全文获取类型
收费全文 | 4969篇 |
免费 | 921篇 |
国内免费 | 1974篇 |
专业分类
测绘学 | 75篇 |
大气科学 | 1058篇 |
地球物理 | 753篇 |
地质学 | 2968篇 |
海洋学 | 2082篇 |
天文学 | 22篇 |
综合类 | 217篇 |
自然地理 | 689篇 |
出版年
2024年 | 25篇 |
2023年 | 86篇 |
2022年 | 245篇 |
2021年 | 219篇 |
2020年 | 231篇 |
2019年 | 281篇 |
2018年 | 243篇 |
2017年 | 280篇 |
2016年 | 273篇 |
2015年 | 267篇 |
2014年 | 366篇 |
2013年 | 461篇 |
2012年 | 298篇 |
2011年 | 331篇 |
2010年 | 237篇 |
2009年 | 351篇 |
2008年 | 394篇 |
2007年 | 366篇 |
2006年 | 366篇 |
2005年 | 328篇 |
2004年 | 311篇 |
2003年 | 264篇 |
2002年 | 245篇 |
2001年 | 193篇 |
2000年 | 184篇 |
1999年 | 170篇 |
1998年 | 137篇 |
1997年 | 137篇 |
1996年 | 98篇 |
1995年 | 72篇 |
1994年 | 115篇 |
1993年 | 76篇 |
1992年 | 44篇 |
1991年 | 41篇 |
1990年 | 19篇 |
1989年 | 23篇 |
1988年 | 17篇 |
1987年 | 12篇 |
1986年 | 13篇 |
1985年 | 11篇 |
1984年 | 8篇 |
1983年 | 5篇 |
1982年 | 8篇 |
1981年 | 3篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1954年 | 2篇 |
排序方式: 共有7864条查询结果,搜索用时 171 毫秒
221.
The geography of water conflict and cooperation: internal pressures and international manifestations 总被引:2,自引:0,他引:2
Studies on transboundary water conflict and cooperation generally consider interstate relations over shared water resources as distinct from intrastate relations. While connections have been made between international water relations and regional relationships in general, it is conceivable that international water conflict and cooperation may also be influenced by domestic water events and vice versa. This paper seeks to investigate the dynamics of water interactions across geographic scale and their relationship to broader international affairs. The research approach involves the creation of an analytical framework for assessing possible linkages between external and internal interactions over freshwater resources. The framework is applied to three case studies – the Middle East, South Asia and Southern Africa – utilizing 'event data'. To validate the findings from the quantitative analyses, the results are compared with conventional qualitative understandings of water and overall relations in the three regions. The comparison demonstrates not only the efficacy of the analytical framework in general, but also highlights, at least in terms of the specific case studies selected, the disparate water dynamics across geographic regions and the importance of considering water events, both national and international, within larger political and historical contexts. 相似文献
222.
Karen Bakker 《The Geographical journal》2003,169(4):328-341
This paper examines the interrelationship between urbanization and water supply privatization in cities in the global South. The purpose of the paper is not to evaluate the impacts of privatization; rather, the paper analyses the differences in pathways and modes of water supply privatization, focusing on urban and contrasting with rural areas. A distinction is drawn between privatization (organizational change) and commercialization (institutional change) of water supply. Emphasis is placed upon the interrelationship between regulatory change (a shift from public to private management of water supply systems), human use of and access to water, and urban waterscapes. In contrast to metaphors of 'networks' so often applied in analyses of water management, the 'archipelago' is posited as a metaphor which better captures the complex overlapping strategies of water supply provision in urban areas in the South. Building on this metaphor, and in response to the 'public–private' dualism often invoked in studies of privatization, the paper outlines an alternative typology of water management in urban areas in the South. This typology foregrounds the concepts of the territorialization of corporate power as a means of understanding the articulation between privatization and urbanization processes in the South. 相似文献
223.
224.
试论经济全球化对非洲华人经济的影响 总被引:1,自引:0,他引:1
经济全球化使越来越多的国家和地区,甚至是一个经济体和一个经济单位都主动或被动地参与到世界经济中来,非洲的华人经济也不例外。鉴于目前有关华人经济的文章主要集中在东南亚地区和美国与欧洲,很少有人探讨过非洲华人经济的情况,所以本文试图通过经济全球化条件下的非洲经济、中非经济关系和华商对非洲的投资,来论述经济全球化对非洲华人经济的影响。 相似文献
225.
Karen Brown 《Area》2003,35(4):343-356
Focusing on the contested issue of trees and forests, this paper looks at various ways in which historians have explored environmental change and human agency in Africa. It looks in particular at the colonial period and positions the case of the Cape Colony (South Africa) in a broader historiographical context. Colonial silviculture involved both the appropriation of the natural forests and the creation of exotic plantations. These policies generated a mixture of reactions from African communities and had varying effects on the environment. Colonial science and the projects it gave rise to have since been critiqued, contributing to the promotion of community-based forestry schemes that try to incorporate indigenous knowledge and ideas about land use. 相似文献
226.
Representing environments in flux: case studies from East Africa 总被引:1,自引:0,他引:1
The dominant view in the ecology and anthropology of the 1950s saw populations harmoniously interacting in self-regulating systems; climax forests and stable societies were the ruling hypotheses. Now, however, ecology and social sciences are investigating nature and culture in flux. The flux paradigms of nature and culture describe a human–ecological relationship that is non-equilibrial, historically contingent and constantly negotiated at both material and ideological levels by unequal actors. In this paper, we examine the effect of changing ecological and cultural paradigms on interpretations of environmental change in three areas of East Africa: the North Pare Mountains, Tanzania, the Mkomazi Game Reserve, Tanzania and the Tsavo National Park, Kenya. We explore how discursive and materialist approaches can complement one another, by expanding the domains of ecological inquiry and demanding that analysts cross-check their data for unquestioned assumptions regarding stability, variability and spatial and temporal scales. Rather than testing a ruling hypothesis, we suggest that ecologists and social scientists work with multiple hypotheses, with the aim of understanding the interplay between ecological, environmental and social influences. 相似文献
227.
华南热水成因硅质岩建造的稀土元素地球化学特征 总被引:11,自引:2,他引:11
本文在华南地区若干个重要层位热水成因硅质岩建造的稀土元素地球化学数据的基础上,讨论了热水成因硅质岩的REE特征及其与形成环境的关系。指出典型热水沉积建造的δCe为负异常,而δEu为正异常,且LREE>HREE;这种热水成因的硅质岩REE总量普遍较低,且有从热水喷口向外REE总量增高的趋势。热水成因硅质泥岩与正常沉积成因硅质泥的混合存在使稀土元素分布状况变得更复杂。 相似文献
228.
229.
230.