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311.
Katherine C. Filippino Margaret R. Mulholland Peter W. Bernhardt George E. Boneillo Ryan E. Morse Matthew Semcheski Harold Marshall Nancy G. Love Quinn Roberts Deborah A. Bronk 《Estuaries and Coasts》2011,34(2):269-280
Total maximum daily loads for nitrogen (N) are currently being established for the Chesapeake Bay watershed. While we know
inorganic N is bioavailable in the environment and therefore its input contributes to cultural eutrophication, the bioavailability
of organic N is unclear. Using bioassay experiments, we examined the impact of effluent-derived organic nitrogen (EON) from
wastewater treatment plants on natural water samples collected along an estuarine/salinity gradient within the lower Chesapeake
Bay watershed. All of the inorganic N and between 31% and 96% of the EON was removed during biotic bioassays within the first
2 days. Further, there was substantial abiotic reactivity of effluent N when it was added to natural water samples. Results
demonstrate that organic and inorganic N in effluent is removed to support the growth of microbial communities. These are
the first results aimed at assessing the reactivity of EON in natural waters along an estuarine/salinity gradient. 相似文献
312.
Toxicity comparison of biosurfactants and synthetic surfactants used in oil spill remediation to two estuarine species 总被引:1,自引:0,他引:1
The relative environmental toxicities of synthetic and biogenic surfactants used in oil spill remediation efforts are not well understood. Acute and chronic toxicities of three synthetic surfactants and three microbiologically produced surfactants were determined and compared in this study for the estuarine epibenthic invertebrate, Mysidopsis bahia and the inland silverside, Menidia beryllina. The toxicities of the surfactant were determined in standard laboratory static and static-renewal tests of 4-7 d duration. Results were specific to the surfactant, response parameter and test species. The LC50 values (nominal concentrations) for M. bahia ranged from 3.3 mg/l (Triton X-100) to >1000 mg/l (PES-61) and 2.5 mg/l (Triton X-100) to 413.6 mg/l (PES-61) for M. beryllina. Chronic first-effect concentrations (mg/l) for the six surfactants ranged from 2.3 to 465.0 (M. beryllina) and 1.0 to >1000.0 (M. bahia) based on reductions in growth and fecundity. Few generalizations could be made concerning the results due to their variability but M. bahia was generally the more sensitive species and the toxicities of the biosurfactants were intermediate to those of the synthetic surfactants. 相似文献
313.
Katherine F. Fornash P. Jonathan Patchett George E. Gehrels Jon E. Spencer 《Contributions to Mineralogy and Petrology》2013,165(6):1295-1310
The Santa Catalina Mountains, SE Arizona, was one of the first metamorphic core complexes to be described. Despite its status as a type example, relatively little is known about precise ages and origins of the intrusive rocks that make up most of the crystalline core. U–Pb and Hf isotopic data by laser ablation–inductively coupled plasma–mass spectrometry from zircons and Nd isotopic results from whole rocks were obtained for 12 granitoids ranging from 1,440 to 26 Ma. Results confirm that the 1.44-Ga Oracle Granite extends through the Catalina Range as variably mylonitic granite and banded gneiss. Laramide intrusions (67–73 Ma) display initial εNd values ?5 to ?8 and εHf from ?7.5 to ?9. Magmatic ages for the prominent white granite sills of the Wilderness suite are 46–57 Ma, in agreement with Terrien (2012), and these granites have initial εNd values ?8 to ?10 and εHf from ?7 to ?14. Lastly, the undeformed Catalina Granite has an age of 26 Ma, with an initial εNd and εHf of ?6 and ?8, respectively. Our Nd results agree with limited results from Farmer and DePaolo (89:10141–10160, 1984). Although the Catalina Granite seems to have a significant juvenile component based on Nd and Hf, most of the Laramide and Wilderness intrusions contain Nd and Hf compositions lying close to the evolution of 1.44-Ga Oracle Granites, a fact that is confirmed by the U–Pb data, which show both 1.7- and 1.4-Ga zircon cores in these samples, with 1.4 Ga as the dominant core age. In order to become the dominant source of most of the 72–45-Ma magmas, the Oracle pluton must not only extend across the whole Catalina region, but also have abundant deep-seated equivalents to provide magma sources. 相似文献
314.
Katherine McDonough Ludovic Moncla Matje van de Camp 《International journal of geographical information science》2013,27(12):2498-2522
ABSTRACTGeographic text analysis (GTA) research in the digital humanities has focused on projects analyzing modern English-language corpora. These projects depend on temporally specific lexicons and gazetteers that enable place name identification and georesolution. Scholars working on the early modern period (1400–1800) lack temporally appropriate geoparsers and gazetteers and have been reliant on general purpose linked open data services like Geonames. These anachronistic resources introduce significant information retrieval and ethical challenges for early modernists. Using the geography entries of the canonical eighteenth-century Encyclopédie, we evaluate rule-based named entity recognition (NER) systems to pinpoint areas where they would benefit from adjustments for processing historical corpora. As we demonstrate, annotating nested and extended place information is one way to improve early modern GTA. Working with Enlightenment sources also motivates a critique of the landscape of digital geospatial data. 相似文献
315.
Matt J. Jarvis Steve Rawlings Steve Eales Katherine M. Blundell rew J. Bunker Steve Croft Ross J. McLure Chris J. Willott 《Monthly notices of the Royal Astronomical Society》2001,326(4):1585-1600
In this paper, the third and final of a series, we present complete K -band imaging and some complementary I -band imaging of the filtered 6C* sample. We find no systematic differences between the K – z relation of 6C* radio galaxies and those from complete samples, so the near-infrared properties of luminous radio galaxies are not obviously biased by the additional 6C* radio selection criteria (steep spectral index and small angular size). The 6C* K – z data significantly improve delineation of the K – z relation for radio galaxies at high redshift ( z >2) . Accounting for non-stellar contamination, and for correlations between radio luminosity and stellar mass, we find little support for previous claims that the underlying scatter in the stellar luminosity of radio galaxies increases significantly at z >2 . In a particular spatially flat universe with a cosmological constant (ΩM =0.3 and ΩΛ =0.7) , the most luminous radio sources appear to be associated with galaxies with a luminosity distribution with a high mean (≈5 L *), and a low dispersion ( σ ∼0.5 mag) which formed their stars at epochs corresponding to z ≳2.5 . This result is in line with recent submillimetre studies of high-redshift radio galaxies and the inferred ages of extremely red objects from faint radio samples. 相似文献
316.
317.
We investigate a number of potential foregrounds for an ambitious goal of future radio telescopes such as the Square Kilometer Array (SKA) and the Low Frequency Array (LOFAR): spatial tomography of neutral gas at high redshift in 21-cm emission. While the expected temperature fluctuations due to unresolved radio point sources is highly uncertain, we point out that free–free emission from the ionizing haloes that reionized the Universe should define a minimal bound. This emission is likely to swamp the expected brightness temperature fluctuations, making proposed detections of the angular patchwork of 21-cm emission across the sky unlikely to be viable. Hα observations with JWST could place an upper bound on the contribution of high-redshift sources to the free–free background. An alternative approach is to discern the topology of reionization from spectral features due to 21-cm emission along a pencil-beam slice. This requires tight control of the frequency-dependence of the beam in order to prevent foreground sources from contributing excessive variance. We also investigate potential contamination by galactic and extragalactic radio recombination lines (RRLs). These are unlikely to be show-stoppers, although little is known about the distribution of RRLs away from the Galactic plane. The mini-halo emission signal is always less than that of the intergalactic medium (IGM), making mini-haloes unlikely to be detectable. If they are seen, it will be only in the very earliest stages of structure formation at high redshift, when the spin temperature of the IGM has not yet decoupled from the cosmic microwave background. 相似文献
318.
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320.
The high hydraulic conductivity of three wooded tropical peat swamps in northeast Peru: measurements and implications for hydrological function 下载免费PDF全文
Thomas J. Kelly Andy J. Baird Katherine H. Roucoux Timothy R. Baker Eurídice N. Honorio Coronado Marcos Ríos Ian T. Lawson 《水文研究》2014,28(9):3373-3387
The form and functioning of peatlands depend strongly on their hydrological status, but there are few data available on the hydraulic properties of tropical peatlands. In particular, the saturated hydraulic conductivity (K) has not previously been measured in neotropical peatlands. Piezometer slug tests were used to measure K at two depths (50 and 90 cm) in three contrasting forested peatlands in the Peruvian Amazon: Quistococha, San Jorge and Buena Vista. Measured K at 50 cm depth varies between 0.00032 and 0.11 cm s?1, and at 90 cm, it varies between 0.00027 and 0.057 cm s?1. Measurements of K taken from different areas of Quistococha showed that spatial heterogeneity accounts for ~20% of the within‐site variance and that depth is a good predictor of K. However, K did not vary significantly with depth at Buena Vista and San Jorge. Statistical analysis showed that ~18% of the variance in the K data can be explained by between‐site differences. Simulations using a simple hydrological model suggest that the relatively high K values could lead to lowering of the water table by >10 cm within ~48 m of the peatland edge for domed peatlands, if subjected to a drought lasting 30 days. However, under current climatic conditions, even with high K, peatlands would be unable to shed the large amount of water entering the system via rainfall through subsurface flow alone. We conclude that most of the water leaves these peatlands via overland flow and/or evapotranspiration. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献