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991.
992.
Effects of Fe2O3, organic matter and carbonate on photocatalytic degradation of lindane in the sediment from the Liao River,China 总被引:1,自引:0,他引:1
Fourteen sediment samples with different content of Fe2O3 were collected from the lower reaches of the Liao River in China. The photodegradation of lindane on the surfaces of these sediments was investigated to observe the effects of Fe2O3 and other photoinducable substances, such as TiO2 and organic substances, on photodegradation of lindane. A partial least-squares (PLS) analysis model was developed to find out the statistical relationship between the photodegradation and the contents of these photoinducable substances. It was concluded from the PLS analysis that inorganic carbon and organic carbon have negative effects, whereas Fe2O3 and TiO2 accelerate the photodegradation of lindane in the sediment samples when 365 nm UV light was used as light source. In all cases of the experiments, the photodegradation of lindane in the sediment samples were fitted for pseudo-first-order kinetics. 相似文献
993.
Nutrient dynamics and the eutrophication of shallow lakes Kasumigaura (Japan), Donghu (PR China), and Okeechobee (USA) 总被引:21,自引:0,他引:21
Havens KE Fukushima T Xie P Iwakuma T James RT Takamura N Hanazato T Yamamoto T 《Environmental pollution (Barking, Essex : 1987)》2001,111(2):263-272
We compared the nutrient dynamics of three lakes that have been heavily influenced by point and non-point source pollution and other human activities. The lakes, located in Japan (Lake Kasumigaura), People's Republic of China (Lake Donghu), and the USA (Lake Okeechobee), all are relatively large (> 30 km2), very shallow (< 4 m mean depth), and eutrophic. In all three lakes we found strong interactions among the sediments, water column, and human activities. Important processes affecting nutrient dynamics included nitrogen fixation, light limitation due to resuspended sediments, and intense grazing on algae by cultured fish. As a result of these complex interactions, simple empirical models developed to predict in-lake responses of total phosphorus and algal biomass to external nutrient loads must be used with caution. While published models may provide 'good' results, in terms of model output matching actual data, this may not be due to accurate representation of lake processes in the models. The variable nutrient dynamics that we observed among the three study lakes appears to be typical for shallow lake systems. This indicates that a greater reliance on lake-specific research may be required for effective management, and a lesser role of inter-lake generalization than is possible for deeper, dimictic lake systems. Furthermore, accurate predictions of management impacts in shallow eutrophic lakes may require the use of relatively complex deterministic modeling tools. 相似文献
994.
Gfrerer M Martens D Gawlik BM Wenzl T Zhang A Quan X Sun C Chen J Platzer B Lankmayr E Kettrup A 《Chemosphere》2002,47(4):455-466
The results of a one-year monitoring program on the two Eastern Chinese River systems, i.e. the Liao-He and the Yangtse, with special emphasis on the presence of triazine herbicides are presented. Sediment, suspended solids and water samples from both rivers were analyzed. Additionally, recovery experiments on the SPE-in-field-enrichment procedure and the extraction methods were performed. The samples were measured by gas chromatography coupled with mass spectrometry, electron capture detection and a newly developed mu-plasma atomic emission detector. A typical result of a one-year monitoring was obtained in case of the Liao-He: During winter, at low water period, low triazine values were found. A similar situation was found in early spring. Highest concentrations of atrazine up to 1600 ng/l were found in late spring in the water samples. Maximum concentrations of atrazine, simazine, propazine, simetryn and prometryn were observed in this season as a result of the actual use of triazines. Finally, after the high water period in autumn the triazine concentrations decreased. Additionally, atrazine adsorbed on sediment (up to 2.8 ng/g) and suspended solids was determined (up to 8 ng/l) during late spring sampling. Therefore, the logarithm of the organic carbon based sorption coefficient of atrazine could be calculated. Low levels of atrazine were measured in the water of Yangtse (up to 18.3 ng/l). The concentrations from all sampling points and sampling stations of a particular sampling date were similar, which indicates a homogeneous distribution of this herbicide. Due to the high discharge rate of up to 79,000 m3/s in case of the Yangtse a considerable mass transport of up to 57.5 kg per day atrazine may take place, even at concentrations below the European drinking water limit of 100 ng/l. 相似文献
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Yanhe Han Xie Quan Huimin Zhao Shuo Chen Yazhi Zhao 《Frontiers of Environmental Science & Engineering》2007,1(1):83-88
The adsorption kinetics for model pollutants on activated carbon fiber (ACF) by polarization was investigated in this work. Kinetics data obtained for the adsorption of these model pollutants at open-circuit, 400 mV, and ?400 mV polarization were applied to the Lagergren equation, and adsorption rate constants (K a) were determined. With the anodic polarization of 400 mV, the capacity of sodium phenoxide was increased from 0.0083 mmol/g at open-circuit to 0.18 mmol/g, and a 17-fold enhancement was achieved; however, the capacity of p-nitrophenol was decreased from 2.93 mmol/g at open-circuit to 2.65 mmol/g. With the cathodal polarization of ?400 mV, the capacity of aniline was improved from 3.60 mmol/g at open-circuit to 3.88 mmol/g; however, the capacity of sodium dodecylbenzene sulfonate was reduced from 2.20 mmol/g at open-circuit to 1.59 mmol/g. The enhancement for electrosorption changed with different groups substituting. Anodic polarization enhances the adsorption of benzene with the electron-donating group. But whether anodic or not, cathodal polarization had less effect on the adsorption of electron-accepting aromatic compounds, and decreased the adsorption capacity of benzene-bearing donor-conjugate bridge-acceptor, while increasing its adsorption rate. Electrostatic interaction played a very important role in the electrosorption of ion-pollutants. 相似文献
1000.
发达国家城市环境治理的进程大致经历城市环境治理非限制阶段、治理起步阶段、工业化防治阶段、城市环境综合防治阶段、城市环境治理可持续发展阶段等。中国城市环境治理大致经历了城市工业点源治理阶段、城市污染综合防治阶段、城市环境综合整治阶段、城市生态建设与环境质量全面改善阶段。 相似文献