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111.
豫西地区秦岭造山带武当群Nd-Hf同位素组成及其物源特征 总被引:1,自引:0,他引:1
武当群变质沉积-火山岩组合是南秦岭地体中重要的基底岩石,其形成时代和地球化学特征可以为理解秦岭造山带的构造演化提供重要的证据.本文报道豫西地区武当群上部沉积岩和下部中-酸性火山岩Sm-Nd同位素和锆石Lu-Hf同位素组成,探讨火山岩成因和沉积岩物源的同位素特征.上部沉积岩的碎屑锆石初始ε_(Hf)值变化在-30~+10之间,对应的模式年龄值t_(DM2)在1.0Ga至3.2Ga之间,初始ε_(Nd)值在-4.0至-6.0之间.沉积物源表现为主要与扬子陆块有亲缘关系的地壳物质和近源的下部火山岩混合的特征.火山岩的锆石初始εHf值变化在-35~+15之间,对应的模式年龄值t_(DM2)在0.8Ga至3.5Ga之间,集中于1.5~1.8Ga和2.2~2.4Ga两个峰值.2个变质石英角斑岩样品初始ε_(Nd)值分别为-9.2和-10.7,而报道的湖北武当群的玄武-安山质熔岩的初始ε_(Nd)值以正值为主.因此,武当群不同类型的火山岩可能存在着成因差异.具有低初始ε_(Nd)值和ε_(Hf)值特征的火山岩可能由地壳物质的重熔而形成的;有些火山岩具有初始ε_(Hf)值变化范围较大(-35~+15)或正初始ε_(Nd)值的特点,可能是壳、幔物质混合成因,有显著的幔源或新生地壳物质的贡献.武当群Nd-Hf同位素组成和碎屑锆石年龄分布特征表明,与扬子陆块有亲缘关系的南秦岭地体在元古代期间可能经历多期地壳增生和再造作用. 相似文献
112.
Jack Katzfey Kim Nguyen John McGregor Peter Hoffmann Suppiah Ramasamy Hiep Van Nguyen Mai Van Khiem Thang Van Nguyen Kien Ba Truong Thang Van Vu Hien Thuan Nguyen Tran Thuc Doan Ha Phong Bang Thanh Nguyen Tan Phan-Van Trung Nguyen-Quang Thanh Ngo-Duc Long Trinh-Tuan 《Asia-Pacific Journal of Atmospheric Sciences》2016,52(2):91-106
To assist the government of Vietnam in its efforts to better understand the impacts of climate change and prioritise its adaptation measures, dynamically downscaled climate change projections were produced across Vietnam. Two Regional Climate Models (RCMs) were used: CSIRO’s variable-resolution Conformal-Cubic Atmospheric Model (CCAM) and the limited-area model Regional Climate Model system version 4.2 (RegCM4.2). First, global CCAM simulations were completed using bias- and variance-corrected sea surface temperatures as well as sea ice concentrations from six Coupled Model Intercomparison Project Phase 5 (CMIP5) global climate models. This approach is different from other downscaling approaches as it does not use any atmospheric fields from the GCMs. The global CCAM simulations were then further downscaled to 10 km using CCAM and to 20 km using RegCM4.2. Evaluations of temperature and precipitation for the current climate (1980-2000) were completed using station data as well as various gridded observational datasets. The RCMs were able to reproduce reasonably well most of the important characteristics of observed spatial patterns and annual cycles of temperature. Average and minimum temperatures were well simulated (biases generally less than 1oC), while maximum temperatures had biases of around 1oC. For precipitation, although the RCMs captured the annual cycle, RegCM4.2 was too dry in Oct.-Nov. (-60% bias), while CCAM was too wet in Dec.- Mar. (130% bias). Both models were too dry in summer and too wet in winter (especially in northern Vietnam). The ability of the ensemble simulations to capture current climate increases confidence in the simulations of future climate. 相似文献
113.
Predicting soil erosion hazard in Lattakia Governorate(W Syria) 总被引:1,自引:0,他引:1
Mohammed Safwan Khallouf Alaa Alshiehabi Omran Bao Pham Quoc Thi Thuy Linh Nguyen Nam Thai Van Tran Anh Duong Harsányi Endre 《国际泥沙研究》2021,36(2):207-220
The main objective of this study is to predict soil erosion in the Lattakia Governorate(WSyria)using the Water Erosion Prediction Project model(WEPP)and to compare the result with that of the RUSLE.Field survey and data collection were carried out,and 44 soil samples were analyzed.In addition,all the necessary input files were prepared for use in the WEPP model and RUSLE.Results show that more than of 80%of the locations studied experience slight to moderate erosion(less than 5 t/ha/y),whereas the rest of the locations experience severe soil erosion hazard.Moreover,the volume of runoff estimated by the WEPP model is in the range of 51e321 mm,and the R^2 between the simulated soil erosion and the predicted runoff reached 0.68.Interestingly,the R^2 between the WEPP model and RUSLE is 0.56,which indicates a good correlation between the two models. 相似文献
114.
The oxygenation kinetics of nanomolar concentrations of Fe(II) in aqueous solution have been studied in the absence and presence of millimolar concentrations of phosphate over the pH range 6.0-7.8. At each phosphate concentration investigated, the overall oxidation rate constant varied linearly with pH, and increased with increasing phosphate concentration. A model based on equilibrium speciation of Fe(II) was found to satisfactorily explain the results obtained. From this model, the rate constants for oxygenation of the Fe(II)-phosphate species FeH2PO4+, FeHPO4 and FePO4− have been determined for the first time. FePO4− was found to be the most kinetically reactive species at circumneutral pH with an estimated oxygenation rate constant of (2.2 ± 0.2) × 10 M−1 s−1. FeH2PO4+ and FeHPO4 were found to be less reactive with oxygen, with rate constants of (3.2 ± 2) × 10−2 M−1 s−1 and (1.2 ± 0.8) × 10−1 M−1 s−1, respectively. 相似文献
115.
Pham Tich Xuan Nguyen Van Pho O. L. Gas’kova S. B. Bortnikova 《Geochemistry International》2013,51(11):931-938
This study provides an assessment of the environmental impact of open pit mining operations at the Cay Cham titanomagnetite-ilmenite deposit (northern Vietnam). The results of surface water sampling indicate the formation of acid mine drainage and contamination of adjacent areas by heavy metals (Cu, Zn, Ni, and Mn). The acid mine drainage is produced by oxidation leaching of sulfide minerals associated with primary mineralization owing to the low neutralization potential of the natural waters in the humid environment of tropical rainforest. The study showed that alternating dry and wet seasons typical of this climatic region promote the generation of stored acidity leading to a sharp decrease in pH of drainage water during the wet season and result in the negative impacts of this mine on both flowing and stagnant surface waters. 相似文献
116.
Ngoc Thach Nguyen Ngoc Hai Pham Xuan Canh Pham Thi Thuy Hang Nguyen Van Lam Nguyen Thi Thanh Thuy Duong 《Environmental Earth Sciences》2013,70(2):531-542
Ha Giang is one of the largest, northern border provinces of Vietnam, consisting of four districts: Yen Minh, Quan Ba, Dong Van and Meo Vac. This province features varied karst landscape of Carboniferous–Permian limestone. The region has been recognized by UNESCO as one of the 77 geological parks in the world and the second in Southeast Asia on 3 October 2012. In the dry season, little or no rain is recorded; therefore, surface water is very scarce. For this reason, proper delineation and exploitation of the groundwater resource is critical for sustainable water supply. This has been identified as an important challenge under the scientific project KC-08-10 in the national program KC-08. Remote sensing and GIS were used to decipher the signature of karst water in the highland of Ha Giang. Information layers generated were subjected to multi-criteria evaluation using analytic hierarchy process for decision making to identify ideal locations for groundwater prospecting. The study resulted in delineation of ten zones for all regions and 18 ideal drilling sites in Tam Son Town of Quan Ba District. Drilling and resistivity soundings were performed to assess the success of the interpretation. Deep resistivity survey confirmed low resistivity (200–300 Ωm) near the identified potential sites in Tam Son Town of Quan Ba District. Further, successful drilling at site LKTS1 with a discharge of 7–9 l/s is observed, proving the potential of this methodology for rapid exploration of groundwater in water-scare karst terrains of Vietnam. 相似文献
117.
Rock association and regional unconformity are identified based on field survey and mapping for the stratigraphy, tectonics, metamorphic rock and igneous rocks in the Song Da zone, the northwestern Vietnam. Pre-Cenozoic in the Song Da zone is divided into three structural layers: (1) the Presinian crystalline basement, (2) the Cambrian-lower part of Upper Triassic, and (3) the upper part of Upper Triassic-Cretaceous. The Pre-Cenozoic structural successions of the Song Da zone show similar features with those of the Yangtze-South China plate: (1) In the Presinian, both of them have TTG complex and Khondalite series of similar ages and experienced similar tectonic evolution; (2) In the Cambrian-early Upper Triassic, the phosphorite and thick-layered limestone are comparable, and the Permian-Triassic basalt in the Song Da zone has genetic mechanism similar to that of the Emeishan basalt; (3) In the late Upper Triassic-Cretaceous, the volcanic-sedimentary faulted basins and thick continental red beds are comparable to those in East China. It can be concluded that the Song Da zone should have been part of the southwestern Yangtze-South China plate, and the boundary between the Yangtze-South China plate and Indochina plate is the Song Ma suture zone which contains ophiolite remnants. Tectonic settings of different structural layers indicate that the Song Da Zone experienced geological events such as the Columbia and Rodinia Supercontinent, sedimentation of the stable platform cover, closure of the Paleo-Tethys, and NW subduction of the Paleo-Pacific plate to the Eurasian plate. The Pre-Cenozoic basement of the Yinggehai Basin is the seaward extension of the Song Da zone, which shows similar tectonic features. 相似文献
118.
119.
This paper examines the current procedure for determining the soil-water characteristic curve (SWCC) model with a particular focus on its application to slope stability analysis under transient unsaturated seepage conditions. A series of laboratory experiments was performed to determine the SWCC of different soils, ranging from high plasticity clay to silty sand, found across the Korean Peninsula. The experimental results were utilized to identify the suitable SWCC model for each soil type based on the fitting criterion. Also, this paper developed a numerical framework for infinite slope stability analysis under transient unsaturated seepage conditions. The significant advantage of the proposed framework, from the practical viewpoint, is to directly predict the timing of failure and potential failure plane based on rainfall recording. The effect of choice of SWCC models on predictability in stability analysis was evaluated by adopting the present framework along with the identified SWCC models. Furthermore, a case study of landslides after a 3-month rainfall in Pohang, Korea, was revisited to assess the performance of the proposed framework. The obtained results demonstrate the significant role of SWCC model on the results of slope stability analysis. The analysis using the SWCC model satisfying the fitting criterion could still not capture the real behavior of unsaturated soil. The comprehensive transient analysis is strongly suggested as a complementary means to the current fitting criterion for determining the suitable SWCC model for stability analysis under transient seepage conditions. 相似文献
120.
Aiyelokun Oluwatobi Pham Quoc Bao Aiyelokun Oluwafunbi Malik Anurag Adarsh S. Mohammadi Babak Linh Nguyen Thi Thuy Zakwan Mohammad 《Natural Hazards》2021,109(2):1557-1588
Natural Hazards - Rainfall intensity or depth estimates are vital input for hydrologic and hydraulic models used in designing drainage infrastructures. Unfortunately, these estimates are... 相似文献