全文获取类型
收费全文 | 2104篇 |
免费 | 219篇 |
国内免费 | 241篇 |
专业分类
测绘学 | 74篇 |
大气科学 | 367篇 |
地球物理 | 250篇 |
地质学 | 531篇 |
海洋学 | 198篇 |
天文学 | 4篇 |
综合类 | 155篇 |
自然地理 | 985篇 |
出版年
2024年 | 8篇 |
2023年 | 25篇 |
2022年 | 48篇 |
2021年 | 77篇 |
2020年 | 57篇 |
2019年 | 59篇 |
2018年 | 64篇 |
2017年 | 83篇 |
2016年 | 85篇 |
2015年 | 74篇 |
2014年 | 98篇 |
2013年 | 90篇 |
2012年 | 99篇 |
2011年 | 103篇 |
2010年 | 80篇 |
2009年 | 100篇 |
2008年 | 114篇 |
2007年 | 133篇 |
2006年 | 123篇 |
2005年 | 109篇 |
2004年 | 84篇 |
2003年 | 87篇 |
2002年 | 94篇 |
2001年 | 105篇 |
2000年 | 93篇 |
1999年 | 88篇 |
1998年 | 79篇 |
1997年 | 58篇 |
1996年 | 41篇 |
1995年 | 46篇 |
1994年 | 37篇 |
1993年 | 25篇 |
1992年 | 17篇 |
1991年 | 14篇 |
1990年 | 16篇 |
1989年 | 13篇 |
1988年 | 10篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1978年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有2564条查询结果,搜索用时 15 毫秒
941.
逐小时自动站数据对于气象灾害预警、决策服务及预报预测等十分重要。以国家级自动站小时观测气温数据为基础,分析研究了小时气温数据的疑误形式,针对各种疑误数据,利用国家级台站建站以来的日最高、日最低以及4时次(北京时02点、08点、14点、20点)定时观测气温数据,研制形成了适用于中国自动站(区域站和国家站)逐小时气温数据质量控制系统,并将此系统应用到2006-2010年中国27000多自动站小时气温观测数据中。结果表明:区域站的正确率、可疑率、错误率分别为99.43 %、2.24 ‰和3.45 ‰,国家站则分别为99.82 %、1.27 ‰和0.49 ‰;区域站和国家站数据的可疑率相当,但国家站错误率明显比区域站低一个量级。通过历史数据质量控制结果的分析,证明自动站气温质量控制系统设计合理,可以判断出错误和可疑数据,具有可用性。 相似文献
942.
Institutional ambiguity in implementing the European Union Marine Strategy Framework Directive 总被引:1,自引:0,他引:1
This article addresses the institutional ambiguity that exists between the European, Regional and Member State levels in the implementation of the Marine Strategy Framework Directive (MSFD). The two main reasons for the emergence of institutional ambiguity are (1) the MSFD being a framework directive and (2) Member States are required to coordinate the implementation of the MFSD through the Regional Sea Conventions. Institutional ambiguity refers to the interference zone between different institutional settings that come together in new policy practices. New rules of the game are needed to bring these institutional settings together and the room to manoeuvre for the actors who negotiate these rules is a defining feature of institutional ambiguity. This article analyses the institutional ambiguity associated with MSFD implementation on the European and regional level for four European Seas: the North Sea, the Baltic Sea, the Mediterranean Sea and the Black Sea. The results indicate different levels of institutional ambiguity in each of the four regions, with the lowest level of ambiguity in the Baltic Sea and the highest in the Mediterranean Sea. Institutional ambiguity also exists on the European level, as coordination efforts have not resulted in clear directions for the implementation of the MSFD as yet. The level of institutional ambiguity is influenced by the relative number of EU member states bordering the particular sea and whether they consider implementation of the MFSD to be urgent. Member States bordering the Mediterranean and the Black Seas lack the support of Regional Sea Conventions in addition to receiving limited direction from the European level. 相似文献
943.
甘肃省各地区自然、社会、经济、文化、人口差异很大,影响经济发展和人口分布的因素也各不相同,为了分析清楚甘肃省经济发展与人口空间分布的现状,本文采用2004年最新统计数据对甘肃省经济不均衡性与人口分布的相关关系进行分析。首先通过计算基尼系数和地理联系率,分析比较了甘肃省主要经济部门与人口空间分布的集中与分散程度,然后通过计算地区综合经济指数、文化水平综合均值,分析甘肃省综合经济水平与人口发展的相关关系,从经济部门的内部组成与外部综合经济实力两个方面分析了甘肃省经济与人口分布以及综合经济水平与综合人口素质的空间关系,为甘肃省经济合理布局和适度人口政策的制定提供了参考意见,为地区经济、人口协调可持续发展提供理论基础。 相似文献
944.
张振佳 《云南地理环境研究》2008,20(1):72-75
区域经济差异的研究历来是区域经济研究的主线。通过运用加权变异系数、锡尔系数和基尼系数等数学方法对泉州市县域经济进行研究,探讨了三次产业以及地区(沿海与内陆)内、地区间对泉州市县域经济发展差距的影响。得出如下结论:(1)泉州市县域经济发展总体差距缩小;(2)第三产业对泉州市县域经济发展差距的贡献率最大,第二产业次之,第一产业最小;(3)地区间的差距对总体差距的贡献呈先上升后下降,而地区内差距特别是沿海内部差距对泉州市县域经济发展差距的的贡献总体呈现上升趋势。 相似文献
945.
改革开放以来,内蒙古经济获得快速发展,取得可喜成就。但是.各地区的经济发展非常不平衡,地区经济差距显著。本文首先揭示了地区经济差距的现状,然后详细地分析各地区对外开放的差异及对地区经济的影响,并运用数学的回归分析法,进行了相关性分析,结果显示二者之间呈现密切的相关关系。 相似文献
946.
世界空港经济发展模式研究 总被引:6,自引:0,他引:6
随着经济全球化不断深入、竞争不断加剧,快速反应的物流形式——航空物流在国际货运中的地位不断提高,由航空物流派生出来的航空商务已成为新的经济增长点,发展航空经济已成为世界各国的热点。本文在界定空港经济定义的基础上,分析了产业对空港经济的适应性,总结了全球四种空港经济的产业发展模式,并在宏观层面上提出了空港经济的固层结构,在微观层面上剖析了两种不同的空港经济布局模式。 相似文献
947.
《Marine Georesources & Geotechnology》2013,31(3-4):261-267
The construction of bridges and tunnels plays an important role in the social and economic development of cities and local regions. The planning of the bridge and tunnel across Taiwan Straits will have a positive effect on the economic development at each stage: preplanning, engineering construction, and the completion of the project. The two sides of Taiwan Straits have the advantage of a suitable location, consanguineous relationship, and appropriate geographic conditions. Currently, there are many economic and cultural communications between both sides of the Straits. The bridge and tunnel from Xiamen to Jinmen can be regarded as the beginning of the “golden link belt.” The total capability for sustainable development of Fujian Province ranks the sixth among 31 provinces in China, which will provide powerful support for the construction of the bridge and tunnel. 相似文献
948.
《African Journal of Marine Science》2013,35(4):497-504
Populations of the African penguin Spheniscus demersus have decreased dramatically over the past century, due in part to competition for food with commercial fisheries, and the species is now endangered as a result. Economic arguments are used to favour fisheries over the needs of penguins, but penguins have direct value to the South African economy thanks to penguin-based tourism at several breeding colonies. We estimated the value of African penguins at the most important tourist site for African penguins: Boulders on the Cape Peninsula, South Africa. As a mainland colony close to Cape Town, Boulders is accessible to large numbers of visitors; gate revenues in 2009/2010 alone were R14.5 million (US$2 million). A zonal travel-cost analysis revealed an average consumer surplus among Cape Town residents of some R20 per visit. Penguin-based tourism thus forms an integral part of the R25 billion Western Cape tourism sector. Given that the future survival of this valuable resource is dependent, among others, on the availability of sufficient prey, competition with South Africa's purse-seine fishing fleet should be limited through management strategies that lessen the potential effects of fishing on prey available at the local scale. 相似文献
949.
Finding common ground: relational concepts of land tenure and economy in the oil palm frontier of Papua New Guinea 总被引:1,自引:0,他引:1
In the oil palm frontier regions of West New Britain and Oro provinces, Papua New Guinea, customary land tenure arrangements are changing in response to the growing demand for land for agricultural development. This paper examines one aspect of these changes, namely the gifting and selling of customary land for oil palm development to people who have no customary birthrights to the land. By analysing how access rights are maintained over the relatively long cultivation cycle of oil palm (approximately 25 years), and in the context of the rapidly changing socio-economic and demographic environments of the oil palm frontiers, the paper demonstrates that while land transactions seemingly entail the commodification of land, land rights and security of land tenure remain embedded in social relationships. For customary landowners, the moral basis of land rights is contingent on 'outsiders' maintaining particular kinds of social and economic relationships with their customary landowning 'hosts'. In exploring how these social relationships are constituted through the performance of particular kinds of exchange relationships, the paper provides insights into relational concepts of land rights and how these are able to persist in Papua New Guinea's oil palm frontier regions where resource struggles are often intense and where large migrant populations are seeking land for agricultural development. 相似文献
950.
Mehdi Saqalli Patrick Caron Pierre Defourny Ali Issaka 《Applied geography (Sevenoaks, England)》2009,29(3):358-370
This paper examines the relevance of a perception-based regional level mapping tool in rural Niger. Two regions in Niger are examined. Results permit to assume that such a tool helped to fill several gaps: (i) a scale gap between local and nation wide studies; (ii) a scientific gap between biophysical and socio-anthropological sciences; and (iii) a methodological gap of integration between data sources. Moreover, this method is fast, cheap and action-oriented. Data are easily understandable and usable both by rural communities and development agencies. It provides information about human dynamics at a regional level, which cannot be achieved by other methods. 相似文献