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61.
62.
Mohammad A. Hoque Aftab A. Khan M. Shamsudduha Muhammad S. Hossain Tariqul Islam Shahid H. Chowdhury 《Environmental Geology》2009,56(8):1687-1695
This study investigated the relationship between near-surface lithology and the spatial variability of As concentrations using
sediment grain-size analysis and electromagnetic induction survey in the southeast Bangladesh. It has been observed that the
aquifers overlain by finer sediments have higher concentrations of As in groundwater, whereas As concentrations are remarkably
low in aquifers having permeable sandy materials or thinner silt/clay layer at the surface. The near-surface lithology acts
as a controlling factor for spatial distributions of groundwater As within the very shallow depths (<15 m). Shallow alluvial
aquifers can provide low-As drinking water in many areas of the country when tube wells are properly installed after investigation
of the overlying near-surface sediment attributes and hydraulic properties. 相似文献
63.
Among several lithostratigraphic subdivisions of the Gaj Formation of Miocene age, the Jhill limestone is entirely different
with respect to its colour, texture and structures. This limestone unit has been evaluated to elaborate its geochemical and
sedimentological characteristics. The distribution of various elements in the acid-soluble fraction has been studied in order
to determine their mineralogy, sedimentary environment, facies and diagenesis. Mineralogy, recrystallization and other diagenetic
changes are the main factors affecting the distribution of trace elements and their mutual relationships in the limestones.
Samples of the Jhill limestone show depletion in large-sized ions (Sr, Pb & K) and also in the ions that are not compatible
with calcite space group. Elements (Fe, Mn, Zn, Cu & Co) having distribution coefficient (D) above unity for natural calcites,
are more enriched. Microscopic and X-ray studies revealed nearly complete conversion of aragonite into stable low-Mg calcite.
An attempt has also been made to verify the reefal conditions for these limestones on the basis of geochemical studies. The
plots of Sr and other facies-indicator elements show that the majority of the beds belong to forereef flank facies with some
algal banks. Low Mg/Ca and Sr/Ca ratios suggest that a phreatic diagenetic environment prevailed after the deposition. High
concentrations of Cr, Ni, and Co in the Jhill limestone show a positive correlation with a higher amount of insoluble residue,
which reflects a relatively high rate of influx of terrigenous material. 相似文献
64.
ShahidA.Khan M.AliShah M.Qaisar 《地震学报》2003,25(4):361-373
通过确定性和概率性方法,对发展迅速的巴基斯坦沿海地区进行了地震危险性评估.根据该地区的地震构造和地质条件,确定了5个地震区域的11个断层作为该地区的潜在震源,计算了每个潜在震源的最大可能震级.根据与之相关震源的最大可信震级,计算了7个沿海城市的峰值加速度(PGA).瓜达尔(Gwadar)和奥尔马腊(Ormara)的峰值加速度分别为0.21和0.25 g,处于地震危险性水平较高的地区;杜尔伯德(Turbat)和卡拉奇(Karachi)位于地震危险性水平较低的地区,峰值加速度小于0.1 g.同时,分别绘制了50年和100年超越概率为10%的PGA区划图,区划图的分区间隔为0.05 g. 相似文献
65.
Biogeochemical investigation of Tamarix aphylla,a plant species, of the Las-bela area has been made.This area mainly consists of ophiolites associated with sed-imentary rocks of Jurassic and Cretaceous age .Quantitative estimations of important biogenic trace elements such as Fe,Mn,Pb,Zn,Cu,Cr,Ni, and Co have been carried out .Anomalous concentrations of these elements in plant species of certain regions can be used to locate possible occurrences of ore deposits in the area.The comparative strdy also reveals appreciable variations in the composition of trace elements in plants.The possible causes of variation in the constitrents of Tamarix aphylla from different localities have been discussed in the light of bed rock nature, mo-bility of element and average abundance in the plant. 相似文献
66.
The pressure acid leach process is the most widely used method of metal extraction from laterite ores. The self-weight settling rate of the ore slurries governs the throughput of the process and is improved by adding synthetic polymers. The charge density, molecular weight, and dosage of the polymers are the key factors influencing the settling rate of the slurries. This interdisciplinary paper uses the geotechnical understanding of hindered sedimentation for a mining engineering application. A conceptual fuzzy rule-based model was developed to evaluate the initial hydraulic conductivity of polymer-modified laterite ore slurries. Identification of control parameters and selection of the model architecture (fuzzy rule-base) were based on expert judgment. The developed model was trained and validated using bench-scale settling test data. The model reasonably predicts the initial hydraulic conductivity of polymer-added laterite ore slurry with a coefficient of determination of 0.75. Rank correlation coefficient-based sensitivity analyses indicated that charge density was the most significant polymer parameter followed by molecular weight and then by dosage. Charge density accounted for more than 97% of variability in the initial hydraulic conductivity estimates for both anionic and cationic polymers. 相似文献
67.
Erum Bashir Shahid Naseem Salma Hamza 《中国地球化学学报》2007,26(3):259-266
Quantitative estimation of ground and stream waters draining through sedimentary rocks of the Pab and Mor ranges (Jurassic-Cretaceous) and the Bela ophiolite has been made. The degree of correspondence among cations and anions has been estimated in order to evaluate their mutual relationships. The abundance of major ions is interpreted to be related to bedrocks and climatic conditions, which may contribute to the genetic affiliation. The log TDS and Na/Na Ca ratio reflected supremacy of weathering of rocks with some influence of evaporation. Ionic relationship is exhibited in the form of Stiff diagrams. Patterns of ionic composition revealed high NaCl, medium Ca(HCO3)2 and low MgSO4. Piper diagram has been used to classify the hydrofacies. The important hydrogeochemical parameters have been estimated for assessment of groundwater quality for domestic purposes in accordance to WHO. Irrigation water qualities have been evaluated in terms of EC, SAR, RSC, ESP and pH. 相似文献
68.
Anuar Sefie Ahmad Zaharin Aris Mohammad Firuz Ramli Tahoora Sheikhy Narany Mohd Khairul Nizar Shamsuddin Syaiful Bahren Saadudin Munirah Abdul Zali 《Environmental Earth Sciences》2018,77(10):397
Continual expansion of population density, urbanization, agriculture, and industry in most parts of the world has increased the generation of pollution, which contributes to the deterioration of surface water quality. This causes the dependence on groundwater sources for their daily needs to accumulate day by day, which raises concerns about their quality and hydrogeochemistry. This study was carried out to increase understanding of the geological setup and assess the groundwater hydrogeochemical characteristics of the multilayered aquifers in Lower Kelantan Basin. Based on lithological data correlation of exploration wells, the study area can be divided into three main aquifers: shallow, intermediate and deep aquifers. From these three aquifers, 101 groundwater samples were collected and analyzed for various parameters. The results showed that pH values in the shallow, intermediate and deep aquifers were generally acidic to slightly alkaline. The sequences of major cations and anions were Na+ > Ca2+ > Mg2+ > K+ and HCO3? > Cl? > SO42? > CO32?, respectively. In the intermediate aquifer, the influence of ancient seawater was the primary factor that contributed to the elevated values of electrical conductivity (EC), Cl? and total dissolved solids (TDS). The main facies in the shallow aquifer were Ca–HCO3 and Na–HCO3 water types. The water types were dominated by Na–Cl and Na–HCO3 in the intermediate aquifer and by Na–HCO3 in the deep aquifer. The Gibbs diagram reveals that the majority of groundwater samples belonged to the deep aquifer and fell in the rock dominance zone. Shallow aquifer samples mostly fell in the rainfall zone, suggesting that this aquifer is affected by anthropogenic activities. In contrast, the results suggest that the deep aquifer is heavily influenced by natural processes. 相似文献
69.
Muhammad Rustam Khan Shahid Saleem Bilali Fahad Hameed Awais Rabnawaz Sohail Mustafa Naveed Azad Muhammad Basharat Abrar Niaz 《Arabian Journal of Geosciences》2018,11(6):131
The present geophysical study deals with the ores and crustal demonstration of southeastern Hazara and its adjoining areas of Azad Jammu and Kashmir, Pakistan, on the basis of terrestrial gravity and magnetic data. Tectonically, the study area lies in the Lesser Himalayas as well as to an extent in the sub-Himalaya, more specifically in the western limb of Hazara Kashmir Syntaxis. In this study, 567 gravity and 508 magnetic stations have been measured with CG-5 gravimeter and proton precession magnetometer, respectively. The collected data have been processed by applying standard corrections and then different types of maps were prepared. The ores in the area have been delineated by the qualitative interpretation of residual Bouguer anomaly and reduction to pole total magnetic intensity maps, whereas regional structures are demarcated by the Bouguer anomaly and regional Bouguer anomaly maps. The positive contour closures on the residual Bouguer anomaly map indicate the iron ore and phosphate, whereas negative contour closures are the effects of low-density material which consists of gypsum and soapstone. The pole-reduced total intensity map also shows the negative and positive contour closures almost in the same localities and confirms the residual Bouguer anomaly map. The geological model computed on the basis of Bouguer anomaly demarcated a series of faults between different rock units in the study area. The Kashmir Boundary Thrust cuts the western limb of Hazara Kashmir Syntaxis near the apex in the north of Muzaffarabad and marks the boundary between Murree Formation and carbonates of Abbottabad Formation. The gravity model also suggests that the thickness of the crust increases towards the northeast. 相似文献
70.
Natural Hazards - The objective of this study was to reconstruct the long-term drought and flood time series to analyze their changing characteristics in Hengshui City of North China. Disaster... 相似文献