全文获取类型
收费全文 | 114篇 |
免费 | 0篇 |
国内免费 | 8篇 |
专业分类
测绘学 | 13篇 |
大气科学 | 8篇 |
地球物理 | 19篇 |
地质学 | 57篇 |
海洋学 | 7篇 |
天文学 | 16篇 |
自然地理 | 2篇 |
出版年
2024年 | 1篇 |
2022年 | 1篇 |
2019年 | 1篇 |
2018年 | 2篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 3篇 |
2014年 | 2篇 |
2013年 | 10篇 |
2012年 | 1篇 |
2011年 | 9篇 |
2010年 | 7篇 |
2009年 | 9篇 |
2008年 | 2篇 |
2007年 | 6篇 |
2006年 | 8篇 |
2005年 | 5篇 |
2004年 | 8篇 |
2003年 | 2篇 |
2002年 | 1篇 |
2001年 | 2篇 |
2000年 | 4篇 |
1999年 | 3篇 |
1996年 | 2篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1971年 | 1篇 |
1968年 | 2篇 |
1967年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有122条查询结果,搜索用时 468 毫秒
71.
GOCE gravitational gradiometry 总被引:16,自引:6,他引:10
GOCE is the first gravitational gradiometry satellite mission. Gravitational gradiometry is the measurement of the second derivatives of the gravitational potential. The nine derivatives form a 3 × 3 matrix, which in geodesy is referred to as Marussi tensor. From the basic properties of the gravitational field, it follows that the matrix is symmetric and trace free. The latter property corresponds to Laplace equation, which gives the theoretical foundation of its representation in terms of spherical harmonic or Fourier series. At the same time, it provides the most powerful quality check of the actual measured gradients. GOCE gradiometry is based on the principle of differential accelerometry. As the satellite carries out a rotational motion in space, the accelerometer differences contain angular effects that must be removed. The GOCE gradiometer provides the components V xx , V yy , V zz and V xz with high precision, while the components V xy and V yz are of low precision, all expressed in the gradiometer reference frame. The best performance is achieved inside the measurement band from 5 × 10–3 to 0.1 Hz. At lower frequencies, the noise increases with 1/f and is superimposed by cyclic distortions, which are modulated from the orbit and attitude motion into the gradient measurements. Global maps with the individual components show typical patterns related to topographic and tectonic features. The maps are separated into those for ascending and those for descending tracks as the components are expressed in the instrument frame. All results are derived from the measurements of the period from November to December 2009. While the components V xx and V yy reach a noise level of about \({10\;\rm{\frac{mE}{\sqrt{Hz}}}}\), that of V zz and V xz is about \({20\; \rm{\frac{mE}{\sqrt{Hz}}}}\). The cause of the latter’s higher noise is not yet understood. This is also the reason why the deviation from the Laplace condition is at the \({20 \;\rm{\frac{mE}{\sqrt{Hz}}}}\) level instead of the originally planned \({11\;\rm{\frac{mE}{\sqrt{Hz}}}}\). Each additional measurement cycle will improve the accuracy and to a smaller extent also the resolution of the spherical harmonic coefficients derived from the measured gradients. 相似文献
72.
Cornelius Fischer Stephan Kaufhold Wanja Wedekind Reiner Dohrmann Volker Karius Siegfried Siegesmund 《Environmental Earth Sciences》2011,63(7-8):1665-1676
Building stones manufactured from contact metamorphic slates (Fruchtschiefer slate) from Theuma (Sachsen, Germany) were investigated for mineralogical alterations as well as for changes in porosity and surface roughness due to weathering. After weathering periods of several years to decades, the originally dark gray-colored slates show pale spots of several centimeters in size at the surface of building stones. The dark-colored and light-colored sections of the slate show no differences in mineralogy. Surface weathering did not result in newly precipitated minerals. It was also found that the observed differences in color are not caused by variations in sedimentary organic carbon concentration or in sulfide/sulfate concentrations. Obtained results instead indicate that dark surface sections may show a thin cover of recent organic matter (OM), e.g., living OM, soot, dirt, etc. Microscopic investigations suggested that this cover was exfoliated at light-colored surface sections. The observed disaggregation of the upper 2 mm of the building block material results in an increase in porosity. Porosity of black (unweathered) slate is <2 vol.%. Due to weathering, the slate’s pores with diameters >1 μm show a significant increase in frequency compared to the original pore size distribution. Porosity of weathered rock volumes increased to approx. 8 vol.%. Discolored surface sections show a higher surface roughness (root-mean-square roughness, Rq ~ 1 μm) compared to dark-colored slate surfaces (Rq ~ 200 nm), both data are for cleavage planes. Preferentially, the discolored surface sections are located close to the edges of cut stones. This and the alteration in porosity, pore size, and surface roughness indicate that color changes of the slate are largely influenced by rock disaggregation proceeding from the edges into the center rather than by mineral dissolution/precipitation processes. 相似文献
73.
The new global gravity models represented by global spherical harmonics like EGM2008 require a high degree and order in their coefficients to resolve the gravity field in local areas; therefore, there are interests to represent the regional or local field by less parameters and to develop a parameter transformation from the global model to a local kind of spherical harmonic model. The authors use local spherical cap harmonics for the regional gravity potential representation related to a local pole and a local spherical coordinate system. This allows to model regional gravity potential with less parameters and less memory requirements in computation and storage. From different kinds of representations of spherical cap harmonics, we have selected the so-called adjusted spherical cap harmonics (ASCH). This is the most appropriate for the presented mathematical model of deriving its coefficients from global gravity models. In that way, the global gravity models can fully be exploited and mapped to regional ASCH, in particular with respect to the computation of regional geoid models with improved solution. 相似文献
74.
Weathering of volcanic tuff rocks caused by moisture expansion 总被引:1,自引:1,他引:0
Wanja Wedekind Rubén López-Doncel Reiner Dohrmann Mathias Kocher Siegfried Siegesmund 《Environmental Earth Sciences》2013,69(4):1203-1224
Moisture expansion in natural building stones is considered one of the most important factors affecting their weathering and deterioration. The processes that may be responsible for the expansion under determinate relative humidity (hygric dilatation) and water-saturated conditions (hydric dilatation) are generally attributed to the presence of swellable clay minerals. In contrast to this assumption, our investigations show that moisture expansion also takes place in volcanic tuff building stones almost free from clay minerals. To provide a deeper understanding of the processes, swelling and deterioration were performed on 14 volcanic tuffs used as important building stones of different ages, compositions and weathering stages from Mexico, Germany and Hungary. The investigations undertaken include extensive chemical, petrophysical and fabric analyses. The samples show a wide range of effective porosity, microporosity, capillary water absorption, moisture expansion, and CEC values. High moisture expansion does not seem to depend on clay mineral content alone. We also observed that there is no significant effect on dilatation if clay minerals are present but only form a thin coat on the outer shell of bigger pores. Moreover, we identified a correlation between microporosity, average pore radius and moisture expansion. The investigations highlight the fact that moisture expansion cannot only be attributed to swellable clay minerals, and suggest that the presence and accumulation of micropores and their average radius and distribution play an important role for non-clay associated swelling intensity, which can most probably be attributed to the disjoining pressure. 相似文献
75.
76.
Stabilization and global climate policy 总被引:1,自引:0,他引:1
Marcus C. Sarofim Chris E. Forest David M. Reiner John M. Reilly 《Global and Planetary Change》2005,47(2-4):266
Academic and political debates over long-run climate policy often invoke “stabilization” of atmospheric concentrations of greenhouse gases (GHGs), but only rarely are non-CO2 greenhouse gases addressed explicitly. Even though the majority of short-term climate policies propose trading between gases on a global warming potential (GWP) basis, discussions of whether CO2 concentrations should be 450, 550, 650 or perhaps as much as 750 ppm leave unstated whether there should be no additional forcing from other GHGs beyond current levels or whether separate concentration targets should be established for each GHG. Here, we use an integrated modeling framework to examine multi-gas stabilization in terms of temperature, economic costs, carbon uptake and other important consequences. We show that there are significant differences in both costs and climate impacts between different “GWP equivalent” policies and demonstrate the importance of non-CO2 GHG reduction on timescales of up to several centuries. 相似文献
77.
Sonoyo Mukai Tadashi Mukai Richard H. Giese Karin Weiss Reiner H. Zerull 《Earth, Moon, and Planets》1982,26(2):197-208
Intensity and polarization of scattered light by an absorbing spherical particle with a random rough surface and with a radius larger than the wavelength of radiation are investigated. Multiple reflections of incident light on the rough surface are treated based on the multiple scattering theory.Within the limits of our approximation the model gives good agreement with typical scattering features by irregular shaped particles derived by microwave analogue experiments and laser measurements, namely a backward enhancement of the intensity, and a reduction of magnitude of polarization.Our treatment will be provide a powerful tool for studying scattering problems of interstellar and/or interplanetary grains as well as those of asteroids and the Moon. 相似文献
78.
G. Fischer G. Karakas M. Blaas V. Ratmeyer N. Nowald R. Schlitzer P. Helmke R. Davenport B. Donner S. Neuer G. Wefer 《International Journal of Earth Sciences》2009,98(2):281-298
The ocean off NW Africa is the second most important coastal upwelling system with a total annual primary production of 0.33 Gt
of carbon per year (Carr in Deep Sea Res II 49:59–80, 2002). Deep ocean organic carbon fluxes measured by sediment traps are also fairly high despite low biogenic opal fluxes. Due
to a low supply of dissolved silicate from subsurface waters, the ocean off NW Africa is characterized by predominantly carbonate-secreting
primary producers, i.e. coccolithophorids. These algae which are key primary producers since millions of years are found in
organic- and chlorophyll-rich zooplankton fecal pellets, which sink rapidly through the water column within a few days. Particle
flux studies in the Mauretanian upwelling area (Cape Blanc) confirm the hypothesis of Armstrong et al. (Deep Sea Res II 49:219–236,
2002) who proposed that ballast availability, e.g. of carbonate particles, is essential to predict deep ocean organic carbon fluxes.
The role of dust as ballast mineral for organic carbon, however, must be also taken into consideration in the coastal settings
off NW Africa. There, high settling rates of larger particles approach 400 m day−1, which may be due to a particular composition of mineral ballast. An assessment of particle settling rates from opal-production
systems in the Southern Ocean of the Atlantic Sector, in contrast, provides lower values, consistent with the assumptions
of Francois et al. (Global Biogeochem Cycles 16(4):1087, 2002). Satellite chlorophyll distributions, particle distributions and fluxes in the water column off NW Africa as well as modelling
studies suggest a significant lateral flux component and export of particles from coastal shelf waters into the open ocean.
These transport processes have implications for paleo-reconstructions from sediment cores retrieved at continental margin
settings. 相似文献
79.
M. J. Reiner K. Goetz J. Fainberg M. L. Kaiser M. Maksimovic B. Cecconi S. Hoang S. D. Bale J.-L. Bougeret 《Solar physics》2009,259(1-2):255-276
The twin STEREO and the Wind spacecraft make remote multipoint measurements of interplanetary radio sources of solar origin from widely separated vantage points. One year after launch, the angular separation between the STEREO spacecraft reached 45°, which was ideal for locating solar type III radio sources in the heliosphere by three-spacecraft triangulation measurements from STEREO and Wind. These triangulated source locations enable intrinsic properties of the radio source, such as its beaming characteristics, to be deduced. We present the first three-point measurements of the beaming characteristics for two solar type III radio bursts that were simultaneously observed by the three spacecraft in December of 2007 and in January of 2008. These analyses suggest that individual type III bursts exhibit a wide beaming pattern that is approximately beamed along the direction tangent to the Parker spiral magnetic field line at the source location. 相似文献
80.
M. J. Reiner K.-L. Klein M. Karlický K. Jiřička A. Klassen M. L. Kaiser J.-L. Bougeret 《Solar physics》2008,249(2):337-354
We report here on the solar origin of distinctive radiation characteristics observed for a decametric type III solar radio burst that was associated with a major solar flare and CME on 11 April 2001. The associated decimeter (Ond?ejov) and meter (Potsdam) wavelength emissions, as well as the GOES soft X-ray lightcurve, suggest that there were two successive events of energy release and electron acceleration associated with this solar eruption. The Nançay radioheliograph images and additional evidence of plasmoid propagation suggest that the second event of electron acceleration resulted from coronal reconfigurations, likely caused by the erupting CME. These observational analyses provide new insights into the physical origin of the distinguishing characteristics of complex type III-like radio emissions that are typically observed at decameter wavelengths during major solar eruptive events. 相似文献