全文获取类型
收费全文 | 2362篇 |
免费 | 95篇 |
国内免费 | 32篇 |
专业分类
测绘学 | 91篇 |
大气科学 | 186篇 |
地球物理 | 507篇 |
地质学 | 786篇 |
海洋学 | 178篇 |
天文学 | 514篇 |
综合类 | 8篇 |
自然地理 | 219篇 |
出版年
2022年 | 27篇 |
2021年 | 23篇 |
2020年 | 35篇 |
2019年 | 34篇 |
2018年 | 58篇 |
2017年 | 75篇 |
2016年 | 56篇 |
2015年 | 63篇 |
2014年 | 65篇 |
2013年 | 107篇 |
2012年 | 61篇 |
2011年 | 106篇 |
2010年 | 93篇 |
2009年 | 116篇 |
2008年 | 106篇 |
2007年 | 91篇 |
2006年 | 89篇 |
2005年 | 56篇 |
2004年 | 70篇 |
2003年 | 53篇 |
2002年 | 89篇 |
2001年 | 45篇 |
2000年 | 58篇 |
1999年 | 40篇 |
1998年 | 41篇 |
1997年 | 43篇 |
1996年 | 25篇 |
1995年 | 35篇 |
1994年 | 21篇 |
1993年 | 24篇 |
1992年 | 31篇 |
1991年 | 17篇 |
1990年 | 20篇 |
1989年 | 17篇 |
1988年 | 20篇 |
1987年 | 28篇 |
1986年 | 27篇 |
1985年 | 36篇 |
1984年 | 48篇 |
1983年 | 35篇 |
1982年 | 56篇 |
1981年 | 35篇 |
1980年 | 39篇 |
1979年 | 41篇 |
1978年 | 26篇 |
1977年 | 29篇 |
1976年 | 25篇 |
1975年 | 23篇 |
1974年 | 29篇 |
1973年 | 18篇 |
排序方式: 共有2489条查询结果,搜索用时 15 毫秒
81.
Water levels in cryoconite holes were monitored at high resolution over a 3‐week period on Austre Brøggerbreen (Svalbard). These data were combined with melt and energy balance modelling, providing insights into the evolution of the glacier's near‐surface hydrology and confirming that the hydrology of the near‐surface, porous ice known as the ‘weathering crust’ is dynamic and analogous to a shallow‐perched aquifer. A positive correlation between radiative forcing of melt and drainage efficiency was found within the weathering crust. This likely resulted from diurnal contraction and dilation of interstitial pore spaces driven by variations in radiative and turbulent fluxes in the surface energy balance, occasionally causing ‘sudden drainage events’. A linear decrease in water levels in cryoconite holes was also observed and attributed to cumulative increases in near‐surface ice porosity over the measurement period. The transport of particulate matter and microbes between cryoconite holes through the porous weathering crust is shown to be dependent upon weathering crust hydraulics and particle size. Cryoconite holes therefore yield an indication of the hydrological dynamics of the weathering crust and provide long‐term storage loci for cryoconite at the glacier surface. This study highlights the importance of the weathering crust as a crucial component of the hydrology, ecology and biogeochemistry of the glacier ecosystem and glacierized regions and demonstrates the utility of cryoconite holes as natural piezometers on glacier surfaces. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
82.
Modelling groundwater/surface water interaction in a managed riparian chalk valley wetland 下载免费PDF全文
Understanding hydrological processes in wetlands may be complicated by management practices and complex groundwater/surface water interactions. This is especially true for wetlands underlain by permeable geology, such as chalk. In this study, the physically based, distributed model MIKE SHE is used to simulate hydrological processes at the Centre for Ecology and Hydrology River Lambourn Observatory, Boxford, Berkshire, UK. This comprises a 10‐ha lowland, chalk valley bottom, riparian wetland designated for its conservation value and scientific interest. Channel management and a compound geology exert important, but to date not completely understood, influences upon hydrological conditions. Model calibration and validation were based upon comparisons of observed and simulated groundwater heads and channel stages over an equally split 20‐month period. Model results are generally consistent with field observations and include short‐term responses to events as well as longer‐term seasonal trends. An intrinsic difficulty in representing compressible, anisotropic soils limited otherwise excellent performance in some areas. Hydrological processes in the wetland are dominated by the interaction between groundwater and surface water. Channel stage provides head boundaries for broad water levels across the wetland, whilst areas of groundwater upwelling control discrete head elevations. A relic surface drainage network confines flooding extents and routes seepage to the main channels. In‐channel macrophyte growth and its management have an acute effect on water levels and the proportional contribution of groundwater and surface water. The implications of model results for management of conservation species and their associated habitats are discussed. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
83.
Joseph Awetori Yaro 《GeoJournal》2010,75(2):199-214
Land in most of Africa is controlled under the customary tenure system which is governed by well intentioned social and cultural
rules meant to grant equal access to families within groups with common interest in land. Rapid changes in the domestic situation
of countries resulting from both refractions of policies and influences from the global economy and emerging complexities
within the local socio-economic context has altered the traditional land tenure systems in most parts of Africa. In the rural
setting and for agricultural purposes, the customary tenure system seems to be crumbling slowly, while in the urban centres
and for housing, industrial and commercial purposes the system has collapsed in favour of a commoditised one. The emerging
patterns of access in Northern Ghana show growing inequalities in access, control and ownership. There is the need for a new
architecture of land rights negotiated by a participatory process and regulated by both state and traditional institutions. 相似文献
84.
Jeffrey Robert Thompson 《Geological Journal》2015,50(4):550-551
85.
86.
87.
The Timor Orogen represents one of the youngest arc–continent collisions exposed on the Earth. It has the potential to provide some of the key parameters about how this style of orogeny evolves. However, the metamorphic age of the highest-grade rocks formed in the collision remains controversial. Using U–Th–Pb dating of monazite from amphibolite-grade sillimanite and garnet-bearing schists we show the peak metamorphism occurred at 5.5–4.7 Ma. The young age of the monazite and the presence of significant amounts of common Pb required the development of a new protocol to simultaneously account for the 230Th disequilibrium and the 207Pb common Pb correction. The new estimate of metamorphic age is consistent with the estimates based on plate reconstructions for the initiation of arc–continent collision in East Timor. The metamorphic event is a result of this collision. 相似文献
88.
With the escalating costs of landslides, the challenge for local authorities is to develop institutional arrangements for landslide risk management that are viewed as efficient, feasible and fair by those affected. For this purpose, the participation of stakeholders in the decision-making process is mandated by the European Union as a way of improving its perceived legitimacy and transparency. This paper reports on an analytical-deliberative process for selecting landslide risk mitigation measures in the town of Nocera Inferiore in southern Italy. The process was structured as a series of meetings with a group of selected residents and several parallel activities open to the public. The preparatory work included a literature/media review, semi-structured interviews carried out with key local stakeholders and a survey eliciting residents’ views on landslide risk management. The main point of departure in the design of this process was the explicit elicitation and structuring of multiple worldviews (or perspectives) among the participants with respect to the nature of the problem and its solution. Rather than eliciting preferences using decision analytical methods (e.g. utility theory or multi-criteria evaluation), this process built on a body of research—based on the theory of plural rationality—that has teased out the limited number of contending and socially constructed definitions of problem-and-solution that are able to achieve viability. This framing proved effective in structuring participants’ views and arriving at a compromise recommendation (not, as is often aimed for, a consensus) on measures for reducing landslide risk. Experts played a unique role in this process by providing a range of policy options that corresponded to the different perspectives held by the participants. 相似文献
89.
Khan Mohd Yawar Ali Khan Babra Chakrapani Govind Joseph 《Arabian Journal of Geosciences》2016,9(8):1-11
Arabian Journal of Geosciences - A comprehensive study on the chemical considerations of thermal waters (springs and geothermal wells) on the performance of solute geothermometers in predicting the... 相似文献
90.
Assessment of soil erosion in a tropical mountain river basin of the southern Western Ghats,India using RUSLE and GIS 总被引:1,自引:0,他引:1
Revised Universal Soil Loss Equation(RUSLE) model coupled with transport limited sediment delivery(TLSD) function was used to predict the longtime average annual soil loss, and to identify the critical erosion-/deposition-prone areas in a tropical mountain river basin, viz., Muthirapuzha River Basin(MRB; area=271.75 km~2), in the southern Western Ghats, India. Mean gross soil erosion in MRB is 14.36 t ha~(-1) yr~(-1), whereas mean net soil erosion(i.e., gross erosion-deposition) is only 3.60 t ha~(-1) yr~(-1)(i.e., roughly 25% of the gross erosion). Majority of the basin area(~86%) experiences only slight erosion(5 t ha~(-1) yr~(-1)), and nearly 3% of the area functions as depositional environment for the eroded sediments(e.g., the terraces of stream reaches, the gentle plains as well as the foot slopes of the plateau scarps and the terrain with concordant summits). Although mean gross soil erosion rates in the natural vegetation belts are relatively higher, compared to agriculture, settlement/built-up areas and tea plantation, the sediment transport efficiency in agricultural areas and tea plantation is significantly high,reflecting the role of human activities on accelerated soil erosion. In MRB, on a mean basis, 0.42 t of soil organic carbon(SOC) content is being eroded per hectare annually, and SOC loss from the 4th order subbasins shows considerable differences, mainly due to the spatial variability in the gross soil erosion rates among the sub-basins. The quantitative results, on soil erosion and deposition, modelled using RUSLE and TLSD, are expected to be beneficial while formulating comprehensive land management strategies for reducing the extent of soil degradation in tropical mountain river basins. 相似文献