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71.
Remote sensing offers a potential tool for large scale environmental surveying and monitoring. However, remote observations of coral reefs are difficult especially due to the spatial and spectral complexity of the target compared to sensor specifications as well as the environmental implications of the water medium above. The development of sensors is driven by technological advances and the desired products. Currently, spaceborne systems are technologically limited to a choice between high spectral resolution and high spatial resolution, but not both. The current study explores the dilemma of whether future sensor design for marine monitoring should prioritise on improving their spatial or spectral resolution. To address this question, a spatially and spectrally resampled ground-level hyperspectral image was used to test two classification elements: (1) how the tradeoff between spatial and spectral resolutions affects classification; and (2) how a noise reduction by majority filter might improve classification accuracy. The studied reef, in the Gulf of Aqaba (Eilat), Israel, is heterogeneous and complex so the local substrate patches are generally finer than currently available imagery. Therefore, the tested spatial resolution was broadly divided into four scale categories from five millimeters to one meter. Spectral resolution resampling aimed to mimic currently available and forthcoming spaceborne sensors such as (1) Environmental Mapping and Analysis Program (EnMAP) that is characterized by 25 bands of 6.5 nm width; (2) VENμS with 12 narrow bands; and (3) the WorldView series with broadband multispectral resolution. Results suggest that spatial resolution should generally be prioritized for coral reef classification because the finer spatial scale tested (pixel size < 0.1 m) may compensate for some low spectral resolution drawbacks. In this regard, it is shown that the post-classification majority filtering substantially improves the accuracy of all pixel sizes up to the point where the kernel size reaches the average unit size (pixel < 0.25 m). However, careful investigation as to the effect of band distribution and choice could improve the sensor suitability for the marine environment task. This in mind, while the focus in this study was on the technologically limited spaceborne design, aerial sensors may presently provide an opportunity to implement the suggested setup. 相似文献
72.
Geomorphic considerations for erosion prediction 总被引:9,自引:0,他引:9
Current soil-erosion prediction technology addresses processes of rainsplash, overland-flow sediment transport, and rill
erosion in small watersheds. The effects of factors determining sediment yield from larger-scale drainage basins, in which
sediment movement is controlled by the combined small-scale processes and a complex set of channel and other basin-scale sediment-delivery
processes, such as soil creep, bioturbation, and accelerated erosion due to denudation of vegetation, have been poorly evaluated.
General suggestions are provided for the development of erosion-prediction technology at the geomorphic or drainage-basin
scale based on the separation of sediment-yield data for channel and geomorphic processes from those of field-scale soil loss.
An emerging technology must consider: (1) the effects on sediment yield of climate, geology and soils, topography, biotic
interactions with other soil processes, and land-use practices; (2) all processes of sediment delivery to a channel system;
and (3) the general tendency in most drainage basins for progressively greater sediment storage in the downstream direction.
Received: 8 November 1995 · Accepted: 20 November 1995 相似文献
73.
M. de Vries G. J. Klaassen N. Struiksma Professor Delft University of Technology. The Netherlands. Delft Hydraulics. The Netherlands. 《国际泥沙研究》1990,(1)
I. INTRODUCTIONMore than a decade ago, under tile auspices of DELFT HYDRAULICS an overview on the use ofmodels for river problems was given (de Vries & van der Zwaard. 1975). Since then a better understanding of morphological processes in rivers has been obtained, their mathematical formulation hasbeen improved and computer facilities have been expended. Scale models and mathematical models arein use. but their field of application is gradually changing. It seems that the better ma… 相似文献
74.
Burša Milan Raděj Karel Šima Zdislav True Scott A. Vatrt Viliam 《Studia Geophysica et Geodaetica》1997,41(3):203-216
The geopotential scale factor R
o
= GM/W
o
(the GM geocentric gravitational constant adopted) and/or geoidal potential Wo have been determined on the basis of the first year's (Oct 92 – Dec 93) ERS-1/TOPEX/POSEIDON altimeter data and of the POCM 4B sea surface topography model: R
o
°=(6 363 672.58°±0.05) m, W
o
°=(62 636 855.8°±0.05)m
2
s
–2
. The 2°–°3 cm uncertainty in the altimeter calibration limits the actual accuracy of the solution. Monitoring dW
o
/dt has been projected. 相似文献
75.
湿地价值评估尺度转换方法——Meta分析研究概述 总被引:3,自引:0,他引:3
湿地价值评估中的尺度转换是通过一个已经有的、与被估算生态系统相似的另一生态系统的价值来估算该湿地生态系统的价值量的过程。Meta分析(Meta-Analysis)是一种定量其他评价效应的大小,并进行综合分析评价的方法,是分析的分析,综合的综合,具有较高的统计效率及验证其他假设的功能,是一种较为精确的价值转移方法。阐述了Meta分析的定义,介绍了Meta分析的步骤及函数表达式,陈述了国内外学者对Meta分析的应用及研究进展,并对其未来的应用前景进行了展望。 相似文献
76.
Ultra fast marine vehicles can substantially benefit from aerodynamic unloading. The subject of this study is aerodynamics of a hybrid trimaran that comprises three wave-piercing planing hulls and a wing-shaped superstructure. This configuration is characterized by high efficiency and good seaworthiness at speeds about twice those of contemporary fast ferries and combat ships. Aerodynamic coefficients of the above-water structure of the hybrid trimaran were measured in a wind tunnel. A computer code based on the vortex lattice method is applied for modeling steady aerodynamics of this structure in a range of attack angles. The application of an interceptor at the pressure side of the wing is shown to produce significant increase in aerodynamic lift. 相似文献
77.
The present paper reviews research done in Asian countries during the second phase of the Worldwide Collaborative Research Project on Fisheries Co-management. Building on the results of the first phase, the paper focuses on stakeholder conflict, and social and geographical scale. Several conclusions emerge from common patterns. Community motivations for co-management are often related more to the protection of fisheries resources from outsiders than to conservation. Access rights are important but exclusion from food resources in a context of widespread poverty should be approached carefully. Cross-scale institutional linkages make adaptive management possible by bringing together groups with broad local foci and ones with narrow trans-local mandates. The role of the government is balancing interactions between these various groups. This is not a role that is compatible with top-down management. 相似文献
78.
79.
《The Journal of geography》2012,111(5):206-213
Abstract The concept of scale is fundamental to geography, yet the definitions for “scale” and related spatial terms can be confusing to those working in other spatial science disciplines. This is particularly true in the emerging multidisciplinary world of integrated remote sensing and geographic information systems, or IGIS's, where data of different types and at various spatial and temporal scales are combined to support complex space-time data analyses. Without a basic lexicon of accepted scale terms, working within an IGIS can breed confusion in the interpretation of data and the models that result from an IGIS construct. This paper provides some terminologies of scale that can be used as a framework for a multidisciplinary lexicon of accepted scaling terms and describes their relationships to an IGIS. It also illustrates how scaling terms can be potentially misunder stood when applied to geographic techniques that are used in disciplines related to geography. 相似文献
80.