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941.
The shallow marine hydrothermal vents near Ambitle Island in eastern Papua New Guinea discharge hot, slightly acidic, As-rich, chemically reduced fluid into cool, slightly alkaline, oxygenated seawater. Gradients in temperature, pH, and total As (AsT), among others, are established as the two aqueous phases mix. The hydrothermal fluid contained 900 μg/L AsT, almost exclusively present as the reduced AsIII, while local seawater measured between 1.2 and 2.4 μg/L As, with approximately equal levels of AsIII and AsV. Of particular interest in this study was As speciation and abundance in pore waters as a function of sediment depth and as a function of distance from the area of focused venting. With increasing distance, AsT concentration in the pore water decreased rapidly, but remained elevated up to 300 m from the area of focused venting when compared to a non-hydrothermal control site. As a function of depth (to 100 cm) AsT concentration in the pore water profiles was elevated and generally increased with depth. Surprisingly, aqueous AsV far exceeded aqueous AsIII at almost all distances and depths investigated, while at the control site the AsIII concentration exceeded that of AsV. In the Tutum Bay hydrothermal system, chemical disequilibria among As species provide potential metabolic energy for arsenite oxidizing microorganisms where hydrothermal fluid mixes with seawater near the vent orifice, and for arsenate reducing microorganisms with increasing distance and depth from the hydrothermal point source. 相似文献
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This paper investigates the impact ash fall would have on dairy farming, based on a study of ‘Tulachard’, a dairy farming
operation at Rerewhakaaitu, North Island, New Zealand. It includes analysis of the potential effects on the dairy shed and
milking machine, electrical supply and distribution, water supply and distribution, tractors and other farm vehicles, farm
buildings (haysheds, pump sheds, implement sheds, etc.), milk-tanker access to the farm and critical needs of dairy cows and
farm to keep milking. One of the most vulnerable areas identified in the study was the cooling of milk at the milking shed,
pending dairy tanker pick-up. The cooling system’s condenser is exposed to the atmosphere and falling ash would make it highly
vulnerable. Laboratory testing with wet and dry ash was conducted to determine its resilience to ash ingestion. It was found
to perform satisfactorily during dry testing, but during wet testing significant clogging/blocking of the condenser’s radiator
occurred, dramatically reducing airflow through the condenser. Specific mitigation recommendations have been developed that
include cleaning with compressed air and adapting farm management techniques to lessen usage of the condenser during an ash-fall
event. Specific recommendations for management of dairy farm operation are given to mitigate the effects of an ash-fall event.
相似文献
James W. ColeEmail: |
945.
A comparison of TRMM to other basin-scale estimates of rainfall during the 1999 Hurricane Floyd flood 总被引:5,自引:2,他引:3
The volumetric rainfall attributed to Hurricane Floyd in 1999 was computed for the bulk of the Tar, Neuse, and Cape Fear River
Basins in eastern North Carolina, USA from the Tropical Rainfall Measuring Mission (TRMM) Multi-Satellite Precipitation Analysis
(TMPA) research product, and compared with volumes computed using kriged gauge data and one centrally located radar. TMPA
showed similar features in the band of heaviest rainfall with kriged and radar data, but was higher in the basin-scale integrations.
Furthermore, Floyd’s direct runoff volumes were computed and divided by the volumetric rainfall estimates to give runoff coefficients
for the three basins. The TMPA, having the larger storm totals, would suggest greater infiltration during Floyd than the gauge
and radar estimates would. Finally, we discuss a concept for adjusting the United States Department of Agriculture Natural
Resources Conservation Service rainfall-runoff model when predicting discharge values from real-time TMPA in ungauged river
basins.
相似文献
Scott CurtisEmail: |
946.
Journal of Oceanology and Limnology - Synechococcus is one of the most abundant picocyanobacteria in marine ecosystem, and the absence of Prochlorococcus would make it indispensable as a primary... 相似文献
947.
High salt and low temperature are the bottlenecks for the remove of oil contaminants by enriched crude-oil degrading microbiota in Liaohe Estuarine Wetland(LEW),China.To improve the performance of crude-oil removal,microbiota was further immobilized by two methods,i.e.,sodium alginate(SA),and polyvinyl alcohol and sodium alginate(PVA+SA).Results showed that the crude oil was effectively removed by the enrichment with an average degrading ratio of 19.42-31.45 mg(L d)?1.The optimal inoculum size for the n-alkanes removal was 10%and 99.89%.Some members of genera Acinetobacter,Actinophytocola,Aquabac-terium,Dysgonomonas,Frigidibacter,Sphingobium,Serpens,and Pseudomonas dominated in crude-oil degrading microflora.Though the removal efficiency was lower than free bacteria when the temperature was 15℃,SA and PVA+SA immobilization im-proved the resistance to salinity.The composite crude-oil degrading microbiota in this study demonstrated a perspective potential for crude oil removal from surface water under high salinity and low temperature conditions. 相似文献
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Calvin J. Heusser Linda E. Heusser & Thomas V. Lowell 《Geografiska Annaler: Series A, Physical Geography》1999,81(2):231-284
Subantarctic Parkland and Subantarctic–North Patagonian Evergreen Forest, embracing >40,000 14 C years of middle and late Llanquihue glaciation, are reconstructed from pollen contained in multiple interdrift deposits and cores of lake sediments. The subantarctic plant communities at low elevations have since been replaced by temperate Valdivian Evergreen Forest. Data in support of the vegetation reconstruction derive from close-interval sampling (>1400 pollen analysed stratigraphic levels) and high-resolution chronology (>200 AMS and conventional radiocarbon-dated horizons). Pollen sequences are from 15 sites, eight of which are exposures and seven mires, located in relation to lobes of piedmont glaciers that occupied Lago Llanquihue, Seno Reloncav', Golfo de Ancud, and the east-central sector of Isla Grande de Chiloí at the northern limit of the Golfo Corcovado lobe. Recurring episodes of grass maxima representing Subantarctic Parkland, when grass and scrub became widespread among patches of southern beech (Nothofagus), bear a relationship to glacial advances. The implication of the maxima, prominent with advances at 22,400 and 14,800 14C yr BP during late Llanquihue glaciation in marine oxygen-isotope Stage 2, is of successive intervals of cold climate with summer temperatures estimated at 6–8°C below the modern mean. The earliest recorded maximum at >50,000 14C yr BP is possibly during late Stage 4. At the time of middle Llanquihue glaciation in Stage 3, cool, humid interstades on Isla Grande de Chiloé with Subantarctic Evergreen Forest, which under progressive cooling after 47,000 14C yr BP was increasingly replaced by parkland. During stepwise deglaciation, when transitional beech woodland communities supplanting parkland became diversified by formation of thermophilous North Patagonian Evergreen Forest, warming in the order of 5–6°C was abrupt after 14,000 14C yr BP . Closed-canopy North Patagonian Evergreen Forest was established by 12,500 14C yr BP . Later, after c. 12,000 until 10,000 14C yr BP , depending on location, forest at low elevations became modified by expansion of a cold-tolerant element indicative of ≥2–3°C cooler climate. This stepwise climatic sequence is seen at all late-glacial sites. Cool, humid interstadial conditions, punctuated by cold stadial climate, are characteristic of the last ≥40,000 14C years of the Pleistocene at midlatitude in the Southern Hemisphere. Pollen sequences from southern South America and terrestrial–marine records from the New Zealand–Tasmania sector express a broad measure of synchrony of vegetational/climatic change for marine oxygen-isotope Stages 2–3. The data, combined with the timing of glacial maxima in the Southern Andes, Southern Alps of New Zealand, and in the Northern Hemisphere, are indicative of synchronous, millennial-scale, midlatitude climatic changes in the polar hemispheres. 相似文献
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