全文获取类型
收费全文 | 112篇 |
免费 | 3篇 |
专业分类
大气科学 | 19篇 |
地球物理 | 4篇 |
地质学 | 66篇 |
海洋学 | 3篇 |
天文学 | 3篇 |
自然地理 | 20篇 |
出版年
2014年 | 3篇 |
2013年 | 6篇 |
2012年 | 4篇 |
2011年 | 2篇 |
2010年 | 3篇 |
2009年 | 8篇 |
2008年 | 1篇 |
2007年 | 6篇 |
2006年 | 4篇 |
2005年 | 5篇 |
2004年 | 3篇 |
2003年 | 1篇 |
2002年 | 5篇 |
2000年 | 4篇 |
1999年 | 1篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 4篇 |
1994年 | 7篇 |
1993年 | 5篇 |
1992年 | 8篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有115条查询结果,搜索用时 15 毫秒
61.
CHRISTIAN CHRISTIANSEN KELD CONRADSEN EMIL EMELYANOV EGIS TRIMONIS JAN HEINEMEIER NIELS RUD 《Boreas: An International Journal of Quaternary Research》1993,22(4):349-356
Detailed sedimentological, micropalaeontological, mineralogical and geochemical investigations as well as 14C datings were carried out on a core from the southern part of the Kattegat Sea. According to the micropalaeontological interpretations, sea level rose by approximately 20 m in the period c. 9610 BP to 8200 BP. The core therefore provides evidence of the hydrographical conditions in the southern Kattegat during the early Holocene transgression. In the sediment there is geochemical evidence of strong stratification in the water column possibly related to inflow of saline water around 9080 BP. After the sediments dated to 8200 BP there is a hiatus followed by very young (<300 BP?) sediments. It is suggested that this hiatus might be associated with the opening of the Danish Straits. 相似文献
62.
63.
CHRISTIAN WICHMANN MATTHIESSEN Ph. D. 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(1):98-101
Matthiessen, Christian Wichmann: Trends in the urbanization process. The Copenhagen case. Geografisk Tidsskrift 80: 98–101. Copenhagen, June 1980. Within the framework of the international comparative research project (Cost of Urban Growth) new trends in urban development have recently been observed. The object of this article is to discuss the trends and give impirical evidence on Danish data. 相似文献
64.
Abstract The uncertainties arising from the problem of identifying a representative model structure and model parameters in a conceptual rainfall-runoff model were investigated. A conceptual model, the HBV model, was applied to the mountainous Brugga basin (39.9 km”) in the Black Forest, southwestern Germany. In a first step, a Monte Carlo procedure with randomly generated parameter sets was used for calibration. For a ten-year calibration period, different parameter sets resulted in an equally good correspondence between observed and simulated runoff. A few parameters were well defined (i.e. best parameter values were within small ranges), but for most parameters good simulations were found with values varying over wide ranges. In a second step, model variants with different numbers of elevation and landuse zones and various runoff generation conceptualizations were tested. In some cases, representation of more spatial variability gave better simulations in terms of discharge. However, good results could be obtained with different and even unrealistic concepts. The computation of design floods and low flow predictions illustrated that the parameter uncertainty and the uncertainty of identifying a unique best model variant have implications for model predictions. The flow predictions varied considerably. The peak discharge of a flood with a probability of 0.01 year?1, for instance, varied from 40 to almost 60 mm day?1. It was concluded that model predictions, particularly in applied studies, should be given as ranges rather than as single values. 相似文献
65.
ANNE K. BRYSTING TOVE M. GABRIELSEN OVE SØRLIBRÅTEN ODDMUND YTREHORN CHRISTIAN BROCHMANN 《Polar research》1996,15(2):93-105
Several studies have demonstrated high levels of genetic (DNA), ecophysiological, ecological, and morphological variation within the species Purple Saxifrage, Saxifraga oppositifolia , in Svalbard. It has recently been proposed that S. oppositifolia is represented by two conspicuously different subspecies in this archipelago: ssp. reptans , a late-flowering, prostrate ecotype of snow-protected, damp habitats, and ssp. pulvinata , an early-flowering, cushion-like ecotype of dry, wind-exposed heaths and ridges. It has also been suggested that the subspecies may be differentiated at the tetraploid and diploid levels, respectively, which would promote reproductive isolation. These hypotheses are tested by examining variation in morphology, ecology, and pollen size and stainability in 150 plants of S. oppositifolia growing in 50 vegetation samples at four sites in the Kongsfjorden area. Although analyses of the various data sets demonstrated the large variation within the species, the material could not be separated into distinct groups. The morphological variation was continuous along local ecological gradients. The pollen grains were fully stainable and the pollen diameter data showed a unimodal distribution, suggesting that the plants analysed represent only one ploidal level. These results reject a hypothesis that the morphologically intermediate plants are hybrids between two taxa at different ploidal levels. Thus, the conspicuous variation in S. oppositifolia in Svalbard probably results from local, in situ ecoclinal differentiation. Although this variation clearly is without taxonomic significance, it is important in the broader context of arctic conservation biology and the potential impact of global warming on arctic vegetation. 相似文献
66.
Late Pleistocene and Holocene glacial history of James Ross Island, Antarctic Peninsula 总被引:2,自引:0,他引:2
ÓLAFUR INGÓLFSSON CHRISTIAN HJORT SVANTE BJÖRCK R. I. LEWIS SMITH 《Boreas: An International Journal of Quaternary Research》1992,21(3):209-222
Studies of Quaternary glacial stratigraphy and morphology around the Antarctic Peninsula have shown that James Ross Island in the western Weddell Sea probably has the best occurrences of stratigraphic sections with dateable material in the region. The stratigraphy includes sections with indefinite radiocarbon age, and three separate aminozones can be recognized. Except for indications of an early deglaciation around c . 10,000 BP, the field evidence from northern James Ross Island suggests a glacial readvance around 7000 BP. It is concluded that the readvance reflects the combined effects of eustatic sea level rise and Holocene warming, leading to increased precipitation and a positive mass balance. The most recent large-scale deglaciation in the area took place around 6000–5000 BP. This confirms the evidence from lake sediments and moss banks in other parts of the Antarctic Peninsula region, which shows that, in most cases, the initiation of organic deposition took place after c . 6000 BP. The literature on the Holocene glacial and environmental history of the region is reviewed in light of the new field evidence. 相似文献
67.
The Po Valley Fog Experiment 1989 总被引:13,自引:0,他引:13
S. FUZZI M. C. FACCHINI G. ORSI J. A. LIND W. WOBROCK M. KESSEL R. MASER W. JAESCHKE K. H. ENDERLE B. G. ARENDS A. BERNER I. SOLLY C. KRUISZ G. REISCHL S. PAHL U. KAMINSKI P. WINKLER J. A. OGREN^ K. J. NOONE• A. HALLBERG H. FIERLINGER-OBERLINNINGER H. PUXBAUM A. MARZORATI H.-C. HANSSON A. WIEDENSOHLER I. B. SVENNINGSSON B. G. MARTINSSON D. SCHELL H. W. GEORGII 《Tellus. Series B, Chemical and physical meteorology》1992,44(5):448-468
68.
The benthic foraminifer Quinqueloculina impressa Reuss, was buried in various types of sediment in order to assess its capability for producing sediment disturbances and thus, ichnofossils. Silts and silty-clays showed distinct burrows; fine sands did not. Two types of burrows were produced: fairly straight, vertical burrows from 4 cm below the water-sediment interface to within 1 cm of the sediment surface, and a horizontal and vertical maze-like burrow system in the top centimetre of the sediment. Individuals moving on the sediment surface also produced visible trails. When the sediments were dried the burrows were always destroyed; in some cases the surface trails were preserved. We propose that the vertical burrows are escape structures and that the horizontal and vertical maze-like structures are living burrows. Ichnofossils similar to the escape structures and surface structures have been described. Presence of these ichnofossils indicates a low energy sedimentary environment and a lack of macrofaunal bioturbation. The presence of escape structures may indicate a pulsatory pattern of sedimentation. 相似文献
69.
70.
CHRISTIAN HJORT SVEND FUNDER 《Boreas: An International Journal of Quaternary Research》1974,3(1):23-33
The subfossil occurrence of Mytilus edulis in central East Greenland has been C14 -dated to roughly between 8000 B.P. and 5500 B.P.; compared with other areas this is a short period. Its immigration coincides with the final deglaciation of the innermost fjords, and its disappearance is contemporaneous with an increase in cold-climate plants, as shown by pollen spectra. It is suggested that it immigrated from the Svalbard area rather than from southeast Greenland, and that the central East Greenland fjord zone forms an isolated oasis, where more southerly species like Mytilus and Chlamys islandica can or could live, even if this was not possible along the surrounding and more hostile outer coasts. The reason for the absence of Mytilus edalis from the region today is probably not the local climate. 相似文献