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291.
Margaret Johston 《GeoJournal》1989,19(3):323-328
An important component of recreation in mountain areas is the experience of risk. Visitors to such places may be seeking the challenge provided by risk, but they may also experience the negative side of risk — accident and injury. International and domestic visitors to mountain lands may have differing experiences of risk. Indeed, it has been suggested frequently in New Zealand that international visitors face considerably more danger than do New Zealanders in mountain recreation. This view is pursued in an examination of one of the negative outcomes of risk — fatal accidents.Coroners' reports form the basis of a comparative study of such negative outcomes for the two groups. Patterns and trends are elaborated in an exploration of the number, location and cause of fatalities, and the activity of the deceased. Differences between two groups are discussed, as are some reasons why the impression that international visitors face more danger exists. 相似文献
292.
Bruce W. Hayward Hugh R. Grenfell Ashwaq T. Sabaa Margaret S. Morley Mark Horrocks 《Estuaries and Coasts》2006,29(2):165-182
Two short cores of late Holocene, low tidal, estuarine sediment from the sheltered fringes of the Auckland's Waitemata Harbor,
New Zealand, record the following changes through time since human colonization: an abrupt decline and disappearance of marine
molluscs, a major decline and virtual disappearance of ostracods, an abrupt decline in calcareous foraminifera (mostlyAmmonia spp.), a rapid increase, in abundance of agglutinated foraminifera, large diatoms, and freshwater thecamoebians, and an increase
in sedimentation rate, but no consistent trend in change of grain size. The up-core foraminiferal changes mimic their present
day up-estuary zonation, which correlates strongly with decreasing salinity and pH. In both localities the faunal changes
can be correlated with the documented local land-use history and increased freshwater runoff over time. At the head of the
Waitemata Harbor, in Lucas Creek estuary, three phases of foraminiferal faunal change occurred: minor changes during initial
Polynesian forest clearance (1500–1800 AD), a major change in early European times (1840–1870 AD) with clearance of most of
the remaining native forest, and another small change in very, recent times (∼1990s) with urbanization in the Lucas Creek
catchment. On the eastern, seaward fringes of the Waitemata Harbor, in the smaller Tamaki Estuary, no faunal changes occurred
in association with complete forest clearance and establishment of pastoral farming in Polynesian and early European times
(before 1950s). Major foraminiferal and other faunal changes occurred in the late European period (1960s–1970s) coincident
with the onset of major urbanization spreading throughout the Tamaki catchment. Our results suggest increased freshwater runoff
is the major culprit for many of the observed biotic changes in the urbanized estuaries of New Zealand. 相似文献
293.
Margaret R. Mulholland George E. Boneillo Peter W. Bernhardt Elizabeth C. Minor 《Estuaries and Coasts》2009,32(6):1176-1194
To determine the roles of dissolved organic matter in the onset, duration, and decline of blooms of the “brown tide” pelagophyte,
Aureococcus anophagefferens, nutrient and microbial dynamics, heterotrophic and autotrophic carbon (C) and nitrogen (N) uptake, and peptide hydrolysis
were compared in natural populations: (1) seasonally, among physically similar sites in a mid-Atlantic coastal lagoon, Chincoteague
Bay, (2) at an individual site as a bloom initiated, developed, and declined, and (3) in whole versus size-fractionated water.
Throughout the year, urea was the dominant form of N taken up at both bloom and nonbloom sites. C acquisition in the A. anophagefferens (1.2–5.0 μm) size fraction was dominated by bicarbonate uptake during bloom initiation but organic C compounds were taken
up later during and after the bloom. Bacterial productivity was enhanced during and just after the bloom and bacterial abundance
was four times higher at the bloom versus nonbloom site. 相似文献
294.
Cornelis VanderPost Margaret McFarlane 《International Journal of Applied Earth Observation and Geoinformation》2007,9(4):343-359
Locating additional long-term groundwater resources in semi-arid regions of developing countries with growing populations is an expensive undertaking. Simple geographic information system (GIS) techniques can be utilised to facilitate efficient application of expensive geophysical techniques and test-drilling by functioning as an interdisciplinary integration and decision-making tool, especially in data-poor and poorly mapped environments where more sophisticated GIS techniques are not applicable. The paper demonstrates this in the context of the search for groundwater alternatives to the dwindling river water supply in the Boteti area of the Kalahari region in Botswana. 相似文献
295.
296.
297.
Michael J. Mottl Jeffrey S. Seewald Margaret K. Tivey Giora Proskurowski Eoghan Reeves C.-F. You Thomas Pichler 《Geochimica et cosmochimica acta》2011,75(4):1013-76
The Eastern Lau Spreading Center (ELSC) is the southernmost part of the back-arc spreading axis in the Lau Basin, west of the Tonga trench and the active Tofua volcanic arc. Over its 397-km length it exhibits large and systematic changes in spreading rate, magmatic/tectonic processes, and proximity to the volcanic arc. In 2005, we collected 81 samples of vent water from six hydrothermal fields along the ELSC. The chemistry of these waters varies both within and between vent fields, in response to changes in substrate composition, temperature and pressure, pH, water/rock ratio, and input from magmatic gases and subducted sediment. Hot-spring temperatures range from 229° to 363 °C at the five northernmost fields, with a general decrease to the south that is reversed at the Mariner field. The southernmost field, Vai Lili, emitted water at up to 334 °C in 1989 but had a maximum venting temperature of only 121 °C in 2005, due to waning activity and admixture of bottom seawater into the subseafloor plumbing system. Chloride varies both within fields and from one field to another, from a low of 528 mmol/kg to a high of 656 mmol/kg, and may be enriched by phase separation and/or leaching of Cl from the rock. Concentrations of the soluble elements K, Rb, Cs, and B likewise increase southward as the volcanic substrate becomes more silica-rich, especially on the Valu Fa Ridge. Iodine and δ7Li increase southward, and δ11B decreases as B increases, apparently in response to increased input from subducted sediment as the arc is approached. Species that decrease southward as temperature falls are Si, H2S, Li, Na/Cl, Fe, Mn, and 87Sr/86Sr, whereas pH, alkalinity, Ca, and Sr increase. Oxygen isotopes indicate a higher water/rock ratio in the three systems on Valu Fa Ridge, consistent with higher porosity in more felsic volcanic rocks. Vent waters at the Mariner vent field on the Valu Fa Ridge are significantly hotter, more acid and metal-rich, less saline, and richer in dissolved gases and other volatiles, including H2S, CO2, and F, than the other vent fields, consistent with input of magmatic gases. The large variations in geologic and geophysical parameters produced by back-arc spreading along the ELSC, which exceed those along mid-ocean ridge spreading axes, produce similar large variations in the composition of vent waters, and thus provide new insights into the processes that control the chemistry of submarine hot springs. 相似文献
298.
The aim of this short article is to stress the importance of using only positive-definite functions as models for covariance functions and variograms.The two examples presented show that a negative variance can easily be obtained when a nonadmissible function is chosen for the variogram model. 相似文献
299.
300.
The paper reviews a number of challenges associated with reducing degradation and its related emissions through national approaches
to REDD+ under UNFCCC policy. It proposes that in many countries, it may in the short run be easier to deal with the kinds
of degradation that result from locally driven community over-exploitation of forest for livelihoods, than from selective
logging or fire control. Such degradation is low-level, but chronic, and is experienced over very large forest areas. Community
forest management programmes tend to result not only in reduced degradation, but also in forest enhancement; moreover they
are often popular, and do not require major political shifts. In principle these approaches therefore offer a quick start
option for REDD+. Developing reference emissions levels for low-level locally driven degradation is difficult however given
that stock losses and gains are too small to be identified and measured using remote sensing, and that in most countries there
is little or no forest inventory data available. We therefore propose that forest management initiatives at the local level,
such as those promoted by community forest management programmes, should monitor, and be credited for, only the net increase
in carbon stock over the implementation period, as assessed by ground level surveys at the start and end of the period. This
would also resolve the problem of nesting (ensuring that all credits are accounted for against the national reference emission
level), since communities and others at the local level would be rewarded only for increased sequestration, while the national
reference emission level would deal only with reductions in emissions from deforestation and degradation. 相似文献