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   292篇
  免费   55篇
  国内免费   34篇
测绘学   36篇
大气科学   54篇
地球物理   176篇
地质学   53篇
海洋学   12篇
天文学   1篇
综合类   25篇
自然地理   24篇
  2024年   1篇
  2023年   4篇
  2022年   11篇
  2021年   12篇
  2020年   12篇
  2019年   22篇
  2018年   18篇
  2017年   17篇
  2016年   11篇
  2015年   15篇
  2014年   15篇
  2013年   21篇
  2012年   17篇
  2011年   14篇
  2010年   9篇
  2009年   15篇
  2008年   8篇
  2007年   10篇
  2006年   11篇
  2005年   10篇
  2004年   13篇
  2003年   12篇
  2002年   15篇
  2001年   8篇
  2000年   8篇
  1999年   6篇
  1998年   9篇
  1997年   5篇
  1996年   11篇
  1995年   14篇
  1994年   5篇
  1993年   8篇
  1992年   4篇
  1991年   3篇
  1990年   2篇
  1988年   1篇
  1987年   2篇
  1985年   2篇
排序方式: 共有381条查询结果,搜索用时 593 毫秒
71.
北欧海比容高度及其与卫星高度计海表面高度异常的比较   总被引:2,自引:1,他引:1  
In this study the steric height anomaly which is calculated from the hydrological data(EN3) is compared with the sea level anomaly derived from satellite altimetry in the Nordic Seas. The overall pattern of steric height is that it is higher in the margin area and lower in the middle area. The extreme values of steric height linear change from1993 to 2010 occur in the Lofoten Basin and off the Norwegian coast, respectively. Such a distribution may be partly attributed to the freshening trend of the Nordic Seas. The correlation between SLA(sea level anomaly) and SHA(steric height anomaly) is not uniform over the Nordic Seas. The time series of SLA and SHA agree well in the Lofoten Basin and northern Norwegian Basin, and worse in the northern Norwegian Sea, implying that the baroclinic effect plays a dominant role in most areas in the Norwegian Sea and the barotropic effect plays a dominant role in the northern Norwegian Sea. The weaker correlations between SLA and SHA in the Greenland and Iceland Seas lead a conclusion that the barotropic contribution is significant in these areas. The area-mean SHA over the entire Nordic Seas has similar amplitudes compared with the SLA during 1996–2002, but SHA has become lower than SLA, being less than half of SLA since 2006.  相似文献   
72.
在第27次中国南极科学考察度夏期间,针对长城站原地震台受干扰源(如发电栋、冷库)的影响,对台站进行了重新选址工作,并完成了新台站的基建工程(摆坑、电缆布设等),架设了一套宽频带地震仪。对新台站记录的数据进行分析表明新台站运行稳定,背景噪音小,记录的地震事件信噪比高,这为下一步开展相关地震学方面的研究将提供高质量的数据。尽管本次科考地震观测时间短,但是新台站不仅观测到了远震记录,而且观测到了长城站附近地区的近震和疑似冰震的记录。单台定位结果显示4次近震分布基本与南设得兰群岛走向平行,且震源深度由东北向西南逐渐变深。  相似文献   
73.
This paper introduces a new method to estimate the seismic hazard on engineering site.The method is mainly based on intensity data of historical earthquakes.The obvious feature of the method is to use some ideas of seismic hazard analysis and considering regional seismicity tendency.The authors depict the comprehensive method to estimate the related parameters and predict the seismic hazards for 14 sites as practical examples.Some problems are also discussed.Compared with seismic hazard analysis,this method has certain advantages,such as simpler computation,lower uncertainty and smaller sensitivity factor.Moreover total hazard P(I≥i)of a site can be examined with real historic data.The result given by the method in this paper can be more stable than that given by seismic hazard analysis nowadays.  相似文献   
74.
通过对三峡地区小台网地震观测和资料研究,认识到该区弹性波地动位移振幅随震中距增加而衰减的变化偏大,地震数字记录的S波波谱分析表明其拐角频率高达21.9Hz,功率谱极大区在0.5~26Hz间,该地区的地震烈度、震中烈度和等震线长轴长度分布具有一定的离散性。上述现象属于极浅源地震波的近场地表效应。研究这些效应特点,可为国家经济建设提供防震、抗震依据  相似文献   
75.
介绍从837工程中长周期摆中提取短周期信号的工作,其意义是利用现有的837工程中长周期摆增加区域台网的近震控制能力。该项工作主要是设计一个带有特殊滤波器的前置放大器,此滤波器在选取归一化参数时要求,以达到抑制低频而提取所需高频信号的目的。  相似文献   
76.
中国地震报告数据处理系统   总被引:1,自引:0,他引:1  
地震观测报告是一份具有广泛使用价值的地震基础资料。中国地震报告数据处理系统是提高中国地震报告质量的关键一环。其主要水平反映在:数据采集和处理自动化;采用最先进的数值计算方法;采用最先进的激光照排技术;用磁介质进行数据传递。  相似文献   
77.
地震宣传教育是地震工作的一项重要内容,抓好地城宣传教育,是搞好地震防灾工作的一项重要措施,在抓地震宣传教育时,应注意把握宣传教育的对象及特点,注意宣传内容,组织好宣传网络,掌握好宣传尺度,注重宣传效果。  相似文献   
78.
79.
Effects on the Ionosphere Due to Phenomena Occurring Below it   总被引:4,自引:0,他引:4  
The terrestrial thermosphere and ionosphere form the most variable part of theEarth's atmosphere. Because our society depends on technological systems thatcan be affected by thermospheric and ionospheric phenomena, understanding,monitoring and ultimately forecasting the changes of the thermosphere–ionosphere system are of crucial importance to communications, navigation and the exploration of near-Earth space. The reason for the extreme variability of the thermosphere–ionosphere system isits rapid response to external forcing from various sources, i.e., thesolar ionizing flux, energetic charged particles and electric fields imposed via the interaction between the solar wind, magnetosphere and ionosphere, as well as coupling from below (meteorological influences) by the upward propagating, broad spectrum,internal atmospheric waves (planetary waves, tides, gravity waves) generated in thestratosphere and troposphere. Thunderstorms, typhoons, hurricanes, tornadoes andeven seismological events may also have observable consequences in the ionosphere.The release of trace gases due to human activity have the potential to cause changes inthe lower and the upper atmosphere.A brief overview is presented concerning the discoveries and experimentalresults that have confirmed that the ionosphere is subject to meteorologicalcontrol (especially for geomagnetic quiet conditions and for middle latitudes).D-region aeronomy, the winter anomaly of radiowave absorption, wave-liketravelling ionospheric disturbances, the non-zonality and regional peculiaritiesof lower thermospheric winds, sporadic-E occurrence and structure, spread-Fevents, the variability of ionospheric electron density profiles and Total ElectronContent, the variability of foF2, etc., should all be considered in connection withtropospheric and stratospheric processes. Ionospheric weather, as a part of spaceweather, (i.e., hour-to-hour and day-to-day variability of the ionospheric parameters)awaits explanation and prediction within the framework of the climatological, seasonal,and solar-cycle variations.  相似文献   
80.
Geodatabase数据模型在配电设备管理中的应用   总被引:2,自引:0,他引:2  
首先简要介绍了Geodatabase数据模型;然后设计了Geodatabase配电网数据模型,并着重配电网中拓扑分析问题的处理;最后,利用一个简单设备介绍了Geodatabase数据模型中“复杂”节点的创建。  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