43.
The atmospheric heat source strength over western Tibet has been computed for the period beginning with the last ten days in May, 1979 and extending through August, 1979. Our results show a significantly smaller heat source than that obtained by other authors. The discrepancy is mainly due to adjustments in the dray, coefficient suggested by observations and numerical modeling experiments. We subdivided western Tibet into northern and southern parts. In the north sensible heating, SH, provides the dominant input into the atmospheric heat source, whereas in the southern part latent heat, LP, offers a significant contribution after the start of the rainy season.Detailed heat budget calculations were also carried out over limited regions of southwestern Tibet which hau good station coverage. During periods with area-averaged rainfall ≤1 mm/day an atmospheric heat source maximum was located over southwestern Tibet near the 500 hPa level, while a heat sink dominated the upper troposphere in a layer of subsidence. When rainfall exceeded 4 mm/day, ascending motions and heal sources prevailed throughout the troposphere with maxima near 400 hPa. Time series analyses of the heat sourcs components show that the total atmospheric heat source is strongly modulated by the release of latent heat. Atmospheric radiational cooling reveals a phase shift in its relation with precipitation. During the first part of the observation period a correlation of that cooling exists mainly with the net radiation at the top of the atmosphere, during the last part with the net radiation at the ground.  相似文献   
44.
45.
46.
The last 50 years saw a dramatic increase in living standards and improvement in the quality of life for many of the world’s poorest. Mortality rates fell, life expectancy rose and per capita incomes swelled. That improvement has been underpinned by technological development and the ubiquitous use of metal and mineral resources. To maintain such progress while addressing climate change and a rising world population, sustainable sources of raw materials will be required, in both developed and developing countries. Delivering the UN Agenda 2030 with its seventeen Sustainable Development Goals and implementing the Paris Agreement of December 2015 will require technologies that consume both traditional and new minerals. Metal recycling and technological change will contribute, but mining must continue and grow for the foreseeable future. Of the 200 or so countries in the world, 60 are open to large-scale mining but 140 are not. New resource governance linkages are needed between existing institutional frameworks so that continuity of global mineral supply is assured over coming decades. Such arrangements would oversee responsible sourcing of minerals, directions of mineral exploration and sustainability of mining and ore processing, raising of consumer awareness and sharing the wealth generated by mining more fairly.  相似文献   
47.
48.
49.
Over the past few decades, band-pass filtered (BP) variance statistics have been widely used as indicators of storm track activity. A recent study suggested that these statistics may be subjected to biases related to Doppler shifting of variance into and out of the fixed frequency band, in the process perhaps greatly exaggerating the correlation between BP variance and mean flow variability. In this study, BP statistics are examined together with other storm track measures to assess whether BP variances are useful indicators of the patterns of storm track activity. Storm track variability related to the North Atlantic Oscillation, as well as the five leading EOFs of 300 hPa BP filtered variance statistics, have been examined. Results presented here suggest that BP variance statistics are useful measures of the patterns of storm track activity. Firstly, BP variance statistics largely reflect changes in total unfiltered transient eddy variance as well as spatially filtered statistics. Secondly, different BP statistics all give qualitatively similar patterns. Thirdly, patterns derived from BP statistics are well correlated (spatially) with precipitation anomalies. In addition, BP statistics are straightforward to compute, and easily reproducible. Moreover, BP variance and covariance statistics are closely related to how storm tracks interact with the large scale circulation. However, results shown in this paper support the suggestion that some biases may be caused by the Doppler effect, especially for variations such as the NAO which are tightly tied to changes in the background flow speed. Thus it is argued that BP statistics should be examined together with other measures of storm track activity to obtain a broader perspective on storm track variations.  相似文献   
50.
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