全文获取类型
收费全文 | 115篇 |
免费 | 5篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 6篇 |
大气科学 | 25篇 |
地球物理 | 36篇 |
地质学 | 33篇 |
海洋学 | 9篇 |
天文学 | 1篇 |
综合类 | 1篇 |
自然地理 | 13篇 |
出版年
2022年 | 2篇 |
2021年 | 1篇 |
2020年 | 3篇 |
2017年 | 2篇 |
2016年 | 6篇 |
2015年 | 3篇 |
2014年 | 4篇 |
2013年 | 2篇 |
2012年 | 2篇 |
2011年 | 9篇 |
2010年 | 5篇 |
2009年 | 6篇 |
2008年 | 11篇 |
2007年 | 9篇 |
2006年 | 7篇 |
2005年 | 9篇 |
2004年 | 2篇 |
2003年 | 3篇 |
2002年 | 4篇 |
2001年 | 2篇 |
2000年 | 3篇 |
1999年 | 7篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 13篇 |
1984年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有124条查询结果,搜索用时 15 毫秒
31.
G. Salvadè K. Stocker J. Trösch F. Zamboni 《Aquatic Sciences - Research Across Boundaries》1992,54(3-4):187-204
The hydrodynamic processes in the Lake of Lugano (Lago di Lugano) have been the object of three major measuring campaigns. The first during summer 1979 in the North Basin, the second in the autumn of 1984 in the South Basin and the last in 1989 again in the North Basin. It is expected that analysis of the collected data in conjunction with theoretical concepts will yield conclusive findings on the driving forces and hydrodynamics of the lake. Numerical models have been applied to the lake and the results have been compared to the measurements. Some models calculate the periods and distributions of amplitude, as well as surface velocities and internal seiches. Other models calculate wind-induced water circulation. Evidence is given to the peculiarities of the North Basin and the difficulties related with the depth-width ratio and with its deep chemical stratification. 相似文献
32.
M. Taylan 《Ocean Engineering》2002,29(13):1021-1681
In this paper, two alternative corvette hull forms namely, the round bottom and deep V have been comparatively analyzed in terms of intact and damaged stability and roll performance in beam waves. The boat is planned to operate in the Navy's coastal water missions. Even though both forms are considered to comply with the design requirements, slight differences in displacement and principal dimensions are found to be inevitable due to the intrinsic characteristics of the specific forms. First part of the study concentrated on determining the conventional intact and damaged stability qualities whereas the second part was devoted to nonlinear rolling behavior of the vessels in synchronous beam waves. Nonlinear rolling amplitudes are thought to be quite important especially for resonance condition since they tend to peak in capsize conditions. Various combinations of loading conditions and damaged cases are taken into account to analyze the effects of them. Comparative results are presented graphically depicting the advantages/disadvantages of the selected forms over each other. 相似文献
33.
Maja A. Lazzaretti Kurt W. Hanselmann Helmut Brandl Daniel Span Reinhard Bachofen 《Aquatic Sciences - Research Across Boundaries》1992,54(3-4):285-299
P, Fe, Mn, and S species were analyzed in water samples from the sediment-water interface collected at four seasonally different times during the course of a year at two sampling sites in the southern basin of Lake Lugano (Lago di Lugano). The results reveal the strong influence of the biogeochemical processes in the sediment on the chemical composition of the lake water above. Consumption of oxygen and nitrate under oxic to microoxic conditions in the water column as well as sequential release of reduced manganese and iron under anoxic conditions was observed as a direct or indirect consequence of microbially mediated degradation of organic matter. The seasonal pattern observed for the release and the retainment of dissolved reduced iron and manganese correlates well with the one for dissolved phosphate. Iron, manganese and phosphorus cycling are coupled tightly in these sediments. Both sediment types act as sinks for hydrogen sulfide and sulfate. An inner-sedimentary sulfur cycle is proposed to couple iron, manganese and phosphorus cycling with the degradation of organic matter. Nutrient cycling at the sediment-water interface might thus be driven by a microbially regulated electron pumping mechanism. The results contribute to a better understanding of the role of sediment processes in the lake's internal phosphorus cycle and its seasonal dynamics. 相似文献
34.
The Lago di Cignana ultra‐high‐pressure unit (LCU), which consists of coesite–eclogite facies metabasics and metasediments, preserves the most deeply subducted oceanic rocks worldwide. New constraints on the prograde and early retrograde evolution of this ultra‐high pressure unit and adjoining units provide important insights into the evolution of the Piemontese–Ligurian palaeo‐subduction zone, active in Paleocene–Eocene times. In the LCU, a first prograde metamorphic assemblage, consisting of omphacite + Ca‐amphibole + epidote + rare biotite + ilmenite, formed during burial at estimated P < 1.7 GPa and 350 < T < 480 °C. Similar metamorphic conditions of 400 < T < 650 °C and 1.0 < P < 1.7 GPa have been estimated for the meta‐ophiolitic rocks juxtaposed to the LCU. The prograde assemblage is partially re‐equilibrated into the peak assemblage garnet + omphacite + Na‐amphibole + lawsonite + coesite + rutile, whose conditions were estimated at 590 < T < 605 °C and P > 3.2 GPa. The prograde path was characterized by a gradual decrease in the thermal gradient from ~9–10 to ~5–6 °C km?1. This variation is interpreted as the evidence of an increase in the rate of subduction of the Piemonte–Ligurian oceanic slab in the Eocene. Accretion of the Piemontese oceanic rocks to the Alpine orogen and thermal relaxation were probably related to the arrival of more buoyant continental crust at the subduction zone. Subsequent deformation of the orogenic wedge is responsible for the present position of the LCU, sandwiched between two tectonic slices of meta‐ophiolites, named the Lower and Upper Units, which experienced peak pressures of 2.7–2.8 and <2.4 GPa respectively. 相似文献
35.
J. Vandenberghe R. Gracheva 《Proceedings of the Geologists' Association. Geologists' Association》2010,121(2):229-237
River valleys have always been attractive places for human occupation. The history of Mesolithic and Neolithic floodplain occupation is linked with archives of fluvial evolution, in particular the intricate relationships between palaeo-hydrological regimes, ecological development and sedimentary environments. This paper describes floodplain evolution in the Russian forest lowland around Moscow since the last deglaciation. Although there is an obvious climatic driving force for the initial fluvial incision at the end of the last glacial, there are many arguments pointing to complex intrinsic evolution involving successive pedogenesis, floodplain accumulation, flooding and fluvial incision from the beginning of the Holocene towards recent times. Increasing wetness during the early and middle Holocene forced people to move from the lowest parts of the valley towards its edges until ultimately, during the most severe flooding episode (at around 2600 years BP), they had to abandon the valley altogether. 相似文献
36.
The Analysis on the Features of the Atmospheric Circulation in Preceding Winters for the Summer Drought and Flooding in the Yangtze And Huaihe River Valley 总被引:12,自引:1,他引:12
TheAnalysisontheFeaturesoftheAtmosphericCirculationinPrecedingWintersfortheSummerDroughtandFloodingintheYangtzeandHuaiheRiver... 相似文献
37.
Multiple criteria decision making and decision support systems for flood risk management 总被引:1,自引:4,他引:1
Jason K. Levy 《Stochastic Environmental Research and Risk Assessment (SERRA)》2005,19(6):438-447
Multiple criteria decision making (MCDM) is a collection of methodologies to compare, select, or rank multiple alternatives
that typically involve incommensurate attributes. MCDM is well-suited for eliciting and modeling the flood preferences of
stakeholders and for improving the coordination among flood agencies, organizations and affected citizens. A flood decision
support system (DSS) architecture is put forth that integrates the latest advances in MCDM, remote sensing, GIS, hydrologic
models, and real-time flood information systems. The analytic network process (ANP) is discussed with application to short-term
flood management options for the middle reaches of the Yangtze River. It is shown that DSS and MCDM can improve flood risk
planning and management under uncertainty by providing data displays, analytical results, and model output to summarize critical
flood information. 相似文献
38.
Ar/Ar analyses of phengites and paragonites from the ultrahigh-pressure metamorphic rocks (zoisite–clinozoisite schist, garnet–phengite schist and piemontite schist) in the Lago di Cignana area, Western Alps were carried out with a laser probe step-heating method using single crystals and a spot dating method on thin sections. Eight phengite and two paragonite crystals give the plateau ages of 37–42 Ma with 96–100% of 39Ar released. Each rock type also contains mica crystals showing discordant age spectra with age fractions (20–35 Ma) significantly younger than the plateau ages. Phengite inclusions in garnet give ages of 43.2 ± 1.1 Ma and 44.4 ± 1.5 Ma, which are significantly older than the spot age (36.4 ± 1.4 Ma) from the matrix phengites, and the plateau ages from the step-heating analyses. Inclusion ages (43 and 44 Ma) are consistent with a zircon SHRIMP age (44 ± 1 Ma) in this area. These results suggest that the oceanic materials that underwent a simple subduction related UHPM, form excess 40Ar-free phengite and that the peak metamorphism is ca. 44 Ma or little older. We suggest that matrix phengites experienced a retrogression reaction changing their chemistry contemporaneously with deformation related to the exhumation of rocks releasing significant radiogenic 40Ar from the crystals. This has lead to the apparent ages of the matrix phengites that are significantly younger than the inclusion age. 相似文献
39.
Deterioration in the water quality results from coal mining, and the significant impact on the environment in South Africa
has been reported (Funke in SA Water, Sci Technol 15:115–144; 1983). Pyrite in with South African coal can be oxidised to
yield acidic and high salinity water. This study deals with the rate at which sulphate could be produced for collieries under
different conditions. Four collieries in the Witbank coalfield were selected for this investigation. The boreholes were investigated
with an in-situ multi-parameter probe, and then sampled at different times with a specific depth sampler to determine the
chemical composition of the water in the collieries. Water level measurements and volumetric calculations were done to determine
influx rates. Daily sulphate generation rate for underground mining was found to be in the range of 0.4–2.7 kg/ha, depending
on the availability of oxygen and the residence time of the water (the time available for neutralising agents present to react)
in the mining void. The exclusion of oxygen due to flooding and the presence of calcareous carbonates influences the observed
sulphate generation. 相似文献
40.
江苏省里下河地区梅雨洪涝灾害成因与规律的探讨 总被引:5,自引:1,他引:4
本文根据里下河地区建湖、兴化、盐城、宝应和阜宁共5个代表站,对1954-1993年共40年的梅雨期降水量和西太平洋副高脊线、588位势什米的西脊点等资料进行分析,发现里下河地区洪涝灾害与梅雨期开始时间早、持续时间长、暴雨频发和雨带稳定在里下河地区有关。而后者又与副热带高压活动特点以及西风带环流特征有密切的关系。分析上述5个代表站梅雨量、副高脊线的所在纬度和588位势什米特征线西脊点的功率谱,得出了 相似文献