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231.
John M. Graham Jr. Eileen F. Rawnsley G. Millard Simmons Doris H. Wurster-Hill Jonathan P. Park Miguel Marin-Padilla Harte C. Crow 《黑龙江环境通报》1989,9(6):409-419
Seven cases of triploidy were encountered by the Prenatal Diagnosis Program at Dartmouth–Hitchcock Medical Center over an 8-year period through associated pregnancy complications. We describe the characteristic findings that facilitate prenatal diagnosis and management. Our experience includes fetuses with major central nervous system abnormalities (spina bifida aperta, holoprosencephaly) and anterior abdominal wall defects, which are detectable with routine prenatal diagnostic screening examinations (ultrasound and AFP). In addition, we stress the importance of recognizing obstetric complications and associated cystic placental changes, which are quite common among triploid conceptuses. Molar changes associated with triploidy have a more benign prognosis than that associated with diploid moles. Such molar changes may relate to the presence of a diploid paternal chromosome complement. The usefulness of cytofluorometric DNA determinations in helping to confirm a clinical suspicion of triploidy is emphasized. These cases are presented in an effort to facilitate prenatal recognition and management of this common cytogenetic condition and prevent unnecessary Caesarean section deliveries. 相似文献
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234.
酚类物质在棉花对枯萎病抗性中的作用 总被引:6,自引:0,他引:6
分析了枯萎病菌侵染及氟乐灵诱发处理后,棉苗叶片和根茎部组织中可溶性酚和黄酮醇以及不溶性细胞结合酚(胞壁结合简单酚、胞壁结合复杂酚聚合物及胞壁结合黄酮醇)含量的变化.结果表明:抗病品种棉苗组织中酚类物质的含量高于感病品种棉苗中的含量,氟乐灵诱发处理促进了棉苗组织中酚类物质的积累;枯萎病菌侵染可明显提高棉苗体内的酚含量,但抗病品种棉苗及经氟乐灵诱发处理并产生诱导抗性的棉苗受侵后其组织中酚含量的增加幅度更大.由此认为,棉花体内的酚类物质与棉花对枯萎病的抗病性以及由氟乐灵诱发的诱导抗性有关. 相似文献
235.
José Martín Pilar López Marianne Gabirot Kevin M. Pilz 《Behavioral ecology and sociobiology》2007,61(8):1275-1282
In some lizards, female mate choice is influenced by chemicals secreted by males, e.g., via the femoral glands. Secretions
of the femoral glands are under direct androgenic control and vary seasonally with androgen production. However, whether increased
testosterone (T) levels affect the concentration and chemical composition of secretions or their attractiveness to females
is unknown. We manipulated T levels of male Iberian wall lizards, Podarcis hispanica, with silastic implants. Differential tongue-flick rates indicated that females detected and discriminated between femoral
secretions of control and T-implanted males based on chemical cues alone. Females showed greater responses to secretions of
T-males, which might suggest that T increased the concentration of chemical signals. Further analyses by gas chromatography–mass
spectrometry indicated that T supplementation induced qualitative changes in lipid composition of femoral secretions. T-males
had decreased relative proportions of cholesta-5,7-dien-3-ol in secretions, which might be related to the negative effects
of T on the immune system and on lipid metabolism. However, experiments of choice of males’ scent showed that females neither
preferred nor avoided the scent marks of T-males but preferred males that maintained higher proportions of cholesta-5,7-dien-3-ol
in secretions, independently of the experimental manipulation. Thus, because this steroid is negatively affected by T, there
might be trade-offs among increasing T levels to increase the production of chemical secretions, maintain metabolism, and
attract females. 相似文献
236.
Christian Sens Petra Scheidemann Andreas Klunk Dietrich Werner 《Environmental science and pollution research international》1998,5(4):202-208
14C-TNT was used to quantify the uptake rate and metabolic turnover of TNT inPhaseolus vulgaris. Seventeen plants were analysed by a special cell fractionation method with polar and nonpolar solvents and enzymes. We obtained
three cytoplasmic fractions and five cell wall derived fractions. The recovery rate was 72% as measured by liquid scintillation
counting.14C partitioned almost in equal amounts with approximately 50% in the cytoplasm and in the cell wall. The majority of the TNT-metabolites
are present in the cytoplasm as was shown by GC/ ECD and thin layer chromatography. The14C in the cell wall is bound probably resulting in long-term immobilisation of these metabolites. We conclude that plants may
also be a model for nitroaromatic turnover and immobilisation in soil components. 相似文献
237.
该文以泡沫混凝土材料作为外墙自保温材料,结合武汉某住宅建筑实例,借助DeST-h能耗模拟软件,以未保温墙体作为基准模型,通过比较几组不同厚度的自保温墙体,以净现值为评价指标确定了泡沫混凝土自保温墙体的经济厚度;借用minitab16软件的曲线拟合功能,计算分析了泡沫混凝土自保温墙体的最佳经济厚度,为泡沫混凝土作为建筑节能墙体材料进一步发展提供指导性的意见.图2,表3,参7. 相似文献
238.
利用FDS模拟研究走廊中排烟口数量、位置以及挡烟垂壁与缓冲区的结合对高层建筑烟气控制效果的影响,寻找最佳组合烟气控制模式。结果表明,在走廊中部设置1个以排除火灾产生烟气为主的排烟口,在空气幕前方2m处设置1个以排除新鲜空气为主的排气口,并且在排气口后方0.5m处设置1个挡烟垂壁的组合烟气控制模式具有最佳的烟气控制效果。挡烟垂壁离机械排烟口0.5m时,可以有效降低缓冲区及前室的温度和烟气浓度,前室内CO2体积分数下降21.4%,温度下降9℃。当挡烟垂壁离空气幕较近时,走廊内的温度和烟气浓度反而上升。 相似文献
239.
根据外墙保温材料具体的工程参数为依据,对挤塑型聚苯乙烯(XPS)、膨胀型聚苯乙烯(EPS)和聚氨酯(PU)三种材料的燃烧参数进行设定,设定火源为从窗口喷射而出的火焰,运用FDS软件进行数值模拟与分析。经过模拟发现:外墙保温材料在竖向燃烧中,火焰前锋高度呈现抛物线式增长,y=at2+bt+c,前期增长迅速,后期逐渐平稳。火焰前锋速度按照线性变化,vp=αt+β。在整个燃烧过程中,火焰前锋速度平稳的降低。XPS板导热系数最好,各测点的温度上升最慢,EPS板蓄热系数最好,所以其温度曲线最为平稳。 相似文献
240.