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   226篇
  免费   15篇
  国内免费   2篇
测绘学   5篇
大气科学   18篇
地球物理   73篇
地质学   66篇
海洋学   23篇
天文学   46篇
综合类   2篇
自然地理   10篇
  2023年   1篇
  2022年   3篇
  2021年   8篇
  2020年   7篇
  2019年   9篇
  2018年   12篇
  2017年   15篇
  2016年   16篇
  2015年   8篇
  2014年   12篇
  2013年   10篇
  2012年   9篇
  2011年   13篇
  2010年   14篇
  2009年   17篇
  2008年   14篇
  2007年   15篇
  2006年   14篇
  2005年   6篇
  2004年   2篇
  2003年   7篇
  2002年   7篇
  2001年   5篇
  2000年   1篇
  1999年   2篇
  1998年   1篇
  1997年   2篇
  1995年   2篇
  1994年   1篇
  1982年   2篇
  1981年   2篇
  1978年   1篇
  1977年   1篇
  1964年   1篇
  1956年   1篇
  1955年   1篇
  1949年   1篇
排序方式: 共有243条查询结果,搜索用时 125 毫秒
241.
Forest pest populations can fluctuate dramatically in relation to climate and density-dependent factors. Although the distributional range of the pine processionary moth Thaumetopoea pityocampa (Lepidoptera Notodontidae) appears to be expanding northward and upslope with climate warming, the relative importance of climate and endogenous, density-dependent factors has not been clearly documented. We analyzed the population dynamics of the moth using long-term data from two provinces in the Southern Alps (Trento: 1990–2009, Bolzano/Bozen: 1975–2011) to evaluate the relative importance of climate and density-dependent factors as regional drivers. Both summer temperatures and rainfall significantly affected population growth rate, with different outcomes depending on the local conditions. Although previous studies indicated that low winter temperatures have negative effects on insect performance, our analyses did not show any negative effect on the population dynamics. A negative density dependent feedback with a 1-year lag emerged as the most important factor driving the population dynamics in both regions. Potential mechanisms explaining the observed negative density feedback include deterioration of host quality, increased mortality caused by pathogens, and increase of prolonged diapause as an adaptive mechanism to escape adverse conditions.  相似文献   
242.
A tornado with severe intensity hit the municipalities of Pianiga, Dolo and Mira close to Venice, northeast Italy, causing damages on a wide number of residential and industrial buildings and destroying some historical villas. In this study, the authors show the results of the damage assessment survey performed in the first days after the occurrence of the extreme event. Limited literature deals with damage assessment of European building types due to wind actions, and the available one does not consider building vulnerability as key factor in the structural response of existing structures subject to tornado hazard. In this paper, structural damages surveyed in reinforced concrete frame structures and masonry buildings, representative of common Italian building types, are critically discussed. Additionally, this work provides a database of past tornado events in northeast Italy, evidencing how the analyzed area has been found to be quite prone to tornado hazard.  相似文献   
243.
We present the feasibility of a prototype, near real-time assimilation and ensemble prediction system for the Intra-Americas Sea run autonomously aboard a ship of opportunity based on the Regional Ocean Modeling System (ROMS). Predicting an ocean state depends upon numerical models that contain uncertainties in their modeled physics, initial conditions, and model state. An advanced model, four-dimensional variational assimilation, and ensemble forecasting techniques are used to account for each of these uncertainties. Every 3 days, data from the previous 7 days period were assimilated to generate an estimate of the circulation and to create an ensemble of 2 weeks forecasts of the ocean state. This paper presents the methods and results for a multi-resolution assimilation system and ensemble forecasts of surface fields and dominant surface circulation features. When compared to post-processed science quality observations, the state estimates suffer from our reliance on real-time, quick-look satellite observations of the ocean surface. Despite a number of issues, the ensemble forecast estimate is often superior to observational persistence. This proof-of-concept prototype performed well enough to reveal deficiencies, provide useful insights, valuable lessons, and guidance for future improvements in real-time ocean forecasting.  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