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51.
Javierre C Clavería I Ponz L Aísa J Fernández A 《Waste management (New York, N.Y.)》2007,27(5):656-663
The amount of polymer material wasted during thermoplastic injection moulding is very high. It comes from both the feed system of the part, and parts necessary to set up the mould, as well as the scrap generated along the process due to quality problems. The residues are managed through polymer recycling that allows reuse of the materials in the manufacturing injection process. Recycling mills convert the parts into small pieces that are used as feed material for injection, by mixing the recycled feedstock in different percentages with raw material. This mixture of both raw and recycled material modifies material properties according to the percentage of recycled material introduced. Some of the properties affected by this modification are those related to rheologic behaviour, which strongly conditions the future injection moulding process. This paper analyzes the rheologic behaviour of material with different percentages of recycled material by means of a capillary rheometer, and evaluates the influence of the corresponding viscosity curves obtained on the injection moulding process, where small variations of parameters related to rheological behaviour, such as pressure or clamping force, can be critical to the viability and cost of the parts manufactured by injection moulding. 相似文献
52.
53.
Adel?R.?A.?Usman Mahtab?Ahmad Mohamed?El-Mahrouky Abdulrasoul?Al-Omran Yong?Sik?Ok Abdelazeem?Sh.?Sallam Ahmed?H.?El-Naggar Mohammad?I.?Al-WabelEmail author 《Environmental geochemistry and health》2016,38(2):511-521
Biochar has emerged as a universal sorbent for the removal of contaminants from water and soil. However, its efficiency is lower than that of commercially available sorbents. Engineering biochar by chemical modification may improve its sorption efficiency. In this study, conocarpus green waste was chemically modified with magnesium and iron oxides and then subjected to thermal pyrolysis to produce biochar. These chemically modified biochars were tested for NO3 removal efficiency from aqueous solutions in batch sorption isothermal and kinetic experiments. The results revealed that MgO-biochar outperformed other biochars with a maximum NO3 sorption capacity of 45.36 mmol kg?1 predicted by the Langmuir sorption model. The kinetics data were well described by the Type 1 pseudo-second-order model, indicating chemisorption as the dominating mechanism of NO3 sorption onto biochars. Greater efficiency of MgO-biochar was related to its high specific surface area (391.8 m2 g?1) and formation of strong ionic complexes with NO3. At an initial pH of 2, more than 89 % NO3 removal efficiency was observed for all of the biochars. We conclude that chemical modification can alter the surface chemistry of biochar, thereby leading to enhanced sorption capacity compared with simple biochar. 相似文献
54.
Hana Měšťánková Gilles Mailhot Jaromír Jirkovský Josef Krýsa Michèle Bolte 《Environmental Chemistry Letters》2009,7(2):127-132
Photodegradation kinetics of Monuron (3-(4-chlorophenyl)-1,1-dimethylurea) in photoreactor with immobilized and suspended
TiO2 photocatalyst were studied. The effect of addition of ferric or ferrous perchlorate was investigated. Whatever the concentration
of Fe(III/II) added there is no significant negative effect on the photodegradation rate of pollutants. On the contrary, depending
on speciation and concentration of iron salts, slight or marked acceleration of the photodegradation kinetics was observed.
This positive influence was more pronounced in the case of TiO2 suspensions than for TiO2 layers. Fe(III) was generally more effective than Fe(II). 相似文献
55.
Marina M. S. Cabral Pinto A. Paula Marinho-Reis Agostinho Almeida Carlos M. Ordens Maria M. V. G. Silva Sandra Freitas Mário R. Simões Paula I. Moreira Pedro A. Dinis M. Luísa Diniz Eduardo A. Ferreira da Silva M. Teresa Condesso de Melo 《Environmental geochemistry and health》2018,40(5):1767-1784
New lines of evidence suggest that less than 10% of neurodegenerative diseases have a strict genetic aetiology and other factors may be prevalent. Environmental exposures to potentially toxic elements appear to be a risk factor for Parkinson’s, Alzheimer’s and sclerosis diseases. This study proposes a multidisciplinary approach combining neurosciences, psychology and environmental sciences while integrating socio-economic, neuropsychological, environmental and health data. We present the preliminary results of a neuropsychological assessment carried out in elderly residents of the industrial city of Estarreja. A battery of cognitive tests and a personal questionnaire were administered to the participants. Multivariate analysis and multiple linear regression analysis were used to identify potential relationships between the cognitive status of the participants and environmental exposure to potentially toxic elements. The results suggest a relationship between urinary PTEs levels and the incidence of cognitive disorders. They also point towards water consumption habits and profession as relevant factors of exposure. Linear regression models show that aluminium (R 2 = 38%), cadmium (R 2 = 11%) and zinc (R 2 = 6%) are good predictors of the scores of the Mini-Mental State Examination cognitive test. Median contents (µg/l) in groundwater are above admissible levels for drinking water for aluminium (371), iron (860), manganese (250), and zinc (305). While the World Health Organization does not provide health-based reference values for aluminium, results obtained from this study suggest that it may have an important role in the cognitive status of the elderly. Urine proved to be a suitable biomarker of exposure both to elements with low and high excretion rates. 相似文献
56.
Ana P. L. Batista Hudson Wallace Pereira Carvalho Gustavo H. P. Luz Paulo F. Q. Martins Maraísa Gonçalves Luiz C. A. Oliveira 《Environmental Chemistry Letters》2010,8(1):63-67
A photocatalyst based on CuO/SiO2 was prepared, and evaluated for the degradation of methylene blue in aqueous medium. The photocatalyst was obtained by calcination
method of copper salt, in the presence of silica. The characterization by XRD, FTIR, and TPR techniques confirmed the formation
of CuO as active phase. SEM studies showed CuO deposited on the surface of SiO2. By ESI-MS, it was demonstrated that the degradation of methylene blue occurs through successive hydroxylations. Photodegradation
assays showed that CuO/SiO2 was efficient for degradation, and that the material worked better in the presence of UV light. 相似文献
57.
Maísa Tatiane Ferreira de Souza Elizangela Ambrosio Cibele Andrade de Almeida Thábata Karoliny Formicoli de Souza Freitas Lídia Brizola Santos Vitor de Cinque Almeida Juliana Carla Garcia 《Environmental monitoring and assessment》2014,186(8):5261-5271
The goal of this study was to investigate the activity of the coagulant extracted from the cactus Opuntia ficus-indica (OFI) in the process of coagulation/flocculation of textile effluents. Preliminary tests of a kaolinite suspension achieved maximum turbidity removal of 95 % using an NaCl extraction solution. Optimization assays were conducted with actual effluents using the response surface methodology (RSM) based on the Box–Behnken experimental design. The responses of the variables FeCl3, dosage, cactus dosage, and pH in the removal of COD and turbidity from both effluents were investigated. The optimum conditions determined for jeans washing laundry effluent were the following: FeCl3 160 mg L?1, cactus dosage 2.60 mg L?1, and pH 5.0. For the fabric dyeing effluent, the optimum conditions were the following: FeCl3 640 mg L?1, cactus dosage 160 mg L?1, and pH 6.0. Investigation of the effects of the storage time and temperature of the cactus O. ficus-indica showed that coagulation efficiency was not significantly affected for storage at room temperature for up to 4 days. 相似文献
58.
Wind selectivity of migratory flight departures in birds 总被引:5,自引:0,他引:5
Optimal migration theory predicts that birds minimizing the overall time of migration should adjust stopover duration with
respect to the rate of fuel accumulation. Recent theoretical developments also take into account the wind situation and predict
that there is a time window (a set of days) during which birds should depart when assisted by winds but will not do so if
there are head winds. There is also a final day when birds will depart irrespective of wind conditions. Hence, the wind model
of optimal migration theory predicts that birds should be sensitive to winds and that there should be a correlation between
departures and winds blowing towards the intended migration direction. We tested this assumption by tracking the departures
of radio-tagged passerines during autumn migration in southern Sweden. Our birds were moderately to very fat when released
and therefore energetically ready for departure. There was a significant correlation between direction of departure and wind
direction. We also found that during days when birds departed there was a significantly larger tail wind component than during
days when birds were present but did not depart. Our results show that passerines do take the current wind situation into
account when departing on migratory flights. We also briefly discuss possible clues that birds use when estimating wind direction
and strength. The inclusion of wind is an important amendment to optimal migration theory of birds and should be explored
further.
Received: 1 March 1999 / Received in revised form: 4 October 1999 / Accepted: 16 October 1999 相似文献
59.
Leif Gustavsson Åsa Karlsson 《Mitigation and Adaptation Strategies for Global Change》2006,11(5-6):935-959
The replacement of fossil fuels by biofuels could be an important means of reducing net carbon dioxide (CO2) emission. An estimation of the CO2 mitigation efficiency of biofuel systems depends on the method and assumptions used. Here, different parameters and methods are discussed for comparing fossil-fuel- and biofuel-based systems. Three parameters are suggested: the monetary cost, the primary energy cost and the biofuel cost of CO2 mitigation. They are defined as the difference in monetary expenditure, primary energy use and biofuel use between the compared systems, divided by the difference in net CO2 emission between the systems. Cogeneration and separate production of electricity and heat is then compared using these parameters and the methods of multi-functional products or subtraction. In both methods, either electricity or heat is regarded as the main product and the other is regarded as a by-product. The multi-functional method is preferable due to its transparency as both the main product and the by-product are part of the functional unit. Using heat as the main product illustrates the typical situation that the heat demand limits the use of cogeneration. When comparing systems the output from them should not differ. If the by-product is not fully, cogenerated part of the by-product has to be produced separately. A logical choice for producing this part of the by-product is to use a similar fuel and technology as used for cogeneration. 相似文献
60.
A Quantitative Review of Urban Ecosystem Service Assessments: Concepts,Models, and Implementation 总被引:3,自引:0,他引:3
Dagmar Haase Neele Larondelle Erik Andersson Martina Artmann Sara Borgström Jürgen Breuste Erik Gomez-Baggethun Åsa Gren Zoé Hamstead Rieke Hansen Nadja Kabisch Peleg Kremer Johannes Langemeyer Emily Lorance Rall Timon McPhearson Stephan Pauleit Salman Qureshi Nina Schwarz Annette Voigt Daniel Wurster Thomas Elmqvist 《Ambio》2014,43(4):413-433
Although a number of comprehensive reviews have examined global ecosystem services (ES), few have focused on studies that assess urban ecosystem services (UES). Given that more than half of the world’s population lives in cities, understanding the dualism of the provision of and need for UES is of critical importance. Which UES are the focus of research, and what types of urban land use are examined? Are models or decision support systems used to assess the provision of UES? Are trade-offs considered? Do studies of UES engage stakeholders? To address these questions, we analyzed 217 papers derived from an ISI Web of Knowledge search using a set of standardized criteria. The results indicate that most UES studies have been undertaken in Europe, North America, and China, at city scale. Assessment methods involve bio-physical models, Geographical Information Systems, and valuation, but few study findings have been implemented as land use policy.