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231.
根据煤与瓦斯突出"综合假说"理论,煤的物理力学性质在突出过程中扮演着重要的角色。利用大型煤与瓦斯突出模拟试验台为工具,选用粒径为5-10目、10-40目、40-80目,以及5-10目和10-40目不同粒级配比下的煤粒,在相同实验参数条件下制作成突出煤样,并分别进行煤与瓦斯突出模拟实验。结果表明:煤层吸附瓦斯是放热过程,煤体温度会不断增加,突出过程则正好相反。煤体的破碎程度越大(粒径越小),突出危险性程度就越高、发生突出的强度就越大;但突出强度大并不一定表现为粉碎率高,原因在于煤的破碎程度越高,进一步破碎的难度就越大,要达到相同破碎率所需的能量就越大。  相似文献   
232.
The effect of the dosing vehicle (e.g., dough) on the ability of an in vitro gastrointestinal (IVG) method to predict relative bioavailable Pb associated with soil ingestion was evaluated. Bioaccessible Pb determined by the IVG method was compared with relative bioavailable Pb measured from dosing trials using juvenile swine for 18 contaminated soils ranging from 1270 to 14200 mg Pb kg(-1). Bioaccessible Pb was measured in the IVG gastric extraction (GE) and intestinal extraction (IE) solutions. Mean bioaccessible Pb values were 32.2% for GE without dough, 23.0% for GE with dough, 1.06% for IE without dough, and 0.56% for IE with dough. It is possible that phytic acid associated with the dough addition decreased bioaccessible Pb. In vivo relative bioavailable Pb ranges for different swine tissues were 1 to 87% for blood, 0 to 110% for liver, 1 to 124% for kidney, and 0.04 to 94% for bone. Strong linear relationships between IVG GE Pb with dough (r > 0.76, P < 0.0002), IVG IE Pb with dough (r > 0.56, P < 0.015), and IVG GE Pb without dough (r > 0.81, P < 0.0001) and in vivo bioavailable Pb as estimated with blood, kidney, liver, and bone were found. Inexpensive in vitro methods may be useful in providing an estimate of the variability in relative bioavailable Pb at a single study site. The IVG method can be used to estimate relative bioavailable Pb, As, and Cd in contaminated soil.  相似文献   
233.
个体防护装备是抵御外来伤害,保护人体安全和健康的重要装备。近几年来,随着国民经济的快速发展。国家更加重视安全生产工作.制定了一系列法律、法规,明确规定了在作业场所必须佩带个体防护装备,促进了个体防护装备在各行各业的应用。随着以人为本。关爱生命和健康的观念日益深入人心.个体防护装备的应用正在向日常工作和生活领域扩展。  相似文献   
234.
全球高致病性禽流感灾害的时空变异   总被引:2,自引:0,他引:2  
利用多种资源建立了全球高致病性禽流感灾害数据库,基于ArcGIS的空间分析和统计模块,对全球高致病性禽流感灾害的时空变异进行分析。结果表明:2003年以来全球高致病性禽流感爆发有三个流行高峰期,正好在2004和2005年的冬季;全球高致病性禽流感爆发的频率在最近几年里呈不断上升的趋势,地理空间范围不断扩散;高致病性禽流感的爆发在时间和空间上表现得更加集中。全球高致病性禽流感分布的总体特征表明在家禽密度高的区域,邻近家禽生产地的湖泊和水库附近,或者鸟类迁徒路线的交叉处,特别是那些重叠的区域可能是高致病性禽流感的多发地区。上述结果可为高致病性禽流感灾害的防控提供借鉴和依据。  相似文献   
235.
概述了硫磺粉尘回收系统的研究现状,简要介绍了一套较为成功的设计方案和几个关键设计环节,指出院 今后推广应用的研究重点和发展趋势,该设计方案突出的特点为:防爆性能好的高效多管式旋风除尘器的设计,对管网和排风罩的优化防爆设计,多层次的防爆抑爆设施的设计。  相似文献   
236.
为了探明草本植物两两组合培养对其重金属富集特性的影响,寻求修复V、Pb、Cd、Cr复合污染的最佳草本植物组合模式,在V、Pb、Cd、Cr 4种重金属〔ρ分别为14.0、0.8、6.0、4.0 mg/L〕共存的水培条件下,研究蒌蒿(Artemisia selengensis turcz)、三叶草(Trifolium repens)、鱼腥草(Houttuynia cordata)和紫花苜蓿(Medicago sativa) 4种草本植物两两组合培养时的重金属富集特性,以及对植物生物量、重金属富集量和转运系数的影响. 结果表明:4种草本植物两两组合培养会在不同程度上影响植物的重金属富集特性,在重金属富集能力方面,蒌蒿、鱼腥草和紫花苜蓿分别与三叶草组合培养时,其地上部分w(Cr)分别比单独培养时提高约157%、303%、639%;两两组合培养时,紫花苜蓿可促进蒌蒿、鱼腥草和三叶草对Pb的吸收. 在重金属转移能力方面,效果最突出的是“三叶草‖紫花苜蓿”组合模式,其中三叶草对V、Pb、Cd、Cr 4种重金属的转运系数分别是单独培养时的1.19、2.52、22.60和1.67倍;对不同组合模式下植物地上部分重金属提取量的分析结果显示,“三叶草‖紫花苜蓿”组合模式对V、Pb、Cd、Cr 4种重金属的提取量均较高,分别为1 555、1 688、473、482 mg/kg,表明该组合模式能够有效缓解地表径流对附近土壤造成的叠加污染. 因此,水培条件下不同草本植物两两组合培养会改变植物的重金属富集特性,并且与植物种类有关.   相似文献   
237.
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   
238.
The purpose of this study was to develop a technology that can convert biogas to synthesis gas (SynGas), a low-emission substituted energy, using a non-thermal-pulsed plasma method. To investigate the characteristics of SynGas production from simulated biogas, the reforming characteristics in relation to variations in pulse frequency, biogas component ratio (C3H8/CO2), vapor flow ratio (H2O/total flow rate [TFR]), biogas velocity, and pulse power were studied. A maximum conversion rate of 49.1% was achieved for the biogas when the above parameters were 500 Hz, 1.5, 0.52, 0.32 m/sec, and 657 W, respectively. Under the above conditions, the dry basis mole fractions of the SynGas were as follows: H2 = 0.645, CH4 = 0.081, C2H2 = 0.067, C3H6 = 0.049, CO = 0.008 and C2H4 = 0.004. The ratio of hydrogen to the other intermediates in the SynGas (H2/ITMs) was 3.1.  相似文献   
239.
张燕  刘颖  韦斯  于红霞 《能源环境保护》2003,17(5):16-17,24
论述了我国的环境监测和食品安全加入WTO之后所受的影响,存在的问题,面临的严峻挑战及应采取的对策。  相似文献   
240.
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   
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