收费全文 | 3831篇 |
免费 | 215篇 |
国内免费 | 1563篇 |
安全科学 | 267篇 |
废物处理 | 233篇 |
环保管理 | 277篇 |
综合类 | 2243篇 |
基础理论 | 683篇 |
污染及防治 | 1424篇 |
评价与监测 | 204篇 |
社会与环境 | 139篇 |
灾害及防治 | 139篇 |
2024年 | 9篇 |
2023年 | 69篇 |
2022年 | 196篇 |
2021年 | 155篇 |
2020年 | 134篇 |
2019年 | 139篇 |
2018年 | 157篇 |
2017年 | 177篇 |
2016年 | 194篇 |
2015年 | 246篇 |
2014年 | 330篇 |
2013年 | 415篇 |
2012年 | 343篇 |
2011年 | 320篇 |
2010年 | 256篇 |
2009年 | 253篇 |
2008年 | 304篇 |
2007年 | 257篇 |
2006年 | 217篇 |
2005年 | 175篇 |
2004年 | 133篇 |
2003年 | 145篇 |
2002年 | 117篇 |
2001年 | 118篇 |
2000年 | 99篇 |
1999年 | 114篇 |
1998年 | 91篇 |
1997年 | 67篇 |
1996年 | 65篇 |
1995年 | 79篇 |
1994年 | 54篇 |
1993年 | 49篇 |
1992年 | 37篇 |
1991年 | 29篇 |
1990年 | 13篇 |
1989年 | 10篇 |
1988年 | 11篇 |
1987年 | 7篇 |
1986年 | 6篇 |
1985年 | 4篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1972年 | 1篇 |
1956年 | 1篇 |
A campaign was conducted to assess and compare the personal exposure in L3 of Tianjin subway, focusing on PM2.5 levels, chemical compositions, morphology analysis, as well as the health risk of heavy metal in PM2.5. The results indicated that the average concentration of the PM2.5 was 151.43 μg/m3 inside the train of the subway during rush hours. PM2.5 concentrations inside car under the ground are higher than those on the ground, and PM2.5 concentrations on the platform are higher than those inside car. Regarding metal concentrations, the highest element in PM2.5 samples was Fe; the level of which is 17.55 μg/m3. OC is a major component of PM2.5 in Tianjin subway. Secondary organic carbon is the formation of gaseous organic pollutants in subway. SEM–EDX and TEM–EDX exhibit the presence of individual particle with a large metal content in the subway samples. For small Fe metal particles, iron oxide can be formed easily. With regard to their sources, Fe-containing particles are generated mainly from mechanical wear and friction processes at the rail–wheel–brake interfaces. The non-carcinogenic risk to metals Cr, Ni, Cu, Zn and Pb, and carcinogenic hazard of Cr and Ni were all below the acceptable level in L3 of Tianjin subway.
相似文献Waterpipe (aka hookah) tobacco smokers are exposed to toxicants that can lead to oxidative DNA and RNA damage, a precursor to chronic disease formation. This study assessed toxicant exposure and biomarkers of DNA [8-oxo-7, 8-dihydro-2′-deoxyguanosine (8-oxodG)] and RNA [8-oxo-7,8-dihydroguanosine (8-oxoGuo)] oxidative damage during smoking of flavored and non-flavored waterpipe tobacco. Thirty waterpipe smokers completed two counterbalanced 2-h lab waterpipe smoking sessions (flavored vs. non-flavored waterpipe tobacco). Urinary concentrations of 8-oxodG and 8-oxoGuo and expired carbon monoxide (eCO) were measured before and after the smoking sessions. A significant increase in the urinary concentrations of 8-oxodG (from 2.12 ± 0.83 to 2.35 ± 0.91 ng/mg creatinine, p = 0.024) and 8-oxoGuo (from 2.96 ± 0.84 to 3.45 ± 0.76 ng/mg creatinine, p = 0.003) were observed after smoking the non-flavored and flavored waterpipe tobacco, respectively. Our results also showed that the mean ± SD of eCO increased significantly after smoking the flavored (from 1.3 ± 1.1 to 20.3 ± 23.6 ppm, p < 0.001) and non-flavored waterpipe tobacco (from 1.8 ± 1.2 to 24.5 ± 26.1 ppm, p < 0.001). There were no significant differences in the means of 8-oxodG (p = 0.576), 8-oxoGuo (p = 0.108), and eCO (p = 0.170) between the flavored and non-flavored tobacco sessions. Smoking non-flavored and flavored waterpipe tobacco leads to oxidative stress and toxicant exposure. Our findings add to the existing evidence about the adverse effects of waterpipe tobacco smoking (WTS) and the need for strong policies to inform and protect young people from the risks of WTS.
相似文献