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31.
32.
Nilufar?Islam Manuel?J.?Rodriguez Ashraf?Farahat Rehan?SadiqEmail author 《Stochastic Environmental Research and Risk Assessment (SERRA)》2017,31(7):1759-1775
Contaminant intrusion in a water distribution network (DN) has three basic pre-conditions: source of contaminant (e.g., leaky sewer), a pathway (e.g., water main leaks), and a driving force (e.g., negative pressure). The impact of intrusion can be catastrophic if residual disinfectant (chlorine) is not present. To avoid microbiological water quality failure, higher levels of secondary chlorination doses can be a possible solution, but they can produce disinfectant by-products which lead to taste and odour complaints. This study presents a methodology to identify potential intrusion points in a DN and optimize booster chlorination based on trade-offs among microbiological risk, chemical risk and life-cycle cost for booster chlorination. A point-scoring scheme was developed to identify the potential intrusion points within a DN. It utilized factors such as pollutant source (e.g., sewer characteristics), pollution pathway (water main diameter, length, age, and surrounding soil properties, etc.), consequence of contamination (e.g., population, and land use), and operational factors (e.g., water pressure) integrated through a geographical information system using advanced ArcMap 10 operations. The contaminant intrusion was modelled for E. Coli O156: H7 (a microbiological indicator) using the EPANET-MSX programmer’s toolkit. The quantitative microbial risk assessment and chemical (human health) risk assessment frameworks were adapted to estimate risk potentials. Booster chlorination locations and dosages were selected using a multi-objective genetic algorithm. The methodology was illustrated through a case study on a portion of a municipal DN. 相似文献
33.
The present study was conducted to evaluate the effect of either individual or combined wheat bran(WB) replacement with Azolla pinnata supplemented with Digestin~(TM) in the diet of freshwater prawn, Macrobrachium rosenbergii Postlarvae(PL) on growth performance, nutrient utilization, chemical body composition and survival(%). Experimental diets were a wheat bran-soybean based diet with no Azolla and Digestin~(TM)(control, T_1), and diets containing 17% Azolla supplemented with Digestin~(TM) 0%(T_2), 1%(T_3), 2%(T_4) and 3%(T 5). Each experimental diet was allocated into three tanks(6 m~3/tank) fed for 12 wks. Each tank was subdivided into three equal pens by nets(2 m~3) and stoked with 84 PL/m~2. The experimental diets were readily consumed by prawns PLs where both high growth and good feed efficiency were achieved for all diets. The results showed that the diets containing A. pinnata supplemented with Digestin? at the level up to 3% have the higher growth and better nutrient utilization than the control diet. No differences were observed for moisture and protein content among the experimental diets. However, the highest protein content was observed on prawns fed on diets T_1 and T 5 respectively, while the lowest value was recorded for T_4 diet. The results also show that prawn PLs fed the diets contain A. pinnata and supplemented with Digestin~(TM) recorded the highest values of body lipid content compared to the control diet. Feed efficiency and economic conversion rate(ECR) values show that economic performance and the cost-effectiveness of the A. pinnata supplemented with up to 3% Digestin~(TM) recorded the highest net return, and therefore it is recommended for prawn, M. rosenbergii PL's. These results are clearly indicating that A. pinnata have a good potential for use in prawn diets at reasonable levels than other conventional diets. 相似文献
34.
The Cretaceous of Afghanistan is marked by great facies diversity. The evolution of Cretaceous basins is part of a complex accretionary history involving three distinct tectonic units namely the Asian (Russian) Block separated from the Indian plate by a rather well defined transcurrent fault (Chaman-Nuski). The southwestern component is representedby the Iran-Afghanistan plate. The Lower Cretaceous of the Asian Block is represented by the Red-Grit Series which isconformable to the underlying Upper Jurassic sequences. The transition is marked by evaporitic facies dominated by salt,gypsum and marl deposits. In south Afghanistan volcanic rocks occur at Farah, with the emplacement of plutonics inwest-central Afghanistan. The Upper Cretaceous of north Afghanistan is marked by richly fossiliferous, lime stone-dominated sequences. The Upper Cretaceous of southern Afghanistan is marked by strong ophiolitic magrmatism. 相似文献
35.
Mohamed W. Ali-Bik Hussein I. M. Metwally Mohamed G. Kamel Ashraf M. A. Wali 《Environmental Earth Sciences》2011,62(1):151-159
Biogenic gypsum in the form of microbialite and potential domal stromatolite as well as endoevaporitic dolomite are deposited
in a perennial saline basin characterized by microbial bloom. Deposition environment, mode of occurrence, and microscopic
investigation including SEM of these precipitates are discussed in conjunction with XRD, XRF, and FTIR data. Combined effects
of salinity gradient and the wind action on the maturity of gypsum outcrop are evident. A characteristic multi-color vertical
gypsum profile reflects steep gradient of oxi-anoxic microenvironments and encodes diverse seasonal microbial communities.
Direct impact of microbial signature in gypsum crystal habit is conspicuous. Endoevaporitic authigenic dolomite is recorded
in specific horizons in interstices of selenite layers. 相似文献
36.
ShigeyukiSuzuki AbdulR.Ashraf HakuyuOkada 《东北亚地学研究》2004,7(2):149-155
Sedimentary facies of the Tsagayan Formation is distributed in the eastern Zeya-Bureya Basin has been analyzed. The formation is of the Maastrichtian to Danian in age and characterized by the cyclicity of the fining-upwards successions. Analysis of environmental changes during the K/T boundary is the focus of this study. Five facies have been identified: Facies A, thick and laterally extensive coarse-grained to medium-gained sandstone units, interpreted as channelfill deposits; Facies B, parallel-laminated to massive mudstone units interpreted as interchannel lakes and flood plain deposits; Facies C, sheet-like medium-grained to fine-grained sandstones interpreted as crevasse splay deposits; Facies D, coal to coaly mudstone beds interpreted as deposits of peatlands; Facies E, very poorly sorted sandy mudstone beds interpreted as debris flow deposits. Fluvial environments with the low-relief fiat topography was inferred. A channel transported large volumes of clasts, and a flood basin with interchannel lakes and peatlands was deciphered. Any distinct change of sedimentary environments has not been identified throughout the Tsagayan Formation (including the K/T boundary). However, two beds of debris flow deposits were identified. The one occurs at the uppermost part of the lower Tsagayan Subformation and contains dinosaur fossils. The other is intercalated in the upper Tsagayan Subformation. 相似文献
37.
This paper presents an inelastic element for the analysis of beams resting on two-parameter foundations. The element is derived from a two field mixed formulation with independent approximation of forces and displacements. The values for the two parameters of the foundation are derived through an iterative technique that is based on an assumption of plane strain for the soil medium. This iterative behavior is repeated at each time step of the nonlinear solution algorithm. The nonlinear response of structures resting on this improved two-parameter foundation model is analyzed following both a Vlasov and a Pasternak approach. Numerical examples that clarify the advantage of the newly developed model are conducted. These studies confirmed the importance of accounting for the foundation second parameter, and the efficiency and accuracy of the proposed model. 相似文献
38.
The study of dynamics of the particle creation in relativistic viscous fluid in Robertson-Walker Universe is studied by using Brans-Dicke theory. The behaviour of these solutions with respect to Dirac's hypothesis are investigated along with the discussion of the physical parameters as well as the variable gravitational constant. By adopting a particular method of integration, exact solutions are obtained and physical interpretations are presented. 相似文献
39.
RésuméDans ce travail, des modèles de prévision de l’érosion spécifique des bassins versants en insuffisance voire en absence de jaugeages ont été élaborés, en fonction des paramètres climatiques, hydromorphométriques et de la couverture végétale, au droit des sites de barrages et retenues collinaires dans le bassin très érodé qu’est l’Algérois-Hodna-Soummam. Les paramètres régissant l’érosion ont été soigneusement sélectionnés sur la base d’une recherche bibliographique et regroupés en deux catégories distinctes par le biais de l’analyse en composantes principales. Deux méthodes statistiques ont été appliquées: la première, basée sur la régression multiple et la deuxième sur les réseaux de neurones artificiels. Des résultats très satisfaisants sont obtenus en testant, par validation croisée, la validité du modèle neuronal composé de: lame écoulée, densité de drainage, pente moyenne du bassin et précipitation moyenne annuelle comme variables d’entrées avec un coefficient de détermination de 0,81 et une erreur quadratique moyenne de 0,19.Editeur Z.W. Kundzewicz; Editeur associé G. MahéCitation Salhi, C., Touaibia, B., et Zeroual, A., 2013. Les réseaux de neurones et la régression multiple en prédiction de l’érosion spécifique: cas du bassin hydrographique Algérois-Hodna-Soummam (Algérie). Hydrological Sciences Journal, 58 (7), 1573–1580. 相似文献
40.
Georgios Etsias Gerard A. Hamill Jesús F. Águila Eric M. Benner Mark C. McDonnell Ashraf A. Ahmed Raymond Flynn 《水文研究》2021,35(4):e14120
Laboratory experiments and numerical simulations were utilized in this study to assess the impact of aquifer stratification on saltwater intrusion. Three homogeneous and six layered aquifers were investigated. Image processing algorithms facilitated the precise calculation of saltwater wedge toe length, width of the mixing zone, and angle of intrusion. It was concluded that the length of intrusion in stratified aquifers is predominantly a function of permeability contrast, total aquifer transmissivity and the number of heterogeneous layers, being positively correlated to all three. When a lower permeability layer overlays or underlays more permeable zones its mixing zone widens, while it becomes thinner for the higher permeability strata. The change in the width of the mixing zone (WMZ) is positively correlated to permeability contrast, while it applies to all strata irrespectively of their relative vertical position in the aquifer. Variations in the applied hydraulic head causes the transient widening of WMZ. These peak WMZ values are larger during saltwater retreat and are negatively correlated to the layer's permeability and distance from the aquifer's bottom. Moreover, steeper angles of intrusion are observed in cases where low permeability layers overlay more permeable strata, and milder ones in the inverse aquifer setups. The presence of a low permeability upper layer results in the confinement of the saltwater wedge in the lower part of the stratified aquifer. This occurs until a critical hydraulic head difference is applied to the system. This hydraulic gradient value was found to be a function of layer width and permeability contrast alike. 相似文献