全文获取类型
收费全文 | 444篇 |
免费 | 94篇 |
国内免费 | 103篇 |
专业分类
测绘学 | 4篇 |
大气科学 | 345篇 |
地球物理 | 38篇 |
地质学 | 89篇 |
海洋学 | 21篇 |
天文学 | 4篇 |
综合类 | 22篇 |
自然地理 | 118篇 |
出版年
2023年 | 3篇 |
2022年 | 7篇 |
2021年 | 6篇 |
2020年 | 6篇 |
2019年 | 9篇 |
2018年 | 8篇 |
2017年 | 7篇 |
2016年 | 11篇 |
2015年 | 19篇 |
2014年 | 17篇 |
2013年 | 17篇 |
2012年 | 13篇 |
2011年 | 23篇 |
2010年 | 23篇 |
2009年 | 32篇 |
2008年 | 21篇 |
2007年 | 29篇 |
2006年 | 35篇 |
2005年 | 28篇 |
2004年 | 29篇 |
2003年 | 31篇 |
2002年 | 26篇 |
2001年 | 20篇 |
2000年 | 21篇 |
1999年 | 32篇 |
1998年 | 24篇 |
1997年 | 23篇 |
1996年 | 20篇 |
1995年 | 15篇 |
1994年 | 18篇 |
1993年 | 18篇 |
1992年 | 11篇 |
1991年 | 13篇 |
1990年 | 10篇 |
1989年 | 7篇 |
1987年 | 4篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有641条查询结果,搜索用时 31 毫秒
201.
Sum probability analysis of 1275 radiometric ages from 608 archaeological sites across northern and central Australia demonstrates a changing archaeological signature that can be closely correlated with climate variability over the last 2 ka. Results reveal a marked increase in archaeological records across northern and central Australia over the last 2 ka, with notable declines in western and northern Australia between ca. AD 700 and 1000 and post‐AD 1500 – two periods broadly coeval with the Medieval Climatic Anomaly and the Little Ice Age as they have been documented in the Asia–Pacific region. Latitudinal and longitudinal analysis of the dataset suggests the increase in archaeological footprint was continent wide, while the declines were greatest from 9 to 20° S, 110 to 135° E and 143 to 150° E. The change in the archaeological data suggests that, combined with an increase in population over the late Holocene, a disruption or reorganisation of pre‐European resource systems occurred across Australia between ca. AD 700 and 1000 and post‐AD 1500. These archaeological responses can be broadly correlated with transitions of the El Niño–Southern Oscillation (ENSO) mean state on a multi‐decadal to centennial timescale. The latter involve a shift towards the La Niña‐like mean state with wetter conditions in the Australian region between AD 700 and 1150. A transition period in ENSO mean state occurred across Australia during AD 1150–1300, with persistent El Niño‐like and drier conditions to ca. AD 1500, and increasing ENSO variability post‐AD 1500 to the present. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
202.
影响中国及关键经济区热带气旋降水的气候趋势及极端性特征 总被引:3,自引:0,他引:3
本文利用中国气象局上海台风研究所整编的《热带气旋年鉴》(1951~2010年)最佳路径资料,分析影响我国和关键经济区热带气旋(TC)降水量、降水强度以及不同等级降水TC频数的气候变化趋势,研究结果表明,影响全国的TC总降水量的年际变化幅度大,年际差异显著。长江三角洲、珠江三角洲地区影响TC过程雨量年极值自1970年代开始缓慢上升,表明近年来TC引起的极端性降水存在增加的可能。全国范围内自1970年代开始,过程雨量大于250 mm的TC频数也在增加,但长江三角洲、珠江三角洲地区发生极端性降水的TC频数并没有明显的增长。TC造成的24小时降水极值的气候变化趋势不明显,但是1980年代全国范围内的24小时降水极值存在跃变。长江三角洲、珠江三角洲地区日降水极值超过250 mm的TC频数自1980年代开始有缓慢增加趋势。全国范围、长江三角洲及珠江三角洲内TC小时降雨量年极值呈现振荡的周期变化,而在年代际上没有明显的变化趋势。 相似文献
203.
Jun-hui Liu Ji-xi GaoShi-Hai Lv Yong-wei HanYi-huang Nie 《Journal of Arid Environments》2011,75(3):298-308
Meteorological records show a rise in temperature and decrease in precipitation in most parts of the farming-pastoral ecotone of Northern China over the last 50 years. During the last quarter of the 20th Century, the agrarian sector went through a series of reforms and changes in government policies on land use that have led to extensive changes in land cover. The objective of this study was to redefine the location and analyze the boundary variations under the effects of climate and land use changes in the farming-pastoral ecotone of Northern China. The results showed that the location of study area has been redefined as both a climatic ecotone from the perspective of suitability of precipitation and temperature for agricultural crops and vegetation growth, and also a land use ecotone based on the impacts of farmland restructuring by government policies on land use. In recent decades, the climatic boundary has moved southeast while the land use boundary has moved northwest, showing opposing directions of change. The extent of boundary changes in the northeast and northern sections are far greater than in the northwestern section of the farming-pastoral ecotone of Northern China. 相似文献
204.
T.C. Giannini A. TakahasiM.C.M.P. Medeiros A.M. SaraivaI. Alves-dos-Santos 《Journal of Arid Environments》2011,75(9):870-872
Krameria plants are found in arid regions of the Americas and present a floral system that attracts oil-collecting bees. Niche modeling and multivariate tools were applied to examine ecological and geographical aspects of the 18 species of this genus, using occurrence data obtained from herbaria and literature. Niche modeling showed the potential areas of occurrence for each species and the analysis of climatic variables suggested that North American species occur mostly in deserted or xeric ecoregions with monthly precipitation below 140 mm and large temperature ranges. South American species are mainly found in deserted ecoregions and subtropical savannas where monthly precipitation often exceeds 150 mm and temperature ranges are smaller. Principal Component Analysis (PCA) performed with values of temperature and precipitation showed that the distribution limits of Krameria species are primarily associated with maximum and minimum temperatures. Modeling of Krameria species proved to be a useful tool for analyzing the influence of the ecological niche variables in the geographical distribution of species, providing new information to guide future investigations. 相似文献
205.
孙建中 《地球科学与环境学报》1993,(Z2)
这里所指示的大气圈、水圈、岩石圈、生物圈以及人类的作用千变万化,从而对人类的生存造成巨大影响,构成了一个复杂的生态环境,讨论这些问题,对人类生存至关重要。 相似文献
206.
本文以金苞花为例,尝试了组培苗从试管内到自然条件下安全养护的小气候环境模拟并获得成功,提出了“关键阶段,过渡阶段和适应阶段”的三段安全养护措施及其相应的气象条件。这对名贵花卉的商业性生产是有意义的。 相似文献
207.
本文通过成都城市发展前后气候要素变化的对比分析,探索了城市化对成都市气候影响的基本规律,并用统计方法得出了城市“热岛”强度(△T,△Tmin)与城市人口总户数及建成区面积密切相关的客观事实,为改善和治理成都城市气候提供了一定的依据。 相似文献
208.
利用1933~1992年期间成都地面最高气温和地面最大风速年极值的记录,通过统计推断,找出了成都地面最高气温年极值和地面最大风速年极值遵循的渐近分布——Weibul分布和Gumbel分布,并讨论了它们的参数估计方法。 相似文献
209.
Less developed places that are affected by climatic impacts face great challenges to future development. Place-based assessments that look at both the development level and climatic impacts on development are important for understanding the current state of human well-being and generating insights into how to facilitate sustainable development in the future. We carry out an assessment of human well-being in the Poyang Lake Region of China (PLR), using GIS, remote sensing, and socio-economic data. We measure human well-being in three aspects of (i) development level, (ii) exposure of development to flooding, and (iii) sensitivity of development to flooding. Following the United Nations Development Programme's human development index, we examine development through measures of life expectancy, literacy, and income. We first use a digital elevation model and GIS data on levees to map flood hazard in PLR. Based on the flood hazard map, we then derive quantitative measures of exposure and sensitivity of the development in a town to flooding. Our assessment indicates that development in PLR overall is highly exposed and sensitive to flooding. There are significant variations in different aspects of human well-being among the 298 towns in the region. These variations suggest different sustainable development pathways and policy interventions for different places. We discuss the potential usefulness of our approach for other similar places. 相似文献
210.
YANG Zhenjing YANG Qinghu ZHEN Mianping HOU Xianhu BI Zhiwei LIU Linjing 《《地质学报》英文版》2014,88(Z1):440-440
正Since the Quaternary,very thick lacustrine sediments have been deposited in Dalangtan of Qaidam Basin.Based on a study of high-resolution sporopollen analysis on the Dalangtan ZK06 drilling,and paleomagnetic dating 相似文献