全文获取类型
收费全文 | 116篇 |
免费 | 6篇 |
专业分类
测绘学 | 4篇 |
大气科学 | 8篇 |
地球物理 | 32篇 |
地质学 | 62篇 |
海洋学 | 7篇 |
天文学 | 2篇 |
综合类 | 2篇 |
自然地理 | 5篇 |
出版年
2024年 | 1篇 |
2021年 | 4篇 |
2020年 | 5篇 |
2019年 | 2篇 |
2018年 | 6篇 |
2017年 | 3篇 |
2016年 | 8篇 |
2015年 | 6篇 |
2014年 | 5篇 |
2013年 | 10篇 |
2012年 | 9篇 |
2011年 | 6篇 |
2010年 | 8篇 |
2009年 | 3篇 |
2008年 | 5篇 |
2007年 | 8篇 |
2006年 | 3篇 |
2005年 | 1篇 |
2004年 | 1篇 |
2003年 | 1篇 |
2002年 | 2篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1986年 | 2篇 |
1983年 | 1篇 |
1955年 | 1篇 |
1952年 | 1篇 |
1948年 | 1篇 |
1926年 | 3篇 |
排序方式: 共有122条查询结果,搜索用时 15 毫秒
61.
Zdzisław M. Migaszewski Agnieszka Gałuszka Stanisław Hałas Józef Dąbek Sabina Dołęgowska Irena Budzyk Ewa Starnawska Artur Michalik 《Environmental Geology》2009,57(1):29-40
In 2005 and 2006, hydrogeochemical study was carried out in the bipartite Wiśniówka Mała pit lake of the Holy Cross Mountains
(south-central Poland). This is the largest acidic water body in Poland. This report presents the element concentrations in
the water and sediment, stable sulfur and oxygen isotope ratios in the soluble sulfates, and stable oxygen isotope ratio in
the water. The scope of the investigation also encompassed mineralogical examinations (scanning electron microscope, X-ray
diffraction) of the sediment. The results of this study show that there is a spatial and temporal variability in concentrations
of most elements and sulfur isotope ratios in the examined pit lake. The water of the western pond displayed a lower pH with
a mean of 3.73 and higher conductivity (390 μS cm−1) as well as higher concentrations of sulfates (156 mg L−1) and most of the cations and anions. The concentrations of Fe2+ and Fe3+ averaged 0.8 and 0.4 mg·L−1. In contrast, the eastern pond water revealed a higher pH (mean of 4.36), lower conductivity (293 μS cm−1) and lower sulfate (90 mg L−1) and trace metal levels. Similar variations were recorded in the stable sulfur isotope ratios. The δ34SV-CDT(SO4
2−) values in the water of the western pit pond were in the range of −6.7 to −4.6‰ (mean of −5.6‰), whereas that in the eastern
pit pond ranged from −2.2 to −0.9‰ (−1.6‰). The alkalinity of the entire lake water was below 0.1 mg·L−1 CaCO3. No distinct difference in the δ18OV-SMOW(SO4
2−) was noted between the western and eastern pit ponds. Compared to the Purple Pond in the Sudetes (Poland) and similar sites
throughout the world, the examined pit lake is highlighted by distinctly low concentrations of sulfates, iron and other trace
metals. Based on this and other studies performed in the Holy Cross Mountains, a conclusion can be drawn that the SO4
2− in the Wiśniówka Mała pit lake water is a mixture of SO4
2− derived from the following sources: (1) pyrite oxidation (especially in the western pond water), (2) leaching of soluble
sulfates from soils and waste material, as well as (3) subordinate deposition of airborne sulfate precipitation. 相似文献
62.
One of the best indicators of the potential erosion risks is the rainfall–runoff erosivity factor (R) of the revised universal soil loss equation (RUSLE). Frequently, however, there is not enough data available to compute the R value, and other parameters, such as the modified Fournier index (Fmod), are used instead. But RUSLE is less effective if only the alternative procedures exist. One of the major discrepancies between R and the alternative parameters is time resolution: individual storms are used to calculate R while monthly averages over the year are used to calculate Fmod.
In this study, a multiple linear regression (r2=0.89) involving monthly EI30, monthly rainfall for days with ≥10.0 mm and monthly number of days with rainfall ≥10.0 mm, for the Algarve region, is presented. Twenty-seven years of monthly rainfall erosivity values were computed for the 32 standard daily-read raingauge stations of the Algarve region. 相似文献
63.
Antonello De Luca Elena Mele Javier Molina Guido Verzeletti Artur V. Pinto 《地震工程与结构动力学》2001,30(8):1125-1145
An experimental test program on a full‐scale model representing a sub‐assemblage of the cloister facade of the Sao Vicente de Fora monastery, retrofitted through base isolation, has been recently carried out at the European Laboratory for Structural Assessment of the Joint Research Centre of the European Commission. In this paper an overview of the laboratory model and the experimental results is provided. In particular, firstly the test model is described, including the geometry and mechanical properties of the masonry specimen and the design of the isolation devices; then the testing method and the sub‐structuring of the isolation system are described and the seismic inputs adopted for the pseudo‐dynamic tests are defined. Finally, the experimental results are discussed and compared to the analogous results obtained on the ‘as is’, fixed‐base sub‐assemblage model. The implications of the test outcomes are emphasized and developments of this research line are presented. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
64.
65.
66.
José Augusto Costa Gonçalves Jorge Carvalho de Lena José Fernando Paiva Hermínio Arias Nalini Jr Janice Cardoso Pereira 《Environmental Geology》2007,53(4):785-793
In the city of Ouro Preto (MG), water catchment for public supply originates from superficial drainage, springs, old abandoned
mines and some driven wells. In the rocks of the region, As is originally found in gold-enriched sulphide-bearing mineral
deposits. The weathering process introduces As into the hydrological system by dissolution of this element into the leachate.
Measurement of the As content in the groundwater of some catchments was carried out during 1 year and these measurements demonstrated
high As content—up to 224 μg L−1 of As(V)—during the rainy season (the maximum concentration limit according to World Health Organization is 10 μg L−1). Lower values were observed during the dry season and in some sampling stations, As was not even detected. The As concentration
variability during 1 year shows a strict and direct relationship to seasonal and hydrological conditions. For city authorities,
responsible for public water supply, it is necessary to perform a complete inventory of the water sources used and constantly
monitor the As content in the water. 相似文献
67.
Experimental verification of effective anisotropic crack theories in variable crack aspect ratio medium
下载免费PDF全文
![点击此处可从《Geophysical Prospecting》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Jessica P. Henriques Jose J. S. de Figueiredo Leo K. Santos Daniel L. Macedo Icaro Coutinho Carolina B. da Silva Alberto L. Melo Mykel Sousa Felipe L. Azevedo 《Geophysical Prospecting》2018,66(1):141-156
Physical modelling of cracked/fractured media using downscaled laboratory experiments has been used with great success as a useful alternative for understanding the effect of anisotropy in the hydrocarbon reservoir characterization and in the crustal and mantle seismology. The main goal of this work was to experimentally verify the predictions of effective elastic parameters in anisotropic cracked media by Hudson and Eshelby–Cheng's effective medium models. For this purpose, we carried out ultrasonic measurements on synthetic anisotropic samples with low crack densities and different aspect ratios. Twelve samples were prepared with two different crack densities, 5% and 8%. Three samples for each crack density presented cracks with only one crack aspect ratio, whereas other three samples for each crack density presented cracks with three different aspect ratios in their composition. It results in samples with aspect ratio values varying from 0.13 to 0.26. All the cracked samples were simulated by penny‐shaped rubber inclusions in a homogeneous isotropic matrix made with epoxy resin. Moreover, an isotropic sample for reference was constructed with epoxy resin only. Regarding velocity predictions performed by the theoretical models, Eshelby–Cheng shows a better fit when compared with the experimental results for samples with single and mix crack aspect ratio (for both crack densities). From velocity values, our comparisons were also performed in terms of the ε, γ, and δ parameters (Thomsen parameters). The results show that Eshelby–Cheng effective medium model fits better with the measurements of ε and γ parameters for crack samples with only one type of crack aspect ratio. 相似文献
68.
Artur Radecki-Pawlik Karol Plesiński Bartosz Radecki-Pawlik Piotr Kuboń Russell Manson 《山地科学学报》2018,15(11):2335-2346
Boulder block ramps are river engineering structures used to stabilise river beds. Block ramps provide a semi-natural and aesthetically pleasing solution to certain river engineering problems in mountain streams. When constructing block ramps,one can use the dissipative behaviour of large macroroughness elements randomly placed on the river bed to enhance fish migration in an upstream direction thus, in this sense, meeting the requirements of the EU Water Framework Directive. Block ramps are often designed and constructed to replace damaged drop hydraulic structures in the channels of mountain streams. This paper investigates the resilience of a particular block ramp placed in the Krzczonówka stream(Polish Carpathians) in terms of the engineering design function and its durability against damaging. A hydrodynamic analysis of a block ramp is presented before and after a flood event that changed the configuration of the blocks. The seminatural unstructured hydraulic structure was built on the Krzczonowka stream to protect gas pipes which are located beneath it. As a result of several floods, the boulder block chute described in this paper was damaged, and some boulders were dislodged and transported downstream. Our post-flood investigations of bathymetry and velocity revealed that even damaged boulder blocks, removed from the chute and displaced downstream of the structure, still provide significant energy dissipation of the flowing water. The novel of our paper is for the first time showing very detailed analysis of unstructured block ramp hydrodynamics parameters done in the field.Also the novel finding of our investigations shows that before and after the flood event the unstructured block ramp structure, is still fish friendly in terms of hydrodynamics. 相似文献
69.
Six members of the annite–siderophyllite join were synthesized in a three step process – crystallization of biotite from
gels, decomposition of the fine-grained biotite under oxidizing conditions and resynthesis of Fe-Al biotite with planned compositions
from these products – producing biotite crystals with thicknesses of up to 10 μm. The biotite was characterized by microprobe,
electron microscopy and X-ray diffraction. Heat capacities of these biotites were measured with a DSC (differential scanning
calorimeter) over the temperature range 143 to 623 K. Using a least-squares technique, the data were fitted to a cp-polynomial, c
p
=k
0+k
1
T
−0.5+ k
2
T
−2+k
3
T
−3. In the temperature range 143 to 250 K, heat capacities of the different annite–siderophyllite members decrease linearly
with increasing Al content. At higher temperatures, however, the cp-polynomial of biotites with intermediate composition (except Ann79Sid21) exhibit a steeper slope than those of other biotites. This produces positive excess heat capacities in the annite–siderophyllite
join at higher temperatures. The activity-composition data of the same binary derived from phase equilibrium experiments (Benisek
et al. 1996) and the data of this study suggest two compositional regions along this join, with different extent of deviation
from ideality. One at X
Sid < 0.3, characterized by a small deviation, one at X
Sid > 0.3 showing a higher nonideality, resulting in a discontinuity visible at this composition. Powder IR-spectra of these
solid solutions were measured with a FTIR-spectrometer and used to calculate heat capacities according to the vibrational
model of Kieffer (1979). The comparison of the vibrational function with the cp-polynomials shows that the vibrational function reproduces well the DSC-data of the siderophyllite-poor and -rich members,
but deviates for intermediate compositions, where the excess heats of mixing occur. With increasing Tschermak vector, the
tetrahedral rotation angle α increases from 0 to 13° for annite to siderophyllite, respectively. At the composition of the
discontinuity, this rotation angle α reaches a value of ∼8∘. The processing of ∼300 chemical data of natural biotites indicates that over 90% of them have a tetrahedral rotation angle
that lies between 7 and 9°. It would appear that biotites with these structural characteristics are most stable.
Received: 27 August 1998 / Accepted: 10 November 1998 相似文献
70.
Eric P. Chassignet Hernan Arango David Dietrich Tal Ezer Michael Ghil Dale B. Haidvogel C. -C. Ma Avichal Mehra Afonso M. Paiva Ziv Sirkes 《Dynamics of Atmospheres and Oceans》2000,32(3-4)
The results of an intercomparison experiment performed with five numerical ocean models of different architecture are presented. While all models are able to simulate the large-scale characteristics of the North Atlantic circulation with a fair degree of realism, they also exhibit differences that can be attributed to the choices made in vertical coordinates, domain size, and boundary conditions. 相似文献