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91.
B. Trček 《Environmental Geology》2008,55(2):269-276
The role of the unsaturated zone in the karst aquifer hydraulic behaviour was brought into focus in these studies of the catchment
of the Hubelj spring (SW Slovenia). The variations of natural tracers in precipitation and in groundwater during a summer
storm event made it possible to trace local flow and solute transport in the observed aquifer. The results produced data on
the aquifer recharge, storage and discharge processes, as well as on mechanisms that affected them, which reflects a karst
groundwater dynamics also at a regional scale. They point out the significance of effects of the fast preferential flow—epiflow
that is the main factor controlling solute/contaminant transport towards the aquifer saturated zone. Numerous arguments indicate
that the karst aquifer flow and solute transport mechanisms depend on the hydraulic behaviour of the epikarst zone. 相似文献
92.
Modelling the influence of environmental and weather factors on the density of the invasive polychaete Boccardia proboscidea
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Griselda V. Garaffo María L. Jaubet María A. Sánchez Elizabeth N. Llanos Eduardo A. Vallarino Rodolfo Elías 《Marine Ecology》2016,37(6):1256-1265
The inter‐tidal zone around sewage discharges in a Southwest Atlantic shore (Mar del Plata, Argentina) is currently colonized by extensive inter‐tidal reefs of the invasive spionid Boccardia proboscidea. Understanding the links between both human and natural disturbances and the massive development of non‐indigenous species will help prevent marine bioinvasions, which are already favoured by global oceanic trade. We present herein predictive models for variations in the density of B. proboscidea around sewage discharges of Mar del Plata, using environmental (pH, turbidity, temperature, salinity and total organic matter content), weather (wind direction and storm records), spatial (sites) and temporal (season and year) variables. Density variations were modelled by generalized linear models, and model averaging (multimodel inference) was used to obtain predicted values. The highest predicted values of B. proboscidea density occurred at sites to the south of the sewage effluent in spring. These sites are more affected by urban effluent discharges and they showed increased B. proboscidea density when the north wind was predominant. In addition, B. proboscidea density values were higher in sites with 20–22 °C (seawater temperature), high total organic matter content in sediments and low salinity. The averaged model was only a good ‘predictive model’ for sites to the north of the outfall, but was useful as an ‘explanatory model’ in all sites. Such predictions may help to back up conservation and management policies and decisions. 相似文献
93.
The corundum‐rich metabauxites, found at the northwest limb of an NE–SW‐trending isoclinal recumbent fold at Mt. Ismail, are enclosed in thick‐bedded platform‐type marbles of Late Cretaceous age, surrounding the polymetamorphic core series in the southern part of the Menderes Massif (SW Turkey). The metabauxite horizons observed as typically boudine‐like structure, extend laterally over c. 3 km and are 1 to 5 m thick. These rocks have dominant mineral assemblages of corundum (~50 modal %), chloritoid (~30 modal %), white mica (margarite, muscovite), diaspore, Fe–Ti‐Oxides (ilmenite, ilmenohematite, rutile), and goethite, limonite, pyrite, tourmaline (uvite, schorl) as minor phases. Chemical analyses of whole rock samples and the mineral assemblage indicate that coexisting minerals of metabauxites are highly aluminous. A number of minerals (e.g. chloritoid and margarite) display a large compositional variation reflecting the initial chemical inhomogenetiy of the karstbauxites. The field observations, trace‐element accumulation coefficients, concentration of elements such as Cr, Zr, Ga and Ni and low amounts of immobile elements all suggest that the studied corundum‐rich metabauxites can be classified as karstbauxites, and are more likely to be a product of weathering of intermediate igneous or argillaceous parental rocks, similar to the karstic Tauric bauxites in the Central Taurides (Seydi ?ehir region) and probably are similar in age (Cenomanian–Turonian). In respect of tectono‐metamorphic evolution, the studied corundum‐rich metabauxites were regionally metamorphosed at ~5–6 kbar pressure and 500–600°C as a consequence of the Barrovian metamorphism referred to as the ‘Main Menderes Metamorphism’ related to the ophiolitic obduction onto the Menderes platform from the Izmir–Ankara Suture during the Middle Eocene. 相似文献
94.
Provenance of Cored Sediments from Active Margin off Southwestern Taiwan Deduced from Geochemical Constraints 总被引:1,自引:0,他引:1
HUANG Shaowei CHEN Juchin LO Chienying LEE Yungtan JIANG Weiteh WANG Yunshuen CHUNG Sanhsiung 《《地质学报》英文版》2014,88(1):128-141
The cored sediments sampled by R/V Marion Dufrense in the active margin off southwestern Taiwan on the east side of the Manila Trench are mostly muds consisting mainly of quartz, feldspar, illite, chlorite + kaolinite with a trace amount of montmorillonite. The cored sediments have higher Fe, Ti, Cr, Cs, Li, Ni, and V but lower Ca, Na, Mn, Hf, Nb, Sr, Ta, U and Zr contents when compared with the upper continental crust(UCC, Taylor and McLennan, 1985). The Eu/Eu* ratios of the sediments averaging 0.69 indicate that the recycling effect on the Eu anomaly may be minor and the contribution of mafic source rock was unimportant, which can also be depicted in the La-Th-Sc plot(Cullers, 1994) showing a "mixed origin" close to the felsic end member. The chemistry of the cored sediment can be explained by a mixing model designed by Ho and Chen(1996) with four end members i.e., greywacke, shale, quartzite and limestone, which are widely distributed in the Cenozoic formations of southern Taiwan with greywacke as the dominant contributor followed by shale. 相似文献
95.
扬子地块的西南边缘活动带,在印支板块、欧亚板块多次碰撞下,导致其不断被破裂、挤压、拉伸,并伴随强烈的岩浆活动及成矿作用.独特的成矿环境,表现为多期性、继承性和分带性成矿特征,因此区内尚有较大的找矿潜力. 相似文献
96.
In order to identify the mud diapirs and mud volcanoes off SW Taiwan, we have examined ∼1500 km long MCS profiles and related marine geophysical data. Our results show ten quasi-linear mud diapirs, oriented NNE–SSW to N–S directions. Thirteen mud volcanoes are identified from the multibeam bathymetric data. These mud volcanoes generally occur on tops of the diapiric structures. Moreover, the active mud flow tracks out of mud volcanoes MV1, MV3 and MV6 are observed through the high backscatter intensity stripes on the sidescan sonar images. The heights of the cone-shaped mud volcanoes range from 65 m to 345 m, and the diameters at base from 680 m to 4100 m. These mud volcanoes have abrupt slopes between 5.3° and 13.6°, implying the mudflow is active and highly viscous. In contrast, the flat crests of mud volcanoes are due to relative lower-viscosity flows. The larger cone-shaped mud volcanoes located at deeper water depths could be related to a longer eruption history. The formation of mud diapirs and volcanoes in the study area are ascribed to the overpressure in sedimentary layers, compressional tectonic forces and gas-bearing fluids. Especially, the gas-bearing fluid plays an important role in enhancing the intrusion after the diapirism as a large amount of gas expulsions is observed. The morphology of the upper Kaoping Slope is mainly controlled by mud diapiric intrusions. 相似文献
97.
Isotopic and cladoceran investigations of Eemian (MIS 5e) lake sediments from Imbramowice, SW Poland, allow us to reconstruct the environmental conditions, especially changes of water level and trophic status, during the early and middle Eemian Interglaciation. We analyzed the sediments from 6.5 to 11.0 m depth in a core provided by Mamakowa (1989). The upper 6.5 m had insufficient carbonates and cladoceran contents for analyses. The analyzed section consists of sandy and organic silts at the bottom, followed by gyttja characterized by increasing CaCO3 content. Measured δ18O values oscillate from ca. - 9 to - 4‰ and δ13C from - 3.5 to above + 6‰. Based on stable isotope analyses of carbonates, we define and characterize eight isotopic horizons (Is). We identify 26 taxa of subfossil Cladocera and seven zones (CLZ) of faunal development. Probably the greatest depth of the lake occurred with pollen zone E2; shallowing then took place. During pollen zones E2-E3, gradual warming is observed and expressed through a positive trend in both δ18O and δ13C values. Pollen zone E4 is characterized by frequent changes of water level. During the Eemian Interglaciation, excluding the initial phase of lake evolution, the lake was meso-eutrophic and eutrophic with high phytoplankton productivity. 相似文献
98.
Siby Kurian Rajesh Agnihotri D. V. Borole S. Wajih A. Naqvi Ana M. Ferreira Carlos Vale 《第四纪科学杂志》2009,24(2):109-116
Using multiple geochemical proxies including specific biomarkers (dinosterol, phytol, stigmasterol and β‐sitosterol) measured in a high‐sedimentation rate core collected from the inner shelf (depth ~45 m) off Goa (India), we reconstruct surface productivity, which is mainly controlled by the monsoon upwelling in this region, during the last ca. 700 a. Surface productivity appears to have varied in tandem with the Konkan–Goa rainfall and sunspot activity during the instrumental period (last 250 a). The productivity proxies also covary with the total solar irradiance reconstructed for the period beyond the instrumental era, within the considerable uncertainty of the age model. This suggests that solar forcing may control coastal upwelling intensity and biological productivity in the eastern Arabian Sea on decadal to centennial timescales. During the late Anthropocene (last ca. 50 a), steep increases in all four biomarkers indicate greatly enhanced productivity in response to high solar irradiance as well as anthropogenic inputs of nutrients. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
99.
火山"熔岩流气泡古高度计"及其在云南腾冲火山区的应用 总被引:6,自引:5,他引:1
通过对火山熔岩流及其气泡特征的研究能够确定熔岩流喷发时的古高度,本文将这一方法称为火山“熔岩流气泡古高度计”.“熔岩流气泡古高度计”是在实地测量熔岩流厚度和实验室对熔岩流顶底气泡体积精确测定的基础上,利用流体力学原理和气体状态方程,通过计算古大气压强,最终获得火山喷发时的古高度.由于火山岩是开展同位素测年的理想材料,并且利用熔岩流计算古高度所需的参数(熔岩流厚度和气泡体积)不受古气候等因素(温度、降雨量等)影响,因此,这一方法以其可靠的年龄和独立的计算参数明显区别于其它古高度计.“熔岩流气泡古高度计”核心技术包括:(1)熔岩流的挑选与厚度测量;(2)熔岩流底部和顶部气泡体积的计算.中等规模、具简单冷凝历史,并且厚度稳定的偏基性熔岩流,是开展古高度计算的理想对象.熔岩流气泡体积的测试手段包括注胶、岩石抛光-扫描、体视学转换和三维CT扫描4种方法.“熔岩流气泡古高度计”最终计算结果误差为400m左右.本文利用“熔岩流气泡古高度计”计算了腾冲火山区熔岩流的古高度,研究结果显示:“熔岩流气泡古高度计”计算的黑空山熔岩流高程与目前的实际高程相吻合.开展“熔岩流气泡古高度计”研究的前提是研究区必须出露保存完好的熔岩流.我国青藏高原的隆升历史一直是国际学术界争论的热点课题,那里出露大面积熔岩流.可以预见,“熔岩流气泡古高度计”将会逐渐成为研究青藏高原隆升历史的有效手段之一. 相似文献
100.