首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   54篇
  免费   4篇
大气科学   7篇
地球物理   12篇
地质学   25篇
海洋学   5篇
天文学   6篇
综合类   3篇
  2022年   1篇
  2021年   2篇
  2019年   1篇
  2018年   5篇
  2017年   2篇
  2016年   5篇
  2015年   4篇
  2014年   8篇
  2013年   4篇
  2012年   6篇
  2011年   3篇
  2009年   1篇
  2008年   4篇
  2007年   4篇
  2006年   2篇
  2005年   1篇
  2003年   1篇
  1990年   2篇
  1978年   1篇
  1962年   1篇
排序方式: 共有58条查询结果,搜索用时 31 毫秒
51.
52.
From 2006 to 2008, microbial water quality was monitored along the Georgian coast of the Black Sea. Temperature, pH, salinity, and dissolved oxygen were measured, along with a variety of aquatic microbial parameters, including heterotrophic plate count (HPC), total culturable bacterial count (TCBC), and chlorophyll a (Chl-a) concentration. Total and fecal coliforms and total enterococci counts were recorded as indicators of fecal pollution. Vibrio bacteria, and Escherichia coli- and Vibrio-specific bacteriophages were isolated and enumerated to determine their relationships to standard marine pollution indicators.Persistent microbial pollution was observed, particularly in the summer months, with a higher rate of contamination in estuaries. Microbial indicators generally showed seasonal dependence, suggesting that temperature may influence bacterial dynamics in this environment. No correlation was apparent between fecal pollution indicators and physical-chemical and aquatic microbial parameters, although there were significant relationships amongst the indicators themselves, as well as with the prevalence of Vibrio bacteria and phage.  相似文献   
53.
Ocean Science Journal - This study seeks to evaluate levels of seven trace metals (Cr, Mn, Fe, Cu, Zn, Pb and Hg) and biochemical (proteins, lipids and carbohydrates) alterations in muscle tissue...  相似文献   
54.
Various extraction procedures were employed for measuring extractable concentrations of potential toxic elements in soil. The extractability of Cd, Cu, Pb and Zn in four contaminated and four non-contaminated soils of Japan, was compared by single extraction (CaCl2, DTPA, NH4Cl, 0.1 M HCl and 1 M HCl ) and sequential extraction procedures [(six operationally defined chemical phases, viz. water soluble (Fl), exchangeable (F2), carbonate (F3), oxide (F4), organic (F5) and residual (F6) fractions)]. Extractability of metals from soils samples varied depending on metals and/or extradants used. Among the extradants, 1 M HCl extracted the largest proportion of Cd (79 to 96% of total), Cu (61 to 83%), Pb (51 to 99%) and Zn (23 to 52%) from soils followed by 0.1 M HCl, NH4Cl, DTPA and CaCl2. In all the extradants, the proportion of extractability of metals was higher in the contaminated soils than the non-contaminated soils. Regardless of soils and extradants, relative extractability was higher for Cd as compared to other three metals. The use of 1 M HCl may be recommended for first-level screening of soil contamination with heavy metals. The other four weak extradants are believed to provide a better assessment of bioavailable/mobile metals content in soils than 1 M HCl extradant. However, 0.1 M HCl mobilized all four metals irrespective of soil types, therefore, might be the best choice if only one extradant is to be used. The sequential extraction procedures showed 22 to 64% of total Cd was in the mobile fraction (sum of Fl to F3), while the corresponding values for Cu, Pb and Zn in this fractions were 2 to 23% suggesting higher mobility of Cd than other three metals. The single extraction procedures are simple and easy to perform and obtained results are comparable with sequential extraction procedure.  相似文献   
55.
Collapsing soils, which undergo a large decrease in bulk volume virtually instantaneously upon saturation and/or load application, are found in arid and semi-arid regions of the world. In the western and midwestern U.S., problems resulting from collapsing soils are being recognized due to rapid industrial and urban developments. A probabilistic analysis of the distribution of such soils would be a rational approach for quantifying risk involved for a project in an area where such soils are found. Indicator kriging was applied to seven sets of collapse and collapse-related soil parameters to obtain the probability that a certain parameter is more or less than a predefined critical value for low, medium, and high collapse susceptibility. Results are presented in the form of probability contour plots with known variance of estimation of the probability. The ability to predict the probability of occurrence of collapse and collapse-related soil parameters for different critical values with a known degree of certainty is invaluable to planners, developers, and geotechnical engineers.  相似文献   
56.
The living conditions of the Bihari camp dwellers of Bangladesh are an embarrassment to the country's social environment. An investigation was made about the socio-economic condition of the Biharis living in the Khalishpur camp, Khulna. A comparison has been made between the Biharis and equivalent Bengali slum dwellers in Khalishpur. The data were collected from primary sources. A 10% systematic sampling was undertaken to collect a total of 150 Bihari households and through a 20% systematic sampling 150 Bengali households were surveyed by questionnaires. Data analysed both qualitatively and quantitatively indicate that the Biharis are leading an extremely substandard life when food consumption, medical expenditure, schooling, income and employment pattern were considered. The condition as prevalent in the camp has led to a high rate of infectious diseases which is likely to aggrevate creating environmental hazards. The country then may face serious social problems which should be prevented through gearing up the process of repatriation and through encouraging community participation in improving their economic and social environment.The study was sponsored by CONCERN a voluntary Irish Organization in Bangladesh.  相似文献   
57.
Summary Using the values of vertical velocities computed byJensen (1960) and the values of the meridional component of the wind for the months of January and April 1958, the covariances of both quantities were evaluated at different levels at various latitudes. These covariances are tabulated and the terms associated with transient eddies are compared to the standing eddy terms, the relative magnitudes of both contributions being finally investigated.
Résumé En employant les valeurs du mouvement vertical calculées parJensen (1960) et les valeurs des composantes méridionales des vents pour les mois de Janvier et Avril 1958, les covariances des deux quantités ont été evaluées aux différents niveaux dans différentes latitudes. Ces covariances sont tabulées et les valeurs associées aux perturbations transientes et stationnaires sont comparées afin de donner un aperçu sur l'importance relative des deux procès.
  相似文献   
58.
Hydrochemical, multivariate statistical and inverse hydrogeochemical modeling techniques were used to investigate groundwater recharge, flow and the hydrochemical evolution within the Akaki volcanic aquifer system, central Ethiopia. The hydrochemical and multivariate statistical techniques are mutually supportive and the extracted information was analyzed together with environmental isotope data. Results reveal five spatial groundwater zones with defined hydrochemical facies, residence times, stable isotopic signals and hydrochemical evolution. These zones are designated as the (1) Intoto, (2) central, (3) Filwuha fault, (4) south zones and (5) a highly polluted sub-sector identified within the central zone. Both the hydrochemical and multivariate statistical analyses have shown the central sub-sector as being spite of differentially polluted by , Cl and and its tritium content shows recent recharge. Due to the fact that the main recharge source is precipitation, the hydrochemical and environmental isotope data clearly indicated that the central and southern sectors are also recharged from domestic waste water and leakage from water mains and reservoirs. Inverse hydrogeochemical modeling demonstrated reactions of silicate minerals in a CO2 open system and precipitation of kaolinite, chalcedony, and rare calcite satisfy the observed change in water chemistry from north to south following the regional flow direction.

Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Résumé Des techniques relevant de l’hydrochimie, des statistiques multivariées et de la modélisation inverse hydrogéochimique, ont été utilisées dans le cadre de l’étude de la recharge des eaux souterraines, de l’écoulement et de l’évolution hydrochimique dans le système volcanique aquifère d’Akaki au centre de l’Ethiopie. Les techniques hydrochimiques et multivariées se supportent mutuellement et l’information extraite a été analysée avec les données isotopiques environnementales, des temps de résidence, des signaux isotopiques stables et une évolution hydrochimique. Ces zones ont été désignées comme le (1) Intoto, (2) le centre, (3) la faille de Filwuha, (4) les zones sud et (5) un sous-secteur fortement pollué identifié dans la zone centrale. Les analyses statistiques hydrochimiques et multivariées ont montré que le sous-secteur central a été différemment pollué par , Cl et , tandis que la teneur en tritium montre une recharge récente. Malgré le fait que la principale source de recharge soit les précipitations, les données hydrochimiques et isotopiques indiquent clairement que les secteurs centres et sud sont également rechargés par les eaux usées domestiques et les fuites de réservoirs et canalisations d’eau. La modélisation hydrogéochimique inverse a démontré les réactions des minéraux silicatés dans un système ouvert au CO2, et la précipitation de kaolinite, de calcédoine, et la rareté de la calcite satisfont les changements observés dans la chimie de l’eau du nord vers le sud en suivant la direction régionale de l’écoulement.

Resumen Se utilizaron la hidroquímica y técnicas de modelación hidrogeoquímica inversa y estadística multivariada, para investigar la recarga del agua subterránea, el flujo y la evolución hidroquímica, dentro del sistema acuífero volcánico Akaki, Etiopía Central. La hidroquímica y las técnicas estadísticas multivariadas se complementan entre si y la información así extraída se analizó junto con los datos de isótopos ambientales. Los resultados revelan cinco zonas diferentes de agua subterránea, con facies hidroquímicas, tiempos de residencia, improntas isotópicas estables y una evolución hidroquímica definidas. Estas zonas se designan como (1) Intoto, (2) Central, (3) Falla de Filwuha, (4) las Zonas del sur y (5) un sub-sector altamente contaminado identificado dentro de la zona central. Tanto los análisis estadísticos multivariados como la hidroquímica, han mostrado al sub-sector central como contaminado diferencialmente por , Cl y y su contenido de tritio muestra una recarga reciente. A pesar del hecho que la fuente principal de recarga es la precipitación, los datos de hidroquímica y de isótopos ambientales indican que los sectores central y del sur, también se recargan a partir de agua doméstica usada y del goteo de las conducciones del acueducto y de sus reservorios. El modelamiento hidrogeoquímico inverso demostró reacciones de minerales silicatados en un sistema de CO2 abierto, y la precipitación de caolinita, calcedonia, y rara vez de calcita, satisfacen el cambio observado en la química de agua del norte a sur, siguiendo la dirección del flujo regional.
  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号