全文获取类型
收费全文 | 323篇 |
免费 | 16篇 |
国内免费 | 18篇 |
专业分类
测绘学 | 4篇 |
大气科学 | 18篇 |
地球物理 | 106篇 |
地质学 | 121篇 |
海洋学 | 14篇 |
天文学 | 65篇 |
综合类 | 10篇 |
自然地理 | 19篇 |
出版年
2024年 | 2篇 |
2023年 | 2篇 |
2022年 | 6篇 |
2021年 | 6篇 |
2020年 | 7篇 |
2019年 | 10篇 |
2018年 | 27篇 |
2017年 | 18篇 |
2016年 | 19篇 |
2015年 | 27篇 |
2014年 | 20篇 |
2013年 | 31篇 |
2012年 | 22篇 |
2011年 | 27篇 |
2010年 | 20篇 |
2009年 | 13篇 |
2008年 | 14篇 |
2007年 | 17篇 |
2006年 | 7篇 |
2005年 | 7篇 |
2004年 | 11篇 |
2003年 | 5篇 |
2002年 | 13篇 |
2001年 | 6篇 |
2000年 | 6篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1989年 | 1篇 |
排序方式: 共有357条查询结果,搜索用时 31 毫秒
191.
192.
Debris flows triggered from non-stationary glacier lake outbursts: the case of the Teztor Lake complex (Northern Tian Shan,Kyrgyzstan) 总被引:1,自引:0,他引:1
Sergey Aleksandrovich Erokhin Vitalii Viktorovich Zaginaev Anna Alexandrovna Meleshko Virginia Ruiz-Villanueva Dmitry Aleksandrovich Petrakov Sergey Semenovich Chernomorets Karina Saidovna Viskhadzhieva Olga Valerjevna Tutubalina Markus Stoffel 《Landslides》2018,15(1):83-98
One of the most far-reaching glacier-related hazards in the Tian Shan Mountains of Kyrgyzstan is glacial lake outburst floods (GLOFs) and related debris flows. An improved understanding of the formation and evolution of glacial lakes and debris flow susceptibility is therefore essential to assess and mitigate potential hazards and risks. Non-stationary glacier lakes may fill periodically and quickly; the potential for them to outburst increases as water volume may change dramatically over very short periods of time. After the outburst or drainage of a lake, the entire process may start again, and thus these non-stationary lakes are of particular importance in the region. In this work, the Teztor lake complex, located in Northern Kyrgyzstan, was selected for the analysis of outburst mechanisms of non-stationary glacial lakes, their formation, as well as the triggering of flows and development of debris flows and floods downstream of the lakes. The different Teztor lakes are filled with water periodically, and according to field observations, they tend to outburst every 9–10 years on average. The most important event in the area dates back to 1953, and another important event occurred on July 31, 2012. Other smaller outbursts have been recorded as well. Our study shows that the recent GLOF in 2012 was caused by a combination of intense precipitation during the days preceding the event and a rapid rise in air temperatures. Analyses of features in the entrainment and depositional zones point to a total debris flow volume of about 200,000 m3, with discharge ranging from 145 to 340 m3 s?1 and flow velocities between 5 and 7 m s?1. Results of this study are key for a better design of sound river corridor planning and for the assessment and mitigation of potential GLOF hazards and risks in the region. 相似文献
193.
Sergey V. Churakov 《Geochimica et cosmochimica acta》2007,71(5):1130-1144
Edge sites of clay minerals play a key role for pH dependent sorption of ions from solutions of electrolytes. Pyrophyllite, Al2[Si4O10](OH)2, is an important structural prototype for a variety of 2:1 dioctahedral phyllosilicates but in contrast to the other clays has no permanent structural charge. The structure of thin water films confined between most common edges of 1Tc pyrophyllite: (0 1 0), (1 1 0) and (1 0 0), was analyzed by means of ab initio molecular dynamic simulations. The system setup allowed for a full flexibility of the interfaces and a proton exchange between the edges of pyrophyllite and water molecules in solution. The structure of hydrated surfaces is compared with the recent predictions of static geometry optimizations for edge-vacuum interfaces. All surfaces studied reveal a strong hydrophilic character of edge similar to the hydrated silica surface and the facets of simple layered hydroxides. Spontaneous proton transfer between different surface sites were observed in molecular dynamics simulations of the (0 1 0) interface. The proton bound to the SiOH site was found to exchange with the AlOH group by the mechanism . The direction of the proton transfer agrees with the scale of relative proton affinities for surface sites obtained from the static calculations. Alternatively, the proton attached to the AlOH2 site exchanges with the AlOH group. In both reactions, the protons are transferred through the chains of hydrogen bonds formed between water molecules in the solution and the surface sites. The observed mechanisms might be one of the basic schemes for the surface proton diffusion in compacted clays. Kinetics of the proton transfer at edge sites is limited by the rate of rearrangements of the water molecules near interface. 相似文献
194.
Olga Kalinina Sergey V Goryachkin Nina A Karavaeva Dmitriy I Lyuri Luise Giani 《Carbon balance and management》2010,5(1):1
Background
Until recently, a lot of arable lands were abandoned in many countries of the world and, especially, in Russia, where about half a million square kilometers of arable lands were abandoned in 1961-2007. The soils at these fallows undergo a process of natural restoration (or self-restoration) that changes the balance of soil organic matter (SOM) supply and mineralization. 相似文献195.
A data assimilation method was used to estimate the variability of three ecologically significant features of the Columbia River estuary and plume: the size of the plume, the orientation of the plume, and the length of the salinity intrusion in the estuary. Our data assimilation method was based on a reduced-dimension Kalman filter that enables fast data assimilation of nonlinear dynamics in the estuary and plume. The assimilated data included measurements of salinity, temperature, and water levels at 13 stations in the estuary and at five moorings in the plume. 相似文献
196.
Wilson JG Komakhidze A Osadchaya T Alyomov S Romanov A Tediashvili M 《Marine pollution bulletin》2008,57(1-5):202-207
Anthropogenic pressures have resulted in measurable impacts on the coastal ecosystems of the northern (Sevastopol Bay, Ukraine) and eastern (Batumi aquatoria, Georgia) Black Sea. Indices suggest that major impacts are relatively localized and are comparable to similar situations in the northern Atlantic. In contrast, biodiversity was appreciably lower than from comparable north Atlantic waters. The number of macrobenthic species was typically round 50, less than half the number that might be expected from similar exercises in US or European waters. Site-specific indices likewise indicated a somewhat lower diversity within communities, yielding metrics which would indicate a measure of stress in N. Atlantic situations. Microbial status was generally good, although regions close to urbanisation did not comply with standards laid down in the current EC Bathing Water Directive (76/EC/160). Likewise viruses were more commonly, although not exclusively, associated with urban locations, as were phages. Microbial investigation of the sediments confirmed the presence of heterotrophic and oil-oxidising bacteria. Abundance of the latter was closely correlated to the degree of oil contamination of the sediments, and to temperature, although for both, the results showed that the increase in bacterial abundance did level off beyond a certain point. Numbers of oil-oxidising bacteria in the water column displayed a classical response to temperature, with abundance doubling over a 10-degree C rise in temperature. Overall the results suggest that while indices in current use are useful in evaluating coastal quality in the Black Sea, some adjustments would be necessary especially in the establishment of baseline or reference values. 相似文献
197.
Biagio Giaccio Roberto Isaia Francesco G. Fedele Emanuele Di Canzio John Hoffecker Annamaria Ronchitelli Andrey A. Sinitsyn Mikhail Anikovich Sergey N. Lisitsyn Vasil V. Popov 《Journal of Volcanology and Geothermal Research》2008
Tephra layers from archaeological sites in southern Italy and eastern Europe stratigraphically associated with cultural levels containing Early Upper Palaeolithic industry were analysed. The results confirm the occurrence of the Campanian Ignimbrite tephra (CI; ca. 40 cal ka BP) at Castelcivita Cave (southern Italy), Temnata Cave (Bulgaria) and in the Kostenki–Borshchevo area of the Russian Plain. This tephra, originated from the largest eruption of the Phlegrean Field caldera, represents the widest volcanic deposit and one of the most important temporal/stratigraphic markers of western Eurasia. At Paglicci Cave and lesser sites in the Apulia region we recognise a chemically and texturally different tephra, which lithologically, chronologically and chemically matches the physical and chemical characteristics of the Plinian eruption of Codola; a poorly known Late Pleistocene explosive event from the Neapolitan volcanoes, likely Somma–Vesuvius. For this latter, we propose a preliminary age estimate of ca. 33 cal ka BP and a correlation to the widespread C-10 marine tephra of the central Mediterranean. The stratigraphic position of both CI and Codola tephra layers at Castelcivita and Paglicci help date the first and the last documented appearance of Early Upper Palaeolithic industries of southern Italy to ca. 41–40 and 33 cal ka BP, respectively, or between two interstadial oscillations of the Monticchio pollen record – to which the CI and Codola tephras are physically correlated – corresponding to the Greenland interstadials 10–9 and 5. In eastern Europe, the stratigraphic and chronometric data seem to indicate an earlier appearance of the Early Upper Palaeolithic industries, which would predate of two millennia at least the overlying CI tephra. The tephrostratigraphic correlation indicates that in both regions the innovations connected with the so-called Early Upper Palaeolithic – encompassing subsistence strategy and stone tool technology – appeared and evolved during one of the most unstable climatic phases of the Last Glacial period. On this basis, the marked environmental unpredictability characterising this time-span is seen as a potential ecological factor involved in the cultural changes observed. 相似文献
198.
Patricia A. Perlock Pablo J. González Kristy F. Tiampo Gema Rodríguez-Velasco Sergey Samsonov José Fernández 《Pure and Applied Geophysics》2008,165(8):1531-1554
Differential interferometry is a very powerful tool for detecting changes in the Earth’s crust where coherence conditions
are good, but is difficult to employ in some volcanic areas due to dense vegetation. We apply two differential InSAR methods
using the time series associated with the interferograms to perform a phase analysis on a data set for La Palma island (Canary
Islands) from the ERS-1 and ERS-2 European Space Agency (ESA) satellites for the time period 1992 to 2000. Both methods involve
choosing a master image from the database and creating a series of interferograms with respect to this image. The “Coherent
Pixel Time Series” (CPTS) technique chooses pixels with good average coherence, aligns the unwrapped interferograms with a
stable area and then performs an inversion to calculate the linear velocity to quantify the deformation. The Coherent Target
Modeling (CTM) method calculates the temporal coherence of each pixel to identify stable targets and then determines the best
velocity for each pixel by using a linear fit that maximizes the temporal coherence. Using these two methods we have been
able to detect deformation on La Palma Island that has been previously undetectable by conventional InSAR methods. There is
a roughly circular region on the Southern part of the island that is actively deforming at ~ −4 to −8 mm/yr. This region is
located near the Teneguia valcano, the host of the last known eruption on La Palma in 1971. A thorough investigation of the
possible sources for this deformation revealed that it was most likely created by a subsurface thermal source. 相似文献
199.
Jan Pietroń Jeffrey A. Nittrouer Sergey R. Chalov Tian Y. Dong Nikolay Kasimov Galina Shinkareva Jerker Jarsjö 《水文研究》2018,32(2):278-292
The Selenga River delta (Russia) is a large (>600 km2) fluvially dominated fresh water system that transfers water and sediment from an undammed drainage basin into Lake Baikal, a United Nations Educational, Scientific, and Cultural Organization World Heritage Site. Through sedimentation processes, the delta and its wetlands provide important environmental services, such as storage of sediment‐bound pollutants (e.g., metals), thereby reducing their input to Lake Baikal. However, in the Selenga River delta and many other deltas of the world, there is a lack of knowledge regarding impacts of potential shifts in the flow regime (e.g., due to climate change and other anthropogenic impacts) on sedimentation processes, including sediment exchanges between deltaic channels and adjacent wetlands. This study uses field measurements of water velocities and sediment characteristics in the Selenga River delta, investigating conditions of moderate discharge, which have become more frequent over the past decades (at the expense of peak flows, Q > 1,350 m3 s?1). The aims are to determine if the river system under moderate flow conditions is capable of supporting sediment export from the main distributary channels of the delta to the adjacent wetlands. The results show that most of the deposited sediment outside of the deltaic channels is characterized by a large proportion of silt and clay material (i.e., <63 μm). For example, floodplain lakes function as sinks of very fine sediment (e.g., 97% of sediment by weight < 63 μm). Additionally, bed material sediment is found to be transported outside of the channel margins during conditions of moderate and high water discharge conditions (Q ≥ 1,000 m3 s?1). Submerged banks and marshlands located in the backwater zone of the delta accumulate sediment during such discharges, supporting wetland development. Thus, these regions likely sequester various metals bound to Selenga River sediment. 相似文献
200.
Two prognostic experiments taking into account real atmospheric forcing for 2006 and 2011 were carried out based on the eddy-resolving numerical model with a horizontal resolution of 1.6 km for the Black Sea. The main dynamic features such as the Rim Current, the Sevastopol, and Batumi anticyclones are reproduced in both experiments. The model results are confirmed via observation data. We accomplished the analysis of simulated circulation and energetics. The results demonstrate that both the vertical viscosity and vertical diffusion along with the energy inflow from the wind have been the main contributors to the annual and seasonal budgets of kinetic and potential energies of the Black Sea circulation. It is shown that two regimes of the Black Sea general circulation are implemented depending on a magnitude of wind contribution to the kinetic energy in winter. Intensive mesoscale eddy formation was observed along the Anatolian, Caucasian, and Crimean coasts. The analysis of the Black Sea circulation and eddy energetics allowed us to conclude that the generation and development of the mesoscale coastal eddies is associated with the barotropic instability in case of intensive coastal currents and is associated with both the barotropic and baroclinic instability in case of weak coastal currents. 相似文献