全文获取类型
收费全文 | 733篇 |
免费 | 82篇 |
国内免费 | 95篇 |
专业分类
测绘学 | 13篇 |
大气科学 | 116篇 |
地球物理 | 126篇 |
地质学 | 341篇 |
海洋学 | 113篇 |
天文学 | 35篇 |
综合类 | 22篇 |
自然地理 | 144篇 |
出版年
2023年 | 3篇 |
2022年 | 6篇 |
2021年 | 17篇 |
2020年 | 15篇 |
2019年 | 30篇 |
2018年 | 14篇 |
2017年 | 28篇 |
2016年 | 21篇 |
2015年 | 27篇 |
2014年 | 30篇 |
2013年 | 39篇 |
2012年 | 21篇 |
2011年 | 38篇 |
2010年 | 43篇 |
2009年 | 54篇 |
2008年 | 50篇 |
2007年 | 57篇 |
2006年 | 36篇 |
2005年 | 54篇 |
2004年 | 43篇 |
2003年 | 30篇 |
2002年 | 35篇 |
2001年 | 37篇 |
2000年 | 21篇 |
1999年 | 23篇 |
1998年 | 23篇 |
1997年 | 11篇 |
1996年 | 13篇 |
1995年 | 15篇 |
1994年 | 18篇 |
1993年 | 8篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1990年 | 7篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1982年 | 7篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1977年 | 1篇 |
排序方式: 共有910条查询结果,搜索用时 140 毫秒
101.
S.D. Salman 《Estuarine, Coastal and Shelf Science》1982,15(3):241-253
Larvae of five species of sessile barnacles were found to be common within 4 miles of Port Erin, Isle of Man. These are Balanus balanoides, B. crenatus, B. balanus, B. hameri and Verucca stroemia. Larvae of other recorded species were very rare or absent.The major larval release of all the common species occurred in late winter and spring, but V. stroemia continued to breed throughout most of the year, and there was some evidence of autumn breeding of B. crenatus on a very small scale. The major release of nauplii by most of these species occurred at the time of the spring diatom outburst.The larval life of each of the four species of Balanus is estimated to last 3–5 weeks, that of V. stroemia 7–8 weeks.Some observations suggested that the larval release of B. balanoides may be stimulated by spring tides, but other observations seemed to contradict this. Larval release may be inhibited by turbulence. 相似文献
102.
Charles Harris 《第四纪科学杂志》1991,6(1):67-77
The nature and origin of glacial sediments at Wylfa Head are described, and their significance with regard to sedimentary environments during Late Devensian deglaciation of the Irish Sea Basin is discussed. Recent models of deglaciation under glaciomarine conditions are challenged. The Quaternary sequence at Wylfa consists of eroded and glaciotectonically deformed bedrock, locally derived lodgement till, calcareous silt-rich lodgement till containing northern erratics, discontinuous units of orange-brown silty sand of possible aeolian origin, and grey laminated freshwater silts filling a small kettle hole. The till units thicken to the south where the surface is drumlinised. It is concluded that the landforms and deposits result from a warm-based Irish Sea glacier, which moved towards the southwest. Spatial variation in basal water pressure resulted from localised drainage through zones of more heavily jointed bedrock. Rapid glacial erosion occurred in areas where subglacial water pressure was relatively high, while deposition of the resulting basal sediment took place where water pressures were reduced. The glacier also carried basal calcareous silty till onshore, which was deposited by lodgement processes. None of the deposits at Wylfa are interpreted as glaciomarine in origin, and there is no evidence at this site for an isostatically induced marine transgression prior to deglaciation. 相似文献
103.
王清华 《极地研究(英文版)》2003,14(1)
1 IntroductionFromitsoriginalformulationin 1 990 ,theInternationalTrans AntarcticScientificExpedition (ITASE)hashadasitsprimaryaimthecollectionandinterpretationofacon tinental widearrayofenvironmentalparametersassembledthroughthecoordinatedeffortsofscientistsfromseveralnations(Mayewskietal.1 996) .AsaconsequenceITASEhasbeenfocusedtoaddresstwokeyscientificobjectives:1 )Todeterminethespatialvariabil ityofAntarcticclimate (eg.accumulation,airtemperature,atmosphericcirculation)overthelast2… 相似文献
104.
105.
106.
Medieval Warming, Little Ice Age, and European impact on the environment during the last millennium in the lower Hudson Valley, New York, USA 总被引:1,自引:0,他引:1
Dee Cabaniss Pederson Dorothy M. Peteet Dorothy Kurdyla Tom Guilderson 《Quaternary Research》2005,63(3):363-249
Establishing natural climate variability becomes particularly important in large urban areas in anticipation of droughts. We present a well-dated bi-decadal record of vegetation, climate, land use, and fire frequency from a tidal marsh in the Hudson River Estuary. The classic Medieval Warm Period is evident through striking increases in charcoal and Pinus dominance from 800–1300 A.D., paralleling paleorecords southward along the Atlantic seaboard. Higher inputs of inorganic sediment during this interval suggest increased watershed erosion during drought conditions. The presence of the Little Ice Age ensues with increases in Picea and Tsuga, coupled with increasing organic percentages due to cooler, moister conditions. European impact is manifested by a decline in arboreal pollen due to land clearance, increased weedy plant cover (i.e., Ambrosia, Plantago, and Rumex), and an increase in inorganic particles to the watershed. 相似文献
107.
Thorsten?MauritsenEmail author Gunilla?Svensson Branko?Grisogono 《Boundary-Layer Meteorology》2005,117(2):259-273
We investigate the flow over Arctic leads using a mesoscale numerical model, typical of both summer and winter, under idealised
conditions. We find that Arctic leads may be the source of standing atmospheric internal gravity waves during both seasons.
The summertime wave may be compared with the wave generated by a small ridge, though with the phase reversed. The mechanism
for exciting the wave is found to be the internal boundary layer developing due to horizontal variations in surface temperature
and roughness length. During the more exploratory wintertime simulations, with substantial temperature difference between
the lead and the ice surface, we find that secondary circulations and intermittent wave-breaking may occur. The effects of
the lead appear far downstream. 相似文献
108.
109.
In a sequence of glacigenic sediments at Aberdaron, Foraminifera were obtained from samples located specifically in order to differentiate between opposing models of depositional environment. All the diamict samples yielded remarkably uniform assemblages, with similar numbers of benthic specimens and benthic species per unit weight of sediment, similar planktic : benthic ratios, and similar ratios of clearly allochthonous to possibly autochthonous elements. This is precisely as predicted by the terrestrial model of sedimentation, where all of the sediments are interpreted as being derived from the melting of glacier ice rich in marine debris entrained during passage along the Irish Sea Basin. The results lend no support to a glacial marine model, since no faunal responses to increasingly distal sedimentary environments are observed. However, the fauna is dominated by the Foraminifera Elphidium excavatum (Terquem) forma clavata Cushman, which is commonly assumed to indicate glacial marine conditions. The modern distribution of similar assemblages suggests that it is just as likely to represent the cold, reduced salinity conditions that would have prevailed in the northern Irish Sea Basin for much of the Quaternary. 相似文献
110.
A coarse-grid (resolution of order 7 km) model of the west coast of Britain is used to examine the sensitivity of computed storm-surge elevations and currents to a range of open-boundary conditions. The storm-surge period 1 to 26 March 1994 is used for this comparison, as it is a time of significant wind activity. Also current measurements in the North Channel of the Irish Sea together with coastal elevation measurements are available for model validation. Elevations and currents previously computed with a coarse-grid shelf-wide model can also be incorporated into the open-boundary condition to examine the influence of far-field effects. Initial model calculations with no far-field input show the importance of including shelf-wide effects from either the external shelf model, or by using observations from coastal gauges interpolated along the open boundary of the west-coast model. Provided the west-coast models open boundary is taken sufficiently far away from the region of interest, in this case the Irish Sea, then either a radiation condition or an elevation-specified condition is appropriate provided far-field effects are taken into account. If these are not included, then neither boundary condition is successful. For the radiation condition it is necessary to include both elevations and currents from a far-field model in order to reproduce the surge. In the case of an elevation-specified boundary condition far-field effects can be incorporated in hindcast calculations by including observed sea-level changes. In a storm-surge prediction calculation the radiation condition with a far-field model is required. Calculations show that computed elevations are spatially more coherent than currents, with flows through the western Irish Sea showing the greatest sensitivity to open-boundary formulation during storm events.Responsible Editor: Phil Dyke 相似文献