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281.
Influence of sea surface temperature on the European heat wave of 2003 summer. Part I: an observational study 总被引:2,自引:0,他引:2
The heat wave affecting Europe during summer of 2003 is analyzed in detail with observational and reanalysis data. Surface, middle and upper troposphere analysis reveal particular circulation patterns related to an atmospheric blocking condition. In general seasonal anomalies, like this intense heat wave, are strongly related to boundary conditions. Composites and empirical orthogonal functions analysis provide evidence for an organized structure in the sea surface temperature (SST) anomaly field: high SSTs in the Mediterranean basin, the North Sea and further north toward the Arctic Circle were observed mainly in the months of June and August. The outcome of this analysis on observational data shows the SST as one of the possible factors in enhancing the heat wave in the European area. 相似文献
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283.
Ramos-Gómez J Martins M Raimundo J Vale C Martín-Díaz ML DelValls TA 《Marine pollution bulletin》2011,62(7):1538-1549
Sediment toxicity assessments using caged organisms present advantages over using laboratory and native community studies. The use of caged Arenicola marina in sediment toxicity assessments was evaluated. Lugworms were exposed in situ to sediments from coastal and port areas in Spain for seven days, and the activities of the biotransformation enzymes ethoxyresorufin O-deethylase, dibenzylfluorescein dealkylase and glutathione S-transferase, the activities of the antioxidant enzymes glutathione reductase and glutathione peroxidase and lipid peroxidation were then analyzed as biomarkers. Biomarker results and sediment physicochemical data were integrated. Cádiz Bay (SW Spain) sediments presented metal contamination that was not linked to a biochemical response. In LPGC Port (SW Spain), Pb contamination exhibited a moderate toxic potential, while PAHs, and presumably pharmaceuticals, provoked biochemical responses that efficiently prevented lipid peroxidation. In Santander Bay (N Spain), exposure to PAHs and, presumably, pharmaceuticals induced biomarker responses, but lipid peroxidation occurred nevertheless. These results indicated that caged A. marina were effective for the assessment of sediment quality and that the selected biomarkers were sufficiently sensitive to identify chemical exposure and toxicity. 相似文献
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286.
Paul A. Bukaveckas Laura E. Barry Matthew J. Beckwith Valerie David Brent Lederer 《Estuaries and Coasts》2011,34(3):569-582
Longitudinal variation in factors affecting phytoplankton production were analyzed to better understand the mechanisms that
cause the formation of a chlorophyll maximum within the tidal freshwater James River. Phytoplankton production was two- to
threefold higher in the region where persistent elevated chlorophyll concentrations occurred. Near this site, the morphology
of the James transitions from a narrow, deep channel to a broad expanse with shallow areas adjoining the main channel. Shallower
depths resulted in greater average irradiance within the water column and suggest that release from light limitation was the
principal factor accounting for the location of the chlorophyll maximum. Grazing rates were low indicating that little of
the algal production was directly consumed by zooplankton. Low exploitation by zooplankton was attributed to poor food quality
due to high concentrations of non-algal particulate matter and potential presence of cyanobacteria. Metabolism data suggest
that two thirds of net primary production was respired in the vicinity of the chlorophyll maximum and one third was exported
via fluvial and tidal advection. Comparison of water column and ecosystem metabolism indicates that the bulk of respiration
occurred within the sediments and that sedimentation was the dominant loss process for phytoplankton. 相似文献
287.
Thomas S. Bianchi Laura A. Wysocki Kathryn M. Schreiner Timothy R. Filley D. Reide Corbett Alexander S. Kolker 《Aquatic Geochemistry》2011,17(4-5):431-456
High sedimentation rates along river-dominated margins make these systems important repositories for organic carbon derived from both allochthonous and autochthonous sources. Using elemental carbon/nitrogen ratios, molecular biomarker (lignin phenol), and stable carbon isotopic (bulk and compound-specific) analyses, this study examined the sources of organic carbon to the Louisiana shelf within one of the primary dispersive pathways of the Mississippi River. Surface sediment samples were collected from stations across the inner, mid, and outer Louisiana shelf, within the Mississippi River plume region, during two cruises in the spring and fall of 2000. Lignin biomarker data showed spatial patterns in terrestrial source plant materials within the river plume, such that sediments near the mouth of the Mississippi River were comparatively less degraded and richer in C4 plant carbon than those found at mid-depth regions of the shelf. A molecular and stable isotope-based mixing model defining riverine, marsh, and marine organic carbon suggested that the highest organic carbon inputs to the shelf in spring were from marine sources (55?C61% marine organic carbon), while riverine organic carbon was the highest (63%) in fall, likely due to lower inputs of marine organic carbon at this time compared with the spring season. This model also indicated that marsh inputs, ranging from 19 to 34% and 3?C15% of the organic carbon in spring and fall, respectively, were significantly more important sources of organic carbon on the inner Louisiana shelf than previously suggested. Finally, we propose that the decomposition of terrestrial-derived organic carbon (from the river and local wetlands sources) in mobile muds may serve as a largely unexplored additional source of oxygen-consuming organic carbon in hypoxic bottom waters of the Louisiana shelf. 相似文献
288.
Henry A. Ruhl Michel AndréLaura Beranzoli M. Namik Ça?atayAna Colaço Mathilde CannatJuanjo J. Dañobeitia Paolo FavaliLouis Géli Michael GilloolyJens Greinert Per O.J. HallRobert Huber Johannes KarstensenRichard S. Lampitt Kate E. LarkinVasilios Lykousis Jürgen MienertJ. Miguel Miranda Roland PersonImants G. Priede Ingrid PuillatLaurenz Thomsen Christoph Waldmann 《Progress in Oceanography》2011,91(1):1-33
Society’s needs for a network of in situ ocean observing systems cross many areas of earth and marine science. Here we review the science themes that benefit from data supplied from ocean observatories. Understanding from existing studies is fragmented to the extent that it lacks the coherent long-term monitoring needed to address questions at the scales essential to understand climate change and improve geo-hazard early warning. Data sets from the deep sea are particularly rare with long-term data available from only a few locations worldwide. These science areas have impacts on societal health and well-being and our awareness of ocean function in a shifting climate.Substantial efforts are underway to realise a network of open-ocean observatories around European Seas that will operate over multiple decades. Some systems are already collecting high-resolution data from surface, water column, seafloor, and sub-seafloor sensors linked to shore by satellite or cable connection in real or near-real time, along with samples and other data collected in a delayed mode. We expect that such observatories will contribute to answering major ocean science questions including: How can monitoring of factors such as seismic activity, pore fluid chemistry and pressure, and gas hydrate stability improve seismic, slope failure, and tsunami warning? What aspects of physical oceanography, biogeochemical cycling, and ecosystems will be most sensitive to climatic and anthropogenic change? What are natural versus anthropogenic changes? Most fundamentally, how are marine processes that occur at differing scales related?The development of ocean observatories provides a substantial opportunity for ocean science to evolve in Europe. Here we also describe some basic attributes of network design. Observatory networks provide the means to coordinate and integrate the collection of standardised data capable of bridging measurement scales across a dispersed area in European Seas adding needed certainty to estimates of future oceanic conditions. Observatory data can be analysed along with other data such as those from satellites, drifting floats, autonomous underwater vehicles, model analysis, and the known distribution and abundances of marine fauna in order to address some of the questions posed above. Standardised methods for information management are also becoming established to ensure better accessibility and traceability of these data sets and ultimately to increase their use for societal benefit. The connection of ocean observatory effort into larger frameworks including the Global Earth Observation System of Systems (GEOSS) and the Global Monitoring of Environment and Security (GMES) is integral to its success. It is in a greater integrated framework that the full potential of the component systems will be realised. 相似文献
289.
Laura L. Brothers Joseph T. Kelley Daniel F. Belknap Walter A. Barnhardt Brian D. Andrews Melissa Landon Maynard 《Geo-Marine Letters》2011,31(4):237-248
Mechanisms and timescales responsible for pockmark formation and maintenance remain uncertain, especially in areas lacking
extensive thermogenic fluid deposits (e.g., previously glaciated estuaries). This study characterizes seafloor activity in
the Belfast Bay, Maine nearshore pockmark field using (1) three swath bathymetry datasets collected between 1999 and 2008,
complemented by analyses of shallow box-core samples for radionuclide activity and undrained shear strength, and (2) historical
bathymetric data (report and smooth sheets from 1872, 1947, 1948). In addition, because repeat swath bathymetry surveys are
an emerging data source, we present a selected literature review of recent studies using such datasets for seafloor change
analysis. This study is the first to apply the method to a pockmark field, and characterizes macro-scale (>5 m) evolution
of tens of square kilometers of highly irregular seafloor. Presence/absence analysis yielded no change in pockmark frequency
or distribution over a 9-year period (1999–2008). In that time pockmarks did not detectably enlarge, truncate, elongate, or
combine. Historical data indicate that pockmark chains already existed in the 19th century. Despite the lack of macroscopic
changes in the field, near-bed undrained shear-strength values of less than 7 kPa and scattered downcore 137Cs signatures indicate a highly disturbed setting. Integrating these findings with independent geophysical and geochemical
observations made in the pockmark field, it can be concluded that (1) large-scale sediment resuspension and dispersion related
to pockmark formation and failure do not occur frequently within this field, and (2) pockmarks can persevere in a dynamic
estuarine setting that exhibits minimal modern fluid venting. Although pockmarks are conventionally thought to be long-lived
features maintained by a combination of fluid venting and minimal sediment accumulation, this suggests that other mechanisms
may be equally active in maintaining such irregular seafloor morphology. One such mechanism could be upwelling within pockmarks
induced by near-bed currents. 相似文献
290.
Harindra J. S. Fernando Brett Verhoef Silvana Di Sabatino Laura S. Leo Seoyeon Park 《Boundary-Layer Meteorology》2013,147(3):443-468
Motivated by air quality and numerical modelling applications as well as recent theoretical advancements in the topic, a field experiment, dubbed transition flow experiment, was conducted in Phoenix, Arizona to study the evening transition in complex terrain (shift of winds from upslope to downslope). Two scenarios were considered: (i) the flow reversal due to a change of buoyancy of a cooled slab of air near the ground, and (ii) the formation of a transition front. A suite of in-situ flow, turbulence and particulate matter (PM) concentration sensors, vertically profiling tethered balloons and remote sensors were deployed, and a mesoscale numerical model provided guidance for interpreting observations. The results were consistent with the front formation mechanism, where it was also found that enhanced turbulence associated with the front increases the local PM concentration. During the transition period the flow adjustment was complex, involving the arrival of multiple fronts from different slopes, directional shear between fronts and episodic turbulent mixing events. The upward momentum diffusion from the incipient downslope flow was small because of stable stratification near the ground, and full establishment of downslope flow occurred over several hours following sunset. Episodic frontal events pose challenges to the modelling of the evening transition in complex terrain, requiring conditional parametrizations for subgrid scales. The observed increase of PM concentration during the evening transition has significant implications for the regulatory enforcement of PM standards for the area. 相似文献