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31.
In recent years, biological toxicity tests have been conducted for soil assessment of environmental pollutants to evaluate the environmental risk due to heavy metals. In this study, batch tests were conducted with soils contaminated with hexavalent chromium (Cr6+) using sulfur-oxidizing bacteria (SOB). For control soils (without Cr6+), the electrical conductivity (EC) increased linearly over time in all samples, indicating that no toxic substances were present in the soil. The initial EC varied between 6 and 7.8 mS/cm, and the final EC varied between 22 and 27 mS/cm after incubation for 65 h. For batch tests performed using Cr6+-contaminated soil, the EC increased slightly or remained stable in all the test samples after a few hours. Thus, the presence of toxic substance Cr6+ inhibited the SOB, which leads to no sulfuric acid formation and therefore, no change in EC. These results indicated that SOB can be employed as a test microorganism to assess the quality of heavy metal-contaminated soils. 相似文献
32.
Numerous early Cretaceous mafic and alkaline dykes, mostly trending in N-S direction, are emplaced in the Archaean gneissic
complex of the Shillong plateau, northeastern India. These dykes are spatially associated with the N-S trending deep-seated
Nongchram fault and well exposed around the Swangkre-Rongmil region. The petrological and geochemical characteristics of mafic
dykes from this area are presented. These mafic dykes show very sharp contact with the host rocks and do not show any signature
of assimilation with them. Petrographically these mafic dykes vary from fine-grained basalt (samples from the dyke margin)
to medium-grained dolerite (samples from the middle of the dyke) having very similar chemical compositions, which may be classified
as basaltic-andesite/andesite. The geochemical characteristics of these mafic dykes suggest that these are genetically related
to each other and probably derived from the same parental magma. Although, the high-field strength element (+rare-earth elements)
compositions disallow the possibility of any crustal involvement in the genesis of these rocks, but Nb/La, La/Ta, and Ba/Ta
ratios, and similarities of geochemical characteristics of present samples with the Elan Bank basalts and Rajmahal (Group
II) mafic dyke samples, suggest minor contamination by assimilation with a small amount of upper crustal material. Chemistry,
particularly REE, hints at an alkaline basaltic nature of melt. Trace element modelling suggests that the melt responsible
for these mafic dykes had undergone extreme differentiation (∼ 50%) before its emplacement. The basaltic-andesite nature of
these rocks may be attributed to this differentiation. Chemistry of these rocks also indicates ∼ 10–15% melting of the mantle
source. The mafic dyke samples of the present investigation show very close geochemical similarities with the mafic rocks
derived from the Kerguelen mantle plume. Perhaps the Swangkre-Rongmil mafic dykes are also derived from the Kerguelen mantle
plume. 相似文献
33.
Journal of Seismology - The Koyna-Warna region in western India is well known around the globe for recurrent reservoir-triggered seismicity soon after the impoundment of the Koyna and Warna... 相似文献
34.
In this paper, we have considered a model for FRW space-time in the presence of coupled scalar field φ and potential V(φ) with causal viscous fluid and polytropic fluid. We have shown that irrespective of fluid the causality theory provides late
time acceleration of the universe. In all cases, the potential always decreases due to evolution of the universe. 相似文献
35.
36.
N. Bhandari J. T. Padia M. N. Rao P. N. Shukla K. M. Suthar R. Sarafin U. Herpers 《Meteoritics & planetary science》1988,23(2):103-106
Abstract— Cosmic ray produced tracks, He and Ne isotopes and radionuclides have been studied in the recently fallen H5 chondrite Gujargaon. The results indicate an exposure age of about 7 Ma. The high track production rates of 0.25 to 0.69 × 106 cm?2 Ma?1 suggest that the Gujargaon meteoroid had a small size (Re = 9–10 cm) in space and suffered 1–3 cm ablation in the atmosphere. The conclusion about the meteoroid size is supported by the low activity of neutron capture isotope 60Co and high spallogenic 22Ne/21Ne ratio of about 1.25. The data on long lived isotopes 10Be, 53Mn and 26Al are used to derive production rates of these isotopes in a rock having a radius of 9 cm and the activity levels of the short lived isotopes 22Na and 54Mn are used to estimate the effect of modulation of galactic cosmic rays at the time of solar maximum of 1982. 相似文献
37.
38.
The electric current exists because of the non-potential magnetic field in solar active regions. We present the evolution of net current in the solar active region NOAA 10930 as the sum of shear current and twist current by using 27 high-resolution vector magnetograms obtained with Hinode/SOT-SP during 9?–?15 December 2006. This active region was highly eruptive and produced a large number of flares ranging from B to X class. We derived local distribution of shear and twist current densities in this active region and studied the evolution of net shear current (NSC) and net twist current (NTC) in the N-polarity and S-polarity regions separately. We found the following: i) The twist current density was dominant in the umbrae. ii) The footpoint of the emerging flux rope showed a dominant twist current. iii) The shear current density and twist current density appeared in alternate bands around the umbrae. iv) On the scale of the active region, NTC was always larger than NSC. v) Both NTC and NSC decreased after the onset of an X3.4 class flare that occurred on 13 December 2006. 相似文献
39.
Topographic corrections of synthetic aperture radar (SAR) images over hilly regions are vital for retrieval of correct backscatter values associated with natural targets. The coarse resolution external digital elevation models (DEM) available for topographic corrections of high resolution SAR images often result into degradation of spatial resolution or improper estimation of backscatter values in SAR images. Also, many a times the external DEMs do not spatially co-register well with the SAR data. The present study showcases the methodology and results of topographic correction of ALOS-PALSAR image using high resolution DEM generated from the same data. High resolution DEMs of Jaipur region, India were generated using multiple pair SAR images acquired from ALOS-PALSAR using interferometric (InSAR) techniques. The DEMs were validated using differential global positioning system measured elevation values as ground control points and were compared with photogrammetric DEM (advanced spaceborne thermal emission and reflection radiometer – ASTER) and SRTM (Shuttle Radar Topography Mission) DEM. It was observed that ALOS-PALSAR images with optimum baseline parameters produced high resolution DEM with better height accuracy. Finally, the validated DEM was used for topographic correction of ALOS-PALSAR images of the same region and were found to produce better result as compared with ASTER and SRTM-DEM. 相似文献
40.
Natural Hazards - High wind poses a number of hazards in different areas such as structural safety, aviation, and wind energy—where low wind speed is also a concern, pollutant transport, to... 相似文献