全文获取类型
收费全文 | 77篇 |
免费 | 5篇 |
国内免费 | 5篇 |
专业分类
大气科学 | 11篇 |
地球物理 | 6篇 |
地质学 | 25篇 |
海洋学 | 33篇 |
天文学 | 5篇 |
自然地理 | 7篇 |
出版年
2023年 | 2篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 2篇 |
2016年 | 2篇 |
2015年 | 3篇 |
2014年 | 2篇 |
2013年 | 5篇 |
2012年 | 3篇 |
2010年 | 2篇 |
2009年 | 3篇 |
2008年 | 4篇 |
2007年 | 2篇 |
2006年 | 5篇 |
2005年 | 4篇 |
2004年 | 4篇 |
2003年 | 1篇 |
2002年 | 5篇 |
2001年 | 4篇 |
2000年 | 1篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1982年 | 2篇 |
1980年 | 3篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1974年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有87条查询结果,搜索用时 15 毫秒
51.
Observations show that the summer precipitation over East China often goes through decadal variations of opposite sign over North China and the Yangtze River valley (YRV), such as the “southern flood and northern drought” pattern that occurred during the late 1970s–1990s. In this study it is shown that a modulation of the Pacific Decadal Oscillation (PDO) on the summer precipitation pattern over East China during the last century is partly responsible for this characteristic precipitation pattern. During positive PDO phases, the warm winter sea surface temperatures (SSTs) in the eastern subtropical Pacific along the western coast of North American propagate to the tropics in the following summer due to weakened oceanic meridional circulation and the existence of a coupled wind–evaporation–SST feedback mechanism, resulting in a warming in the eastern tropical Pacific Ocean (5°N–20°N, 160°W–120°W) in summer. This in turn causes a zonal anomalous circulation over the subtropical–tropical Pacific Ocean that induces a strengthened western Pacific subtropical high (WPSH) and thus more moisture over the YRV region. The end result of these events is that the summer precipitation is increased over the YRV region while it is decreased over North China. The suggested mechanism is found both in the observations and in a 600-years fully coupled pre-industrial multi-century control simulations with Bergen Climate Model. The intensification of the WPSH due to the warming in the eastern tropical Pacific Ocean was also examined in idealized SSTA-forced AGCM experiments. 相似文献
52.
AbstractThe Salar de Atacama is located in the most arid desert in the world. Despite its extreme conditions, it has many ecosystems of high ecological value. The Soncor ecosystem, a sequence of lagoons, is the most important environment of the region as it acts as the centre for the breeding of the Andean Flamingo. This salt flat also contains significant mining deposits and is an important water source for the region. Freshwater and brine—enriched in lithium and potassium—are being pumped from the aquifers near to the Soncor ecosystem, which has so far not been greatly affected by this groundwater extraction. However, there is a potential risk that future anthropogenic effects may disturb this fragile environment. The objective of this study is to determine the origin of the water sources of the Soncor ecosystem so as to adequately manage its water resources. Three hypotheses previously proposed in the technical literature were investigated in order to determine proactive actions to protect this fragile ecosystem. The study utilized classic hydrogeological techniques, such as the construction of stratigraphic profiles, piezometric maps and stream gauging, combined with less-common isotopic techniques, such as the 87Sr/86Sr ratio. The results confirmed the hypothesis that the origins of the water sources are associated with groundwater inputs coming from the east side of the salt flat, in the north of the basin.Editor Z.W. Kundzewicz; Associate editor M. AcremanCitation Ortiz, C., Aravena, R., Briones, E., Suárez, F., Tore, C., and Muñoz, J.F., 2014. Sources of surface water for the Soncor ecosystem, Salar de Atacama basin, northern Chile. Hydrological Sciences Journal, 59 (2), 336–350. 相似文献
53.
Jan S. Laberg Kiichiro Kawamura Hilde Amundsen Nicole Baeten Matthias Forwick Tom A. Rydningen Tore O. Vorren 《Geo-Marine Letters》2014,34(1):51-58
Swath-bathymetry data and 2D multichannel seismics reveal for the first time an up to ~60 km wide amphitheater-shaped slide scar on the eastern flank of the Jan Mayen Ridge, a micro-continent in the Norwegian–Greenland Sea. The scar opens southeastward where it continues as a narrower, topographically controlled translational area. It includes secondary scars, as well as channels and escarpments. Based on the identification of secondary scars, the slide is classified as a slide complex and the total volume of missing sediments was estimated at ~60 km3. From the overall shape of the scar, the upslope widening from a bottleneck- or channel-like bypass-area, the failure is inferred to have had a retrogressive development. The absence of ridges, slabs and sediment blocks indicates that the failed sediments have been evacuated entirely. The smaller channels were formed from single or repetitive smaller flows post-dating the large failure events. 相似文献
54.
55.
The day to night ratio in ionospheric radio wave absorption has been studied for College, Alaska using a narrow beam riometer array and computer assisted programming of the data. For the period of 6 November 1967 to 17 April 1968 no significant departure from a ratio of unity was found. 相似文献
56.
This paper describes the development of a regressive-to-transgressive shoreline wedge within the Middle Jurassic Tarbert Formation in the Oseberg South area (northern North Sea), as interpreted from core and log data from more than hundred wells. The wedge is described in terms of four facies associations (FA1–FA4). The lower, regressive portion of the wedge (FA1–FA2) contains both coarsening upward wave/storm-dominated shoreline deposits as well as coal-bearing paralic deposits, and was deposited during ascending regression. The upper, transgressive portion of the wedge (FA3–FA4) is characterised by wave-dominated estuarine deposits, exhibiting an upward change from inner to central to outer estuarine deposits. In contrast to some earlier studies, it is argued that this part was deposited during accretionary transgression. The present study documents an estuarine system that developed without any preceding fall of relative sea level and valley incision. It is argued that differential fault-induced subsidence created a broad gentle sag wherein one or several estuarine systems developed as the depositional system became transgressive. The subtle fault-induced subsidence is related to the tectonic evolution in the North Sea Basin. 相似文献
57.
Tore Prestvik Steven Goldberg Haraldur Karlsson Karl Grnvold 《Earth and Planetary Science Letters》2001,190(3-4):211-220
The currently active off-rift central volcano Öræfajökull in south-east Iceland sits unconformably on much older (10–12 Ma) and eroded crust. The composition of recent volcanics ranges from basalt to rhyolite, but the series is more sodic alkaline than the common rift zone tholeiitic suites. In this study we present Sr, Nd, Pb and O isotopic data for a suite of Öræfajökull samples. The complete suite shows typical mantle values for oxygen isotopes. The 87Sr/86Sr ratios (average of 15 SAMPLES=0.703702) of the modern Öræfajökull rocks (basalts as well as rhyolites) are much higher than observed so far for any other Icelandic rocks. The 143Nd/144Nd ratios (average=0.512947; n=15) are lower than for rift rocks, but similar to rocks of the off-rift Snæfellsnes volcanic zone. Furthermore, the Öræfajökull rocks are enriched in the 207Pb/204Pb and 208Pb/204Pb isotope ratios compared to Icelandic rift basalts. The enriched nature of the suite indicates that Öræfajökull samples a source component that has characteristics common with EM2 type mantle. Furthermore, it is concluded that the silicic rocks of Öræfajökull formed by fractional crystallization from mafic melts rather than by partial melting of older crust. 相似文献
58.
Lithologic, paleontologic, and chronostratigraphic investigation of 13 gravity cores indicates the following environmental evolution: a high- (mid-) arctic period with a slight influx of ice-rafted debris occurred during the early middle Weichselian followed by a mid- (high-) arctic environment with a high influx of iceberg-rafted debris during the remainder of the middle Weichselian. The continental ice sheet probably did not extend beyond the inner shelf during middle Weichselian and a minimum relative sea level was ca. −120 m. A low-arctic environment occurred during (parts of) the late Weichselian with an initial winnowing of the sediments. The Norwegian Current entered the area during this substage. A high- (mid-) boreal environment occurred during the Holocene with high winnowing activity in the early Holocene. Winnowing is still very active on the shallower banks in contrast to the deeper banks where it has ceased. Relatively high percentages of carbonate in the form of biogenic skeletal remains occur in the Holocene sediments. 相似文献
59.
Tore Torske 《International Journal of Earth Sciences》1982,71(1):104-119
An isolated synclinorium, comprising the up to 5 km thick Ullensvang Group of metavolcanic and metasedimentary rocks, is surrounded by granitoid plutons and has no recognizable older basement. From an earlier interpretation based on regional data this area is inferred to be part of a Proterozoic, cordilleran-type volcanic-plutonic belt. Major structures in the synclinorium are interpreted to have evolved as follows: 1) Early folds were produced by regional compression; 2) within a part of the synclinorium, such folds were tightened and reoriented during a subsequent deformation phase caused by forceful emplacement of the Kvinnherad batholith, flanking the synclinorium to the southwest; 3) this deformation was accompanied by thrust faulting towards the northeast, away from the batholith; 4) forceful emplacement of plutons belonging to the Eidfjord-Kinsarvik batholith, on the northeastern flank of the synclinorium, produced southwest-vergent overfolding of the earlier structures in the synclinorium. In addition, local deformation around a pluton intruding the northern part of the synclinorium near Utne produced areally restricted deformation structures, approximately corresponding in time with the second deformation event (2) above. Structures in plutonics rocks of the batholiths are interpreted in terms of an emplacement model involving distension diapirism. The deformation zones associated with diapiric plutons in this area appear to be more similar to some of those reported from Archaean greenstone belts than to those found in volcanic-plutonic belts of younger cordilleran-type orogens. 相似文献
60.
Tore P?sse 《Mathematical Geology》1990,22(7):803-824
A nonuniform glacio-isostatic uplift results in differential uplift for different parts of a lake. If the lake outlet is situated in the area with the greatest rate of uplift, then the lake will be continuously transgressed. Ancient lake levels can be estimated by dating transgressed peat at different depths in such a lake. Two lakes in southwestern Sweden have been investigated by this method and the course of glacio-isostatic uplift has been determined empirically. The uplift can be expressed by an exponential function through the following formula
相似文献 |