全文获取类型
收费全文 | 93篇 |
免费 | 2篇 |
专业分类
大气科学 | 2篇 |
地球物理 | 30篇 |
地质学 | 50篇 |
海洋学 | 1篇 |
天文学 | 9篇 |
自然地理 | 3篇 |
出版年
2021年 | 2篇 |
2020年 | 1篇 |
2018年 | 8篇 |
2017年 | 4篇 |
2016年 | 5篇 |
2015年 | 6篇 |
2014年 | 6篇 |
2013年 | 5篇 |
2012年 | 3篇 |
2011年 | 10篇 |
2010年 | 2篇 |
2009年 | 8篇 |
2008年 | 2篇 |
2007年 | 3篇 |
2006年 | 1篇 |
2005年 | 3篇 |
2004年 | 1篇 |
2003年 | 1篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1986年 | 1篇 |
1982年 | 1篇 |
1979年 | 3篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1972年 | 1篇 |
1970年 | 1篇 |
1968年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有95条查询结果,搜索用时 15 毫秒
51.
GIS-based hydrogeological databases and groundwater modelling 总被引:4,自引:2,他引:2
Radu Gogu Guy Carabin Vincent Hallet Valerie Peters Alain Dassargues 《Hydrogeology Journal》2001,9(6):555-569
Reliability and validity of groundwater analysis strongly depend on the availability of large volumes of high-quality data.
Putting all data into a coherent and logical structure supported by a computing environment helps ensure validity and availability
and provides a powerful tool for hydrogeological studies. A hydrogeological geographic information system (GIS) database that
offers facilities for groundwater-vulnerability analysis and hydrogeological modelling has been designed in Belgium for the
Walloon region. Data from five river basins, chosen for their contrasting hydrogeological characteristics, have been included
in the database, and a set of applications that have been developed now allow further advances. Interest is growing in the
potential for integrating GIS technology and groundwater simulation models. A "loose-coupling" tool was created between the
spatial-database scheme and the groundwater numerical model interface GMS (Groundwater Modelling System). Following time and
spatial queries, the hydrogeological data stored in the database can be easily used within different groundwater numerical
models.
Electronic Publication 相似文献
52.
Radu?Constantin?GoguEmail author Vincent?Hallet Alain?Dassargues 《Environmental Geology》2003,44(8):881-892
Five different methods for assessing intrinsic aquifer vulnerability were tested in a case study and their results compared. The test area was a slightly karstified district in the Condroz region of Belgium. The basin covers about 65 km2 and the karst aquifer provides a water-supply of about 28,000 m3d-1. The methods tested were: EPIK (Doerfliger et al. 1999), DRASTIC (Aller et al. 1987), 'German method' (von Hoyer and Söfner 1998), GOD (Foster 1987) and ISIS (Civita and De Regibus 1995). The results are compared and critically examined. From the analysis, it seems that reducing the number of parameters is unsatisfactory, due to the variety of geological conditions. The various methods produce very different results at any given site. As only physically-based methods can be checked for their reliability, it is clear that future vulnerability mapping techniques must incorporate such methods. 相似文献
53.
Amplitude versus offset information is a key feature to seismic reservoir characterization. Therefore amplitude preserving migration was developed to obtain this information from seismic reflection data. For complex 3-D media, however, this process is computationally expensive. In this paper we present an efficient traveltime based strategy for amplitude preserving migration of the Kirchhoff type. Its foundations are the generation of traveltime tables using a wavefront-oriented ray-tracing technique, and a generalized moveout relation for 3-D heterogeneous media. All required quantities for the amplitude preserving migration are computed from coarsely gridded traveltime tables. The migration includes the interpolation from the coarsely gridded input traveltimes onto the fine migration grid, the computation of amplitude preserving weight functions, and, optionally, the evaluation of an optimized migration aperture. Since ray tracing is employed for the traveltime computation the input velocity model needs to be smooth, i.e. velocity variations of spatial dimensions below the wavelength of the considered reflection signals are removed. Numerical examples on simple generic models validate the technique and an application to the Marmousi model demonstrates its potential to complex media. The major advantage of the traveltime based strategy consists of its computational efficiency by maintaining sufficient accuracy. Considerable savings in storage space (105 and more for 3-D data with respect to no interpolation at all) can be achieved. The computational time for the stack can be substantially reduced (up to 90% in 3-D) with the optimized migration aperture since only those traces are stacked which really contribute to the image point under consideration. 相似文献
54.
Etienne Balan Michele Lazzeri Simon Delattre Merlin Méheut Keith Refson Bjoern Winkler 《Physics and Chemistry of Minerals》2007,34(9):621-625
The theoretical anharmonicity of the inner-OH stretching modes of kaolinite and lizardite is determined using a frozen-phonon
approach. The anharmonicity parameter, defined as the difference between half the first overtone frequency and the frequency
of the fundamental transition, is −95 and −92 cm−1 for kaolinite and lizardite, respectively. These values are consistent with the experimental measurements. The very good
agreement usually observed between harmonic calculations of vibrational frequencies at the density functional theory (DFT)
level, using the generalized gradient approximation (GGA), and experimental positions of vibrational bands results from the
fortuitous, but almost exact, cancelation of two types of errors. One is related to the GGA approximation and the other to
the neglect of anharmonicity. 相似文献
55.
56.
57.
Sensitivity analysis for the EPIK method of vulnerability assessment in a small karstic aquifer, southern Belgium 总被引:5,自引:0,他引:5
Applying the EPIK parametric method, a vulnerability assessment has been made for a small karstic groundwater system in southern
Belgium. The aquifer is a karstified limestone of Devonian age. A map of intrinsic vulnerability of the aquifer and of the
local water-supply system shows three vulnerability areas. A parameter-balance study and a sensitivity analysis were performed
to evaluate the influence of single parameters on aquifer-vulnerability assessment using the EPIK method. This approach provides
a methodology for the evaluation of vulnerability mapping and for more reliable interpretation of vulnerability indices for
karst groundwater resources.
Received, March 1999/Revised, December 1999, February 2000/Accepted, February 2000 相似文献
58.
Etienne Balan Marc Blanchard Jean-François Hochepied Michele Lazzeri 《Physics and Chemistry of Minerals》2008,35(5):279-285
The theoretical infrared (IR) and Raman spectra of bayerite (β-Al(OH)3) are computed in the density functional theory framework, using the linear response theory. The results are consistent with
the occurrence of six non-equivalent OH groups in a bayerite structure with space group P21/n. Similar to gibbsite, the transmission powder IR spectrum of bayerite in the region of the OH stretching bands is found to
depend on the shape of particles. In particular, the broadening of the strong band observed at about 3,460 cm−1 in the spectrum of Al hydroxides is related to the electrostatic charges occurring at the surface of the polarized dielectric
particles. The experimental correlation observed between the shape of this band and morphological parameters has therefore
a physical, instead of chemical, origin. 相似文献
59.
The effect of fluctuating daily surface fluxes on the time-mean oceanic circulation is studied using an empirical flux model.
The model produces fluctuating fluxes resulting from atmospheric variability and includes oceanic feedbacks on the fluxes.
Numerical experiments were carried out by driving an ocean general circulation model with three different versions of the
empirical model. It is found that fluctuating daily fluxes lead to an increase in the meridional overturning circulation (MOC)
of the Atlantic of about 1 Sv and a decrease in the Antarctic circumpolar current (ACC) of about 32 Sv. The changes are approximately
7% of the MOC and 16% of the ACC obtained without fluctuating daily fluxes. The fluctuating fluxes change the intensity and
the depth of vertical mixing. This, in turn, changes the density field and thus the circulation. Fluctuating buoyancy fluxes
change the vertical mixing in a non-linear way: they tend to increase the convective mixing in mostly stable regions and to
decrease the convective mixing in mostly unstable regions. The ACC changes are related to the enhanced mixing in the subtropical
and the mid-latitude Southern Ocean and reduced mixing in the high-latitude Southern Ocean. The enhanced mixing is related
to an increase in the frequency and the depth of convective events. As these events bring more dense water downward, the mixing
changes lead to a reduction in meridional gradient of the depth-integrated density in the Southern Ocean and hence the strength
of the ACC. The MOC changes are related to more subtle density changes. It is found that the vertical mixing in a latitudinal
strip in the northern North Atlantic is more strongly enhanced due to fluctuating fluxes than the mixing in a latitudinal
strip in the South Atlantic. This leads to an increase in the density difference between the two strips, which can be responsible
for the increase in the Atlantic MOC. 相似文献
60.
Characterization of coal reservoirs and determination of in-situ physical coal properties related to transport mechanism are complicated due to having lack of standard procedures in the literature. By considering these difficulties, a new approach has been developed proposing the usage of relationships between coal rank and physical coal properties. In this study, effects of shrinkage and swelling (SS) on total methane recovery at CO2 breakthrough (TMRB), which includes ten-year primary methane recovery and succeeding enhanced coalbed methane (ECBM) recovery up to CO2 breakthrough, and CO2 sequestration have been investigated by using rank-dependent coal properties. In addition to coal rank, different coal reservoir types, molar compositions of injected fluid, and parameters within the extended Palmer & Mansoori (P&M) permeability model were considered. As a result of this study, shrinkage and swelling lead to an increase in TMRB. Moreover, swelling increased CO2 breakthrough time and decreased displacement ratio and CO2 storage for all ranks of coal. Low-rank coals are affected more negatively than high-rank coals by swelling. Furthermore, it was realized that dry coal reservoirs are more influenced by swelling than others and saturated wet coals are more suitable for eliminating the negative effects of CO2 injection. In addition, it was understood that it is possible to reduce swelling effect of CO2 on cleat permeability by mixing it with N2 before injection. However, an economical optimization is required for the selection of proper gas mixture. Finally, it is concluded from sensitivity analysis that elastic modulus is the most important parameter, except the initial cleat porosity, controlling SS in the extended P&M model by highly affecting TMRB. 相似文献