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101.
Mercuric reductase is detected in Cephalosporium tabacinum F2.The enzyme, which is an intracellular one,catalyzes the reduction of mercuric ions to elemental mercury,which requires NADH as an electron donor and added sulfhydryl compound.The optimum temperature and pH of the enzymatic reaction are 30℃ and 7.0- 8. 0,respectively.The enzyme activity is stable in the range of 25- 30℃ for 40min,and stable at pH 7. 0 for 2 hours. Metal ions such as Ag+ ,CO2+), Cu2+,Zh2+, Mn2+,Ni2+ show different degrees of inhibitory effect on the enzyme activity,other compounds such as phenylmercury acetate and potassium ferricyanide also partially inhibit the enzyme activity. 相似文献
102.
环境条件和化学物质对叶类蔬菜硝酸盐的效应研究 总被引:11,自引:0,他引:11
在人工气候室和常温栽培条件下,研究了不同生长期化学物质赤霉素和钼酸铵对莴笋,小白菜硝酸盐含量和营养品质的效应。结果表明,两种环境下外源化学物质明显提高莴笋株高和小白菜根重,但却使莴笋叶绿素含量降低。两种环境G2和M2均明显提高两种叶类蔬菜AA的Vc含量,因而是G和M的最适施用时期。 相似文献
103.
离子色谱法测定硝酸盐氮研究 总被引:1,自引:0,他引:1
文章探讨了一处测定地表水和饮用水中硝酸盐氮的直接方法-离子色谱法,与常用的酚二磺酸比色法相比,该方法具有简便,安全的优点,干扰少,准确度高。 相似文献
104.
Prenatal diagnosis of methylenetetrahydrofolate reductase (MTHFR) deficiency and family studies were performed because of a severely affected first child in this family. The fetus at risk was found to be heterozygous as confirmed by the enzymatic activity assay performed several times after birth. In the father, MTHFR activity was normal in lymphocytes and decreased in fibroblasts, whereas in the asymptomatic mother, the activity was not detectable in fibroblasts and was very low in lymphocytes. The absence of any clinical symptoms in the mother despite a clear MTHFR deficiency and hyperhomocystinemia emphasizes the heterogeneity of this disease. 相似文献
105.
挥发性脂肪酸(VFA)是消化污泥上清液(DSS)中主要的组分。DSS是反硝化很好的碳源。在本试验条件下,DSS碳源完全反硝化的临界值为1.74mg DSS-C/mgNO3-N。但是,DSS中的TKN除了很小一部分被用于同化合成外,其大部分进入反硝化系统后不发生任何变化并出水排放。 相似文献
106.
酸雨致酸土壤对小麦幼苗若干营养代谢的影响 总被引:4,自引:2,他引:4
童贯和 《应用与环境生物学报》2005,11(3):279-282
通过模拟酸雨淋洗土壤,造成土壤酸化和盐基流失.将小麦幼苗栽培于由酸雨致酸的土壤,其体内的碳素代谢和氮素代谢受到抑制,从而导致体内可溶性糖含量和含N量下降.其中致酸土壤对根系碳素代谢和氮素代谢的抑制作用大于对茎叶碳素代谢和氮素代谢的抑制作用.表4参23 相似文献
107.
Vulnerability and risk evaluation of agricultural nitrogen pollution for Hungary's main aquifer using DRASTIC and GLEAMS models 总被引:5,自引:1,他引:4
Leone A Ripa MN Uricchio V Deák J Vargay Z 《Journal of environmental management》2009,90(10):2969-2978
In recent years, the significant improvement in point source depuration technologies has highlighted problems regarding, in particular, phosphorus and nitrogen pollution of surface and groundwater caused by agricultural non-point (diffuse) sources (NPS). Therefore, there is an urgent need to determine the relationship between agriculture and chemical and ecological water quality.This is a worldwide problem, but it is particularly relevant in countries, such as Hungary, that have recently become members of the European Community. The Italian Foreign Ministry has financed the PECO (Eastern Europe Countries Project) projects, amongst which is the project that led to the present paper, aimed at agricultural sustainability in Hungary, from the point of view of NPS. Specifically, the aim of the present work has been to study nitrates in Hungary's main aquifer. This study compares a model showing aquifer intrinsic vulnerability to pollution (using the DRASTIC parameter method; Aller et al. [Aller, L., Truman, B., Leher, J.H., Petty, R.J., 1986. DRASTIC: A Standardized System for Evaluating Ground Water Pollution Potential Using Hydrogeologic Settings. US NTIS, Springfield, VA.]) with a field-scale model (GLEAMS; Knisel [Knisel, W.G. (Ed.), 1993. GLEAMS—Groudwater Leaching Effects of Agricultural Management Systems, Version 3.10. University of Georgia, Coastal Plain Experimental Station, Tifton, GA.]) developed to evaluate the effects of agricultural management systems within and through the plant root zone. Specifically, GLEAMS calculates nitrate nitrogen lost by runoff, sediment and leachate.Groundwater monitoring probes were constructed for the project to measure: (i) nitrate content in monitored wells; (ii) tritium (3H) hydrogen radioisotope, as a tool to estimate the recharge conditions of the shallow groundwater; (iii) nitrogen isotope ratio δ15N, since nitrogen of organic and inorganic origin can easily be distinguished.The results obtained are satisfactory, above all regarding the DRASTIC evaluation method, which is shown to satisfactorily explain both low and high aquifer vulnerability, and furthermore proves to be a good tool for zoning hydrogeological regions in terms of natural system susceptibility to pollution. The GLEAMS model, however, proves not to be immediately usable for predictions, above all due to the difficulty in finding sufficient data for the input parameters. It remains a good tool, but only after an accurate validation, for decision support systems, in the specific case to integrate intrinsic vulnerability, from DRASTIC (or similar methods), with land use nitrate loads from GLEAMS, or similar methods.The PECO project has proved a positive experience to highlight the fundamental points of a decision support system, aimed to mitigate the nitrate risk for groundwater coming from Hungarian agricultural areas. 相似文献
108.
Groundwater nitrification is a poorly characterized process affecting the speciation and transport of nitrogen. Cores from two sites in a plume of contamination were examined using culture-based and molecular techniques targeting nitrification processes. The first site, located beneath a sewage effluent infiltration bed, received treated effluent containing O2 (> 300 µM) and NH4+ (51–800 µM). The second site was 2.5 km down-gradient near the leading edge of the ammonium zone within the contaminant plume and featured vertical gradients of O2, NH4+, and NO3− (0–300, 0–500, and 100–200 µM with depth, respectively). Ammonia- and nitrite-oxidizers enumerated by the culture-based MPN method were low in abundance at both sites (1.8 to 350 g− 1 and 33 to 35,000 g− 1, respectively). Potential nitrifying activity measured in core material in the laboratory was also very low, requiring several weeks for products to accumulate. Molecular analysis of aquifer DNA (nested PCR followed by cloning and 16S rDNA sequencing) detected primarily sequences associated with the Nitrosospira genus throughout the cores at the down-gradient site and a smaller proportion from the Nitrosomonas genus in the deeper anoxic, NH4+ zone at the down-gradient site. Only a single Nitrosospira sequence was detected beneath the infiltration bed. Furthermore, the majority of Nitrosospira-associated sequences represent an unrecognized cluster. We conclude that an uncharacterized group associated with Nitrosospira dominate at the geochemically stable, down-gradient site, but found little evidence for Betaproteobacteria nitrifiers beneath the infiltration beds where geochemical conditions were more variable. 相似文献
109.
Sana Ullah Xuejun Guo Xiaoyan Luo Xiangyuan Zhang Siwen Leng Na Ma Palwasha Faiz 《Frontiers of Environmental Science & Engineering》2020,14(5):89
110.