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   582篇
  免费   73篇
  国内免费   326篇
安全科学   24篇
废物处理   56篇
环保管理   41篇
综合类   512篇
基础理论   219篇
污染及防治   89篇
评价与监测   29篇
社会与环境   11篇
  2023年   10篇
  2022年   13篇
  2021年   30篇
  2020年   14篇
  2019年   29篇
  2018年   20篇
  2017年   29篇
  2016年   19篇
  2015年   33篇
  2014年   56篇
  2013年   93篇
  2012年   54篇
  2011年   53篇
  2010年   33篇
  2009年   42篇
  2008年   37篇
  2007年   52篇
  2006年   70篇
  2005年   28篇
  2004年   32篇
  2003年   38篇
  2002年   32篇
  2001年   35篇
  2000年   21篇
  1999年   8篇
  1998年   22篇
  1997年   5篇
  1996年   16篇
  1995年   11篇
  1994年   9篇
  1993年   6篇
  1992年   2篇
  1991年   3篇
  1990年   5篇
  1989年   2篇
  1988年   6篇
  1987年   2篇
  1986年   2篇
  1985年   1篇
  1984年   1篇
  1982年   1篇
  1981年   2篇
  1979年   1篇
  1977年   1篇
  1975年   1篇
  1971年   1篇
排序方式: 共有981条查询结果,搜索用时 312 毫秒
131.
A total of 200 Jordanian children were classified into two groups: 100 Fe replete and 100 Fe deficient with ages ranging between 3.0 and 12.0 years (6.9 ± 2.7 years). All participants were chosen according to proper selection criteria followed by the sample collection: the samples were analyzed for hemoglobin and red blood cells; ferritin, an immunoassays-based instrument; and levels of Pb, Cu, and Zn. There were no significant differences between genders regarding Fe-deficiency (p = 0.57 and χ2 = 0.33), with a significant association of younger individuals (3.0–9.1 years) with Fe-deficiency (p < 0.05 and χ2 = 22.7).

In addition, there is a significant positive correlation between Fe-deficiency with blood levels of Pb, Cu, and Zn (p < 0.05), (r = 0.43, 0.35, and 0.42, respectively) as compared to control group, this findings supported, by comparing the levels of the examined metals in both groups, in individuals whom close to heavy metals source (highway traffic or oil gas station), and found that the mean of the heavy metals level in close Fe-deficient group higher than in close Fe-replete group.  相似文献   
132.
The hypotheses on the de novo syntheses of polychlorinated dibenzofurans (PCDFs) and polychlorinated dibenzo‐p‐dioxins (PCDDs), based on known literature, are presented. Polychlorinated benzenes and polychlorinated phenols are probably key intermediates.

In the present article, hypotheses that may account for the presence of polychlorinated dibenzofurans (PCDFs) and dibenzo‐p‐dioxins (PCDDs) in the effluents from municipal and industrial incinerators are put forward. These hypotheses are based on the previously surveyed literature (Ref. 203–206) and experimental results on laboratory scale and thermodynamic calculations are considered. The interconnections of various reaction steps are speculative and no technological information was added to account for conditions in real incinerators. Conclusion of the discussions on the related subject matter, presented in the Parts I‐IV (Ref. 203–206), are also described in this paper.  相似文献   
133.
Bioavailabilities of metals in sediment to aquatic organisms depend on the strength of metal bonding to particulates. The accumulation tests of Cu and Cd in carp and in snails have been studied in vitro with the solution containing semisynthetic sediment samples in which the contents of various speciation of metal in sediment have been extended. For carp, the accumulation of Cu and Cd is related to the concentration of dissolved metal which in turn is affected by the distributions of speciations in sediment under given environmental conditions. It is another pattern for snails, various speciations of metal in sediment can contribute indirectly to metal accumulation. The contribution ratio, or relative importance of various speciations of metal in sediment can be expressed by multiple linear regression formulas. The contribution of ion‐exchangable speciation and coprecipition with carbonate speciation is 105 times larger than that of residue speciation in sediment.  相似文献   
134.
以壳聚糖(CTS)、聚乙烯吡咯烷酮(PVP)、活性炭(C)为基材,Cu(Ⅱ)为印迹离子,制备了CTS/PVP共混印迹球[Cu(Ⅱ)-IICP]和CTS/PVP/C共混印迹球[Cu(Ⅱ)-IICPC].以Cu(Ⅱ)的吸附量作为评价指标,对两种共混印迹球的制备条件进行了优化.研究结果表明,当CTS/PVP的质量比为6∶4,活性炭质量分数为0.6%,Cu(Ⅱ)模板剂质量分数为0.05%,所制备的两种共混印迹球吸附性能较佳,且对Cu(Ⅱ)有较好的选择吸附性.物理吸附分析结果表明,与未印迹相比印迹材料的比表面积明显增大.FTIR谱图分析,Cu(Ⅱ)模板主要与CTS和PVP中的—NH2和—OH发生了配位作用.XRD谱图分析结果表明,CTS与PVP、C、Cu(Ⅱ)之间发生了相互作用,改变了CTS原有的晶体结构,使其结晶度降低.  相似文献   
135.
Metallurgical production is the largest polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) emission source in China. However, PCDD/F monitoring and research are rarely conducted on primary metallurgical production. In this study, a demonstration primary copper smelter in China was selected to investigate PCDD/F characteristics and control. Samples were collected from major PCDD/F release points in the smelter process (fly ashes and waste water sludge). Specific analysis of PCDD/F congeners was carried out using a high resolution gas chromatography/high resolution mass spectrometry method. The results showed that PCDD/Fs might be unintentionally produced in the primary copper smelter processes, with sample concentrations of 180–6110 pg/g dry wt; highly chlorinated PCDD/F homologues were predominant. The toxicity of all the samples was calculated to be 120 pg WHO TEQ/g, fly ashes from the refining process furnaces air pollution control device and sludge were hazardous waste with higher PCDD/F toxicity. Both precursor formation and de novo synthesis were found to contribute to PCDD/F formation in the smelter process. PCDD/F characteristics and formation were compared with reported secondary copper smelters. Life-cycle control of PCDD/F was proposed for retrofitting of this smelter and for similar plants in China's primary copper production sector, including control at the PCDD/F formation, removal and disposal stages.  相似文献   
136.
The overall effect of the number of boats on the copper (Cu) levels in the water column and sediment, along with their spatial variability within Shelter Island Yacht Basin (SIYB), San Diego Bay, California was examined. We identified a horizontal gradient of increasing dissolved Cu and Cu in sediment from outside to the head of SIYB which was coincident with the increasing number of boats. Spatial models of Cu distribution in water and sediment indicated the presence of ‘hotspots’ of Cu concentration. From outside to the head of SIYB, dissolved Cu ranged from 1.3 μ g L?1 to 14.6 μ g L?1 in surface water, and 2.0 μ g L?1 to 10.2 μ g L?1 in bottom water. Cu in sediment exceeded the Effect Range Low of 34 mg kg?1 (i.e. where adverse effects to fauna may occur), with a peak concentration of 442 mg kg?1 at the head of the basin. Free Cu++ in surface water was several orders of magnitude higher than in sediment porewater. High-resolution data of Cu species together with probability maps presented in this paper will allow managers to easily visualise and localise areas of impaired quality and to prioritise which areas should be targeted to improve Cu-related conditions.  相似文献   
137.
The aim of this study was to assess the toxic impact of copper on postlarvae (PL) of the penaeid shrimp Penaeus indicus. Tolerance, growth, oxygen consumption and metal accumulation were investigated in these PL on exposure to copper. Tolerance studies were conducted for 96 h to assess the tolerance limits of P. indicus PL exposed to different concentrations of copper using static renewal bioassay tests. Using the Probit method, the regression equation was calculated as Y=0.4899+2.3562 X, with a correlation coefficient of 0.9707. The 96 h LC50 was 0.8204 ppm. The effect of sublethal (one-fifth of 96 h LC50) copper on PL for short- and long-term exposures revealed a significant (p<0.05) decrease in the rate of oxygen consumption, metabolic rate, mean length, wet and dry weight of the exposed PL over their respective controls which can be attributed to a gradual and time-dependent accumulation of the metal, as noticed in the exposed PL through accumulation studies. Overall, the data suggest that on chronic exposure even sublethal concentrations of copper can reduce the metabolic rate and growth in P. indicus PL. This is perhaps the first attempt to use the wild P. indicus PL as a bioindicator of copper toxicity.  相似文献   
138.
Phosphogypsum (PG), a solid by-product of phosphoric acid production, contains radionuclides and trace metals in concentrations which may pose a potential hazard to human health and the environment. to investigate the possibility of bioaccumulation of radium and six heavy metals over time when aquatic organisms experience both trophic and environmental exposure to PG, we designed a laboratory experiment representing three levels of an aquatic food chain. During the 135 day experiment, a meiobenthic copepod species (Amphiascoides atopus) was cultured in the presence of PG. the copepods were subsequently fed to grass shrimp (Palaemonetes vulgaris and P. pugio) which were in turn fed to gulf killifish (Fundulus grandis); both the grass shrimp and the killifish also experienced an environmental PG exposure. Other than elevated radium levels in the experimental grass shrimp, the experiment demonstrated little effect of environmental or trophic exposure to PG on microinvertebrates, macroinvertebrates, or fishes that could be attributed to PG. in all cases where increased concentrations were indicated within the experimental group, roughly equivalent increases in metal concentrations also occurred in the control group.  相似文献   
139.
Secondary copper production is one of the key polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) emission sources in China, but research and data on this issue are rare. In 2004, when the Stockholm Convention entered into force in China, PCDD/Fs emissions from secondary copper production contributed to 32.2% of the total release. In this paper, PCDD/Fs emission dynamics from secondary copper industry were discussed and cumulative risks were characterized. From 2004 to 2009, industrial policies played an indirect role in PCDD/Fs reduction, but its effects are still limited. The Yangtze River Delta, Pearl River Delta and central regions were among the top three of dioxin emissions from secondary copper production in China. Shanghai, Shandong, Zhejiang, and Jiangxi had comparatively higher accumulated risk and were recommended as the priority regions for promoting PCDD/Fs emission control in China. From 2009 to 2015, the PCDD/Fs emission dynamics in the secondary copper industry were presented through simulation. PCDD/Fs emission equations were established, resulting in the recommendation of control technology conversion rate at 30% for small scale smelters and 51%–57% for large and medium-sized enterprises in 2015. In conclusion, both indirect policy and direct control technology retrofitting should be integrated for more effective PCDD/Fs emission reduction in secondary copper industry.  相似文献   
140.
选取3种钝化材料(赤泥、硼泥、钙镁磷肥),通过盆栽试验,观测了在不同铜污染水平红壤上,3种钝化材料对小油菜(Brassica campestris,L var Conmunis)吸收铜的影响。结果表明:在铜污染红壤上,3种钝化材料降低土壤EDTA提取态铜含量的效果显著。其中,在高铜污染水平红壤上,施用高量赤泥、硼泥处理降低效果最为明显,较污染对照降低了41.48%、44.44%。在低铜污染水平红壤上,施用高量赤泥处理降低效果最为明显,较对照处理降低了35.83%。施用3种钝化材料均能促进小油菜生长,增加小油菜的生物量,降低小油菜对铜的吸收量。其中,低铜污染水平红壤上,施用高量赤泥、高量硼泥与硼泥-赤泥联合施用处理降低铜含量的效果最为明显,与污染对照相比,小油菜铜含量分别降低82.64%,72.71%,85.14%;在高铜污染水平红壤上,施用高量赤泥与硼泥、赤泥联合施用处理降低小油菜铜含量的效果最为明显,小油菜铜含量分别为36.37,36.32 mg.kg^-1。结果表明,用量为45 000 kg.hm^-2的赤泥是最佳的功能钝化材料。  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