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   952篇
  免费   363篇
  国内免费   991篇
测绘学   19篇
大气科学   1392篇
地球物理   153篇
地质学   127篇
海洋学   432篇
天文学   6篇
综合类   42篇
自然地理   135篇
  2024年   12篇
  2023年   23篇
  2022年   59篇
  2021年   74篇
  2020年   90篇
  2019年   82篇
  2018年   67篇
  2017年   77篇
  2016年   67篇
  2015年   64篇
  2014年   90篇
  2013年   122篇
  2012年   117篇
  2011年   113篇
  2010年   94篇
  2009年   98篇
  2008年   92篇
  2007年   119篇
  2006年   113篇
  2005年   107篇
  2004年   76篇
  2003年   72篇
  2002年   67篇
  2001年   71篇
  2000年   59篇
  1999年   32篇
  1998年   41篇
  1997年   31篇
  1996年   39篇
  1995年   39篇
  1994年   32篇
  1993年   13篇
  1992年   19篇
  1991年   11篇
  1990年   1篇
  1989年   6篇
  1988年   3篇
  1987年   1篇
  1986年   1篇
  1985年   5篇
  1984年   3篇
  1983年   1篇
  1981年   1篇
  1980年   1篇
  1977年   1篇
排序方式: 共有2306条查询结果,搜索用时 46 毫秒
101.
102.
A time-dependent linear model on the equatorial beta plane is developed in this paper.Its verticalstructure consists of two active layers with equal density and temperature above the thermocline and aquasi-stationary layer with constant density below the thermocline.The results of nurnericat experiments show that the direct influence of heat on the equatorial ocean ismuch smaller than that of wind stress.Nevertheless,through the tropical ocean-atmosphere interaction,the change of wind stress resulting from the thermal forcing may set a determinant effect on the equilibriumand anomalous development of the ocean-almosphere circulation.  相似文献   
103.
Based on steady semi-geostrophic model equations,analysis is carried out of the linear and nonlinearmodification/response of the tropical atmosphere to the forcing of ideal paired heat sources of contrasting nature.Re-suits show that the linear part is dominant in the steady response but the nonlinear modification is quite noticable in theneighborhood of the heat source and between the paired sources,and the barotropic mode and second baroclinic modeplay a different role in the modification,with the barotropic(second baroclinic)mode modification depending largely onthe Rossby wave self-interaction(the magnitude due to the Kelvin-Rossby wave interaction)between the pairedsources.  相似文献   
104.
计算机天气图图形识别   总被引:4,自引:0,他引:4  
李振海 《气象》1994,20(6):20-23
根据天气系统的定义和实际业务中的天气图分析规范,总结出了500、700、850hPa3层高空天气图上特征等高线,特征等温线,槽线(含切变线),高(低)中心,冷(暖)中心以及热带气旋的识别方法及其判别式,并给出了实现计算机自动识别的程序设计步骤。  相似文献   
105.
Based on steady semi-geostrophic model equations,analysis is carried out of the linear and nonlinear modification/response of the tropical atmosphere to the forcing of ideal paired heat sources of contrasting nature.Resuits show that the linear part is dominant in the steady response but the nonlinear modification is quite noticable in the neighborhood of the heat source and between the paired sources,and the barotropic mode and second baroclinic mode play a different role in the modification,with the barotropic(second baroclinic)mode modification depending largely on the Rossby wave self-interaction(the magnitude due to the Kelvin-Rossby wave interaction)between the paired sources.  相似文献   
106.
The concentration of solvent-extractable (SE) and bound hydrocarbons, ketones, alcohols, sterols, monocarboxylic acids, hydroxyacids and α,ω-dicarboxylic acids of a surface sample (0–2.5 cm) from a recent carbonate tropical sediment taken at 60ft (18m) depth north-west of the Low Isles, North Queensland, are reported in detail. n-Alkanes are a minor constituent in the SE and bound hydrocarbon fractions with the major component being unresolved complex hydrocarbon material which is not an anthropogenic input. 6,10,14-Trimethylpentadecan-2-one derived from chlorophyll, as well as phytol, were identified as major components of the ketone and alcohol constituents. No chlorophyll pigments or pigmented degradation products were present, implying degradation before incorporation into the sediment. This conclusion is consistent with evidence for higher-plant input in which all sensitive lipids have been degraded before incorporation. SE and bound fractions have been studied in detail and show considerable differences probably arising from the importance of viable biomass in the SE fraction. Inputs to the sediment are determined as higher plants, algae, bacteria, fungi and meiofauna in descending order of importance.  相似文献   
107.
时间标度计算表明,西北太平洋热带气旋路径是一个无标度性的系统,其关联方差谱遵从频率的-2 ̄-3次方幂律,不同背景下的路径系统均如此。由此得到的不同季节、不同地域的热带气旋路径可预报时间尺度基本上为3 ̄4d,但异常热带气旋路径的可预报时间尺度则为1 ̄2d。  相似文献   
108.
热带太平洋地区SSTA和风应力场的海气耦合模态   总被引:13,自引:4,他引:13  
按国家气象局“八五”攻关力专家组提出的有关近海热带气候强度突变的标准,对1970-1991年在我国的近海发生强度突为的热带气旋进行了分类统计,发现如下气候特征:平均每年有8-9个热带气旋移到我国近海时发生强度突变,其中突然减弱的居多,占总个数的79.6%,突然增强的只占总个数的20.4%,突然增强只发和天5-10月,而突然减弱到5-12月均可发生;突然增强主要出现在浙闽沿海、南海中部,珠江口外西侧  相似文献   
109.
The tropical cyclone motion is numerically simulated with a quasi-geostrophic baroclinic model.The flow field of a tropical cyclone is decomposed into its axisymmetric and asymmetric components.The relation between the ventilation flow vector and the motion vector of the tropical cyclone is investigated.The results of numerical experiments indicate:(1) There are both large-scale beta gyres and small-scale gyres in the asyrnmetric flow field.(2) The interaction between small-scale gyres and large-scale beta gyres leads to the oscillation of translation speed and translation direction for the tropical cyclone.(3) There are the large deviations between the ventilation flow vector calculated by means of Fiorino and Elsberry's method and the motion vector of tropical cyclone.(4) The ventilation flow vector computed using the improved method closely correlates with the motion vector of the tropical cyclone.  相似文献   
110.
Temporal and spatial rainfall patterns were analysed to describe the distribution of daily rainfall across a medium‐sized (379km2) tropical catchment. Investigations were carried out to assess whether a climatological variogram model was appropriate for mapping rainfall taking into consideration the changing rainfall characteristics through the wet season. Exploratory, frequency and moving average analyses of 30 years' daily precipitation data were used to describe the reliability and structure of the rainfall regime. Four phases in the wet season were distinguished, with the peak period (mid‐August to mid‐September) representing the wettest period. A low‐cost rain gauge network of 36 plastic gauges with overflow reservoirs was installed and monitored to obtain spatially distributed rainfall data. Geostatistical techniques were used to develop global and wet season phase climatological variograms. The unscaled climatological variograms were cross‐validated and compared using a range of rainfall events. Ordinary Kriging was used as the interpolation method. The global climatological variogram performed better, and was used to optimize the number and location of rain gauges in the network. The research showed that although distinct wet season phases could be established based on the temporal analysis of daily rainfall characteristics, the interpolation of daily rainfall across a medium‐sized catchment based on spatial analysis was better served by using the global rather than the wet season phase climatological variogram model. Copyright © 2001 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