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排序方式: 共有481条查询结果,搜索用时 171 毫秒
241.
242.
Remote Sensing of Mangrove Change Along the Tanzania Coast 总被引:1,自引:1,他引:0
Yeqiao Wang Gregory Bonynge Jarunee Nugranad Michael Traber Amani Ngusaru James Tobey 《Marine Geodesy》2013,36(1-2):35-48
This article contributes to the understanding of the changes in distribution and total area of mangrove forests along the mainland Tanzania coast over the past decade. Mangroves are recognized as critical coastal habitat requiring protection and special attention. The Tanzania coastline forms a suitable habitat for establishment of mangrove forests. Mangrove forests are distributed from Tanga in the north to Mtwara in the south covering approximately 109,593 hectares from 1988-1990 and about 108,138 hectares in 2000. The largest continuous mangrove stands are found in the districts of Rufiji, Kilwa, Tanga-Muheza, and Mtwara. Comparison of data between these two time periods shows that the geographic coverage of mangroves has no dramatic change in the past decade. The Tanzania Mangrove Management Project and other closely related programs and efforts pertaining to mangrove conservation contribute to direct restoration and natural regeneration of mangroves. This study documents the changes of mangroves and demonstrates that remote sensing and GIS offer important data and tools in the advancement of coastal resource management and ecosystem monitoring. Application of geographic information technologies is critical for improved coastal resources management and decision making for sustainable development in Tanzania. 相似文献
243.
《Norsk geografisk tidsskrift. Norwegian journal of geography》2012,66(1):21-31
In this study some light is shed on farmers' changing land-use and management practices in two mountain watersheds located in the Western Hills of Nepal. The study is based on a survey of 300 households, group discussion, interviews of key informants, and field observation in project and non-project watersheds conducted from April to September 1999. Confronted with shrinking landholding size, owing to a steadily growing population and scarcity of non-farming employment opportunities, farmers in both watersheds have gradually intensified land use and cultivated new crops to increase farm production and income. They are shifting from cereal crops to livestock husbandry, particularly along the road in the project watershed, and to vegetables and other cash crops in the accessible foothills of the non-project watershed. They have also adopted various structural and biological measures to control soil erosion, landslides, gully expansion and soil nutrient loss in order to maintain or enhance land productivity. The degree of adoption of the structural and biological measures is higher in the project watershed than in the non-project watershed. Contrary to the traditionally held belief of some researchers, population pressure on a finite land resource has brought about positive changes in land-use and management practices. Farmers have innovated and adopted different land management technologies to increase farm production as they are exposed to the risk of food insecurity because of shrinking landholding size and land degradation. 相似文献
244.
利用1960-2008年山西省65个气象站的气温资料,采用线性倾向估计、滑动平均法、小波分析和突变分析等方法,分析了近49a来山西省气温变化的特点和规律。结果表明:山西省年及四季气温均呈上升趋势,气温倾向率分别为0.25℃/10a、0.31℃/10a、0.04℃/10a、0.19℃/10a和0.43℃/10a。山西省年平均气温与秋季气温存在准15a及5-10a的周期,春、夏两季气温主要以5-10a的周期变化为主,冬季气温主要存在准15a的周期。山西省年平均气温以及春、冬两季气温均发生了突变,突变开始时间为1993、1997年和1988年。 相似文献
245.
近57年巴彦淖尔市平均最高最低气温及日较差变化 总被引:1,自引:0,他引:1
利用1954年-2010年内蒙古巴彦淖尔市9个台站的月平均最高、最低气温观测资料,对巴彦淖尔市年、季平均最高、最低气温变化趋势的空间分布状况和时间变化特征进行了分析。结果表明,近57年来,巴彦淖尔市年平均最高气温的变化特征呈现北部增暖幅度明显大于南部,且近十年呈弱降温趋势;年平均最低气温与全国各地基本一致,呈明显的变暖趋势;无论是年还是季,平均最低气温的增暖幅度明显大于平均最高气温的增幅;年平均日较差多呈下降趋势,并在北部地区尤为明显,各季平均日较差亦均呈下降趋势,并以冬季的下降幅度为最大;年平均最高气温和最低气温的变化在年代际变化上基本呈现较为一致的变化,即57年来主要的变暖均是从20世纪80年代中期开始,均在90年代后期达到了近57年来的历史新高,最高气温近十年来又略有回落。 相似文献
246.
247.
Brett J. Stubbs 《The Australian geographer》2001,32(3):295-319
A feature of the pre-European landscape of the sub-tropical Richmond River district of north-eastern New South Wales was a large expanse of rainforest known as the Big Scrub. In and around the Big Scrub were small patches of grassland and grassy open-forest, known locally as 'grasses'. These were often given individual names, which indicated their importance in the early timber-based economy of this generally grassless district for camping and depasturing working stock. Historical records enable a reconstruction of the distribution of 56 named 'grasses', and also allow some inferences to be made about their botany and ecology. The 'grasses' appear to be natural features of the landscape, mainly relict areas following invasion of the late Pleistocene open-forest vegetation by rainforest, following sea level rise, during the Holocene. A toponymic study of the use of the term 'grass' in the Richmond River district is also included. 相似文献
248.
陈满荣 《云南地理环境研究》1996,8(2):81-85
本文针对生物在湖泊中的繁衍是湖泊消亡的主要原因这一观点,用现代地理学和历史地理学的理论和事实,否定了这一论点,指出湖泊消亡主要原因在不同时空等条件下的复杂性。对认识湖泊消亡规律有一定意义。 相似文献
249.
利用本站的历史演变资料 ,分析和临近站同期值的对比发现 ,白银观测站的日照从 1995年后发生了明显的变化。冬、春季日偏少最大 0 .8h ,夏、秋日偏少最大 0 .7h ,月日照百分率偏少 5~ 6个百分点 ;通过分析 ,提出了环境变化后日照后记的订正使用方法 相似文献
250.
Rural Tourism: A case of lifestyle-led opportunities 总被引:1,自引:0,他引:1
D. J. WALMSLEY 《The Australian geographer》2003,34(1):61-72
Tourism is often seen as a panacea for the ills of declining rural communities. The paper argues that there is an element of blind optimism in this view although a shift of focus from production to consumption within advanced economies like Australia's will undoubtedly provide opportunities for the development of the leisure, recreation and tourism industries, both in metropolitan and rural areas. The paper suggests that an increased focus on lifestyle will come to characterise Australia. Some rural communities will be able to capitalise on this, both for temporary visitors and for in-migration, but many will not. The well-established concepts of threshold and range, when coupled with the idea of specialisation, will have a large influence on which places 'win' and which 'lose' in any lifestyle-led and leisure-oriented society. 'Place marketing' will become increasingly important for towns competing against each other for the 'leisure and lifestyle dollar'. 相似文献