全文获取类型
收费全文 | 395篇 |
免费 | 20篇 |
国内免费 | 16篇 |
专业分类
测绘学 | 9篇 |
大气科学 | 2篇 |
地球物理 | 173篇 |
地质学 | 112篇 |
海洋学 | 36篇 |
天文学 | 3篇 |
综合类 | 4篇 |
自然地理 | 92篇 |
出版年
2023年 | 7篇 |
2022年 | 6篇 |
2021年 | 4篇 |
2020年 | 1篇 |
2019年 | 10篇 |
2018年 | 6篇 |
2017年 | 11篇 |
2016年 | 5篇 |
2015年 | 5篇 |
2014年 | 18篇 |
2013年 | 15篇 |
2012年 | 7篇 |
2011年 | 17篇 |
2010年 | 7篇 |
2009年 | 28篇 |
2008年 | 40篇 |
2007年 | 24篇 |
2006年 | 29篇 |
2005年 | 19篇 |
2004年 | 15篇 |
2003年 | 14篇 |
2002年 | 13篇 |
2001年 | 12篇 |
2000年 | 16篇 |
1999年 | 10篇 |
1998年 | 5篇 |
1997年 | 7篇 |
1996年 | 5篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 11篇 |
1992年 | 9篇 |
1991年 | 7篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有431条查询结果,搜索用时 15 毫秒
171.
K. V. S. R. Prasad S. V. V. Arun Kumar Ch. Venkata Ramu P. Sreenivas 《Natural Hazards》2009,49(2):347-360
The nearshore parameters, viz., wave runup, wave setup, and wave energy have been estimated during storm and normal conditions
of SW monsoon (June–September) and NE monsoon (November–February) by empirical parameterization along Visakhapatnam coast.
These results were compared with the field observations during three storms of SW monsoon season in the year 2007. The higher
nearshore wave energies were observed at R.K. Beach, Jodugullapalem beach, and Sagarnagar beach during both the seasons. During
storm events, the higher wave energies associated with higher wave runups cause severe erosion along the wave convergence
zones. The storm wave runups (SWRUs) were higher at R.K. Beach, Palm beach, Jodugullapalem beach, and Sagarnagar Beach. The
yearly low wave energy was observed at Lawson’s Bay with lowest wave runup, considered as safest zone. R.K. Beach, Palm beach,
and Jodugullapalem beach are identified as vulnerable zones of wave attack. It is noteworthy that in addition to wave energies,
wave runups and wave setups also play a vital role in endangering the coast. 相似文献
172.
David J. Wachal Kenneth E. Banks Paul F. Hudak R. Daren Harmel 《Environmental Geology》2009,56(8):1615-1627
Sediment yields from natural gas well sites in Denton County, TX, USA can be substantial and warrant consideration of appropriate
erosion and sediment control best management practices (BMPs). Version 2 of the revised universal soil loss equation (RUSLE
2.0) was used to predict sediment yields and evaluate the efficiency of BMPs for multiple combinations of different land surface
conditions (soil erodibility and slope) commonly found at gas well sites in the area. Annual average sediment yield predictions
from unprotected site conditions ranged from 12.1 to 134.5 tonnes per hectare per year (t/ha/yr). Sediment yield predictions
for 1, 2, 5, and 10-year design storms ranged from 8.1 to 20.6 t/ha. When site conditions were modeled with BMPs, predicted
sediment yields were 52–93% less. A comparison of modeled efficiency values to a review of laboratory and field data suggests
that modeled (theoretical) sediment yield results with BMPs are likely best case scenarios. This study also evaluated BMPs
in the context of site management goals and implementation cost, demonstrating a practical approach for the application of
RUSLE 2.0 for managing soil loss and understanding the importance of selecting appropriate site-specific BMPs for disturbed
site conditions. 相似文献
173.
This paper presents the results of an 11-year study into mudflat elevation changes within the intertidal zone at Stert Flats in Bridgwater Bay, Somerset. This site is located in the outer Severn Estuary/inner Bristol Channel which is a macro-hypertidal regime dominated by physical processes, characterized by strong tidal currents, high turbidity and a significant degree of exposure to wind generated waves. Two transects of stakes were installed perpendicular to the coast, extending seawards 300 m from the edge of the saltmarsh onto the mudflats, against which variations in accretion or erosion could be measured. The mudflats themselves consisted of an underlying consolidated clay of Holocene age and a surface veneer of fluid mud and/or mobile sand patches which varied both spatially and temporally. Mudflat development was recorded over both short-term (monthly/seasonal) and medium-term (inter-annual) timescales. The results display a significant degree of scatter over all timescales. Such variability in response may be expected in such a dynamic system where noise can be attributed to a combination of factors such as the mobility of surface fluid mud and sand patches and the migration of the underlying ridge–runnel drainage network. Despite this, the expected short-term variations related to neap–spring tidal conditions and seasonal influences were observed at a number of locations on the transects although these were weakly expressed. The over-riding feature of the profiles is a consistent long-term trend of erosion which appears to be masking shorter term trends within the dataset. Viewed over the 11-year period, the changes in mudflat elevation closely match the pattern of the index of the North Atlantic Oscillation (NAO) during the 1990s, suggesting a strong climatic control over mudflat development on a medium-term/decadal scale. Most profiles display a strong erosional trend during the early 1990s when the NAO index was positive. The erosional trend peaked in 1995 at a time during which the values for monthly winter mean significant wave height were notably high. Between 1996 and 2001 the profiles generally record accretion and the data display significant variability. This corresponds with a shift to a strongly negative and then weakly positive NAO index phase. The fact that such a general atmospheric factor correlates so closely with medium timescale elevation change is attributed to relative weakness of biological binding and burrowing at this site, and more-so to the overwhelming dominance of the physical regime, especially the tidal current and the wind–wave regime. Both the background erosional trend and the influence of the index of the NAO in controlling mudflat evolution have important implications relating to coastal management. These are discussed in relation to coastal defence measures, morphological response to major civil engineering projects (e.g. Severn Tidal Power Barrage) and the prospect of climate change, sea-level rise and a possible increase in strength of NAO conditions in the future. 相似文献
174.
Controls of surface erosion on the evolution of the Alps: constraints from the stratigraphies of the adjacent foreland basins 总被引:5,自引:0,他引:5
F. Schlunegger 《International Journal of Earth Sciences》1999,88(2):285-304
The combined information about the stratigraphies from the foreland basins surrounding the Swiss Alps, exhumation mechanisms
and the structural evolution of the Alpine orogenic wedge allow an evaluation of the controls of erosion rates on large-scale
Alpine tectonic evolution. Volumetric data from the Molasse Basin and fining-upward trends in the Gonfolite Lombarda indicate
that at ∼20 Ma, average erosion rates in the Alps decreased by >50%. It appears that at that time, erosion rates decreased
more rapidly than crustal uplift rates. As a result, surface uplift occurred. Because of surface uplift, the drainage pattern
of the Alpine hinterland evolved from an across-strike to the present-day along-strike orientation. Furthermore, the decrease
of average erosion rates at ∼20 Ma coincides with initiation of a phase of thrusting in the Jura Mountains and the Southern
Alpine nappes at ∼50 km distance from the pre-20-Ma thrust front. Coupled erosion-mechanical models of orogens suggest that
although rates of crustal convergence decreased between the Oligocene and the present, the reduction of average erosion rates
at ∼20 Ma was high enough to have significantly influenced initiation of the state of growth of the Swiss Alps at that time.
Received: 8 June 1998 / Accepted: 30 October 1998 相似文献
175.
《国际泥沙研究》2023,38(1):49-65
Severe erosion is caused by intense rainfall in tropical regions. The erodible soil of steep hill slopes, accompanied by destruction of vegetation due to human interventions results in accelerated erosion. A sustainable and cost-effective solution such as vetiver grass (Chrysopogon zizanioides) is, thus, required to control the erosion process. In the current study, 6 small-scale glass models: 1 bare and 5 with vetiver grass, having a slope angle of 37° have been constructed. One year after planting, artificial rainfall of extremely high intensity was applied to all 6 small models and the role of vetiver canopy and roots in erosion and runoff control was observed. To see the effect of soil texture, one among these 5 models was made with silty sand and others contained sandy silt. The results demonstrated that, for sandy silt, the inclusion of vetiver reduced the soil loss by 94%–97%, and soil detachment rates were lowered by 95%. The average runoff also was reduced by 21%. The canopy cover showed a positive impact on reducing both quantities. An increase in average root diameter from 1.6 to 2.5 mm increases the soil loss due to its negative impact on added cohesion. The added cohesion showed a linearly negative correlation with soil loss. A composite system of vetiver and jute geotextile was most effective in erosion reduction among 4 vegetated models with sandy silt. Under same vetiver planting layout, the grass covered model of silty sand yielded 84% lower erosion and 62.5% lower runoff than the grass covered one with sandy silt. Thus, vetiver was more effective in erosion and runoff reduction for soil with a greater percentage of sand, and soil type dominated the erosion process. 相似文献
176.
Hongwu Zhang Guangquan Liu Chensu Zhao Luohao Zhang Qiang Zhang Heng Fu Shuai Cao 《国际泥沙研究》2023,38(1):24-32
A typical gully sub-basin with a complex geomorphological form is used to do a model test of gravity erosion of loess by considering the sequence of slopes in a prototype gully creating a sequence of underlying surface forms in the upper reaches. The results show that the runoff from heavy rainfall is the main external force for the erosion of loess, and also is an important influencing factor to stimulate and intensify the development of gravity erosion. The soil structure and the height of the... 相似文献
177.
Geomorphic considerations for erosion prediction 总被引:9,自引:0,他引:9
Current soil-erosion prediction technology addresses processes of rainsplash, overland-flow sediment transport, and rill
erosion in small watersheds. The effects of factors determining sediment yield from larger-scale drainage basins, in which
sediment movement is controlled by the combined small-scale processes and a complex set of channel and other basin-scale sediment-delivery
processes, such as soil creep, bioturbation, and accelerated erosion due to denudation of vegetation, have been poorly evaluated.
General suggestions are provided for the development of erosion-prediction technology at the geomorphic or drainage-basin
scale based on the separation of sediment-yield data for channel and geomorphic processes from those of field-scale soil loss.
An emerging technology must consider: (1) the effects on sediment yield of climate, geology and soils, topography, biotic
interactions with other soil processes, and land-use practices; (2) all processes of sediment delivery to a channel system;
and (3) the general tendency in most drainage basins for progressively greater sediment storage in the downstream direction.
Received: 8 November 1995 · Accepted: 20 November 1995 相似文献
178.
179.
Erosion, sediment transportation and accumulation in rivers 总被引:8,自引:5,他引:3
N. I. ALEKSEEVSKIY K. M. BERKOVICH and R. S. CHALOV Prof. Head of the Hydrology Department Faculty of Geography Moscow State University Moscow Russia Prof. Leading researcher Lab. of Soil Erosion Fluvial Processes Faculty of Geography Moscow State University Moscow Russia Prof. Head of the Lab. of Soil Erosion Fluvial Processes Faculty of Geography Moscow State University Moscow Russia 《国际泥沙研究》2008,23(2):93-105
The present paper analyses the interrelation between erosion, sediment transportation and accumulation proposed by N. I. Makkaveyev (1908-1983) and its further development in modem studies of river channel processes in Russia. Spatio-temporal linkages between erosion and accumulation are defined considering channel processes at different scales - river longitudinal profile, channel morphological patterns, alluvial bedforms (bars, dunes) and individual sediment particles. Relations between river geomorphic activity, flow transportation capacity and sediment budgets are established (sediment input and output; channel bed erosion and sediment entrainment into flow - termination of sediment transport and its deposition). Channel planforms, floodplain segments separated by the latter and alluvial channel bedforms are shown to be geomorphic expressions of sediment transport process at different spatial and temporal scales. This paper is dedicated to the 100th anniversary of N. I. Makkaveyev, Professor of the Moscow State University, author of the book "River channel and erosion in its basin" (1955). That book is regarded in Russia as the pioneering work which initiated the complex hydrological and geographical studies of channel processes and laid a basis for the theory of unified fluvial erosion-accumulation process. 相似文献
180.
黄土丘陵小流域土地利用变化对水土流失的影响 总被引:80,自引:3,他引:80
在土壤侵蚀模型LISEM (Limburg Soil Erosion Model) 校正的基础上,模拟了陕北黄土丘陵沟壑区大南沟小流域5种土地利用方案的水土流失效应,旨在探讨土地利用变化对流域出口水土流失的影响。研究结果表明:流域出口的洪峰流速、径流总量和侵蚀总量的大小顺序为:1975年>1998年>25度退耕>20度退耕>15度退耕。1975年和1998年25度以上的陡坡耕地和休闲地均退耕还林还草,这2种土地利用格局的径流和侵蚀模拟值都显著大于3种退耕方案。在3种退耕方案中,20度和15度以上的陡坡耕地和休闲地逐步转变为果园/经济林地,3种退耕方案之间的水土流失差异不显著。相对于1975年土地利用来说,1998年土地利用能降低洪峰流速、径流量和侵蚀量约5%~10%;3种退耕方案的减流减沙效益更加显著,可以降低洪峰流速、径流量和侵蚀量约40%~50%。 相似文献