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101.
This paper establishes that an isotropic spatial correlation function in the form of a modified Bessel function of the second kind, first order, can be used to model the spatial variability of a pollution concentration field over a sufficiently long period of time in which the variability due to meteorological factors has been smoothed out. The corresponding cumulative semivariogram is derived and fitted by nonlinear least-squares to monthly averaged ozone data at 18 monitoring stations of the Sydney region. The good fit of the model indicates that the Sydney airshed has homogeneous and isotropic subregions whose radius of influence is about 17 km. The Bessel function form of the spatial correlation has a physical meaning as it is derived from the diffusion equation; hence, it is expected that the model can be used, in general, to represent the spatial variability of a smoothed homogeneous and isotropic concentration field.  相似文献   
102.
长江流域发展对长江口水域功能开发的影响   总被引:3,自引:0,他引:3  
长江口水域是上海市重要水源地,同时兼具工农业取水、通航、纳污、围垦等多种功能,长江口已成为上海市建设世界级城市的重要支撑之一,其水资源的开发、利用和保护已成为人们关注的焦点。重点分析了随着长江流域社会经济的发展,流域水旱灾害、水土流失、污染物排放、大型水利工程建设等因素对长江口水域功能的影响,提出长江口现状过境水资源量为9335×108m3/a,上海市最大可开发利用的资源量约在3680×108m3/a;长江口水域水质基本符合II类标准,但近岸水域的污染不容忽视;长江口咸潮入侵成为长江口水资源利用的最大障碍,每年长江口的氯化物超标天数在45d;长江流域的来沙量有减少的趋势,多年平均输沙量为4.35×108t。最后,就河口水域功能开发提出了相关对策建议。  相似文献   
103.
比较分析法是监测部门分析数据的常用方法,使用EXCEL的数据库和列表函数可方便快捷地获得复杂条件下同比、环比或其它比较分析的结果。掌握EXCEL的单元格引用,可极大减轻大量重复类型公式的输入,迅速地完成数据比较分析。以城市环境空气监测数据的比较分析为例,展示了一种快速实现比较分析的方法与步骤。  相似文献   
104.
Fetuses and neonates are known to be high-risk groups for Methylmercury(MeHg)exposure.MeHg can be transferred to the fetus through the placenta and to newborn offspring through breast milk.The aim of the present study was to investigate the neurotoxic effects of low doses of MeHg(1 and 5 μg/m L in drinking water) administration,from gestational day 1 to postnatal day(PND) 21,on the neurobehavioral development of rats.The results showed that the no-observed-effect level of MeHg is somewhere in the range of 1–4 μg/mL.Neurobehavioral development analysis revealed a delayed appearance of cliff drop and negative geotaxis reflexes in the 5 μg/mL MeHg exposure group.Developmental exposure to MeHg affected locomotor activity functions for the females,but not for the males,implying that the female pups were more vulnerable than the male pups.All pups exposed to 5 μg/mL of MeHg showed a significant deficit in motor coordination in the rotarod test compared with controls,and the highest accumulated concentrations of Hg were found in the cerebellum,followed by the hippocampus and cerebral cortex,indicating that the cerebellum is a possible target for MeHg toxicity.We demonstrated adverse effects of developmental exposure to MeHg associated with tissue concentrations very close to the current human body burden of this persistent and bioaccumulative compound.  相似文献   
105.
Safety strategies in the process and other industries depend ultimately on how much the owners and operators decide should be spent on protection systems to protect workers and the public from potential plant hazards. An important input to decisions of this sort is the value of life, which needs to be assessed in a valid manner so that safety decisions can be made properly. A key reference point for decisions on safety investment decisions in the UK is a 1999 study on the “value of a prevented fatality” (VPF), which employs a two-injury chained model that has been shown previously by the present authors to possess internal inconsistencies. The 1999 study made extensive use of utility functions to interpret survey data, and it is this feature that is explored in this paper. It will be explained here how different forms of utility function of the Exponential family can produce the same figure for an intermediate parameter in the calculation of the VPF from the two-injury chained model. Exponential utility functions are, however, unlikely to provide a realistic representation if their calculated risk-aversions need to be negative or zero in order to match survey data, which would imply an incautious attitude amongst those taking decisions on safety. The use of an incompletely specified wealth threshold in the utility modelling is explored in the light of a proposal by the authors of the 1999 study that a second utility function can be used to determine the individual's utility when his wealth lies below the threshold, which constitutes the lower limit of validity of the first utility function. The proposition is shown to be untenable. The results presented in this paper raise further concerns about the lack of validity of the 1999 study on which the UK VPF is based and hence on the safety decisions that have been made in consequence.  相似文献   
106.
With the aim of wood production with negligible negative effects on biodiversity and ecosystem processes, a silvicultural practice of selective logging with natural regeneration has been implemented in European beech forests (Fagus sylvatica) during the last decades. Despite this near‐to‐nature strategy, species richness of various taxa is lower in these forests than in unmanaged forests. To develop guidelines to minimize the fundamental weaknesses in the current practice, we linked functional traits of saproxylic beetle species to ecosystem characteristics. We used continental‐scale data from 8 European countries and regional‐scale data from a large forest in southern Germany and forest‐stand variables that represented a gradient of intensity of forest use to evaluate the effect of current near‐to‐nature management strategies on the functional diversity of saproxylic beetles. Forest‐stand variables did not have a statistically significant effect on overall functional diversity, but they did significantly affect community mean and diversity of single functional traits. As the amount of dead wood increased the composition of assemblages shifted toward dominance of larger species and species preferring dead wood of large diameter and in advanced stages of decay. The mean amount of dead wood across plots in which most species occurred was from 20 to 60 m3/ha. Species occurring in plots with mean dead wood >60 m3/ha were consistently those inhabiting dead wood of large diameter and in advanced stages of decay. On the basis of our results, to make current wood‐production practices in beech forests throughout Europe more conservation oriented (i.e., promoting biodiversity and ecosystem functioning), we recommend increasing the amount of dead wood to >20 m3/ha; not removing dead wood of large diameter (50 cm) and allowing more dead wood in advanced stages of decomposition to develop; and designating strict forest reserves, with their exceptionally high amounts of dead wood, that would serve as refuges for and sources of saproxylic habitat specialists. Efectos Actuales del Manejo Casi Natural de Bosques sobre la Composición de Atributos Funcionales de Escarabajos Saproxílicos en Bosques de Haya  相似文献   
107.
山西省“三生”功能协同/权衡关系分析   总被引:2,自引:0,他引:2  
康庆  郭青霞  丁一  张扬 《自然资源学报》2021,36(5):1195-1207
为探究生产—生活—生态(“三生”)功能协调情况,基于综合评价模型和力学平衡模型,选用2005年、2010年和2018年土地利用类型和统计数据,测度山西省“三生”功能时空演变及协同/权衡关系特征。结果表明:(1)2005—2018年“三生”功能时空分异特征明显,生产功能为下降态势,呈现出“平原高,山区低”的分布格局;生活功能持续上升,空间分布与生产功能相似;生态功能呈上升状态,但需注意恶化倾向,空间格局稳定。(2)研究期间,“三生”功能协同性显著提升且趋势合理,空间分布与生产、生活功能趋同。(3)依据“三生”功能协调度偏离情况,划分功能主导区和提升区,明确各县域功能特征。研究结果可为国土空间规划提供依据。  相似文献   
108.
灾害事件发生后,信息的有效传播对于灾害救助意义重大.灾害事件往往伴随电力、交通、通讯的中断,导致许多传播媒介无法发挥作用,而广播媒介因其较强的抗灾害能力在灾害信息传播过程中保持了相对畅通,成为灾害救助的重要媒介.本文介绍了广播媒介在自我救助、专业救助和社会救助中的不同作用,进一步探讨了几种常见的传播媒介的抗灾害能力,并针对广播媒介在灾害救助中存在的问题提出了一些建议.  相似文献   
109.
Abstract: This study incorporates the newly available Gravity Recovery and Climate Experiment (GRACE) water storage data and water table data from well logs to reduce parameter uncertainty in Soil and Water Assessment Tool (SWAT) calibration using a SUFI2 (sequential uncertainty fitting) framework for the Lower Missouri River Basin. Model evaluations are performed in multiple stages using a multiobjective function consisting of multisite streamflow and GRACE water storage data as well as a groundwater component. Results show that (1) a model calibrated with both streamflow and GRACE data simultaneously can maintain the water balance for the whole basin, but may improperly partition surface flow and base flow. Additional inclusion of the groundwater constraint can significantly improve the model performance in groundwater hydrological processes. In our case, the estimation of specific yield of shallow aquifers has been increased to 10?2 from previous much underestimated level (<10?3). (2) The daily streamflow data are needed to confine the parameters related to water flow in channels such as the Manning’s coefficient, which are less sensitive to the monthly simulations. (3) Parameters are nonuniformly sensitive for different goal variables, and thus, proper specification of a prior distribution of parameters may be the key factor for global optimization algorithms to obtain stable and realistic model performance.  相似文献   
110.
CHALLENGE OF URBANIZATION IN CHINAAccording to the forecast, the proportion of urbanpopulation in China will increase from about 35% todayto more than 50% in the next two decades. Due to thisprocess, huge areas of former agricultural and natural landare currently turned into build-up-areas and traffic-ways.Approximately 40-50% of this area will be developed forindustrial use. Further more, large sites occupied by oldindustry ("brownfields") will be redeveloped. Thisdevelopment of …  相似文献   
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