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241.
ABSTRACT

Environmental change in small islands may be associated with migration as a means of adaptation. Both Manam and the Carteret Islands in Papua New Guinea (PNG) have experienced rapid- and slow-onset changes, respectively. These have been accompanied by the forced migration and ‘temporary’ resettlement of the Manam population and attempts at resettlement by Carteret Islanders. Neither has proved successful, thwarted by ‘host’ landowners, the impossibility of gaining adequate access to land and land rights, and government inactivity. Settlers have been perceived as outsiders and rival claimants to valuable coastal resources. Inability to resettle in national contexts raises issues of ambiguity, identity and citizenship. The problems experienced by quite small population groups moving short distances in similar cultural contexts are indicative of the potential future problems facing environmental migrants in other contexts.  相似文献   
242.
We document frequent, rapid, strong, millennial-scale paleovegetation shifts throughout the late Pleistocene, within a 100,000+ yr interval (~ 115–15 ka) of terrestrial sediments from the mid-Atlantic Region (MAR) of North America. High-resolution analyses of fossil pollen from one core locality revealed a continuously shifting sequence of thermally dependent forest assemblages, ranging between two endmembers: subtropical oak-tupelo-bald cypress-gum forest and high boreal spruce-pine forest. Sedimentary textural evidence indicates fluvial, paludal, and loess deposition, and paleosol formation, representing sequential freshwater to subaerial environments in which this record was deposited. Its total age–depth model, based on radiocarbon and optically stimulated luminescence ages, ranges from terrestrial oxygen isotope stages (OIS) 6 to 1. The particular core sub-interval presented here is correlative in trend and timing to that portion of the oxygen isotope sequence common among several Greenland ice cores: interstades GI2 to GI24 (≈ OIS2–5 d). This site thus provides the first evidence for an essentially complete series of ‘Dansgaard–Oeschger’ climate events in the MAR. These data reveal that the ~ 100,000 yr preceding the Late Glacial and Holocene in the MAR of North America were characterized by frequently and dynamically changing climate states, and by vegetation shifts that closely tracked the Greenland paleoclimate sequence.  相似文献   
243.
The potential use of spent coffee ground (SCG) for the removal of copper has been investigated as a low‐cost adsorbent for the biosorption of heavy metals. Adsorption batch experiments were conducted to determine isotherms and kinetics. The biosorption equilibrium data were found to fit well the Freundlich model and an experimental maximum biosorption capacity of copper ions 0.214 mmol/g was achieved. The biosorption kinetics of SCG was studied at different adsorbate concentrations (0.1–1.0 mM) and stirring speeds (100–400/min). The results showed an increase in the copper ion uptake with raising the initial metal concentration and the kinetic data followed the pseudo‐second order rate expression. The effect of stirring speed was a significant factor for the external mass transfer resistance at 100/min and coefficients were estimated by the Mathews and Weber model. Biosorption of copper ions onto SCG was observed to be related mainly with the release of calcium and hydrogen ions suggesting that biosorption performance by SCG can be attributed to ion‐exchange mechanism with calcium and hydrogen ions neutralizing the carboxyl and hydroxyl groups of the biomass.  相似文献   
244.
A common problem faced by geography departments, particularly during times of fiscal compression and mounting pressure for accountability, is how to compare themselves and their faculty with others. The recent revolution in bibliometrics provides a growing volume of data that can be used in benchmarking exercises. In this article, we assess the production and citation of journal articles and books by tenure-track and tenured faculty in selected U.S. and Canadian geography departments (n = 17) according to a set of readily derived and transparent performance indicators derived from publicly available data. Scopus was used to assess article production and citation; Google Scholar was used for book citation. Results point to significant heterogeneity in department characteristics, productivity, and citation of published work. The number of publications, citations, and h-Index scores among scholars in the sample (n = 369) is related strongly to academic age and subfield of enquiry (i.e., physical or human geography) but not—despite apparently marked differences in output and citations—to gender.  相似文献   
245.
This article focuses on the use of map-based multicriteria analysis to develop a negotiation support tool for land use allocation. Spatial multicriteria analysis is used to make explicit trade-offs between objectives and to provide guidance and feedback on the land use changes negotiated by the participants. Digital maps are the means of communication among workshop participants, and an interactive mapping device (the ‘Touch table’) is used as the interface. Participants are informed about the relevant trade-offs on the map and use this information to change the land use maps. The approach is tested during a negotiation session as part of the land use planning process of the Bodegraven polder, a peat meadow area in the Netherlands.  相似文献   
246.
Abstract— We surveyed the impact crater populations of Venus and the Moon, dry targets with and without an atmosphere, to characterize how the 3‐dimensional shape of a crater and the appearance of the ejecta blanket varies with impact angle. An empirical estimate of the impact angle below which particular phenomena occur was inferred from the cumulative percentage of impact craters exhibiting different traits. The results of the surveys were mostly consistent with predictions from experimental work. Assuming a sin2θ dependence for the cumulative fraction of craters forming below angle θ, on the Moon, the following transitions occur: >?45 degrees, the ejecta blanket becomes asymmetric; >?25 degrees, a forbidden zone develops in the uprange portion of the ejecta blanket, and the crater rim is depressed in that direction; >?15 degrees, the rim becomes saddle‐shaped; >?10 degrees, the rim becomes elongated in the direction of impact and the ejecta forms a “butterfly” pattern. On Venus, the atmosphere causes asymmetries in the ejecta blanket to occur at higher impact angles. The transitions on Venus are: >?55 degrees, the ejecta becomes heavily concentrated downrange; >?40 degrees, a notch in the ejecta that extends to the rim appears, and as impact angle decreases, the notch develops into a larger forbidden zone; >?10 degrees, a fly‐wing pattern develops, where material is ejected in the crossrange direction but gets swept downrange. No relationship between location or shape of the central structure and impact angle was observed on either planet. No uprange steepening and no variation in internal slope or crater depth could be associated with impact angle on the Moon. For both planets, as the impact angle decreases from vertical, first the uprange and then the downrange rim decreases in elevation, while the remainder of the rim stays at a constant elevation. For craters on Venus >?15 km in diameter, a variety of crater shapes are observed because meteoroid fragment dispersal is a significant fraction of crater diameter. The longer path length for oblique impacts causes a correlation of clustered impact effects with oblique impact effects. One consequence of this correlation is a shallowing of the crater with decreasing impact angle for small craters.  相似文献   
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249.
Ketoconazole is a fungicidal drug that inhibits function of cytochrome P450s in the synthesis of steroids. To examine if inhibition of P450 function affects gene expression in a dynamic manner, we conducted in vitro exposures of ovary tissue from fathead minnows (Pimephales promelas) to 0.5 microM ketoconazole to investigate effects on steroid production and gene expression over time. Expression of four key steroidogenesis genes was examined at 1, 6, and 12h of exposure. 11 beta- and 20 beta-hydroxysteroid dehydrogenases were down regulated at 1h and Cytochrome P450 17 was down-regulated at 12h, consistent with the absence of steroid production. In contrast, cytochrome P450 19A was up-regulated at 6h, indicating feedback regulation. Microarray analysis of 12h exposures indicated enrichment of biological processes involved in neurotransmitter secretion, lymphocyte cell activation, sodium ion transport, and embryonic development. These data suggest that, with the exception of cytochrome P450 19A, these steroid metabolic genes are regulated in a feed forward manner and that the effects of ketoconazole may be broader than anticipated based on the mechanism of action alone.  相似文献   
250.
A common first step in conservation planning and resource management is to identify and classify habitat types, and this has led to a proliferation of habitat classification systems. Ideally, classifications should be scientifically and conceptually rigorous, with broad applicability across spatial and temporal scales. Successful systems will also be flexible and adaptable, with a framework and supporting lexicon accessible to users from a variety of disciplines and locations. A new, continental-scale classification system for coastal and marine habitats—the Coastal and Marine Ecological Classification Standard (CMECS)—is currently being developed for North America by NatureServe and the National Oceanic and Atmospheric Administration (NOAA). CMECS is a nested, hierarchical framework that applies a uniform set of rules and terminology across multiple habitat scales using a combination of oceanographic (e.g. salinity, temperature), physiographic (e.g. depth, substratum), and biological (e.g. community type) criteria. Estuaries are arguably the most difficult marine environments to classify due to large spatio-temporal variability resulting in rapidly shifting benthic and water column conditions. We simultaneously collected data at eleven subtidal sites in the Columbia River Estuary (CRE) in fall 2004 to evaluate whether the estuarine component of CMECS could adequately classify habitats across several scales for representative sites within the estuary spanning a range of conditions. Using outputs from an acoustic Doppler current profiler (ADCP), CTD (conductivity, temperature, depth) sensor, and PONAR (benthic dredge) we concluded that the CMECS hierarchy provided a spatially explicit framework in which to integrate multiple parameters to define macro-habitats at the 100 m2 to >1000 m2 scales, or across several tiers of the CMECS system. The classification's strengths lie in its nested, hierarchical structure and in the development of a standardized, yet flexible classification lexicon. The application of the CMECS to other estuaries in North America should therefore identify similar habitat types at similar scales as we identified in the CRE. We also suggest that the CMECS could be improved by refining classification thresholds to better reflect ecological processes, by direct integration of temporal variability, and by more explicitly linking physical and biological processes with habitat patterns.  相似文献   
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