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   1939篇
  免费   21篇
  国内免费   29篇
安全科学   81篇
废物处理   135篇
环保管理   176篇
综合类   294篇
基础理论   327篇
污染及防治   638篇
评价与监测   195篇
社会与环境   132篇
灾害及防治   11篇
  2024年   2篇
  2023年   31篇
  2022年   69篇
  2021年   77篇
  2020年   37篇
  2019年   35篇
  2018年   88篇
  2017年   80篇
  2016年   103篇
  2015年   61篇
  2014年   95篇
  2013年   190篇
  2012年   135篇
  2011年   142篇
  2010年   102篇
  2009年   83篇
  2008年   120篇
  2007年   96篇
  2006年   107篇
  2005年   89篇
  2004年   62篇
  2003年   39篇
  2002年   32篇
  2001年   13篇
  2000年   6篇
  1999年   11篇
  1998年   7篇
  1997年   4篇
  1996年   5篇
  1995年   5篇
  1994年   5篇
  1993年   2篇
  1992年   2篇
  1991年   4篇
  1990年   4篇
  1988年   5篇
  1987年   2篇
  1986年   3篇
  1985年   3篇
  1984年   2篇
  1983年   2篇
  1979年   2篇
  1966年   2篇
  1962年   2篇
  1961年   2篇
  1960年   2篇
  1959年   2篇
  1953年   2篇
  1929年   1篇
  1928年   2篇
排序方式: 共有1989条查询结果,搜索用时 0 毫秒
991.
Synthesis of vitellogenin (VTG) in male fish is a widely recognized effect for estrogenic pollutants in temperate environments, while similar investigations are still lacking for Antarctic organisms. In this study, a preliminary characterization of vitellogenin gene expression was performed by RT-PCR in the key species Trematomus bernacchii sampled in different phases of reproductive cycle and food availability. Females exhibited the highest gene expression during the spawning period, but VTG mRNA was always detected also in males; a significant increase of gene expression was observed both in males and females at the end of the feeding season. These results were not fully supported by a differential exposure to phyto- or anthropogenic estrogens during the planctonic cycle; on the other side, the endocrine properties of cadmium, naturally elevated in Terra Nova Bay and increasing during algal bloom, would explain both the presence of VTG mRNA in males and the seasonal changes of gene induction. Laboratory exposures did not reveal short-term estrogenic effects of cadmium while an elevated responsiveness of T. bernacchii was observed toward a classical estrogenic receptor agonist (17beta-estradiol). Different hypotheses were considered to suggest delayed endocrine effects of cadmium, including the early interaction with other cellular detoxification systems or alterations at multiple levels of the hypothalamus-pituitary-gonad-liver axis. Although molecular mechanisms of VTG gene expression in males of T. bernacchii remain unclear, obtained results provide interesting insights on this species which should stimulate future research activities.  相似文献   
992.
The Naples's harbour is one of the largest and most important commercial and tourist port of the Mediterranean basin. It is located on the southeast coast of Italy and receives industrial and municipal wastewaters from the city of Naples. Due to its social and economic impact, a comprehensive assessment of levels and sources of contamination of bottom sediments in this area of the Mediterranean basin is essential to identify potential danger due to mobilization of contaminants produced by managing of the same sediments. In this study, superficial sediments collected from 189 sampling sites were analyzed for grain size, heavy metals (Cr, Cu, Ni, Pb, V, Zn, Co, Sn, Cd, Hg, As, Al and Fe), 16 priority polycyclic aromatic hydrocarbons (PAHs) and perylene and 38 individual polychlorinated biphenyl (PCB) congeners. Compared to the estimated local background, Cu, Zn, Pb, Cd, Sn and Hg show enrichment factors >3 and only Hg evidences a median value higher than the NOAA (effects range - median) guidelines. Principal component analysis allowed us to clearly discriminate two areas mainly affected by heavy metals contamination and influenced by different sources related to industrial, commercial and/or urban activities. Priority PAHs are predominantly represented by three-five-ring compounds with concentrations ranging between 9 and 31774 ng g(-1) and frequently higher than the NOAA ER-M index. A prevalent pyrolitic origin of PAH was assessed on the basis of the relative abundance of the different congeners and selected isomer ratios. The concentrations of PCBs, as sum of the 38 congeners, ranged from 1 to 899 ng g(-1), with a predominance of highly chlorinated (tetra- and penta-chlorobiphenyls) congeners. WHO-TEQ values, calculated for the PCDD-like PCB congeners, suggest a relatively high level of toxicity. Generally, the concentration of PAHs and PCBs were higher near the sites of intense industrial, shipping and/or commercial activities suggesting a direct influence of these sources on the pollutant distribution patterns.  相似文献   
993.
High concentration of NO 3 ? in groundwater has raised concern over possible contamination of drinking water supplies. In addition, the formation of haloacetic acids (HAAs) as by-products during disinfection with chlorine-based agents is still a relevant issue, since HAAs pose serious health hazard. In this work, we investigated the affinity of a precursor of Al-MCM-41 (a mesostructured hexagonal aluminosilicate containing the template surfactant) towards nitrate and HAAs, for its possible application in the removal of these pollutants from natural and drinking waters. Additionally, adsorption kinetics and isotherms were studied. The adsorbent was synthesized using cetyltrimethylammonium bromide as surfactant and characterized by physico?Cchemical techniques. Simulated drinking water was spiked with the EPA-regulated HAAs (monochloroacetic (MCAA), monobromoacetic (MBAA), dichloroacetic (DCAA), dibromoacetic (DBAA), and trichloroacetic (TCAA) acids) and placed in contact with the adsorbent. The effect of matrix composition was studied. Adsorption kinetic studies were performed testing three kinetics models. For the adsorption studies, three adsorption isotherm approaches have been tested to experimental data. The pollutant recoveries were evaluated by suppressed ion chromatography. The affinity of the adsorbent was TCAA = DBAA = DCAA > MBAA > MCAA with DCAA, DBAA, and TCAA completely removed. A removal as high as 77?% was achieved for 13?mg/L nitrate. The adsorption isotherms of NO 3 ? and monochloroacetic acid can be modeled by the Freundlich equation, while their adsorption kinetics follow a pseudo-second-order rate mechanism. The adsorbent exhibited high affinity towards HAAs in simulated drinking water even at relevant matrix concentrations, suggesting its potential application for water remediation technologies.  相似文献   
994.

Background, aim and scope

Water is a renewable resource and acceptable quality is important for human health, ecological and economic reasons, but human activity can cause great damage to the natural aquatic environment. Managing the water cycle in a sustainable way is the key to protect natural resources and human health. On a global level, the microbiological contamination of water sources is a major problem in connection with poverty and the United Nations Millennium Development Declaration is an important initiative to handle this problem. In terms of environmental health, persistent organic pollutants (POPs) circulate globally; as they travel long distances, they are found in remote areas far from their original source of application and can cause damage wherever they move to. On a global scale, United Nations Environmental Programme (UNEP) issued the Stockholm Convention to reduce POPs; in the European Union (EU), one intention of the Water Framework Directive (WFD) is to reach the good chemical status of waters; beside these regulations, there are other directives in support of these goals. The aim of this paper is to discuss whether the Stockholm Convention and the WFD allows meeting the targets of protection of human and environmental health, which are established in the different directives and how could we approach the targets.

Materials and methods

The aims and scopes of different directives are compiled and compared with the actual quality of water, different approaches of standard settings are compared and potential treatment options are discussed.

Results

Under the Stockholm Convention on POPs, which came into force in May 2004, governments are required to develop a National Implementation Plan (NIP) setting out how they will address their obligations under the convention and how they will take measures to eliminate or reduce the release of POPs into the environment by the use of best available techniques (BAT) and application of best environmental practices (BEP). On a European level, the WFD has been in place as the main European legislation to protect our water resources and the water environment of Europe since 2000. It requires managing river basins so that the quality and quantity of water does not affect the ecological services of any specific water body. Nevertheless, the goals of other directives as for drinking water, bathing water and urban wastewater treatment are not yet harmonised mainly concerning microbiological, priority substances and priority hazardous substances (PS/PHS) contamination. Following the detection of substances, a risk assessment with sound effect data needs to be performed also for regulatory decisions and priorisation of measures to remove emerging contaminants. Beside personal care products and industrial contaminants, faecal pollution of recreational waters is one of the major hazards facing users, although microbial contamination from other sources as well as chemical and physical aspects also affects the suitability of water for recreation. As in arid and semiarid areas, wastewater is considered for irrigation with regulatory needs of hygienic and chemical parameters—health-based targets—to avoid the contamination of crops and food. In surface waters, currently, the relationships between physical and chemical properties and the biological state of surface waters were quite well-understood to enable the management of catchments and rivers to achieve ecological quality.

Discussion

Nevertheless, more work is needed to find out the actual impact of the regulations for single chemicals and complex mixtures, in terms of environmental quality standards to achieve a ‘good chemical status’, on the good biological status. In a next step after the adoption of the list of PS/PHS substances, which also includes the POPs, the Urban Wastewater Treatment Directive (UWWTD) needs to be adjusted and existing or new treatment options (BATs) should comply with the new requirements of the different directives.

Conclusions

Relevant substances threaten human health and the environment by new effects such as CMR, endocrine-disrupting effects or neurotoxicity which are not yet considered in an adequate way by assessment methods and regulatory standards and the application of abatement technologies. The Registration, Evaluation, Authorisation and Restriction of Chemicals helps to control the sources, but WFD, the Stockholm Convention and UWWTD need to be harmonised and a rolling revision process should react on new developments. Finally, to answer the question if the Stockholm Convention and the WFD (2000/60/EC) could reach the target—I would state that they provide a very valuable frame to approach the targets, but there is still way to go to reach them on an EU level and on a global scale, also under the aspects of the Stockholm Convention and the Millennium Development Goals.

Perspectives

The compilation of the goals of different regulations and combined actions will save a lot of administrative efforts and money.
  相似文献   
995.
A three-part study was conducted to quantify the impact of landscaped vegetation on air quality in a rapidly expanding urban area in the arid southeastern United States. The study combines in situ, plant-level measurements, a spatial emissions inventory, and a photochemical box model. Maximum plant-level basal emission rates were moderate: 18.1 μgC gdw?1 h?1 (Washingtonia spp., palms) for isoprene and 9.56 μgC gdw?1 h?1 (Fraxinus velutina, Arizona ash) for monoterpenes. Sesquiterpene emission rates were low for plant species selected in this study, with no measurement exceeding 0.1 μgC gdw?1 h?1. The high ambient temperatures combined with moderate plant-level emission factors resulted in landscape emission factors that were low (250–640 μgC m?2 h?1) compared to more mesic environments (e.g., the southeastern United States). The Regional Atmospheric Chemistry Mechanism (RACM) was modified to include a new reaction pathway for ocimene. Using measured concentrations of anthropogenic hydrocarbons and other reactive air pollutants (NOx, ozone), the box model employing the RACM mechanism revealed that these modest emissions could have a significant impact on air quality. For a suburban location that was downwind of the urban core (high NOx; low anthropogenic hydrocarbons), biogenic terpenes increased time-dependent ozone production rates by a factor of 50. Our study demonstrates that low-biomass density landscapes emit sufficient biogenic terpenes to have a significant impact on regional air quality.  相似文献   
996.
Anthocyanins and tannins in ozone-fumigated guava trees   总被引:1,自引:0,他引:1  
Psidium guajava “Paluma”, a tropical tree species, is known to be an efficient ozone indicator in tropical countries. When exposed to ozone, this species displays a characteristic leaf injury identified by inter-veinal red stippling on adaxial leaf surfaces. Following 30 days of three ozone treatments consisting of carbon filtered air (CF – AOT40 = 17 ppb h), ambient non-filtered air (NF – AOT40 = 542 ppb h) and ambient non-filtered air + 40 ppb ozone (NF + O3 – AOT40 = 7802 ppb h), the amounts of residual anthocyanins and tannins present in 10 P. guajava (“Paluma”) saplings were quantified. Higher amounts of anthocyanins were found in the NF + O3 treatment (1.6%) when compared to the CF (0.97%) and NF (1.30%) (p < 0.05), and of total tannins in the NF + O3 treatment (0.16%) compared to the CF (0.14%). Condensed tannins showed the same tendency as enhanced amounts. Regression analyses using amounts of tannins and anthocyanins, AOT40 and the leaf injury index (LII), showed a correlation between the leaf injury index and quantities of anthocyanins and total tannins. These results are in accordance with the association between the incidence of red-stippled leaves and ozone polluted environments.  相似文献   
997.
Scientific literacy can be considered as a new demand of post-industrial society. It seems necessary in order to foster education for sustainability throughout students' academic careers. Universities striving to teach sustainability are being challenged to integrate a holistic perspective into a traditional undergraduate curriculum, which aims at specialization. This new integrative, inter- and transdisciplinary epistemological approach is necessary to cultivate autonomous citizenship, i.e., that each citizen be prepared to understand and participate in discussions about the complex contemporary issues posed by post-industrial society. This paper presents an epistemological framework to show the role of scientific literacy in fostering education for sustainability. We present a set of 26 collaborative concept maps (CCmaps) in order to illustrate an instance of theory becoming practice. During a required course for first-year undergraduate students (ACH 0011, Natural Sciences), climate change was presented and discussed in broad perspective by using CCmaps. We present students' CCmaps to show how they use concepts from quantitative and literacy disciplines to deal with the challenges posed by the need of achieving a sustainable development.  相似文献   
998.
Torque teno viruses (TTV) are small DNA viruses widespread among humans and pigs. The clinical significance of TTV infections in either humans or pigs is uncertain. In fact, TTV viremia is highly prevalent in patients with different pathologies, but it can also be frequently observed in healthy subjects. Virus infection in pigs is considered a putative cofactor in several diseases; despite being detected frequently in healthy animals, its role still remains unknown. The present study aimed to investigate the presence of Torque teno sus virus (TTSuV) in 62 bile samples collected from pigs at slaughterhouse and in 36 fresh pork liver sausages bought at point of sale. Quantitative Real-Time PCR, confirmed that 19.4 and 58.3 % of bile and sausage samples tested positive for TTSuV, respectively. The mean viral load was established as 5.6 × 104 GE/µl for bile and 7.16 × 103 GE/g for sausages. TTSuV nucleotide sequence analysis confirmed a wide heterogeneity among the circulating TTSuV strains, which included both TTSuV1 and TTSuV2.  相似文献   
999.
1000.
The objective of this study was to evaluate the effect of heat treatment on poultry litter with different levels of reutilisation for potential generation of biogas in experimental biodigesters. Chicken litter used was obtained from two small-scale poultry houses where 14 birds m?2 were housed for a period of 42 days per cycle. Litter from aviary 1 received no heat treatment while each batch of litter produced from aviary 2 underwent a fermentation process. For each batch taken, two biodigesters were set for each aviary, with hydraulic retention time of 35 days. The efficiency of the biodigestion process was evaluated by biogas production in relation to total solids (TS) added, as well as the potential for power generation. Quantified volumes ranged from 8.9 to 41.1 L of biogas for aviary 1, and 6.7 to 33.9 L of biogas for aviary 2, with the sixth bed reused from both aviaries registering the largest biogas potential. Average potential biogas in m3 kg?1 of TS added were 0.022 to 0.034 for aviary 1 and 0.015 to 0.022 for aviary 2. Energy values ??of biogas produced were calculated based on calorific value and ranged from 0.06 to 0.33 kWh for chicken litter without fermentation and from 0.05 to 0.27 kWh for chicken litter with fermentation. It was concluded that the re-use of poultry litter resulted in an increase in biogas production, and the use of fermentation in the microbiological treatment of poultry litter seems to have negatively influenced production of biogas.  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