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141.
Shoreline armoring is extensive in urban areas worldwide, but the ecological consequences are poorly documented. We mapped
shoreline armoring along the Duwamish River estuary (Washington State, USA) and evaluated differences in temperature, invertebrates,
and juvenile salmon (Oncorhynchus spp.) diet between armored and unarmored intertidal habitats. Mean substrate temperatures were significantly warmer at armored
sites, but water temperature similar to unarmored habitats. Epibenthic invertebrate densities were over tenfold greater on
unarmored shorelines and taxa richness double that of armored locations. Taxa richness of neuston invertebrates was also higher
at unarmored sites, but abundance similar. We did not detect differences in Chinook (O. tshawytscha) diet, but observed a higher proportion of benthic prey for chum (O. keta) from unarmored sites. Given that over 66% of the Duwamish shoreline is armored—similar to much of south and central Puget
Sound—our results underscore the need for further ecological study to address the impacts of estuary armoring. 相似文献
142.
Leesun Kim Ian E. Galbally Nichola Porter Ian A Weeks Sarah J Lawson 《Journal of Atmospheric Chemistry》2011,68(3):265-279
Emissions of biogenic volatile organic compounds (BVOCs) from mechanical wounding of leaves and branches of plants can contribute
to the atmospheric burden of volatile organic compounds (VOCs) in both (a) urban airsheds (from urban garden maintenance)
and (b) the global atmosphere (from large scale forest harvesting). These emissions of BVOCs are poorly understood and quantified,
and their role in urban and global emissions inventories neglected. This paper presents measurements of the magnitude, duration
and composition of emissions of BVOCs, carbon dioxide (CO2) and methane (CH4) from freshly cut leaf mulch and wood chips derived from a common eucalypt tree, Eucalyptus sideroxylon (red ironbark), found in southeastern Australian forests and gardens. The emissions of BVOCs from freshly cut and shredded
leaves and wood of E. sideroxylon were found to be 2.3 ± 0.6 and 0.05 ± 0.04 mg g-1 DM (Dry Mass) from leaf mulch and wood chips respectively and to last typically for 1 day following cutting. Three sampling
techniques were used for VOC speciation and the 12 most abundant BVOCs released from the mulch materials were identified.
The specific BVOCs emitted in order of decreasing abundance from leaf mulch are: (a) stored plant oils, 1,8-cineole, α–pinene
and o-cymene which make up the major part of the emissions, (b) a minor contribution from chemicals associated with environmental
stress and wound defence, (Z)–3–hexenyl acetate, (E)-2-hexenal and (Z)-3-hexen-1-ol, and (c) a second minor contribution from
metabolic products, acetaldehyde and acetone. The observed integrated emissions of BVOCs from leaves following mulching are
equivalent to more than half and perhaps all of the likely stored plant oils in the leaves. For the two comparable studies
available, one of a plant with stored oils (this study) and one of a plant without stored plant oils, the emissions of leaf
wound defence BVOCs are in the same range for both plants. In the plant with stored plant oils, the plant oil emissions are
about a factor of 11 larger in emission rate than the plant wound defence BVOCs. A compilation of available leaf wounding
BVOC emission studies indicates that for plants with stored plant oils, plant oil emissions dominate, whereas with other plants,
leaf wound defence BVOCs dominate the emissions. 相似文献
143.
Stratospheric circulation in seasonal forecasting models: implications for seasonal prediction 总被引:1,自引:1,他引:0
Amanda C. Maycock Sarah P. E. Keeley Andrew J. Charlton-Perez Francisco J. Doblas-Reyes 《Climate Dynamics》2011,36(1-2):309-321
Accurate seasonal forecasts rely on the presence of low frequency, predictable signals in the climate system which have a sufficiently well understood and significant impact on the atmospheric circulation. In the Northern European region, signals associated with seasonal scale variability such as ENSO, North Atlantic SST anomalies and the North Atlantic Oscillation have not yet proven sufficient to enable satisfactorily skilful dynamical seasonal forecasts. The winter-time circulations of the stratosphere and troposphere are highly coupled. It is therefore possible that additional seasonal forecasting skill may be gained by including a realistic stratosphere in models. In this study we assess the ability of five seasonal forecasting models to simulate the Northern Hemisphere extra-tropical winter-time stratospheric circulation. Our results show that all of the models have a polar night jet which is too weak and displaced southward compared to re-analysis data. It is shown that the models underestimate the number, magnitude and duration of periods of anomalous stratospheric circulation. Despite the poor representation of the general circulation of the stratosphere, the results indicate that there may be a detectable tropospheric response following anomalous circulation events in the stratosphere. However, the models fail to exhibit any predictability in their forecasts. These results highlight some of the deficiencies of current seasonal forecasting models with a poorly resolved stratosphere. The combination of these results with other recent studies which show a tropospheric response to stratospheric variability, demonstrates a real prospect for improving the skill of seasonal forecasts. 相似文献
144.
145.
Sarah E. Gasda 《Advances in water resources》2011,34(10):1268-1282
Split-operator methods are commonly used to approximate environmental models. These methods facilitate the tailoring of different approximation approaches to different portions of the differential operator and provide a means to split large coupled problems into pieces that are more amenable to parallel computation than the original fully-coupled problem. However, split-operator methods introduce an additional source of approximation error into the solution, which is typically either ignored or controlled heuristically. In this work, we develop two methods to estimate and control the error in split-operator methods, which lead to a dynamic adjustment of the temporal splitting step based upon the error estimators. The proposed methods are shown to yield robust solutions that provide the desired control of error. In addition, for a typical nonlinear reaction problem, the new methods are shown to reduce the solution error by more than two orders of magnitude compared to standard methods for an identical level of computational effort. The algorithms introduced and evaluated have widespread applicability in environmental modeling. 相似文献
146.
A new tool called ESASS (Enhanced Screen Auger Sampling System) was developed by the U.S. Geological Survey. The use of ESASS, because of its unique U.S. patent design (U.S. patent no. 7,631,705 B1), allows for the collection of representative, depth‐specific groundwater samples (vertical profiling) in a quick and efficient manner using a 0.305‐m long screen auger during hollow‐stem auger drilling. With ESASS, the water column in the flights above the screen auger is separated from the water in the screen auger by a specially designed removable plug and collar. The tool fits inside an auger of standard inner diameter (82.55 mm). The novel design of the system constituted by the plug, collar, and A‐rod allows the plug to be retrieved using conventional drilling A‐rods. After retrieval, standard‐diameter (50.8 mm) observation wells can be installed within the hollow‐stem augers. Testing of ESASS was conducted at one waste‐disposal site with tetrachloroethylene (PCE) contamination and at two reference sites with no known waste‐disposal history. All three sites have similar geology and are underlain by glacial, stratified‐drift deposits. For the applications tested, ESASS proved to be a useful tool in vertical profiling of groundwater quality. At the waste site, PCE concentrations measured with ESASS profiling at several depths were comparable (relative percent difference <25%) to PCE concentrations sampled from wells. Vertical profiling with ESASS at the reference sites illustrated the vertical resolution achievable in the profile system; shallow groundwater quality varied by a factor of five in concentration of some constituents (nitrate and nitrite) over short (0.61 m) distances. 相似文献
147.
Numerical flow models can be a useful tool for dimensioning water wells and to investigate the hydraulics in their near‐field. Fully laminar flow can be assumed for all models calculated up to the screen. Therefore models can be used to predict—at least qualitatively, neglecting turbulent losses inside the well—the spatial distribution of inflow into the well and the overall hydraulic performance of different combinations of aquifer parameters and technical installations. Models for both horizontal (plan view) and vertical flow (cross section) to wells were calculated for a variety of setups. For the latter, this included variations of hydraulic conductivity of the screen, pump position, and aquifer heterogeneity. Models of suction flow control devices showed that they indeed can homogenize inflow, albeit at the cost of elevated entrance losses. 相似文献
148.
149.
Sarah Marie Hall 《Geoforum》2011,42(6):627-637
Using ethnographic research with six families in the North West of England (2007–2009), this paper opens up the ‘black box’ of everyday ethical consumption by adding colour and form to these everyday experiences. While recent geographical literature has recognised the ethical considerations that are implicit in everyday consumption practices, there is a noticeable void of research that explores and fleshes out the everyday ethical actions of individuals and families as consumers. By exploring the everyday ethics of money, waste and health choices in family consumption practices, this paper makes the case for recognising the ethical nature of everyday practices and choices of consumption. It is argued that rather than consumers subscribing to a given set of ethics in consumption, there are multiple ways of recognising consumption as an ethically-embedded process. 相似文献
150.
Blogging, social networking, and other Web 2.0 practices have sparked widespread debate about the status and future of privacy. This paper examines an explicitly geographical aspect of Web 2.0 with respect to these debates: the geospatial web, or ‘geoweb’. As part of fundamental shifts in the kinds of geographic information available, its circulation, and representative forms it assumes, the geoweb implies new objects of privacy concern and subsequent privacy-related negotiations over the aggregate of its component information, technologies, and data praxes. Thus we argue that privacy must not only be revisited, but indeed re-conceptualized. Whereas prior research on privacy vis-à-vis geographic information technologies has tended to question what privacy ‘is’, we focus instead on the constitutive outcomes of societal struggles over privacy. We examine how privacy is being negotiated around two geoweb services - Google Street View and the Twitter GeoAPI - to illustrate that these contestations produce privacy as a social object in particular ways. We show that public discourse around actual or anticipated privacy harms stemming from geoweb services and their uses, as well as the preventatives and remedies proposed or implemented to address such harms, reconstitute the objects and practices of privacy concern, and alter the roles and relationships of state, civil and corporate actors in the construction of privacy. Finally we suggest that the geoweb raises new privacy concerns because some of its representational forms - namely geo-tagged images and self-authored texts - facilitate identification and disclosure with more immediacy and less abstraction. 相似文献