全文获取类型
收费全文 | 166篇 |
免费 | 1篇 |
国内免费 | 1篇 |
专业分类
测绘学 | 3篇 |
大气科学 | 3篇 |
地球物理 | 27篇 |
地质学 | 99篇 |
海洋学 | 9篇 |
天文学 | 11篇 |
自然地理 | 16篇 |
出版年
2022年 | 1篇 |
2021年 | 2篇 |
2020年 | 3篇 |
2019年 | 1篇 |
2018年 | 9篇 |
2017年 | 5篇 |
2016年 | 6篇 |
2015年 | 4篇 |
2014年 | 3篇 |
2013年 | 8篇 |
2012年 | 8篇 |
2011年 | 3篇 |
2010年 | 5篇 |
2009年 | 5篇 |
2008年 | 2篇 |
2007年 | 4篇 |
2006年 | 1篇 |
2005年 | 4篇 |
2004年 | 2篇 |
2003年 | 3篇 |
2002年 | 2篇 |
2001年 | 2篇 |
2000年 | 3篇 |
1999年 | 9篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1983年 | 5篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 7篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1975年 | 6篇 |
1974年 | 4篇 |
1973年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有168条查询结果,搜索用时 286 毫秒
151.
Stagnation points and bifurcation in 3-D mountain airflow 总被引:1,自引:0,他引:1
152.
153.
Four natural peridotite nodules ranging from chemically depletedto Fe-rich, alkaline and calcic (SiO2 = 43.745.7 wt.per cent, A12O3 = 1.6O8.21 wt. per cent, CaO = 0.708.12wt. per cent, alk = 0.100.90 wt. per cent and Mg/(Mg+Fe2+)= 0.940.85) have been investigated in the hypersolidusregion from 800? to 1250?C with variable activities of H2O,CO2, and H2. The vapor-saturated peridotite solidi are 50200?Cbelow those previously published. The temperature of the beginningof melting of peridotite decreases markedly with decreasingMg/(Mg+SFe) of the starting material at constant CaO/Al2O3.Conversely, lowering CaO/Al2O3 reduces the temperature at constantMg/(Mg+Fe) of the starting material. Temperature differencesbetween the solidi up to 200?C are observed. All solidi displaya temperature minimum reflecting the appearance of garnet. Thisminimum shifts to lower pressure with decreasing Mg/(Mg + Fe)of the starting material. The temperature of the beginning ofmelting decreases isobarically as approximately a linear functionof the mol fraction of H2O in the vapor (XH2Ov). The data alsoshow that some CO2 may dissolve in silicate melts formed bypartial melting of peridotite. Amphibole (pargasitic hornblende) is a hypersolidus mineralin all compositions, although its P/T stability field dependson bulk rock chemistry. The upper pressure stability of amphiboleis marked by the appearance of garnet. The vapor-saturated (H2O) liquidus curve for one peridotiteis between 1250? and 1300?C between 10 and 30 kb. Olivine, spinel,and orthopyroxene are either liquidus phases or co-exist immediatelybelow the temperature of the peridotite liquidus. The data suggest considerable mineralogical heterogeneity inthe oceanic upper mantle because the oceanic geotherm passesthrough the P/T band covering the appearance of garnet in variousperidotites. The variable depth to the low-velocity zone is explained byvariable aHjo conditions in the upper mantle and possibly alsoby variations in the composition of the peridotite itself. Itis suggested that komatiite in Precambrian terrane could formby direct melting of hydrous peridotite. Such melting requiresabout 1250?C compared with 1600?C which is required for drymelting. The genesis of kimberlite can be related to partial meltingof peridotite under conditions of XH2Ov = 0.50.25 (XCO2v= 0.50.75). Such activities of H2O result in meltingat depths ranging between 125 and 175 km in the mantle. Thisrange is within the minimum depth generally accepted for theformation of kimberlite. 相似文献
154.
The deglaciation of Norway after 10,000 B.P. 总被引:1,自引:0,他引:1
Several distinctive marginal moraines of Preboreal age have been observed in Norway. They are grouped into three major morainal zones that are radiocarbon dated at about 9900±100, 9600±100 and 9300±100 B.P. respectively. The following deglaciation of central Norway was rapid and most likely completed about 8500 B.P. Evidence of glacier fluctuations up to recent time is discussed. The results are based partly on observations by the field parties of the I.G.C.P. project 'Quaternary Glaciations in the Northern Hemisphere'. 相似文献
155.
Salt exposures and weathering residuum on several salt diapirs in different geographic/climatic settings were studied. Anhydrite,
gypsum, hematite, calcite, dolomite, quartz, and clay minerals are the main constituents of the weathering residuum covering
the salt diapirs in various thicknesses. Erosion rates of residuum as well as of rock salt exposures were measured at selected
sites for a period of 5 years by plastic pegs as benchmarks. Recorded data were standardized to a horizontal surface and to
long-term mean precipitation. For the rock salt exposures the following long-term denudation rates were determined of 30–40 mm a−1 for coastal diapirs and up to 120 mm a−1 for mountain salt diapirs. Long-term mean superficial denudation rate measured on weathering residuum of low thickness reached
3.5 mm a−1 on coastal diapirs. The total denudation rate estimated for the thin residuum is close to 4–7 mm a−1 based on apparent correlation with the uplift rate on Hormoz and Namakdan diapirs. Denudation of rock salt exposures is much
faster compared to parts of diapirs covered by weathering residuum. The extent of salt exposures is an important factor in
the morphological evolution of salt diapirs as it can inhibit further expansion of the diapir. Salt exposures produce huge
amounts of dissolved and clastic load, thus affecting the surrounding of the diapir. 相似文献
156.
Zare MR Mostajaboddavati M Kamali M Abdi MR Mortazavi MS 《Marine pollution bulletin》2012,64(9):1956-1961
The natural radioactivity levels in sediment samples of the northern coast of Oman Sea, covering the coastal strip from Hormoz canyon to Goatr seaport, as the first time has been determined. The results of measurements will serve as background reference level for Oman Sea coastlines. Sediments from 36 coastal and near shore locations were collected for analysis. Analysis on the collected samples were carried out to determine (235)U, (238)U, (232)Th, (40)K and (137)Cs using two high purity germanium detectors with 38.5% and 55% relative efficiencies. The concentration of (235)U, (238)U, (232)Th, (40)K and (137)Cs in sediment samples ranged between 1.01 and 2.87Bq/kg, 11.83 and 22.68Bq/kg, 10.7 and 25.02Bq/kg, 222.89 and 535.07Bq/kg and 0.14 and 2.8Bq/kg, respectively. The radium equivalent activity was well below the defined limit of 370Bq/kg. The external hazard indices were found to be less than 1, indicating a low dose. 相似文献
157.
158.
Thermoregulatory effects which occur during the first hours after plumage-oiling were studied under laboratory conditions by measuring the metabolic heat production of Common Eiders ( Somateria mollissima ) which were resting in water for up to three hours. The ducks were exposed to 10-70 mL Statfjord A crude oil while residing in water inside a respiration chamber at 5.5°C. The study demonstrated a dose-and time-dependent effect of plumage oiling on metabolic heat production during the first three hours after contact with the oil. The results indicate that the immediate, short-term effects following initial contact with oil at sea are lesser in scale than those which occur after the birds have preened the oil into a greater part of their plumage. After plumage contamination with 70 mL crude oil, the rate of heat loss exceeded the thermoregulatory heat production capacity and the Eiders became hypothermic within 70 minutes after contamination. 相似文献
159.
160.
KEVIN J. TUTTLE SVElN ROAR ØOUSTMO BJ ÖRN G. ANDERSEN 《Boreas: An International Journal of Quaternary Research》1997,26(2):141-156
This raised delta structure is an ice-contact deltaic complex with a volume of c. 4.4.109 m3 , deposited c . 9500 yr BP in a shallow wide 'fjord' during the retreat of the Scandinavian ice cap. The delta plain lies at an altitude of 200–223 m. It aggraded c . 20 m above the contemporaneous sea level during a regional marine regression. The braidplain palaeochannel characteristics indicate a peak meltwater discharge of 7–9 103 m3 /s. Calculations based on a glacial ablation model indicate a mid-summer discharge of c . 5.5 103 m3 /s. However, the fluvial topset of the delta has an erosive base whose altitude decreases upstream and indicates stream incision by more the 6 m below the contemporaneous sea level. The deep scour is ascribed to episodic floods over the relatively short delta plain, which exceeded direct ablation-associated discharges. The depositional time-span of the delta is assessed to have been 70 years, calculated from coastal gradient and shoreline displacement curves. The average sedimentation rate of the delta is thereby inferred to have been extremely high, c . 6. 107 m3 /yr. The sedimentation is thought to reflect 'extreme' ice-margin conditions, where the sediment and water discharge was maximized by full-scale ablation, with simultaneous subglacial, englacial and supraglacial sediment and water supply. These conditions might further coincide with an abundant rainfall in the catchment area or the drainage of dammed waters, initiating episodic floods which eroded deep beneath sea level. As a whole, the study illustrates the hydrological conditions of proglacial sedimentation at the front of the rapidly retreating last Scandinavian ice cap. 相似文献