全文获取类型
收费全文 | 960篇 |
免费 | 38篇 |
国内免费 | 5篇 |
专业分类
测绘学 | 16篇 |
大气科学 | 68篇 |
地球物理 | 257篇 |
地质学 | 260篇 |
海洋学 | 85篇 |
天文学 | 189篇 |
综合类 | 12篇 |
自然地理 | 116篇 |
出版年
2021年 | 10篇 |
2020年 | 10篇 |
2019年 | 8篇 |
2018年 | 15篇 |
2017年 | 18篇 |
2016年 | 13篇 |
2015年 | 14篇 |
2014年 | 25篇 |
2013年 | 65篇 |
2012年 | 28篇 |
2011年 | 35篇 |
2010年 | 40篇 |
2009年 | 39篇 |
2008年 | 42篇 |
2007年 | 39篇 |
2006年 | 38篇 |
2005年 | 49篇 |
2004年 | 39篇 |
2003年 | 26篇 |
2002年 | 25篇 |
2001年 | 20篇 |
2000年 | 28篇 |
1999年 | 24篇 |
1998年 | 25篇 |
1997年 | 22篇 |
1996年 | 13篇 |
1995年 | 19篇 |
1994年 | 20篇 |
1993年 | 15篇 |
1992年 | 14篇 |
1991年 | 12篇 |
1990年 | 15篇 |
1989年 | 11篇 |
1988年 | 8篇 |
1987年 | 15篇 |
1986年 | 9篇 |
1985年 | 16篇 |
1984年 | 15篇 |
1983年 | 13篇 |
1982年 | 15篇 |
1981年 | 16篇 |
1980年 | 9篇 |
1979年 | 9篇 |
1978年 | 9篇 |
1977年 | 8篇 |
1976年 | 6篇 |
1975年 | 9篇 |
1974年 | 6篇 |
1973年 | 8篇 |
1972年 | 6篇 |
排序方式: 共有1003条查询结果,搜索用时 31 毫秒
111.
Here we present a crustal folding or buckling mechanism to explain the rootless 3–5 km high Alborz Mountains in northern Iran as well as 10 km of Late Miocene to recent subsidence in the south Caspian basin and 3–6 km of subsidence in the central Iranian basin in the context of the middle Miocene to recent Arabia–Eurasia collision. A key element of the mechanism is the presence of lateral and vertical lithospheric strength contrasts between the north Iranian continental and south Caspian oceanic crusts: when compression from the collision is applied across the region, the strong south Caspian oceanic crust, buried under > 10 km of premiddle Miocene sediment, interacts with the bottom of the mechanically strong continental upper crust of northern Iran, resulting in upward buckling of the continental crust and downward buckling of the oceanic crust. We test this mechanism using a finite-element numerical model with a Maxwell rheology and obtain results that are consistent with the geological and geophysical observations. The observations compiled here and the model results demonstrate the potential for using this region as a natural laboratory for studying the early stages of continent–oceanic collision, including processes like basin inversion, fault localization and, potentially, subduction initiation. 相似文献
112.
Gary Sands 《GeoJournal》2010,75(6):539-552
Canada’s three large city regions—Montréal, Toronto and Vancouver—have been relatively successful in retaining their Manufacturing
bases, while at the same time adding substantial numbers of New Economy job opportunities. Deindustrialization appears to
have occurred primarily in the Montréal CMA (Census Metropolitan Area) and in some smaller communities where motor vehicle
manufacturing was significant. Growth in New Economy jobs has occurred in the larger CMAs; the smaller urban areas have had
little success in attracting these jobs. For the most part, these trends appear to be path dependent: prosperous communities
with substantial proportions of New Economy jobs are likely to remain prosperous and to attract more such jobs. The lack of
significant correlation between Economic Health and the presence of immigrants, same sex couples, performing and visual artists
suggests that local economic development strategies based on these factors may have limited success. 相似文献
113.
Geochemical and mineralogical evidence for Sahara and Sahel dust additions to Quaternary soils on Lanzarote,eastern Canary Islands,Spain 总被引:1,自引:0,他引:1
Daniel R. Muhs James Budahn Gary Skipp Joseph M. Prospero DeAnna Patterson E. Arthur Bettis III 《地学学报》2010,22(6):399-410
Africa is the most important source of dust in the world today, and dust storms are frequent on the nearby Canary Islands. Previous workers have inferred that the Sahara is the most important source of dust to Canary Islands soils, with little contribution from the Sahel region. Soils overlying a late Quaternary basalt flow on Lanzarote, Canary Islands, contain, in addition to volcanic minerals, quartz and mica, exotic to the island’s bedrock. Kaolinite in the soils also likely has an exotic origin. Trace‐element geochemistry shows that the soils are derived from varying proportions of locally derived basalt and African dust. Major‐element geochemistry, clay mineralogy and interpretation of satellite imagery suggest that dust additions to the Canary Islands come not only from the Sahara Desert, but also from the Sahel region. 相似文献
114.
Changes to sediment sources following wildfire in a forested upland catchment,southeastern Australia
Hugh G. Smith Gary J. Sheridan Patrick N. J. Lane Philip J. Noske Henk Heijnis 《水文研究》2011,25(18):2878-2889
Few investigations link post‐fire changes to sediment sources and erosion processes with sediment yield response at the catchment scale. This linkage is essential if downstream impacts on sediment transport after fire are to be understood in the context of fire effects across different forest environments. In this study, we quantify changing source contributions to fine sediment (<63 µm) exported from a eucalypt forest catchment (136 ha) burnt by wildfire. The study catchment is one of a pair of research catchments located in the East Kiewa River valley in southeastern Australia that have been the subject of a research program investigating wildfire effects on runoff, erosion, and catchment sediment/nutrient exports. This previous research provided the opportunity to couple insights gained from a range of measurement techniques with the application of fallout radionuclides 137Cs and 210Pbex to trace sediment sources. It was found that hillslope surface erosion dominated exports throughout the 3·5‐year post‐fire measurement period. During this time there was a pronounced decline in the proportional surface contribution from close to 100% in the first six months to 58% in the fourth year after fire. Over the study period, hillslope surface sources accounted for 93% of the fine sediment yield from the burnt catchment. The largest decline in the hillslope contribution occurred between the first and second years after fire, which corresponded with the previously reported large decline in sediment yield, breakdown of water repellency in burnt soils, substantial reduction in hillslope erodibility, and rapid surface vegetation recovery. Coupling the information on sediment sources with hillslope process measurements indicated that only a small proportion of slopes contributed sediment to the catchment outlet, with material derived from near‐channel areas dominating the post‐fire catchment sediment yield response. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
115.
116.
117.
118.
D. Heath Jones Will Saunders Matthew Colless Mike A. Read Quentin A. Parker Fred G. Watson Lachlan A. Campbell Daniel Burkey Thomas Mauch Lesa Moore Malcolm Hartley Paul Cass Dionne James Ken Russell Kristin Fiegert John Dawe John Huchra Tom Jarrett Ofer Lahav John Lucey Gary A. Mamon Dominique Proust Elaine M. Sadler Ken-ichi Wakamatsu 《Monthly notices of the Royal Astronomical Society》2004,355(3):747-763
119.
Clinoform geometry,geomorphology, facies character and stratigraphic architecture of a sand‐rich subaqueous delta: Jurassic Sognefjord Formation,offshore Norway
下载免费PDF全文
![点击此处可从《Sedimentology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Stefano Patruno Gary J. Hampson Christopher A.‐L. Jackson Tom Dreyer 《Sedimentology》2015,62(1):350-388
The integration of core sedimentology, seismic stratigraphy and seismic geomorphology has enabled interpretation of delta‐scale (i.e. tens of metres high) subaqueous clinoforms in the upper Jurassic Sognefjord Formation of the Troll Field. Mud‐prone subaqueous deltas characterized by a compound clinoform morphology and sandy delta‐scale subaqueous clinoforms are common in recent tide‐influenced, wave‐influenced and current‐influenced settings, but ancient examples are virtually unknown. The data presented help to fully comprehend the criteria for the recognition of other ancient delta‐scale subaqueous clinoforms, as well as refining the depositional model of the reservoir in the super‐giant Troll hydrocarbon field. Two 10 to 60 m thick, overall coarsening‐upward packages are distinguished in the lower Sognefjord Formation. Progressively higher energy, wave‐dominated or current‐dominated facies occur from the base to the top of each package. Each package corresponds to a set of seismically resolved, westerly dipping clinoforms, the bounding surfaces of which form the seismic ‘envelope’ of a clinoform set and the major marine flooding surfaces recognized in cores. The packages thicken westwards, until they reach a maximum where the clinoform ‘envelope’ rolls over to define a topset–foreset–toeset geometry. All clinoforms are consistently oriented sub‐parallel to the edge of the Horda Platform (N005–N030). In the eastern half of the field, individual foresets are relatively gently dipping (1° to 6°) and bound thin (10 to 30 m) clinothems. Core data indicate that these proximal clinothems are dominated by fine‐grained, hummocky cross‐stratified sandstones. Towards the west, clinoforms gradually become steeper (5° to 14°) and bound thicker (15 to 60 m) clinothems that comprise medium‐grained, cross‐bedded sandstones. Topsets are consistently well‐developed, except in the westernmost area. No seismic or sedimentological evidence of subaerial exposure is observed. Deposition created fully subaqueous, near‐linear clinoforms that prograded westwards across the Horda Platform. Subaqueous clinoforms were probably fed by a river outlet in the north‐east and sculpted by the action of currents sub‐parallel to the clinoform strike. 相似文献
120.
Dáithí Stone Maximilian Auffhammer Mark Carey Gerrit Hansen Christian Huggel Wolfgang Cramer David Lobell Ulf Molau Andrew Solow Lourdes Tibig Gary Yohe 《Climatic change》2013,118(2):381-395
Future scenarios of the energy system under greenhouse gas emission constraints depict dramatic growth in a range of energy technologies. Technological growth dynamics observed historically provide a useful comparator for these future trajectories. We find that historical time series data reveal a consistent relationship between how much a technology’s cumulative installed capacity grows, and how long this growth takes. This relationship between extent (how much) and duration (for how long) is consistent across both energy supply and end-use technologies, and both established and emerging technologies. We then develop and test an approach for using this historical relationship to assess technological trajectories in future scenarios. Our approach for “learning from the past” contributes to the assessment and verification of integrated assessment and energy-economic models used to generate quantitative scenarios. Using data on power generation technologies from two such models, we also find a consistent extent - duration relationship across both technologies and scenarios. This relationship describes future low carbon technological growth in the power sector which appears to be conservative relative to what has been evidenced historically. Specifically, future extents of capacity growth are comparatively low given the lengthy time duration of that growth. We treat this finding with caution due to the low number of data points. Yet it remains counter-intuitive given the extremely rapid growth rates of certain low carbon technologies under stringent emission constraints. We explore possible reasons for the apparent scenario conservatism, and find parametric or structural conservatism in the underlying models to be one possible explanation. 相似文献