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排序方式: 共有319条查询结果,搜索用时 281 毫秒
131.
T.V. Donskaya D.P. Gladkochub V.S. Fedorovsky A.M. Mazukabzov M. Cho W. Cheong J. Kim 《Russian Geology and Geophysics》2013,54(10):1205-1218
We present geological, structural, and geochemical data on synmetamorphic granitoids from the Tutai and South Ol’khon plutons of the Ol’khon terrane (Central Asian Fold Belt) with an estimation of the U–Pb zircon age of the Tutai granites. The structural and petrological data suggest the synfolding and synmetamorphic origin of the granitoids. The U–Pb zircon age of the Tutai granites (488.6 ± 8.0 Ma) almost coincides with the previously estimated age of quartz syenites from the South Ol’khon pluton (495 ± 6 Ma). The plutons occupy the same position in the regional structure. The granitoids underwent final deformations and metamorphism at 464 ± 11 Ma. The Tutai pluton consists of moderately potassic granites, whereas the South Ol’khon pluton is made up of quartz syenites and granites. The geochemical characteristics of the granites from both plutons (low Y and Yb contents, fractionated REE patterns) indicate their formation under conditions of garnet crystallization in deep crustal restite. The higher Y and Yb contents of the South Ol’khon quartz syenites as compared with those of the granites suggest the lack of equilibrium between the quartz syenite magmas and garnet parageneses during their formation or evolution. The Tutai and South Ol’khon granites were derived from quartz-feldspar crustal rocks, whereas the South Ol’khon quartz syenites might have originated from a mixed (crust-mantle) source. It is presumed that the granitoids formed within accretion-thickened crust. Early accretion, which has been first identified in the region, affected not only the Pribrezhnaya zone (the zone of the Tutai and South Ol’khon plutons) but also the entire Anga–Satyurty megazone of the Ol’khon terrane. The accretion ended with the convergence and oblique collision of the Ol’khon terrane and Siberian continent, when strike-slip tectonics became ubiquitous. 相似文献
132.
Jae Seong Lee Eun-Soo Kim Sung-Hyun Kahng Seok-Hyun Yoon Jin-Hyung Cho Kyung-Soo Bahk Dong-Jin Kang 《Ocean Science Journal》2012,47(4):489-495
We have developed a novel miniature in situ microprofiler (NAFRI BelpI) for coastal and deep-sea studies. The BelpI can carry up to three oxygen microsensors, and it allows for simultaneous replicate measurements in a relatively small area. All functions can be controlled and programmed via a small magnetic bar and three reed switches; this feature facilitates the initial setup both onboard and underwater. The large LCD window shows basic information such as the movement intervals of the linear stage, number of replicate measurements, waiting time between measurements, and the pA from the microsensors. From high-resolution vertical profiles of oxygen in coastal sediment measured using the microsensors, the diffusivity boundary layer thicknesses was determined to be in the range 0.30–0.35 mm. In addition, the time-series measurement of oxygen profiles in permeable sandy sediment showed advective transport of oxygen into pore water by tidal agitation. Two examples of in situ measurement using a BelpI suggest that it can be widely applied to the study of the sediment-water interface. 相似文献
133.
Jaeil Cho Taikan Oki Pat J.-F. Yeh Wonsik Kim Shinjiro Kanae Kyoichi Otsuki 《Theoretical and Applied Climatology》2012,108(1-2):135-145
The sensitivity of land surface energy partitioning to near-surface air temperature (T a) is a critical issue to understand the interaction between land surface and climatic system. Thus, studies with in situ observed data compiled from various climates and ecosystems are required. The relations derived from such empirical analyses are useful for developing accurate estimation methods of energy partitioning. In this study, the effect of T a on land surface energy partitioning is evaluated by using flux measurement data compiled from a global network of eddy covariance tower sites (FLUXNET). According to the analysis of 25 FLUXNET sites (60 site-years) data, the Bowen ratio is found to have a linear relation with the bulk surface resistance normalized by aerodynamic and climatological resistance parameters in general, of which the slope and intercept are dependent on T a. Energy partitioning in warmer atmosphere is less sensitive to changes in land surface conditions. In addition, a negative relation is found between Bowen ratio and T a, and this relation is stronger above less vegetated surface and under low vapor pressure deficit and low received radiative energy condition. The empirical results obtained in this study are expected to be useful in gaining better understanding of alternating surface energy partitioning under increasing T a. 相似文献
134.
Influence of acid mine drainage on microbial communities in stream and groundwater samples at Guryong Mine,South Korea 总被引:1,自引:0,他引:1
Jaisoo Kim So-Yeon Koo Ji-Young Kim Eun-Hee Lee Sang-Don Lee Kyung-Seok Ko Dong-Chan Ko Kyung-Suk Cho 《Environmental Geology》2009,58(7):1567-1574
The effects of acid mine drainage (AMD) in a stream and groundwater near an abandoned copper mine were characterized by physicochemical
properties, bacterial community structure using denaturing gel gradient electrophoresis (DGGE), and microbial activity/diversity
using Ecoplate technique. Based on DGGE fingerprints, the eubacterial community structures grouped into the stream water (GRS1,
GRS2 and GRS3) and groundwater samples (GW1 and GW2), apparently based on differences in water temperature and the concentrations
of dissolved oxygen, nitrate and sulfate. The most highly AMD-contaminated sample (GRS1) had additional α-Proteobacteria whereas
the groundwater samples included additional β-Proteobacteria, suggesting the development of populations resistant to AMD toxicity
under aerobic and anaerobic conditions, respectively. Community level physiological activities on the 31 Ecoplate substrates
suggested that the activities decreased with increasing concentrations of sulfate and heavy metals derived from AMD. The Shannon
index showed that microbial diversity was greatest in GRS2, and lowest in GRS1, and was probably related to the level of AMD. 相似文献
135.
Slope stability analysis is a geotechnical engineering problem characterized by many sources of uncertainty. Some of these sources are connected to the uncertainties of soil properties involved in the analysis. In this paper, a numerical procedure for integrating a commercial finite difference method into a probabilistic analysis of slope stability is presented. Given that the limit state function cannot be expressed in an explicit form, an artificial neural network (ANN)-based response surface is adopted to approximate the limit state function, thereby reducing the number of stability analysis calculations. A trained ANN model is used to calculate the probability of failure through the first- and second-order reliability methods and a Monte Carlo simulation technique. Probabilistic stability assessments for a hypothetical two-layer slope as well as for the Cannon Dam in Missouri, USA are performed to verify the application potential of the proposed method. 相似文献
136.
Hyerin Kim Sung-Hyun Cho Dongguen Lee Youn-Young Jung Young-Hee Kim Dong-Chan Koh Jeonghoon Lee 《Environmental Earth Sciences》2017,76(2):82
For water resources management, many studies for investigating flow paths from rainfall to subsurface have been conducted for last half century. A hydrograph separation based on end member mixing was carried out to evaluate the importance of the hydrological pathways providing the main sources of a small granitic watershed, Dorim-cheon, Seoul. An analysis of chloride, oxygen-18 and deuterium isotopes from precipitation and stream water during three storms was conducted with high-resolution data using 129 samples. Stream water, collected in advance of rain event, was assumed as a pre-event water (baseflow) component according to its dry condition and isotopic values compared with the values of different time periods. The contribution from vadose water was ignored due to the thin soil layer covering the study area. Using a two-component mixing model, hydrograph separation of the stream water in Dorim-cheon was conducted based on weighted mean values of rain water and pre-event water component with the high-resolution datasets. As a result of the analysis with water isotopes, contribution of groundwater was dominant during the entire study period (73–74%) except of instant dominance of rainfall at the earliest period. Using chloride as a tracer for hydrograph separation, a significant difference for the amount of pre-event water contribution was identified. This might be caused by the large variation of chloride concentration during the rain event and the end member determination. 相似文献
137.
Dinoflagellate Cysts in Coastal Sediments as Indicators of Eutrophication: A Case of Gwangyang Bay,South Sea of Korea 总被引:1,自引:0,他引:1
Diatom densities in the surface water and dinoflagellate cysts in bottom sediments of Gwangyang Bay were studied to determine
changes in the phytoplankton community structure in response to anthropogenic eutrophication and to assess the use of dinoflagellate
cysts as indicators of coastal eutrophication. Our results show that, in nutrient-enriched environments, diatoms are particularly
benefited from the nutrients supplied and, as a consequence, heterotrophic dinoflagellates that feed on the diatoms can be
more abundant than autotrophic dinoflagellates. In short-core sediment records, a marked shift in autotrophic–heterotrophic
dinoflagellate cyst compositions occurred at a depth of approximately 9–10 cm corresponding to the timing of the 1970s industrialization
around Gwangyang Bay. This tentatively indicates that diatom and dinoflagellate communities here have undergone a considerable
change mainly due to increased nutrient loadings from both domestic sewage effluent and industrial pollution. Our study suggests
a possible potential use of dinoflagellate cysts in providing retrospective information on the long-term effects of coastal
eutrophication. 相似文献
138.
Seok Lee Heung-Jae Lie Kyu-Min Song Cheol-Ho Cho Eun-Pyo Lim 《Journal of Oceanography》2008,64(5):763-776
This study examined tidal modification and change in tidal currents caused by the construction of the Saemangeum dike, based
on field observations and a numerical model. The Saemangeum dike was completed in April 2006, enclosing an estuarine area
along the mid-western coast of South Korea. After closure of the dike, the tidal range outside the dike decreased slightly
but significantly, while the inside tidal range decreased drastically. The numerical model results show that the dike construction
has influenced tidal energy propagation and the tidal system in the Yellow Sea. The tidal current speed near the dike decreased
abruptly following closure of the dike, except in front of the sluice gates. Since completion of the dike, outflow water discharged
from the sluice gates has longer residence times due to the weakened tidal current; the change in the tidal current field
has also caused greater northward expansion of outflow water. The sluice gates release fresher water, which spreads over the
sea surface mainly by inertial momentum near the gate; this water is then gradually mixed with sea water farther from the
gate. The less saline, possibly more contaminated outflow impacts the marine environment near the Saemangeum dike. Controlling
the discharge and gate-opening timing can partially mitigate these impacts on the marine environment. 相似文献
139.
140.
A. Esquivel A. Lazarian S. Horibe J. Cho V. Ossenkopf J. Stutzki 《Monthly notices of the Royal Astronomical Society》2007,381(4):1733-1744
We continue with our previous work on statistics of velocity centroids, to retrieve information about the scaling properties of an underlying turbulent velocity field from spectroscopic observations. We use synthetic data sets with extreme effects of velocity–density correlations that we create artificially, which also have a non-Gaussian distribution of fluctuations. We confirm that centroids can be used to obtain the scaling properties of the turbulent velocity when the ratio of the density dispersion to the mean density is less than unity, regardless of velocity–density correlations and non-Gaussianity. It was found that extreme velocity–density correlations can distort the statistics of velocity centroids, impeding the recovery of the turbulent velocity spectral index from centroids. We show that such correlations introduce high-order moments to the maps of centroids, which we disregarded in previous work, but that they are only important when the density dispersion is large in comparison with the mean density. It was also found that non-Gaussian velocity and/or density distort the statistics of centroids too, but to a lower degree than extreme cross-correlations. 相似文献