全文获取类型
收费全文 | 156篇 |
免费 | 2篇 |
国内免费 | 6篇 |
专业分类
测绘学 | 4篇 |
大气科学 | 4篇 |
地球物理 | 29篇 |
地质学 | 108篇 |
海洋学 | 2篇 |
天文学 | 6篇 |
综合类 | 5篇 |
自然地理 | 6篇 |
出版年
2022年 | 5篇 |
2021年 | 3篇 |
2020年 | 8篇 |
2019年 | 4篇 |
2018年 | 11篇 |
2017年 | 16篇 |
2016年 | 9篇 |
2015年 | 11篇 |
2014年 | 12篇 |
2013年 | 15篇 |
2012年 | 13篇 |
2011年 | 8篇 |
2010年 | 10篇 |
2009年 | 5篇 |
2008年 | 4篇 |
2007年 | 3篇 |
2006年 | 9篇 |
2004年 | 2篇 |
2003年 | 1篇 |
2001年 | 1篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1987年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有164条查询结果,搜索用时 15 毫秒
41.
A modified Newton-Raphson iterative technique is formulated for obtaining the static configuration of the Lazy "S" flexible marine riser between the floater and mid-arch buoy under its submerged self weight and the applied top tension. The geometrically non-linear problem is solved by finite difference with the above technique. The problem is formulated as a regular boundary value problem with specified moments and deflections at both ends. Usually the bending stiffness of the flexible riser made of Coflexip pipe is very low. By use of the above analysis, several flexible riser configurations are analyzed and their characteristic behaviors are investigated. Also, changes in the riser characteristics due to quasi-static motion of the floater end are estimated for the safety of the riser layout. 相似文献
42.
Alzahraa Abo HABIBAH Kamal DAHAB Ashraf SHABANA Samir KAMH Hekmat IBRAHIM 《《地质学报》英文版》2022,96(3):1082-1097
The El Minia governorate lies within the Nile Valley, surrounded by calcareous plateaus to the east and west. The present study focuses on the hydrogeochemistry of the Eocene limestone aquifer at some wadis in the east El Minia governorate, Eastern Desert, Egypt. Hydrogeologically, two main aquifers are encountered in the study area, namely the Maghagha marly limestone and the Samalut chalky limestone aquifers. The Maghagha aquifer is composed of alternating layers of marly limestone and shale with thicknesses ranging from 3.49 m to 177.05 m and a groundwater depth ranging from 8.5 m to 59.27 m which reflects low groundwater potentiality. The groundwater salinity representing this aquifer ranges from 603.5 mg/L to 978.5 mg/L, reflecting fresh water type. Samalut aquifer is made up of chalky, cavernous and fractured limestone with thickness ranging from 30 m to 205 m and groundwater depth ranging from 9 m to 86.77 m, which indicates good groundwater potential. The groundwater salinity of the concerned aquifer ranges from 349.7 mg/L to 2043.9 mg/L, reflecting fresh to possibly brackish water types. Groundwater in the study area is of meteoric water origin; recent recharge is mainly controlled through the presence of fractures and their densities. The majority of groundwater samples in the study area are suitable for drinking and irrigation purposes. 相似文献
43.
Kamal A. S. M. Maksud Hossain Farhad Rahman Md. Zillur Ahmed Bayes Sammonds Peter 《Landslides》2022,19(2):465-478
Landslides - The Forcibly Displaced Myanmar Nationals (FDMN), historically known as ‘Rohingya’ who fled the 2017 ethnic atrocities and genocide in the Northern Rakhine State of Myanmar,... 相似文献
44.
Hamou Djellit Hervé Bellon Aziouz Ouabadi Mohamed E.M. Derder Bernard Henry Boualem Bayou Allaoua Khaldi Kamal Baziz Mounir K. Merahi 《Comptes Rendus Geoscience》2006,338(9):624-631
Palaeozoic formations of the Tassilis Oua-n-Ahaggar (southeastern Hoggar) include magmatic rocks in the Tin Serririne syncline. Slight contact metamorphism of the overlying bed and studies of anisotropy of magnetic susceptibility of these rocks show that the latter correspond to sills and NW–SE or north–south dykes. 40K/40Ar dating of separated feldspars and whole rock for one sample and of whole rock for two other samples give a mean age of (at the 2-σ level), thus corresponding to a Lower Carboniferous (Tournaisian) age. Taking into account both the age of this magmatism and the stratigraphic and structural data for this region suggests that dolerites were emplaced within distensive zones that are related to the reactivation of Panafrican faults. To cite this article: H. Djellit et al., C. R. Geoscience 338 (2006). 相似文献
45.
Mokhles Kamal Azer Robert J. Stern Jun-Ichi Kimura 《International Journal of Earth Sciences》2010,99(2):245-267
New geochemical, isotopic, and geochronological data and interpretations are presented for late Neoproterozoic intrusive carbonates
and related rocks of southern Sinai, Egypt (northernmost Arabian–Nubian Shield). The Tarr carbonates are coarsely crystalline
and related to explosive emplacement of hypabyssal and volcanic albitite at 605 ± 13 Ma. The carbonates associated with the
albitites are divisible into two types: primary dolomitite and secondary breunneritite (Fe-rich magnesite). The dolomitite
was clearly intrusive but differs from classic igneous carbonatites, containing much lower abundances of incompatible elements,
such as REE, U, Th, Rb, Nb, Y, P, Sr, Zr, Ba, and total alkalies. The breunneritite is a secondary replacement of dolomitite,
probably marking the roots of a vigorous hydrothermal system. Albitites show pristine abundances of major and trace elements
and were not subjected to a major metamorphic overprint. They are relatively more fractionated, alkaline and related to within-plate
A-type magmas, were emplaced in an extensional or non-compressive tectonic regime in the cupola of high-level A-type granite.
Tarr albitites may represent residual magma remaining after near-total crystallization of an A-type granite pluton at depth,
forcibly emplaced into the roof above the cooling pluton. The intrusive dolomitite exsolved from highly differentiated albitite
melt, in the apical regions of a still-buried alkaline “A-type” granite pluton that was rich in CO2; these volatiles migrated upwards and towards the cooler margins of the magma body. Late NNE-SSW extension allowed a shallow-level
cupola to form, into which albitite melts and carbonate fluids migrated, culminating in explosive emplacement of albitite
breccia and intrusive carbonate. Isotopic compositions of Tarr dolomitite and albitite indicate these are consanguineous and
ultimately of mantle origin. Magmatic volatiles fenitized the wall rock, while submarine hydrothermal activity transformed
some of the dolomitite into breunneritite. Recognition of Tarr-type should encourage similar hypabyssal complex intrusions
to be sought for in association with A-type granitic plutons elsewhere. 相似文献
46.
We propose a general stochastic model for the UT1/LOD system and derive the corresponding Kalman filter model. This stochastic model consists of an arbitrary sum of continous time autoregressive moving average (ARMA) processes, each chosen to characterize a different frequency band. The transition matrix which corresponds to the overall system and the time-dependent process noise covariance matrix are derived.Based on the general formulation, several models for UT1 were derived from spectral analysis of the Space 92 UT1 series (Gross,1993). Using Space 92 as the reference series, the candidate models were compared based on their ability to predict UT1 and LOD up to 30 days in the absence of data. These candidate models were compared with the JPL operational Kalman Earth Orientation Filter (KEOF) which assumes a random walk model for LOD (Morabito et al.,1987). The results of the comparison revealed that autoregressive modeling the 40–50 day oscillation in the LOD reduces the LOD prediction error by 10prediction. 相似文献
47.
Sorption of dissolved Fe2+ on bentonite was studied using a batch technique. The distribution coefficient, Kd , was evaluated for a bentonite-iron system as a function of contact time, pH, sorbent and sorbate concentrations, and temperature. Sorption results were interpreted in terms of Freundlich's and Langmuir's equations. Thermodynamic parameters for the sorption system were determined at three temperatures: 298°, 308°, and 318°K. The values of ΔH°(-4.0 kjmol−1 ) and ΔG°(-2.46 Kjmol−1 ) at 298°K (25°C) suggest that sorption of iron on bentonite is an exothermic and a spontaneous process. The ΔG° value became less negative at higher temperatures and, therefore, less iron was sorbed at higher temperatures. The desorption studies with 0.01 M CaCl2 and deionized water at iron loading on bentonite showed that more than 90 wt% of the iron is irreversibly sorbed, probably due to the fixation of the iron by isomorphous replacement in the crystal lattice of the sorbent. 相似文献
48.
Water Resources - The present study is an attempt to apply principal component analysis (PCA) for spatial assessment of water quality parameters that are responsible for water quality deterioration... 相似文献
49.
Water Resources - Groundwater resources are depleting at an alarming rate all over the world. Therefore, ensuring water security is the foremost priority of every nation. This paper presents a... 相似文献
50.
Karakoram Himalaya(KH) has continental climatic conditions and possesses largest concentration of glaciers outside the polar regions. The melt water from these glaciers is a major contributor to the Indus river. In this study, various methods have been used to estimate the ice volume in the Karakoram Range of glaciers such as Coregistration of Optically Sensed Images and Correlation(COSI-Corr) method and Area-Volume relations. Landsat 8 satellite data has been used to generate the ice displacement, velocity and thickness map. Our study for 558 Karakoram glaciers revealed that the average ice thickness in Karakoram is 90 m. Ground Penetrating Radar(GPR) survey has been conducted in one of the KH glacier i.e. Saser La glacier and the collected GPR data is used for the validation of satellite derived thickness map. GPR measured glacier thickness values are found comparable with satellite estimated values with RMSE of 4.3 m. The total ice volume of the Karakoram glaciers is estimated to be 1607±19 km3(1473±17 Gt), which is equivalent to 1473±17 km3 of water equivalent. Present study also covers the analysis of glacier surface displacement, velocity and ice thickness values with reference to glacier mean slope. 相似文献