全文获取类型
收费全文 | 286篇 |
免费 | 14篇 |
国内免费 | 8篇 |
专业分类
测绘学 | 5篇 |
大气科学 | 29篇 |
地球物理 | 105篇 |
地质学 | 97篇 |
海洋学 | 23篇 |
天文学 | 23篇 |
综合类 | 2篇 |
自然地理 | 24篇 |
出版年
2023年 | 2篇 |
2021年 | 3篇 |
2020年 | 5篇 |
2019年 | 3篇 |
2018年 | 12篇 |
2017年 | 8篇 |
2016年 | 10篇 |
2015年 | 10篇 |
2014年 | 11篇 |
2013年 | 33篇 |
2012年 | 16篇 |
2011年 | 17篇 |
2010年 | 18篇 |
2009年 | 11篇 |
2008年 | 13篇 |
2007年 | 8篇 |
2006年 | 17篇 |
2005年 | 14篇 |
2004年 | 14篇 |
2003年 | 11篇 |
2002年 | 8篇 |
2001年 | 7篇 |
2000年 | 9篇 |
1999年 | 4篇 |
1998年 | 9篇 |
1997年 | 3篇 |
1995年 | 6篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 4篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有308条查询结果,搜索用时 187 毫秒
41.
Michael V.W. Cuttler Jeff E. Hansen Ryan J. Lowe Julie A. Trotter Malcolm T. McCulloch 《地球表面变化过程与地形》2019,44(2):552-564
Reef-associated landforms are coupled to the health of the reef ecosystem which produces the sediment that forms and maintains these landforms. However, this connection can make reef-fronted coastlines sensitive to the impacts of climate change, given that any decline in ecosystem health (e.g. decreasing sediment supply) or changes to physical processes (e.g. sea level rise, increasing wave energy) could drive the sediment budgets of these systems into a net erosive state. Therefore, knowledge of both the sediment sources and transport mechanisms is required to predict the sensitivity of reef-associated landforms to future climate change. Here, we examine the benthic habitat composition, sediment characteristics (composition, texture, and age), and transport mechanisms and pathways to understand the interconnections between coastal morphology and the reef system at Tantabiddi, Ningaloo Reef, Western Australia. Benthic surveys and sediment composition analysis revealed that although live coral accounts for less than 5% of the benthic cover, coral is the dominant sediment constituent (34% on average). Sediment ages (238U/230Th) were mostly found to be thousands of years old, suggesting that the primary sediment source is relic reef material (e.g. Holocene reef framework). Sediment transport across the lagoon was quantified through measurements of ripple migration rates, which were found to be shoreward migrating and responsible for feeding the large shoreline salient in the lee of the reef. The derived sediment fluxes were comparable with previously measured rates of sediment production by bioerosion. These results suggest that sediment budgets of systems dependent on old (>103 years) source materials may be more resilient to climate change as present-day reef health and community composition (i.e. sources of ‘new’ carbonate production) have limited influence on sediment supply. Therefore, the vulnerability of reef-associated landforms in these systems will be dictated by future changes to mechanisms of sediment generation (e.g. bioerosion) and/or physical processes. © 2018 John Wiley & Sons, Ltd. 相似文献
42.
43.
Geostatistical models should be checked to ensure consistency with conditioning data and statistical inputs. These are minimum
acceptance criteria. Often the first and second-order statistics such as the histogram and variogram of simulated geological
realizations are compared to the input parameters to check the reasonableness of the simulation implementation. Assessing
the reproduction of statistics beyond second-order is often not considered because the “correct” higher order statistics are
rarely known. With multiple point simulation (MPS) geostatistical methods, practitioners are now explicitly modeling higher-order
statistics taken from a training image (TI). This article explores methods for extending minimum acceptance criteria to multiple
point statistical comparisons between geostatistical realizations made with MPS algorithms and the associated TI. The intent
is to assess how well the geostatistical models have reproduced the input statistics of the TI; akin to assessing the histogram
and variogram reproduction in traditional semivariogram-based geostatistics. A number of metrics are presented to compare
the input multiple point statistics of the TI with the statistics of the geostatistical realizations. These metrics are (1)
first and second-order statistics, (2) trends, (3) the multiscale histogram, (4) the multiple point density function, and
(5) the missing bins in the multiple point density function. A case study using MPS realizations is presented to demonstrate
the proposed metrics; however, the metrics are not limited to specific MPS realizations. Comparisons could be made between
any reference numerical analogue model and any simulated categorical variable model. 相似文献
44.
Aleksey S. Telyakovskiy Gastão A. Braga Satoko Kurita Jeff Mortensen 《Advances in water resources》2010
For certain initial and boundary conditions the Boussinesq equation, a nonlinear partial differential equation describing the flow of water in unconfined aquifers, can be reduced to a boundary value problem for a nonlinear ordinary differential equation. Using Song et al.'s (2007) [7] approach, we show that for zero head initial condition and power-law flux boundary condition at the inlet boundary, the solution in the form of power series can be obtained with Barenblatt's (1990) [2] rescaling procedure applied to the power series solution obtained in Song et al. (2007) [7] for the power-law head boundary condition. Polynomial approximations can then be obtained by taking terms from the power series. Although for a small number of terms the newly obtained approximations may be worse than polynomial approximations obtained by other techniques, any desired accuracy can be achieved by taking more terms from the power series. 相似文献
45.
Past research has demonstrated the dramatic effects that variations in suspended clay can have on the properties of flow by producing a range of transitional flows between turbulent and laminar states, depending on clay concentration and fluid shear. Past studies have been restricted to kaolinite flows, a clay mineral that has relatively weak cohesive properties. This paper extends these studies to suspension flows of bentonite, a clay mineral that attains higher viscosities at far lower volumetric concentrations within a flow. The results show that the types of transitional flow behaviour recognized in past studies can also be found in bentonite suspension flows, but at lower suspended sediment concentrations, thus demonstrating an even more dramatic effect on flow properties, and potentially on sediment transport and resulting bed morphology, than kaolinite flows. The paper proposes new stability diagrams for the phase space of bentonite flows and compares these to past work on kaolinite suspension flows. These new data suggest that the transitional‐flow Reynolds number can be used to delineate the types of transitional flow across different clay types and assess modern and ancient clay‐suspension flows. © 2016 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd. 相似文献
46.
Jeff Ching-Fu Hsieh Susanna M. Cramb James M. McGree Nathan A. M. Dunn Peter D. Baade Kerrie L. Mengersen 《Stochastic Environmental Research and Risk Assessment (SERRA)》2016,30(1):155-165
Although mammography screening programs aim to diagnose breast cancer at an early stage, not all tumours are detected during the regular screening examination. This study examines the influence of various characteristics, including geographical residence, on the survival between screen- and interval-detected breast cancers among participants of a public population-based breast screening program in Queensland, Australia. The investigation was performed using the linked population-based datasets from BreastScreen Queensland and the Queensland Cancer Registry for the period of 1997–2008 for women aged 40–89 years at diagnosis. A Bayesian spatial relative survival modelling approach that accommodates rare outcomes in small geographic regions was adopted, with the use of Markov chain Monte Carlo computation, to evaluate the relative excess risk of breast cancer. In the multivariate Bayesian spatial model, higher relative excess risk of mortality was observed in interval-detected cancer (RER = 1.59, 95 % credible interval = [1.33, 1.89]) compared to screen-detected cancer. Higher cancer survival among the study cohort was also observed among younger women (40–59 years), those of non-Indigenous ethnicity, with localised (stage I) tumour stage as well as those not in the work force. There was no independent association with marital status. Moreover, there was no substantive evidence of either measured geographical or latent random spatial inequalities in survival among screening participants across Queensland, meaning the higher survival for screen-detected breast cancer patients compared to interval-detected women was consistent across the state. These results provide suggestive evidence supporting the effectiveness of the BreastScreen Queensland screening program in reaching socio-economically disadvantaged women as well as those living in rural and remote areas of the state, but also highlights the need for any interval cancer awareness programs to be geographically widespread. 相似文献
47.
48.
This study examines the challenges of achieving sustainable management of the world's largest mangrove forest, the Sundarbans, in Bangladesh. The Sundarbans is currently managed by the Bangladesh Department of Forest, under a state property‐rights regime, while our study explores an alternative property‐rights regime. We employed a mixed‐method approach to examine the prospects of alternative management and livelihood strategies to achieve sustainability. Both focus groups and household surveying were used to assess the opportunities for, and barriers to, achieving sustainability. It was found that two conflicting groups—forest‐dependent communities and foresters—are responsible for policy failures due to the absence of power‐sharing arrangements, nor is it likely a common property‐rights regime will be enough to cap degradation and achieve sustainability, while supply‐and‐demand policy interventions may well could help achieve sustainable management of the Sundarbans. 相似文献
49.
Jeff Onsted Keith C. Clarke 《International journal of geographical information science》2013,27(5):881-898
This research sought to understand the role that differentially assessed lands (lands in the United States given tax breaks in return for their guarantee to remain in agriculture) play in influencing urban growth. Our method was to calibrate the SLEUTH urban growth model under two different conditions. The first used an excluded layer that ignored such lands, effectively rendering them available for development. The second treated those lands as totally excluded from development. Our hypothesis was that excluding those lands would yield better metrics of fit with past data. Our results validate our hypothesis since two different metrics that evaluate goodness of fit both yielded higher values when differentially assessed lands are treated as excluded. This suggests that, at least in our study area, differential assessment, which protects farm and ranch lands for tenuous periods of time, has indeed allowed farmland to resist urban development. Including differentially assessed lands also yielded very different calibrated coefficients of growth as the model tried to account for the same growth patterns over two very different excluded areas. Excluded layer design can greatly affect model behavior. Since differentially assessed lands are quite common through the United States and are often ignored in urban growth modeling, the findings of this research can assist other urban growth modelers in designing excluded layers that result in more accurate model calibration and thus forecasting. 相似文献
50.
Timothy R. H. Davies Jeff Warburton Stuart A. Dunning Alodie A. P. Bubeck 《地球表面变化过程与地形》2013,38(11):1261-1268
Threlkeld Knotts (c. 500 m above sea level) in the English Lake District has hitherto been considered to be a glacially‐modified intrusion of microgranite. However, its surface features are incompatible with glacial modification; neither can these nor the subsurface structures revealed by ground‐penetrating radar (GPR) be explained by post‐glacial subaerial processes acting on a glacially‐modified microgranite intrusion. Here we re‐interpret Threlkeld Knotts as a very large post‐glacial landslide involving the microgranite, with an estimated volume of about 4 × 107 m3. This interpretation is tested against published and recent information on the geology of the site, the glacial geomorphic history of the area and newly‐acquired GPR data. More than 60 large post‐Last Glacial Maximum (LGM) rock–slope failures have significantly modified the glaciated landscape of the Lake District; this is one of the largest. Recognition of this major landslide deposit in such a well‐studied environment highlights the need to continuously re‐examine landscapes in the light of increasing knowledge of geomorphic processes and with available technology in currently active or de‐glaciating environments. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献