全文获取类型
| 收费全文 | 816篇 |
| 免费 | 134篇 |
| 国内免费 | 58篇 |
专业分类
| 测绘学 | 37篇 |
| 大气科学 | 19篇 |
| 地球物理 | 175篇 |
| 地质学 | 435篇 |
| 海洋学 | 7篇 |
| 天文学 | 19篇 |
| 综合类 | 34篇 |
| 自然地理 | 282篇 |
出版年
| 2023年 | 4篇 |
| 2022年 | 36篇 |
| 2021年 | 54篇 |
| 2020年 | 42篇 |
| 2019年 | 47篇 |
| 2018年 | 38篇 |
| 2017年 | 50篇 |
| 2016年 | 42篇 |
| 2015年 | 49篇 |
| 2014年 | 44篇 |
| 2013年 | 50篇 |
| 2012年 | 59篇 |
| 2011年 | 52篇 |
| 2010年 | 42篇 |
| 2009年 | 34篇 |
| 2008年 | 40篇 |
| 2007年 | 47篇 |
| 2006年 | 32篇 |
| 2005年 | 30篇 |
| 2004年 | 30篇 |
| 2003年 | 25篇 |
| 2002年 | 15篇 |
| 2001年 | 16篇 |
| 2000年 | 19篇 |
| 1999年 | 21篇 |
| 1998年 | 9篇 |
| 1997年 | 14篇 |
| 1996年 | 7篇 |
| 1995年 | 5篇 |
| 1994年 | 9篇 |
| 1993年 | 7篇 |
| 1992年 | 6篇 |
| 1991年 | 7篇 |
| 1990年 | 7篇 |
| 1989年 | 7篇 |
| 1988年 | 8篇 |
| 1987年 | 1篇 |
| 1985年 | 1篇 |
| 1982年 | 1篇 |
| 1977年 | 1篇 |
排序方式： 共有1008条查询结果，搜索用时 15 毫秒
31.
Discharge‐sediment processes of the Zhadang glacier on the Tibetan Plateau measured with a high frequency data acquisition system 
下载免费PDF全文
下载免费PDF全文 In high elevation cold regions of the Tibetan Plateau, suspended sediment transfer from glacier meltwater erosion is one of the important hydrological components. The Zhadang glacier is a typical valley‐type glacier in the Nyainqentanglha Mountains on the Tibetan Plateau. To make frequent and long period records of meltwater runoff and sediment processes in the very high elevation and isolated regions, an automatic system was installed near the glacier snout (5400 m a.s.l) in August 2013, to measure the transient discharge and sediment processes at 5‐min interval, which is shorter than the time span for the water flow to traverse the catchment from the farthest end to the watershed outlet. Diurnal variations of discharge, and suspended sediment concentration (SSC) were recorded at high frequency for the Zhadang glacier, before suspended sediment load (SSL) was computed. Hourly SSC varied from the range of 0.2 kg/m3 to 0.5 kg/m3 (at 8:00–9:00) to the range of 2.0 kg/m3 to 4.0 kg/m3 (at 17:00–18:00). The daily SSL was 32.24 t during the intense ablation period. Hourly SSC was linearly correlated with discharge (r = 0.885**, n = 18, p < 0.01). A digit‐eight hysteresis loop was observed for the sediment transport in the glacier area. Air temperature fluctuations influence discharge, and then result in the sediment variations. The results of this study provide insight into the responses of suspended sediment delivery processes with a high frequency data in the high elevation cold regions. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
32.
Sophie Cauvy‐Fraunié Patricio Andino Rodrigo Espinosa Roger Calvez Fabien Anthelme Dean Jacobsen Olivier Dangles 《水文研究》2014,28(6):3008-3017
Equatorial glacier‐fed streams present unique hydraulic patterns when compared to glacier‐fed observed in temperate regions as the main variability in discharge occurs on a daily basis. To assess how benthic fauna respond to these specific hydraulic conditions, we investigated the relationships between flow regime, hydraulic conditions (boundary Reynolds number, Re*), and macroinvertebrate communities (taxon richness and abundance) in a tropical glacier‐fed stream located in the high Ecuadorian Andes (> 4000 m). Both physical and biotic variables were measured under four discharge conditions (base‐flow and glacial flood pulses of various intensities), at 30 random points, in two sites whose hydraulic conditions were representative to those found in other streams of the study catchment. While daily glacial flood pulses significantly increased hydraulic stress in the benthic habitats (appearance of Re* > 2000), low stress areas still persisted even during extreme flood events (Re* < 500). In contrast to previous research in temperate glacier‐fed streams, taxon richness and abundance were not significantly affected by changes in hydraulic conditions induced by daily glacial flood pulses. However, we found that a few rare taxa, in particular rare ones, preferentially occurred in highly stressed hydraulic habitats. Monte‐Carlo simulations of benthic communities under glacial flood reduction scenarios predicted that taxon richness would be significantly reduced by the loss of high hydraulic stress habitats following glacier shrinking. This pioneer study on the relationship between hydraulic conditions and benthic diversity in an equatorial glacial stream evidenced unknown effects of climate change on singular yet endangered aquatic systems. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
33.
34.
35.
36.
Currently, one of the effective means in monitoring glacier change in regional scale is remote sensing and site-observation method. In this article, we present a study of comparing glacier area in 2005 derived from SPOT5 satellite image with area in 1972 derived from topographic maps. Moreover, Miaoergou (庙儿沟) flat-summit glacier is site observed to verify glacial change in regional scale. During the study period, glaciers located in the southern slope of Kalik (喀尔里克) Mountain re-duced their area by 12.3%. ... 相似文献
37.
冰川面积是监测冰川变化信息的重要参数。本文以各拉丹东地区为例,根据冰川区域特有的纹理特征,选取时间间隔为35天的ENVISAT ASAR干涉对,利用灰度共生矩阵提取纹理特征,通过波段组合进行监督分类,进而提取研究区冰川面积。同时以Landsat TM光学影像为依据,评价利用纹理特征提取结果的精度。研究表明:基于纹理特征并利用SAR影像提取冰川面积的方法是可行的,为提取冰川信息提供了又一可靠手段。 相似文献
38.
Snow chemistry on the glaciers of alpine regions is a good indicator of atmospheric environmental change.We examine snow chemistry in three snowpits at different altitudes on the Haxilegen Glacier No.51,in the Kuitun River source,Tian Shan,China,during July-September 2004 to 2007.We use correlation analysis,factor analysis and sea-salt tracing methods to examine the characteristics and sources of major ions and mineral dust particles in the snow.Results show that mineral dust particles and major ions in the snow pits vary seasonally.During the Asian dust period in springtime,the concentration of mineral dust particles and major ions deposited in snow is high,while the concentration is relatively low during the non-dust period of summer and autumn.This may be caused by dust storm activity in central Asia.The order of major ionic concentrations in the snow packs was determined to be Ca2+ > SO42-> NH4+ > NO3-> Cl-> Na+ > Mg2+ > K+.Ca2+ was the dominant cation;SO42- was the dominant anion.We find,with the exception of NO3-,that the variabilities of ionic concentrations are highly correlated.Results show that the glacier region was significantly affected by dust activity and anthropogenic source.The major ions,especially Na+,originate from dust sources of central Asia and from the Ocean,transported by the westerly winds. 相似文献
39.
40.
Atmospheric air temperature data from 92 stations in China’s radiosonde network were used to analyze changes in the freezing
level height (FLH), glacier snow line, and ice edge from 1958–2005 (48 years) and to examine the impact of these changes on the
cryosphere. In general, the FLH, glacier snow line, and ice edge exhibited latitudinal zonation, declining from south to north.
Trends in the FLH, glacier snow line, and ice edge showed spatial heterogeneity during the study period, with prevailing upward
trends. Temporally, the FLH, glacier snow line, and ice edge trends differed on various time scales. 相似文献