全文获取类型
收费全文 | 318篇 |
免费 | 18篇 |
国内免费 | 20篇 |
专业分类
测绘学 | 6篇 |
大气科学 | 30篇 |
地球物理 | 90篇 |
地质学 | 132篇 |
海洋学 | 24篇 |
天文学 | 33篇 |
自然地理 | 41篇 |
出版年
2024年 | 2篇 |
2022年 | 4篇 |
2021年 | 11篇 |
2020年 | 17篇 |
2019年 | 15篇 |
2018年 | 14篇 |
2017年 | 10篇 |
2016年 | 11篇 |
2015年 | 17篇 |
2014年 | 13篇 |
2013年 | 26篇 |
2012年 | 22篇 |
2011年 | 19篇 |
2010年 | 16篇 |
2009年 | 18篇 |
2008年 | 21篇 |
2007年 | 23篇 |
2006年 | 12篇 |
2005年 | 11篇 |
2004年 | 11篇 |
2003年 | 8篇 |
2002年 | 12篇 |
2001年 | 5篇 |
2000年 | 6篇 |
1999年 | 3篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1996年 | 5篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有356条查询结果,搜索用时 31 毫秒
51.
Application of the Ordered Weighted Averaging (OWA) method to the Caspian Sea conflict 总被引:1,自引:0,他引:1
Hojjat Mianabadi Majid Sheikhmohammady Erik Mostert Nick Van de Giesen 《Stochastic Environmental Research and Risk Assessment (SERRA)》2014,28(6):1359-1372
This study proposes a promising allocation mechanism of the Caspian Sea natural resources, which are presently shared among five countries. To date, these nations have been unable to reach an allocation agreement. We apply a methodology to propose the most appropriate solution under different risk attitudes of the states. This research is different from other studies regarding the Caspian Sea negotiations in that it employs risk-based fuzzy multi attribute decision making methods for simulating the risk attitudes or optimism/pessimism degrees of the decision makers. The ordered weighted averaging (OWA) approach, which considers the optimism/pessimism degree quantitatively, is used to take into account the effects of different risk attitudes of the negotiators on the final outcome. We demonstrate how one could obtain a range of alternatives under different multi attribute and risk attitudes. The induced OWA (IOWA) method is also used to determine the relative power of these states bordering the Caspian Sea by considering several attributes, including different risk attitudes of agents. Results indicate that taking into account the risk attitude (prone, neutral, averse) of the states can affect the overall ranking of the proposed solutions. The findings from this study may facilitate negotiation regarding the most preferred allocation mechanism for the Caspian Sea. 相似文献
52.
Alternative water management options to reduce vulnerability for climate change in the Netherlands 总被引:1,自引:0,他引:1
Urbanization, land subsidence and sea level rise will increase vulnerability of the urbanized low-lying areas in the western
part of the Netherlands. In this article possibilities are explored to reduce vulnerability of these areas by implementing
alternative water management options. Two main water management fields are distinguished, water supply and flood control.
A four-component vulnerability framework is presented that includes threshold capacity, coping capacity, recovery capacity,
and adaptive capacity. By using the vulnerability framework it is shown that current water supply and flood control strategies
in the Netherlands focus on increasing threshold capacity by constructing higher and stronger dikes, improved water storage
and delivery infrastructure. A complete vulnerability decreasing strategy requires measures that include all four capacities.
Flood damage reduction, backup water supply systems and emergency plans are measures that can contribute to increasing coping
capacity. Recovery capacity can be increased by multi-source water supply, insurance, or establishing disaster funds. Adaptive
capacity can be developed by starting experiments with new modes of water supply and urbanization. Including all four components
of the vulnerability framework enables better understanding of water and climate related vulnerability of urban areas and
enables developing more complete water management strategies to reduce vulnerability. 相似文献
53.
Nikolay G. Granin Sergey I. Muyakshin Mikhail M. Makarov Konstantin M. Kucher Il’ya A. Aslamov Liba Z. Granina Igor B. Mizandrontsev 《Geo-Marine Letters》2012,32(5-6):427-436
Methane bubble fluxes in gas flares from bottom sediments in Lake Baikal were estimated for the first time using hydroacoustic methods. Earlier work has demonstrated the occurrence of gas seeps both inside and outside of areas where bottom simulating reflectors were identified in seismic profiles. Fluxes ranged from 14 to 216 tons per year, with the flux for the entire area of the central and southern basins ranging from 1,400 to 2,800 tons per year. Comparison with other water bodies showed that fluxes from the most intensive Baikal flares were similar to those in the Norwegian and Okhotsk seas. Gas hydrates decompose at the lower boundary of the gas hydrate stability zone due to sedimentation. Calculation of the amount of methane produced due to sedimentation gave a total of between 2,600 and 14,000 tons per year for the central and southern basins of the lake. Based on rough estimation, the total flux from shallow- and deep-water gas seeps is similar to the amount of methane produced due to sedimentation. This suggests that gas hydrates possibly occupy much more than 10?% of the pore volume near the base of the gas hydrate stability zone, or that there are other reasons for gas hydrate dissociation and bubble flux from these bottom sediments. 相似文献
54.
A large-scale avalanche of Earth material is modeled here as a granular flow using a distinct element numerical model PFC
2D. Such failures occur in a variety of geological settings and are known to occur frequently over geologic time-scales transporting
significant volumes of material basinward. Despite this, they remain poorly understood. The model used here begins with a
listric failure, typical of the flank collapse of a volcanic cone, and describes the movement of an assembly of several thousand
particles from failure to deposition. Within the model, each particle possesses its own material properties and interacts
with its immediate neighbors and/or the basal boundary during emplacement. The general mechanics of the particle assembly
are observed by monitoring the stresses, displacements, and velocities of distinct sections of the avalanche body. We monitor
the avalanches’ energy regime (e.g., gravitational influence, energy dissipation by friction, kinetic energy evolution, and
avalanche body strain). The addition of colored markers of varying geometry to the pre-failure avalanche was also used to
make qualitative observations on the internal deformation that occurs during avalanche emplacement. A general stretching and
thinning of the avalanche is observed. Monitoring of vertical and horizontal variations in stress, strain, porosity, and relative
particle stability indicate that the lower more proximal sections of the avalanche are subject to higher stresses. These stresses
are observed to be most significant during the initial phases of failure but decline thereafter; a situation likely to be
conducive to block fragmentation and in developing a basal shear layer in real-world events. The model also shows how an avalanche
which is initially influenced purely by gravity (potential energy) develops into a fully flowing assemblage as downslope momentum
is gained and kinetic energy increases. The horizontal transition where the failure meets the run-out surface is recognized
as a key area in emplacement evolution. The model has particular relevance to volcanic flank collapses and consequently the
implications of the model to these types of failure and the geological products that result are considered in detail although
the model is relevant to any form of large-scale rock or debris avalanche. 相似文献
55.
Citation Abrahart, R.J. & Mount, N.J. (2011) Discussion of “Neuro-fuzzy models employing wavelet analysis for suspended sediment concentration prediction in rivers by S.A. Mirgagheri et al. (2010, Hydrol. Sci. J. 55(7), 1175–1189).” Hydrol. Sci. J. 56(7), 1325–1329. 相似文献
56.
Chaofan LI Riyu LU Nick DUNSTONE Adam A.SCAIFE Philip E.BETT Fei ZHENG 《大气科学进展》2021,38(12):2055-2066
During June and July of 2020, the Yangtze River basin suffered from extreme mei-yu rainfall and catastrophic flooding. This study explores the seasonal predictability and associated dynamical causes for this extreme Yangtze River rainfall event, based on forecasts from the Met Office GloSea5 operational forecast system. The forecasts successfully predicted above-average rainfall over the Yangtze River basin, which arose from the successful reproduction of the anomalous western North Pacific subtropical high (WNPSH). Our results indicate that both the Indian Ocean warm sea surface temperature (SST) and local WNP SST gradient were responsible for the westward extension of the WNPSH, and the forecasts captured these tropical signals well. We explore extratropical drivers but find a large model spread among the forecast members regarding the meridional displacements of the East Asian mid-latitude westerly jet (EAJ). The forecast members with an evident southward displacement of the EAJ favored more extreme Yangtze River rainfall. However, the forecast Yangtze River rainfall anomaly was weaker compared to that was observed and no member showed such strong rainfall. In observations, the EAJ displayed an evident acceleration in summer 2020, which could lead to a significant wind convergence in the lower troposphere around the Yangtze River basin, and favor more mei-yu rainfall. The model forecast failed to satisfactorily reproduce these processes. This difference implies that the observed enhancement of the EAJ intensity gave a large boost to the Yangtze River rainfall, hindering a better forecast of the intensity of the event and disaster mitigation. 相似文献
57.
58.
Nick E. Timms Peter D. Kinny Steven M. Reddy Katy Evans Chris Clark Dave Healy 《Chemical Geology》2011,280(1-2):33-46
A zircon grain in an orthopyroxene–garnet–phlogopite–zircon–rutile-bearing xenolith from Udachnaya, Siberia, preserves a pattern of crystallographic misorientation and subgrain microstructure associated with crystal–plastic deformation. The zircon grain records significant variations in titanium (Ti) from 2.6 to 30 ppm that corresponds to a difference in calculated Ti-in-zircon temperatures of over several hundred degrees Celsius. The highest Ti concentration is measured at subgrain centres (30 ppm), and Ti is variably depleted at low-angle boundaries (down to 2.6 ppm). Variations in cathodoluminescence coincide with the deformation microstructure and indicate localised, differential enrichment of rare earth elements (REE) at low-angle boundaries. Variable enrichment of U and Th and systematic increase of Th/U from 1.61 to 3.52 occurs at low-angle boundaries. Individual SHRIMP-derived U–Pb ages from more deformed zones (mean age of 1799 ± 40, n = 22) are systematically younger than subgrain cores (mean age of 1851 ± 65 Ma, n = 7), and indicate that open system behaviour of Ti–Th–U occurred shortly after zircon growth, prior to the accumulation of significant radiogenic Pb. Modelling of trace-element diffusion distances for geologically reasonable thermal histories indicates that the observed variations are ~ 5 orders of magnitude greater than can be accounted for by volume diffusion. The data are best explained by enhanced diffusion of U, Th and Ti along deformation-related fast-diffusion pathways, such as dislocations and low-angle (< 5°) boundaries. These results indicate chemical exchange between zircon and the surrounding matrix and show that Ti-in-zircon thermometry and U–Pb geochronology from deformed zircon may not yield information relating to the conditions and timing of primary crystallisation. 相似文献
59.
New friends in new places: Network formation during the migration process among Poles in the UK 总被引:1,自引:0,他引:1
This paper contributes to on-going work that seeks to understand the dynamic nature of immigrant social network formation. We explore three propositions, derived from the literature, that might be expected to characterise the ways in which migrant associational ties evolve during and immediately after arrival in their destination country. Evidence is drawn from 42 interviews conducted between January and December 2008 with predominantly Polish migrants to the UK (28) as well as domestic service providers (14). In agreement with the existing literature on immigrant social network formation we find that weak associational ties between migrants are locally dense and rapidly formed. More surprisingly, we also find that the Poles in our sample from lower socio-economic groups tended to rely heavily upon weak associational ties while higher socio-economic group Poles tended to rely on associations made through their employing institutions. This illustrates the importance of socio-economic status in framing co-ethnic migrant network formation. This is significant because we also find that weak associational ties are not unambiguously beneficial to lower socio-economic group migrants who tend to (have to be) more compromising about, and therefore more compromised by, the social ‘friendships’ that result. 相似文献
60.