全文获取类型
收费全文 | 8184篇 |
免费 | 409篇 |
国内免费 | 36篇 |
专业分类
测绘学 | 277篇 |
大气科学 | 603篇 |
地球物理 | 3177篇 |
地质学 | 2668篇 |
海洋学 | 335篇 |
天文学 | 1210篇 |
综合类 | 46篇 |
自然地理 | 313篇 |
出版年
2022年 | 64篇 |
2021年 | 155篇 |
2020年 | 161篇 |
2019年 | 122篇 |
2018年 | 360篇 |
2017年 | 344篇 |
2016年 | 506篇 |
2015年 | 367篇 |
2014年 | 413篇 |
2013年 | 531篇 |
2012年 | 457篇 |
2011年 | 396篇 |
2010年 | 372篇 |
2009年 | 357篇 |
2008年 | 299篇 |
2007年 | 238篇 |
2006年 | 227篇 |
2005年 | 178篇 |
2004年 | 184篇 |
2003年 | 168篇 |
2002年 | 135篇 |
2001年 | 149篇 |
2000年 | 116篇 |
1999年 | 85篇 |
1998年 | 127篇 |
1997年 | 106篇 |
1996年 | 64篇 |
1995年 | 94篇 |
1994年 | 102篇 |
1993年 | 72篇 |
1992年 | 70篇 |
1991年 | 65篇 |
1990年 | 88篇 |
1989年 | 64篇 |
1988年 | 51篇 |
1987年 | 54篇 |
1986年 | 55篇 |
1985年 | 60篇 |
1984年 | 50篇 |
1983年 | 57篇 |
1982年 | 61篇 |
1981年 | 56篇 |
1980年 | 57篇 |
1979年 | 55篇 |
1978年 | 63篇 |
1977年 | 51篇 |
1975年 | 54篇 |
1973年 | 66篇 |
1972年 | 49篇 |
1971年 | 57篇 |
排序方式: 共有8629条查询结果,搜索用时 31 毫秒
981.
Depositional system and palaeoclimatic interpretations of Middle to Late Pleistocene travertines: Kocabaş, Denizli,south‐west Turkey
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)
Travertine deposits in western Turkey are very well‐exposed in the area of Kocaba?, in the eastern part of the Denizli Basin. The palaeoclimatic significance of these travertines is discussed using U/Th dates, stable isotope data and palynological evidence. The Kocaba? travertine occurrences are characterized by successions of depositional terraces associated with palaeosols and karstic features. The travertines have been classified into eight lithotypes and one erosional horizon, namely: laminated, coated bubble, reed, paper‐thin raft, intraclasts, micritic travertine with gastropods, extra‐formational pebbles and a palaeosol layer. The analysed travertines mostly formed between 181 ka and 80 ka (Middle to Late Pleistocene) during a series of climatic changes including glacial and interglacial intervals; their δ13C and δ18O values indicate that the depositional waters were mainly of basinal thermal origin, occasionally mixed with surficial meteoric water. Palynological results obtained from the palaeosols showed an abundance of non‐arboreal percentage and xerophytic plants (Oleaceae and Quercus evergreen type) indicating that a drought occurred. Marine Isotope Stage 6 is represented by grassland species but Marine Isotope Stage 5 is represented by Pinaceae–Pinus and Abies, Quercus and Oleaceae. Uranium/thorium analyses of the Kocaba? travertines show that deposition began in Marine Isotope Stage 6 (glacial) and continued to Marine Isotope Stage 4 (glacial), but mostly occurred in Marine Isotope Stage 5 (interglacial). The travertine deposition continued to ca 80 ka in the south‐west of the study area, in one particular depression depositional system. Palaeoenvironmental indicators suggest that the travertine depositional evolution was probably controlled by fault‐related movements that influenced groundwater flow. Good correlation of the stable isotope values and dates of deposition of the travertines and palynological data of palaeosols in the Kocaba? travertines serve as a starting point for further palaeoclimate studies in south‐west Turkey. Additionally, the study can be compared with other regional palaeoclimate archives. 相似文献
982.
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
983.
984.
985.
986.
Lukáš Ackerman Gordon Medaris Jr. Petr Špaček Jaromír Ulrych 《International Journal of Earth Sciences》2015,104(8):1957-1979
987.
Progressive failure leading to the 3 December 2013 rockfall at Puigcercós scarp (Catalonia,Spain) 总被引:1,自引:1,他引:0
A detailed analysis of the pre-failure behavior of the 3 December 2013 rockfall (1,012 m3) occurred on Puigcercós pilot study area (Catalonia, Spain) is presented. The exact date of failure was obtained based on a photographic monitoring performed every 4 h. The long-term monitoring (2,217 days) of the rock slope carried out by a Terrestrial LiDAR allowed the early detection of both pre-failure deformation and precursory rockfalls preceding the final failure. By means of the analysis of the pre-failure deformation, four different deformed areas were detected and the tertiary creep phase was observed in three of them. An attempt to predict the time to failure was performed using the Fukuzono’s (1985) method. Furthermore, the temporal evolution of the precursory rockfalls occurred in those four areas during the progressive failure showed a close resemblance with the exponential pattern of the cumulated displacements at tertiary creep stage. Finally, the study of the meteorological conditions did not show any single triggering factor associated with the final failure. Reversely, the increase in the occurrence of precursory rockfalls on several areas of the slope together with the observed acceleration on the deformation pattern reinforce the role of a progressive degradation of the stability conditions, which ultimately leaded to the 3 December rockfall event. 相似文献
988.
989.
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
990.