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221.
Cationic hydrogel with magnetic property was synthesized via radical polymerization and its removal capacity of chromate from
contaminated water was found to be 200 mg/g. Using Fourier transform infrared spectroscopy (FT-IR) study, the mechanism of
chromate removal by hydrogel was found to be non-specific adsorption, mainly due to ion exchange, as evidenced by the positively
charged functional group, trimethyl ammonium –N+(CH3)3; in the monomer. Verifications were accordingly determined by testing
different oxyanion adsorption onto the hydrogel. The results of the chromate adsorption experiments illustrated that the amount
of chromate adsorbed was nearly equal to that of the chloride released from the hydrogel, which is part of the evidence for ion
exchange. Single and multi-oxyanion adsorption experiments were also performed, and it was demonstrated that ion removal was
species independent, but charge dependent, another characteristic of the ion exchange process. It was found that the same Langmuir
model can be applied to best fit the findings of single and multi-oxyanion adsorption, which further indicates the mechanism of chromate
removal is attributed to ion exchange. In view of the above, the background anions compete for adsorption sites with chromate,
evidenced by inhibitive chromate removal in the presence of background electrolytes in the batch studies, further echoing the ion
exchange mechanism. 相似文献
222.
Stefano Colazza Mauro Lo Bue Daniela Lo Giudice Ezio Peri 《Die Naturwissenschaften》2009,96(8):975-981
Chemical footprints left behind by true bugs are perceived as contact kairomones by scelionid egg parasitoids. Female wasps
encountering a contaminated artificial substrate display a characteristic arrestment posture, holding the body motionless
and antennating the surface. In the system Nezara viridula (L.) and its egg parasitoid Trissolcus basalis (Wollaston), previous studies have shown that the kairomone mediating such behavior is part of N. viridula’s cuticular hydrocarbons (CHC) and furthermore that the wasp’s ability to discriminate host male and female footprints is mainly
based on the presence/absence of nonadecane (nC19). In this study, the effect of epicuticular waxes of leaves of broad bean, Vicia faba, on wasp responses to footprints of N. viridula females were investigated. Approximately 20% of T. basalis females displayed an arrestment posture when released on the adaxial leaf surfaces of broad bean plants with intact wax layer
and without host chemical contamination; whereas ∼70% of wasps displayed the arrestment posture when intact leaves were contaminated
by host female footprints. Adaxial leaf surfaces of broad bean plants dewaxed with an aqueous solution of gum arabic and afterwards
contaminated by N. viridula females induced arrestment responses in about 10% of female wasps; the same percentage of arrestment (10%) was observed when
the wasps were released on leaves contaminated by host females and subsequently dewaxed. The side of the polymer film that
was appressed to the leaf surface, peeled from the contaminated leaves, induced an arrestment posture in about 95% of observed
wasps. Scanning electron microscopy (SEM) revealed that the epicuticular waxes occurred as a film densely crystallized as
irregularly shaped platelets with spherical granules randomly distributed. These findings demonstrated that epicuticular waxes
of broad bean leaves can mediate the foraging behavior of T. basalis females by absorbing contact kairomones of the host. 相似文献
223.
Yuchi Lee Shanglien Lo Jeff Kuo Chinghong Hsieh 《Frontiers of Environmental Science & Engineering in China》2012,6(1):17-25
Microwave-hydrothermal treatment of persistent and bioaccumulative perfluorooctanoic acid (PFOA) in water with persulfate
(S2O82−) has been found effective. However, applications of this process to effectively remediate PFOA pollution require a better
understanding on free-radical scavenging reactions that also take place. The objectives of this study were to investigate
the effects of pH (pH = 2.5, 6.6, 8.8, and 10.5), chloride concentrations (0.01–0.15 mol·L−1), and temperature (60°C, 90°C, and 130°C) on persulfate oxidation of PFOA under microwave irradiation. Maximum PFOA degradation
occurred at pH 2.5, while little or no degradation at pH 10.5. Lowering system pH resulted in an increase in PFOA degradation
rate. Both high pH and chloride concentrations would result in more scavenging of sulfate free radicals and slow down PFOA
degradation. When chloride concentrations were less than 0.04 mol·L−1 at 90°C and 0.06 mol·L−1 at 60°C, presence of chloride ions had insignificant impacts on PFOA degradation. However, beyond these concentration levels,
PFOA degradation rates reduced significantly with an increase in chloride concentrations, especially under the higher temperature. 相似文献
224.
Contributions of biofilm and suspended sludge to nitrogen transformation and
nitrous oxide emission in hybrid sequencing batch system 总被引:2,自引:0,他引:2
Ingwei Wayne Lo Kwang Victor Lo Don S Mavini Dean Shiskowski William Ramey 《环境科学学报(英文版)》2010,22(7):953-960
Hybrid system combines the nature of suspended growth and attached growth has been widely applied to wastewater treatment.
In this research, the contributions to N transformation and N2O emission by biofilm and suspended sludge in the hybrid sequencingbatch
reactor for a simultaneous nitrification, denitrification and phosphorus removal process were investigated. For the hybrid system,
nitrification occurred mostly in the suspended sludge, while the biofilm played the major role in denitrification. The interaction of
the biofilm and the suspended sludge in the same reactor resulted in a better overall nitrogen removal performance with simultaneous
nitrification and denitrification. However, N2O emission was the main end product of nitrogen removal for the hybrid system; while
it was N2 for the biofilm. The relative low N2O emissions from the pure biofilm and the pure suspended sludge corresponded to the
relatively high nitrate at the end of the aeration period compared with the hybrid system. 相似文献
225.
Preparation of cross-linked magnetic chitosan with quaternary ammonium and its application for Cr(VI) and P(V) removal 总被引:2,自引:0,他引:2
Pollutants that exist in anionic species are issues of concern in water treatment. Compared to cationic pollutants, the removal of anionic pollutants by adsorption is more difficult because most adsorbents carry predominantly negative charges in neutral and alkaline environments. In this study, a cross-linked chitosan derivative with quaternary ammonium and magnetic properties(QM-chitosan) was prepared and employed to remove chromium(VI) and phosphorus(V)(Cr(VI) and P(V)) from aqueous environments. The QM-chitosan was characterized by Fourier transform infrared spectrometry(FT-IR),thermogravimetric analysis(TGA), energy dispersive X-ray(SEM-EDX) and zeta potential.Batch experiments show that QM-chitosan can effectively remove Cr(VI) and P(V), and the main mechanism was believed to be electrostatic interaction. A pseudosecond-order model was fitted to describe the kinetic processes of Cr(VI) and P(V) removal. The adsorption isotherms of both Cr(VI) and P(V) on the QM-chitosan were well fitted by the Langmuir isotherm equation. The saturated adsorption capacity of P(V)(2.783 mmol/g) was found to be higher than that of Cr(VI)(2.323 mmol/g), resulting from the size of the H2PO-4ions being smaller than that of the HCr O-4ions. However, the theoretical calculation and experimental results showed that QM-chitosan had a stronger affinity for Cr(VI) than P(V). The adsorption–desorption of the QM-chitosan was evaluated, and high regeneration rates were demonstrated. 相似文献
226.
227.
On the basis of the European Water Framework Directive (2000/60), the water resources of the member states of the European
Community should reach good quality standards by 2015. Although such regulations illustrate the basic points for a comprehensive
and effective policy of water monitoring and management, no practical tools are provided to face and solve the issues concerning
freshwater ecosystems such as rivers. The Italian government has developed a set of regulations as adoption of the European
Directive but failed to indicate feasible procedures for river monitoring and management. On a local scale, Sicilian authorities
have implemented monitoring networks of watersheds, aiming at describing the general conditions of rivers. However, such monitoring
programs have provided a relatively fragmentary picture of the ecological conditions of the rivers. In this study, the integrated
use of environmental quality indices is proposed as a methodology able to provide a practical approach to river monitoring
and management. As a case study, the Imera Meridionale River, Sicily’s largest river, was chosen. The water quality index
developed by the U.S. National Sanitation Foundation and the floristic quality index based on the Wilhelm method were applied.
The former enabled us to describe the water quality according to a spatial–temporal gradient, whereas the latter focused on
the ecological quality of riparian vegetation. This study proposes a holistic view of river ecosystems by considering biotic
and abiotic factors in agreement with the current European regulations. How the combined use of such indices can guide sustainable
management efforts is also discussed. 相似文献
228.
Artificial aggregate made from waste stone sludge and waste silt 总被引:1,自引:0,他引:1
Fang-Chih Chang Ming-Yu Lee Shang-Lien Lo Jyh-Dong Lin 《Journal of environmental management》2010,91(11):2289-2294
In this research, waste stone sludge obtained from slab stone processing and waste silt from aggregate washing plants were recycled to manufacture artificial aggregate. Fine-powdered stone sludge was mixed with waste silt of larger particle size; vibratory compaction was applied for good water permeability, resulting in a smaller amount of solidifying agent being used. For the densified packing used in this study, the mix proportion of waste stone sludge to waste silt was 35:50, which produced artificial aggregate of more compact structure with water absorption rate below 0.1%. In addition, applying vibratory compaction of 33.3 Hz to the artificial aggregate and curing for 28 days doubled the compressive strength to above 29.4 MPa. Hence, recycling of waste stone sludge and waste silt for the production of artificial aggregate not only offers a feasible substitute for sand and stone, but also an ecological alternative to waste management of sludge and silt. 相似文献
229.
Conservation efforts are often motivated by the threat of global extinction. Yet if conservationists had more information suggesting that extirpation of individual species could lead to undesirable ecological effects, they might more frequently attempt to protect or restore such species across their ranges even if they were not globally endangered. Scientists have seldom measured or quantitatively predicted the functional consequences of species loss, even for large, extinction‐prone species that theory suggests should be functionally unique. We measured the contribution of Asian elephants (Elephas maximus) to the dispersal of 3 large‐fruited species in a disturbed tropical moist forest and predicted the extent to which alternative dispersers could compensate for elephants in their absence. We created an empirical probability model with data on frugivory and seed dispersal from Buxa Tiger Reserve, India. These data were used to estimate the proportion of seeds consumed by elephants and other frugivores that survive handling and density‐dependent processes (Janzen‐Connell effects and conspecific intradung competition) and germinate. Without compensation, the number of seeds dispersed and surviving density‐dependent effects decreased 26% (Artocarpus chaplasha), 42% (Careya arborea), and 72% (Dillenia indica) when elephants were absent from the ecosystem. Compensatory fruit removal by other animals substantially ameliorated these losses. For instance, reductions in successful dispersal of D. indica were as low as 23% when gaur (Bos gaurus) persisted, but median dispersal distance still declined from 30% (C. arborea) to 90% (A. chaplasha) without elephants. Our results support the theory that the largest animal species in an ecosystem have nonredundant ecological functionality and that their extirpation is likely to lead to the deterioration of ecosystem processes such as seed dispersal. This effect is likely accentuated by the overall defaunation of many tropical systems. 相似文献
230.
Guor-Cheng Fang Chaur-Tsuen Lo Meng-Hsien Cho Yuan-Jie Zhuang Kai-Hsiang Tsai Chao-Yang Huang You-Fu Xiao 《Environmental geochemistry and health》2017,39(4):901-911
The main purpose of this study was to monitor ambient air particulates and mercury species [RGM, Hg(p), GEM and total mercury] concentrations and dry depositions over rural area at Longjing in central Taiwan during October 2014 to September 2015. In addition, passive air sampler and knife-edge surrogate surface samplers were used to collect the ambient air mercury species concentrations and dry depositions, respectively, in this study. Moreover, direct mercury analyzer was directly used to detect the mercury Hg(p) and RGM concentrations. The result indicated that: (1) The average highest RGM, Hg(p), GEM and total mercury concentrations, and dry depositions were observed in January, prevailing dust storm occurred in winter season was the possible major reason responsible for the above findings. (2) The highest average RGM, Hg(p), GEM and total mercury concentrations, dry depositions and velocities were occurred in winter. This is because that China is the largest atmospheric mercury (Hg) emitter in the world. Its Hg emissions and environmental impacts need to be evaluated. (3) The results indicated that the total mercury ratios of Kaohsiung to that of this study were 5.61. This is because that Kaohsiung has the largest industry density (~60 %) in Taiwan. (4) the USA showed average lower mercury species concentrations when compared to those of the other world countries. The average ratios of China/USA values were 89, 76 and 160 for total mercury, RGM and Hg(p), respectively, during the years of 2000–2012. 相似文献