全文获取类型
收费全文 | 320篇 |
免费 | 8篇 |
专业分类
测绘学 | 4篇 |
大气科学 | 31篇 |
地球物理 | 84篇 |
地质学 | 111篇 |
海洋学 | 26篇 |
天文学 | 39篇 |
综合类 | 3篇 |
自然地理 | 30篇 |
出版年
2024年 | 2篇 |
2023年 | 1篇 |
2022年 | 5篇 |
2021年 | 4篇 |
2020年 | 11篇 |
2019年 | 9篇 |
2018年 | 13篇 |
2017年 | 20篇 |
2016年 | 12篇 |
2015年 | 9篇 |
2014年 | 11篇 |
2013年 | 11篇 |
2012年 | 13篇 |
2011年 | 13篇 |
2010年 | 11篇 |
2009年 | 23篇 |
2008年 | 17篇 |
2007年 | 13篇 |
2006年 | 8篇 |
2005年 | 9篇 |
2004年 | 11篇 |
2003年 | 12篇 |
2002年 | 13篇 |
2001年 | 6篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 4篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1975年 | 1篇 |
1974年 | 4篇 |
1973年 | 3篇 |
排序方式: 共有328条查询结果,搜索用时 46 毫秒
41.
Natural Hazards - Hurricanes and tropical storms are natural hazards with the capacity to devastate coastal regions. Understanding this catastrophic potential is critical to support informed... 相似文献
42.
Catherine Heymans Ludovic Van Waerbeke David Bacon Joel Berge Gary Bernstein Emmanuel Bertin Sarah Bridle Michael L. Brown Douglas Clowe Håkon Dahle Thomas Erben Meghan Gray Marco Hetterscheidt Henk Hoekstra Patrick Hudelot Mike Jarvis Konrad Kuijken Vera Margoniner Richard Massey Yannick Mellier Reiko Nakajima Alexandre Refregier Jason Rhodes Tim Schrabback David Wittman 《Monthly notices of the Royal Astronomical Society》2006,368(3):1323-1339
43.
Adrian Gilli Flavio S. Anselmetti Daniel Ariztegui† Milan Beres† Judith A. McKenzie Vera Markgraf‡ 《Sedimentology》2005,52(1):1-23
The results of a seismic stratigraphic analysis of a closed lake basin, Lago Cardiel, in southernmost South America are reported. Very few high-resolution, continental records spanning the Late Quaternary have been obtained from this region. Seismic sequence stratigraphic analysis allows a reconstruction of lake level variations. Two major hiatuses of unknown age occurred during the early evolution of the basin with the deposition of an alluvial fan in a restricted area in the intervening time period. Following the development of a relatively shallow lake during the late Pleistocene and a short desiccation pulse around 11 220 14C yr BP, a transgression of over 135 m occurred at the beginning of the Holocene. The transgression was associated with the formation of beach ridges preserved in the lake stratigraphy on the floor of the modern Lago Cardiel at four different elevations. The preservation of largely unreworked beach ridges indicates a stepwise rise in the lake level. There is no seismic evidence of a major lowering of the lake below modern level during the entire Holocene. Deposition since the mid-Holocene is marked by strong lateral differences in sediment accumulation with a depocentre slightly to the north of the basin midpoint and a pronounced mounded distribution. Seismic reflection geometries, as well as sedimentological characteristics indicate a lacustrine contourite drift covering an area of 80–100 km2. As Lago Cardiel is under the influence of westerly winds, these most likely drove lake circulation. The identification of drowned beach ridges and of contourite drifts illustrates that high-resolution seismic stratigraphy is not only a powerful tool in reconstructing past lake level elevations for closed lake basins, but it can also provide information about the rate of lake level changes and the presence and strength of lake currents. 相似文献
44.
Martin Mozny Mirek Trnka Zdenek Zalud Petr Hlavinka Jiri Nekovar Vera Potop Michal Virag 《Theoretical and Applied Climatology》2012,107(1-2):99-111
Since 2000, the network of stations that make up the Czech Hydrometeorological Institute (CHMI) has measured the soil moisture content at the 0- to 0.9-m layer using sensors placed within the natural soil profile under closely cropped grass cover. Using information from 8?years of continuous observation at seven stations throughout the Czech Republic, we verified the usefulness of the Soil Moisture Index (SMI). The SMI is a potentially useful index for calculating the water deficit in the Czech Republic and Central Europe. During this period, a statistically significant decrease in moisture content was detected, and negative SMI values predominated. There were frequent occurrences of flash drought, defined as a very rapid decline in soil moisture during a 3-week period. The CHMI can use SMI values below ?3 in the Integrated Warning Service System. The routine calculation of SMI values can alert agricultural producers to the development of flash drought conditions and provide them with information regarding the effectiveness of recent rainfall events. An increase in soil moisture, in contrast, could serve as a warning sign for hydrology because it creates the preconditions for flooding. The complex study of soil humidity regimes is becoming more significant in connection with current global climatic change warnings in hydrological cycles. 相似文献
45.
The investigation of supernova remnants (SNRs) across the electromagnetic spectrum from radio up to very high energy gamma-rays can serve as a test of the particle acceleration and touches on one of the unresolved problems of modern astrophysics, namely the origin of cosmic rays and the Galaxy's contribution to the overall cosmic ray spectrum. The multiwavelength observations of Cas A SNR demonstrated that structure and spectral features have clear signs of young SNRs and its overall properties make this object the best target to test a hypothesis of cosmic ray origin in SNRs. Studies of Cas A at very high energies by SHALON telescope showed the location of TeV gamma-ray emission region relative to the position of reveres shock. Also, the spectral energy distribution was obtained at high and very high energies. To describe the spectral and structural features of this SNR viewed in non-thermal emission, two approaches involving reverse and also both reverse and forward shocks to the mechanism of diffusive shock acceleration of cosmic rays in Cas A were applied. It is demonstrated that the observational properties of Cas A are well reproduced by the hadronic model with significant contribution of both the forward and reverse shocks in the generation of broadband emission. Calculation results suggest that the very high efficiency of particle acceleration in Cas A, which value is up to 25% of the supernova explosion energy with energy of accelerated particles not exceeding of eV. Whereas, the forward shock model predicts the spectral characteristics of the TeV-gamma-emission corresponding to ones detected at 800 GeV–40 TeV that are the evidence of acceleration of the hadronic cosmic rays in shells of SNRs up to eV 相似文献
46.
Vera K. Rosenbush Vasilij G. Shevchenko Alexander V. Sergeev Feodor P. Velichko Nikolai V. Karpov 《Icarus》2009,201(2):655-665
We present new polarimetric and photometric observations of high-albedo E-type Asteroid 44 Nysa in the BVRI wavebands at phase angles ranging from 0.41° to 7.49° during the 2005 opposition. A bimodal phase-angle dependence of polarization was found for Nysa in the V band. The polarization opposition effect was revealed in the form of a secondary minimum of negative polarization with amplitude ∼0.3% centered at a phase angle ∼0.8°. It is superimposed on the regular negative polarization branch with minimal polarization −0.30% at a phase angle 5.8°. We analyzed all available polarimetric data for E-type Asteroids 44 Nysa, 64 Angelina, and 214 Ashera and confirmed the presence of the polarization opposition effect for high-albedo asteroids at phase angle ∼1° with an amplitude ∼0.35%. The magnitude-phase curves reveal the presence of spike-like opposition effect of brightness for 44 Nysa in the BVRI spectral bands. 44 Nysa is the second high-albedo asteroid after 64 Angelina for which both the polarization opposition effect and the brightness opposition effect are detected. The differences between the parameters of the opposition effects for silicate surfaces (44 Nysa, 64 Angelina, Io) and icy surfaces (Europa, Ganymede, Iapetus, Saturn's rings) are discussed. The specific morphological parameters of opposition effects, in particular the angular width of the polarization opposition effect is comparable to that of the brightness opposition effect, provide almost unequivocal evidence that they are caused by coherent backscattering. One of unexpected results of our investigation is that 44 Nysa becomes bluer with increasing phase angle, while 64 Angelina shows phase reddening. 相似文献
47.
Jorge Del Río Vera Francisco Criado-Aldeanueva Jesús García-Lafuente F. Javier Soto-Navarro 《Global and Planetary Change》2009,68(3):232-235
Altimetry measurements over the Ionian region and tide gauge records along the southern Italian coasts have been combined to analyse the negative sea level trend over the Ionian basin in the last decades. The apparent decreasing trend should be better understood as an abrupt sea level drop in 1998 probably linked to changes in the surface circulation in the Ionian basin induced by the Eastern Mediterranean Transient, which changed from anticyclonic to cyclonic about March 1998. From then onwards, a rising rate of 7.9 ± 0.9 mm/year is observed over the basin. 相似文献
48.
Aleksi Räsänen Vera Kauppinen Sirkku Juhola Gunhild Setten Haakon Lein 《Norsk geografisk tidsskrift. Norwegian journal of geography》2020,74(3):165-180
ABSTRACT Despite a notable increase in the literature on community resilience, the notion of ‘community’ remains underproblematised. This is evident within flood risk management (FRM) literature, in which the understanding and roles of communities may be acknowledged but seldom discussed in any detail. The purpose of the article is to demonstrate how community networks are configured by different actors, whose roles and responsibilities span spatial scales within the context of FRM. Accordingly, the authors analyse findings from semi-structured interviews, policy documents, and household surveys from two flood prone areas in Finnish Lapland. The analysis reveals that the ways in which authorities, civil society, and informal actors take on multiple roles are intertwined and form different types of networks. By implication, the configuration of community is fuzzy, elusive and situated, and not confined to a fixed spatiality. The authors discuss the implications of the complex nature of community for FRM specifically, and for community resilience more broadly. They conclude that an analysis of different actors across scales contributes to an understanding of the configuration of community, including community resilience, and how the meaning of community takes shape according to the differing aims of FRM in combination with differing geographical settings. 相似文献
49.
Theresa Tufuor Chizu Sato 《Norsk geografisk tidsskrift. Norwegian journal of geography》2017,71(1):46-59
In recent decades there has been a large migration stream of single women from the north to Accra in Ghana. Existing studies have focused on young migrant women’s livelihood strategies in their place of destination. However, once-married women – divorced and widowed women and neglected wives – also migrate, and their motivations for migration are less known. Drawing on qualitative and quantitative methods, the authors investigate the effects of gender norms, age, marital status, socio-economic status, and position in households on women’s decisions to migrate. The results revealed that migrant women from resource-poor households, regardless of age, marital status and position in households, commonly cited a gain in autonomy as an important motivation for their migration. From a differentiated perspective, young unmarried women aspired to prepare themselves for often expensive religious marriage ceremonies, whereas once-married women invest in their children’s education and build their own housing. By paying attention to the effects of gender norms, age, marital status, socio-economic status, and position in households on women’s decisions to migrate, the study illuminates the contradictory ways in which their migration practices are both shaped by and shape gender ideologies in parts of contemporary northern Ghana. 相似文献
50.
Cretaceous deformation of the southern Central Andes: synorogenic growth strata in the Neuquén Group (35° 30′–37° S) 下载免费PDF全文
Lucas M. Fennell Andrés Folguera Maximiliano Naipauer Guido Gianni Emilio A. Rojas Vera Germán Bottesi Victor A. Ramos 《Basin Research》2017,29(Z1):51-72
The Neuquén Group is an Upper Cretaceous continental sedimentary unit exhumed during the latest Miocene contractional phase occurred in the southern Central Andes, allowing a direct field observation and study of the depositional geometries. The identification of growth strata on these units surrounding the structures of the frontal parts of the Andes, sedimentological analyses and U–Pb dating of detrital components, allowed the definition of a synorogenic unit that coexisted with the uplift of the early Andean orogen since ca. 100 Ma, maximum age obtained in this work, compatible with previous assignments and constrained in the top by the deposition of the Malargüe Group, in the Maastrichtian (ca. 72 Ma). The definition of a wedge top area in this foreland basin system, where growth strata were described, permitted to identify a Late Cretaceous orogenic front and foredeep area, whose location and amplitude contrast with previous hypotheses. This wedge top area was mostly fed from the paleo‐Andes with small populations coming from sources in the cratonic area that are interpreted as a recycling in Jurassic and Lower Cretaceous sections, which contrasts with other analyses performed at the foredeep zone that have mixed sources. In particular, Permian sources are interpreted as coming directly from the cores of the basement structures, where Neopaleozoic sections are exposed, next to the synorogenic sedimentation, implying a strong incision in Late Cretaceous times with an exhumation structural level similar to the present. The maximum recognised advance for this Late Cretaceous deformation in the study area is approximately 500 km east of the Pacific trench, which constitutes an anomaly compared with neighbour segments where Late Cretaceous deformations were found considerably retracted. The geodynamic context of the sedimentation of this unit is interpreted as produced under the westward fast moving of South America, colliding with two consecutive mid‐ocean ridges during a period of important plate reorganisation. The subduction of young, anhydrous, buoyant lithosphere would have produced changes in the subduction geometry, reflected first by an arc waning/gap and subsequently by an arc migration that coexisted with synorogenic sedimentation. These magmatic and deformational processes would be the product of a shallow subduction regime, following previous proposals, which occurred in Late Cretaceous times, synchronous to the sedimentation of the Neuquén Group. 相似文献