全文获取类型
收费全文 | 1150篇 |
免费 | 31篇 |
国内免费 | 8篇 |
专业分类
测绘学 | 16篇 |
大气科学 | 121篇 |
地球物理 | 234篇 |
地质学 | 417篇 |
海洋学 | 87篇 |
天文学 | 202篇 |
综合类 | 3篇 |
自然地理 | 109篇 |
出版年
2021年 | 10篇 |
2020年 | 12篇 |
2019年 | 10篇 |
2018年 | 15篇 |
2017年 | 24篇 |
2016年 | 19篇 |
2015年 | 19篇 |
2014年 | 28篇 |
2013年 | 61篇 |
2012年 | 25篇 |
2011年 | 47篇 |
2010年 | 35篇 |
2009年 | 64篇 |
2008年 | 34篇 |
2007年 | 28篇 |
2006年 | 44篇 |
2005年 | 33篇 |
2004年 | 49篇 |
2003年 | 48篇 |
2002年 | 33篇 |
2001年 | 30篇 |
2000年 | 27篇 |
1999年 | 34篇 |
1998年 | 29篇 |
1997年 | 18篇 |
1996年 | 19篇 |
1995年 | 21篇 |
1994年 | 18篇 |
1993年 | 18篇 |
1992年 | 18篇 |
1991年 | 15篇 |
1990年 | 14篇 |
1989年 | 12篇 |
1988年 | 12篇 |
1987年 | 15篇 |
1986年 | 8篇 |
1985年 | 13篇 |
1984年 | 24篇 |
1983年 | 14篇 |
1982年 | 15篇 |
1981年 | 23篇 |
1980年 | 14篇 |
1979年 | 15篇 |
1978年 | 18篇 |
1977年 | 13篇 |
1976年 | 12篇 |
1975年 | 19篇 |
1974年 | 12篇 |
1973年 | 10篇 |
1972年 | 11篇 |
排序方式: 共有1189条查询结果,搜索用时 15 毫秒
211.
Predisposition and cause of the catastrophic landslides of August 2005 in Brienz (Switzerland) 总被引:2,自引:0,他引:2
Very intensive rainfall in August 2005 (>300 mm/3 days) triggered moderately deep (2–10 m) landslides of about 50'000 m3 volume each in two mountain torrent catchments above the village of Brienz (Berner Oberland, Switzerland). These landslides
– originating in Trachtbach and Glyssibach catchments – transformed into extremely rapid (>5 m/s) debris flows, which caused
significant damage in inhabited areas; two persons lost their lives and about twenty-five families became homeless. The Brienz
case was the most damaging one among many landslide disasters occurring during those rainy days in the Swiss Alps. In this
paper we study in detail the predisposition and causes of the 2005 landslides in the Brienz area, based on field mapping,
analysis of high resolution images and digital terrain models, derived from LIDAR and infrared measurements taken before and
after the event. The features of these landslides are compared with past and dormant landslides in the mid-slope portion of
the mountain chain north of Brienz, which has been the source of many catastrophic mass wasting events during the last centuries.
Detailed field mapping shows that highly weathered series of strongly overconsolidated Mesozoic marls (Diphyoides Limestone
& Vitznau Marls of Valanginian age) and their residual soils form the primary source for the sliding materials. The rupture
surfaces of the moderately deep landslides often run at the transition from saprolite to weathered bedrock, with a dip angle
of about 40o in the landslide depletion area. These landslides transform into debris flows, where debris slides into strongly
convergent hillslopes or directly into headwater channels. 相似文献
212.
Preparing a seismic hazard model for Switzerland: the view from PEGASOS Expert Group 3 (EG1c) 总被引:1,自引:0,他引:1
The seismic hazard model used in the PEGASOS project for assessing earth-quake hazard at four NPP sites was a composite of four sub-models, each produced by a team of three experts. In this paper, one of these models is described in detail by the authors. A criticism sometimes levelled at probabilistic seismic hazard studies is that the process by which seismic source zones are arrived at is obscure, subjective and inconsistent. Here, we attempt to recount the stages by which the model evolved, and the decisions made along the way. In particular, a macro-to-micro approach was used, in which three main stages can be described. The first was the characterisation of the overall kinematic model, the “big picture” of regional seismogenesis. Secondly, this was refined to a more detailed seismotectonic model. Lastly, this was used as the basis of individual sources, for which parameters can be assessed. Some basic questions had also to be answered about aspects of the approach to modelling to be used: for instance, is spatial smoothing an appropriate tool to apply? Should individual fault sources be modelled in an intraplate environment? Also, the extent to which alternative modelling decisions should be expressed in a logic tree structure has to be considered. 相似文献
213.
To assess whether reaches of the Motueka River (New Zealand) that gain water from groundwater were likely to represent significant cold-water refugia for brown trout during periods of high water temperatures, water temperature was monitored for more than 18 months in two gaining reaches of the Motueka River and three reaches that were predicted to be losing water to groundwater. These data were used to predict brown trout (Salmo trutta) growth in gaining and losing reaches. Groundwater inputs had a small effect on water temperature at the reach-scale and modelling suggests that the differences observed were unlikely to result in appreciable differences in trout growth. Several coldwater patches were identified within the study reach that were up to 3.5°C cooler than the mainstem, but these were generally shallow and were unlikely to provide refuge for adult trout. The exception was Hinetai Spring, which had a mean water temperature of close to 16°C during the period January–March, when temperatures in the mainstem regularly exceeded 19°C. Trout were observed within the cold-water plume at the mouth of Hinetai Stream, which would allow them to thermoregulate when mainstem temperatures are unfavourable while still being able to capitalise on food resources available in the mainstem. 相似文献
214.
Mohammad Merheb Roger Moussa François Colin Charles Perrin Nicolas Baghdadi 《水文科学杂志》2013,58(14):2520-2539
ABSTRACTThis work examines 140 hydrological studies conducted in the Mediterranean region. It identifies key characteristics of the hydrological responses of Mediterranean catchments at various time scales and compares different methods and modelling approaches used for individual-catchment studies. The study area is divided into the northwestern (NWM), eastern (EM) and southern (SM) Mediterranean. The analysis indicates regional discrepancies in which the NWM shows the most extreme rainfall regime. A tendency for reduced water resources driven by both anthropogenic and climatic pressures and a more extreme rainfall regime are also noticeable. Catchments show very heterogeneous responses over time and space, resulting in limitations in hydrological modelling and large uncertainties in predictions. However, few models have been developed to address these issues. Additional studies are necessary to improve the knowledge of Mediterranean hydrological features and to account for regional specificities.
Editor D. Koutsoyiannis Associate editor A. Efstratiadis 相似文献
215.
The transformation of a weakly nonlinear interfacial solitary wave in an ideal two-layer flow over a step is studied. In the vicinity of the step the wave transformation is described in the framework of the linear theory of long interfacial waves, and the coefficients of wave reflection and transmission are calculated. A strong transformation arises for propagation into shallower water, but a weak transformation for propagation into deeper water. Far from the step, the wave dynamics is described by the Korteweg-de Vries equation which is fully integrable. In the vicinity of the step, the reflected and transmitted waves have soliton-like shapes, but their parameters do not satisfy the steady-state soliton solutions. Using the inverse scattering technique it is shown that the reflected wave evolves into a single soliton and dispersing radiation if the wave propagates from deep to shallow water, and only dispersing radiation if the wave propagates from shallow to deep water. The dynamics of the transmitted wave is more complicated. In particular, if the coefficient of the nonlinear quadratic term in the Korteweg-de Vries equation is not changed in sign in the region after the step, the transmitted wave evolves into a group of solitons and radiation, a process similar to soliton fission for surface gravity waves at a step. But if the coefficient of the nonlinear term changes sign, the soliton is destroyed completely and transforms into radiation. The effects of cubic nonlinearity are studied in the framework of the extended Korteweg-de Vries (Gardner) equation which is also integrable. The higher-order nonlinear effects influence the amplitudes of the generated solitons if the amplitude of the transformed wave is comparable with the thickness of lower layer, but otherwise the process of soliton fission is qualitatively the same as in the framework of the Korteweg-de Vries equation. 相似文献
216.
A paleoenvironmental model is proposed for the western shoreline of Cape Cod Bay, Massachusetts, from about 9,000 through 5,500 years B.P. Central to this reconstruction is the integration and correlation of the glacial sediments, radiometric chronology and pollen stratigraphy of an exposed peat deposit located near Nameloc Heights, Plymouth, Massachusetts. Four Carbon-14 dates provide a chronology and suggest an average rate of peat accumulation of about 6 cm/100 years from 8,800 through 7,400 years B.P., decreasing to 3 cm/100 years from 7,400 to 5,500 years B.P. This sequence of radiometric dates provides a temporal framework within which the pollen taxa of the peat deposit can be correlated to the established floristic zones of the southern New England region. 相似文献
217.
218.
Oswaldo Eduardo Ramos Ramos Luis Fernando Cáceres Mauricio Rodolfo Ormachea Muñoz Prosun Bhattacharya Israel Quino Jorge Quintanilla Ondra Sracek Roger Thunvik Jochen Bundschuh Maria Eugenia García 《Environmental Earth Sciences》2012,66(3):793-807
Water management in semiarid and arid catchments such as the Poopó Lake Basin requires improved understanding of the complex behavior of the various contaminants, which affect the drinking water quality and considered as crucial for sustainable development of the region. Mechanisms of arsenic (As) release in the surface and groundwater were studied. Hydrochemical data for surface water (4 samples) and groundwater (28 samples) were collected in a small watershed in the Poopó catchment at the highland of the Bolivian Andes (Altiplano). All of them show high electrical conductivity values and moderately oxidizing conditions. The surface water contains high concentration of sulfate and the trace elements As, Zn and Pb in the zone affected by acid mine drainage. There is a large variability of the concentration of As and of the trace elements in the groundwater in the five different regions within the Poopó catchment. The metal concentrations sensitive to changes of redox state and results of speciation modeling suggest that As (V) is a predominant aqueous species, which conforms to the prevailing oxidizing conditions in the shallow groundwater environment. Two generalized trends for As distribution were identified in groundwater: (a) high concentrations are found in the arid zone (100–250 μg/L) in the southern (region III) and in the northwestern (region V) regions, and (b) low concentrations (<50 μg/L) are found in the remaining part of the basin (region I, II and IV). However, the spatial distribution within these regions needs to be investigated further. A conclusion from the present study is that there are multiple sources of As as well as other trace elements (such as Cd, Mn and Zn) in the Poopó Lake Basin. Among the sources and the processes which led to the mobility of As and other trace metals in the region are: (a) weathering of sulfide minerals, (b) oxidation of pyrite and/or arsenopyrite in mineralized areas and (c) desorption from hydrous ferric oxide (HFO) surfaces. In non-mining areas, volcanic ash is suggested to be a significant source of As. 相似文献
219.
Roger N. Jones 《Climatic change》2011,108(4):733-743
The latest iteration of Intergovernmental Panel on Climate Change (IPCC) uncertainty guidance is simpler and easier to use
than the previous version. However, its primary focus remains assessing “what is at risk” under climate change, thus is most
suitable for dealing with the scientific uncertainties in Working Group I and part of Working Group II findings. I distinguish
between tame and complex risks, arguing that the guidance is most suited to assessing tame risks. Climate change is a complex
risk, and as such as can be divided into idealized, calculated and perceived risks. While science has claims to objectivity,
risk has a specific value component: when measuring gain and loss, calculated risks compete with risky options to manage those
risks. The IPCC is charged with calculating risk (IPCC 2007, p22) but the communication of key findings takes place in an environment of competing perceived risks. Recommendations for
managing this complex environment include separating scientific and risk-based findings, treating uncertainties for each separately;
strengthening the philosophical basis of uncertainty management; application of a methodical scientific research program;
clearly communicating competing findings, especially in the social sciences; and application of multiple frame to policy-relevant
findings as reflected in the literature. 相似文献
220.
Authors of the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) received guidance on reporting
understanding, certainty and/or confidence in findings using a common language, to better communicate with decision makers.
However, a review of the IPCC conducted by the InterAcademy Council (2010) found that “the guidance was not consistently followed in AR4, leading to unnecessary errors . . . the guidance was often
applied to statements that are so vague they cannot be falsified. In these cases the impression was often left, quite incorrectly,
that a substantive finding was being presented.” Our comprehensive and quantitative analysis of findings and associated uncertainty
in the AR4 supports the IAC findings and suggests opportunities for improvement in future assessments. 相似文献