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   1583篇
  免费   265篇
  国内免费   391篇
测绘学   227篇
大气科学   237篇
地球物理   356篇
地质学   934篇
海洋学   114篇
天文学   119篇
综合类   113篇
自然地理   139篇
  2024年   10篇
  2023年   42篇
  2022年   101篇
  2021年   93篇
  2020年   92篇
  2019年   77篇
  2018年   85篇
  2017年   65篇
  2016年   88篇
  2015年   88篇
  2014年   97篇
  2013年   101篇
  2012年   65篇
  2011年   99篇
  2010年   83篇
  2009年   101篇
  2008年   84篇
  2007年   102篇
  2006年   77篇
  2005年   74篇
  2004年   42篇
  2003年   45篇
  2002年   45篇
  2001年   49篇
  2000年   50篇
  1999年   63篇
  1998年   51篇
  1997年   41篇
  1996年   28篇
  1995年   35篇
  1994年   45篇
  1993年   35篇
  1992年   18篇
  1991年   14篇
  1990年   12篇
  1989年   3篇
  1988年   3篇
  1987年   3篇
  1986年   9篇
  1985年   6篇
  1984年   5篇
  1983年   1篇
  1982年   1篇
  1981年   2篇
  1979年   5篇
  1958年   2篇
  1957年   2篇
排序方式: 共有2239条查询结果,搜索用时 15 毫秒
71.
以新世纪版《中华人民共和国国家经济地图集》的编研为背景,探讨了新世纪地学研究和测绘地理信息技术条件下经济地图集基础地理框架建立的若干问题。针对地图集的多尺度、多分辨率、多时态及内容的多样性等特点,通过对比与需求分析,重点探讨了地图集的地图投影、比例尺与分幅、地图定向及地理底图的设计与应用,并最终确定了地图集基础地理框架方案。  相似文献   
72.
Yin  Bojun  Zuo  Renguang  Xiong  Yihui 《Natural Resources Research》2022,31(4):2065-2079
Natural Resources Research - The application of deep learning algorithms in mineral prospectivity mapping (MPM) is a hot topic in mineral exploration. However, few studies have focused on recurrent...  相似文献   
73.
GPS repetition measurement tbta in Qinghai-Xizatlg (Tibetan) area in 1992 and 1994 have been used to determine the change rates of seven bascline vectors of Lhasa-Wenquan, etc. It is the first time to obtain the direct observation results of the large-scale crustal horizontal motions in this area. Thesc preliminary results also for the first time provide the direct observation evidence for some important geophysical and geological viewpoints, such as the northward gradual reduce of the effect of the northward push-pressing to Eurasian continent by Indian Plate in the Qinghai-Xizang area, having a southward strike slip movement of the Chuan-Dian diamond block, etc.  相似文献   
74.
The geochemical signatures of fifty-four rock samples and three supplementary drill stem test(DST) oils from the Yacheng-Sanya formations in the central Qiongdongnan Basin(CQB) were analysed. Reconstruction of the early Oligocene-early Miocene(36–16 Ma) palaeovegetation and source analyses of organic matter(OM) were conducted using aliphatic biomarkers in ancient sediments and DST oils. Both the interpreted aquatic and terrigenous OM contributed to the CQB source rocks(SRs) but had varying relat...  相似文献   
75.
Based on new and existing data on oxygen isotopes, alkenone-surface seawater temperature trends, planktonic foraminifers, lithology, and clay mineral composition of piston cores, a distinct cooling event has been identified around 8,200 cal a b.p. in the middle Okinawa Trough, northwest Pacific. This corresponds to the 8,200 a b.p. cooling event recorded in many places of the Northern Hemisphere. During this event, the local temperature decreased by 1°C, and the δ18O value increased by 0.6‰. A strengthened Asian winter monsoon is the most probable cause for this event, which thus adds further credibility to the contention that we are dealing here with a global phenomenon.  相似文献   
76.
77.
西沙海槽沉积模式   总被引:1,自引:0,他引:1  
晚中新世琼东南盆地快速构造沉降,沉积欠补偿形成了西沙海槽。西沙海槽上部高陡带为悬浮沉积体系,下部低缓带为浊流滑塌沉积体系,槽底平缓带为河流沉积体系。不同于浊流沉积小而散,深海河流沉积为稳定的贯穿整个海槽的大储层。由于深海河流沉积体系稳、远、大的特点,其注定成为世界深水油气勘探的主要目标。  相似文献   
78.
运用面向对象的软件开发技术,结合珊瑚礁地貌学、计算机图像学和计算机信息管理技术,在Windows平台上研制开发出南沙群岛珊瑚礁地貌图像信息管理系统。该系统集文件管理、数据库管理和图形、图像管理于一体,具有信息检索输出、信息编辑和信息维护等功能,以图形用户介面交互,达到"所见即所得"的效果。  相似文献   
79.
Numerical study about vortex-induced vibration(VIV) related to a flexible riser model in consideration of internal flow progressing inside has been performed.The main objective of this work is to investigate the coupled fluid-structure interaction(FSI) taking place between tensioned riser model,external shear current and upward-progressing internal flow(from ocean bottom to surface).A CAE technology behind the current research which combines structural software with the CFD technology has been proposed.According to the result from dynamic analysis,it has been found that the existence of upward-progressing internal flow does play an important role in determining the vibration mode(/dominant frequency),vibration intensity and the magnitude of instantaneous vibration amplitude,when the velocity ratio of internal flow against external current is relatively high.As a rule,the larger the velocity of internal flow is,the more it contributes to the dynamic vibration response of the flexible riser model.In addition,multi-modal vibration phenomenon has been widely observed,for asymmetric curvature along the riser span emerges in the case of external shear current being imposed.  相似文献   
80.
In the late Miocene, giant ancient pockmarks, which are fairly rare globally, developed in the Qiongdongnan Basin. In this paper, to determine the sedimentary characteristics and genetic mechanism of these giant ancient pockmarks in the Yinggehai Formation of the Qiongdongnan Basin, based on high-resolution 3D seismic data and multiattribute fusion technologies, we analyzed the planar distribution and seismic facies of the ancient pockmarks and compared the characteristics of the ancient pockmar...  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