全文获取类型
收费全文 | 2941篇 |
免费 | 195篇 |
国内免费 | 219篇 |
专业分类
测绘学 | 1569篇 |
大气科学 | 41篇 |
地球物理 | 198篇 |
地质学 | 791篇 |
海洋学 | 177篇 |
天文学 | 38篇 |
综合类 | 216篇 |
自然地理 | 325篇 |
出版年
2024年 | 2篇 |
2023年 | 14篇 |
2022年 | 82篇 |
2021年 | 83篇 |
2020年 | 129篇 |
2019年 | 92篇 |
2018年 | 62篇 |
2017年 | 211篇 |
2016年 | 174篇 |
2015年 | 142篇 |
2014年 | 163篇 |
2013年 | 275篇 |
2012年 | 202篇 |
2011年 | 184篇 |
2010年 | 126篇 |
2009年 | 101篇 |
2008年 | 182篇 |
2007年 | 164篇 |
2006年 | 141篇 |
2005年 | 122篇 |
2004年 | 94篇 |
2003年 | 89篇 |
2002年 | 76篇 |
2001年 | 68篇 |
2000年 | 48篇 |
1999年 | 41篇 |
1998年 | 54篇 |
1997年 | 37篇 |
1996年 | 26篇 |
1995年 | 25篇 |
1994年 | 16篇 |
1993年 | 18篇 |
1992年 | 13篇 |
1991年 | 12篇 |
1990年 | 18篇 |
1989年 | 8篇 |
1988年 | 8篇 |
1987年 | 9篇 |
1986年 | 10篇 |
1985年 | 8篇 |
1984年 | 4篇 |
1982年 | 3篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1973年 | 5篇 |
1972年 | 4篇 |
1971年 | 3篇 |
排序方式: 共有3355条查询结果,搜索用时 781 毫秒
972.
Amongst many ongoing initiatives to preserve biodiversity, the Millennium Ecosystem Assessment again shows the importance to slow down the loss of biological diversity. However, there is still a gap in the overview of global patterns of species distributions. This paper reviews how remote sensing has been used to assess terrestrial faunal diversity, with emphasis on proxies and methodologies, while exploring prospective challenges for the conservation and sustainable use of biodiversity. We grouped and discussed papers dealing with the faunal taxa mammals, birds, reptiles, amphibians, and invertebrates into five classes of surrogates of animal diversity: (1) habitat suitability, (2) photosynthetic productivity, (3) multi-temporal patterns, (4) structural properties of habitat, and (5) forage quality. It is concluded that the most promising approach for the assessment, monitoring, prediction, and conservation of faunal diversity appears to be the synergy of remote sensing products and auxiliary data with ecological biodiversity models, and a subsequent validation of the results using traditional observation techniques. 相似文献
973.
The availability of airborne LiDAR data provides a new opportunity to overcome some of the problems associated with traditional, field‐based, geomorphological mapping such as restrictions on access and constraints of time or cost. The combination of airborne LiDAR data and GIS technology facilitates the rapid production of geomorphological maps of floodplain environments; however, unfiltered LiDAR data, which include vegetation and buildings, are currently more suitable for geomorphological mapping than data that have been filtered to remove these features. Classification of LiDAR data according to elevation in a GIS enables the user to identify and delineate geomorphological features in a manner similar to field mapping, but it is necessary to use a range of classification intervals in order to map the various types of feature that occur within a single reach. Comparison of a LiDAR‐derived geomorphological map with an independently produced field geomorphological map showed a high degree of similarity between the results of the two methods, although ground‐truthing is essential in cases where a high degree of accuracy is required. Ground‐truthing of a LiDAR‐derived geomorphological map showed that around 80% of features mapped using both methods were identified from the LiDAR data, suggesting that the method is suitable for applications such as production of base maps for use in field mapping and selection of sites for detailed investigation. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
974.
975.
Eric M. Thompson Laurie G. Baise Robert E. Kayen 《Soil Dynamics and Earthquake Engineering》2007,27(2):144-152
Ground motions recorded within sedimentary basins are variable over short distances. One important cause of the variability is that local soil properties are variable at all scales. Regional hazard maps developed for predicting site effects are generally derived from maps of surficial geology; however, recent studies have shown that mapped geologic units do not correlate well with the average shear-wave velocity of the upper 30 m, Vs(30). We model the horizontal variability of near-surface soil shear-wave velocity in the San Francisco Bay Area to estimate values in unsampled locations in order to account for site effects in a continuous manner. Previous geostatistical studies of soil properties have shown horizontal correlations at the scale of meters to tens of meters while the vertical correlations are on the order of centimeters. In this paper we analyze shear-wave velocity data over regional distances and find that surface shear-wave velocity is correlated at horizontal distances up to 4 km based on data from seismic cone penetration tests and the spectral analysis of surface waves. We propose a method to map site effects by using geostatistical methods based on the shear-wave velocity correlation structure within a sedimentary basin. If used in conjunction with densely spaced shear-wave velocity profiles in regions of high seismic risk, geostatistical methods can produce reliable continuous maps of site effects. 相似文献
976.
M. Bisson M. T. Pareschi G. Zanchetta R. Sulpizio R. Santacroce 《Bulletin of Volcanology》2007,70(2):157-167
The Campania Region (southern Italy) is characterized by the frequent occurrence of volcaniclastic debris flows that damage
property and loss of life (more than 170 deaths between 1996 and 1999). Historical investigation allowed the identification
of more than 500 events during the last four centuries; in particular, more than half of these occurred in the last 100 years,
causing hundreds of deaths. The aim of this paper is to quantify debris-flow hazard potential in the Campania Region. To this
end, we compared several elements such as the thickness distribution of pyroclastic fall deposits from the last 18 ka of the
Vesuvius and Phlegrean Fields volcanoes, the slopes of relieves, and the historical record of volcaniclastic debris flows
from A.D. 1500 to the present. Results show that flow occurrence is not only a function of the cumulative thickness of past
pyroclastic fall deposits but also depends on the age of emplacement. Deposits younger than 10 ka (Holocene eruptions) apparently
increase the risk of debris flows, while those older than 10 ka (Late Pleistocene eruptions) seem to play a less prominent
role, which is probably due to different climatic conditions, and therefore different rates of erosion of pyroclastic falls
between the Holocene and the Late Pleistocene. Based on the above considerations, we compiled a large-scale debris-flow hazard
map of the study area in which five main hazard zones are identified: very low, low, moderate, high, and very high. 相似文献
977.
基于语义映射的空间数据转换及其应用研究 总被引:3,自引:0,他引:3
数据转换是GIS工程建设中的一个十分重要的内容,传统的方法往往只是进行数据格式的转换,忽略了空间数据之间的内在联系,本文将语义映射和空间操作相结合,实现空间数据和属性数据的重构,从而实现异构数据的快速转换。 相似文献
978.
979.
980.
网络办公系统在测绘生产中的应用开发 总被引:1,自引:0,他引:1
结合工作实际介绍了网络办公系统建设的意义、过程及在测绘生产中的应用,根据系统开发过程中所遇到的问题,总结了网络办公系统建立的一些关键技术及测绘工作中对网络办公系统的需求,为行业中其他正在建设或拟定建设的办公系统提供借鉴。 相似文献