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981.
Congbin Xu Wenjie Yang Weijiang Liu Hongliang Sun Chunlei Jiao Ai-jun Lin 《环境科学学报(英文版)》2018,30(5):14-22
Zero-valent iron (ZVI) was loaded on expanded graphite (EG) to produce a composite material (EG-ZVI) for efficient removal of hexavalent chromium (Cr(VI)). EG and EG-ZVI were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy and Brunauer–Emmett–Teller (BET) analysis. EG-ZVI had a high specific surface area and contained sub-micron sized particles of zero-valent iron. Batch experiments were employed to evaluate the Cr(VI) removal performance. The results showed that the Cr(VI) removal rate was 98.80% for EG-ZVI, which was higher than that for both EG (10.00%) and ZVI (29.80%). Furthermore, the removal rate of Cr(VI) by EG-ZVI showed little dependence on solution pH within a pH range of 1–9. Even at pH 11, a Cr(VI) removal rate of 62.44% was obtained after reaction for 1 hr. EG-ZVI could enhance the removal of Cr(VI) via chemical reduction and physical adsorption, respectively. X-ray photoelectron spectroscopy (XPS) was used to analyze the mechanisms of Cr(VI) removal, which indicated that the ZVI loaded on the surface was oxidized, and the removed Cr(VI) was immobilized via the formation of Cr(III) hydroxide and Cr(III)–Fe(III) hydroxide/oxyhydroxide on the surface of EG-ZVI. 相似文献
982.
应用320米塔上第一次获得的垂直风速脉动量的垂直分布资料,根据湍流扩散统计理论并结合半经验近似,讨论由欧拉参数估算边界层下层扩散参数的主要方法,得到了湍流统计特征量K_(?)、σ_w及ε随高度和稳定度变化的经验关系,为北京地区大气扩散规律研究及污染模式的建立提供实验基础. 相似文献
983.
西南地区干旱规律与节水农业发展问题 总被引:11,自引:1,他引:11
除西藏以外的中国西南地区人口、耕地和农林牧渔总产值分别占全国的19.2%、19.1%和14.9%,是我国十分重要且潜力巨大的农产品生产基地。干旱是制约本区农业发展的重要因素。文章分析了西南地区的干旱特征,揭示出该区季节性干旱严重、区域性干旱突出、干旱类型多、连旱频率大的干旱规律,提出对农业生产危害最严重的干旱类型是春旱、夏旱和伏旱。从自然和经济开发的角度,分析了该区干旱的主要成因是降雨分布不均、水资源可利用率低、水土流失严重和水利工程滞后。在此基础上,提出了提高降雨利用率、提高水资源开发程度及大力发展生物节水技术的对策,特别是农业结构调整、抗旱作物选用、节水农耕农艺技术和发展经济植物篱(埂)等生物节水技术。 相似文献
984.
农村产业结构调整问题研究 总被引:2,自引:0,他引:2
姚阳 《湖南环境生物职业技术学院学报》2006,12(1):65-68
本文首先对农村产业结构调整的相关概念进行了阐述.其次,分析和归纳了判断农村产业结构合理化的标准以及农村产业结构变动的影响因素. 相似文献
985.
The extraction of K+ and SiO2 from silicate minerals by Bacillus mucilaginosus in liquid culture was studied in incubation experiments. B. mucilaginosus was found to dissolve soil minerals and mica and simultaneously release K+ and SiO2 from the crystal lattices. In contrast, the bacterium did not dissolve feldspar. B. mucilaginosus also produced organic acids and polysaccharides during growth. The polysaccharides strongly adsorbed the organic acids and attached to the surface of the mineral, resulting in an area of high concentration of organic acids near the mineral. The polysaccharides also adsorbed SiO2 and this affected the equilibrium between the mineral and fluid phases and led to the reaction toward SiO2 and K+ solubilization. These two processes led to the decomposition of silicate minerals by the bacterium. 相似文献
986.
Heavy metals associated with reduced sulfur in sediments from different deposition environments in the Pearl River estuary, China 总被引:3,自引:0,他引:3
Distribution of acid volatile sulfur (AVS) and the simultaneously extracted metals (SEM: Cu, Pb, Zn, Cd, Ni) in sediment profiles has been studied at five sites in Pearl River estuary, China. Of the five sampling locations, Nos.1 and 2 are in the middle shoal, Nos.3 and 4 in the west shoal and No. 5 locates to the south of the estuary. The AVS content in the sediments of the middle shoal varies in a small range (0.25–4.06 μmol g−1), while that of west shoal increases with depth from 0 to ultimately 26.09 μmol g−1. The SEM concentration in the sediment profiles at location Nos. 1, 2 and 5 is generally in the range of 0.95±0.2 μmol g−1 with a slight upward increase, while that in the sediment of west shallows are much higher (1.43–2.42 μmol g−1) with a significant upward increase, especially in the upper layer of ca. 15 cm. The observed upward increase of SEM content at all the sites implies that heavy metal contamination of sediment in the Pearl River estuary is increasing. Calculations of the excess heavy metal content which is defined by SEM-AVS molar difference suggests that the upper sediment in the Pearl River estuary, especially on the west shallows, could be a source of heavy metal contaminants and may cause toxicity to the benthos. The site-specific distribution patterns in the AVS and SEM profiles were interpreted according to the hydrogeochemistry of deposition environments. 相似文献
987.
净土保卫战和农业农村污染治理攻坚战是污染防治攻坚战的重要组成部分。本文对"十四五"及今后一个时期土壤、地下水和农业农村生态环境保护总体形势进行了分析,研究提出"十四五"目标指标、重点任务和政策措施的建议,提出坚持问题导向、目标导向,坚持分类施策、精准治污,以解决人民群众关心的突出环境问题为重点,实施一批源头预防、风险管控、治理修复重大工程,推进土壤、地下水和农业农村生态保护治理体系与治理能力现代化,为美丽中国建设提供坚实保障。 相似文献
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