全文获取类型
收费全文 | 517篇 |
免费 | 26篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 14篇 |
大气科学 | 43篇 |
地球物理 | 105篇 |
地质学 | 182篇 |
海洋学 | 35篇 |
天文学 | 137篇 |
综合类 | 2篇 |
自然地理 | 29篇 |
出版年
2022年 | 2篇 |
2021年 | 14篇 |
2020年 | 3篇 |
2019年 | 3篇 |
2018年 | 18篇 |
2017年 | 18篇 |
2016年 | 29篇 |
2015年 | 12篇 |
2014年 | 25篇 |
2013年 | 27篇 |
2012年 | 27篇 |
2011年 | 29篇 |
2010年 | 37篇 |
2009年 | 45篇 |
2008年 | 25篇 |
2007年 | 35篇 |
2006年 | 24篇 |
2005年 | 24篇 |
2004年 | 25篇 |
2003年 | 17篇 |
2002年 | 17篇 |
2001年 | 12篇 |
2000年 | 13篇 |
1999年 | 7篇 |
1998年 | 10篇 |
1997年 | 3篇 |
1996年 | 5篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 7篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 5篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1948年 | 1篇 |
1922年 | 1篇 |
排序方式: 共有547条查询结果,搜索用时 15 毫秒
111.
112.
113.
Ralf Seidler Kateryna Padalkina H. Martin Bücker Anozie Ebigbo Michael Herty Gabriele Marquart Jan Niederau 《Computational Geosciences》2016,20(2):375-383
During geothermal reservoir development, drilling deep boreholes turns out to be extremely expensive and risky. Thus, it is of great importance to work out the details of suitable borehole locations in advance. Here, given a set of existing boreholes, we demonstrate how a sophisticated numerical technique called optimal experimental design helps to find a location of an additional exploratory borehole that reduces risk and, ultimately, saves cost. More precisely, the approach minimizes the uncertainty when deducing the effective permeability of a buried reservoir layer from a temperature profile measured in this exploratory borehole. In this paper, we (1) outline the mathematical formulation in terms of an optimization problem, (2) describe the numerical implementation involving various software components, and (3) apply the method to a 3D numerical simulation model representing a real geothermal reservoir in northern Italy. Our results show that optimal experimental design is conceptually and computationally feasible for industrial-scale applications. For the particular reservoir and the estimation of permeability from temperature, the optimal location of the additional borehole coincides with regions of high flow rates and large deviations from the mean temperature of the reservoir layer in question. Finally, the presentation shows that, methodologically, the optimization method can be generalized from estimating permeability to finding any other reservoir properties. 相似文献
114.
Erich Kaiser 《International Journal of Earth Sciences》1922,13(4):321-326
Ohne Zusammenfassung 相似文献
115.
116.
R. Kaiser 《地球物理与天体物理流体动力学》2013,107(1-2):125-135
Abstract Bayly (1993) introduced and investigated the equation (? t + v·▽-η ▽2)S = RS as a scalar analogue of the magnetic induction equation. Here, S(r, t) is a scalar function and the flow field v(r, t) and “stretching” function R(r, t) are given independently. This equation is much easier to handle than the corresponding vector equation and, although not of much relevance to the (vector) kinematic dynamo problem, it helps to study some features of the fast dynamo problem. In this note the scalar equation is considered for linear flow and a harmonic potential as stretching function. The steady equation separates into one-dimensional equations, which can be completely solved and therefore allow one to monitor the behaviour of the spectrum in the limit of vanishing diffusivity. For more general homogeneous flows a scaling argument is given which ensures fast dynamo action for certain powers of the harmonic potential. Our results stress the singular behaviour of eigenfunctions in the limit of vanishing diffusivity and the importance of stagnation points in the flow for fast dynamo action. 相似文献
117.
Dominika Kalasov Tom Zikmund Pavel Spurný Jakub Haloda Jií Borovi
ka Jozef Kaiser 《Meteoritics & planetary science》2020,55(5):1073-1081
A very bright and long bolide was observed over the eastern part of the Czech Republic during late local evening on December 9, 2014. This bolide was recorded by professional instruments in the Czech part of the European Fireball Network. Three meteorites weighing in total 87 g were found in the predicted area and were named ??ár nad Sázavou. The complete material composition of the meteorite was obtained from one cut‐off piece using petrography, mineralogy, and scanning electron microscopy (together with X‐ray energy dispersive spectroscopy and wavelength dispersive spectroscopy). X‐ray computed tomography (CT) was applied on all pieces for the determination of their grain and bulk density, digitization of shape, and examination of the structural homogeneity. CT has proved its important role for nondestructive exploration of brecciated meteorites formed by distinct lithologies or petrological types. In this article, we discuss its limits in terms of structural and material resolution based on the correlation of state‐of‐the‐art CT data and SEM images. Furthermore, we introduce a new way of air cavity quantification, which distinguishes the natural porosity of meteorite and cracks related to erosion processes. This helps to discuss the presence of weathering products based on comparison of the meteorite pieces found at different times after impact. 相似文献
118.
Roberto P. Saglia Jan Snigula Robert Senger Ralf Bender 《Experimental Astronomy》2013,35(1-2):337-344
We describe the implementation of the PhotoZ code in the framework of the Astro-WISE package and as part of the Photometric Classification Server of the PanSTARRS pipeline. Both systems allow the automatic measurement of photometric redshifts for the millions of objects being observed in the PanSTARRS project or expected to be observed by future surveys like KIDS, DES or EUCLID. 相似文献
119.
We report the detection and analysis of circular polarization in solar type III radio storms at hectometric-to-kilometric
wavelengths. We find that a small (usually less than 5%), but statistically significant, degree of circular polarization is
present in all interplanetary type III radio storms below 1 MHz. The sense of the polarization, which is right-hand circular
for some storms and left-hand circular for others, is maintained for the entire duration of the type III storm (usually many
days). For a given storm, the degree of circular polarization peaks near central meridian crossing of the associated active
region. At a given time, the degree of circular polarization is found to generally vary as the logarithm of the observing
frequency. The radiation characteristics, including the polarization, for one interplanetary type III storm exhibits an unusual
1.6 hour oscillation. Based on the standard plasma emission theory of type III radiation, we discuss the implications of these
observations for the magnitude and radial dependence of the solar magnetic field above active regions on the Sun. 相似文献
120.
Johann Friedrich Tolksdorf Knut Kaiser 《Boreas: An International Journal of Quaternary Research》2012,41(3):408-421
Aeolian sands are widespread in the European sand‐belt. While there is a consensus about the timing of increased aeolian activity and, in contrast, of surface stabilization during the Lateglacial, knowledge about Holocene aeolian dynamics is still very sparse. It is generally assumed that aeolian processes have been closely connected to human activities since at least the Neolithic period. A compilation of 189 luminescence dates from aeolian sands of Holocene age and 301 14C‐dates from palaeo‐surfaces, comprising palaeosols, buried peats and archaeological features from the whole sand‐belt, is plotted as histograms and kernel density plots and divided into sub‐phases by cluster analysis. This is also done separately for the dates from the areas west and east of the river Elbe. Our results show that aeolian activity did not cease with the end of the Younger Dryas but continued in the whole European sand‐belt until the Mid‐Atlantic (c. 6500 a BP), presenting evidence of vegetation‐free areas at least at the local scale. During the subsequent time period evidence of aeolian sedimentation is sparse, and surface stabilization is indicated by a cluster of palaeo‐surfaces ascribed to the early Subboreal (c. 5000 cal. a BP). The agglomeration of luminescence ages around 4000 years is probably connected with intensified land use during the Late Neolithic. Younger phases of aeolian sedimentation are indicated by clusters of luminescence ages around 1800 years, a group of luminescence ages from the Netherlands and NW Germany around 900 years, and a group of ages around 680 years in Germany. Among the dates from palaeo‐surfaces, clusters were identified around 2700, 1300 and 900 cal. a BP as well as around 690 cal. a BP in the western part and 610 cal. a BP in the eastern part of the sand‐belt. The clusters within the luminescence ages and the 14C‐dates coincide with phases where increased human impact can be deduced from archaeological and historical sources as well as from environmental history. 相似文献