全文获取类型
收费全文 | 72篇 |
免费 | 5篇 |
专业分类
大气科学 | 14篇 |
地球物理 | 28篇 |
地质学 | 24篇 |
海洋学 | 5篇 |
天文学 | 5篇 |
自然地理 | 1篇 |
出版年
2020年 | 5篇 |
2019年 | 3篇 |
2016年 | 2篇 |
2015年 | 3篇 |
2014年 | 5篇 |
2013年 | 6篇 |
2012年 | 1篇 |
2011年 | 3篇 |
2010年 | 4篇 |
2009年 | 2篇 |
2008年 | 1篇 |
2007年 | 3篇 |
2002年 | 1篇 |
2000年 | 1篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1982年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1972年 | 4篇 |
1970年 | 1篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1961年 | 1篇 |
1956年 | 1篇 |
1954年 | 1篇 |
1951年 | 1篇 |
1950年 | 1篇 |
1949年 | 1篇 |
1948年 | 1篇 |
排序方式: 共有77条查询结果,搜索用时 975 毫秒
1.
Application of participatory principles to investigation of the natural world: An example from Chile
Participatory research in environmental and natural resources-related fields is premised on many of the same notions that underlie participatory processes in decision making. This study examines one instance of participatory research to assess the extent to which the documented benefits of participatory decision-making hold up in the context of research. A survey of Chilean shell-fishers engaged in research with marine biologists assesses the relationships between four variables: fishers’ participation in research, fishers’ opinions of biologists, fishers’ trust in biologists, and fishers’ acquisition of knowledge from biologists. Results illuminate the multidimensionality of these variables and suggest that complex interrelationships between them make the benefits of participatory research more nuanced than those reported for participatory decision-making. For instance, participatory research may provide low benefits when participatory research outcomes differ little from those produced solely by scientists. In addition, high-cost scenarios may result when outcomes of participatory research are inferior to those produced solely by scientists. A third downside may result when participation leads participants to increase their deference to scientific knowledge, thereby defeating the corroborative purpose of their participation. A fourth effect may occur when increased trust by in scientists results from participation, decreasing participants’ perceived need to take part in research. 相似文献
2.
U. Schumann 《Annales Geophysicae》1994,12(5):365-384
Emissions from aircraft engines include carbon dioxide, water vapour, nitrogen oxides, sulphur components and various other gases and particles. Such emissions from high-flying global civil subsonic air traffic may cause anthropogenic climate changes by an increase of ozone and cloudiness in the upper troposphere, and by an enhanced greenhouse effect. The absolute emissions by air traffic are small (a few percent of the total) compared to surface emissions. However, the greenhouse effect of emitted water and of nitrogen oxides at cruise altitude is potentially large compared to that of the same emissions near the earth’s surface because of relatively large residence times at flight altitudes, low background concentrations, low temperature, and large radiative efficiency. Model computations indicate that emission of nitrogen oxides has doubled the background concentration in the upper troposphere between 40○N and 60○N. Models also indicate that this causes an increase of ozone by about 5-20%. Regionally, the observed annual mean change in cloudiness is 0.4%. It is estimated that the resultant greenhouse effect of changes in ozone and thin cirrus cloud cover causes a climatic surface temperature change of 0.01-0.1 K. These temperature changes are small compared to the natural variability. Recent research indicates that the emissions at cruise altitude may increase the amount of stratospheric aerosols and polar stratospheric clouds and thereby have an impact on the atmospheric environment. Air traffic is increasing about 5-6% per year, fuel consumption by about 3%, hence the effects of the related emissions are expected to grow. This paper surveys the state of knowledge and describes several results from recent and ongoing research. 相似文献
3.
The separation of heavy metals by complexation with macromolecular water-soluble agents and subsequent ultrafiltration is described. The method can be expected to join common techniques of metal separation like liquid-liquid extraction, adsorption, redox reaction or liquid membrane permeation. Reactions between metal ions and polymer phases are characterized as pH-dependent distribution equilibria illustrated at a propene-maleic acid copolymer as an example. The complexation behaviour of the substance under study is governed by isotherms of the saturation type. Attempts proved to be successful to calculate break-through constants as well as saturation capacities from batch-type studies and dynamic measurements by transferring the laws of adsorption and ion exchange, respectively, to the ultrafiltration process. The quantities of fixed metals amounting to about 2.5 mmol/g were found to be in the range of moderate adsorbents. A solution consisting of 3 solutes has been tested to get more detailed information on mixture behaviour as compared to single component systems. In the long run, the proposed method should provide an additional variant for the extraction and concentration of metal ions from diluted aqueous solutions. 相似文献
4.
5.
Zusammenfassung Die Orientierung der Kristallite eines Faserhalites wurde mit einer Röntgen-U-Tisch-Methode bestimmt, indem für jedes Korn die drei Symmetrieachsen des durch einen Bildverstärker sichtbar gemachten Laue-Bildes zentral gestellt wurden. Die Darstellung der Ergebnisse erfolgte in einer flächentreuen Projektion durch Eintragung der Pole der Kornschnittflächen im entsprechenden Präparat in einem sphärischen Dreieck mit den Durchstoßpunkten der Senkrechten auf (001), (011) und (111) als Eckpunkten.Aus der Bearbeitung eines Schnittes senkrecht zur Faserrichtung ergibt sich, daß etwa ein Drittel der Kristallite eine zweizählige Achse nahe zur Faserrichtung hat; das entspricht qualitativ den Erwartungen aus den vektoriellen Wachstumsgeschwindigkeiten beim Halit. Die Ergebnisse aus Schnitten parallel zur Faserachse sind nicht so klar zu interpretieren, jedoch zeigen sich auch hier Orientierungseffekte.
Mit 5 Abbildungen 相似文献
Preferred crystallographic orientation of crystallites in natural fibrous halite aggregates
Summary The orientations of the crystallites in a fibrous halite were determined using an X-ray universal stage method in which for each individual grain the Laue-diagrams of the three symmetry axes, made visible by an image intensifier, were set at the center. The results are presented in an equal-area net using the poles of the corresponding grain's sections in a spherical triangle with the normals to (001), (011) and (111) as corner points.Studies on a thin section perpendicular to the fiber direction revealed a two-fold axis approximately along the fiber direction for about a third of the crystallites. This is qualitatively what is expected from halite vectorial growth rates. The results of sections parallel to the fiber axis are not so clear but do show orientation effects.
Mit 5 Abbildungen 相似文献
6.
Jeffrey Neal Guy Schumann Paul Bates Wouter Buytaert Patrick Matgen Florian Pappenberger 《水文研究》2009,23(25):3641-3649
River discharge is currently monitored by a diminishing network of gauges, which provide a spatially incomplete picture of global discharges. This study assimilated water level information derived from a fused satellite Synthetic Aperture Radar (SAR) image and digital terrain model (DTM) with simulations from a coupled hydrological and hydrodynamic model to estimate discharge in an un‐gauged basin scenario. Assimilating water level measurements led to a 79% reduction in ensemble discharge uncertainty over the coupled hydrological hydrodynamic model alone. Measurement bias was evident, but the method still provided a means of improving estimates of discharge for high flows. The study demonstrates the potential of currently available synthetic aperture radar imagery to reduce discharge uncertainty in un‐gauged basins when combined with model simulations in a data assimilation framework, where sufficient topographic data are available. The work is timely because in the near future the launch of satellite radar missions will lead to a significant increase in the volume of data available for space‐borne discharge estimation. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
7.
Thermal and exhumation history of the central Rwenzori Mountains, Western Rift of the East African Rift System, Uganda 总被引:2,自引:1,他引:1
F. U. Bauer U. A. Glasmacher U. Ring A. Schumann B. Nagudi 《International Journal of Earth Sciences》2010,99(7):1575-1597
The Rwenzori Mountains (Mtns) in west Uganda are the highest rift mountains on Earth and rise to more than 5,000 m. We apply
low-temperature thermochronology (apatite fission-track (AFT) and apatite (U–Th–Sm)/He (AHe) analysis) for tracking the cooling
history of the Rwenzori Mtns. Samples from the central and northern Rwenzoris reveal AFT ages between 195.0 (±8.4) Ma and
85.3 (±5.3) Ma, and AHe ages between 210.0 (±6.0) Ma to 24.9 (±0.5) Ma. Modelled time–temperature paths reflect a protracted
cooling history with accelerated cooling in Permo-Triassic and Jurassic times, followed by a long period of constant and slow
cooling, than succeeded by a renewed accelerated cooling in the Neogene. During the last 10 Ma, differentiated erosion and
surface uplift affected the Rwenzori Mtns, with more pronounced uplift along the western flank. The final rock uplift of the
Rwenzori Mtns that partly led to the formation of the recent topography must have been fast and in the near past (Pliocene
to Pleistocene). Erosion could not compensate for the latest rock uplift, resulting in Oligocene to Miocene AHe ages. 相似文献
8.
Based on the stochastic and phenomenological aspects of hydrological processes, a conceptually based stochastic point process (SPP) model for daily stream‐flow generation is proposed in this paper. In which, storms are defined by a stochastic point process with marked values. All the random variables defining the process are assumed to be mutually independent, which constitutes a compound Poisson point process. The direct surface runoff is regarded as occurring from storage in a cascade of surface linear reservoirs and is responsible for the short‐term variation of the daily stream flows. The baseflow component is considered as coming from subsurface/groundwater storage and is responsible for the long‐term persistence of the storm time‐series. This type of model is proposed as a more realistic model of daily stream flow than models based on pure stochastic processes. Studies on the instantaneous unit hydrograph and the mechanism of baseflow could thereby provide some parameters for this model. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
9.
10.
The Tycho Epoch Photometry Annex A, a data base of photometry of more than 34 000 bright stars, has been searched for periodic variable stars with approximately sinusoidal light curves. Advantage was taken of special properties of the observing programme (photometry in two wavebands, availability of repeated measurements) to use simple but efficient variable selection criteria. Details of 70 strong candidate variables are presented. 相似文献