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   2349篇
  免费   23篇
  国内免费   6篇
安全科学   65篇
废物处理   177篇
环保管理   155篇
综合类   276篇
基础理论   484篇
环境理论   1篇
污染及防治   818篇
评价与监测   236篇
社会与环境   162篇
灾害及防治   4篇
  2023年   26篇
  2022年   68篇
  2021年   77篇
  2020年   33篇
  2019年   40篇
  2018年   78篇
  2017年   83篇
  2016年   122篇
  2015年   75篇
  2014年   132篇
  2013年   228篇
  2012年   135篇
  2011年   178篇
  2010年   100篇
  2009年   71篇
  2008年   149篇
  2007年   161篇
  2006年   112篇
  2005年   92篇
  2004年   63篇
  2003年   56篇
  2002年   62篇
  2001年   37篇
  2000年   21篇
  1999年   19篇
  1998年   6篇
  1997年   9篇
  1996年   6篇
  1995年   12篇
  1994年   7篇
  1993年   12篇
  1992年   3篇
  1991年   7篇
  1990年   10篇
  1989年   3篇
  1988年   6篇
  1983年   3篇
  1975年   2篇
  1967年   4篇
  1966年   2篇
  1964年   8篇
  1963年   7篇
  1962年   7篇
  1960年   5篇
  1959年   2篇
  1958年   8篇
  1957年   3篇
  1956年   4篇
  1955年   2篇
  1943年   2篇
排序方式: 共有2378条查询结果,搜索用时 15 毫秒
971.
Urban green/blue spaces are put under pressure as urban areas grow, develop and evolve. It is increasingly recognized, however, that green/blue spaces provide important ecosystem services, stimulate higher real estate prices and prevent flooding problems. This paper aims to assess and compare the socio-economic impacts of potential green/blue space, urban residential and road infrastructure development scenarios in the Lyon Confluence project area (France), using the Sustainable Urbanizing Landscape Development (SULD) hedonic pricing simulation model. Results show four major tendencies regarding the value-added of green/blue spaces in urban landscapes: (1) cities become more compact; (2) population densities increase; (3) real estate values rise; and (4) demographic distribution patterns change. The magnitude of these impacts depends, however, on the quality and size of the intervention, the social classes attracted to the intervention area and on the location of the intervention relative to existing residential areas, urban centres, road infrastructure and environmental amenities.  相似文献   
972.
The objective of this study was to evaluate whether the oxidative stress caused by aluminum (Al) toxicity is an early symptom that can trigger root growth inhibition in Macaca (Al-sensitive) and SMIC148-A (Al-tolerant) potato clones. Plantlets were grown in a nutrient solution (pH 4.00) with 0, 100 and 200 mg Al L−1. At 24, 72, 120 and 168 h after Al addition, root length and biochemical parameters were determined. Regardless of exposure time, root length of the Macaca clone was significantly lower at 200 mg Al L−1. For the SMIC148-A clone, root length did not decrease with any Al treatments. Al supply caused lipid peroxidation only in Macaca, in both roots (at 24, 72, 120 and 168 h) and shoot (at 120 and 168 h). In roots of the Macaca, catalase (CAT) and ascorbate peroxidase (APX) activity decreased at 72 and 120 h, and at 24, 72 and 120 h, respectively. At 168 h, both activities increased upon addition of Al. In roots of the SMIC148-A, CAT activity increased at 72 and 168 h, whereas APX activity decreased at 72 h and increased at 24, 12 and 168 h. The Macaca showed lower root non-protein thiol group (NPSH) concentration at 200 mg Al L−1 in all evaluations, but the SMIC148-A either did not demonstrate any alterations at 24 and 72 h or presented higher levels at 120 h. This pattern was also observed in root ascorbic acid (AsA) concentration at 24 and 120 h. The cellular redox status of these potato clones seems to be affected by Al. Therefore, oxidative stress may be an important mechanism for Al toxicity, mainly in the Al-sensitive Macaca clone.  相似文献   
973.
The Institute of Environmental Engineering at the University of Pannonia has undertaken the challenge to develop an online environmental information system. This system is able to receive and process the collected environmental data via Internet. The authors have attached importance to the presentation of the data and have included other comprehensible information for laymen as well in order to work out visualisation techniques that are expressive and attract attention for environmental questions through the developed information system. The ways of visualizing physical and chemical parameters of surface water and the effects of motorway construction were examined.  相似文献   
974.
Assessing the sustainability of complex development processes requires multi-causal and integrated analyses. We develop a system-based methodology, rooted in interdisciplinary discussion and consensus building between 15 experts, to construct a multi-causal diagram which examines the sustainability of the Argentine Pampas′ process of agriculturization. The resulting diagram includes 25 factors and provides a big-picture of the multiple dimensions and interrelations affecting sustainability. According to this examination, the increasing concentration of production and the incorporation of technological innovations, triggered by economic and institutional factors, are the cause of environmental distresses and social changes, whose consequences for sustainability are still highly disputed. Nevertheless, the symptoms of both environmental and social unsustainability are more evident in the case of the extra-Pampean regions than in the Pampas. This suggests that the Pampean agriculture model should not be transferred to these regions without substantial modifications. The experts did not reach consensus on whether the agriculturization process is overall sustainable or unsustainable. Lack of consensus revolved mainly around opposing perspectives regarding the significance of the threats to environmental sustainability. The magnitude of socio-distributive unbalance and loss of rural jobs were also contentious. Yet, the paper shows how the exercise of building a joint causal diagram was undoubtedly helpful for linking piece-meal disciplinary facts, brought in from all fronts, into a comprehensive and coherent picture. Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue.  相似文献   
975.

Background, aim, and scope  

Polycyclic aromatic hydrocarbons (PAHs) are often found in oily wastewaters. Their presence is usually the result of human activities and has a negative effect on the environment. One important step in addressing this problem is to evaluate the effectiveness of PAH removal by biological processes since these are the most cost-effective treatments known today. Many techniques are presently available for PAH determination in wastewaters. Solid phase microextracion (SPME) is known to be one of the most effective techniques for this purpose. When analyzing complex matrices with substances such as natural organic matter (NOM) and non-aqueous phase liquids (NAPL), it is important to differentiate the free dissolved PAH from matrix-bonded PAH. PAHs associated with the bonded fraction are less susceptible to biological treatment. The present study concerns the development of a simple and suitable methodology for the determination of the freely dissolved and the total fraction of PAHs present in oily wastewaters. The methodology was then applied to an oily wastewater from a fuel station retention basin.  相似文献   
976.
The objective of this work was to study the technological feasibility of treating wastewater from a personal care industry (PCI-WW) in a mechanically stirred anaerobic sequencing batch biofilm reactor (AnSBBR) containing immobilized biomass on polyurethane foam. An assessment was made on how system efficiency and stability would be affected by: increasing organic load; supplementation of nutrients and alkalinity; and different feed strategies. The AnSBBR operated with 8-h cycles, stirring speed of 400 rpm, temperature of 30 °C, and treated with 2.0 L wastewater per cycle. First the efficiency and stability of the AnSBBR were studied when submitted to an organic loading rate (OLR) of 3.1–9.4 gCOD/(L d), and when the PCI-WW was supplemented with nutrients (sucrose, urea, trace metals) and alkalinity. The AnSBBR was shown to be robust and presented stability and removal efficiency exceeding 90%. At an OLR of 12.0 gCOD/(L d) efficiency became difficult to maintain due to the presence of commercial cleansers and disinfectants in the wastewater lots. In a subsequent stage the AnSBBR treated the wastewater supplemented with alkalinity, but with no nutrients at varying feed strategies and maintaining an OLR of approximately 9.0 gCOD/(L d). The first strategy consists of feeding 2.0 L of the influent batchwise [OLR of 9.4 gCOD/(L d)]. In the second 1.0 L of influent was fed-batchwise and an additional 1.0 L was fed fed-batchwise [OLR of 9.2 gCOD/(L d)], i.e., in relation to the first strategy the feed volume was maintained but supplied in different periods. In the third strategy 1.0 L of treated effluent was maintained in the reactor and 1.0 L of influent was fed fed-batchwise [OLR of 9.0 gCOD/(L d)], i.e., in relation to the first strategy the feed volume was different but the feed period was the same and the OLR was maintained by increasing the influent concentration. Comparison of the first and second strategies revealed that organic matter removal efficiency was unaffected (exceeding 90%). The third strategy resulted in a reduction in average removal efficiency from 91 to 83% when compared to the first one. A kinetic study resulted in first order kinetic parameters ranges from 0.42 to 1.46 h−1 at OLRs from 3.1 to 12.0 gCOD/(L d), respectively, and the second feed strategy [OLR of 9.2 gCOD/(L d)] was shown to be the most favorable.  相似文献   
977.
A simple method by first derivative spectrophotometry is proposed for the simultaneous determination of o-nitrophenol and p-nitrophenol. The analytes were separated from samples by liquid-liquid extraction (pH = 7.4) as tetrabutylammonium ion pairs into the 1,2-dichloroethane organic phase and subsequently the extracts were evaluated directly by derivative spectrophotometry. Simultaneous determination of both analytes could be carried out using the zero-crossing and the graphical methods for o-nitrophenol and p-nitrophenol, respectively. The determination ranges were found to be between 0.115 to 3.00 ppm and 0.130 to 3.00 ppm for o-nitrophenol and p-nitrophenol, respectively. The relative standard deviations were in all instances less than 2.0%. The proposed method was applied to the determination of these compounds in fruit juices.  相似文献   
978.
MtDNA analyses were employed to examine the species identification of three preserved museum sturgeon specimens from the River Guadalquivir, two of which were originally described as Acipenser sturio L., 1758 by Hernando (1975; Doñana, Acta Vertd 2: 263–264). Later the same two specimens were identified as A. naccarii Bonaparte, 1836 by Garrido-Ramos et?al. (1997; Mar Biol 129: 33–39) on the basis of morphometric and nuclear DNA analyses. Three different laboratories using independent techniques were unsuccessful in extracting authentic DNA from tissue samples from the three specimens and in obtaining any verifiable PCR product. We cannot confirm the previous molecular identification of two of these specimens by Garrido-Ramos et?al. as A. naccarii. We suggest that these specimens are indeed A. sturio.  相似文献   
979.
The concentrations of organic carbon (Corg), inorganic carbon (Cinorg), organic nitrogen (Norg) and total aromatic (AromT) were determined in 25 samples of bottom sediments from the Lake Valencia, Venezuela, as a contribution to the knowledge about pollution by organic compounds in tropical lakes. Results demonstrate that the Corg and Norg concentrations do not show the pollution indexes by themselves. This is a consequence of the masking effect of naturally derived organic matter from the decay of algae and organisms in the water column and terrestrial plants, which are transported to the lake. Nevertheless, the AromT concentrations and the normalised AromT (normalized to organic carbon) make it possible to detect organic matter of anthropogenic origin, in the AromT levels are about nine times higher than those natural. The variation in the band intensity of the IRFT spectra for some functional groups present in the saturate and aromatic hydrocarbon fractions gives an indication of anthropogenic contribution for some zones of the lake. With the 1H NMR spectra it was not possible to differentiate a natural source from an anthropogenic one in the lake. Naturally occurring organic compounds (eicosane, pentacosane, and hexacosane) were detected with GC technique in the saturated hydrocarbon fraction. The presence of an unresolved complex mixture (UCM) in the GC chromatograms indicates pollution by branched and cyclic hydrocarbons. These compounds are probably produced by the incomplete combustion of oil products. Potentially toxic organic compounds such as anthracene, phenanthrene and chrysene were found in the aromatic hydrocarbon fraction, which despite presenting low concentrations (ppb order) accumulate in the lake sediments along with the natural source organic matter. The main access paths of organic pollutants to the lake are the rivers which cross the two urban and industrial areas (Maracay and Valencia cities). The mixture of polluted sediments with bottom natural sediments and the autochthonous contribution of organic matter mitigate the pollution levels progressively towards the center of the lake.  相似文献   
980.
The objective of this study was to determine the main patterns and factors influencing food transition in riverine people in the Brazilian Amazon. Through interviews with a semi-structured questionnaire, we inferred their food habits and provide information about general demographic, socioeconomic, resource use and environmental context. Data from the questionnaires were categorized and analyzed using a logistic regression model to assess the relative influence of socioeconomic and environment factors on the local diet. Based on a logistic regression data analysis, it was found a greater consumption of processed food significantly associated with multiple factors such as market participation, sex (female and male), government aid to forest conservation and environment context (upland and wetland). Although the local diet is composed mainly of local resources such as fish and cassava flour, increasing incomes due to direct government subsidy programs and marketing of cassava flour have influenced these local practices and habits. Through the analysis of factors influencing food transition, it was possible to evaluate those having the greatest effect on this Amazon region and propose an alternative method to subsidy food policy grounded in local opinion surveys.  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