全文获取类型
收费全文 | 25262篇 |
免费 | 665篇 |
国内免费 | 4538篇 |
专业分类
安全科学 | 1164篇 |
废物处理 | 1138篇 |
环保管理 | 2878篇 |
综合类 | 10087篇 |
基础理论 | 5099篇 |
环境理论 | 12篇 |
污染及防治 | 7641篇 |
评价与监测 | 1027篇 |
社会与环境 | 791篇 |
灾害及防治 | 628篇 |
出版年
2023年 | 244篇 |
2022年 | 624篇 |
2021年 | 543篇 |
2020年 | 394篇 |
2019年 | 428篇 |
2018年 | 592篇 |
2017年 | 682篇 |
2016年 | 703篇 |
2015年 | 845篇 |
2014年 | 1160篇 |
2013年 | 2220篇 |
2012年 | 1317篇 |
2011年 | 1610篇 |
2010年 | 1154篇 |
2009年 | 1246篇 |
2008年 | 1322篇 |
2007年 | 1162篇 |
2006年 | 1080篇 |
2005年 | 802篇 |
2004年 | 694篇 |
2003年 | 816篇 |
2002年 | 702篇 |
2001年 | 769篇 |
2000年 | 660篇 |
1999年 | 614篇 |
1998年 | 479篇 |
1997年 | 454篇 |
1996年 | 470篇 |
1995年 | 437篇 |
1994年 | 378篇 |
1993年 | 332篇 |
1992年 | 295篇 |
1991年 | 275篇 |
1990年 | 272篇 |
1989年 | 248篇 |
1988年 | 210篇 |
1987年 | 180篇 |
1986年 | 170篇 |
1985年 | 176篇 |
1984年 | 158篇 |
1983年 | 169篇 |
1982年 | 170篇 |
1981年 | 165篇 |
1980年 | 149篇 |
1979年 | 145篇 |
1978年 | 142篇 |
1977年 | 129篇 |
1976年 | 136篇 |
1974年 | 142篇 |
1972年 | 125篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
1引言
防护装备在核、生、化环境下起着防放射性灰尘、防生物细菌和防化学毒剂的作用。防护装备的防护性能检测准确与否。直接影响着防护装备产品的质量乃至使用者的生命安全。防护装备的防护性能受湿度的影响很大,以前,在防护装备的防护性能检测过程中是利用干、湿球温度计来检测测试管路中的湿度。 相似文献
73.
Comparative on Causes and Accumulation of Selenium in the Tree-rings Ambient High-selenium Coal Combustion Area from Yutangba, Hubei, China 总被引:1,自引:0,他引:1
Liu G Zhang Y Qi C Zheng L Chen Y Peng Z 《Environmental monitoring and assessment》2007,133(1-3):99-103
Toxic trace elements emitted during coal combustion are the main sources of air pollution. They are released into the atmosphere
mainly in the forms of fine ash, smoke and flue, and thus adversely affect plant, animal and human health. Selenium is one
of toxic and the most volatile in coal. Large amount of atmospheric emission of selenium, as well as selenium present and
scrubber stockpiles in ash may create serious environmental problems. In the paper, on the basis of investigating the abundance
and distribution of selenium in plant-rings during recent 20 years, the bioaccumulation of selenium is explained that selenium
in plant, which were collected from the village of selenium-rich coal combustion, is much higher than that in plants collected
away from the village of selenium-rich coal combustion. The main origins of selenium are selenium-rich coal combustion and
high-selenium rock weathered. The selenium recycle by food chain and selenium will accumulate and redistribute in environments. 相似文献
74.
Dryland area occupies 37% of the national territory in China. Desertification and other disasters have limited dryland sustainable development. Here we overview the dryland characteristics and desertification status and introduce four regionally optimized eco‐productive paradigms for dryland sustainable development, i.e., the mountain‐oasis paradigm in arid desert; the small watershed‐based paradigm on the Loess Plateau; the integrated animal husbandry paradigm on the Inner Mongolia Steppe and the agro‐pastoral transitional region; and three circle paradigm on the Ordos Plateau. These paradigms are established on the basis of regional landscape patterns and their underlying material and energy flow rules, and different functional belts are determined and capitalized upon with the integrated consideration of regional biogeophysical processes, biogeochemical cycles and biogeosocial relations. These paradigms cannot cover all complex landscape types, but provide theoretical frameworks and practicable models for dryland sustainable development in China. 相似文献
75.
固定化混合菌修复油污染地表水的研究 总被引:5,自引:0,他引:5
从辽河油田受石油污染的河床底泥中筛选出一株芽孢杆菌(Bacillus sp.)和一株黄杆菌(Flavobacterium sp.),采用二次交联化学方法对2株细菌单独及混合固定,分别进行了不同接种量的固定化细菌对油的降解,以及固定化混合菌对环境的耐受性和在自然地表水中对油的降解进行研究,结果表明,在相同时间内固定化混合菌对油的降解效果明显优于固定化单株菌,而且都优于游离菌。固定化混合菌pH在6~10、温度在20~40℃范围内能保持较好的活性。在120 h时,固定化混合菌对自然地表水中油的降解率达94.5%,对地表水中COD的去除率达89.6%。扫描电子显微镜分析显示,固定化载体的微观结构适合细菌的生长,固定化混合菌在载体内部形成高密度的菌群。以上的研究为固定化微生物应用于油污染地表水的生物修复提供了一定的理论基础。 相似文献
76.
Carl W. Chen 《Journal of the American Water Resources Association》2003,39(6):1561-1562
77.
78.
David W. Mehlman 《Conservation biology》1994,8(4):1141-1145
79.
The amount of NO2 and NO produced by the machine smoking of cigarettes was determined for 15 commercial Canadian brands. Average yield of NO was 1.44 μmoles or about 13% of the average reported for American cigarettes. Levels of NO2 were less than 12% of NO and were probably due to the oxidation of NO. In order to assess the contribution of tobacco smoke to levels of NO in ambient air, 5 brands of cigarettes were smoked in 27 cubic meter controlled environment room. Ventilation conditions were either 2.5 or 5.0 air changes per hour (ACH) and each experiment was replicated 3 times for a total of 30 experiments. Ventilation rates of 0.3 and 1.5 ACH were also selected in a second series of experiments in which only one brand of cigarette was smoked. Least squares estimates for the effective ventilation rates were obtained in the usual manner after linearizing the decay portion of the NO time curve. In each of the experiments, the regression explained at least 95% of the variation in the levels of NO with time. Loss of NO due to factors other than ventilation appeared to be constant within experimental error and averaged 2.22 ACH. Equilibrium values for NO were grossly underestimated when results from currently accepted proecedures for smoke analysis were used in modeling the growth and decay of NO. Goodness-of-fit was improved when equilibrium values were estimated based on observed levels in ambient air. This approach may be more suitable for evaluating the potential contribution of cigarette smoke to levels of indoor air pollutants. 相似文献
80.