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291.
Honey bees have a highly developed nest homeostasis, for example, maintaining low CO2 levels and stable nest temperatures at 35°C.We investigate the role of nest homeostasis in deactivating phenolic compounds present in the nectar of Aloe littoralis. We show that the phenolic content in nectar was reduced (from 0.65% to 0.49%) after nectar was incubated in a nest of Apis cerana, and that it was reduced still more (from 0.65% to 0.37%) if nectar was mixed with hypopharyngeal gland proteins (HGP) of worker bees before being placed inside a nest. HGP had little effect on samples outside a nest, indicating that nest conditions are necessary for HGP to deactivate phenolics in nectar. Consequently, the highly controlled nest homeostasis of honey bees facilitates direct deactivation of phenolics in nectar, and plays a role in the action of HGP as well. 相似文献
292.
293.
Cuiping Li Fangqiong Ling Minglu Zhang Wen-Tso Liu Yuxian Li Wenjun Liu 《环境科学学报(英文版)》2017,29(1):21-30
Understanding the spatial and temporal dynamics of microbial communities in drinking water systems is vital to securing the microbial safety of drinking water. The objective of this study was to comprehensively characterize the dynamics of microbial biomass and bacterial communities at each step of a full-scale drinking water treatment plant in Beijing, China. Both bulk water and biofilm samples on granular activated carbon (GAC) were collected over 9 months. The proportion of cultivable cells decreased during the treatment processes, and this proportion was higher in warm season than cool season, suggesting that treatment processes and water temperature probably had considerable impact on the R2A cultivability of total bacteria. 16s rRNA gene based 454 pyrosequencing analysis of the bacterial community revealed that Proteobacteria predominated in all samples. The GAC biofilm harbored a distinct population with a much higher relative abundance of Acidobacteria than water samples. Principle coordinate analysis and one-way analysis of similarity indicated that the dynamics of the microbial communities in bulk water and biofilm samples were better explained by the treatment processes rather than by sampling time, and distinctive changes of the microbial communities in water occurred after GAC filtration. Furthermore, 20 distinct OTUs contributing most to the dissimilarity among samples of different sampling locations and 6 persistent OTUs present in the entire treatment process flow were identified. Overall, our findings demonstrate the significant effects that treatment processes have on the microbial biomass and community fluctuation and provide implications for further targeted investigation on particular bacteria populations. 相似文献
294.
石墨炉原子吸收分光光度法测定土壤中总铬 总被引:1,自引:0,他引:1
建立了土壤中总铬测定的石墨炉原子吸收分光光度法;以塞曼效应扣除背景,优化了石墨炉灰化、原子化温度、停留时间及基体改进剂用量。结果表明:当原子化温度为2 700℃,灰化温度为700℃,原子化时间2 s,灰化时间为9 s;基体改进剂用量为3~5μL时,仪器可以达到最佳工作状态。该方法铬元素浓度在0~32μg/L内呈良好的线性关系,相关系数r=0.999 9,检出限为0.3 mg/kg;对土壤标样GSS-1和ESS-1的铬测定精密度均小于5%,相对误差在-4.8%~-0.7%之间,方法的灵敏度和准确度均符合要求。因此,石墨炉原子吸收分光光度法测定土壤中总铬具有原子化温度高、干扰少、灵敏度高等特点可适用土壤中总铬的测定。 相似文献
295.
Modeling and verifying chlorine decay and chloroacetic acid formation in drinking water chlorination
This study presents a phenomenological model that can be used by the water professionals to quantify chlorine decay and disinfection
byproduct (DBP) formation in water. The kinetic model was developed by introducing the concept of limiting chlorine demand
and extending an established reactive species approach. The limiting chlorine demand, which quantifies chlorine reactive natural
organic matter (NOM) on an equivalent basis, was mathematically defined by the relation between ultimate chlorine residue
and initial chlorine dose. It was found experimentally that NOM in water has limiting chlorine demand that increases with
chlorine dose once the ultimate residue is established. These results indicated that the complex NOM has a unique ability
to adjust chemically to the change in redox condition caused by the free chlorine. It is attributed mainly to the redundant
functional groups that persist in heterogeneous NOM molecules. The results also demonstrated that the effect of chlorine dose
on the rate of chlorine decay can be quantitatively interpreted with the limiting chlorine demand. The kinetic model developed
was validated for chlorine decay and chloroacetic acid formation in finished drinking water. 相似文献
296.
应用以MPSS模型为基础的计算软件UV calc对某饮用水紫外线消毒反应器进行强度分布的计算,同时,采用枯草芽孢杆菌(ATCC9372)作为受试菌种进行生物验证.结果显示,在该反应器中理论计算数值总体上明显高于生物验证的数值,反应器中最低紫外剂量区域出现在2支灯管之间的反应器壁附近.另外,理论计算和生物验证的误差与流量、透光率具有相关性.在高流量、低透光率的情况下,理论计算的数值更接近于生物验证数值.相对于理论计算,生物验证是确定紫外线反应器剂量反应曲线的可靠方法. 相似文献
297.
298.
Fangfang Chang Jiuhui Qu Xu Zhao Wenjun Liu Kun Wu 《Frontiers of Environmental Science & Engineering in China》2011,5(4):512-518
Fe-Mn binary oxide incorporated into porous diatomite (FMBO-diatomite) was prepared in situ and regenerated in a fixed-bed
column for arsenite [As(III)] and arsenate [As(V)] removal. Four consecutive adsorption cycles were operated under the following
conditions: Initial arsenic concentration of 0.1 mg·L−1, empty bed contact time of 5 min, and pH 7.0. About 3000, 3300, 3800, and 4500 bed volumes of eligible effluent (arsenic
concentration ⩽ 0.01 mg·L−1) were obtained in four As (III) adsorption cycles; while about 2000, 2300, 2500, and 3100 bed volumes of eligible effluent
were obtained in four As(V) adsorption cycles. The dissection results of FMBO-diatomite fixed-bed exhibited that small amounts
of manganese and iron were transferred from the top of the fixed-bed to the bottom of the fixed-bed during As(III) removal
process. Compared to the extremely low concentration of iron (<0.01 mg·L−1), the fluctuation concentration of Mn2+ in effluent of the As(III) removal column was in a range of 0.01–0.08 mg·L−1. The release of manganese suggested that manganese oxides played an important role in As(III) oxidation. Determined with
the US EPA toxicity characteristic leaching procedure (TCLP), the leaching risk of As(III) on exhausted FMBO-diatomite was
lower than that of As(V). 相似文献
299.
为了增强纳米零价铁的分散性,本研究采用环境友好型材料Pluronic F-127对纳米零价铁(NZVI)进行表面改性,形成分散型纳米零价铁(F-NZVI),并用于水中2,4-DCP的去除.通过不同质量比的F-NZVI颗粒沉降试验和对2,4-DCP的去除试验,发现存在沉降去除和悬浮去除两个阶段,确定F-127与NZVI颗粒的最佳质量比为2∶1,2,4-DCP最大去除率为72.32%.通过SEM、FTIR、XRD、XPS对样品进行表面形貌、组成和晶体结构分析,发现F-127对提高NZVI分散性和抗氧化性有显著作用.通过控制不同因素研究F-NZVI去除水中2,4-DCP的最优条件,实验结果表明,当2,4-DCP初始浓度为20 mg·L~(-1)时,F-NZVI去除2,4-DCP的最佳pH值为5,F-NZVI最佳投加量为3 g·L~(-1). 相似文献
300.
VOCs(挥发性有机物)已成为中国大气污染防治的重点污染物,涂料的生产和使用是VOCs排放的重要固定源.美国、欧盟于20世纪90年代制定了涂料制造工业的VOCs排放标准,而中国自2010年起才开始管控VOCs的排放.通过对美国、欧盟和中国现行的涂料制造工业VOCs排放标准体系进行对比研究发现,中国涂料制造工业VOCs排放标准体系完整且严厉,由源头替代、工艺过程控制、排放限值、监控与管理等构成,但存在表征方法不明确、分析方法不准确、总量控制指标缺乏等问题.因此,基于优化VOCs全过程防控标准体系,提出以下4点建议:①强化源头VOCs排放控制,制定高固分涂料、水性涂料(油墨)各类涂料产品的VOCs含量限值,并配以相关分析方法;②加强VOCs工艺过程控制,在强调密闭要求的基础上,制定吸风罩捕集效率的统一判断标准;③选用TOC(有机碳)代替NMHC(非甲烷总烃)作为VOCs的表征指标,借鉴欧盟的逸散率制定排放绩效值,构建总量控制指标;④实施溶剂管理计划和PRTR(污染物释放和转移登记记录),以实现VOCs减排的长效机制. 相似文献