全文获取类型
收费全文 | 214篇 |
免费 | 27篇 |
国内免费 | 128篇 |
专业分类
安全科学 | 20篇 |
废物处理 | 14篇 |
环保管理 | 14篇 |
综合类 | 200篇 |
基础理论 | 54篇 |
污染及防治 | 53篇 |
评价与监测 | 14篇 |
出版年
2023年 | 2篇 |
2022年 | 2篇 |
2021年 | 8篇 |
2020年 | 10篇 |
2019年 | 8篇 |
2018年 | 9篇 |
2017年 | 5篇 |
2016年 | 9篇 |
2015年 | 10篇 |
2014年 | 17篇 |
2013年 | 16篇 |
2012年 | 24篇 |
2011年 | 16篇 |
2010年 | 24篇 |
2009年 | 29篇 |
2008年 | 28篇 |
2007年 | 39篇 |
2006年 | 39篇 |
2005年 | 20篇 |
2004年 | 10篇 |
2003年 | 14篇 |
2002年 | 5篇 |
2001年 | 1篇 |
2000年 | 4篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1986年 | 1篇 |
排序方式: 共有369条查询结果,搜索用时 62 毫秒
231.
本文以牛皮纸作载体,用浸渍法制备了具有光催化作用的纳米P-TiO2光催化剂,对室内一定浓度的甲醛气体进行了降解实验研究。通过实验探讨了甲醛的初始浓度、催化剂的用量、湿度条件、溶胶pH值和金属离子的掺杂5个影响甲醛降解率的因素,结果采用美国interscan公司生产的4160型甲醛分析仪进行表征。实验结果表明,当甲醛的初始浓度约为1.53mg/m3,P-TiO2用量为11.94g,湿度约为52%,溶胶pH=5.01,掺杂6.00mL 0.20 mol/L Cu2+离子时,甲醛的降解效果最好,最高可达93.50%,甲醛浓度降至0.0994mg/m3,达到了GB/T 18883—2002标准中规定的0.10 mg/m3。 相似文献
232.
233.
基于OMI数据的兰州地区对流层甲醛时空变化研究 总被引:1,自引:0,他引:1
基于OMHCHO遥感数据产品,对兰州地区2006—2016年对流层甲醛柱浓度的时空分布进行了分析,并对与其排放相关的因素进行了探讨,结果表明:2006—2016年对流层甲醛柱浓度整体呈上升趋势,其中2006—2011年甲醛柱浓度增加迅速,最大增长率为21.0%,2012—2016年甲醛柱浓度平缓波动上升,11年中年均增长率为5.4%;空间上甲醛柱浓度整体呈现由兰州市区西部及与其相邻的永登县部分区域向周边区域递增的趋势,2006—2011年表现为浓度级的增加和区域的扩大,2012—2015年浓度级及其区域基本不变,2016年在东南部出现高值甲醛柱浓度区;每年的最高值出现在6—8月份,11年中最大的柱浓度值出现在2011年的7月份,最低值基本出现在2—4月份,11年中最低的柱浓度值出现在2006年的2月份;四季对流层甲醛柱浓度水平为:夏季冬季秋季春季;影响因素中气温和风向对大气中甲醛的生成和分布有着促进作用,兰州地区生产总值及各产业增加值,尤其是工业产值和机动车保有量的增加,与甲醛柱浓度升高密切相关,这些人为因素是对流层中甲醛柱浓度变化的主要原因. 相似文献
234.
高浓度甲醛废水在高温高pH的条件下,通过投加CaO强化氧化剂,实现了高浓度甲醛废水的甲醛快速降解转化.反应条件和投加药量如下:20 000 mg/L浓度的甲醛废水投加固体NaOH量、CaO量分别为2 kg/m 3高浓度甲醛废水和0.6 kg/m 3高浓度甲醛废水,当反应温度为80℃时,控制废水反应的pH值在9.5~10.0左右,当反应时间为30 min后,通过观察反应后废水的颜色和闻废水是否有甲醛的气味判定是否为反应的终点.当反应后的废水无甲醛气味,颜色为红棕色,即可判断为反应的终点,此时甲醛浓度降低到20 mg/L以下,甲醛的去除率为99.9%以上. 相似文献
235.
Ohmichi K Komiyama M Matsuno Y Takanashi Y Miyamoto H Kadota T Maekawa M Toyama Y Tatsugi Y Kohno T Ohmichi M Mori C 《Environmental science and pollution research international》2006,13(2):120-124
Goal, Scope and Background Cadavers for gross anatomy laboratories are usually prepared by using embalming fluid which contains formaldehyde (FA) as
a principal component. During the process of dissection, FA vapors are emitted from the cadavers, resulting in the exposure
of medical students and their instructors to elevated levels of FA in the laboratory. The American Conference of Governmental
Industrial Hygienists (ACGIH) has set a ceiling limit for FA at 0.3 ppm. In Japan, the Ministry of Health, Labour and Welfare
has set an air quality guideline defining two limit values for environmental exposure to FA: 0.08 ppm as an average for general
workplaces and 0.25 ppm for specific workplaces such as an FA factory. Although there are many reports on indoor FA concentrations
in gross anatomy laboratories, only a few reports have described personal FA exposure levels. The purpose of the present study
was to clarify personal exposure levels as well as indoor FA concentrations in our laboratory in order to investigate the
relationship between them.
Methods The gross anatomy laboratory was evaluated in the 4th, 10th and 18th sessions of 20 laboratory sessions in total over a period
of 10 weeks. Air samples were collected using a diffusive sampling device for organic carbonyl compounds. Area samples were
taken in the center and four corners of the laboratory during the entire time of each session (4-6 hours). Personal samples
were collected from instructors and students using a sampling device pinned on each person's lapel, and they were 1.1 to 6
hours in duration. Analysis was carried out using high performance liquid chromatography.
Results and Discussion Room averages of FA concentrations were 0.45, 0.38 and 0.68 ppm for the 4th, 10th and 18th sessions, respectively, ranging
from 0.23 to 1.03 ppm. These levels were comparable to or relatively lower than the levels reported previously, but were still
higher than the guideline limit for specific workplaces in Japan and the ACGIH ceiling limit. The indoor FA concentrations
varied depending on the contents of laboratory sessions and seemed to increase when body cavity or deep structures were being
dissected. In all sessions but the 4th, FA levels at the center of the room were higher than those in the corners. This might
be related to the arrangement of air supply diffusers and return grills. However, it cannot be ruled out that FA levels in
the corners were lowered by leakage of FA through the doors and windows. Average personal exposure levels were 0.80, 0.45
and 0.51 ppm for instructors and 1.02, 1.08 and 0.89 ppm for students for the 4th, 10th and 18th session, respectively. The
exposure levels of students were significantly higher than the mean indoor FA concentrations in the 4th and 10th sessions,
and the same tendency was also observed in the 18th session. The personal exposure level of instructors was also significantly
higher than the indoor FA level in the 4th session, while they were almost the same in the 10th and 18th sessions. Differences
in behavior during the sessions might reflect the differential personal exposure levels between students and instructors.
Conclusion The present study revealed that, if a person is close to the cadavers during the gross anatomy laboratory, his/her personal
exposure level is possibly 2 to 3-fold higher than the mean indoor FA concentration. This should be considered in the risk
assessment of FA in gross anatomy laboratories.
Recommendation and Outlook If the risk of FA in gross anatomy laboratories is assessed based on the indoor FA levels, the possibility that personal
exposure levels are 2 to 3-fold higher than the mean indoor FA level should be taken into account. Otherwise, the risk should
be assessed based on the personal exposure levels. However, it is hard to measure everyone's exposure level. Therefore, further
studies are necessary to develop a method of personal exposure assessment from the indoor FA concentration. 相似文献
236.
利用气相色谱/燃烧/同位素比值质谱(GC/C/IRMS)技术,采用2,4-二硝基苯肼(DNPH)衍生化,初步研究了单体化合物稳定碳同位素方法研究大气甲醛来源问题.根据不同同位素组成的甲醛与DNPH反应,模拟大气采样,具体讨论了甲醛与DNPH衍生化过程的同位素效应及分析方法的重现性与精确度.结果表明,每个甲醛2,4-二硝基苯腙样品分析的最大标准偏差为0.3‰;不同同位素组成的甲醛衍生化产物甲醛2,4-二硝基苯腙与理论值的平均偏差为0.24‰±0.14‰(从0.03‰到0.35‰),小于仪器分析误差0.5‰,该衍生化过程不存在同位素分馏.采用该方法对酒店大厅内外大气甲醛碳同位素组成进行了初步研究,结果表明不同来源的甲醛同位素组成具有显著差异,可以为大气甲醛的来源分析提供非常有效的信息. 相似文献
237.
我国城市当前普遍存在室外大气PM_(2.5)与室内甲醛(FA)联合污染状况,二者均被报道在单独暴露下可以导致肺损伤并诱导和诱发哮喘的急性发作,但其联合污染的具体效应,以及分子机制目前尚不清楚。为探究PM_(2.5)和/或甲醛暴露对小鼠的肺损伤及其可能的机制,分别将雄性Balb/c小鼠分为以下6组:对照组,AZD8055组,PM_(2.5)组,FA组,PM_(2.5)+FA组,PM_(2.5)+FA+AZD8055组。染毒结束后,观察肺组织病理学变化;检测肺组织氧化损伤,活性氧(reactive oxygen species,ROS),还原型谷胱甘肽(glutathione,GSH)和丙二醛(malondialdehyde,MDA)的含量,DNA损伤,DNA-蛋白质交联(DNA-protein crosslink,DPC)系数和8羟基脱氧鸟苷(8-OH-d G)的含量,以及细胞凋亡、半胱氨酸天冬氨酸蛋白酶-3(Caspase-3)的含量。结果表明,当吸入气态甲醛浓度为3 mg·m-3,气道滴注PM_(2.5)浓度为2.5 mg·m L-1时,肺组织出现不同程度的支气管重塑和炎症细胞浸润。ROS显著上升,GSH显著下降,DPC、8-OH-d G以及Caspase-3都显著上升。添加AZD8055后,肺组织损伤效应更加显著。PM_(2.5)复合甲醛的暴露导致小鼠肺损伤具有协同作用,氧化应激及其下游的DNA损伤可能是甲醛联合PM_(2.5)致小鼠肺损伤的一种重要机制。 相似文献
238.
239.
甲醇和甲醛往往同时存在,为了能同时检测它们,采用变色酸光度法对甲醇、甲醛的检测进行了探讨性实验。先用变色酸比色法直接测定甲醛,然后在酸性条件下用高锰酸钾将甲醇氧化成甲醛后再与变色酸反应进行测定,这时的测定值为甲醇与甲醛之总量,扣除甲醛之量后就得到甲醇量。甲醛的最低检出浓度为2mg/L,测定上限为20mg/L,方法的精密度和准确度也比较好。 相似文献
240.
本文研究了水中苯酚,糖醇及甲醛在NKA树脂上的吸附平衡,发现了各组份之间的竞争吸附特点,以及苯酚脱附过程中受到其它二组份的影响情况。 相似文献