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   782篇
  免费   46篇
  国内免费   191篇
安全科学   54篇
废物处理   18篇
环保管理   147篇
综合类   374篇
基础理论   191篇
环境理论   1篇
污染及防治   120篇
评价与监测   59篇
社会与环境   54篇
灾害及防治   1篇
  2024年   2篇
  2023年   10篇
  2022年   20篇
  2021年   32篇
  2020年   30篇
  2019年   15篇
  2018年   23篇
  2017年   26篇
  2016年   31篇
  2015年   43篇
  2014年   50篇
  2013年   79篇
  2012年   46篇
  2011年   83篇
  2010年   56篇
  2009年   52篇
  2008年   32篇
  2007年   65篇
  2006年   61篇
  2005年   54篇
  2004年   23篇
  2003年   38篇
  2002年   16篇
  2001年   13篇
  2000年   18篇
  1999年   12篇
  1998年   17篇
  1997年   9篇
  1996年   8篇
  1995年   13篇
  1994年   6篇
  1993年   6篇
  1992年   7篇
  1991年   2篇
  1990年   2篇
  1987年   1篇
  1985年   1篇
  1984年   1篇
  1983年   1篇
  1982年   2篇
  1981年   1篇
  1979年   1篇
  1978年   2篇
  1976年   2篇
  1975年   1篇
  1973年   1篇
  1972年   1篇
  1971年   4篇
排序方式: 共有1019条查询结果,搜索用时 468 毫秒
861.
Tens of thousands of chemicals are currently marketed worldwide, but only a small number of these compounds has been measured in effluents or the environment to date. The need for screening methodologies to select candidates for environmental monitoring is therefore significant. To meet this need, the Swedish Chemicals Agency developed the Exposure Index (EI), a model for ranking emissions to a number of environmental matrices based on chemical quantity used and use pattern. Here we evaluate the EI. Data on measured concentrations of organic chemicals in sewage treatment plants, one of the recipients considered in the EI model, were compiled from the literature, and the correlation between predicted emission levels and observed concentrations was assessed by linear regression analysis. The adequacy of the parameters employed in the EI was further explored by calibration of the model to measured concentrations. The EI was found to be of limited use for ranking contaminant levels in STPs; the r2 values for the regressions between predicted and observed values ranged from 0.02 (= 0.243) to 0.14 (= 0.007) depending on the dataset. The calibrated version of the model produced only slightly better predictions although it was fitted to the experimental data. However, the model is a valuable first step in developing a high throughput screening tool for organic contaminants, and there is potential for improving the EI algorithm.  相似文献   
862.
In recent years there has been growing international interest in the assessment of doses and risks from ionising contaminants to biota. In this study the ERICA Tool, developed within the EC 6th Framework Programme, was applied to estimate incremental dose rates to biota in freshwater ecosystems in Finland mainly resulting from exposure to the Chernobyl-derived radionuclides 137Cs, 134Cs and 90Sr. Data sets consisting of measured activity concentrations in fish, aquatic plants, lake water and sediment for three selected lakes located in a region with high 137Cs deposition were applied in the assessment. The dose rates to most species studied were clearly below the screening level of 10 μGy h−1, indicating no significant impact of the Chernobyl fallout on these species. However, the possibility of higher dose rates to certain species living on or in the bottom sediment cannot be excluded based on this assessment.  相似文献   
863.
A soil-plant transfer study was performed using soil from a former uranium ore processing factory in South Bohemia. We present the results from greenhouse experiments which include estimates of the time required for phytoremediation. The accumulation of 226Ra by different plant species from a mixture of garden soil and contaminated substrate was extremely variable, ranging from 0.03 to 2.20 Bq 226Ra/g DW. We found differences in accumulation of 226Ra between plants from the same genus and between cultivars of the same plant species. The results of 226Ra accumulation showed a linear relation between concentration of 226Ra in plants and concentration of 226Ra in soil mixtures. On the basis of these results we estimated the time required for phytoremediation, but this appears to be too long for practical purposes.  相似文献   
864.
A field study has been conducted to evaluate the 226Ra bioaccumulation among aquatic plants growing in the stream/river adjoining the uranium mining and ore-processing complex at Jaduguda, India. Two types of plant group have been investigated namely free floating algal species submerged into water and plants rooted in stream & riverbed. The highest 226Ra activity concentration (9850 Bq kg−1) was found in filamentous algae growing in the residual water of tailings pond. The concentration ratios of 226Ra in filamentous algae (activity concentration of 226Ra in plant Bq kg−1 fresh weight/activity concentration of 226Ra in water Bq l−1) widely varied i.e. from 1.1 × 103 to 8.6 × 104. Other aquatic plants were also showing wide variability in the 226Ra activity concentration. The ln-transformed filamentous algae 226Ra activity concentration was significantly correlated with that of ln-transformed water concentration (r = 0.89, p < 0.001). There was no correlation between the activity concentrations of 226Ra in stream/riverbed rooted plants and the substrate. For this group, correlation between 226Ra activity concentration and Mn, Fe, Cu concentration in plants were statistically significant.  相似文献   
865.
The effect of soil properties on the toxicity of molybdenum (Mo) to four plant species was investigated. Soil organic carbon or ammonium-oxalate extractable Fe oxides were found to be the best predictors of the 50% effective dose (ED50) of Mo in different soils, explaining > 65% of the variance in ED50 for four species except for ryegrass (26-38%). Molybdenum concentrations in soil solution and consequently plant uptake were increased when soil pH was artificially raised because sorption of Mo to amorphous oxides is greatly reduced at high pH. The addition of sulphate significantly decreased Mo uptake by oilseed rape. For risk assessment, we suggest that Mo toxicity values for plants should be normalised using soil amorphous iron oxide concentrations.  相似文献   
866.
通过熏气的方法,比较了在硫氧化物混合污染气体的作用下,木本花卉(月季Rosa chinensis,杜鹃Rhododendron simsii,一品红Euphorbia pulcherrima,茉莉花Jasminum sambac),一、二年生花卉(一串红Salvia splendens,凤仙花Impatiens balsamina),宿根花卉(君子兰Clivia miniata),室内观叶植物(文竹Asparagus setacens,吊兰Chlorophytum comosum,沿阶草Ophiopogon bodinieri,朱蕉Cordyline fruticosa,吊竹梅Zebrina pendula,白斑万年青Dieffenbachia bowmannii)中13种花卉植物的叶片伤害症状及植物抗性表现,并对植物受害后的恢复情况进行了追踪观察。发现在同种污染气体的作用下,不同种类的植物表现出不同的伤害症状。植株不同叶龄的叶片对污染气体的敏感性存在一定的差异,幼龄叶不一定比中老龄叶敏感性强。当污染浓度不超过一定阈值时,花卉植物都有不同程度的恢复能力。利用“花卉植物叶片伤害评价系统”对试验植物叶片伤害症状进行了评价,依据评价结果,对试验植物进行了抗性分级。为保证对植物抗性等级划分的准确性,建议制定统一的熏气浓度标准和评价标准。  相似文献   
867.
火电厂氮氧化物控制标准、政策分析及研究   总被引:1,自引:0,他引:1  
制订污染物的排放标准及控制政策是治理环境污染的主要措施之一,世界各国针对火电厂氮氧化物(NOx)排放量分别制订了适合各国国情的控制政策及排放标准。通过对美国、欧盟及日本等世界主要发达国家及地区火电厂氮氧化物排放控制对策的分析,提出了对我国火电厂氮氧化物排放控制政策的建议。  相似文献   
868.
Abstract: The objective of this study is to evaluate the effect of estrogens on fish endocrine disruption in river water and treated wastewater. Endogenous estrogen estrone (E1), 17β‐estradiol (E2), river water, and treated wastewater were used for exposure tests on male Japanese medaka. Vitellogenin induction in male medaka was regarded as the endpoint of endocrine disruption. The effective concentrations of E1 and E2 on vitellogenin induction in medaka were evaluated by breeding medaka for 14 days in tanks with various concentrations of E1 or E2. Vitellogenin induction increased with elapse of time during exposure, with higher estrogen concentrations causing greater vitellogenin induction. According to the test results, the lowest observed effect concentrations (LOECs) of E1 and E2 were estimated to be 31.6 and 5.0 ng/l, respectively; and the E2 equivalent (EEQ) LOEC value of E1 was 5.2 ng‐E2/l, derived by multiplying the relative potency of E1 by that of E2 as estimated in this study. In continuous exposure tests using river water or treated wastewater, the estrogenic activity, an index of total estrogenic potential measured by yeast screen assay and expressed as EEQ, varied widely during the exposure tests, and significant vitellogenin induction was observed after several days of high levels of estrogenic activity in water. Vitellogenin concentration tended to significantly increase if EEQ exceeded the level of 5 ng‐E2/l. The threshold value was substantially the same as the results for E1 and E2 exposure tests of medaka. Consequently, EEQ over 5 ng‐E2/l was revealed to have the potential to cause endocrine disruption of male medaka. As estrogenic activity exceeding 5 ng‐E2/l was observed in some rivers in Japan, total estrogenic potential needs to be further decreased at wastewater treatment plants to prevent fish endocrine disruption.  相似文献   
869.
An educational project on biological monitoring of air quality was launched in 2004 to involve about 650 young students (age 6 to 16) from 21 schools of nine municipalities in Tuscany (Central Italy) in active detection of the crucial pollutant ozone with indicator sensitive tobacco seedlings. Results implied the reading of 9,300 raw biological figures and were fortified by the data captured by six photometric analysers. Under the guidance of their teachers, the students had several opportunities to practice with many basic and applied study areas and were initiated into the scientific method in a simple and absorbing manner. Curiosity and involvement were widespread; a sort of emotional and responsible relationship was developed by several pupils. Though primarily an educational exercise, the survey introduced a research element and the regional picture of air pollution that emerged has increased our knowledge of the air quality situation in the area. Biological monitoring of air quality is a powerful tool to improve the awareness and involvement in key topics of environmental education. In addition, it represents a crucial element for improving the awareness of problems and implies the active participation of citizens in the assessment of several indicators of the state of the environment. Its potential as a robust implement in landscape and urban planning is noteworthy.  相似文献   
870.
石化装置开停工及检维修过程中的泄压吹扫放空是石化企业VOCs的重要排放源项之一。分析了我国石化企业对停工及检维修的现行操作规范与《石化行业VOCs污染源排查工作指南》中对该源项核算方法参数要求的不符之处,并参照美国炼油厂有毒有害空气污染物国家排放标准的相关规定,提出了监测和操作方面的改进建议。  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