全文获取类型
收费全文 | 617篇 |
免费 | 108篇 |
国内免费 | 175篇 |
专业分类
测绘学 | 95篇 |
大气科学 | 203篇 |
地球物理 | 86篇 |
地质学 | 263篇 |
海洋学 | 112篇 |
天文学 | 7篇 |
综合类 | 53篇 |
自然地理 | 81篇 |
出版年
2024年 | 6篇 |
2023年 | 17篇 |
2022年 | 29篇 |
2021年 | 31篇 |
2020年 | 35篇 |
2019年 | 31篇 |
2018年 | 20篇 |
2017年 | 35篇 |
2016年 | 35篇 |
2015年 | 39篇 |
2014年 | 44篇 |
2013年 | 35篇 |
2012年 | 42篇 |
2011年 | 36篇 |
2010年 | 31篇 |
2009年 | 45篇 |
2008年 | 28篇 |
2007年 | 63篇 |
2006年 | 33篇 |
2005年 | 31篇 |
2004年 | 35篇 |
2003年 | 22篇 |
2002年 | 25篇 |
2001年 | 25篇 |
2000年 | 20篇 |
1999年 | 23篇 |
1998年 | 13篇 |
1997年 | 11篇 |
1996年 | 13篇 |
1995年 | 6篇 |
1994年 | 6篇 |
1993年 | 5篇 |
1992年 | 8篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1987年 | 1篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1979年 | 1篇 |
排序方式: 共有900条查询结果,搜索用时 484 毫秒
521.
Fleming LE Broad K Clement A Dewailly E Elmir S Knap A Pomponi SA Smith S Solo Gabriele H Walsh P 《Marine pollution bulletin》2006,53(10-12):545-560
There has been an increasing recognition of the inter-relationship between human health and the oceans. Traditionally, the focus of research and concern has been on the impact of human activities on the oceans, particularly through anthropogenic pollution and the exploitation of marine resources. More recently, there has been recognition of the potential direct impact of the oceans on human health, both detrimental and beneficial. Areas identified include: global change, harmful algal blooms (HABs), microbial and chemical contamination of marine waters and seafood, and marine models and natural products from the seas. It is hoped that through the recognition of the inter-dependence of the health of both humans and the oceans, efforts will be made to restore and preserve the oceans. 相似文献
522.
国际航空气象预报的发展趋势 总被引:3,自引:0,他引:3
结合国际上最新的航空气象预报产品或项目,介绍了美国、加拿大及欧洲在航空气象预报方面的最新进展和未来的发展趋势。综合来看,未来航空气象预报将更多地基于网络技术,逐渐走向半自动化和自动化;将更多地使用概率预报;形式也将更加多样化,图形格式的预报产品将有越来越大的比率。在航空用户业务系统中,预报产品最终将成为集成的决策辅助工具;在协同决策中的所有参与者使用统一的预报产品;针对不同的航空用户提供不同的预报产品将是未来气象服务的一个主要方向。 相似文献
523.
长治市2006年8月28日出现了暴雨天气过程,对该次暴雨的500hPa天气形势和700hPa切变影响系统进行了分析。并进一步对强降水主要集中时段的T213数值预报产品的相对湿度场、K指数场,FY-2C云区相对湿度廓线以及多普勒雷达降水回波特征进行了综合诊断,给出了该次暴雨的主要着眼点,为今后暴雨预报提供一些思路。 相似文献
524.
伐木制品碳储量对森林生态系统和大气之间的碳平衡起着至关重要的作用,伐木制品替代化石燃料,以及延长产品使用寿命对于减缓温室气体的排放具有很大的潜力。因此,伐木制品的碳储量议题已被列为《联合国气候变化框架公约》谈判的重要议题,并且将成为今后林业议题谈判的重要内容之一。在参与林业议题谈判和分析相关谈判资料的基础上,对各主要谈判方的观点作了简要总结,指出了目前该议题谈判存在的主要问题,并指出了今后谈判和研究的主要方向以及我国谈判的建议,以期为我国今后的履约战略提供支持。 相似文献
525.
Food commodities, geographical knowledges and the reconnection of production and consumption: The case of naturally embedded food products 总被引:1,自引:0,他引:1
This paper focuses on a particular group of food commodities, associated with the wider turn to ‘alternative food networks’, that are described as ‘naturally embedded food products’ (NEFPs). These are commodities (specifically meats and cheeses) that utilise grassland biodiversity as an input into production to positively influence, in various ways, the final qualities of the commodity. Building on the geographical literature on commodity circuits and analysing data derived from NEFP promotional materials and focus groups with urban and rural residents in the UK, the paper interrogates the geographical knowledges that are deployed by producers in the promotion of NEFPs and how these knowledges are accommodated and contested by consumers as they bring their own geographical knowledges to the interpretation of these commodities. The paper undertakes this task in order to problematise the extent to which alternative food networks in general and NEFPs in particular are bringing about a reconnection of producers and consumers and, concomitantly, a defetishisation of food, as is claimed for them by many of their policy and academic proponents. In the process the paper reveals how the food commodities associated with alternative food networks entail the creation of new and rival fetishes paradoxically as a result of efforts to ‘thicken connections’ between the production and consumption of food. 相似文献
526.
527.
528.
529.
Yunqiao Shu Simon Stisen Karsten H. Jensen Inge Sandholt 《International Journal of Applied Earth Observation and Geoinformation》2011
Data from the first operational Chinese geostationary satellite Fengyun-2C (FY-2C) satellite are applied in combination with Moderate Resolution Imaging Spectroradiometer (MODIS) satellite products for the assessment of regional evapotranspiration over the North China Plain. The approach is based on the improved triangle method, where the temperature–vegetation index space includes thermal inertia. Two thermal infrared channels from FY-2C are used to estimate surface temperature (Ts) based on a split window algorithm originally proposed for the MSG-SEVIRI sensor. Subsequently the high temporal resolution of FY-2C data is exploited to give the morning rise in Ts. Combined with the 16 days composite MODIS vegetation indices product (MOD13) at a spatial resolution of 5 km, evaporative fraction (EF) is estimated by interpolation in the ΔTs–NDVI triangular-shaped scatter space. Finally, regional actual evapotranspiration (ET) is derived from the evaporative fraction and available energy estimated from MODIS surface albedo products MCD43. Spatial variations of estimated surface variables (Ts, EF and ET) corresponded well to land cover patterns and farmland management practices. Estimated ET and EF also compared well to lysimeter data collected for the period June 2005–September 2007. The improved triangle method was also applied to MODIS products for comparison. Estimates based on FY-2C products proved to provide slightly better results than those based on MODIS products. The consistency of the estimated spatial variation with other spatial data supports the use of FY-2C data for ET estimation using the improved triangle method. Of particular value is the high temporal frequency of image acquisitions from FY-2C which improves the likelihood of obtaining cloud free image acquisitions as compared to polar orbiting sensors like MODIS. 相似文献
530.
Throughout history, humans have transformed natural forests into agricultural land, settlement areas and managed forests. Studies on the dynamics of forest change are one of the mainstays in land change science. The forest transition theory offers a powerful tool to analyze changes in human interference with forests. At the national level, a range of factors have been found to influence a country's forest change. The role of international wood product trade has, however, rarely been studied based on empirical data. We offer a global assessment of how this trade helps shape observed forest change, by relating forest stock change to net trade of wood products for the period 1997-2007 and by localizing the origin of wood consumed in a given nation. For many nations, traded wood products have a relevant impact on the course of ongoing forest transitions. We develop a general typology of how wood product trade can influence forest change and place various nations within this framework. We find that many wealthy nations with returning forests seem to accelerate this return by importing wood products. These imports appear to be provided by two main types of wood exporters: (a) by wealthy countries with low population densities and stable forests and (b) by relatively poor countries with declining forests, employing increasing population and welfare levels. We discuss these findings in the light of general theories on land use transitions and forest change and conclude by highlighting implications for national forest policies and global environmental governance, aiming at reducing negative impacts of wood products and enhancing the positive role they can play in replacing more fossil fuel intensive products. 相似文献