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591.
折流式水解反应器处理印染废水水温影响研究 总被引:1,自引:0,他引:1
在水温为5℃、9.7℃、14.9℃、19.7℃、23.5℃和31.1℃6种温度的条件下,应用折流式水解反应器对印染废水进行水解试验研究.结果表明,提高水温可增大COD、色度及UVA254的去除效率,相应的ORP值变小,pH值升高,水解程度加深.水温5℃时,水解效果较差;水温在10~23.5℃内,水解效果相对较好,31.1℃水解效果最好,研究结果能为工程应用提供一定的参考. 相似文献
592.
属性识别理论模型在湖泊水质富营养化评价中的应用 总被引:25,自引:4,他引:21
近年来提出的属性识别理论模型已在环境质量评价中有所应用。现将该模型引用到湖泊水质富营养化评价中来 ,并用此模型对福州市山仔水库的水质进行评价 ,其评价结果与运用模糊隶属函数法得到的结果进行比较 ,其结果令人满意。此模型为湖泊水质的富营养化评价提供一种简便实用的评价方法 相似文献
593.
594.
Musah Mohammed Kong Yusheng Mensah Isaac Adjei Antwi Stephen Kwadwo Osei Agyemang Andrew Donkor Mary 《Environment, Development and Sustainability》2021,23(10):15225-15239
Environment, Development and Sustainability - This paper explored the link between energy consumption and carbon emissions in North Africa through an Environmental Kuznets Curve (EKC) framework.... 相似文献
595.
Hu Z Navarro R Nomura N Kong H Wijesekara S Matsumura M 《Environmental science and pollution research international》2007,14(1):12-18
Background There has been an increasing concern about the treatment and disposal of contaminated sediment from dredged river, harbor
or estuary due to the accumulated toxic organics such as dioxins and inorganics particularly heavy metals like Cr, Pb, Zn,
Cu, Hg and Cd. However, considering the huge amount of materials and financial costs involved, any candidate technology must
ultimately result to reusable residual by-products. This can only be made possible if the toxic pollutants are removed or
stabilized in the raw sediment and then fed back into the materials cycle. Currently, we are developing a pyrolysis process
for the commercial-scale cleanup of dioxins and heavy metal-contaminated river sediment to yield reusable char for various
economical applications. In this connection, this paper describes our preliminary investigation into the extent of dioxins
and heavy metal volatilization from actual contaminated sediment. The stabilization of certain metallic species particularly
Cr ions was studied.
Methods Laboratory scale pyrolysis experiments were conducted using a special horizontal lab-scale pyrolyzer. Sediment samples from
Shanghai Suzhou Creek and Tagonoura Harbor were pyrolyzed in the reactor under nitrogen gas at 800°C and different retention
times of 30, 60 and 90 min. A constant heating rate of 10°C min-1 was employed. The pyrolysis gas was first allowed to pass
through a cold trap to condense the tar. Uncondensed gases were then channeled through a column containing an adsorbent (XAD-2
Resin) for dioxins. Heavy metal concentrations in the initial and final sediment residues were analyzed by ICP (Nippon Jarrel-Ash)
following their acid and alkali (for Cr6+) digestion. Dioxins content of the pyrolysis char, tar, and exhaust gases in the
dioxin adsorbent were also determined. For comparative purpose, thermal treatment under air flow was conducted.
Results The data for the removal of heavy metals from Suzhou Creek sediment showed very significant reductions in Pb, Zn and Cr6+
content of the sediment at this condition. Percentage removals were 42.4%, 60.8% and 42.2%, respectively. The disappearance
of Cr6+ was due to reduction reactions rather than volatilization since the total Cr content remained almost unchanged. Other
heavy metals such as Cu, Fe and Ni showed very minimal reductions. Nonetheless, Toxicity Characteristics Leaching Procedure
(TCLP) tests confirmed that these residual heavy metals were rather stable in the pyrolysis char. Reduction of toxic Cr6+
at 42.2% has also been achieved by pyrolysis (with N2) as opposed to the more than 580 % increase in Cr6+ observed during
thermal oxidation (with air).
Discussion Pyrolysis also remove toxic organics particularly dioxins from the sediment. For the total dioxins, removal percentage of
99.9999% was achieved even at the lowest retention time of 30 min. Almost all polychlorinated dibenzo-p-dioxine (PCDDs) and
polychlorinated dibenzo-furans (PCDFs) were removed at any retention time. The TEQs detected from the solid residues were
mainly contributed by dioxin-like PCBs, yet these were present in relatively trace quantities. At the shortest retention time
of 30 min, only 0.000085 pg-TEQ g-1 of polychlorinated biphenyls (PCBs) was detected in the pyrolysis char. Furthermore, the
residual PCBs have very low toxicity ratings and none of the highly toxic PCBs, which were initially present in the sediment
such as 3,3',4,4',5-PeCB and 3,3',4,4'5,5'-HxCB, were detected in the char. Results further confirmed that most of the dioxins
that were removed were transferred to the gas phase so that volatilization may be considered as the main mechanism for their
removal.
Conclusion Some heavy metals particularly Pb and Zn can be volatilized under N2 pyrolysis at 800oC. Pyrolysis also prevented the formation
of more toxic Cr6+ ions and at the same time resulted to its reduction by around 42.2% contrast to the 580% increase during
thermal oxidation. PCDDs and PCDFs have been removed and were not formed in the solid products over the retention time range
of 30-90 min at 800°C. Dioxin-like PCBs mostly remained and a retention time of 30 min was found sufficient for its maximum
removal.
Recommendations and Perspective . With the above results, a temperature of 800oC at a retention time of 30 min is sufficient for the removal of total dioxins
and some heavy metals by volatilization. It is however necessary to destroy the dioxins as well as recover heavy metals in
the gas phase. Stability of remaining heavy metals in the char also needs to be confirmed by leaching tests. These are the
major concerns, which we are currently evaluating to establish the feasibility of our proposed large scale pyrolysis system
for sediment treatment. 相似文献
596.
Thirteen organochlorine pesticides (OCPs) in 18 fish species from Qiantang River were firstly determined by GC-ECD. To elucidate the sources and the environment fate of these pollutants, water and sediment samples were also analyzed for OCPs contents. Total concentrations of OCPs in fish muscles ranged from 7.43 to 143.79 ng g(-1) wet weight (ww) with highest concentration recorded in sole fish (Cynoglossus abbreviatus), a benthic carnivore. The results indicated that carnivore fish have higher OCPs concentration than other fish with different feeding modes. OCPs concentration in fish was in the range of 1.86-5.85, 2.65-133.51 and 1.94-12.48 ng g(-1) for HCHs (alpha-, beta-, gamma-, delta-HCH), DDTs (p,p'-DDD, p,p'-DDE, p,p'-DDT, o,p'-DDD) and other OCPs (aldrin, diedrin, endrin, heptachlor, heptachlor expoide), respectively. The highest OCPs concentration in fish organs of four big fish species was found in brain of silver carp (Hypophthalmichthys molitrix), 289.26 ng g(-1) ww followed by kidney, liver, heart and gill. Among the OCPs analyzed, DDE, gamma-HCH and heptachlor were the predominant contaminants in fish muscle, which indicated that there was recent input of lindane. Significant correlation was observed between concentrations of DDTs and lipid content as well as between OCPs and lipid contents in fish species. Both field water bioconcentration factors (BCF) and sediment BCF showed a positive correlation with octanol-water partition coefficients (Kow) in the sole fish. 相似文献
597.
Kong WD Zhu YG Liang YC Zhang J Smith FA Yang M 《Environmental pollution (Barking, Essex : 1987)》2007,147(1):187-193
A series of experiments were conducted in a hydroponic system to investigate the uptake of oxytetracycline (OTC) and its toxicity to alfalfa (Medicago sativa L.). OTC inhibited alfalfa shoot and root growth by up to 61% and 85%, respectively. The kinetics of OTC uptake could be well described by Michaelis-Menten equation with Vmax of 2.25 micromol g-1 fresh weight h-1, and Km of 0.036 mM. The uptake of OTC by alfalfa was strongly inhibited by the metabolic inhibitor, 2,4-DNP (2,4-dinitrophenol), at pH 3.5 and 6.0, but not by the aquaporin competitors, glycerol and Ag+. OTC uptake, however, was significantly inhibited by Hg2+, suggesting that the inhibition of influx was due to general cellular stress rather than the specific action of Hg2+ on aquaporins. Results from the present study suggested that OTC uptake into alfalfa is an energy-dependent process. 相似文献
598.
A regression method was developed for the hydrophobicity ruler approach, which is an indirect method for determining the octanol/water partition coefficients of very hydrophobic compounds. Two constants introduced into the mathematical model were obtained by regression of the absorption data sampled before the partition equilibrium. A water miscible organic solvent was used to increase the solubility of the very hydrophobic compounds in the aqueous solution so that the hydrophobicity scale was reduced and the equilibration was accelerated. Polydimethylsiloxane/methanol aqueous solution and a series of 21 polychlorinated biphenyls (PCBs) were used to demonstrate the regression method. The PCB compounds with known experimental logK(o/w) values served as reference compounds, while the PCB compounds without known logK(o/w) values were determined. The distribution coefficients (logK(p/s)), uptake and elimination rate constants were obtained from the two regression constants for each compound (reference or unknown). The correlation of the logK(p/s) values of the reference PCB compounds with their logK(o/w) values was linear (logK(o/w)=2.69logK(p/s)+0.76, R(2)=0.97). The logK(o/w) values were compared with literature values and suggested that some values from the literature far off the calibration line could be inaccurate. The critical experimental factors, the merits of the regression method were discussed. 相似文献
599.
600.
Jinming Luo Yongjie Wang Zhongyan Gao Wenfeng Wang 《Environmental science and pollution research international》2017,24(19):16351-16363
Environmental Science and Pollution Research - The excessive enrichment of trace elements, such as Pb and Cd, from food may contribute to the decline of migratory red-crowned cranes (Grus... 相似文献