全文获取类型
收费全文 | 453篇 |
免费 | 13篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 7篇 |
大气科学 | 43篇 |
地球物理 | 21篇 |
地质学 | 273篇 |
海洋学 | 24篇 |
天文学 | 5篇 |
自然地理 | 95篇 |
出版年
2016年 | 2篇 |
2015年 | 3篇 |
2014年 | 8篇 |
2013年 | 26篇 |
2012年 | 7篇 |
2011年 | 14篇 |
2010年 | 10篇 |
2009年 | 17篇 |
2008年 | 12篇 |
2007年 | 15篇 |
2006年 | 10篇 |
2005年 | 21篇 |
2004年 | 15篇 |
2003年 | 14篇 |
2002年 | 5篇 |
2001年 | 6篇 |
2000年 | 10篇 |
1999年 | 11篇 |
1998年 | 17篇 |
1997年 | 35篇 |
1996年 | 26篇 |
1995年 | 12篇 |
1994年 | 20篇 |
1993年 | 8篇 |
1992年 | 7篇 |
1991年 | 16篇 |
1990年 | 20篇 |
1989年 | 10篇 |
1988年 | 12篇 |
1987年 | 10篇 |
1986年 | 9篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1971年 | 3篇 |
1970年 | 1篇 |
1968年 | 1篇 |
1967年 | 2篇 |
1966年 | 2篇 |
1963年 | 3篇 |
1962年 | 1篇 |
排序方式: 共有468条查询结果,搜索用时 15 毫秒
61.
KROON NORRIS KLAUS IAN T. ALEXANDER LEON PAUL BARDOT CHARLES E. BARKER JEAN-PIERRE BELLIER CHARLES D. BLOME LEON J. CLARKE JOCHEN ERBACHER KRISTINA L. FAUL MARY ANNE HOLMES BRIAN T. HUBER MIRIAM E. KATZ KENNETH G. MACLEOD SANDRA MARCA FRANCISA C. MARTINEZ-RUIZ ISAO MITA MUTSUMI NAKAI JAMES G. OGG DOROTHY K. PAK THOMAS K. PLETSCH JEAN M. SELF-TRIAL NICHOLAS J. SHACKLETON JAN SMIT WILLIAM USSLERIII DAVID K. WATKINS JOEN WIDMARK & PAUL A. WILSON 《Geology Today》1998,14(6):222-226
62.
63.
DAVID HUDDART MATTHEW R. BENNETT NEIL F. GLASSER 《Boreas: An International Journal of Quaternary Research》1999,28(2):253-273
Although eskers are frequently described glaciofluvial landforms, they are poorly understood. To assist with the interpretation of Pleistocene examples, modern analogue data are required. This paper documents the morphology, sedimentology and formation of a 650 m long esker system in front of the high-arctic glacier Vegbreen in Svalbard. The esker is located between the Neoglacial maximum and the present ice front and appears to have formed both as a supraglacial trough-fill and as a channel/conduit-fill along the suture formed by two confluent glacier lobes. A range of sedimentary facies is preserved within this ridge system providing evidence for braided rivers, ephemeral lakes, episodic flow regimes and sediment gravity flows. This case study provides an important analogue for glaciofluvial sedimentation between retreating ice lobes. 相似文献
64.
65.
The Paradigm pelagic food web organization in Antarctic waters is undergoing fundamental revision evidence that large fractions of material and energy flow through the microbial food web. because of the unique Antarctic ecosystem conditions, the microbial food web performs some roles that are fundamentally different from those in oligotrophic temperate and tropical waters: 1) during winter, bacterial production, at the expense of slow-turnover DOM (dissolved organic matter) from the previous summer, could be a significant factor in the survival of over wintering animal populations; 2) microbial regeneration of ammonium in nitrate-replete Antarctic waters may spare the reductants necessary for nitrate assimilation and thus enhance primary productivity of deep-mixed light-limited phytoplankton; and 3) the small diatoms and phytoflagellates which dominate the Antarctic pelagic primary production are apparently directly digestible by the metazoan herbivores, whereas cyanobacteria which dominate the primary productivity in lower latitude oligotrophic waters are not digestible by the metazoan herbivores. These roles performed by the microbial loop may, in part, explain why Antarctic waters, in contrast to the lower latitude oligotrophic waters, have high levels of tertiary productivity despite low primary productivity. 相似文献
66.
67.
PAUL C. BUCKLAND DAVID W. PERRY GÍSLI M. GISLASON REW J. DUGMORE 《Boreas: An International Journal of Quaternary Research》1986,15(2):173-184
The origins of the Icelandic biota are discussed with particular reference to recent work on Coleopteran (beetle) and Trichopteran (caddis fly) fossils from deposits which are earlier than the arrival of man (Landnám) in the country. The hypothesis of survival through Pleistocene glaciations in refugia is discounted in favour of immigration on ice floes during Late Glacial/Early Holocene deglaciation. Consideration of the nature of the insect fauna and the extent of Late Glacial ice sheets, with the evidence from ocean circulation patterns, suggests a source area in the fjords of south-west Norway. The model is applicable to the origins of the biota on all the North Atlantic islands, east of the Davis Strait. 相似文献
68.
DAVID LEE DUEWER 《地理学报(英文版)》1990,(4)
The Free-Wilson paradigm is an established and powerful tool for quantitatively relating activity withchemical structure.Current implementations of the paradigm,however,are flawed both conceptually andin execution.As part of an attempt to more fully realize the promise of the paradigm,it was necessaryto examine these limitations in detail.This report introduces a robust,theory-founded Free-Wilson implementation:stepwise principalcomponents regression analysis(SPCRA).SPCRA is computationally superior to previousimplementations but does not in itself correct their conceptual flaws.The development of SPCRA did,however,facilitate derivation of a simple and chemically significantinterpretation of the Free-Wilson structure-activity model.A number of statistical aspects of this modelcommonly misused in previous applications are discussed at length.These discussions provide criticalbackground for the development of an alternative implementation of the Free-Wilson paradigm. 相似文献
69.
70.
By HEATHER D. GRAVEN † BRITTON B. STEPHENS THOMAS P. GUILDERSON TERESA L. CAMPOS DAVID S. SCHIMEL J. ELLIOTT CAMPBELL RALPH F. KEELING 《Tellus. Series B, Chemical and physical meteorology》2009,61(3):536-546
Measurements of Δ14 C in atmospheric CO2 are an effective method of separating CO2 additions from fossil fuel and biospheric sources or sinks of CO2 . We illustrate this technique with vertical profiles of CO2 and Δ14 C analysed in whole air flask samples collected above Colorado, USA in May and July 2004. Comparison of lower tropospheric composition to cleaner air at higher altitudes (>5 km) revealed considerable additions from respiration in the morning in both urban and rural locations. Afternoon concentrations were mainly governed by fossil fuel emissions and boundary layer depth, also showing net biospheric CO2 uptake in some cases. We estimate local industrial CO2 :CO emission ratios using in situ measurements of CO concentration. Ratios are found to vary by 100% and average 57 mole CO2 :1 mole CO, higher than expected from emissions inventories. Uncertainty in CO2 from different sources was ±1.1 to ±4.1 ppm for addition or uptake of −4.6 to 55.8 ppm, limited by Δ14 C measurement precision and uncertainty in background Δ14 C and CO2 levels. 相似文献