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481.
482.
Jinyang Chen Zhi Li Lujiang Jin Pei Ni Guiyang Liu Haibo He Jianqiu Zhang Junping Dong Ruyi Ruan 《Journal of Material Cycles and Waste Management》2010,12(4):321-325
Depolymerization of nylon 6 to produce ε-caprolactam using an environmentally friendly heteropoly acid catalyst was studied
at temperatures between 553 and 603 K in water. The products of depolymerization were analyzed qualitatively and quantitatively
by means of mass spectrometry and high-performance liquid chromatography. The results showed that the depolymerized product
was mainly ε-caprolactam with a little 6-aminocaproic acid and oligomers. The phosphotungstic heteropoly acid used as a catalyst
can improve the hydrolysis rate and yield of ε-caprolactam. The optimum hydrolysis conditions for ε-caprolactam yield were
as follows: phosphotungstic heteropoly acid content, 3%; reaction temperature, 573 K; and reaction time, 85 min. Under these
conditions, the yield of ε-caprolactam was 77.96%. In the temperature range 553–603 K, the activation energy of 3% phosphotungstic
heteropoly acid-catalyzed depolymerization was evaluated as 77.38 kJ/mol, which is lower than the 86.64 kJ/mol value for no
catalyst. 相似文献
483.
Liying Sun Jinren Ni Alistair G.L. Borthwick 《Journal of environmental management》2010,91(4):1021-1031
This paper presents an approach for rapid assessment of sustainability for Mainland China based on a multilayer index system. Efficient assessment is conducted with the basic mapping units at county and city levels. After evaluating a comprehensive sustainable development index, SDI, for each unit, five rankings of sustainability are determined, and a zonation map produced. Regional characteristics and differences are interpreted through macro-analysis of the spatial variation in SDI. A sensitivity analysis is performed by which the weights of the sub-indices are altered by ±20%, and SDI re-evaluated; the resulting grades remain the same, thus confirming the robustness of the technique. Moreover, the accuracy of the proposed approach is indirectly validated by comparison with assessment results from an alternative systems analysis method. It is found that major conurbations such as Beijing have relatively high levels of sustainability, whereas provinces in central and western China require investment to improve their sustainability. 相似文献
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485.
Recently, a building-based air quality model system which can predict air quality in front of individual buildings along both
sides of a road has been developed. Using the Macau Peninsula as a case study, this paper shows the advantages of building-based
model system in data capture and data mining. Compared with the traditional grid-based model systems with input/output spatial
resolutions of 1–2 km, the building-based approach can extract the street configuration and traffic data building by building
and therefore, can capture the complex spatial variation of traffic emission, urban geometry, and air pollution. The non-homogeneous
distribution of air pollution in the Macau Peninsula was modeled in a high-spatial resolution of 319 receptors·km−2. The spatial relationship among air quality, traffic flow, and urban geometry in the historic urban area is investigated.
The study shows that the building-based approach may open an innovative methodology in data mining of urban spatial data for
environmental assessment. The results are particularly useful to urban planners when they need to consider the influences
of urban form on street environment. 相似文献
486.
结合重力资料分析认为,江苏地磁异常亦与下扬子地幔流应力场活动相关。南黄海Ms6.1地震前地磁异常有呈象限分布的规律,并有发生于地磁正负变化梯度带附近的特征;重力变化打破年变规律,出现大于区域场的负异常,且呈梯度变化 相似文献
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488.
双酚A和典型类固醇环境激素迁移转化研究进展 总被引:5,自引:0,他引:5
近年来有关环境激素污染的认知、研究与防治已经开始受到全球的重视,其中双酚A(BPA)和类固醇是环境中检出频率较高的几种环境激素.国外有关BPA和类固醇环境激素的调查和其迁移转化的研究已经广泛展开,但我国仍处于起步阶段.综述了国内外BPA和两种典型类固醇激素17β-雌二醇(E2)和17α-乙炔基雌二醇(EE2)的研究进展,介绍了其基本性质、用途、危害、环境中浓度和其迁移转化规律;指出为了阐明BPA、E2和EE2在环境中危害,有关其吸附、生物降解和光降解等迁移转化规律,及各迁移转化过程之间协同作用与相互影响的研究还有待于进一步深入. 相似文献
489.
针对化学强化一级处理系统(CEPT)处理废水时影响因素多,难以进行适当的控制和处理效果的预测等问题,建立起基于BP人工神经网络的CEPT法处理猪场稳定塘废水预测模型,并应用该模型对烧杯试验进行了模拟.结果表明,预测值和实测值吻合较好,模型对COD、总磷、浊度去除率预测的平均相对误差分别为7.5%、4.8%和4.9%.通过对pH值和絮凝剂投药量等可控参数进行优化计算,得到CEPT系统的最佳操作条件和最合理操作条件.该模型的建立为CEPT法处理废水工艺系统实现自动化控制提供了一条简便实用的途径. 相似文献
490.
This paper presents a modification of chemical oxygen demand (COD) monitoring giving a better indication of the pollution level compared with the conventional COD method for rivers with a high content of sediments. The correlation between the sediment organic carbon and COD was investigated using sediments sampled in the middle Yellow River, China. Partitioning of the sediment organic carbon between the water and sediment phases was also investigated using batch experiments, with the sediment concentration varying from 20 to 400 g/L. As a result, the COD modification equations are proposed for both turbid water (mixture of water and sediment) and supematant water (filtrate using a 0.45-microm membrane). The modified COD in turbid water and supernatant water could be 40 and 10% less than the monitored COD values, respectively. These results may have a significant influence on the assessment of water quality class in the Yellow River. 相似文献