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   1721篇
  免费   85篇
  国内免费   13篇
测绘学   31篇
大气科学   100篇
地球物理   465篇
地质学   823篇
海洋学   104篇
天文学   219篇
综合类   7篇
自然地理   70篇
  2024年   6篇
  2023年   7篇
  2022年   22篇
  2021年   37篇
  2020年   28篇
  2019年   37篇
  2018年   84篇
  2017年   80篇
  2016年   106篇
  2015年   80篇
  2014年   122篇
  2013年   187篇
  2012年   67篇
  2011年   112篇
  2010年   112篇
  2009年   104篇
  2008年   85篇
  2007年   51篇
  2006年   54篇
  2005年   29篇
  2004年   28篇
  2003年   33篇
  2002年   35篇
  2001年   20篇
  2000年   20篇
  1999年   13篇
  1998年   11篇
  1997年   21篇
  1996年   13篇
  1995年   9篇
  1994年   18篇
  1993年   7篇
  1992年   15篇
  1991年   14篇
  1990年   7篇
  1989年   15篇
  1988年   6篇
  1987年   10篇
  1986年   5篇
  1985年   8篇
  1984年   7篇
  1983年   8篇
  1982年   9篇
  1980年   8篇
  1979年   7篇
  1978年   6篇
  1977年   5篇
  1975年   7篇
  1974年   6篇
  1973年   11篇
排序方式: 共有1819条查询结果,搜索用时 0 毫秒
1.
2.
3.
The spatial distribution of volatiles in the Martian hydrolithosphere   总被引:1,自引:0,他引:1  
In order to quantify the spatial distribution of volatiles on Mars, 2600 fluidized ejecta craters have been systematically measured, classified and mapped over the planet Mars, using 1 : 2 M scale USGS photomosaics. The latitudinal distribution of ejecta craters reveals that flower ejecta deposits (Type 1), together with low mobility ejecta, are frequently observed in the equatorial region and on ridged plains. Rampart craters (Type 2), with high mobility ejecta, occur at mid latitudes and exhibit a spatial relationship with polygonal patterns and pseudocrater areas. The increase of ejecta mobility with latitude attests for a concentration of volatiles at high latitudes. Statistical analysis shows that cratered uplands and ridged plains contain less volatile material near the surface than the underlying materials. In Chryse Planitia and Utopia Planitia the statistical study and the spatial relationships between polygonally fractured patterns, pseudocraters and the great number of high mobility ejecta deposits suggest the presence of a water-rich alluvial deposit close to the surface near the mouth of Chryse and Elysium channels. This result explains, on a more quantitative basis, the idea that fractured patterns were preferentially developed in a volatile-rich sedimentary deposits. The behaviour of volatiles, at 41 S, 257 W near Reull Vallis, exhibits a strong anomaly, with the presence of an abnormally volatile rich layer close to the surface.  相似文献   
4.
5.
6.
7.
8.
International Journal of Earth Sciences - This study reports on spectacular deformation structures, including arrays of striated thrusts, discovered by excavation work in Holocene deposits in...  相似文献   
9.
The availability of miniaturized sensors with enhanced capabilities, new methods for image processing, and easy access to small and low-weight airborne platforms for data acquisition, including unmanned vehicles, opens new possibilities for geodetic navigation applications and developing new developments in sensor fusion. In this context, the development of efficient methods, based on low-cost sensors, to extract precise georeferenced information from digital cameras is of utmost interest. We present a method to improve the performance of the integration of GNSS/low-cost IMU by exploiting the orientation changes retrieved from digital images. In this work, a robust-adaptive Kalman filter is also introduced to further improve the performance of the method deployed. The adaptive factor and the robust factor accomplished are determined by innovation information and the threshold value of orientation changes between consecutive images. Results from airborne tests used to assess the performance of the method are presented. The results show that using a non-metric camera, the Euler angle estimation accuracy of the GNSS/low-cost IMU integration can be improved to be close to 0.5 degree and an additional improvement, which can reach 59%, can be achieved after using the robust-adaptive Kalman filter.  相似文献   
10.

The priority of flood management planning is physical victimization and focuses on taking structural measures. Although this approach is an accurate approach, more information is needed in implementing efficient precautionary and planning decisions. It is an indisputable fact that the existence of nothing that is not sustainable in nature cannot continue. Hence, it is necessary to implement a planning decision suitable for the structure of the population living in the region so that the continuity of the policies to be carried out against natural hazards of hydrometeorological origin such as a flood is ensured. How the socio-demographic structures affect the flood risk perception of 245 people living in the city center of Bayburt is examined in this study. It is the first research conducted for the province of Bayburt for this perspective. The participants were asked to fill a questionnaire containing 24 items and consisting of 2 sections. T test and one-way ANOVA (one-way analysis of variance) statistical methods were used to ascertain the difference between the responses of the participants to the questionnaire, based on their demographic structure. As the result of the study, significant differences were observed between the expressions depicting flood risk perception and the participant's age, income levels and educational background. In addition, it has been noted that there is a positive relationship between education and income levels and flood risk perception.

  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