全文获取类型
收费全文 | 761篇 |
免费 | 39篇 |
国内免费 | 287篇 |
专业分类
安全科学 | 42篇 |
废物处理 | 48篇 |
环保管理 | 81篇 |
综合类 | 418篇 |
基础理论 | 155篇 |
污染及防治 | 267篇 |
评价与监测 | 22篇 |
社会与环境 | 32篇 |
灾害及防治 | 22篇 |
出版年
2023年 | 13篇 |
2022年 | 31篇 |
2021年 | 31篇 |
2020年 | 23篇 |
2019年 | 22篇 |
2018年 | 30篇 |
2017年 | 34篇 |
2016年 | 29篇 |
2015年 | 45篇 |
2014年 | 54篇 |
2013年 | 88篇 |
2012年 | 66篇 |
2011年 | 52篇 |
2010年 | 36篇 |
2009年 | 43篇 |
2008年 | 54篇 |
2007年 | 33篇 |
2006年 | 43篇 |
2005年 | 24篇 |
2004年 | 24篇 |
2003年 | 15篇 |
2002年 | 25篇 |
2001年 | 28篇 |
2000年 | 28篇 |
1999年 | 31篇 |
1998年 | 31篇 |
1997年 | 21篇 |
1996年 | 21篇 |
1995年 | 24篇 |
1994年 | 23篇 |
1993年 | 17篇 |
1992年 | 16篇 |
1991年 | 6篇 |
1990年 | 9篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1981年 | 4篇 |
排序方式: 共有1087条查询结果,搜索用时 390 毫秒
311.
312.
啤酒酵母菌对溶液中锶离子的吸附行为 总被引:1,自引:0,他引:1
利用废弃啤酒酵母菌为生物吸附剂,考察了pH、啤酒酵母菌加入量、锶离子初始浓度、吸附时间等对锶离子吸附行为的影响,并通过红外光谱分析探讨了吸附机制.结果表明:(1)在吸附温度为25℃、pH为4.5、啤酒酵母菌加入量为2.0 g/L、锶离子初始质量浓度为10.0 mg/L、吸附60 min的条件下,啤酒酵母菌对锶离子的吸附基本达到平衡.(2)啤酒酵母菌对锶离子的吸附较好地符合Langmuir和Freundlich吸附等温式,且以Langmuir吸附等温式拟合效果更优.在吸附温度为25℃、pH为4.5、啤酒酵母菌加入量为2.0 g/L、吸附时间为180 min、锶离子初始质量浓度为5.0~250.0 mg/L的条件下,啤酒酵母菌对锶离子的理论饱和吸附量为29.67 mg/g.(3)啤酒酵母菌吸附锶离子前后的红外图谱显示.部分吸收峰发生了位移并且透过率改变.推断在啤酒酵母菌吸附锶离子的过程中,锶离子先与NH2和酰胺基团中的N原子进行配位络合,随后被络合了的锶作为成核位点再吸附更多的锶离子在表面.此外,蛋白质特征谱带--酰胺Ⅰ带和酰胺Ⅱ带吸收峰的透过率也发生变化,可能是啤酒酵母菌蛋白质上的官能团也结合了锶离子. 相似文献
313.
Distributions, sources and risk assessment of polycyclic aromatic hydrocarbons (PAHs) in topsoil at Ji’nan city, China 总被引:2,自引:0,他引:2
Surface soil (0-5 cm) samples from 17 sampling sites including different functional areas at Ji'nan city in Shandong Province of China were collected and analyzed for 16 EPA priority polycyclic aromatic hydrocarbons (PAHs). The total PAH concentrations were in the range from 1.31 mg kg(-1) to 254.08 mg kg(-1) (dry weight), and the average level of total PAHs was 23.25 mg kg(-1). The highest total PAHs concentrations were found in steel and iron plant at industrial areas. The total PAHs concentrations in industrial areas were markedly higher than those in other different functional areas. According to comparing total PAHs concentration in Ji'nan city to that of other urban areas, it was found that total PAHs concentrations were 6 to 137 times higher than other areas because of some specific sampling sites such as steel and iron plant and one main roadside. The results showed that PAHs in topsoil of Ji'nan city were suffered from strong pyrogenic influence, especially in industrial areas. However about 52.9% soil samples were mainly originated from both pyrogenic and petrogenic mixed sources based on Flu/Pyr ratios and Phe/Ant ratios. Furthermore, It was found that all individual PAHs except Fle were significantly correlated (P < 0.01) with LMW, HMW, total PAHs and SOM, and individual PAHs except Fle in soils were significantly correlated (P < 0.01) with each other. The nemerow composite index to assess the environmental quality showed that the soil sample of steel and iron plant in industrial areas and one main roadside were heavy pollution of PAHs, and about 47% soil sampling sites were safety, about 53% soil sampling sites were got different grades of PAHs pollution. 相似文献
314.
315.
316.
高职数学教学必须加强数学思想方法的教学 总被引:1,自引:0,他引:1
代伟 《中国环境管理干部学院学报》2008,18(4):109-111
数学思想方法是数学知识的核心,是数学的精髓和灵魂,是研究数学理论和运用数学解决实际问题的指导思想。本文针对目前高职数学教学中存在的数学思想方法教学重视不够以及教法上随意性的现状,提出通过加强数学史和基本数学思想方法的介绍,以及倡导“问题解决”的教学模式来提高学生的数学素养。 相似文献
317.
Fourteen surface sediment samples were collected from Lanzhou Reach of Yellow River, China in July 2005. The concentrations of 16 priority polycyclic aromatic hydrocarbons (PAHs) were determined by gas chromatography equipped with a mass spectrometry detector (GC-MS). Total concentrations of the PAHs ranged from 464 to 2621 ng/g dry weight. Sediment samples with the highest PAH concentrations appeared at the downstream of Lanzhou City, where there was the biggest wastewater discharge pipeline from Lanzhou Oil Refinery Factory and Lanzhou Chemical Industry Company. Municipal sewage also contributed to the PAH contamination in the sediments. A correlation existed between the sediment organic carbon content (f(oc)) and the total PAH concentrations (r(2)=0.57), suggesting that sediment organic carbon content played an important role in controlling the PAHs levels in the sediments. According to the observed molecular indices, PAHs contamination in Lanzhou Reach of Yellow River originated both from the high-temperature pyrolytic processes and from the petrogenic source, showing a mixed PAH input pattern, which was also confirmed by the results of a principal component analysis (PCA). According to the numerical effect-based sediment quality guidelines (SQGs) of the United States, the levels of PAHs at most studied sites in Lanzhou Reach of Yellow River should not exert adverse biological effects. Although at some sites (such as S10, S12, etc.) one PAH may exceed the effects range low (ERL), individual PAH did not exceed the effects range median (ERM). The results indicated that sediments in all sites should have potential biological impact, but should have no impairment. 相似文献
318.
集成电路产业含氟废水处理工程 总被引:3,自引:0,他引:3
介绍采用三级反应一级沉淀为主体工艺,处理集成电路产业含氟废水的实际应用情况和工程治理效果。实践表明,采用本处理技术,能确保出水水质氟离子浓度达到上海市《污水综合排放标准》(DB31/199-1997)的二级标准,即F-浓度≤10mg/L。 相似文献
319.
采样自行设计、构建的生物脱臭塔对生活污水回用处理系统产生的臭气进行净化,获得良好的效果,在空塔停留时间为92s时2个脱臭塔对氨和硫化氢的净化率均达到80%以上,投加活性污泥的1号塔的净化效果更好,表明接种污泥能够促进臭气的净化,其排气中氨含量已优于厂界一级标准,臭气强度接近无臭水平,沸石吸附及微生物氧化分解可能是其中主要过程机理。脱臭塔净化后排气中硫化氢含量仍然较高,达到稍可感觉出和易感觉的水平,表明脱臭塔对硫化氢的净化作用有待进一步提高。氮氧化物因为进气浓度很低,故净化率仅为37%~51%。 相似文献
320.
We examined the concentration, size distribution, redox state and isotopic composition of plutonium (Pu) in groundwater at the 100K-Area at the U.S. Department of Energy's (DOE) Hanford Site. Total concentrations of Pu isotopes were extremely low (10(-4) to 10(-6) pCi/kg, approximately 10(4) to 10(6) atoms/kg) but measurable for the first time in the 100K-Area wells using mass spectrometric analyses that are much more sensitive than alpha spectroscopy methods used previously. Size fractionation data from two wells suggest that 7-29% of the Pu is associated with colloids, operationally defined here as particles between 1 kDa-0.2 microm in size. These colloids were collected using a 1 kDa cross-flow ultrafiltration (CFF) system developed specifically for groundwater actinide studies to include careful controls both in the field and during processing to ensure in situ geochemical conditions are maintained and size separations can be well characterized. Pu in this colloidal fraction was exclusively in the more reduced Pu(III/IV) form, consistent with the higher affinity of Pu in the lower oxidation states for particle surfaces. While the overall concentrations of Pu were low, the Pu isotopic composition suggests at least two local sources of groundwater Pu, namely, local Hanford reactor operations at the 100K-Area and spent nuclear fuel from the N-reactor, which was stored in concrete pools at this site. Differences between this site and the Savannah River Site (SRS) are noted, since groundwater Pu at the F-Area seepage basin at SRS has been found using these same methods, to be characterized by lower colloidal abundances and higher oxidation states. This difference is not directly attributable to groundwater redox potential or geochemical conditions, but rather the physical-chemical difference in Pu sources, which at SRS appear to be dominated downstream from the seepage basins by decay of 244Cm, resulting in more oxidized forms of 240Pu. There is no clear evidence for colloid facilitated transport of Pu in groundwater at the Hanford Site, since downstream wells have both an order of magnitude lower concentrations of Pu and a lower fractional colloidal distribution. 相似文献