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71.
K.A. Evans H.St.C. O’Neill N.S. Keller L.-Y. Jang 《Geochimica et cosmochimica acta》2009,73(22):6847-7631
S K-edge XANES and Mn-, W- and Ni-XANES and EXAFS spectra of silicate glasses synthesised at 1400 °C and 1 bar with compositions in the CaO-MgO-Al2O3-SiO2-S plus MnO, NiO, or WO3 systems were used to investigate sulphur speciation in silicate glasses.S K-edge spectra comprised a composite peak with an edge between 2470 and 2471.4 eV, which was attributed to S2−, and a peak of variable height with an edge at 2480.2-2480.8 eV, which is consistent with the presence of S6+. The latter peak was attributed to sample oxidation during sample storage. W-rich samples produced an additional lower energy peak at 2469.8 eV that is tentatively attributed to the existence of S 3p orbitals hybridised with the W 5d states.Deconvolution of the composite peak reveals that the composite peak for Mn-bearing samples fits well to a model that combines three Lorentzians at 2473.1, 2474.9 and 2476.2 eV with an arctan edge step. The composite peak for W-bearing samples fits well to the same combination plus an additional Lorentzian at 2469.8 eV. The ratio of the proportions of the signal accounted for by peaks at 2473.1 and 2476.2 eV correlates with Mn:Ca molar ratios, but not with W:Ca ratios. Spectra from Ni-bearing samples were qualitatively similar but S levels were too low to allow robust quantification of peak components. Some part of the signal accounted for by the 2473.1 eV peak was therefore taken to record the formation of Mn-S melt species, while the 2469.8 peak is interpreted to record the formation of W-S melt species. The 2474.9 and 2476.2 eV peaks were taken to be dominated by Ca-S and Mg-S interactions. However, a 1:1 relationship between peak components and specific energy transitions is not proposed. This interpretation is consistent with known features of the lower parts of the conduction band in monosulphide minerals and indicates a similarity between sulphur species in the melts and the monosulphides. S-XANES spectra cannot be reproduced by a combination of the spectra of the component element monosulphides.Mn-, W- and Ni-XANES and EXAFS for synthetic glasses without sulphide exsolution did not show any sensitivity to the presence of sulphur, which is unsurprising as S:O ratios were sufficiently low that metals would be mostly co-ordinated by O. Mn EXAFS spectra were consistent with divalent Mn in 5 co-ordinated Mn-O melt species. W spectra were consistent with tetrahedrally co-ordinated hexavalent W, most likely in scheelite-like melt species, and Ni spectra were consistent with [4] co-ordinated divalent Ni. These results indicate lower co-ordinations for both W and Ni than those inferred by some previous workers. Cation co-ordination may reflect the proportion of non-bridging oxygens, which is lower in the Ca-rich and Al-poor samples investigated here than for previous studies. 相似文献
72.
Ju-Duk Yoon Jeong-Hui Kim Sang-Hyeon Park Eve Kim Min-Ho Jang 《Ocean Science Journal》2017,52(1):147-164
The construction of an estuary barrage, an instream structure in the lower reaches of a river, causes significant physical changes in water flow patterns and river morphology, and results in altered environmental conditions. Here, we examined the impact of the Geum River estuary barrage, completed in 1990, on fish assemblages by using a literature search and fresh surveys of fishways in the barrage. We found that fish assemblages upstream and downstream of the barrage were altered following its completion. After construction, more species were found in the freshwater area, with a particularly great increase in freshwater species. Conversely, estuarine and marine species were only consistently caught in the downstream salt-water area, although the number of species increased. In total, 15,829 fish from 47 species and 20 families were identified at the three types (pool and weir, rubble type, and boat passage) of fishways in the barrage. The dominant species were Chelon haematocheilus, an estuarine species, Coilia nasus, a diadromous species, and Erythroculter erythropterus, a freshwater species. The mean total length of fish (101.9 ± 76.0 mm) in the boat passage fishway was approximately 100 mm lesser than those in the pool and weir (207.2 ± 112.8 mm) and rubble type (205.8 ± 112.7 mm) fishways. The boat passage fishway was the most efficient for fish movements. The current fishway system is not sufficient for fish migration, and thus additional ways are required to improve the system such as the boat passage. Few estuarine or diadromous species were found in both freshwater and salt-water areas, but freshwater fishes that accidently moved to salt-water area actively used fishways. Therefore, fishway management in the Geum River estuary barrage has to focus on freshwater fish; however, this may need to change to a focus on migratory fishes depending on ecological life cycles of migratory fish. 相似文献
73.
74.
75.
Lee Seok Oh Kyung-Hee Jang Sung-Tae You Hak Yoel Park Joonsung Song Kyu-Min 《Ocean Science Journal》2019,54(1):39-50
Ocean Science Journal - A practical method to estimate the M2 tidal current is proposed based on one-day current observations. In this method, the semi-diurnal constituent, composed of several... 相似文献
76.
R observations of a newly discovered binary GSC 4540_1533 are presented. Analysis of the light curve with the Wilson-Devinney
program indicates that the system is detached and consist of 2 main sequence stars.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
77.
Yuzo Obara Tomoharu Nakayama Katsuhiko Sugawara Toshiro Aoki Hyun Kuk Jang 《国际地质力学数值与分析法杂志》1992,16(10):701-716
A two-dimensional hybrid method for solving elastoplastic problems in engineering is presented by coupling two existing methods, namely, the boundary element method and the characteristics method. The formulation of this method is presented, as well as an excellent procedure for the determination of the boundary between elastic and plastic regions. It is shown not only that this method is a powerful and accurate method for evaluating the shape and extent of the plastic region around rock caverns, which is of prime importance for the construction of rock caverns, but also applicable to a given range of the initial stress field ratio where only compressive failure occurs. Then, some typical examples are solved in order to check the accuracy of the solution by this method. Furthermore, its successful applications are presented and discussed to determine the shape and the extent of the plastic regions around parallel, circular and rectangular openings. 相似文献
78.
Minhwan Jang 《Astrophysics and Space Science》2001,275(3):209-215
Preliminary results from a pilot program to monitor the intranightoptical variability in Seyfert 2 galaxies are reported. This program is designed to test some of the prominent theoretical mechanismsproposed for the origin of optical microvariability in active galacticnuclei (AGN). Two out of 3 Seyfert 2 galaxies observed show evidence formicrovariations. This detection can provide important constraints forthe models utilizing discrete events on accretion disks. 相似文献
79.
Climate change due to global warming is a public concern in Central Asia. Because of specific orography and climate conditions, the republic of Tajikistan is considered as the main glacial center of Central Asia. In this study, regional climate change impacts in the two large basins of Tajikistan, Pyanj and Vaksh River basins located in the upstream sector of the Amu Darya River basin are analysed. A statistical regression method with model output statistics corrections using the ground observation data, Willmott archived dataset and GSMaP satellite driven dataset, was developed and applied to the basins to downscale the Global Climate Model Projections at a 0.1‐degree grid and to assess the regional climate change impacts at subbasin scale. It was found that snow and glacier melting are of fundamental importance for the state of the future water resources and flooding at the target basins since the air temperature had a clearly increasing trend toward the future. It was also found that the snowfall will decrease, but the rainfall will increase because of the gradual increase in the air temperature. Such changes may result in an increase in flash floods during the winter and the early spring, and in significant changes in the hydrological regime during a year in the future. Furthermore, the risks of floods in the target basins may be slightly increasing because of the increase in the frequencies and magnitudes of high daily precipitation and the increase in the rapid snowmelt with high air temperatures toward the future. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
80.
Deterministic flood inundation mapping is valuable for the investigation of detailed flood depth and extent. However, when these data are used for real‐time flood warning, uncertainty arises while encountering the difficulties of timely response, message interpretation and performance evaluation that makes statistical analysis necessary. By incorporating deterministic flood inundation map outputs statistically by means of logistic regression, this paper presents a probabilistic real‐time flood warning model determining region‐based flood probability directly from rainfall, being efficient in computation, clear in message, and valid in physical meaning. The calibration and validation of the probabilistic model show a satisfactory overall correctness rate, with the hit rate far surpassing the false alarm rate in issuing flood warning for historical events. Further analyses show that the probabilistic model is effective in evaluating the level of uncertainty lying within flood warning which can be reduced by several techniques proposed in order to improve warning performance. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献