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991.
Spatial distribution of arsenic in the intertidal sediments of River Scheldt, Belgium 总被引:1,自引:0,他引:1
A study was carried out to assess the spatial distribution of arsenic in the intertidal sediments of the River Scheldt in Belgium. Sediment samples were collected from different locations along the River Scheldt up to 100 cm depth and analysed for the major physicochemical properties. The study reveals that the arsenic contents in the sediment samples vary in a wide range, from 2.3 to 140.2 mg kg(-1) dry weight. Moreover, the arsenic concentrations are generally below the background concentrations and remediation thresholds of arsenic in Flanders, Belgium. The occurrence of arsenic is found closely related to some physicochemical properties of the sediments. Arsenic has a strong positive correlation with organic matter and clay contents. On the contrary, a negative correlation exists between arsenic, sand and pH. It is recommended to develop and use organic matter control practices for lowering further accumulation of arsenic within the sediments. 相似文献
992.
A~2/O工艺重新启动试验的污泥活性恢复研究 总被引:1,自引:0,他引:1
以处理实际城市污水的小试规模A2/O工艺为研究对象,在处理工艺稳定运行的基础上关停装置60 d,进行了"饥饿"期内不同关停模式下系统重新启动后污泥活性恢复的研究.结果表明,循环模式、厌氧模式和微曝模式3种不同关停模式下,系统重启第4天,污泥硝化性能及反硝化性能基本恢复甚至超过关停前水平,而脱碳性能和除磷性能的恢复速度则较缓慢,重新启动后系统呈现较好的反硝化除磷能力;重启第12天后3种关停模式出水水质良好,基本满足<城镇污水处理厂污染物排放标准>(GB 18918-2002)一级B标准.不同关停模式下,系统污泥活性恢复速率及出水水质对比显示,污水处理厂故障检修期间将搅拌、曝气等动力设备完全关闭的厌氧模式下系统污泥活性恢复较快,而且能耗最低. 相似文献
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Yonghong Hao Yuen Zhu Ying Zhao Wei Wang Xin Du Tian‐Chyi J. Yeh 《Journal of the American Water Resources Association》2009,45(5):1228-1237
Abstract: One of the largest karst springs in North China, the Jinci Springs, dried up and has remained dry since 1994. We develop a correlation analysis with time‐lag and a regression analysis with time‐lag to study the relation between spring flow and precipitation. This allows us to obtain a better understanding of karst hydrological processes by differentiating the contribution of variation in precipitation from anthropogenic impacts on the dry‐up of Jinci Springs. We divided the karstic hydrological processes into two phases: pre‐1961 and post‐1961. In the first phase (i.e., 1954‐1960) the groundwater recharge was affected by precipitation alone, and in the second phase (i.e., 1961‐1994) the groundwater recharge was influenced by both precipitation and human activities. Using precipitation and groundwater recharge data in the first phase, we set up a groundwater recharge model with time‐lags. By running the time‐lags model, we acquired the groundwater recharge likely to occur under the sole effect of precipitation in the second phase. Using a water‐balance calculation, we conclude that the groundwater recharge exhibited statistical stationarity, and the Jinci Springs dry‐up was the result of anthropogenic activities. At least three specific types of anthropogenic activities contributed to the drying‐up of Jinci Springs: (1) groundwater pumping accounts for 51%, (2) the dewatering from coal mining accounts for 33%, (3) and dam‐building 14%. The drying‐up of Jinci Springs meant that the groundwater drained from the aquifer’s fractures, and subsequently changed the structure of the karst aquifer. Although groundwater exploitation has been reduced, the flow at Jinci Springs has not reoccurred. 相似文献
997.
E. Osei B. Du A. Bekele L. Hauck A. Saleh A. Tanter 《Journal of the American Water Resources Association》2008,44(3):562-576
Abstract: An integrated economic and environmental modeling system was developed for evaluating agro‐environmental policies and practices implemented on large scales. The modeling system, the Comprehensive Economic and Environmental Optimization Tool‐Macro Modeling System (CEEOT‐MMS), integrates the Farm‐level Economic Model (FEM) and the Agricultural Policy Environmental eXtender (APEX) model, as well as national databases and clustering and aggregation algorithms. Using micro simulations of statistically derived representative farms and subsequent aggregation of farm‐level results, a wide range of agricultural best management practices can be investigated within CEEOT‐MMS. In the present study, CEEOT‐MMS was used to evaluate the economic and water quality impacts of nitrogen (N) and phosphorus (P) based manure application rates when implemented on all animal feeding operations in the State of Texas. Results of the study indicate that edge‐of‐field total P losses can be reduced by about 0.8 kg/ha/year or 14% when manure applications are calibrated to supply all of the recommended crop P requirements from manure total P sources only, when compared to manure applications at the recommended crop N agronomic rate. Corresponding economic impacts are projected to average a US$4,800 annual cost increase per farm. Results are also presented by ecological subregion, farm type, and farm size categories. 相似文献
998.
Application of biological safety index in two Japanese watersheds using a bioassay battery 总被引:1,自引:0,他引:1
In order to integratedly evaluate the biological safety as a water quality index, an assessment method based on three toxicity tests (algae growth inhibition, daphnia immobilization and larval fish toxicity) was developed. In this study, the developed method was used to screen, evaluate and rank the biological safety of small rivers near agricultural, industrial and residential areas. Twenty-seven representative water samples were collected from the Kaname River watershed and the Hinata River watershed in Kanagawa Prefecture, Japan. The results indicated that (1) the biological safety of water from the Hinata River ranked much higher than those from the Suzu River and the Shibuta River due to less human activities, (2) the biological safety from outlets of paddy fields ranked much worse than those from point source discharges of toxic pollutants, (3) the use of pesticides significantly affected the water quality of nearby small rivers and ditches during the pesticide application season, (4) the effects of different kinds of pesticides could successfully be classified using one toxicity test component of the bioassay battery, and (5) there was no significant quantitative relationship between the toxicity and dissolved organic carbon (DOC) for the studied water samples. The toxicities of water samples in this study were in agreement with the concentrations of pesticides determined with chemical methods by other researchers, which demonstrated that the developed assessment method was reliable to screen site contaminated with organic chemicals for priority management. 相似文献
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山东省生态环境承载力评价指标体系探讨 总被引:3,自引:0,他引:3
将生态环境承载力划分为资源承载力、环境承载力、循环经济水平和经济社会支持能力四部分,结合山东省生态环境现状,根据指标体系建立的原则,选用了57项评价指标,分层次构建了山东省生态环境承载力评价指标体系.其中,资源承载力选用生物资源、水资源等5大类共10项指标;环境承载力选用地表水、近岸海域等5大类共9项指标;循环经济水平选用资源产出水平、资源消耗水平等4大类共18项指标;经济社会支持能力选用人口数量与素质水平、经济发展水平等7大类共20项指标. 相似文献