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51.
Records of palaeo‐sea level and eruption duration in a coastal tuff ring,Jeju Island,Korea 下载免费PDF全文
Phreatomagmatic volcanoes and their sedimentary products can preserve high‐resolution records of earth surface processes because of their high deposition rate. Songaksan, Jeju Island, Korea, is a phreatomagmatic volcano, which erupted c. 3.7 ka BP in a coastal setting. Its tuff ring preserves a record of intertidal to supratidal facies transition in the basal part, which reveals the position of palaeo‐high‐tide level for at least 13 high‐tide events, and a record of a storm‐surge event in the middle part of the tuff ring, which lasted approximately three tidal cycles. Based on these features, the phreatomagmatic eruption of Songaksan is estimated to have taken place over a month. The sea level at the time was almost identical to that at present. This study shows that coastal phreatomagmatic volcanoes can preserve high‐resolution records of eruption duration and palaeo‐sea level, and can provide accurately levelled and dated data points to the Quaternary sea‐level curve. 相似文献
52.
A geochemical study was carried out in a small spa area (Onyang Spa, Korea) where intensive pumping of deep thermal groundwater (1 300 000 m3 year−1) is taking place. This has caused the deep fractures to lose their artesian pressure and the upper shallow fractures have been encroached by shallow, cold waters. To quantify the influence of long‐term heavy pumping on the quality of the geothermal water, groundwater sampling and chemical analysis, water‐level measurement, and well loggings were performed for the selected deep thermal wells and shallow cold wells. Chemical analysis results indicate a big contrast in water chemistry and origins between the two water types. Shallow groundwater shows a wider concentration ranges in solutes that are closely related to human activity, illustrating the water's vulnerability to contamination near the land surface. Plots of water chemistry as a function of fluoride reveal that the quality of the thermal water was greatly influenced by the shallow, cold groundwater and that intensive pumping of the deep thermal groundwater has caused the introduction of shallow groundwater into the deeper fractures. Although the deep and the shallow fractures were piezometrically separated to some extent, a mixing model based on fluoride and nitrate indicated that the cold‐water fractions in the thermal wells are up to 50%. This suggests that the thermal water is faced with water quality degradation by the downward flow of the shallow, cold water. Restriction on the total of all the pumpage permits per unit area is suggested to restore the artesian pressure of the deep thermal aquifer and to prevent cold‐water intrusion in the study area. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
53.
Jae Woo Lee Chun-Hwey Kim Robert H. Koch 《Monthly notices of the Royal Astronomical Society》2007,379(4):1665-1680
We obtained CCD photometric observations of the Algol-type semidetached binary XX Cephei (XX Cep) during 15 nights from 2002 September 17 to 2003 February 2, and also on 2005 January 21. Except for those data taken on the last night of the concentrated observing season, the 3881 measurements were obtained over an interval of only 106 nights. From these data, four new times of minimum light were calculated. The (O− C) diagram formed from all available timings, and thus the orbital period of the system, can be partly represented as a beat effect between two cyclical variations with different periods ( yr, yr) and amplitudes ( K 1 =0.015 d, K 2 =0.103 d) , respectively. Both physical and non-physical interpretations of these cycles were investigated. The long-term sinusoidal variation is too long for magnetic cycling in solar-type single and close binary stars. In addition, we have studied the effect of a possible secular period variation. By analysing the residuals from our Wilson–Devinney (WD) binary model, we found small light variations with a period of 5.99 d with amplitudes growing toward longer wavelengths. We think that these oscillations may be produced by instabilities at the systemic L 1 point (also occupied by the point of the cool star) and that these instabilities are, in turn, caused by non-uniform and sporadic convection. There is also a short-period oscillation of about 45 min in the WD light residuals that is attributed to accretion on to the mass-gaining primary component from a feeble gas stream originating on the cool donor star. 相似文献
54.
To supplement conventional geophysical log data, this study presents temporal variations in electrical conductivity (EC) and temperature with depth in a multilayered coastal aquifer, on the eastern part of Jeju Island, Korea. One‐month time‐series data obtained at eight points from a multi‐depth monitoring system showed that semidiurnal and semimonthly tidal variations induced dynamic fluctuations in EC and temperature. At some depths, EC ranged from 1483 to 26 822 µS cm?1, while some points showed no significant variations. The results of EC log and time‐series data revealed that a sharp fresh‐saltwater interface occurred at low tide, but the diffusion zone broadened to 20 m at high tide. EC, temperature, and tide level data were used for the cross‐correlation analysis. The response time of EC and temperature to tide appears to range from less than 30 min to 11 h. Using end‐member mixing analysis (EMMA), the fraction of variations of chloride concentration in the multilayered aquifer was explained, and a conceptual model was developed which subdivided the coastal aquifer into four vertical zones. The percentage of water derived from seawater varied from 2 to 48 at specific depth, owing to tidal fluctuations. Continuous observations of EC and temperature at multiple depths are powerful tools for quantifying the transport of saline water by tidal variations in multilayered coastal aquifers. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
55.
56.
Hyoung-Gi Kim Chang-Yeoul Choi Jung-Wouk Woo Yongrok Choi Kyonghwan Kim Desheng Dash Wu 《Stochastic Environmental Research and Risk Assessment (SERRA)》2011,25(3):305-322
The Kyoto Protocol calls for industrialized nations to cut greenhouse gas emissions by 5% from 1990 levels by 2008–2012, so
developed countries are presenting various policies to reduce greenhouse gas that is produced in transport fields. One of
those polices is a modal shift that changes from road freight to sea, inland waterways and railroad transportation that is
eco-friendly. The increase of road freight brings road congestion, accidents, logistic costs, air pollution and greenhouse
gases. Railroads are superior to the other modes of transportation in mass transportability, high speed, timeliness, safety
and environmental-friendliness, but the railway industry has been pushed behind in competition. Korean railroads were used
by passengers and for freight transport popularly until the middle of the 20th century. However, because of the sudden change
of logistics environments, having time efficiency being most important, railroads lost logistic competitive power against
the transportation by truck. This paper intends to examine the modal shift to railroad transportation, which enjoys high interest
as environmentally-friendly logistics, i.e., the modal shift strategy. Efficiency analysis is conducted using DEA and exploratory
factors are identified for the modal shift of the companies. This paper also proposes an alternative plan for green logistics
and environmentally-friendly logistics, by analyzing the characteristics of the railroad cargo transportation system and the
conditions of local railroad cargo transportation. 相似文献
57.
Sang Woo Ji Young Wook Cheong Gil Jae Yim Jayanta Bhattacharya 《Environmental Geology》2007,52(6):1033-1043
Acid rock drainage (ARD) is a longstanding problem often associated with the resulting corrosion due to the acidity generated
from sulfidic oxidation. To evaluate characteristics of ARD and corrosion, samples from the road side rock mass of Boeun and
Mujoo were analysed using X-ray diffraction, acid/base accounting and Leaching tests. The results indicated that many samples
had a pyritic origin and can be regarded as acid-generating rocks. The Leaching test showed that the average pH of the leachates
of samples from both Boeun and Mujoo were moderately acidic, ranging from 3 to 4. Interestingly, as acidity increases from
pH 4, the SO4−, Fe, Al and Mg concentrations increase abnormally. Samples from roadside slope of Mujoo showed high corrosive potential.
Maximum sulfide oxidation rate of a sample taken from Mujoo was as high as 5,166 mg/kg/week. 相似文献
58.
Occurrence and distribution of vibrios in fishes and shellfishes in coastal waters of Hong Kong 总被引:1,自引:0,他引:1
Xu Huaishu Li Jun Phyllis Brayton Norman Y. S. Woo David Swartz Zhang Shuting Rita R. Colwell 《海洋学报(英文版)》1998,17(4):545-553
INTRODUCTIONTheoccurrenceanddistributionofhalophilicvibriosinthecoastalwatersofHongKonghasbeenrePorted(Chanetal.,l986).Theresultsshowedthatvibrioswerepresentduringthesum-mermonthsinHongKongcoastalwatersatconcentrationsof9oto67ooind./cm3,accountingo.4l%~4o%ofthetotalbacterialPOpulationofthe48isolatesexaminedindetail.Theyob-servedV.Paraheamolyticus,V.harvha,V.vulnfficus,V.camPbelliandV.fiuvialis.Becausemanyofthevibri0species,includingsome0ftheisolatesbyChanetal.(1986)fromHongKongwate… 相似文献
59.
60.
The Soufriere Hills volcano in the south-eastern part of Montserrat erupted pyroclast flows as recently as A. D. 1646 ± 54 years and must therefore be considered dormant, not extinct. The highly destructive nature of pyroclast flow eruptions makes it imperative that such activity should be predicted and, if the threat of eruption becomes sufficiently large, the population should be moved to a sale distance from the volcano. Sharp increases in seismic and solfataric activity occurred in 1966 and these events indicated the abnormally high risk of an eruption in the near future. A network of four short period seismographs was established in the island in May 1966 and between this date and the end of 1967, 723 local earthquakes were recorded, of which 32 were reported felt in the island. Hypocentres were determined for 189 of these earthquakes, and most of these lay in a WNW to ESE belt beneath the Soufriere Hills, at depths of less than 15 km. The average rate of seismic energy release decreased with time throughout the series but there was a strong seasonal variation with maxima in May and November–December of each year. The average depth of the earthquakes decreased from 5.2 km in April and May 1966 to a minimum of 2.8 km from July to September 1966. After September the mean focal depths increased again and by the end of the crisis in November 1967 the mean depth was 9.7 km. Measurements carried out using water-tube tiltmeters showed that the region 2–3 km south-east of the Soufriere Hills was doming upwards until January 1967, then subsided between January–March 1967 and finally rose again at a slower rate between March and September 1967. Heat flow from Galway’s Soufriere which was 3 × 105 cal/sec in 1954 increased to a maximum of 2 × 105 cal/sec in October 1966, then declined to 5 × 105 cal/sec in September 1967. The earthquake series was not the aftershock sequence of any major tectonic earthquake, and only two hypocentres were determined at depths greater than 15 km. It is concluded that magma was intruded into the upper crust beneath the Soufriere Hills volcano and that the earthquakes and other phenomena resulted from the upward migration of this magma. 相似文献