全文获取类型
收费全文 | 128篇 |
免费 | 3篇 |
国内免费 | 5篇 |
专业分类
测绘学 | 2篇 |
大气科学 | 23篇 |
地球物理 | 24篇 |
地质学 | 70篇 |
海洋学 | 5篇 |
天文学 | 10篇 |
自然地理 | 2篇 |
出版年
2022年 | 1篇 |
2021年 | 2篇 |
2020年 | 3篇 |
2019年 | 2篇 |
2018年 | 5篇 |
2016年 | 6篇 |
2015年 | 3篇 |
2014年 | 5篇 |
2013年 | 11篇 |
2012年 | 11篇 |
2011年 | 8篇 |
2010年 | 7篇 |
2009年 | 15篇 |
2008年 | 6篇 |
2007年 | 7篇 |
2006年 | 13篇 |
2005年 | 2篇 |
2004年 | 3篇 |
2003年 | 2篇 |
2002年 | 2篇 |
2001年 | 4篇 |
1998年 | 2篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1969年 | 1篇 |
1965年 | 1篇 |
1964年 | 1篇 |
1962年 | 1篇 |
排序方式: 共有136条查询结果,搜索用时 0 毫秒
51.
Gernot Klammler Hans Kupfersberger Gerhard Rock Johann Fank 《Environmental Earth Sciences》2013,69(2):663-678
The aquifer Westliches Leibnitzer Feld, Austria, is a significant resource for regional and supraregional drinking water supply for more than 100,000 inhabitants, but the region also provides excellent agricultural conditions. This dual use implicates conflicts (e.g., non-point source groundwater pollution by nitrogen leaching), which have to be harmonized for a sustainable coexistence. At the aquifer scale, numerical models are state-of-the-art tools to simulate the behavior of groundwater quantity and quality and serve as decision support system for implementing groundwater protecting measures. While fully and iteratively coupled simulation models consider feedback between the saturated and unsaturated zone, sandy soil conditions and groundwater depths beneath the root zone allow the use of a unidirectional sequential coupling of the unsaturated water flow and nitrate transport model SIMWASER/STOTRASIM with FEFLOW for the investigation area. Considering separated inputs of water and nitrogen into groundwater out of surface water bodies, agricultural, residential and forested areas, first simulation results match observed groundwater tables, but underestimate nitrate concentrations in general. Thus, multiple scenarios assuming higher nitrogen inputs at the surface are simulated to converge with measured nitrate concentrations. Preliminary results indicate that N-input into the groundwater is strongly dominated by contributions of agricultural land. 相似文献
52.
Planning the use of fish for food security in the Pacific 总被引:1,自引:0,他引:1
Johann D. Bell Mecki Kronen Aliti Vunisea Warwick J. Nash Gregory Keeble Andreas Demmke Scott Pontifex Serge Andréfouët 《Marine Policy》2009
Fish is a mainstay of food security for Pacific island countries and territories (PICTs). Recent household income and expenditure surveys, and socio-economic surveys, demonstrate that subsistence fishing still provides the great majority of dietary animal protein in the region. Forecasts of the fish required in 2030 to meet recommended per capita fish consumption, or to maintain current consumption, indicate that even well-managed coastal fisheries will only be able to meet the demand in 6 of 22 PICTs. Governments of many PICTs will need to increase local access to tuna, and develop small-pond aquaculture, to provide food security. Diversifying the supply of fish will also make rural households in the Pacific more resilient to natural disasters, social and political instability, and the uncertainty of climate change. 相似文献
53.
54.
Johann Waringer Wolfram Graf Steffen U. Pauls Heinrich Vicentini Verena Lubini 《Limnologica》2008,38(1):34-42
At three alpine locations in Switzerland adults of Drusus melanchaetes and unknown Drusinae larvae which could not be identified with existing keys were sampled. Based on DNA association with adults, we identified the unknown larvae as D. melanchaetes. To further support the association of specimens a phylogeny was estimated with the putative closest relatives of D. melanchaetes – D. monticola and D. nigrescens – and five other species of Drusus (D. chrysotus, destitutus, discolor, muelleri and romanicus). A highly supported monophyletic clade groups unknown larvae and D. melanchaetes specimens from the central Alps and Austria (Vorarlberg), confirming the association.Based on morphology, larvae of D. melanchaetes key out together with D. destitutus in existing keys. D. melanchaetes is separated from the latter species by the shape of the lateral head profile which is almost straight and shows a small step at the height of the antenna, whereas in D. destitutus the lateral head profile is evenly rounded. In addition, in frontal view, the shape of the lateral head outline is straight in D. melanchaetes and rounded in D. destititus. There are also differences in the shape of the pronotum and in the number of the posterodorsal setae at the eighth abdominal dorsum. 相似文献
55.
We use the coupled climate model MPI-ESM to show that for higher CO2 levels the El Niño-Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) merge into a single mode of Pacific variability, regardless of present-day or Middle Miocene (~15 Ma) topographic boundary conditions. Hence, topographic differences—determining the landscape of past climates—play a smaller role for Pacific variability than previously thought. We attribute the single variability mode to resonance between these two oscillation patterns. In order to estimate the strength of the resonance we compute the spectral power of the ENSO and PDO time series and their coherence. We find that for both Middle Miocene and present-day topographic conditions, higher CO2 forcing leads to stronger resonance between ENSO and PDO. Our results show that (1) stronger CO2 forcing enhances Pacific variability resulting in stronger “atmospheric bridge” and that (2) past climates are likely to exhibit Pacific variability corresponding either to ENSO, PDO, or our proposed single mode. 相似文献
56.
Solar prominences have been simultaneously observed in the integrated light of the He D3 and the Hβ emissions on two successive days, using the SST on La Palma with its tip-tilt mirror locked on a nearby white-light
limb facular grain. The spatial and the temporal variation of the integrated line intensities and their ratio shows mainly
two characteristics: (A) Constant emission ratio (even) in regions with substantial intensity variations and (B) varying emission
ratio (often) tightly related to intensity structures of the prominence. (A) May be explained by a different number of superposing
threads along the line of sight having very similar physical state. (B) Indicates threads with different intrinsic physical
states; these may depend on the gas pressure or the inner structure of each thread, i.e., the “packing density,” affecting the penetration of ionizing EUV radiation, which affects the He i level populations and thus the rate of the triplet excitation. 相似文献
57.
Johann G. Raith 《Mineralogy and Petrology》2004,82(3-4):I-III
58.
59.
Reasons for Spatial Microdistributions of Foraminifers in an Intertidal Pool (Northern Adriatic Sea)
Abstract. The spatial microdistribution of foraminifers was tested by the method of quadratic samplings on 2 sample grids in an intertidal pool of the northernmost Adriatic sea. Abundant species of foraminifers exhibit patchy distributions throughout; the distribution-patterns of some species correspond nearly completely. Using statistical methods (regression- and correlation-analyses) correlations to abiotic and biotic factors (water depth, exposure rate, seagrass, benthonic algae) were ascertained. The significant correlations of the foraminiferal frequencies to blue-green algae and/or diatoms enable an interpretation of these connexions as food dependences. Several foraminiferal species seem to have specific diets. 相似文献
60.