全文获取类型
收费全文 | 777篇 |
免费 | 44篇 |
国内免费 | 65篇 |
专业分类
测绘学 | 227篇 |
大气科学 | 29篇 |
地球物理 | 87篇 |
地质学 | 125篇 |
海洋学 | 102篇 |
天文学 | 12篇 |
综合类 | 81篇 |
自然地理 | 223篇 |
出版年
2023年 | 8篇 |
2022年 | 19篇 |
2021年 | 19篇 |
2020年 | 25篇 |
2019年 | 32篇 |
2018年 | 20篇 |
2017年 | 31篇 |
2016年 | 35篇 |
2015年 | 22篇 |
2014年 | 37篇 |
2013年 | 90篇 |
2012年 | 35篇 |
2011年 | 70篇 |
2010年 | 34篇 |
2009年 | 35篇 |
2008年 | 38篇 |
2007年 | 43篇 |
2006年 | 35篇 |
2005年 | 40篇 |
2004年 | 38篇 |
2003年 | 24篇 |
2002年 | 26篇 |
2001年 | 17篇 |
2000年 | 28篇 |
1999年 | 16篇 |
1998年 | 9篇 |
1997年 | 17篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1994年 | 8篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 1篇 |
排序方式: 共有886条查询结果,搜索用时 515 毫秒
621.
Javier Lacasta F. Javier Lopez-Pellicer Borja Espejo-García Javier Nogueras-Iso F. Javier Zarazaga-Soria 《International journal of geographical information science》2017,31(8):1583-1605
Geospatial data catalogs enable users to discover and access geographical information. Prevailing solutions are document oriented and fragment the spatial continuum of the geospatial data into independent and disconnected resources described through metadata. Due to this, the complete answer for a query may be scattered across multiple resources, making its discovery and access more difficult. This paper proposes an improved information retrieval process for geospatial data catalogs that aggregates the search results by identifying the implicit spatial/thematic relations between the metadata records of the resources. These aggregations are constructed in such a way that they match better the user query than each resource individually. 相似文献
622.
Based on the concept of map algebra, this research developed a network neighborhood analysis framework for directed flow networks. The analysis framework has two components: the first component defines how neighborhoods are delineated on networks and the second component calculates various statistics within the neighborhoods. The power and value of the analysis framework lie in its capability to delineate versatile network neighborhoods and its flexibility in calculating various statistics within the neighborhoods. It extends the raster map algebra to networks and provides a consistent analysis framework for the raster, vector, and network data models. Using a small section of the National Hydrography Dataset (NHD) networks, a prototype Web application is implemented to experiment and demonstrate the concept and uses of the analysis framework. 相似文献
623.
The benefits of a regional or thematic approach to the study and presentation of world geography have long been debated. The goal to not to reimagine these debates or to promote one approach over another; the aim is to explore how world geography courses are currently being taught in American universities. By polling and sharing information about course structures, topics, and forms of evaluation, an open dialogue between instructors that will improve teaching strategies and student comprehension is encouraged. 相似文献
624.
Takeshi Shirabe 《International journal of geographical information science》2016,30(8):1469-1485
Given a grid of cells each having an associated cost value, a raster version of the least-cost path problem seeks a sequence of cells connecting two specified cells such that its total accumulated cost is minimized. Identifying least-cost paths is one of the most basic functions of raster-based geographic information systems. Existing algorithms are useful if the path width is assumed to be zero or negligible compared to the cell size. This assumption, however, may not be valid in many real-world applications ranging from wildlife corridor planning to highway alignment. This paper presents a method to solve a raster-based least-cost path problem whose solution is a path having a specified width in terms of Euclidean distance (rather than by number of cells). Assuming that all cell values are positive, it does so by transforming the given grid into a graph such that each node represents a neighborhood of a certain form determined by the specified path width, and each arc represents a possible transition from one neighborhood to another. An existing shortest path algorithm is then applied to the graph. This method is highly efficient, as the number of nodes in the transformed graph is not more than the number of cells in the given grid and decreases with the specified path width. However, a shortcoming of this method is the possibility of generating a self-intersecting path which occurs only when the given grid has an extremely skewed distribution of cost values. 相似文献
625.
在世界遗产地旅游产业发展的动态背景下,运用偏离份额分析法和向量夹角法分别从产业结构的合理化和高级化两个视角衡量山东省曲阜市2006—2015年旅游产业结构的时序变化,测度曲阜市旅游产业结构变动对旅游经济发展的贡献。研究表明:曲阜市旅游产业有一定的结构优势但竞争力相对较弱,合理化水平有待提高;旅游产业结构的高级化水平虽然有升有降,但平均水平一直较高,表现出高位震荡的特征;旅游产业结构变动对旅游经济增长贡献度的均值为0.03,周期性震荡呈现收敛趋势,反映出曲阜市旅游经济发展趋于成熟。 相似文献
626.
国际环境复杂多变,世界经济处于金融危机后的深度调整期,世情、国情、党情步入新常态,迫切需要开展地理世情监测,实施服务经济发展、国防安全、外交商贸、资源开发、能源保障等"走出去"战略。本文分析了地理世情监测的内涵、意义、国内外发展现状、我国开展地理世情监测的已有基础和存在的问题,提出开展常态化地理世情监测的若干建议。 相似文献
627.
地图符号设计是地图设计的重要组成部分,其中,用于表示不依比例尺小面积地物或点状地物的点状符号设计被广泛关注和探讨。综观目前常见的网络地图,特别是旅游网络地图,其点状地图符号设计方案大多尺寸相近,以象形符号为主,但边框设计有3种不同方案:对符号添加统一边框,对不同符号添加不同边框,以及不加边框。通过眼动实验,探究点状地图符号边框设计对用户认知地图的影响,比较上述3种方案所获取的不同认知效果,进一步研究网络旅游地图的点状地图符号边框设计方案。 相似文献
628.
Victor R. Savage 《Singapore journal of tropical geography》2003,24(1):61-85
To celebrate the 50th anniversary of the Singapore Journal of Tropical Geography and the 75th anniversary of the teaching of geography in the Department of Geography, National University of Singapore, the home of the Journal, this article, based on personal reflections and "objective" academic materials, provides an overview of developments in geography in the Department and Journal. The paper argues that the department's and Journal's"identities", since the post-World War II period, have been shaped by Singapore's changing domestic politics, the changing university academic environment, the personalities and academic interests of heads of the department and the Journa's editors, the state of the changing regional and global political economic environment, and the individual research interests of faculty in the department, and reflects a complex mix of colonial/post-colonial, modern/post-modern, North-South and East-West discourses. While a defined Singapore school of geography has yet to emerge, the article shows that both the department and the Journal have made major strides in meeting the challenges of globalisation and, in the process, have gained international visibility and academic legitimacy. In particular, the Journal has consolidated its position as a major voice for academics in lesser developed countries, its platform for "tropical world" discourse and maintaining its edge in the colonial/post-colonial and modern/post-modern discourses of states within the tropics. 相似文献
629.
630.
简述宽波段或高光谱遥感技术方法及亚象元、低概率目标探测技术的研究及应用现状。结合大兴安岭地区矿产资源勘查的背景条件,系统阐述该技术在植被覆盖地区地质找矿的应用流程。这一研究方案的实施及可能获得的成果,将改善在植被覆盖地区的地质找矿工作。 相似文献