全文获取类型
收费全文 | 216篇 |
免费 | 28篇 |
国内免费 | 42篇 |
学科分类
地球科学 | 286篇 |
出版年
2024年 | 3篇 |
2023年 | 3篇 |
2022年 | 1篇 |
2021年 | 9篇 |
2020年 | 10篇 |
2019年 | 22篇 |
2018年 | 14篇 |
2017年 | 11篇 |
2016年 | 9篇 |
2015年 | 16篇 |
2014年 | 9篇 |
2013年 | 15篇 |
2012年 | 15篇 |
2011年 | 11篇 |
2010年 | 9篇 |
2009年 | 13篇 |
2008年 | 18篇 |
2007年 | 9篇 |
2006年 | 6篇 |
2005年 | 9篇 |
2004年 | 7篇 |
2003年 | 5篇 |
2002年 | 6篇 |
2001年 | 3篇 |
2000年 | 4篇 |
1999年 | 5篇 |
1998年 | 1篇 |
1997年 | 6篇 |
1996年 | 7篇 |
1995年 | 1篇 |
1994年 | 9篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 7篇 |
1988年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1978年 | 1篇 |
排序方式: 共有286条查询结果,搜索用时 15 毫秒
1.
The gastropod limpet, Cellana grata, is common on moderately exposed to exposed Hong Kong rocky shores. On the basis of the existing literature on trace metal contamination in Hong Kong, four sites were identified, representative of highly polluted (Aberdeen and Lei Yue Mun) and clean (Cape d'Aguilar and Clear Water Bay) conditions. Limpets from the two polluted sites showed similar, but significantly higher body concentrations of copper than limpets from the two clean sites, which were also similar. Non-invasive measurements of cardiac activity of limpets from the four sites showed between site differences in baseline heart rates under standard seawater, irrespective of pollution level. When acutely exposed to water borne copper (2 h, 0.5+/-0.06 SD ppm), however, limpets from clean sites showed a significantly higher increase in inter-beating time (bradycardia) than those from polluted sites. These results highlight the potential use of cardiac activity to assess the exposure of natural populations of limpets to trace metal pollution. 相似文献
2.
LAS格式解析及其扩展域的应用 总被引:2,自引:0,他引:2
激光雷达是近年来兴起的一种快速获取地物目标三维信息的主动遥感技术。其采集的离散激光点具有数据量大,信息丰富等特点。目前常用的LIDAR数据存储格式,在存储LIDAR数据时存在种种不足,且数据交换和共享困难。LAS格式是ASPRS制定的标准LIDAR数据交换格式,能较好地解决多属性离散激光点数据的存储问题,具有结构严谨,便于扩展等优点。本文在对LAS格式进行解析的基础上,针对LAS变长记录的扩展域,介绍了一些实际的应用。 相似文献
3.
勉略宁三角地区是我国西北重要的铜-金多金属成矿远景区之一,已发现多种类型的铜、铁、铅、锌、金和银等多金属矿床(点)多达上百处,除金矿床为大一超大型外(煎茶岭和李家沟金矿床),铜-金多金属矿床多与中酸性侵入体有关,但规模均不大(中-小型),其中规模最大的铜厂铜矿床也不过为中型,远景储量为大型. 相似文献
4.
Demographic transition in Sri Lanka: a spatial perspective 总被引:1,自引:0,他引:1
Fuller GA 《Population geography : a journal of the Association of Population Geographers of India》1984,6(1-2):1-11
Demographic transition theory involves a lagging fertility transition induced by a leading mortality transition. This article focuses on the linkage between the mortality and fertility transitions in Sri Lanka; it discusses the measurement of areal fertility, demonstrates the use of a measure not commonly used in population geography, and shows areal association between past mortality and recent fertility. The Coale or Princeton fertility indices allow a reasonably good view of structural and behavioral aspects of fertility; the Coale indices examine the contribution of structure to total fertility and the contribution of marital fertility. Although recent fertility decline has been less rapid than the post-war mortality decline, Sri Lanka's crude birth rate in 1975 was the 5th lowest in Asia. Sri Lanka experienced very high crude death rates in 1930, and quite low rates in 1950 and in subsequent years. This demonstrates an association between historic mortality and recent fertility, and that association can be linked deductively to demographic transition theory. In 1930, malaria was endemic throughout the Dry Zone of Sri Lanka, and hyperendemic in several districts. The Spearman rank correlation coefficients reveal the strongest relationship between malaria and nuptiality; this lends evidence to the notion that structural influences on fertility--such as delayed marriage--are more important than influences on marital fertility--such as coital frequency. The evidence suggests that mortalily decline in Sri Lanka led to an increase in fertility in those areas where malaria had been concentrated. This suggests the possibility that measures constituting malaria control or eradication also stimulate increased fertility; therefore, anti-malarial programs must be integrated with family planning. 相似文献
5.
给出了某些地震前地电的观测结果。数据是在帕特雷大学地震中心用VAN方法在3年独立实验研究期间搜集的。记录的信号包括:(a)地电场的缓慢变化;(b)地电场的周期变化;(c)地震电信号。 相似文献
6.
7.
8.
10.