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641.
Best estimates for the solid-liquid distribution coefficients (Kd) of radiostrontium and radiocaesium for various soil types, were derived from geometric means (GM) calculated from grouping soils by texture and organic matter content, and also using soil cofactors governing soil–radionuclide interaction. The Kd (Sr) GM for Sand, Loam, Clay and Organic groups were similar, although the value for the Sand group was significantly lower. The Sr cofactor approach, based on the ratios of cation exchange capacity (CEC) to Ca and Mg concentrations in the soil solution, leads to Kd (Sr) GM with a lower variability, from which best estimates could be proposed. The Kd (Cs) GM for Sand and Organic groups differed, although similar values were obtained for Loam and Clay groups. Grouping the Kd (Cs) according to the Radiocaesium Interception Potential (RIP) and the RIP divided by the K concentration in the soil solution also allows to suggest Kd (Cs) best estimates with a lower variability. 相似文献
642.
Review of fluoride removal from drinking water 总被引:9,自引:0,他引:9
M. Mohapatra S. Anand B.K. Mishra Dion E. Giles P. Singh 《Journal of environmental management》2009,91(1):67-77
Fluoride in drinking water has a profound effect on teeth and bones. Up to a small level (1–1.5 mg/L) this strengthens the enamel. Concentrations in the range of 1.5–4 mg/L result in dental fluorosis whereas with prolonged exposure at still higher fluoride concentrations (4–10 mg/L) dental fluorosis progresses to skeletal fluorosis. High fluoride concentrations in groundwater, up to more than 30 mg/L, occur widely, in many parts of the world. This review article is aimed at providing precise information on efforts made by various researchers in the field of fluoride removal for drinking water. The fluoride removal has been broadly divided in two sections dealing with membrane and adsorption techniques. Under the membrane techniques reverse osmosis, nanofiltration, dialysis and electro-dialysis have been discussed. Adsorption, which is a conventional technique, deals with adsorbents such as: alumina/aluminium based materials, clays and soils, calcium based minerals, synthetic compounds and carbon based materials. Studies on fluoride removal from aqueous solutions using various reversed zeolites, modified zeolites and ion exchange resins based on cross-linked polystyrene are reviewed. During the last few years, layered double oxides have been of interest as adsorbents for fluoride removal. Such recent developments have been briefly discussed. 相似文献
643.
Sebastiaan J.H. Rietjens Kirsten Verlaan Thijs W. Brocades Zaalberg Sirp J. De Boer 《Disasters》2009,33(3):412-435
This paper seeks to contribute to an improved information management and exchange between humanitarian organisations and military agents in complex emergencies. To do so, a theoretical information management process model was developed and applied to the case of information management between International Security Assistance Force troops and humanitarian organisations such as Cordaid, DACAAR and the International Office for Migration in Kabul, Afghanistan. Based on this analysis the main shortcomings and problems in each stage of the information management process were identified. These include a lack of structured information databases, the absence of identification of information needs, and an over‐classification of documents by the military. Using a logical framework analysis, six major improvement tactics were developed, including the creation of more overlap in rotations of personnel, the specification of aims and tasks regarding information management, the improvement of skills and competences of personnel involved, and the introduction of regular joint civil–military evaluations. 相似文献
644.
Dry deposition and soil-air gas exchange of polychlorinated biphenyls (PCBs) in an industrial area 总被引:3,自引:0,他引:3
Bozlaker A Odabasi M Muezzinoglu A 《Environmental pollution (Barking, Essex : 1987)》2008,156(3):784-793
Ambient air and dry deposition, and soil samples were collected at the Aliaga industrial site in Izmir, Turkey. Atmospheric total (particle + gas) ∑41-PCB concentrations were higher in summer (3370 ± 1617 pg m−3, average + SD) than in winter (1164 ± 618 pg m−3), probably due to increased volatilization with temperature. Average particulate ∑41-PCBs dry deposition fluxes were 349 ± 183 and 469 ± 328 ng m−2 day−1 in summer and winter, respectively. Overall average particulate deposition velocity was 5.5 ± 3.5 cm s−1. The spatial distribution of ∑41-PCB soil concentrations (n = 48) showed that the iron-steel plants, ship dismantling facilities, refinery and petrochemicals complex are the major sources in the area. Calculated air-soil exchange fluxes indicated that the contaminated soil is a secondary source to the atmosphere for lighter PCBs and as a sink for heavier ones. Comparable magnitude of gas exchange and dry particle deposition fluxes indicated that both mechanisms are equally important for PCB movement between air and soil in Aliaga. 相似文献
645.
采用共沉淀法制备了钛/钙氢氧化物新型吸附剂,并对其吸附除As的性能进行了初步研究.考察了不同制备方法、Ti/Ca比例、pH值、Ca2+、磷酸根离子对As(Ⅲ)和As(Ⅴ)去除率的影响,研究了所制备吸附剂对As(Ⅲ)和As(Ⅴ)的吸附热力学特性,并对其吸附机理进行了探讨.结果表明:所制备吸附剂对As(Ⅲ)具有优异的选择性;吸附去除率试验中,吸附剂投加量0.2 g/L、As质量浓度1 mg/L、20℃、吸附3h条件下,TC-45/5吸附剂对As(Ⅲ)的去除率达到97.3%,对As(Ⅴ)的去除率为78.2%;酸性条件和Ca2+可显著提高As(Ⅴ)去除率,但对As(Ⅲ)吸附去除的影响不大;磷酸根离子由于竞争吸附而导致As去除率下降,且对去除As(Ⅴ)的抑制作用更强烈;30℃时,As(Ⅲ)与As(Ⅴ)的Langmuir饱和吸附量分别为30.21 mg/g和16.61mg/g.研究表明,钛/钙氢氧化物对As(Ⅲ)去除效果良好. 相似文献
646.
647.
648.
Decomposition of alachlor by ozonation and its mechanism 总被引:1,自引:0,他引:1
Decomposition and corresponding mechanism of alachlor, an endocrine disruptor in water by ozonation were investigated. Results showed that alachlor could not be completely mineralized by ozone alone. Many intermediates and final products were formed during the process, including aromatic compounds, aliphatic carboxylic acids, and inorganic ions. In evoluting these products, some of them with weak polarity were qualitatively identified by GC-MS. The information of inorganic ions suggested that the dechlorination was the first and the fastest step in the ozonation of alachlor. 相似文献
649.
An improved method,suitable for collecting nitrate from surface waters in the watershed for 15 N isotope tracing analysis,was developed on the basis of the anion exchange coupled with diffusion through systematic simulation and comparison experiments.The results showed that the nitrate could be separated and enriched from the waters efficiently by using the improved method.Being simple and practical in operation principle and procedures,cost-economic,and highly efficient in nitrate separation/enrichment,the method met the requirements of δ 15 N mass spectrum analysis and would lay a foundation for the application of 15 N isotope tracing approach to the research on non-point source pollution in watershed. 相似文献
650.