全文获取类型
收费全文 | 29945篇 |
免费 | 2327篇 |
国内免费 | 4685篇 |
专业分类
安全科学 | 3704篇 |
废物处理 | 477篇 |
环保管理 | 5540篇 |
综合类 | 17236篇 |
基础理论 | 3124篇 |
环境理论 | 60篇 |
污染及防治 | 2000篇 |
评价与监测 | 1592篇 |
社会与环境 | 2285篇 |
灾害及防治 | 939篇 |
出版年
2024年 | 158篇 |
2023年 | 582篇 |
2022年 | 891篇 |
2021年 | 1089篇 |
2020年 | 1105篇 |
2019年 | 916篇 |
2018年 | 796篇 |
2017年 | 1256篇 |
2016年 | 1382篇 |
2015年 | 1405篇 |
2014年 | 1417篇 |
2013年 | 1880篇 |
2012年 | 2124篇 |
2011年 | 2188篇 |
2010年 | 1665篇 |
2009年 | 1690篇 |
2008年 | 1220篇 |
2007年 | 1942篇 |
2006年 | 1941篇 |
2005年 | 1730篇 |
2004年 | 1530篇 |
2003年 | 1371篇 |
2002年 | 1160篇 |
2001年 | 1006篇 |
2000年 | 951篇 |
1999年 | 797篇 |
1998年 | 544篇 |
1997年 | 470篇 |
1996年 | 312篇 |
1995年 | 322篇 |
1994年 | 255篇 |
1993年 | 230篇 |
1992年 | 155篇 |
1991年 | 88篇 |
1990年 | 67篇 |
1989年 | 38篇 |
1988年 | 40篇 |
1987年 | 20篇 |
1986年 | 19篇 |
1985年 | 14篇 |
1984年 | 26篇 |
1983年 | 17篇 |
1982年 | 15篇 |
1981年 | 14篇 |
1980年 | 21篇 |
1979年 | 22篇 |
1977年 | 12篇 |
1973年 | 11篇 |
1972年 | 10篇 |
1971年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
Soils from two typical tidal salt marshes with varied salinity in the Yellow River Delta wetland were analysed to determine possible effects of salinity on soil carbon sequestration through changes in soil microbiology. The mean soil respiration (SR) of the salt water–fresh water mixing zone (MZ) was 2.89 times higher than that of the coastal zone (CZ) (4.73 and 1.63?μmol?m?2?s?1, respectively, p?.05), and soil dehydrogenase activity was the main microbial factor influencing SR. In addition to the higher soil microbial biomass, the MZ had more β-Proteobacteria than the CZ, as well as some specific bacteria with strong heterotrophic metabolic activity such as Pseudomonas sp. and Limnobacter sp. that might have led to its higher dehydrogenase activity and respiratory rates. Additionally, the CZ possessed more Halobacteria and Thaumarchaeota with the ability to fix CO2 than the MZ. Significantly lower soil salinity in MZ (4.25?g?kg?1) was suitable for β-Proteobacteria, but detrimental for Halobacteria compared with CZ (7.09?g?kg?1, p?.01), which might lead to the lower microbial decomposition capacity of soils in CZ. As a result, the CZ has a higher soil organic carbon content than the MZ. 相似文献
142.
143.
为了在酸性条件下实现剩余污泥中磷的高效回收,对pH=3时剩余污泥水解酸化过程中氨氮、正磷酸盐和钙镁离子的溶出现象以及磷回收进行了研究分析。结果表明:当pH=3时,所溶出的氨氮、镁离子和钙离子与磷酸盐的摩尔比均大于1,能满足采用鸟粪石沉淀法或者羟磷灰石沉淀法回收磷的要求;但所溶出的钙镁离子的摩尔比大于1,会对鸟粪石沉淀法回收磷的顺利进行有较大影响;有无外加镁剂对磷回收率影响不大。采用改型后的镁型强酸性阳离子交换树脂进行离子交换可以得到较高纯度的鸟粪石沉淀产品,通过XRD检测其纯度为95%以上。 相似文献
144.
基于目前国家建立环境污染责任保险制度的规划需求和河南省当前新发展形势需要,选择以河南省典型高污染、高风险行业(即煤化工行业)为研究对象.在对相关理论进行分析的基础上,识别影响河南省煤化工行业的环境风险因子,并确定指标的评估标准(权重及评分结果).遵照指标体系的建立原则,采用层次分析法,从内在性和外在性两方面因素构建煤化工行业环境风险等级划分指标体系,进一步将评分结果与环境风险等级比对,最终将煤化工行业的环境风险等级划分为5个等级,为河南省环境污染责任保险制度的建立奠定基础. 相似文献
145.
Aree Choodum Panote Thavarungkul Proespichaya Kanatharana 《Journal of environmental science and health. Part. B》2013,48(5):577-583
A simple sample preparation technique was developed for rapid analysis of acetaldehyde residue in Polyethylene Terephthalate (PET) bottles. A laboratory-built heating system was used and coupled with gas chromatography-flame ionization detector (GC-FID) at optimized conditions. The results were a tremendous reduction of the sample preparation time from 24 hours, for the conventional method, to only one hour. The analysis took only 1.5 min with other good analytical performances i.e. a low detection limit, 0.3 ng mL? 1 and a wide linear dynamic range, 0.3 ng mL? 1 to 6.6 μ g mL? 1 with R2 > 0.99.Acetaldehyde residue in freshly blown bottles were analyzed and found in the range of 0.4 to 1.1 ng mL? 1. The results were good agreement with the conventional 24-hour airspace method (P < 0.01). The PET-bottle sampling technique was also developed to minimize the complication of sample transportation and pre-concentration. A purge and trap technique was found to be the most suitable. Then, it was implemented and compared, the results showed no significant difference (P < 0.01) with and without purge and trap. 相似文献
146.
Dust storms frequently occur in Mongolia and in northern China. Each year there are 30 to 120 dusty days in source regions of Mongolia and 14–20 dusty days on the Korean Peninsula. Intense sand storms and associated dust falls produce environmental impacts in East Asia. This paper discusses the environmental degradation in Mongolia and the social, economic and atmospheric impacts of dust storms in the sink area. The impact of dust storms on environmental compartments as well as their direct and indirect consequences to basic resources like water and energy demand and supply is explained. Governments are encouraged to take appropriate action in specified regions. For monitoring dust storms there is a need for international cooperation to combat growing environmental and human security concerns. 相似文献
147.
148.
149.
1994年江淮伏旱及其影响研究 总被引:1,自引:0,他引:1
利用江谁地区18个站点1951~1995年6~8月降水量资料,用Z指数建立了历年夏季旱涝序列,着重对1994年江淮伏旱及其对农业、水资源的影响进行了分析评述,获得了一些有意义的结论。 相似文献
150.