首页 | 官方网站   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   860篇
  免费   51篇
  国内免费   9篇
地球科学   920篇
  2023年   4篇
  2022年   6篇
  2021年   29篇
  2020年   12篇
  2019年   19篇
  2018年   34篇
  2017年   35篇
  2016年   49篇
  2015年   31篇
  2014年   27篇
  2013年   56篇
  2012年   42篇
  2011年   45篇
  2010年   42篇
  2009年   58篇
  2008年   44篇
  2007年   44篇
  2006年   37篇
  2005年   22篇
  2004年   42篇
  2003年   29篇
  2002年   21篇
  2001年   19篇
  2000年   28篇
  1999年   14篇
  1998年   12篇
  1997年   8篇
  1996年   11篇
  1995年   6篇
  1994年   3篇
  1993年   7篇
  1991年   8篇
  1990年   5篇
  1988年   4篇
  1987年   2篇
  1986年   3篇
  1984年   6篇
  1983年   12篇
  1982年   6篇
  1981年   5篇
  1980年   3篇
  1979年   3篇
  1978年   3篇
  1977年   4篇
  1976年   4篇
  1975年   2篇
  1974年   5篇
  1973年   2篇
  1972年   2篇
  1967年   1篇
排序方式: 共有920条查询结果,搜索用时 0 毫秒
1.
2.
Cities like London, New York and Los Angeles possess complex urban environments that, despite their technological sophistication, present their citizens with a multiplicity of risks. This paper presents a discussion of the effects of physical and social trends on the creation of risk and vulnerability to hazard in such cities. The interplay between physical hazards and perceived risks in late modern, or Risk, urban societies is considered, and the impact of this process on adjustment to hazard.  相似文献   
3.
Mark E Bailey and Tom Ray give an overview of the National Astronomy Meeting in Dublin, where record numbers of astronomers went to talk, listen and network.  相似文献   
4.
We used multivariate statistical techniques to analyse the distributions of surface sediment chironomid assemblages with respect to surface-water temperature, and an additional set of 27 environmental variables, in 30 freshwater lakes of northern Fennoscandia. Our study transect spans boreal coniferous forest to subarctic tundra and includes a steep temperature gradient. Canonical correspondence analysis (CCA) with forward selection and associated Monte Carlo permutation tests revealed that there were statistically significant (P<0.05) relationships between chironomid distributions and two environmental variables, namely lakewater temperature and maximum lake depth. A constrained CCA with temperature as the only predictor variable suggested that the relationship between lakewater temperature and chironomid composition was sufficiently robust for developing a weighted-averaging (WA) based quantitative inference model that will allow palaeotemperature reconstructions using subfossil chironomid remains preserved in lake sediments.  相似文献   
5.
6.
7.
Mineralogical and chemical investigations (<2μm clay separates) of shale samples from the Neogene-age Surma Group obtained from four wells (Habiganj-11, Shahbazpur-1, Titas-11, Titas-15) in the Bengal basin, Bangladesh, were carried out in order to reveal the clay mineral composition as reservoir exploration and exploitation requires a good understanding of the clay minerals. The samples were analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM) and X-Ray fluorescence spectrometry (XRF). Mineralogically, the sub-surface Surma Group shales comprise predominantly quartz, plagioclase, illite, chlorite, kaolinite, with lesser amounts of K-feldspar, dolomite and smectite, and minor to trace amounts of calcite, siderite and pyrite. The chemical composition of the <2 μm clay separates also suggests an illite and chlorite-rich composition. With increasing burial depth, the Surma Group shales are enriched in illite. The gradual decreasing of the smectite clays with depth and ultimate disappearance at greater depths (≥ 3000 m) may have been responsible for the presence of the diagenetic illite. Based on the mineralogical composition it is most likely that the illite-chlorite associations together with quartz and feldspar were predominantly detrital in origin and thus reflect the presence of a rapidly-rising source terrain not subjected to intense weathering.  相似文献   
8.
9.
10.
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-23

京公网安备 11010802026262号