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   220篇
  免费   40篇
  国内免费   68篇
测绘学   20篇
大气科学   32篇
地球物理   41篇
地质学   162篇
海洋学   17篇
天文学   1篇
综合类   42篇
自然地理   13篇
  2017年   1篇
  2016年   1篇
  2015年   1篇
  2014年   2篇
  2013年   4篇
  2012年   1篇
  2011年   56篇
  2010年   34篇
  2009年   18篇
  2008年   9篇
  2007年   14篇
  2006年   26篇
  2005年   34篇
  2004年   55篇
  2003年   28篇
  2002年   17篇
  2001年   7篇
  2000年   1篇
  1999年   3篇
  1998年   3篇
  1997年   4篇
  1996年   2篇
  1995年   2篇
  1994年   2篇
  1992年   1篇
  1991年   1篇
  1982年   1篇
排序方式: 共有328条查询结果,搜索用时 46 毫秒
11.
A numerical wave flume is constructed based on the Reynolds Averaged Navier-Stokes (RANS) equations with turbulence closure by a modified k-ε model to study the viscous interactions of waves with vertical breakwaters for different overtopping cases. The governing equations,the turbulence model,boundary conditions,and solution method for the numerical wave flume are introduced briefly. The reliability of the numerical wave flume is examined by comparing the numerical results with the experimental measurement...  相似文献   
12.
In this paper,the theory for applying remote sensing to earthquake prediction has been elucidated and an experiment has been made.Through the experiment,it has been found that the characteristics and temperature of infrared radiant of rocks vary as a function of rock stress,the order of magnitude of radiance variation is 10-5(W/cm2 sr um),the amount of variation of the radiant temperature is 0.2℃~0.8℃ and some significant precursor information has been discovered.The experiment has verified preliminarily that the advanced technology of remote sensing can be applied to earthquake prediction.  相似文献   
13.
In this paper,a tropical atmospheric model of relevance to shorts-term climate variations(Wang and Li 1993)is util-ized for study of the development of Madden-Julian oscillation.The model contains an interactive process ofboundary-layer Ekman convergence and precipitation heating.The model is solved by expanding dependent variables interms of parabolic cylindrical functions in the meridional direction and truncating three meridional modes n=0,2,4 forequatorial symmetric solutions.The free wave solutions obtained under long-wave approximation are induced as aKelvin wave and two Rossby waves.After considering the effect of boundary-layer dynamic process,the modifiedKelvin wave becomes unstable in long-wave bands with a typical growth rate on an order of 10~(-6) s~(-1)and an eastwardphase speed of 10 m s~(-1);the most unstable mode is wavenumber one.These theoretical results are consistent with the ob-served Madden-Julian oscillation in equatorial area.For the two modified Rossby waves,one with a smaller meridionalscale(n=4)decays except for extra long-waves;the other with a larger meridional scale(n=2)grows in short-wavebands.This may be relevant to explaining the westward propagation of super cloud clusters in the Madden-Julianoscillation.The theory suggests that the boundary-layer dynamic process is an important mechanism in the develop-ment of the Madden-Julian oscillation.  相似文献   
14.
在Version 2的基础上,对短波辐射方案进行进一步的改进:引入了新增非灰体气体吸收效应、冰晶粒子形状效应和尺度效应以及云的不均匀性效应(称为Version 3)。数值模拟试验结果表明:Version 3能更好地模拟出全球冬、夏季的降水场、海平面气压场及地表气温场的主要分布特征,并且能相当准确地反映出这几个场的季节性变化特征。Version 3对这3个场的模拟能力明显优于原版本(Version 1)。此外,它对东亚地区的季风降雨具有很好的模拟能力,能较好地反映东亚区域降水的季节性变化。可见,Version 3为进一步研究云-辐射相互作用提供了很好的模式基础。本工作还清楚地表明,模式的进一步发展必须进行对相关物理过程中各个因子的更精确刻画,只有这样,模式才能得到更好的模拟能力。  相似文献   
15.
郑小梅  龙毅 《测绘学院学报》2002,19(4):265-267,271
简要介绍了一种GIS平台SICAD/Open,详细描述了SICAD/Open空间拓扑结构,给出了基于SICAD/Open空间拓扑结构的地籍空间实体图形变更处理方法,为在地籍信息系统中利用地理信息系统技术实现地籍空间实体图形变更提供了一种切实可行的操作方法。文中描述的处理方法已成功应用于上海市地籍管理信息系统中。  相似文献   
16.
油、水、干层的地球化学识别   总被引:4,自引:0,他引:4       下载免费PDF全文
本文介绍一种判断油、水、干层的地球化学方法,根据储层样品中有机抽提的的含量和组成特征,结合油层物性,地层测试和试油资料编制织识别油、水,干层的图版,提出判别油、水、干层的地质/地球化学指标,确定油层的地球化学参数的下限,并运用此方法对松辽盆地新站油田主要油层分布段的油、水、干层进行判别。根据试油资料验证表明,地球化学判断结果比传统的地质录井及地球物理测井资料判断结果更符合实际情况。  相似文献   
17.
One of the fundamental questions concerning the nature and prediction of the oceanic states in the equatorial eastern Pacific is how the turnabout from a cold water state (La Nina) to a warm water state (El Nino) takes place, and vice versa. Recent studies show that this turnabout is directly linked to the interannual thermocline variations in the tropical Pacific Ocean basin. An index, as an indicator and precursor to describe interannual thermocline variations and the turnabout of oceanic states in our previous paper (Qian and Hu, 2005), is also used in this study. The index, which shows the maximum subsurface temperature anomaly (MSTA), is derived from the monthly 21-year (1980-2000) expendable XBT dataset in the present study. Results show that the MSTA can be used as a precursor for the occurrences of El Nino (or La Nina) events. The subsequent analyses of the MSTA propagations in the tropical Pacific suggest a one-year potential predictability for El Nino and La Nina events by identifying ocean temperature anomalies in the thermocline of the western Pacific Ocean. It also suggests that a closed route cycle with the strongest signal propagation is identified only in the tropical North Pacific Ocean. A positive (or negative) MSTA signal may travel from the western equatorial Pacific to the eastern equatorial Pacific with the strongest signal along the equator. This signal turns northward along the tropical eastern boundary of the basin and then moves westward along the north side of off-equator around 16°N. Finally, the signal returns toward the equator along the western boundary of the basin. The turnabout time from an El Nino event to a La Nina event in the eastern equatorial Pacific depends critically on the speed of the signal traveling along the closed route, and it usually needs about 4 years. This finding may help to predict the occurrence of the El Nino or La Nina event at least one year in advance.  相似文献   
18.
矿产资源管理信息系统设计与开发   总被引:1,自引:0,他引:1  
基于GIS的矿产资源管理信息系统采用地理信息系统(GIS)技术、SQL Server数据库技术以及网络技术,实现了矿产资源信息图形数据与属性数据统一管理,为矿产资源管理工作提供了现代化的科学管理手段和决策支持。本文介绍了系统的设计与实现、系统包含的工作模块、各个模块的功能结构以及采用的技术特点。  相似文献   
19.
1 IntroductionMeteorological stations on the Tibetan Plateau are few in number and uneven in distribution, with a majority concentrated in the east and south. No stations exist so far within the large expanse in the middle or west of the Plateau. Moreover…  相似文献   
20.
本文利用单纯形法局部搜索速度快和模拟退火算法全局寻优的特点,同时为了克服各自算法的弊病,提出采用单纯形一模拟退火混合算法(SMSA)进行水文地质逆问题的求解。论文详细描述了SMSA算法的具体操作算子的实现,并将该算法应用于一个大型水源地的地下水模拟反演。计算结果表明,SMSA算法在水文地质参数反演计算具有求解速度快,精度高的特点,而且易于实现并行运算。  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