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   84篇
  免费   10篇
  国内免费   171篇
测绘学   2篇
大气科学   48篇
地球物理   26篇
地质学   153篇
海洋学   12篇
综合类   13篇
自然地理   11篇
  2024年   5篇
  2023年   17篇
  2022年   13篇
  2021年   11篇
  2020年   9篇
  2019年   14篇
  2018年   13篇
  2017年   14篇
  2016年   11篇
  2015年   22篇
  2014年   37篇
  2013年   24篇
  2012年   4篇
  2011年   5篇
  2010年   9篇
  2009年   9篇
  2008年   5篇
  2007年   1篇
  2006年   10篇
  2005年   7篇
  2004年   7篇
  2003年   4篇
  2002年   4篇
  2001年   1篇
  2000年   4篇
  1999年   1篇
  1997年   1篇
  1988年   1篇
  1942年   2篇
排序方式: 共有265条查询结果,搜索用时 15 毫秒
211.
向泽君  罗再谦  汪明 《测绘通报》2011,(9):42-44,69
基于全景摄影测量技术,对实际的道路作面积测量,并对测量数据以全站仪测量为基准作相关误差分析;同时基于试验对GPS误差来源、摄影测量误差来源、数据采集等误差来源作简要分析,并提出减小和消除误差的措施。研究连续实景影像在“白改黑”工程中道路面积测量中的应用。  相似文献   
212.
伍红雨  李芷卉  李文媛  郑璟 《气象》2020,46(6):801-812
利用2003—2017年广东2000多个区域自动气象站逐小时降水资料,分析了不同历时的广东极端强降水的年和月变化特征,在此基础上分析汛期4—9月的极端强降水频次的时空分布特征。结果表明:近15年来,广东不同历时极端强降水出现频率的年变化趋势存在明显差异,在年以及前、后汛期,24 h呈减少趋势;3、1 h呈上升趋势,其中1 h极端强降水频率在年和后汛期呈显著增加趋势。5—6月是广东极端强降水最易出现的时段,频次大值主要出现在粤西南阳江、江门、茂名,中部和北部的广州、清远以及粤东的汕头、揭阳等地。后汛期极端强降水主要出现在粤中南部地区,特别是南部沿海。1 h极端强降水次数在珠江三角洲以及茂名信宜、高州等地增加趋势明显,而粤东的大部分地区为减少趋势。地形和大气环流等可能是广东极端强降水频次中心形成的重要因素。  相似文献   
213.
Please refer to the attachment(s) for more details  相似文献   
214.
根据1961—2019年广东86个站点的降水和气温以及大气环流和海温资料,采用统计分析方法,研究广东2月降水和气温的时空分布特征及其相应的大气环流与海温特征。结果表明:近59年广东2月有两个年代际降水偏少时段,但对应的气温特征显著不同,分别是1961—1981年“冷干”和1999—2019年“暖干”,其对应的大气环流特征表明,第一时段1961—1981年(第二时段1999—2019年)500 hPa高度场以经向(纬向)环流为主,东亚大槽偏强(弱),东亚冬季风偏强(弱),低层受异常北(南)风控制,地面冷高压偏强(弱),偏强的冷空气阻碍了来自海上的水汽输送(偏弱的冷空气不能南下至广东),使得广东处于水汽辐散区(青藏高原表现为反气旋式环流,南支系统不活跃,对广东地区水汽输送不足),最终导致广东2月低温少雨(高温少雨)。进一步的分析表明,热带东太平洋和北太平洋中部海温异常是影响广东2月降水的重要外强迫因子,其中第一时段1961—1981年(第二时段1999—2019年)是热带东太平洋(北太平洋中部)海温异常偏冷(暖)通过850 hPa经向风切变偏弱(北太平洋中部异常反气旋环流)来影响广东降水。热带印度洋全区一致型、西太平洋暖池区和北太平洋中部海温异常是影响广东2月气温的外强迫因子,其中前两者主要通过东亚大槽这一环流影响广东气温,而北太平洋中部海温仅影响“暖干”期下广东2月的气温。   相似文献   
215.
Following consideration of the characteristics of high temperature, high pressure and high in-situ stress in ultra-deep sedimentary basins, together with the existence of hydrocarbon phase state transformation, hydrocarbon-water-rock interaction and rock mechanical property transition at those depths, the evaluation index system for hydrocarbon preservation was established. The physical leakage evaluation indexes can be divided into three categories: the dynamic efficiency indexes of micro-sealing, caprock integrity and natural gas diffusion. The chemical loss evaluation indexes can be divided into two categories: the thermochemical sulfate reduction (TSR) index in marine gypsum-bearing carbonate strata and the thermochemical oxidation of hydrocarbons (TOH) index in clastic strata. The slippage angle and overconsolidation ratio (OCR) are the key evaluation indexes in the evaluation of the integrity of shale caprocks. TSR intensity can be quantitatively calculated by use of the ZnPVT state parameter method. The TOH strength can be used to estimate the degree of hydrocarbon chemical loss, based on the TOH-related authigenic calcite cement content or the degree of negative δ13C of authigenic calcite. For the evaluation of ultra-deep preservation in specific areas, key indexes can be selected according to the local geological conditions, instead of all indexes needing to be evaluated for every scenario.  相似文献   
216.
With the deepening of oil and gas exploration, the importance of depth is increasingly highlighted. The risk of preservation of storage space in deep reservoirs is greater than that in shallow and medium layers. Deep layers mean older strata, more complex structural evolution and more complex hydrocarbon accumulation processes, and even adjustment and transformation of oil and gas reservoirs. This paper systematically investigates the current status and research progress of deep oil and gas exploration around the world and looks forward to the future research focus of deep oil and gas. In the deep, especially the ultra-deep layers, carbonate reservoirs play a more important role than clastic rocks. Karst, fault?karst and dolomite reservoirs are the main types of deep and ultra-deep reservoirs. The common feature of most deep large and medium-sized oil and gas reservoirs is that they formed in the early with shallow depth. Fault activity and evolution of trap highs are the main ways to cause physical adjustment of oil and gas reservoirs. Crude oil cracking and thermochemical sulfate reduction (TSR) are the main chemical modification effects in the reservoir. Large-scale high-quality dolomite reservoirs is the main direction of deep oil and gas exploration. Accurate identification of oil and gas charging, adjustment and reformation processes is the key to understanding deep oil and gas distribution. High-precision detection technology and high-precision dating technology are an important guarantee for deep oil and gas research.  相似文献   
217.
The Sinongduo mining region includes two types of mineralizations: the epithermal and the carbonate-hosted PbZn-Ag deposits. Despite being studied for many years, the ore formation process and genesis of the carbonate-hosted Pb-Zn-Ag deposits remain poorly understood. The Pb-Zn-Ag ore bodies occur as veins and are hosted by limestone and dolostone of the Permian Xiala Formation. Three sulfide mineralization substages have been identified at the Sinongduo carbonatehosted deposit. Indium coupled w...  相似文献   
218.
<正>The third biological radiation refers to the Middle Triassic biological radiation in the world.In 2007,the China Geological Survey during field investigations of the project"Regional Geological Survey in Datong,Guishan,Luoping County and Pengzha at a scale of 1:50000 in Yunnan Province"first discovered and named the Luoping Biota(Fig.1).This Middle Triassic biota emanates from  相似文献   
219.
<正>Rare earth resources are relatively scarce worldwide,but their global consumption is increasing year-by-year.At present,China has about 36%of the global rare earth reserves,but provides 90%of the world’s supply,which has generally met world demand and promoted the development of the world economy.In order to continuously and stably supply rare earths to international markets,the Chinese Government has financially  相似文献   
220.
Based on repeated comparison studies of broadband digital seismic records before the Wenchuan M_S8. 0,Yushu M_S7. 1 and Qingchuan M_S5. 4 earthquakes,the possible microseismic fluctuations before impending earthquakes were preliminarily identified. In order to verify and test this phenomenon,a real-time tracking technical system was established by using continuous waveform records of more than 200 wide-band digital seismic stations in regional networks such as Gansu,Qinghai,Sichuan,Yunnan and Tibet.Through real-time tracking and dynamic monitoring of 24 earthquakes with M≥5. 0 occurring in the Qinghai-Tibetan block during the period of 2012-2014 and the observations of stations in some non-seismic areas,the reproducibility and objectivity of the impending earthquake phenomenon were verified. The main characteristics of the microseismic fluctuation phenomena immediately preceding the strong earthquakes are as follows:(1)the spectrum range is wider,the dominant frequency is 11-16 Hz,and the spectrum shape is more regular;(2)it appears 6-24 days before the earthquake,averaging about 15 days;(3)it is possible to be recorded by the stations within the epicenter distance of 50 km,and the stations with the epicenter distance of more than 50 km generally cannot record it;(4)this phenomenon is directional,i. e. the direction in which the activity degree,N-value,varies significantly may be related to the location of the seismic source,the seismogenic fault and the distribution of aftershocks of the strong earthquake. The preliminary study shows that the impending-earthquakes microseismic phenomena may be related to the pre-activity,micro-vibration and micro-rupture in the source region in the imminent stage,or the microactivity and micro-rupture associated with the active tectonics.  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