全文获取类型
收费全文 | 402篇 |
免费 | 16篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 12篇 |
大气科学 | 37篇 |
地球物理 | 90篇 |
地质学 | 126篇 |
海洋学 | 44篇 |
天文学 | 63篇 |
综合类 | 4篇 |
自然地理 | 44篇 |
出版年
2024年 | 4篇 |
2023年 | 2篇 |
2022年 | 3篇 |
2021年 | 17篇 |
2020年 | 19篇 |
2019年 | 17篇 |
2018年 | 19篇 |
2017年 | 15篇 |
2016年 | 22篇 |
2015年 | 16篇 |
2014年 | 25篇 |
2013年 | 35篇 |
2012年 | 17篇 |
2011年 | 21篇 |
2010年 | 23篇 |
2009年 | 13篇 |
2008年 | 20篇 |
2007年 | 18篇 |
2006年 | 16篇 |
2005年 | 13篇 |
2004年 | 9篇 |
2003年 | 11篇 |
2002年 | 8篇 |
2001年 | 3篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1991年 | 1篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 6篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1977年 | 1篇 |
1973年 | 2篇 |
1968年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有420条查询结果,搜索用时 15 毫秒
411.
Abstract. The long-spined sea urchin Diadema antillarum has been reported to be the major food item of the queen triggerfish, Balistes vetula in the Caribbean. This sea urchin has undergone a massive mortality on reefs throughout the Caribbean during 1983. The dietary habits of twenty-three queen triggerfish from patch reef habitats in Belize were examined. It was found that crabs and chitons now form the major dietary items when D. antillarum is not available. It is suggested that this predator, which was previously specialized on a single food item, is able to shift resource utilization in the absence of its primary food source, and that the queen triggerfish can capture diverse prey from a wide variety of habitats. 相似文献
412.
The Mesozoic ostracod genus Arculicythere Grékoff: further evidence for the southern Gondwana seaway
This paper demonstrates that Arculicythere Grékoff is a widespread taxon in the uppermost Upper Jurassic and Lower Cretaceous of Gondwana. It occurs in Madagascar, India, Israel, South Africa, the Falklands Plateau, Argentina and Australia. The earliest record is from the Upper Tithonian of Madagascar but the most profuse occurrences are in the Albian, when the genus was very widespread around Gondwana. Its distribution seems to be associated with a major southern Gondwana seaway, and the genus provides additional proof of the existence of this corridor. Unlike another endemic gondwanine genus, Majungaella Grékoff, which ranged from earlier in the Jurassic but extended into the Neogene in the Antarctic, or Rostrocytheridea Dingle that survived into the Campanian of the Antarctic, Arculicythere seems to have become extinct in the Albian. 相似文献
413.
We have found some mistakes in the article by Sara Casciati(2007).The revisions are given below:
1.The last sentence of the first paragraph in p.262 "(Casciati and Faravelli,2007)" should be changed to "(Casciati and Faravelli,1991)". 相似文献
414.
Sara L. Webb 《Quaternary Research》1986,26(3)
Rapid rates of species range extension during the Holocene represent seed dispersal distances of at least 6 to 8 km per generation for North American species of Fagus, Quercus, and Carya, taxa whose fruits are heavy nuts. Occasional seed dispersal by biotic seed predators is necessary for these dispersal distances. One likely agent for dispersal across long distances and habitat discontinuities was the extinct (since 1914 A.D.) passenger pigeon (Ectopistes migratorius). This bird's abundance, capacity for delayed digestion, and nomadic habits strongly suggest an occasional seed dispersal role, although a coevolutionary seed dispersal relationship cannot be inferred from available evidence. The capacity of some heavy seeds for dispersal distances greater than those of most light, wind-dispersed seeds has biogeographic and genetic implications. 相似文献
415.
416.
Short‐term Quantitative Precipitation Forecasts (QPFs) can be achieved from numerical weather prediction (NWP) models or radar nowcasting, that is the extrapolation of the precipitation at a future time from consecutive radar scans. Hybrid forecasts obtained by merging rainfall forecasts from radar nowcasting and NWP models are potentially more skilful than either radar nowcasts or NWP rainfall forecasts alone. This paper provides an assessment of deterministic and probabilistic high‐resolution QPFs achieved by implementing the Short‐term Ensemble Prediction System developed by the UK Met Office. Both radar nowcasts and hybrid forecasts have been performed. The results show that the performance of both deterministic nowcasts and deterministic hybrid forecasts decreases with increasing rainfall intensity and spatial resolution. The results also show that the blending with the NWP forecasts improves the performance of the forecasting system. Probabilistic hybrid forecasts have been obtained through the modelling of a stochastic noise component to produce a number of equally likely ensemble members, and the comparative assessment of deterministic and probabilistic hybrid forecasts shows that the probabilistic forecasting system is characterised by a higher discrimination accuracy than the deterministic one. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
417.
Lucia Luzi Sara Lovati Ezio D’Alema Simone Marzorati Domenico Di Giacomo Salomon Hailemikael Ettore Cardarelli Michele Cercato Gerarda Di Filippo Giuliano Milana Giuseppe Di Giulio Mario Rainone Patrizio Torrese Patrizio Signanini Gabriele Scarascia Mugnozza Stefano Rivellino Antonella Gorini 《Bulletin of Earthquake Engineering》2010,8(5):1189-1207
Geological, geophysical and geotechnical investigations, for the characterization of the strong-motion recording sites managed by the Italian Civil Protection, have been carried out in the framework of the project “Italian strong-motion database in the period 1972–2004”. The project aimed at creating an updated database of strong-motion data acquired in Italy by different institutions in the time span 1972–2004, and at improving the quality of disseminated data. This article illustrates the state of the recording site characterization before the beginning of the project, explains the criteria adopted to select the sites where geophysical/geotechnical investigation have been performed and describes the results of the promoted field surveys. 相似文献
418.
419.
Sara Picone Francesca Alvisi Enrico Dinelli Caterina Morigi Alessandra Negri Mariangela Ravaioli Carmela Vaccaro 《第四纪科学杂志》2008,23(5):489-501
Sedimentological, geochemical and micropalaeontological data from sediment cores in the northwestern Adriatic Sea were obtained to reconstruct the stratigraphic framework and palaeogeographic setting during the last post‐glacial sea‐level rise (14000–6000 yr BP). Four lithostratigraphic units were identified: (a) distal plain deposits (>14000 yr BP), submerged during the first phases of marine ingression; (b) coastal lagoon system; (c) barrier‐lagoon system, which is dated back to between 10019 ± 61 and 10228 ± 174 cal. yr BP from 14C dating on peat and shell remains; (d) marine prodelta deposits (<5500 yr BP). Geochemical data allow the identification of three distinct sediment sources: River Po, River Adige and Eastern Alpine rivers characterised by decreasing Ni/Mg ratios (50–70, 8–15 and 5–10, respectively) and Ba/Al ratios of 45–55, 55–65 and 35–45, respectively. The three sources display different relative abundances in time. During the Lateglacial, the Po is the main sediment source for the southern cores, whereas the Eastern Alps and the River Adige are the main sediment sources for the northern cores. This suggests a northern position of the Po River bed compared to previous studies. Coastal drowning led to a homogenization of the provenance signal within the sediments. Only after the marine transgression does a River Po signal appear in the northern cores. At the same time, in the southern cores the signal of Eastern Alpine rivers becomes stronger. Transgressive barrier‐lagoon and recent sediments do not display a predominant signal for provenance indicators. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
420.