全文获取类型
收费全文 | 88篇 |
免费 | 4篇 |
专业分类
测绘学 | 3篇 |
大气科学 | 7篇 |
地球物理 | 15篇 |
地质学 | 41篇 |
海洋学 | 6篇 |
天文学 | 8篇 |
自然地理 | 12篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 6篇 |
2020年 | 3篇 |
2019年 | 5篇 |
2018年 | 5篇 |
2017年 | 3篇 |
2016年 | 1篇 |
2015年 | 3篇 |
2014年 | 6篇 |
2013年 | 5篇 |
2012年 | 4篇 |
2011年 | 7篇 |
2010年 | 2篇 |
2009年 | 1篇 |
2008年 | 3篇 |
2007年 | 2篇 |
2006年 | 1篇 |
2004年 | 3篇 |
2003年 | 2篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1991年 | 2篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1970年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有92条查询结果,搜索用时 46 毫秒
1.
2.
Courtney Turich 《Geochimica et cosmochimica acta》2008,72(13):3287-3288
3.
A comparison of three image-object methods for the multiscale analysis of landscape structure 总被引:4,自引:0,他引:4
Geoffrey J. Hay Thomas Blaschke Danielle J. Marceau Andr Bouchard 《ISPRS Journal of Photogrammetry and Remote Sensing》2003,57(5-6):327
Within the conceptual framework of Complex Systems, we discuss the importance and challenges in extracting and linking multiscale objects from high-resolution remote sensing imagery to improve the monitoring, modeling and management of complex landscapes. In particular, we emphasize that remote sensing data are a particular case of the modifiable areal unit problem (MAUP) and describe how image-objects provide a way to reduce this problem. We then hypothesize that multiscale analysis should be guided by the intrinsic scale of the dominant landscape objects composing a scene and describe three different multiscale image-processing techniques with the potential to achieve this. Each of these techniques, i.e., Fractal Net Evolution Approach (FNEA), Linear Scale-Space and Blob-Feature Detection (SS), and Multiscale Object-Specific Analysis (MOSA), facilitates the multiscale pattern analysis, exploration and hierarchical linking of image-objects based on methods that derive spatially explicit multiscale contextual information from a single resolution of remote sensing imagery. We then outline the weaknesses and strengths of each technique and provide strategies for their improvement. 相似文献
4.
The Mau Forest Complex is Kenya's largest fragment of Afromontane forest, providing critical ecosystem services, and has been subject to intense land use changes since colonial times. It forms the upper catchment of rivers that drain into major drainage networks, thus supporting the livelihoods of millions of Kenyans and providing important wildlife areas. We present the results of a sedimentological and palynological analysis of a Late Pleistocene–Holocene sediment record of Afromontane forest change from Nyabuiyabui wetland in the Eastern Mau Forest, a highland region that has received limited geological characterization and palaeoecological study. Sedimentology, pollen, charcoal, X-ray fluorescence and radiocarbon data record environmental and ecosystem change over the last ~16 000 cal a bp. The pollen record suggests Afromontane forests characterized the end of the Late Pleistocene to the Holocene with dominant taxa changing from Apodytes, Celtis, Dracaena, Hagenia and Podocarpus to Cordia, Croton, Ficus, Juniperus and Olea. The Late Holocene is characterized by a more open Afromontane forest with increased grass and herbaceous cover. Continuous Poaceae, Cyperaceae and Juncaceae vegetation currently cover the wetland and the water level has been decreasing over the recent past. Intensive agroforestry since the 1920s has reduced Afromontane forest cover as introduced taxa have increased (Pinus, Cupressus and Eucalyptus). 相似文献
5.
6.
7.
In the Alaska halibut individual fishing quota (IFQ) fishery, small remote fishing communities (SRFCs) have disproportionately lost fishing rights. Our analysis of quota market participation from 1995 to 1999 confirms that SRFC residents are more likely to sell than buy quota. Alaska Native heritage is another important predictor of quota market behavior. Residents of Alaska Native villages have an increased likelihood of selling quota. Loss of fisheries participation in small indigenous communities can be an unintended consequence of quota systems. Mitigation measures should take into account the social factors that can lead to such a redistribution of fishing rights in privatized access fisheries. 相似文献
8.
The potential role of roots and rhizomes in structuring salt-marsh benthic communities 总被引:1,自引:0,他引:1
The density of the Carolina marsh clam,Polymesoda caroliniana (Bosc), was determined in three adjacent tidal marsh communities which differed only in plant species composition. Clam density was inversely related to the density (biomass) of plant roots and rhizomes in sediments and directly related to density of plant stems (numbers). Clam abundance was not related to the basal area of plant stems. Each plant community contained clams of various ages from juvenile to adult indicating continued recruitment and survival. These data suggest thatP. caroliniana is most abundant inJuncus roemerianus marshes because there are fewer roots and rhizomes (mean of 2.5 kg m?2) to hamper burrwing as compared toSpartina alterniflora andcynosuroides (5.1 and 6.3 kg m?2, respectively) dominated marshes. Salinity, floding frequency, distance from flooding water, and sediment type were essentially constant among the three plant communities. Root/rhizome density should be collected along with other environmental parameters during studies of benthic organisms on marshes because it potentially limits the occurrence or abundance of some species. 相似文献
9.
10.
Belowground production of roots and rhizomes in the top 20 cm of soil was 2.2 kg m?2 yr?1 based on a maximum minus minimum estimation procedure in a giant cordgrass (Spartina cynosuroides (L.) Roth) marsh in Mississippi. Approximately 1.9 kg m?2 (86%) of this production occurred in late spring-summer and 0.3 kg m?2 in late fall. This estimate ignores any production below 20 cm depth and is thus an underestimate. Production values increased to 4.0 kg m?2 yr?1 using Smalley’s technique and accounting for decomposition. Aboveground tissues (leaves and stems) were depleted in nitrogen in July which corresponded to peaks in both above- and belowground biomass. The low root/shoot ratio (2.6) on this marsh does not suggest that growth is nutrient limited. Indeed, total productivity (above- and belowground) for this marsh was high (between 4.4 and 6.2 kg m?2 yr?1). 相似文献