全文获取类型
收费全文 | 936篇 |
免费 | 154篇 |
国内免费 | 160篇 |
专业分类
测绘学 | 15篇 |
大气科学 | 243篇 |
地球物理 | 154篇 |
地质学 | 441篇 |
海洋学 | 102篇 |
天文学 | 5篇 |
综合类 | 20篇 |
自然地理 | 270篇 |
出版年
2024年 | 7篇 |
2023年 | 13篇 |
2022年 | 23篇 |
2021年 | 28篇 |
2020年 | 27篇 |
2019年 | 38篇 |
2018年 | 26篇 |
2017年 | 38篇 |
2016年 | 47篇 |
2015年 | 37篇 |
2014年 | 48篇 |
2013年 | 50篇 |
2012年 | 40篇 |
2011年 | 35篇 |
2010年 | 32篇 |
2009年 | 46篇 |
2008年 | 78篇 |
2007年 | 73篇 |
2006年 | 65篇 |
2005年 | 54篇 |
2004年 | 59篇 |
2003年 | 61篇 |
2002年 | 48篇 |
2001年 | 45篇 |
2000年 | 26篇 |
1999年 | 32篇 |
1998年 | 27篇 |
1997年 | 29篇 |
1996年 | 22篇 |
1995年 | 20篇 |
1994年 | 15篇 |
1993年 | 8篇 |
1992年 | 6篇 |
1991年 | 10篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1977年 | 1篇 |
排序方式: 共有1250条查询结果,搜索用时 140 毫秒
211.
212.
The adoption of the proposed European Marine Strategy Directive is an opportunity for a comprehensive policy for protecting, improving and sustainably using Europe's environmentally degraded seas. It calls for an ecosystem-based approach to management where humans are regarded as a key system component. Although the proposed wording has been the subject of fierce debate, the central policy goal remains achieving "Good Environmental Status". The interpretation of "good" is key to implementation and relates to human values and worldviews. We demonstrate how these vary widely across Europe. Solution of fundamental considerations such as the assignation of reference states, the balance between precautionary and evidence-based action, the degree of subsidiarity, and conservation strategies including marine protected areas, will ultimately depend upon public understanding, involvement in and support for the Directive. The social element, critical to effective adaptive management, requires greater attention within the context of a regional seas geographical framework. 相似文献
213.
Stefan Bouzarovski 《Area》2009,41(4):452-463
Energy developments in the post-Communist states of Eastern and Central Europe (ECE) have a major impact on global energy security and sustainability, thanks to this region's key geographical position between the energy-exporting states of the former Soviet Union, on the one hand, and the energy-importing states of Western and Southern Europe, on the other. At the same time, post-socialist reforms of energy industries in this region provide unique insights into the complex relations of power, economic transformation and spatial inequality that govern energy production and consumption. This paper therefore aims to provide an initial look at some of the theoretical and policy issues that underpin the emergent 'geographies' of energy reform in ECE, as well as their embeddedness in relations of power stemming from organisational, infrastructural and economic inequalities in the region. It employs an analysis of local news reports, policy papers and statistical data to examine the intricate institutional networks and spatial formations that have governed the energy transformation process. In broader terms, the paper aims to emphasise the important role that human geography can play in making sense of the territorial differences and frictions that have emerged during the post-socialist reform process, while challenging the idea of a 'neat' neoliberal transition from a centrally planned to a market-based mode of energy regulation . 相似文献
214.
通过对穿越西北次海盆的3条地震测线以及一条深反射地震剖面的解释,对其新生代的构造 沉积特征进行研究,探讨了伸展模型,并进而对其新生代的构造演化过程和动力学机制进行了分析。结果显示:西北次海盆在30 Ma时开始发育,断层的活动期集中在渐新世,并大致以海盆中部的岩浆岩凸起为轴对称分布,对渐新统的沉积起控制作用。海盆扩张东强西弱,西部显示出更多的陆缘裂谷盆地的特征。25 Ma后扩张轴向南跃迁,西北次海盆的海底扩张运动停止,进入裂后沉降阶段。构造展布方向受到其南侧的中-西沙地块的影响,大致沿其北部边界展布。深反射地震剖面所反映的深部地壳结构也显示出大致沿海盆中轴对称的特征,显示研究区很可能为纯剪的变形模式。 相似文献
215.
Hans-Joachim Bürkner 《GeoJournal》2000,50(2-3):105-108
Migration flows from western Europe, the United States and Canada to east central Europe have received little attention so
far. But numbers are now considerable and in the context of globalisation it seems appropriate to conceptualise communities
of Westerners in terms of transnational social spaces as defined by Glick Schiller et al. Study of Americans in Prague reveals
three main groups: enterprise managers, lifestyle migrants and entrepreneurs in small and medium-sized enterprises. All are
engaged in a variety of different processes of community-building, often with clear trends towards a new transnationalism.
Yet, the individual attempt to live in two societies is limited by the marked boundaries of the communities and by the degree
of social exclusion which they experience from the majority population.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
216.
217.
西北地区生态环境建设和水资源可持续利用的若干问题 总被引:32,自引:19,他引:13
通过水资源特征分析及水资源利用的评价, 论述了水资源持续利用可持续发展存在的水资源紧缺、生态环境恶化等问题。提出了水资源利用可持续发展对策: 开源节流、以节水为主, 坚持水费改革, 改善生态环境等措施。认为西北地区社会经济要发展, 保护和改善生态环境是前提, 水资源可持续利用是关键。只有珍惜、保护、合理利用和科学管理水资源, 重视保护和改善生态环境, 解决好生态环境建设的体制、机制和投资, 提高其效益, 才能确保水资源的可持续利用, 促进西北社会经济可持续发展。 相似文献
218.
西北地区的退耕规模、粮食响应及政策建议 总被引:19,自引:0,他引:19
退耕还林(草)是西北地区生态环境建设的重大举措,但退耕必然会对的粮食生产带来直接影响。基于全国土地利用详查的分县数据,研究认为:(1)按照法律规定,大于25度的陡坡耕地必须无条件地退耕。仅此一项,西北地区就必须退耕153.6×104hm2,占现有耕地的9.2%,粮食减产为71.2×104t,占1996年粮食产量的2.2%,对全区人均粮食占有量的影响很小;(2)在保证人均耕地0.1hm2前提下对大于15度的坡耕地退耕,则退耕面积可达347.8×104hm2,超过现有耕地的1/5;对应的粮食减产为234.5×104t,是1996年粮食产量的7.3%,甘肃、陕西和青海的粮食减产比例都在1/10左右,退耕带来的直接粮食减产效应是显而易见的。最后针对西北地区的退耕规模及其粮食响应,提出了两条政策建议 相似文献
219.
Mountain Water Tower and Ecological Risk Estimation of the Mesta-Nestos Transboundary River Basin (Bulgaria-Greece) 总被引:2,自引:1,他引:1
K. Grunewald J. Scheithauer J.-M. Monger N. Nikolova 《山地科学学报》2007,4(3):209-220
The Mesta-Nestos river basin in Bulgaria and Greece is a case study for transboundary decision-making support in south-eastern Europe and a show-case for the development of methodologies and information-gathering for the integrated regional planning of water resources. Land-use conflicts in this water-scarce region cover a wide spectrum of activities like agricultural irrigation,drinking water production,diversions for industrial water,and risk of pollution from mining,to name a few examples. Measurements of the water quality were carried out in the upper basin. Results will be illustrated by the example of the environmental situation in the alpine region of the Pirin National Park as well as in the Razlog Basin with a stronger anthropogenic impact and pollution around a former uranium mine near the village of Ele?nica. The social and economic development of this transboundary region is a recently established priority for the future. It will mean an increase in water usage and more stress for the water resources if regional impacts of global climate change are verified. Problem-focused management of the catchment area as a whole on the basis of proved geo-data sets is needed for the future. 相似文献
220.
西北干旱区地气温差季节和年际变化特征的分析 总被引:11,自引:4,他引:7
利用西北干旱区49个气象站1961—2000年0 cm地温和气温月平均资料,采用逐级归并法、小波分析、经验正交函数(EOF)、旋转经验正交函数(REOF)方法,分析了西北干旱区地气温差的时空演变特征、气候突变和周期振荡。结果表明:西北干旱区地气温差可分为12月~2月、3月、4~6月、7~10月和11月5类,11月和12月~2月呈下降趋势,3月、4~6月和7~10月呈上升趋势,12月~2月下降幅度较大,4~6月上升幅度最大;地气温差受大尺度气候异常的影响,第一载荷向量反映了全区一致的性质;北疆区和内蒙区有异常变化存在;3月和11月的突变点为1977年,12月~2月、4~6月和7~10月的突变点为1981年;周期振荡主要以3~6年为主。 相似文献