全文获取类型
收费全文 | 179篇 |
免费 | 4篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 1篇 |
大气科学 | 20篇 |
地球物理 | 44篇 |
地质学 | 74篇 |
海洋学 | 10篇 |
天文学 | 22篇 |
综合类 | 1篇 |
自然地理 | 13篇 |
出版年
2021年 | 2篇 |
2020年 | 5篇 |
2019年 | 4篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2016年 | 6篇 |
2015年 | 2篇 |
2014年 | 6篇 |
2013年 | 17篇 |
2012年 | 9篇 |
2011年 | 9篇 |
2010年 | 10篇 |
2009年 | 16篇 |
2008年 | 13篇 |
2007年 | 11篇 |
2006年 | 5篇 |
2005年 | 7篇 |
2004年 | 4篇 |
2003年 | 5篇 |
2002年 | 4篇 |
2001年 | 7篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1969年 | 1篇 |
排序方式: 共有185条查询结果,搜索用时 895 毫秒
171.
172.
Glacial isostatic adjustment in Fennoscandia from GRACE data and comparison with geodynamical models
The Earth’s gravity field observed by the Gravity Recovery and Climate Experiment (GRACE) satellite mission shows variations due to the integral effect of mass variations in the atmosphere, hydrosphere and geosphere. Several institutions, such as the GeoForschungsZentrum (GFZ) Potsdam, the University of Texas at Austin, Center for Space Research (CSR) and the Jet Propulsion Laboratory (JPL), Pasadena, provide GRACE monthly solutions, which differ slightly due to the application of different reduction models and centre-specific processing schemes. The GRACE data are used to investigate the mass variations in Fennoscandia, an area which is strongly influenced by glacial isostatic adjustment (GIA). Hence the focus is set on the computation of secular trends. Different filters (e.g. isotropic and non-isotropic filters) are discussed for the removal of high frequency noise to permit the extraction of the GIA signal. The resulting GRACE based mass variations are compared to global hydrology models (WGHM, LaDWorld) in order to (a) separate possible hydrological signals and (b) validate the hydrology models with regard to long period and secular components. In addition, a pattern matching algorithm is applied to localise the uplift centre, and finally the GRACE signal is compared with the results from a geodynamical modelling. The GRACE data clearly show temporal gravity variations in Fennoscandia. The secular variations are in good agreement with former studies and other independent data. The uplift centre is located over the Bothnian Bay, and the whole uplift area comprises the Scandinavian Peninsula and Finland. The secular variations derived from the GFZ, CSR and JPL monthly solutions differ up to 20%, which is not statistically significant, and the largest signal of about 1.2 Gal/year is obtained from the GFZ solution. Besides the GIA signal, two peaks with positive trend values of about 0.8 Gal/year exist in central eastern Europe, which are not GIA-induced, and also not explainable by the hydrology models. This may indicate that the recent global hydrology models have to be revised with respect to long period and secular components. Finally, the GRACE uplift signal is also in quite good agreement with the results from a simple geodynamical modelling. 相似文献
173.
Andreas Krein Holger Klinck Michael Eiden Wolfhard Symader Reinhard Bierl Lucien Hoffmann Laurent Pfister 《地球表面变化过程与地形》2008,33(1):152-163
This article deals with the following two questions. Are acoustic measurements in running waters appropriate for a highly resolved investigation of the bedload transport? Which characterizations of the bedload regarding mass and shape are possible via the acoustic signals? The signals were recorded by means of data recorders (Tascam Inc. DAP1 Portable Data Recorder) and hydrophones (International Transducer Corp. ITC‐4001 A). The ITC‐4001 is a shallow water omnidirectional transducer containing a flexural disc transducer utilizing Channelite‐5400 ceramics mounted in a rugged corrosion‐resistant housing. These hydrophones were screwed onto the bottom side of stainless steel plates, serving as a contact surface for the bedload in motion above them. After more than 100 series of tests in the laboratory, which indicated the basic relations between the dimension, shape and weight of the bedload and the resulting signal, field tests of the measuring system were conducted. By artificially produced flood waves in the small brooks Riverisbach, Olewiger Bach and by a winter flood wave in the River Moselle, it is possible to elaborate similar structures of the signal course of the bedload movement. The highest transport rates can be observed at the beginning of the increasing limbs and behind the peaks of the waves. At the beginning of the waves, the increasing transport power of the water and the loose material can be considered as the cause for this result. The high stream velocity behind the wave peaks explains the increase in the bedload transport so that material from the channel beds is unfastened and will be mobilized. The characterization of the bedload regarding the shape and mass is still limited regarding the field measurements and could be solved only for homogeneous grain sizes and single stones under laboratory conditions. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
174.
Kerstin Kolditz Olaf Dellwig Jan Barkowski Thomas H. Badewien Holger Freund Hans-Jürgen Brumsack 《Geo-Marine Letters》2012,32(1):49-60
De-embankment in the salt marshes of the island of Langeoog was carried out in 2004, thereby inducing an artificial transgression
within an area of 2.2 km2. Material from three suspended matter traps (SMTs) located along a N–S transect was collected monthly between January 2006
and February 2007. Besides geochemical (major and trace elements) and grain-size analyses, the duration and height of water
cover were continuously measured by pressure gauges during the sampling period at two sites, thus revealing inundation frequency
(max. 280 year−1) and level (max. 2.4 m). Generally, the silt-dominated SMT material exhibits a geochemical composition similar to that of
suspended particulate matter from the adjacent Wadden Sea. However, distinctly increasing enrichments of TOC, P, Mn and Mo
from the shoreline towards the higher salt marsh clearly indicate fractionation processes during material transport. Geochemical
comparison with older Holocene coastal deposits reveals a mixture of brackish and tidal flat sediments, thus reflecting an
early stage of sea-level rise and the development from a terrestrial towards a marine-dominated system. Sedimentation rates
are higher than the local sea-level rise, as revealed by vertical salt marsh growth. Storm surges deliver the highest amounts
of sediment and play an important role in salt marsh accumulation within the study area. Average accumulation rates of TOC
(780 t year−1), P (54 t year−1) and Mn (5.2 t year−1) in the de-embanked area suggest that the former sand-dominated sediments currently receive significant amounts of reactive
organic-rich material, thus fostering biogeochemical cycling. 相似文献
175.
Michael Marks Pavel Kroupa Holger Baumgardt 《Monthly notices of the Royal Astronomical Society》2008,386(4):2047-2054
Recently, De Marchi, Paresce & Pulone studied a sample of 20 globular clusters and found that all clusters with high concentrations have steep stellar mass functions while clusters with low concentration have comparatively shallow mass functions. No globular clusters were found with a flat mass function and high concentration. This seems curious since more concentrated star clusters are believed to be dynamically more evolved and should have lost more low-mass stars via evaporation, which would result in a shallower mass function in the low-mass part.
We show that this effect can be explained by residual-gas expulsion from initially mass segregated star clusters, and is enhanced further through unresolved binaries. If gas expulsion is the correct mechanism to produce the observed trend in the c –α -plane, then observation of these parameters would allow to constrain cluster starting conditions such as star formation efficiency and the time-scale of gas expulsion. 相似文献
We show that this effect can be explained by residual-gas expulsion from initially mass segregated star clusters, and is enhanced further through unresolved binaries. If gas expulsion is the correct mechanism to produce the observed trend in the c –α -plane, then observation of these parameters would allow to constrain cluster starting conditions such as star formation efficiency and the time-scale of gas expulsion. 相似文献
176.
Juan Liu Jin Wang Yongheng Chen Jianying Qi Holger Lippold Chunlin Wang 《洁净——土壤、空气、水》2010,38(10):909-915
Thallium (Tl) is a rare element of high toxicity. Sediments sampled in three representative locations near industries utilizing Tl‐containing raw materials from the Pearl River Basin, China were analyzed for their total Tl contents and the Tl contents in four sequentially extracted fractions (i.e., weak acid exchangeable, reducible, oxidizable, and residual fraction). The results reveal that the total Tl contents (1.25–19.1 µg/g) in the studied sediments were slightly high to quite high compared with those in the Chinese background sediments. This indicates the apparent Tl contamination of the investigated sediments. However, with respect to the chemical fractions, Tl is mainly associated with the residual fraction (>60%) of the sediments, especially of those from the mining area of Tl‐bearing pyrite minerals, indicating the relatively low mobility, and low bioavailability of Tl in these sediments. This obviously contrasts with the previous findings that Tl is mainly entrapped in the first three labile fractions of the contaminated samples. Possible reasons were given for the dominating association of Tl with the residual fraction (>95%) of the mining area sediments. The significant role of certain K‐containing silicates or minerals of these sediments on retaining Tl in the residual fraction, discovered by this study, provides a special field of research opportunity for the Tl‐containing wastewater treatment. 相似文献
177.
Holger Pedersen Claudio Canut de Bon Harri Lindgren 《Meteoritics & planetary science》1992,27(2):126-135
Abstract A field investigation is presented of the strewnfield of the mesosiderite Vaca Muerta, originally found in 1861. The area, 11.5 km long, 2.1 km wide, is located about 60 km southeast of Taltal, Chile, in the Atacama Desert. It has yielded 80 meteorites with a total mass exceeding 3782 kg. Most fragments were found in an undisturbed state, but some had been broken by prospectors. The present studies, in connection with historical records, indicate that the original mass of Vaca Muerta exceeded 6 metric tons. One impact feature, somewhat modified by man, consists of a 10.5-m diameter, 1.7-m deep hole, without an uplifted rim. Small masses were scattered up to 85 m from the hole. 相似文献
178.
179.
In the deep subsurface of the northeast German basin products of extensive volcanism are present that formed during the waning
phase of the Variscan orogeny (Permian–Carboniferous boundary). Large volumes (≥48,000 km3) of dominantly felsic magma were emplaced in the northern foreland of the Variscan mountains in a terrestrial semi-arid environment.
Most of these units were inferred by previous authors to represent the products of explosive volcanic eruptions such as ignimbrites.
However, a detailed analysis of the volcanic texture and lithofacies association shows that most units are best interpreted
as coherent lavas emplaced either as extrusive units or as shallow intrusions, with important implications for the reconstruction
of the paleo-environment. This study shows that detailed textural examination of drill cores provide important observations,
which can be applied as criteria for the interpretation of the mode of volcanic eruptions. Furthermore, phenocryst logging
and geochemical fingerprinting based on immobile element ratios can be employed for the classification and discrimination
of individual emplacement units. 相似文献
180.
Climate variability and change affects individuals and societies. Within agricultural systems, seasonal climate forecasting
can increase preparedness and lead to better social, economic and environmental outcomes. However, climate forecasting is
not the panacea to all our problems in agriculture. Instead, it is one of many risk management tools that sometimes play an
important role in decision-making. Understanding when, where and how to use this tool is a complex and multi-dimensional problem. To do this effectively, we suggest a participatory, cross-disciplinary
research approach that brings together institutions (partnerships), disciplines (e.g., climate science, agricultural systems
science, rural sociology and many other disciplines) and people (scientist, policy makers and direct beneficiaries) as equal
partners to reap the benefits from climate knowledge. Climate science can provide insights into climatic processes, agricultural
systems science can translate these insights into management options and rural sociology can help determine the options that
are most feasible or desirable from a socio-economic perspective. Any scientific breakthroughs in climate forecasting capabilities
are much more likely to have an immediate and positive impact if they are conducted and delivered within such a framework.
While knowledge and understanding of the socio-economic circumstances is important and must be taken into account, the general
approach of integrated systems science is generic and applicable in developed as well as in developing countries. Examples
of decisions aided by simulation output ranges from tactical crop management options, commodity marketing to policy decisions
about future land use. We also highlight the need to better understand temporal- and spatial-scale variability and argue that
only a probabilistic approach to outcome dissemination should be considered. We demonstrated how knowledge of climatic variability
(CV), can lead to better decisions in agriculture, regardless of geographical location and socio-economic conditions. 相似文献