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   404篇
  免费   14篇
  国内免费   1篇
测绘学   7篇
大气科学   17篇
地球物理   80篇
地质学   122篇
海洋学   36篇
天文学   128篇
综合类   1篇
自然地理   28篇
  2021年   4篇
  2020年   4篇
  2019年   5篇
  2018年   7篇
  2017年   9篇
  2016年   7篇
  2015年   4篇
  2014年   11篇
  2013年   23篇
  2012年   3篇
  2011年   13篇
  2010年   12篇
  2009年   17篇
  2008年   17篇
  2007年   16篇
  2006年   15篇
  2005年   14篇
  2004年   23篇
  2003年   22篇
  2002年   17篇
  2001年   16篇
  2000年   14篇
  1999年   11篇
  1998年   14篇
  1997年   5篇
  1996年   4篇
  1995年   3篇
  1994年   4篇
  1993年   7篇
  1992年   6篇
  1991年   9篇
  1990年   2篇
  1989年   8篇
  1988年   2篇
  1987年   9篇
  1985年   7篇
  1984年   10篇
  1983年   8篇
  1982年   3篇
  1981年   3篇
  1980年   3篇
  1979年   4篇
  1978年   6篇
  1976年   2篇
  1975年   3篇
  1974年   2篇
  1970年   1篇
  1968年   1篇
  1967年   2篇
  1966年   3篇
排序方式: 共有419条查询结果,搜索用时 843 毫秒
241.
This paper is a review of work done on the production of an aerosol by the sea, and on the mechanisms by which bacteria might be enriched on the aerosol. Air bubbles produced in the sea, primarily by breaking waves, burst at the surface to eject both film and jet drops into the atmosphere. These drops are mixed upward by turbulence to produce the well-known marine sea-salt aerosol. In rising through the water, the bubbles may scavenge bacteria which, when the bubble burst, are skimmed off the bubble and ejected upward with the jet drops. Depending on drop size, the distance the bubble moves through the water, and other factors, the concentration of bacteria in jet drops can be several hundred times that in the bulk water film drops can also be enriched with bacteria. The enrichment of jet and film drops with bacteria, viruses, or toxins may at times produce a health hazard for those living along the shore.  相似文献   
242.
For almost a decade the Tallgrass Prairie Preserve in Oklahoma has been used as a field laboratory for the investigation of aspects of the remediation and restoration of oil and brine spills. Objectives of this work have included: (1) simplification of the remediation process and lowering the cost of remediation; (2) the development of methods to accelerate or jump-start the restoration process; and (3) determining appropriate metrics for assessing the status of soil ecosystem recovery. This research has resulted in a number of lessons learned that will be presented here which can be exported to other exploration and production sites, especially sites located in sensitive ecosystems. Key observations have included the role of a fertilizer amendment in linking the remediation and restoration process at an oil-impacted site, the use of nematodes as ecological indicators in the restoration of oil- and brine-impacted sites, and the development of a two-stage process for remediation of brine impacted sites that does not include significant use of gypsum.  相似文献   
243.
We present statistics of SGR 1806-20 bursts, combining 290 events detected with the Rossi X-Ray Timing Explorer/Proportional Counter Array, 111 events detected with the Burst and Transient Source Experiment, and 134 events detected with the International Cometary Explorer. We find that the fluence distribution of bursts observed with each instrument are well described by power laws with indices 1.43, 1.76, and 1.67, respectively. The distribution of time intervals between successive bursts from SGR 1806-20 is described by a lognormal function with a peak at 103 s. There is no correlation between the burst intensity and either the waiting times until the next burst or the time elapsed since the previous burst. In all these statistical properties, SGR 1806-20 bursts resemble a self-organized critical system, similar to earthquakes and solar flares. Our results thus support the hypothesis that the energy source for soft gamma repeater bursts is crustquakes due to the evolving, strong magnetic field of the neutron star, rather than any accretion or nuclear power.  相似文献   
244.
245.
246.
Finding the repeat times of the GPS constellation   总被引:5,自引:6,他引:5  
Single-epoch estimates of position using GPS are improved by removing multipath signals, which repeat when the GPS constellation does. We present two programs for finding this repeat time, one using the orbital period and the other the topocentric positions of the satellites. Both methods show that the repeat time is variable across the constellation, at the few-second level for most satellites, but with a few showing much different values. The repeat time for topocentric positions, which we term the aspect repeat time, averages 247 s less than a day, with fluctuations through the day that may be as much as 2.5 s at high latitudes.  相似文献   
247.
248.
This paper examines changes in gender relations in a small coastal community as a result of the 2010 Chile earthquake and tsunami. Vulnerability and resilience are used as a conceptual framework to analyse these changes. Based on empirical evidence from a seven-year longitudinal study and quasi-ethnographic work, we explore changes in power relations at the different stages of the disaster and longer-term recovery as well as the conditions that fostered these changes. Our findings show distinct patterns of change. First, disasters can trigger long-lasting changes that challenge historical patriarchal relations. Second, while vulnerability increases following a disaster, resilience can potentially counteract women’s vulnerability. We propose that resilience can be a pathway to produce long-term changes in gender relations and empower women in the context of disasters.  相似文献   
249.
250.
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