全文获取类型
收费全文 | 294篇 |
免费 | 33篇 |
国内免费 | 22篇 |
专业分类
测绘学 | 28篇 |
大气科学 | 18篇 |
地球物理 | 35篇 |
地质学 | 96篇 |
海洋学 | 88篇 |
综合类 | 10篇 |
自然地理 | 74篇 |
出版年
2023年 | 3篇 |
2022年 | 10篇 |
2021年 | 10篇 |
2020年 | 9篇 |
2019年 | 9篇 |
2018年 | 11篇 |
2017年 | 6篇 |
2016年 | 10篇 |
2015年 | 10篇 |
2014年 | 17篇 |
2013年 | 29篇 |
2012年 | 23篇 |
2011年 | 15篇 |
2010年 | 10篇 |
2009年 | 16篇 |
2008年 | 19篇 |
2007年 | 14篇 |
2006年 | 18篇 |
2005年 | 11篇 |
2004年 | 13篇 |
2003年 | 13篇 |
2002年 | 12篇 |
2001年 | 4篇 |
2000年 | 7篇 |
1999年 | 10篇 |
1998年 | 4篇 |
1997年 | 7篇 |
1996年 | 5篇 |
1995年 | 3篇 |
1994年 | 7篇 |
1992年 | 3篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1981年 | 3篇 |
排序方式: 共有349条查询结果,搜索用时 15 毫秒
1.
近年来国产遥感卫星数据增多,但在山地冰川运动速度监测研究中,国产卫星遥感数据的使用却很少。基于此现状,本研究利用"高分一号"卫星数据(GF-1)对藏东南雅弄冰川运动速度进行了提取。通过与同分辨率、同时段的Landsat 8数据进行对比,以及利用非冰川稳定区域的残余位移和冰川主冰流线剖面运动速度两方面,评估了GF-1数据提取的冰川运动速度的精度。结果表明:GF-1数据在非冰川稳定区域的平均偏移量为7.48 m·a~(-1),虽较Landsat 8数据的高(平均偏移量4.58 m·a~(-1)),但小于冰川平均运动速度的5%;GF-1数据与Landsat 8数据在2015年—2016年时段内的冰川主冰流线运动速度变化趋势一致,两者的偏差均方根为7.41 m,小于冰川平均运动速度的5%。研究结果证明了国产高分一号卫星遥感数据在青藏高原山地冰川运动速度监测应用中的可行性。 相似文献
2.
3.
Accompanying economic growth, CO2 emissions have polluted the natural environment worldwide. This study highlights the special problems with stock market development and CO2 emissions in 25 Organization for Economic Cooperation and Development (OECD) countries during 1971–2007 to trace the trend of CO2 emissions while countries grow their economies. A panel‐data model is applied to analyze the relationships between stock market (SM) development, energy consumption, gross domestic product (GDP), and CO2 emissions in 25 OECD countries. Low‐GDP countries show different results from high‐GDP countries in the trends of SM development and CO2 emissions, and dynamic effects occur in SM development and CO2 emissions under various GDP conditions. There is a negative relationship between SM development and CO2 emissions if countries enjoy high economic growth, which means that these countries avoid CO2 emissions through SM development. However, a positive relationship is found between SM development and CO2 emissions if countries experience low economic growth, which means that SM development does not show the boycott‐effect relationship with CO2 emissions when countries experience low levels of economic development. This study shows a correlation between SM development and CO2 emissions among OECD countries. 相似文献
4.
High‐frequency water quality monitoring in an urban catchment: hydrochemical dynamics,primary production and implications for the Water Framework Directive 下载免费PDF全文
Sarah J. Halliday Richard A. Skeffington Andrew J. Wade Michael J. Bowes Emma Gozzard Jonathan R. Newman Matthew Loewenthal Elizabeth J. Palmer‐Felgate Helen P. Jarvie 《水文研究》2015,29(15):3388-3407
This paper describes the hydrochemistry of a lowland, urbanised river‐system, The Cut in England, using in situ sub‐daily sampling. The Cut receives effluent discharges from four major sewage treatment works serving around 190 000 people. These discharges consist largely of treated water, originally abstracted from the River Thames and returned via the water supply network, substantially increasing the natural flow. The hourly water quality data were supplemented by weekly manual sampling with laboratory analysis to check the hourly data and measure further determinands. Mean phosphorus and nitrate concentrations were very high, breaching standards set by EU legislation. Although 56% of the catchment area is agricultural, the hydrochemical dynamics were significantly impacted by effluent discharges which accounted for approximately 50% of the annual P catchment input loads and, on average, 59% of river flow at the monitoring point. Diurnal dissolved oxygen data demonstrated high in‐stream productivity. From a comparison of high frequency and conventional monitoring data, it is inferred that much of the primary production was dominated by benthic algae, largely diatoms. Despite the high productivity and nutrient concentrations, the river water did not become anoxic, and major phytoplankton blooms were not observed. The strong diurnal and annual variation observed showed that assessments of water quality made under the Water Framework Directive (WFD) are sensitive to the time and season of sampling. It is recommended that specific sampling time windows be specified for each determinand, and that WFD targets should be applied in combination to help identify periods of greatest ecological risk. © 2015 The Authors. Hydrological Processes published by John Wiley & Sons Ltd. 相似文献
5.
The aim of the present work is to investigate the distribution of arsenic(As) in sewage ir-rigation area,to deduce the migration and transformation mechanism of As in soil and groundwater,and to infer the source of As in soil and groundwater.This study is carried out in a sewage irrigation area of the Pearl River Delta,China.Surface water samples,soil samples,and groundwater samples from sewage irrigation area were analyzed for As and other elements.As contents in water samples were analyzed by hydride gene... 相似文献
6.
注水开发是提高陕北浅层低孔特低渗油藏最终采收率和开发效益的主要方式。随着开发工作的开展,油田污水已成为注水开发的主要水源,污水的处理、污水回注和再利用是油田可持续高效发展的关键问题之一。针对南泥湾低渗油藏脱后污水及池塘污水化验结果,通过对絮凝剂、助凝剂、杀菌剂、缓蚀阻垢剂、除氧剂、浮选剂种类及加药量的优选,进行了回注污水处理研究。结果表明:按照所筛选出的各种水处理剂选型及浓度选择混合后,配伍性良好,处理后的污水水质各项指标均达到延长低渗透油藏注入水推荐标准,可满足南泥湾油田特低渗油藏注水开发要求。研究结果可为陕北浅层低渗油田污水处理及注水方案优化提供理论依据。 相似文献
7.
随着城市的发展和能源需求的增长,污水的热能回收利用越来越受到关注,开发污水源热泵技术对建筑节能降耗具有重要意义。本文就污水源热泵系统的工作原理、特点等方面进行了介绍,阐述了国内外污水源热泵技术的开发利用历程与工程现状,分析了城市污水热能资源潜力以及污水源热泵技术的发展前景,指出利用污水与环境的温差获取热能具有十分巨大的能量资源前景,适宜的热源距离是污水源热泵开发利用的先决条件,开发污水源热泵系统,可以充分利用城市污水处理厂的二级出水或城市污水作为水源,通过合理利用出水的流量和温差为城市住宅供暖。基于我国能源与环境的现状,污水源热泵系统具有良好的市场前景,是一种值得推广的能源开发利用方式。 相似文献
8.
9.
10.
优越的地理位置和丰富的旅游资源使得河南的旅游业快速发展,对旅游业发展进行预测可以为旅游业发展决策提供帮助。运用灰色系统理论的灰色关联度分析法,对河南省旅游业的影响因子进行定量分析,得知影响河南旅游业发展的三大因素是国内生产总值、人均国内生产总值和民用汽车数量。建立河南国内旅游接待人数和国内旅游收入的灰色GM(1,1)预测模型。结果表明,未来5年河南省旅游业发展势头强劲。 相似文献