全文获取类型
收费全文 | 551篇 |
免费 | 26篇 |
国内免费 | 5篇 |
专业分类
测绘学 | 41篇 |
大气科学 | 49篇 |
地球物理 | 178篇 |
地质学 | 179篇 |
海洋学 | 26篇 |
天文学 | 57篇 |
综合类 | 3篇 |
自然地理 | 49篇 |
出版年
2024年 | 2篇 |
2023年 | 3篇 |
2022年 | 11篇 |
2021年 | 7篇 |
2020年 | 15篇 |
2019年 | 10篇 |
2018年 | 16篇 |
2017年 | 14篇 |
2016年 | 24篇 |
2015年 | 20篇 |
2014年 | 20篇 |
2013年 | 37篇 |
2012年 | 30篇 |
2011年 | 27篇 |
2010年 | 22篇 |
2009年 | 41篇 |
2008年 | 24篇 |
2007年 | 29篇 |
2006年 | 25篇 |
2005年 | 20篇 |
2004年 | 18篇 |
2003年 | 18篇 |
2002年 | 15篇 |
2001年 | 16篇 |
2000年 | 9篇 |
1999年 | 9篇 |
1998年 | 12篇 |
1997年 | 15篇 |
1996年 | 6篇 |
1995年 | 7篇 |
1994年 | 7篇 |
1993年 | 6篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1987年 | 7篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1981年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 3篇 |
1973年 | 1篇 |
排序方式: 共有582条查询结果,搜索用时 15 毫秒
391.
392.
Thomas Wilson Carol Stewart Jim Cole David Johnston Shane Cronin 《Environmental Earth Sciences》2010,61(4):675-688
Agriculture is critically dependent on continuity of water quality and quantity. It is well-established that even small quantities
of volcanic ash can disrupt municipal water supplies, with known impacts to quality including: acidification, increases in
turbidity and ionic concentrations. In addition, delivery systems may be blocked or damaged by hard and abrasive suspended
ash and related ash-cleanup operations place extra stress on water reserves. The aim of this study was to characterise the
key areas of vulnerability of farm water supplies to volcanic ashfall, and to identify management recommendations to reduce
these. From literature review and case studies of farms impacted by the 1991 Pinatubo (Philippines) and 1991 Hudson (Chile)
eruptions, key issues were: sedimentation of irrigation ditches and drinking water ponds, turbidity induced abrasion of sprinkler
nozzles and water pumps, and damage to electric pumps (by ash on air-intakes). Building on this, we characterised the water-use
regimes and water supply system vulnerability of eight case-study farms from across the North Island, New Zealand. From this,
we propose an index system to evaluate the vulnerability of farm water supply systems. The key contributors to the vulnerability
index include: water source, storage capacity, reliance on electricity, independence/interconnectedness of system elements,
volume of water use and other load factors. These allow identification of key strategies for mitigating water supply vulnerability
during prevention, preparation, response and recovery phases of a volcanic eruption. 相似文献
393.
Sara S. Russell Ashley J. King Helena C. Bates Natasha V. Almeida Richard C. Greenwood Luke Daly Katherine H. Joy Jim Rowe Tobias Salge Caroline L. Smith P. Grindrod S. Boazman L. Bond V. Bond C. Casey Z. Dickeson G. Ensor S. Farrelly P. Godfrey L. J. Hallis M. B. Ihász D. Kirk L. Jackson M. R. Lee B. Mayne S. McMullan A. Mounsey S. E. Mounsey S. Mounsey S. Motaghian S. Naqvi Á. O'Brien A. Pickersgill D. Skilton I. Spencer N. R. Stephen F. Suttle M. D. Suttle R. Tartese C. Weir Cathryn Wilcock Hannah Wilcock Rob Wilcock 《Meteoritics & planetary science》2024,59(5):973-987
The Winchcombe meteorite fell on February 28, 2021 and was the first recovered meteorite fall in the UK for 30 years, and the first UK carbonaceous chondrite. The meteorite was widely observed by meteor camera networks, doorbell cameras, and eyewitnesses, and 213.5 g (around 35% of the final recovered mass) was collected quickly—within 12 h—of its fall. It, therefore, represents an opportunity to study very pristine extra-terrestrial material and requires appropriate careful curation. The meteorite fell in a narrow (600 m across) strewn field ~8.5 km long and oriented approximately east–west, with the largest single fragment at the farthest (east) end in the town of Winchcombe, Gloucestershire. Of the total known mass of 602 g, around 525 g is curated at the Natural History Museum, London. A sample analysis plan was devised within a month of the fall to enable scientists in the UK and beyond to quickly access and analyze fresh material. The sample is stored long term in a nitrogen atmosphere glove box. Preliminary macroscopic and electron microscopic examinations show it to be a CM2 chondrite, and despite an early search, no fragile minerals, such as halite, sulfur, etc., were observed. 相似文献
394.
Silicic recharge of multiple rhyolite magmas by basaltic intrusion during the 22.6 ka Okareka Eruption Episode, New Zealand 总被引:1,自引:0,他引:1
Phil Shane Ian A. Nairn Victoria C. Smith Miles Darragh Kate Beggs Jim W. Cole 《Lithos》2008,103(3-4):527-549
Deposits of the 22.6 ka Okareka Eruption Episode from Tarawera Volcanic Complex record the sequential and simultaneous eruption of three discrete rhyolite magmas following a silicic recharge event related to basaltic intrusion. The episode started with basaltic eruption ( 0.01 km3 magma), and rapidly changed to a plinian eruption involving a moderate temperature (750 °C), cummingtonite-bearing rhyolite magma (T1) with a volume of 0.3 km3. Hybrid basalt/rhyolite clasts demonstrate direct basaltic intrusion that helped trigger the eruption. Crystals, shards and lapilli of two other rhyolite magmas then joined the eruption sequence. They comprise a cooler (720 °C) crystal-rich biotite–hornblende rhyolite magma (T2) ( 0.3 km3), and a hotter (780 °C), crystal-poor, pyroxene–hornblende rhyolite magma (T3) ( 4.5 km3). All mid to late-stage ash units contain various mixtures of T1, T2 and T3 components with a general increase in abundance of T3 and rapid decline of T1 with time. About 4 km3 of T3 magma was extruded as lavas at the end of the episode. Contrasts in melt composition, crystal and volatile contents, and temperatures influenced viscosity and miscibility, and thus limited pre-eruption mixing of the rhyolite magmas. The eruption sequence and the restricted direct basaltic intrusion into only one magma (T1) is consistent with the rhyolites occupying separate melt pods within a large crystal-mush zone. Melt–crystal equilibria and volatile contents in melt inclusions indicate temporary magma storage depths of < 8 km. Each of the magmas display quartz crystals containing melt inclusions that are compositionally highly evolved relative to the accompanying matrix glass, and thus point to a stage of more complete crystallisation. The matrix glass, enriched in Sr and Ti, represents a re-melting event of underlying the crystal pile induced by basaltic intrusion, presumably part of the same event that erupted scoria at the start of the eruption. This recharge rhyolite melt percolated upward and hybridised with the resident melts in each of the three magma pods. The Okareka episode rhyolites contrast with other well-documented rhyolites that are either continuously or discontinuously zoned, or have been homogenised during re-activation to a uniform composition. Rapid basalt dike intrusion to shallow levels appears to have (prematurely?) triggered the Okareka rhyolites into eruption, so that their early ponding in separate melt pods has been recorded before it could be masked by mixing or stratification had amalgamation into a larger body occurred. 相似文献
395.
Appourchaux Thierry Andersen Bo N. Fröhlich Claus Jiménez Antonio Telljohann Udo Wehrli Christoph 《Solar physics》1997,170(1):27-41
The Luminosity Oscillations Imager (LOI) is a part of the VIRGO instrument aboard the Solar and Heliospheric Observatory (SOHO). The scientific objective of the LOI experiment is to identify and characterize pressure and internal gravity oscillations of the Sun by observing the radiance variations. The LOI is a low-resolution imager with 12 pixels, for the measurement of the radiance distribution over the solar disk at 500 nm. The low resolution capability of the instrument allows the identification of individual azimuthal orders for l = 0 to 7, without suffering the mixing that affects integrated solar disk instruments. The performance, calibrations and instrumental effects of the LOI are described together with the procedures for extracting the solar p modes. 相似文献
396.
T. Toutain T. Appourchaux F. Baudin C. Fröhlich A. Gabriel P. Scherrer B. N. Andersen R. Bogart R. Bush W. Finsterle R. A. García G. Grec C. J. Henney J. T. Hoeksema A. Jiménez A. Kosovichev T. Roca Cortés S. Turck-Chièze R. Ulrich C. Wehrli 《Solar physics》1997,175(2):311-328
The three helioseismology instruments aboard SOHO observe solar p modes in velocity (GOLF and MDI) and in intensity (VIRGO
and MDI). Time series of two months duration are compared and confirm that the instruments indeed observe the same Sun to
a high degree of precision. Power spectra of 108 days are compared showing systematic differences between mode frequencies
measured in intensity and in velocity. Data coverage exceeds 97% for all the instruments during this interval. The weighted
mean differences (V-I) are −0.1 μHz for l=0, and −0.16 μHz for l=1. The source of this systematic difference may be due to
an asymmetry effect that is stronger for modes seen in intensity. Wavelet analysis is also used to compare the shape of the
forcing functions. In these data sets nearly all of the variations in mode amplitude are of solar origin. Some implications
for structure inversions are discussed. 相似文献
397.
398.
Richard Dawson Jim Hall Paul Sayers Paul Bates Corina Rosu 《Stochastic Environmental Research and Risk Assessment (SERRA)》2005,19(6):388-402
A dike system of moderate size has a large number of potential system states, and the loading imposed on the system is inherently
random. If the system should fail, in one of its many potential failure modes, the topography of UK floodplains is usually
such that hydrodynamic modelling of flood inundation is required to generate realistic estimates of flood depth and hence
damage. To do so for all possible failure states may require 1,000s of computationally expensive inundation simulations. A
risk-based sampling technique is proposed in order to reduce the computational resources required to estimate flood risk.
The approach is novel in that the loading and dike system states (obtained using a simplified reliability analysis) are sampled
according to the contribution that a given region of the space of basic variables makes to risk. The methodology is demonstrated
in a strategic flood risk assessment for the city of Burton-upon-Trent in the UK. 5,000 inundation model simulations were
run although it was shown that the flood risk estimate converged adequately after approximately half this number. The case
study demonstrates that, amongst other factors, risk is a complex function of loadings, dike resistance, floodplain topography
and the spatial distribution of floodplain assets. The application of this approach allows flood risk managers to obtain an
improved understanding of the flooding system, its vulnerabilities and the most efficient means of allocating resource to
improve performance. It may also be used to test how the system may respond to future external perturbations. 相似文献
399.
The water balance of four different rainforest types in the Wet Tropics region of north Queensland is inferred from measurements of canopy hydrological components undertaken for periods between 391 to 657 days. These measurements of rainfall, cloud interception, stem-flow, throughfall, canopy interception and transpiration have revealed considerable differences in the canopy water balance of different locations as a result of forest structural differences, altitude, exposure and climate. Cloud interception is a significant extra input of water to forests at high altitude sites (>1000 m) and varies between 7 and 29% of the total water input. At coastal and lower montane rainforests annual total evaporation is consistently around 50% of the total water input, but in upper montane cloud forest this drops dramatically to only 13% of the water input. At all sites actual evaporation is greater than potential evaporation for most of the year and on an annual basis exceeds potential by between 2 and 53%. The source of this additional energy is uncertain, but is likely to come from advection. Annual interception at all the rainforest sites was greater than annual transpiration, with transpiration dominating in the dry season and interception dominating in the wet season. All of the rainforests have a large annual net water balance to sustain runoff and recharge. Towards the end of the dry season runoff and recharge can cease in coastal lowland and lower mountain forests and they may have to draw on soil moisture and/or ground water at this time. In contrast, upper montane cloud forests have a positive net water balance throughout the year and are therefore an important source of dry season river flows. Furthermore, their exceptionally large annual runoff (∼6500 mm year−1) is a major source of downstream water. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
400.
Teleconnections between Andean and New Zealand glaciers 总被引:1,自引:1,他引:0
Retreat and advance of glaciers in the Southern Alps of New Zealand have occurred over two distinct 20-yr climate periods (1954–1974) and (1974–1994). Changes in tropical and southern Andean glaciers are compared over these same periods. Behaviour of glaciers in the tropical Andes are out of phase with the Southern Alps glaciers, but some glaciers in Patagonia appear to be in phase. Southern Hemisphere atmospheric circulation using 700 hPa geopotential height anomalies and sea surface temperature patterns are examined for these periods. Glacier response on inter-decadal timescales is linked with distinctive shifts in atmospheric circulation patterns around the Southern Hemisphere. Retreat (advance) of glaciers in the Southern Alps and southern Andean glacier and advance (retreat) of glaciers in the tropical Andes are all associated with weaker (stronger) westerlies, blocking events in the South-east Pacific, negative (positive) geopotential height anomalies over Southern Africa and higher latitudes of the Southern Hemisphere. These glacier changes are also linked with the negative (positive) phase of the Inter-decadal Pacific Oscillation, a higher frequency of La Niña (El Niño) events, and warm (cool) sea surface temperatures in the New Zealand region and cool (warm) sea surface temperatures in the equatorial eastern region of the Pacific Ocean off the coast of Peru. 相似文献