全文获取类型
收费全文 | 157篇 |
免费 | 7篇 |
国内免费 | 1篇 |
专业分类
大气科学 | 26篇 |
地球物理 | 35篇 |
地质学 | 65篇 |
海洋学 | 9篇 |
天文学 | 13篇 |
综合类 | 1篇 |
自然地理 | 16篇 |
出版年
2022年 | 1篇 |
2021年 | 6篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 9篇 |
2017年 | 5篇 |
2016年 | 9篇 |
2015年 | 2篇 |
2014年 | 2篇 |
2013年 | 14篇 |
2012年 | 12篇 |
2011年 | 11篇 |
2010年 | 6篇 |
2009年 | 10篇 |
2008年 | 7篇 |
2007年 | 7篇 |
2006年 | 3篇 |
2005年 | 5篇 |
2004年 | 10篇 |
2003年 | 7篇 |
2002年 | 2篇 |
2000年 | 1篇 |
1999年 | 5篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1974年 | 3篇 |
1973年 | 3篇 |
排序方式: 共有165条查询结果,搜索用时 234 毫秒
141.
Kirsten Simonsen M. Sc. 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(1):26-35
Simonsen, Kirsten, 1973: Studies of household activity patterns and urban structure. Geografisk Tidsskrift 73: 26–35. København, juni 1, 1974. This Paper focuses upon the daily activity patterns of individuals and households. It gives a survey of the relevant literature and discusses the possible use of activity studies. Furthermore, it treats the interrelationship between activity patterns and environment and illustrates this by a case study from a Danish provincial town. 相似文献
142.
143.
144.
145.
Jessica L. Blois John W. Williams Eric C. Grimm Stephen T. Jackson Russell W. Graham 《Quaternary Science Reviews》2011,30(15-16):1926-1939
Mapping past vegetation dynamics from heterogeneous databases of fossil-pollen records must face the challenge of temporal uncertainty. The growing collection of densely sampled fossil-pollen records with accurate and precise chronologies allows us to develop new methods to assess and reduce this uncertainty. Here, we test our methods in the context of vegetation changes in eastern North America during the abrupt climate changes of the last deglaciation. We use the network of fossil-pollen records in the Neotoma Paleoecology Database (www.neotomadb.org) and data contributed by individual investigators. Because many of these records were collected decades before the current generation of 14C and age-model technologies, we first developed a framework to assess the overall reliability of 14C chronologies by systematically evaluating individual 14C ages and associated chronologies. We developed a qualitative ranking scheme for individual 14C ages that combines information about their accuracy and precision. ‘Benchmark’ pollen records were defined to have at least one 14C age with an accuracy within 250 years and a precision less than 500 years that is within 1000 years of the time interval of interest, and at least five pollen samples per 1000 years across this time period. Only 22 of >350 late-Pleistocene pollen cores in eastern North America met the benchmark criteria.We then used Bayesian change-point analysis to identify widespread ecological events (Picea decline, Quercus rise, and Alnus decline), and interpolated the ages of these events from the benchmark sites to non-benchmark sites. Leave-one-out cross-validation analyses with the benchmark sites indicated that the spatial error associated with interpolation was less for inverse distance-weighting (IDW) than thin-plate splines (TPS) and was about 500 years for the three biotic events. By comparison, the difference between the original ages of events at poorly constrained sites and the biostratigraphic ages interpolated from the benchmark sites was close to 1000 years, suggesting that the use of biostratigraphic ages can significantly improve the age models for poorly constrained sites. Overall, these analyses suggest that the temporal resolution of multi-site syntheses of late-Pleistocene fossil-pollen data in eastern North America is about 500 years, a resolution that allows analysis of ecological responses to millennial-scale climate change during the last deglaciation. 相似文献
146.
Differences in preferential flow with antecedent moisture conditions and soil texture: Implications for subsurface P transport 总被引:2,自引:0,他引:2
Preferential flowpaths transport phosphorus (P) to agricultural tile drains. However, if and to what extent this may vary with soil texture, moisture conditions, and P placement is poorly understood. This study investigated (a) interactions between soil texture, antecedent moisture conditions, and the relative contributions of matrix and preferential flow and (b) associated P distributions through the soil profile when fertilizers were applied to the surface or subsurface. Brilliant blue dye was used to stain subsurface flowpaths in clay and silt loam plots during simulated rainfall events under wet and dry conditions. Fertilizer P was applied to the surface or via subsurface placement to plots of different soil texture and moisture condition. Photographs of dye stains were analysed to classify the flow patterns as matrix dominated or macropore dominated, and soils within plots were analysed for their water‐extractable P (WEP) content. Preferential flow occurred under all soil texture and moisture conditions. Dye penetrated deeper into clay soils via macropores and had lower interaction with the soil matrix, compared with silt loam soil. Moisture conditions influenced preferential flowpaths in clay, with dry clay having deeper infiltration (92 ± 7.6 cm) and less dye–matrix interaction than wet clay (77 ± 4.7 cm). Depth of staining did not differ between wet (56 ± 7.2 cm) and dry (50 ± 6.6 cm) silt loam, nor did dominant flowpaths. WEP distribution in the top 10 cm of the soil profile differed with fertilizer placement, but no differences in soil WEP were observed at depth. These results demonstrate that large rainfall events following drought conditions in clay soil may be prone to rapid P transport to tile drains due to increased preferential flow, whereas flow in silt loams is less affected by antecedent moisture. Subsurface placement of fertilizer may minimize the risk of subsurface P transport, particularily in clay. 相似文献
147.
Rosati P. Basa S. Blain A. W. Bozzo E. Branchesi M. Christensen L. Ferrara A. Gomboc A. O’Brien P. T. Osborne J. P. Rossi A. Schüssler F. Spurio M. Stergioulas N. Stratta G. Amati L. Casewell S. Ciolfi R. Ghirlanda G. Grimm S. Guetta D. Harms J. Le Floc’h E. Longo F. Maggiore M. Mereghetti S. Oganesyan G. Salvaterra R. Tanvir N. R. Turriziani S. Vergani S. D. Balman S. Caruana J. Erkut M. H. Guidorzi G. Frontera F. Martin-Carrillo A. Paltani S. Porquet D. Sergijenko O. 《Experimental Astronomy》2021,52(3):407-437
Experimental Astronomy - The proposed THESEUS mission will vastly expand the capabilities to monitor the high-energy sky. It will specifically exploit large samples of gamma-ray bursts to probe the... 相似文献
148.
Martin Wessels Kirsten Mohaupt Reiner Kümmerlin Angela Lenhard 《Journal of Paleolimnology》1999,21(2):171-192
In Lake Constance, phosphorus concentrations and the seasonal development of phytoplankton communities in water samples from the pelagic zone were regularly recorded since the 1950's. Before the 1950's, there were occasional investigations of plankton communities since 1896. We compared these data with the sedimentary record in two sediment cores. Then, the eutrophication history of Lake Constance was inferred from diatoms. The record of biogenic silica in the cores is discussed with respect to diatom biomass increase.Diatom assemblages in the sediment cores precisely reflected the pelagic diatom development for the period 1971--1992. Both sediment cores and the water samples have a high interannual variability of diatom assemblages. Below a sediment depth of 27 cm (AD 1920), more than 50% of the diatoms were partly corroded, and we limited the reconstruction of trophic state changes to the interval of 1920--1993. Oligotrophic conditions of Lake Constance were indicated by the dominance of various Cyclotella taxa from 1920 to 1940. Since 1939/1940, increasing abundance of it Tabellaria fenestrata showed oligotrophic to mesotrophic conditions. Between 1953 and 1956, increasing Stephanodiscus hantzschii and disappearing Cyclotella indicated advanced eutrophication and total phosphorus values ranged between 8--10 mg m-3 during turnover in late winter. Further eutrophication was shown by disappearing T. fenestrata and increasing S. minutulus in 1963. Maximum TP concentrations of 87 mg m-3 occurred in 1979/80 and was accompanied by increasing abundances of Aulacoseira granulata. From 1986 to 1992, reoccurrence of Tabellaria fenestrata and Cyclotella indicate some recovery of Lake Constance.Biogenic silica and diatom abundances were similar among cores but indicate a 3--4 fold increase of diatom biomass only. This was far below the estimate of biomass increase from sedimentary pigment data (25 fold) and the estimate of phytoplankton data from the literature (70 fold). 相似文献
149.
Relative sea-level change at the time of, and since, the most recent great earthquake at the Cascadia subduction zone is estimated from intertidal sediments at three marshes on western Vancouver Island, British Columbia. We compare the elevation of the pre-earthquake surface, which is marked by a tsunami sand sheet, with the modern depositional elevation range of the sediment type upon which the sand was deposited. At a site south of the Nootka fault zone, which is the northern boundary of the subducting Juan de Fuca plate, tidal mud overlies the pre-earthquake marsh surface. The stratigraphy at this site indicates 0.2–1.6 m of coseismic submergence and 1.1 m of subsequent emergence. In contrast, two sites to the north lack obvious stratigraphic evidence for coseismic land-level change and record between 0.1 and 1.7 m of post-earthquake submergence. These results indicate a difference in tectonic environment across the Nootka fault zone and suggest that plate-boundary rupture during the last great Cascadia earthquake probably did not extend north of central Vancouver Island. 相似文献
150.