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91.
92.
A period study of the young binary AR Aur based on the extensive series of published photoelectric/ccd minima times indicates the cyclic (O – C) variation for the system. This continuous oscillatory variation covers almost three cycles, about 6000 orbital periods, by the present observational data. It can be attributed to the light‐time effect due to a third body with a period of 23.68 ± 0.17 years in the system. The analysis yields a light‐time semi‐amplitude of 0.0084 ± 0.0002 day and an orbital eccentricity of 0.20 ± 0.04. Adopting the total mass of AR Aur, the mass of the third body assumed in the co‐planar orbit with the binary is M3 = 0.54 ± 0.03 M⊙ and the semimajor axis of its orbit is a3 = 13.0 + 0.2 AU. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
93.
Studies on differentiation of ensimatic arc units from melange units in the Northern Anatolian Ophiolitic Belt(NAOB) are very rare. The study area represents the southern edge of the central part of the NAOB.The aim of the study is to distinguish the main units of NAOB and to define the geotectonic setting of the Darmik Ensimatic Arc Association(DEAA). To study the ensimatic arc units as an independent tectonic unit is important and facilitates understanding of the geological evolution of the NAOB. During field studies, the contact relationships within the Darmik Ensimatic Arc Association(DEAA) units and also with other tectonic units were reviewed. Then, paleontological, geochronological, petrological and also geochemical properties of the DEAA have been defined. In the present study, ensimatic arc units have been distinguished from ophiolitic association for the first time, in the region. As a result of the study, the DEAA is divided into two levels and lower level named as the Kartal unit and upper level named as the izibüyük unit. In the Kartal unit, basaltic and andesitic lavas with their equivalent pyroclastic rock units are dominant. Radiolarite and mudstones interbedded within the Kartal unit of DEAA have Turonian and Santonian age. In addition, the age of basalt samples of DEAA are 98.7 ± 2.4 Ma, defined using the~(40)Ar/39 Ar method. The izibüyük unit of DEAA comprises conglomerate, sandstone, claystone, mudstone,clayey limestone, micritic limestone with volcanic interbeds and also calciturbidites. Santonian-Maastrichtian ages were obtained from this unit of the DEAA. In conclusion, the age of DEAA is widely accepted as Late Cretaceous. After the evaluation of the analysis, the volcanics of the DEAA originated from calcalkaline-basalts, which reflect ensimatic arc magmatism. 相似文献
94.
95.
Prediction of ground vibrations resulting from the blasting operations in an open-pit mine by adaptive neuro-fuzzy inference system 总被引:3,自引:0,他引:3
The aim of this study is to predict the peak particle velocity (PPV) values from both presently constructed simple regression
model and fuzzy-based model. For this purpose, vibrations induced by bench blasting operations were measured in an open-pit
mine operated by the most important magnesite producing company (MAS) in Turkey. After gathering the ordered pairs of distance
and PPV values, the site-specific parameters were determined using traditional regression method. Also, an attempt has been
made to investigate the applicability of a relatively new soft computing method called as the adaptive neuro-fuzzy inference
system (ANFIS) to predict PPV. To achieve this objective, data obtained from the blasting measurements were evaluated by constructing
an ANFIS-based prediction model. The distance from the blasting site to the monitoring stations and the charge weight per
delay were selected as the input parameters of the constructed model, the output parameter being the PPV. Valid for the site,
the PPV prediction capability of the constructed ANFIS-based model has proved to be successful in terms of statistical performance
indices such as variance account for (VAF), root mean square error (RMSE), standard error of estimation, and correlation between
predicted and measured PPV values. Also, using these statistical performance indices, a prediction performance comparison
has been made between the presently constructed ANFIS-based model and the classical regression-based prediction method, which
has been widely used in the literature. Although the prediction performance of the regression-based model was high, the comparison
has indicated that the proposed ANFIS-based model exhibited better prediction performance than the classical regression-based
model. 相似文献
96.
Xu Chu Ozan Akça Fred Gaidies Ivano Gennaro Weiqiang Ji 《Journal of Metamorphic Geology》2023,41(1):121-141
The thermal histories of Himalayan leucogranites provide critical information for unravelling the post-collisional geodynamics of the Himalayas. The Ramba Dome is located at the intersection of the Tethyan Himalayan leucogranite belt with the Yadong–Gulu Rift and hosts several generations of granitic intrusions. Of these intrusions, the 8-Ma two-mica granites and garnet leucogranite dykes are the youngest of Himalayan leucogranites. In this study, we focus on the carbonaceous staurolite schist located ~1.3 km from the intrusion to constrain the thermal history of the aureole that marked the cessation of leucogranite magmatism. The schist contains euhedral garnet and staurolite porphyroblasts in a foliated matrix of muscovite + biotite + chlorite + plagioclase + quartz + graphite. The staurolite shows minor compositional variations from the inclusion-free core to the inclusion-rich rim. By contrast, the garnet features a distinctive bell-shaped Mn profile and increasing Mg# from the garnet core to rims. In a graphite-bearing equilibrium phase diagram for a modified bulk composition with garnet cores removed, the garnet rim composition suggests a peak temperature of ~550°C, consistent with an independent thermometer based on the Raman spectra of carbonaceous materials (RSCM; 548 ± 9°C). The P–T condition lies within the narrow low-variance field bracketed by the staurolite-in and chlorite-out boundaries, indicating minimal overstepping of staurolite nucleation and growth. On the other hand, the garnet core composition indicates 520°C at 2.5 kbar, about 40°C higher than the predicted garnet-in boundary (~480°C). This apparent temperature overstep corresponds to a small chemical affinity (<5 kJ/mol 12 O) for garnet nucleation, comparable to previous estimates. The sharp boundaries of the high-Ca sector zoning in the core indicate limited diffusion modification (~1.5 Ma if at the peak temperature). The short thermal pulse involves advective heat transfer by leucogranite emplacement, followed by rapid cooling toward the end of Himalayan magmatism and rapid exhumation likely facilitated by the Yadong–Gulu Rift. 相似文献
97.
Hydrogeology of karst aquifer systems in SW Turkey and an assessment of water quality and contamination problems 总被引:1,自引:0,他引:1
Aysen Davraz Remzi Karaguzel Iskender Soyaslan Erhan Sener Fatma Seyman Sehnaz Sener 《Environmental Geology》2009,58(5):973-988
The aim of this research is to determine the relationship between groundwater flow and water quality of different ground and
surface water basins in the southwest Turkey. In addition, groundwater vulnerability is assessed taking into consideration
groundwater flow and quality. The autochthonous Beydaglari limestone is the major karstic aquifer in the region. According
to the groundwater level map of alluvium aquifers in the basins, groundwater discharge toward the carbonate aquifer is direct
and indirect. The hydrogeological connection between ground and surface water basins occurs via the karstic aquifer located
at the bottom of the alluvium bottom. In Egirdir lake, water also discharges in the karstic aquifer via karstic sinkholes
at the western border of the lake. In the research area, general groundwater discharge is toward the Mediterranean Sea by
means of autochthonous carbonate system, according to hydrogeological investigations, research of lineament and hydraulic
conductivities. This result is supported by the locations of lineaments and shore springs discharging from the limestone.
In addition, spreading of contaminants via karstic aquifer to great distance has been clearly identified. 相似文献
98.
Lars P. Dyrud Kelly Denney Julio Urbina Diego Janches Erhan Kudeki Steve Franke 《Earth, Moon, and Planets》2004,95(1-4):89-100
In this paper, we use radar observations from a 50 MHz radar stationed near Salinas, Puerto Rico, to study the variability
of specular as well as non-specular meteor trails in the E-region ionosphere. The observations were made from 18:00 to 08:00 h
AST over various days in 1998 and 1999 during the Coqui II Campaign [Urbina et al., 2000, Geophys. Rev. Lett. 27, 2853–2856]. The radar system had two sub-arrays, both produced beams pointed to the north in the magnetic meridian plane,
perpendicular to the magnetic field, at an elevation angle of approximately 41 degrees.
The Coqui II radar is sensitive to at least two types of echoes from meteor trails: (1) Specular reflections from trails oriented
perpendicular to the radar beam, and (2) scattering, or, non-specular reflections, from trails deposited with arbitrary orientations.
We examine and compare the diurnal and seasonal variability of echoes from specular and non-specular returns observed with
the Coqui II radar. We also compare these results with meteor head echo observations made with the Arecibo 430 MHz radar.
We use common region observations of these three types of meteor echoes to show that the diurnal and seasonal variability
of specular trails, non-specular trails, and head echoes are not equivalent. The implications of these results on global meteor
mass flux estimates obtained from specular meteor observations remains to be examined. 相似文献
99.
100.
Abdurrahman Dokuz İbrahim Uysal Wolfgang Siebel Mehmet Turan Robert Duncan Miğraç Akçay 《Contributions to Mineralogy and Petrology》2013,166(5):1443-1468
New geochemical and isotopic data for post-collisional Early Eocene and Late Miocene adakitic rocks from the eastern part of the Sakarya Zone, Turkey, indicate that slab and lower crustal melting, respectively, played key roles in the petrogenesis of these rocks. The Early Eocene Yoncal?k dacite (54.4 Ma) exhibits high Sr/Y and La/Yb ratios, low Y and HREE concentrations, moderate Mg# (44–65), and relatively high εNd and low ISr values, similar to adakites formed by slab melting associated with subduction. Geochemical composition of the Yoncal?k dacite cannot be explained by simple crystal fractionation and/or crustal contamination of andesitic parent magma, but is consistent with the participation of different proportions of melts derived from subducted basalt and sediments. Sr/Y correlates horizontally with Rb/Y, and Pb/Nd correlates vertically with Nd isotopic composition, indicating that Sr and Pb budgets are strongly controlled by melt addition from the subducting slab, whereas positive correlations between Th/Nd and Pb/Nd, and Rb/Y and Nb/Y point to some contribution of sediment melt. In addition to low concentrations of heavy rare earth elements (~2–3 times chondrite), a systematic decrease in their concentrations and Nb/Ta ratios with increasing SiO2 contents suggests that slab partial melting occurred in the garnet stability field and that these elements were mobilized by fluid flux. These geochemical and isotopic signatures are best explained by slab breakoff and fusion shortly after the initiation of collision. Although the Late Micone Tavda?? rhyolite (8.75 Ma) has some geochemical features identical to adakites, such as high Sr/Y and La/Yb ratios, low Y and HREE concentrations, other requirements, such as sodic andesite and/or dacite with relatively high MgO and Mg# (>50), relatively high Ni and Cr, low K2O/Na2O (<0.4), high Sr (>400 ppm), for slab-derived adakites are not provided. It is sodic in composition and shows no traces of fractionation from dacitic parent magma. Low Nd and high Sr isotope ratios suggest derivation by partial fusion of calc-alkaline, juvenile crust with high Sr/Y and La/Yb ratios. 相似文献