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191.
Hydrogeological and mixing process of waters in aquifers in arid regions: a case study in San Luis Potosi Valley,Mexico 总被引:1,自引:0,他引:1
J. A. Ramos-Leal V. J. Martínez-Ruiz J. R. Rangel-Mendez M. C. Alfaro de la Torre 《Environmental Geology》2007,53(2):325-337
The climatic conditions of arid regions are characterized by high temperatures, low precipitation and high evapotranspiration
rates that can explain the reduced recharge of aquifers. Thus, in these regions, there are some problems related to the groundwater
quality and recharge that makes worse the problem of groundwater supply. A model, taking into account ternary mixtures, is
presented and applied to a case study: the aquifer of San Luis Potosi valley located in the highlands of the central part
of Mexico. In this valley, four hydrochemical facies were identified that correspond to the Ca–Na + K–HCO3, Na + K–Ca–HCO3, Ca–HCO3 and Ca–SO4 types. From this characterization, it was found out that the recharge area (known as Bledos Graben) is located at the SE
of the valley; the deep water flow comes from there (Villa de Reyes and Alvarez Range) to the center of the valley. Mixture
fractions were obtained by using chlorides and fluorides as conservative elements, from which it was possible to quantify
the contribution of each member to the groundwater quality. According to these results, the contributions to the water extracted
from this aquifer are as follows: shallow flows 50%, deep flows from Villa de Reyes 27%, and flows coming from the Alvarez
Ranges about 15%. 相似文献
192.
Groundwater in the Hang-Jia-Hu Plain, eastern China, is a drinking water source for local residents. Groundwater samples were
collected from large-diameter hand-dug wells and boreholes for comparison of their iron and manganese concentrations, as well
as other ions. The results show that iron and manganese concentrations are relatively high, exceeding drinking water standards
by several times. Aquifer sediment samples contain abundant iron (30,790 mg kg−1) and manganese (602 mg kg−1). The results of correspondence factor analysis of the hydrochemistry data and the liberation experiments (using seawater
and rainwater as leachants) suggest that iron and manganese in shallow groundwater come from the sediment in the Holocene
aquifer. A reductive environment involving relatively high total dissolved solids and organic carbon in the aquifer system
is favorable to iron and manganese transferring from the sediment to groundwater and stabilizes these ions. Shallow, large-diameter
hand-dug wells provide oxic conditions that decrease the concentrations of dissolved iron and manganese in the well water.
Résumé Dans la Plaine de Hang-Jia-Hu, à l’Est de la Chine, les eaux souterraines constituent une ressource en eau potable pour les autochtones. Des échantillons d’eau souterraine ont été prélevés dans des puits de large diamètre creusés manuellement et dans des forages, afin de confronter leurs concentrations en fer, manganèse et autres ions. Les résultats montrent des concentrations en fer et manganèse relativement hautes, souvent au-delà des limites de potabilité. Les échantillons de sédiments de l’aquifère contiennent des quantités abondantes de fer (30,790 mg kg−1) et de manganèse (602 mg kg−1). Les résultats de l’analyse factorielle de correspondance des données hydrochimiques et des tests de libération (utilisant l’eau de mer et l’eau de pluie comme vecteurs) suggèrent que le fer et le manganèse contenus dans les aquifères superficiels proviennent des sédiments de l’aquifère holocène. Un environnement réducteur, impliquant une quantité élevée de solides dissous et de carbone organique dans le système aquifère, est favorable à un transfert du fer et du manganèse depuis les sédiments vers les eaux souterraines, et stabilise les ions considérés. Les puits peu profonds, de large diamètre et creusés à la main créent des conditions oxydantes qui abaissent les concentrations en fer et manganèse dissous dans l’eau du puits.
Resumen El agua subterránea en la Llanura de Hang-Jia-Hu, al este de China, es una fuente de agua potable para los residentes locales. Las muestras de agua subterránea fueron recogidas en pozos de gran diámetro excavados a mano y en pozos barrenados con el objeto de comparar las concentraciones de hierro y manganeso, y también las de otros iones. Los resultados muestran que las concentraciones de hierro y manganeso son relativamente altas, excediendo varias veces los límites para agua potable. Las muestras de sedimentos tomadas del acuífero contienen abundante hierro (30,790 mg kg−1) y manganeso (602 mg kg−1). Los resultados del análisis de correspondencia de los datos hidroquímicos y experimentos de liberación (usando agua de mar y agua de lluvia como lixiviantes) sugieren que los iones hierro y manganeso en las aguas subterráneas someras provienen de los sedimentos acuíferos del Holoceno. Un ambiente reductor que contiene relativamente alta cantidad de sólidos totales disueltos y carbono orgánico en el sistema acuífero es favorable para la transferencia de hierro y manganeso desde los sedimentos al agua subterránea y para estabilizar estos iones. Los pozos poco profundos, de gran diámetro, excavados a mano, suministran condiciones de oxidación que disminuyen las concentraciones de hierro y manganeso disueltos en el agua del pozo.相似文献
193.
194.
A. Guendouz A. S. Moulla W. M. Edmunds K. Zouari P. Shand A. Mamou 《Hydrogeology Journal》2003,11(4):483-495
The hydrogeochemical and isotopic evolution of groundwaters in the Mio–Pliocene sands of the Complexe Terminal (CT) aquifer in central Algeria are described. The CT aquifer is located in the large sedimentary basin of the Great Oriental Erg. Down-gradient groundwater evolution is considered along the main representative aquifer cross section (south–north), from the southern recharge area (Tinrhert Plateau and Great Oriental Erg) over about 700 km. Groundwater mineralisation increases along the flow line, from 1.5 to 8 g l?1, primarily as a result of dissolution of evaporite minerals, as shown by Br/Cl and strontium isotope ratios. Trends in both major and trace elements demonstrate a progressive evolution along the flow path. Redox reactions are important and the persistence of oxidising conditions favours the increase in some trace elements (e.g. Cr) and also NO3 ?, which reaches concentrations of 16.8 mg l?1 NO3-N. The range in 14C, 0–8.4 pmc in the deeper groundwaters, corresponds with late Pleistocene recharge, although there then follows a hiatus in the data with no results in the range 10–20 pmc, interpreted as a gap in recharge coincident with hyper-arid but cool conditions across the Sahara; groundwater in the range 24.7–38.9 pmc signifies a distinct period of Holocene recharge. All δ18O compositions are enriched relative to deuterium and are considered to be derived by evaporative enrichment from a parent rainfall around ?11‰ δ18O, signifying cooler conditions in the late Pleistocene and possibly heavy monsoon rains during the Holocene. 相似文献
195.
196.
The Oramiriukwa River is within the sandy coastal plain strata of the Benin formation (Miocene–Recent). The base flow is very
high ranging from 79.13–98.56%, which is caused by the excellent hydraulic interconnection between the river and the adjacent
unconfined aquifer. Recharge rates are high, estimated to range from 1.8×1012–2.5×1012 m3/year. Coastal sands are medium-to-coarse grained, moderately-to-poorly sorted, angular to subangular, with lenses of clay
and clayey fine-grained sands. The coastal sands and clay lenses form aquifer and aquitard systems, which are unconfined to
semi-confined. Groundwater recharge potential is high. Runoff from precipitation is low. Groundwater and surface water are
fairly acidic; pH ranges from 5.5–6.1 (groundwater) and 5.8–6.5 (surface water), and hardness is generally low. Chemical analysis
and percentage sodium show that groundwater and surface water are somewhat potable after some pH modification of the surface
water. The waters are good for agricultural use, especially for irrigation and poultry water supply. However, pollution from
landfill leachate is serious.
Electronic Publication 相似文献
197.
The distribution of fresh and salt water in coastal aquifers is influenced by many processes. The influence of aquifer heterogeneity
and human interference such as land reclamation is illustrated in the Belgian coastal plain where, around A.D. 1200, the reclamation of a tidally influenced environment was completed. The aquifer, which was filled with salt water, was
thereafter freshened. The areal distribution of peat, clay, silt and sand influences the general flow and distribution of
fresh and salt water along with the drainage pattern and results in the development of fresh-water lenses. The water quality
in and around the fresh-water lenses below an inverted tidal channel ridge is surveyed. The hydrochemical evolution of the
fresh water lens is reconstructed, pointing to cation exchange, solution of calcite and the oxidation of organic material
as the major chemical reactions. The formation and evolution of the fresh water lens is modelled using a two-dimensional density-dependent
solute transport model and the sensitivity of drainage and conductivities are studied. Drainage level mainly influences the
depth of the fresh-water lens, whereas the time of formation is mainly influenced by conductivity.
Electronic Publication 相似文献
198.
Moisture samples obtained from unsaturated-zone profiles in sands from northern Nigeria were used to obtain recharge estimates
using the chloride (Cl) mass-balance method and to produce records of past recharge and climatic events. Recharge rates range
from 14–49 mm/year, on the basis of unsaturated-zone Cl values and rainfall chemistry measured over eight years at three local
stations. The unsaturated-zone results also provide a record of the changing recharge and climatic events of the past 80 years;
this record compares quite well with modelling results using precipitation data from Maiduguri, especially for the late 20th-century
period of drought. The best fit for the model is made, however, by using a lower mean rainfall Cl (0.65 mg/l) than that obtained
from the mean of the field results (1.77 mg/l Cl). This result implies that the measured rainfall Cl probably overestimates
the depositional flux of Cl, although the lower value is comparable to the minimum of the measured rainfall Cl values (0.6 mg/l
Cl). Recharge estimates made using these lower Cl values range from 16–30 mm/year. The spatial variability was then determined
using results from 360 regional shallow wells over 18,000 km2.
Using the revised rainfall estimate, the Cl balance indicates a value of 43 mm for the regional recharge, suggesting that
either additional preferential flow is taking place over and above that from the vadose one, or that the regional recharge
represents inputs from earlier wetter periods. These recharge estimates compare favourably with those from hydraulic modelling
in the same area and suggest that the recharge rates are much higher than values previously published for this area. High
nitrate (NO3) concentrations (NO3-N>Cl) preserved under aerobic conditions in the vadose zone reflect secondary enrichment from N-fixing vegetation, as occurs
elsewhere in the Sahel.
Electronic Publication 相似文献
199.
本文分析了1991年1月5日缅甸7.6级大震前,云南省西部水化网观测到的水化异常,这些异常不仅有水氡,还有水汞、CO2、Ca(++)、Mg(++)和Cl-等,异常的时间不仅有中长期,还有短临异常。文中根据观测事实指出,一次强烈地震发生之前,水化学的异常范围不仅仅在距震中200公里的范围之内,甚至在距震中500公里的范围内也有分布。 相似文献
200.
在进行水化学样品全分析数据的统计处理中,应用原始数据和经过标准化处理后的数据,进行统计量计算时出现了不一致性。如本无相关关系的原始数据子成份,在经标准化处理后的数据子成份中却出现了负相关;原始数据和标准化数据的协方差阵相差甚远;因子分析图解中出现了曲面结构等。本文根据JohnAitchison提出的对数比法,结合实例,对这一问题进行了探索,论证了对数比法在水化学资料处理中的可行性。 相似文献