全文获取类型
收费全文 | 545篇 |
免费 | 8篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 10篇 |
大气科学 | 7篇 |
地球物理 | 148篇 |
地质学 | 236篇 |
海洋学 | 37篇 |
天文学 | 61篇 |
综合类 | 1篇 |
自然地理 | 55篇 |
出版年
2019年 | 6篇 |
2018年 | 4篇 |
2017年 | 10篇 |
2016年 | 9篇 |
2015年 | 4篇 |
2014年 | 17篇 |
2013年 | 26篇 |
2012年 | 13篇 |
2011年 | 23篇 |
2010年 | 22篇 |
2009年 | 22篇 |
2008年 | 22篇 |
2007年 | 16篇 |
2006年 | 25篇 |
2005年 | 10篇 |
2004年 | 9篇 |
2003年 | 15篇 |
2002年 | 11篇 |
2001年 | 15篇 |
2000年 | 5篇 |
1999年 | 9篇 |
1998年 | 6篇 |
1997年 | 9篇 |
1995年 | 7篇 |
1994年 | 8篇 |
1993年 | 5篇 |
1991年 | 6篇 |
1990年 | 9篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 7篇 |
1984年 | 5篇 |
1983年 | 9篇 |
1982年 | 12篇 |
1981年 | 8篇 |
1980年 | 12篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1974年 | 7篇 |
1973年 | 5篇 |
1968年 | 4篇 |
1965年 | 6篇 |
1964年 | 4篇 |
1962年 | 4篇 |
1953年 | 5篇 |
1952年 | 4篇 |
1951年 | 5篇 |
1950年 | 4篇 |
1949年 | 8篇 |
排序方式: 共有555条查询结果,搜索用时 15 毫秒
281.
282.
283.
284.
Hanna Hadler Andreas Vött Timo Willershäuser Dennis Wilken Ruth Blankenfeldt Claus von Carnap-Bornheim Kurt Emde Peter Fischer Ulf Ickerodt Stefanie Klooß Bente Majchczack Lea Obrocki Wolfgang Rabbel 《地球表面变化过程与地形》2021,46(15):3228-3251
In ad 1362, a major storm surge drowned wide areas of cultivated medieval marshland along the north-western coast of Germany and turned them into tidal flats. This study presents a new methodological approach for the reconstruction of changing coastal landscapes developed from a study site in the Wadden Sea of North Frisia. Initially, we deciphered long-term as well as event-related short-term geomorphological changes, using a geoscientific standard approach of vibracoring, analyses of sedimentary, geochemical and microfaunal palaeoenvironmental parameters and radiocarbon dating. In a next step, Direct Push (DP)-based Cone Penetration Testing (CPT) and the Hydraulic Profiling Tool (HPT) were applied at vibracore locations to obtain in situ high-resolution stratigraphic data. In a last step, multivariate linear discriminant analysis (LDA) was successfully applied to efficiently identify different sedimentary facies (e.g., fossil marsh or tidal flat deposits) from the CPT and HPT test dataset, to map the facies' lateral distribution, also in comparison to reflection seismic measurements and test their potential to interpolate the borehole and CPT/HPT data. The training dataset acquired for the key site from coring and DP sensing finally allows an automated facies classification of CPT/HPT data obtained elsewhere within the study area. The new methodological approach allowed a detailed reconstruction of the local coastal landscape development in the interplay of natural marsh formation, medieval land reclamation and storm surge-related land losses. 相似文献
285.
286.
Xiao-Le Deng Thomas Grombein Wen-Bin Shen Bernhard Heck Kurt Seitz 《Journal of Geodesy》2016,90(6):585-587
287.
Martin B. Kalinowski Anders Axelsson Marc Bean Xavier Blanchard Theodore W. Bowyer Guy Brachet Simon Hebel Justin I. McIntyre Jana Peters Christoph Pistner Maria Raith Anders Ringbom Paul R. J. Saey Clemens Schlosser Trevor J. Stocki Thomas Taffary R. Kurt Ungar 《Pure and Applied Geophysics》2010,167(4-5):517-539
A global monitoring system for atmospheric xenon radioactivity is being established as part of the International Monitoring System that will verify compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT) once the treaty has entered into force. This paper studies isotopic activity ratios to support the interpretation of observed atmospheric concentrations of 135Xe, 133mXe, 133Xe and 131mXe. The goal is to distinguish nuclear explosion sources from civilian releases. Simulations of nuclear explosions and reactors, empirical data for both test and reactor releases as well as observations by measurement stations of the International Noble Gas Experiment (INGE) are used to provide a proof of concept for the isotopic ratio based method for source discrimination. 相似文献
288.
Kurt Friese Gerald Schmidt Jorge Carvalho de Lena Dieter W. Zachmann 《Limnologica》2010,40(2):114-125
The artificial reservoir Lagoa da Pampulha in central Brazil has been increasingly affected by sediment deposition and pollution from urban and industrial sources. This study investigates water chemistry and heavy metal concentrations and their fractionation in the lake sediment using ICP-OES, ICP-MS, and XRD analyses. Fractionation analysis was done by sequential extraction under inert gas as well as after oxidation. The lake exhibits a permanent stratification with an oxygen-free hypolimnion below 2 m depth. Nutrient concentrations are enriched for phosphorous components (SRP, PO4). In the sediment it was not possible to detect oxygen. Carbon, sulfur, and most of the analyzed heavy metals are enriched in the top sediment layer with a pronounced downward decrease, indicating the presence of an anthropogenic influence. Statistical analysis, including correlations and a Principal Component Analysis (PCA) of depth-related total concentration data, helps to distinguish presumably anthropogenic heavy metals from geogenic components. Some samples with high element concentrations in the sediment also show elevated concentrations in their pore water. Analyses of element distribution between sediment and pore water suggest a strong bonding of heavy metals to the anoxic sediment. The trend towards elevated solubility in the pore water of oxidized samples is clear for most of the analyzed elements. Fractionation analysis reveals characteristic associations of selected elements to specific mineral bonding forms. In addition, it indicates that the behavior of heavy metals in the sediment is strongly influenced by organic substances. These substances provide buffering against oxidation, acidification, and metal release. The high nutrient loading causes reducing conditions in the lake sediment. These conditions trigger the accumulation of sediments rich in S2−, which stabilizes the fixation of heavy elements. In the future, care must be taken to reduce the supply of contaminants and to prevent the release of heavy metals from sediments dredged for remediation purposes. 相似文献
289.
Simulating Martian regolith in the laboratory 总被引:1,自引:0,他引:1
Karsten Seiferlin Pascale Ehrenfreund Kurt Gunderson Günter Kargl Jonathan Peter Merrison 《Planetary and Space Science》2008,56(15):2009-2025
Regolith and dust cover the surfaces of the Solar Systems solid bodies, and thus constitute the visible surface of these objects. The topmost layers also interact with space or the atmosphere in the case of Mars, Venus and Titan. Surface probes have been proposed, studied and flown to some of these worlds. Landers and some of the mechanisms they carry, e.g. sampling devices, drills and subsurface probes (“moles”) will interact with the porous surface layer. The absence of true extraterrestrial test materials in ample quantities restricts experiments to the use of soil or regolith analogue materials. Several standardized soil simulants have been developed and produced and are commonly used for a variety of laboratory experiments. In this paper we intend to give an overview of some of the most important soil simulants, and describe experiments (penetrometry, thermal conductivity, aeolian transport, goniometry, spectroscopy and exobiology) made in various European laboratory facilities. 相似文献
290.
RWI_TOPO_2015 is a new high-resolution spherical harmonic representation of the Earth’s topographic gravitational potential that is based on a refined Rock–Water–Ice (RWI) approach. This method is characterized by a three-layer decomposition of the Earth’s topography with respect to its rock, water, and ice masses. To allow a rigorous separate modeling of these masses with variable density values, gravity forward modeling is performed in the space domain using tesseroid mass bodies arranged on an ellipsoidal reference surface. While the predecessor model RWI_TOPO_2012 was based on the \(5'\times 5'\) global topographic database DTM2006.0 (Digital Topographic Model 2006.0), the new RWI model uses updated height information of the \(1'\times 1'\) Earth2014 topography suite. Moreover, in the case of RWI_TOPO_2015, the representation in spherical harmonics is extended to degree and order 2190 (formerly 1800). Beside a presentation of the used formalism, the processing for RWI_TOPO_2015 is described in detail, and the characteristics of the resulting spherical harmonic coefficients are analyzed in the space and frequency domain. Furthermore, this paper focuses on a comparison of the RWI approach to the conventionally used rock-equivalent method. For this purpose, a consistent rock-equivalent version REQ_TOPO_2015 is generated, in which the heights of water and ice masses are condensed to the constant rock density. When evaluated on the surface of the GRS80 ellipsoid (Geodetic Reference System 1980), the differences of RWI_TOPO_2015 and REQ_TOPO_2015 reach maximum amplitudes of about 1 m, 50 mGal, and 20 mE in terms of height anomaly, gravity disturbance, and the radial–radial gravity gradient, respectively. Although these differences are attenuated with increasing height above the ellipsoid, significant magnitudes can even be detected in the case of the satellite altitudes of current gravity field missions. In order to assess their performance, RWI_TOPO_2015, REQ_TOPO_2015, and RWI_TOPO_2012 are validated against independent gravity information of current global geopotential models, clearly demonstrating the attained improvements in the case of the new RWI model. 相似文献