全文获取类型
收费全文 | 8111篇 |
免费 | 281篇 |
国内免费 | 75篇 |
专业分类
测绘学 | 221篇 |
大气科学 | 586篇 |
地球物理 | 2420篇 |
地质学 | 2976篇 |
海洋学 | 440篇 |
天文学 | 1429篇 |
综合类 | 30篇 |
自然地理 | 365篇 |
出版年
2022年 | 63篇 |
2021年 | 119篇 |
2020年 | 109篇 |
2019年 | 97篇 |
2018年 | 318篇 |
2017年 | 303篇 |
2016年 | 448篇 |
2015年 | 286篇 |
2014年 | 412篇 |
2013年 | 514篇 |
2012年 | 394篇 |
2011年 | 416篇 |
2010年 | 377篇 |
2009年 | 395篇 |
2008年 | 325篇 |
2007年 | 300篇 |
2006年 | 318篇 |
2005年 | 208篇 |
2004年 | 225篇 |
2003年 | 183篇 |
2002年 | 140篇 |
2001年 | 147篇 |
2000年 | 114篇 |
1999年 | 119篇 |
1998年 | 139篇 |
1997年 | 133篇 |
1996年 | 103篇 |
1995年 | 73篇 |
1994年 | 69篇 |
1993年 | 88篇 |
1992年 | 72篇 |
1991年 | 74篇 |
1990年 | 74篇 |
1989年 | 66篇 |
1988年 | 59篇 |
1987年 | 68篇 |
1986年 | 79篇 |
1985年 | 61篇 |
1984年 | 70篇 |
1983年 | 64篇 |
1982年 | 66篇 |
1981年 | 58篇 |
1980年 | 51篇 |
1979年 | 58篇 |
1977年 | 44篇 |
1976年 | 44篇 |
1975年 | 43篇 |
1974年 | 44篇 |
1973年 | 51篇 |
1971年 | 49篇 |
排序方式: 共有8467条查询结果,搜索用时 15 毫秒
991.
Historical torrential flood events in the Kolubara river basin 总被引:1,自引:0,他引:1
992.
993.
994.
995.
Réka?LukácsEmail author Szabolcs?Harangi Olivier?Bachmann Marcel?Guillong Martin?Dani?ík Yannick?Buret Albrecht?von?Quadt István?Dunkl László?Fodor Jakub?Sliwinski Ildikó?Soós János?Szepesi 《Contributions to Mineralogy and Petrology》2015,170(5-6):52
A silicic ignimbrite flare-up episode occurred in the Pannonian Basin during the Miocene, coeval with the syn-extensional period in the region. It produced important correlation horizons in the regional stratigraphy; however, they lacked precise and accurate geochronology. Here, we used U–Pb (LA-ICP-MS and ID-TIMS) and (U–Th)/He dating of zircons to determine the eruption ages of the youngest stage of this volcanic activity and constrain the longevity of the magma storage in crustal reservoirs. Reliability of the U–Pb data is supported by (U–Th)/He zircon dating and magnetostratigraphic constraints. We distinguish four eruptive phases from 15.9 ± 0.3 to 14.1 ± 0.3 Ma, each of which possibly includes multiple eruptive events. Among these, at least two large volume eruptions (>10 km3) occurred at 14.8 ± 0.3 Ma (Demjén ignimbrite) and 14.1 ± 0.3 Ma (Harsány ignimbrite). The in situ U–Pb zircon dating shows wide age ranges (up to 700 kyr) in most of the crystal-poor pyroclastic units, containing few to no xenocrysts, which implies efficient recycling of antecrysts. We propose that long-lived silicic magma reservoirs, mostly kept as high-crystallinity mushes, have existed in the Pannonian Basin during the 16–14 Ma period. Small but significant differences in zircon, bulk rock and glass shard composition among units suggest the presence of spatially separated reservoirs, sometimes existing contemporaneously. Our results also better constrain the time frame of the main tectonic events that occurred in the Northern Pannonian Basin: We refined the upper temporal boundary (15 Ma) of the youngest counterclockwise block rotation and the beginning of a new deformation phase, which structurally characterized the onset of the youngest volcanic and sedimentary phase. 相似文献
996.
New insights into geochemical behaviour in ancient marine carbonates (Upper Jurassic Ammonitico Rosso): Novel proxies for interpreting sea‐level dynamics and palaeoceanography
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)
Rute Coimbra Adrian Immenhauser Federico Olóriz Víctor Rodríguez‐Galiano Mario Chica‐Olmo 《Sedimentology》2015,62(1):266-302
Elemental concentrations in Phanerozoic sea water are known to fluctuate both in time and space. With regard to carbonates precipitated from marine fluids, elemental concentrations in the carbonate crystal lattice are affected by a complex array of equilibrium and non‐equilibrium as well as post‐depositional alteration processes. To assess the potential of carbonate elemental chemostratigraphy, seven Upper Jurassic sections were investigated along a proximal to distal transect across the south‐east Iberian palaeomargin. The aim was to explore stratigraphic and spatial variations in calcium, strontium, magnesium, iron and manganese elemental abundances. The epicontinental geochemical record is influenced by the combination of continental runoff and a significant diagenetic overprint. In contrast, the epioceanic geochemical record agrees with reconstructed open marine sea water values, reflecting a moderate degree of syn‐depositional to early marine pore water diagenesis. Establishing a fair degree of preservation of matrix micrite, a thorough statistical approach was applied and elemental associations tested for their environmental significance. Principal component and hierarchical cluster analyses revealed a persistent relation between carbonate magnesium, iron and strontium abundances. Processes related to early diagenetic nodulation in Ammonitico Rosso facies most probably account for the incorporation of these elements in the calcium carbonate lattice. The clear decoupling of carbonate manganese abundance with respect to the remaining elements is documented and related to high sea floor spreading rates and hydrothermal activity during the Late Jurassic. The investigation of potential time‐fluctuation of geochemical patterns was approached through variogram computation. The observed temporal behaviour is most likely to be forced by relative sea‐level dynamics, reflecting Late Jurassic palaeoceanographic conditions and potential planetary interactions. The data obtained in this study highlight the utility of elemental data from carbonate matrix micrites as geochemical proxies for studying the influence of remote trigger factors. 相似文献
997.
998.
999.
Lukáš Ackerman Gordon Medaris Jr. Petr Špaček Jaromír Ulrych 《International Journal of Earth Sciences》2015,104(8):1957-1979
1000.
Human-induced coastal landslide reactivation. Monitoring by PSInSAR techniques and urban damage survey (SE Spain) 总被引:1,自引:1,他引:0