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排序方式: 共有708条查询结果,搜索用时 468 毫秒
461.
Shuting Luo Xiaodong Wu Baofang Jin Shuang Liu Rui Ran Zhichun Si Duan Weng 《环境科学学报(英文版)》2020,32(8):64-71
Pt/Al2O3 catalysts with mean Pt particle size ranged from 2.7 to 7.1 nm were synthesized by chemical reduction method, and the sulfated counterparts were prepared by impregnation of sulfuric acid. The turnover frequency of platinum for soot oxidation under loose contact conditions in a feed flow containing NO and O2 are positively correlated with the size of platinum. The sulfated Pt/Al2O3 exhibits higher catalytic activity for soot oxidation in the presence of NO despite their reduced ability for NO2 production. Such a contradiction is more significant for those catalysts with smaller platinum particles. Herein, the catalysts were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), transmission electron microscopy (TEM), inductive coupled plasma (ICP) emission spectrometry, CO chemisorption, thermogravimetric analysis (TGA), NH3 temperature-programmed desorption (NH3-TPD), NO temperature-programmed oxidation (TPO) and NOx temperature-programmed desorption (TPD). Possible effect of Pt particle size for the catalytic oxidation of soot in the presence of NO was presented based primarily on the promoted NO2 transfer efficiency onto the soot pushed by the acidic catalysts. 相似文献
462.
Daojun Zhang Ziran M Baodong Wang Tao Zhu Duan Weng Xiaodong Wu Hongyan Wang Ge Li Jiali Zhou 《环境科学学报(英文版)》2020,32(2):145-154
A series of vanadium based catalysts(VxMn(4-x)Mo3Ce3/Ti) with different vanadium(x wt.%) and manganese((4-x) wt.%) contents have been prepared by the wet impregnation method and investigated for selective catalytic reduction(SCR) of NO_x by NH_3 in the presence of 8 vol.% H_2O and 500 ppm V SO_2.The physicochemical characteristics of the catalysts were thoroughly characterized.The SCR of NO_x by NH_3(NH_3-SCR) activity, especially the low-temperature activity, significantly increased with increasing V_2O_5 content in the catalyst until the V_2O_5 content reached 1.5 wt.%, which corresponds well with the redox properties of the catalyst.All of the metal oxides were well dispersed and strongly interacted with each other on the catalyst surface.V mainly exists in the V~(5+)state in the catalysts.The strong synergistic effect between the vanadium and cerium species led to formation of more Ce~(3+)species, and that between the vanadium and manganese species contributed to formation of more manganese species with low valences.All of the catalysts exhibited strong acidity, while the redox properties determined the NH_3-SCR activity, especially the low-temperature activity.H_2O and SO_2 had severe inhibiting effects on the activity of V1.5Mn2.5Mo3Ce3/Ti.However, good H_2O and SO_2 resistance and high NO_x conversion by V1.5Mn2.5Mo3Ce3/Ti could be achieved in the presence of SO_2 and almost no decline was observed in a long-term test at 275℃ for 168 hr in the presence of SO_2 and H_2O, which can be attributed to the sulfate species formed on the catalyst surface. 相似文献
463.
制备了炭化核桃壳,采用SEM,EDX,FTIR等方法对炭化核桃壳进行了表征,研究了炭化核桃壳对废水中Cr(Ⅵ)的吸附效果。表征结果显示,炭化后的核桃壳为片状结构,且形成了大量的微孔,微孔数量的增加使得核桃壳的比表面积明显增大。实验结果表明,炭化核桃壳吸附处理含Cr(Ⅵ)废水的最佳工艺条件为:初始废水pH 2.0、炭化核桃壳加入量16 g/L、吸附温度25 ℃、转速150 r/min、吸附时间180 min,在此最佳工艺条件下吸附处理Cr(Ⅵ)质量浓度为20 mg/L废水,Cr(Ⅵ)去除率高达98.7%,最大吸附量为8.731 mg/g。Langmuir吸附等温模型可更好地描述炭化核桃壳对Cr(Ⅵ)的吸附过程,吸附属于单分子层吸附。拟二级动力学方程能更好地描述炭化核桃壳对Cr(Ⅵ)的吸附行为,此吸附过程以化学吸附为主控步骤。 相似文献
464.
465.
A series of H-SAPO-34 zeolites were synthesized by a hydrothermal method in fluoride media. The as-synthesized H-SAPO-34 zeolites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 physisorption, temperature-programmed desorption of NH3 (NH3-TPD) and nuclear magnetic resonance (NMR) measurements. The results showed that a certain concentration of F− anions promoted the nucleation and crystallization of H-SAPO-34. The H-SAPO-34 synthesized in the fluoride media showed high crystallinity, uniform particle size distribution, large specific surface area and pore volume, and enhanced acidity. Therefore, Cu/SAPO-34 based on the fluoride-assisted zeolite showed a broadened temperature window for the selective catalytic reduction of NO by NH3 (NH3-SCR) reaction due to the enhanced acidity of the zeolite and the improved dispersion of copper species. 相似文献
466.
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468.
气瓶水压试验合格标准实验研究 总被引:4,自引:1,他引:3
水压试验是气瓶检验的主要项目,将容积残余变形率超过10% 作为气瓶报废的标准沿用至今。笔者通过实验,分析了气瓶水压试验现行评定标准存在的问题,并对采用容积弹性变形作为评定指标进行了探讨,以期为制订更合理的水压试验标准提供有益的启示。 相似文献
469.
Arsenic (As) is a pervasive and ubiquitous environmental toxin that has created catastrophic human health problems world-wide.
Chlamydomonas reinhardtii is a unicellular green alga, which exists ubiquitously in freshwater aquatic systems. Arsenic metabolism
processes of this alga through arsenate reduction and sequent store and efflux were investigated. When supplied with 10 mol/L arsenate,
arsenic speciation analysis showed that arsenite concentration increased from 5.7 to 15.7 mg/kg dry weight during a 7-day period,
accounting for 18%–24% of the total As in alga. When treated with different levels of arsenate (10, 20, 30, 40, 50 mol/L) for 7 days,
the arsenite concentration increased with increasing external arsenate concentrations, the proportion of arsenite was up to 23%–28%
of the total As in alga. In efflux experiments, both arsenate and arsenite could be found in the efflux solutions. Additionally, the efflux
of arsenate was more than that of arsenite. Furthermore, two arsenate reductase genes of C. reinhardtii (CrACR2s) were cloned and
expressed in Escherichia coli strain WC3110 (ΔarsC) for the first time. The abilities of both CrACR2s genes to complement the arsenatesensitive
strain were examined. CrACR2.1 restored arsenate resistance at 0.8 mmol/L. However, CrACR2.2 showed much less ability
to complement. The gene products were demonstrated to reduce arsenate to arsenite in vivo. In agreement with the complementation
results, CrACR2.1 showed higher reduction ability than CrACR2.2, when treated with 0.4 mmol/L arsenate for 16 hr incubation. 相似文献
470.
随着中国养殖业的迅速发展,禽畜粪便的排放数量逐年增加。据统计,禽畜粪尿排放量每头牛为55kg/d~65 kg/d,每头猪为3.5 kg/d~11.0 kg/d,每只鸡为0.10 kg/d~0.15 kg/d,每只羊为2.66 kg/d。大量的禽畜粪便不经处理而排入环境,将会对地表水、地下水、土壤和空气造成严重的污染,并危及禽畜本身及人体健康。因此,实现禽畜粪便的减量化、无害化及资源化,防止和消除养殖场粪便的污染及其利用问题的研究,对于生态环境的保护、实施可持续发展战略都具有十分重要的意义。本试验利用日本JST赠送的生态厕所反应装置为试验设备,分别以木屑和木屑与秸秆混合物为微生物载体,对牛粪便进行减量化处理技术研究。旨在为研究中国农业的玉米作物秸秆是否可以替代木屑作为反应过程中的调理剂,达到对禽畜养殖业粪便良好的减量化处理效果,减轻对环境的污染,同时也为中国大量的农作物秸秆寻找另一条资源化利用途径。 相似文献