全文获取类型
收费全文 | 2630篇 |
免费 | 396篇 |
国内免费 | 1330篇 |
专业分类
安全科学 | 212篇 |
废物处理 | 201篇 |
环保管理 | 293篇 |
综合类 | 2383篇 |
基础理论 | 465篇 |
环境理论 | 1篇 |
污染及防治 | 407篇 |
评价与监测 | 237篇 |
社会与环境 | 102篇 |
灾害及防治 | 55篇 |
出版年
2024年 | 21篇 |
2023年 | 131篇 |
2022年 | 205篇 |
2021年 | 216篇 |
2020年 | 184篇 |
2019年 | 184篇 |
2018年 | 131篇 |
2017年 | 205篇 |
2016年 | 107篇 |
2015年 | 143篇 |
2014年 | 299篇 |
2013年 | 293篇 |
2012年 | 356篇 |
2011年 | 303篇 |
2010年 | 253篇 |
2009年 | 202篇 |
2008年 | 145篇 |
2007年 | 157篇 |
2006年 | 150篇 |
2005年 | 106篇 |
2004年 | 74篇 |
2003年 | 76篇 |
2002年 | 55篇 |
2001年 | 59篇 |
2000年 | 64篇 |
1999年 | 38篇 |
1998年 | 20篇 |
1997年 | 20篇 |
1996年 | 25篇 |
1995年 | 23篇 |
1994年 | 20篇 |
1993年 | 16篇 |
1992年 | 10篇 |
1991年 | 15篇 |
1990年 | 11篇 |
1989年 | 12篇 |
1988年 | 4篇 |
1987年 | 8篇 |
1986年 | 1篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1970年 | 1篇 |
排序方式: 共有4356条查询结果,搜索用时 15 毫秒
991.
On the influence of faulting on small-scale soil-gas radon variability: a case study in the Iberian Uranium Province 总被引:2,自引:0,他引:2
In order to evaluate the influence of faulting on the variability of geogenic radon at detailed scale (1:2000), data on gamma ray fluxes, U and Th concentrations in rocks, radon in soil-gas and radon in groundwater were collected in three target areas on the Oliveira do Hospital region (Central Portugal). This region stands on the Iberian Uranium Province, and is dominantly composed of Hercynian granites and metasedimentary rocks of pre-Ordovician age, crosscut by faults with dominant strike N35°E, N55°E and N75°E. Radiometric anomalies are frequent, associated with faults of the referred systems and metasedimentary enclaves; the analytical data confirms that these anomalies are produced by local high uranium contents in rocks and fault-filling materials (n = 34, range 13-724 ppm), while other radiogenic elements are relatively constant (e.g. Th 4-30 ppm). Radon concentration in soil can be extremely high, up to 12,850 kBq m−3 (n = 215), with a large proportion of results above 100 kBq m−3. Unsurprisingly, groundwater also shows high radon concentrations, with observed values in the range 150-4850 Bq.L−1 (n = 17). From the results it is concluded that metasedimentary enclaves, as well as faults, can accumulate uranium from circulating fluids, and as a consequence, strongly locally enhance geogenic radon potential. Due to this fact, for the purpose of land use planning in such uranium-enriched regions, very detailed geological mapping is needed to precisely recognize radon high risk areas. A correlation between radon concentration in soil or in groundwater and gamma ray fluxes was established pointing to the possible use of these fluxes as a first step in assessing geogenic radon potential, at least to geological setting similar to the study area. 相似文献
992.
993.
为分析不饱和聚酯树脂在内衬改造应用中存在的引燃风险,阐述加油站埋地罐内衬改造工艺,测试不饱和聚酯树脂固化放热特性、与玻璃钢摩擦的滚刷及装树脂绝缘桶的表面静电电位。结果表明:不饱和聚酯树脂与固化剂混合后的放热不足以引起树脂自燃;滚刷、树脂与绝缘桶间摩擦可导致桶表面静电位超过7 kV,带电绝缘体表面与金属凸出物间存在静电放电现象、甚至引起挥发苯乙烯局部闪燃风险。油罐内衬改造时需强化通风以及增加静电防护措施,避免静电放电引起罐内燃爆事故。 相似文献
994.
以城市生活垃圾厌氧消化污泥为接种物,考察了初始pH值为5、6、7和8时对泔脚发酵产氢余物中温(36℃)批式厌氧消化的影响。结果表明,当初始pH值低于7时,随着初始pH值的增大,产氢余物的产甲烷能力也随之增大;而当初始pH值高于7时,体系的产沼能力却受到了极大的抑制。结合Gompertz模型拟合结果,初始pH值为7为泔脚发酵产氢余物沼气化的最佳初始pH值,其沼气化的延迟时间λ、产甲烷率、生物气中甲烷的最高体积含量分别为:4.02 d,379.28 mL/g VS,82.2%。厌氧消化结束后,除初始pH值为5的以外,厌氧消化余物的pH值在6.8~6.9之间,这为沼气中甲烷的高体积含量(高于常规厌氧消化的最高甲烷体积含量75%)提供了证据。 相似文献
995.
This research utilized the Ames test to determine the mutagenicity of water treated by advanced processes, including ozonation and granular activated carbon (GAC). Raw water samples for this research included those obtained from the Pan Hsin waterworks as well as samples containing humic acids. Treated samples were collected from the pilot‐scale advanced treatment plant. The Ames test was used to measure the mutagenicity of the water after each treatment process. For the Pan Hsin raw water samples treated with ozone or GAC, it was indicated that, regardless of whether samples were preozonated or not, they all showed a mutagenic potency less than 2 once the S9 enzyme was added. This level of mutagenicity is insignificant. The prepared humic acid samples, on the other hand, demonstrated a significant reduction in mutagenicity after the pre‐ozonation process, indicating that preozonation can lower the degree of mutagenicity. Furthermore, the mutagenicity of the prepared humic acid samples gradually decreased after the advanced treatment process. However, when chlorine was added later to these samples, the mutagenicity increased again. This research shows that the use of O3/GAC processes to treat water can successfully lower mutagenicity, indicating a great potential for applications in the treatment of drinking water. 相似文献
996.
William Hartley Nicholas M. Dickinson 《Environmental pollution (Barking, Essex : 1987)》2010,158(3):649-657
A derelict canal contains an estimated 9800 tonnes of anoxic sediment with highly elevated concentrations of trace elements. Lack of maintenance, reduced water levels and vegetation colonization threaten the stability of pollutants by removing existing waterlogged reduced conditions. A column leaching study of the sediment under increasingly oxidized conditions showed reductions in As mobility but increased heavy metal concentrations. In a reduced state, As mobility was higher (as a consequence of enhanced Fe and organic carbon solubility) whilst heavy metal concentrations in leachates were lower (due to markedly higher pH). Over 10 contiguous wetting and drying cycles, the consequences were profound; all trace elements were continuously leached with enhanced flushing of Fe, As, Zn and Cu. This raises concern over possible mobilization of pollutants to the wider environment, including groundwater. Options for management to stabilize contaminants are discussed that point to the importance of limiting water flow through the sediment. 相似文献
997.
998.
Here we synthesize key findings from a series of experiments to gain new insight on inter-plant competition between juvenile beech (Fagus sylvatica) and spruce (Picea abies) under the influence of increased O3 and CO2 concentrations. Competitiveness of plants was quantified and mechanistically interpreted as space-related resource investments and gains. Stable isotopes were addressed as temporal integrators of plant performance, such as photosynthesis and its relation to water use and nitrogen uptake. In the weaker competitor, beech, efficiency in space-related aboveground resource investment was decreased in competition with spruce and positively related to Δ13C, as well as stomatal conductance, but negatively related to δ18O. Likewise, our synthesis revealed that strong belowground competition for water in spruce was paralleled in this species by high N assimilation capacity. We suggest combining the time-integrative potential of stable isotopes with space-related investigations of competitiveness to accomplish mechanistic understanding of plant competition for resources. 相似文献
999.
Minori Uchimiya Leonid Gorb Mohammad M. Qasim 《Environmental pollution (Barking, Essex : 1987)》2010,158(10):3048-3053
Extensive studies have been conducted in the past decades to predict the environmental abiotic and biotic redox fate of nitroaromatic and nitramine explosives. However, surprisingly little information is available on one-electron standard reduction potentials (Eo(R-NO2/R-NO2−)). The Eo(R-NO2/R-NO2−) is an essential thermodynamic parameter for predicting the rate and extent of reductive transformation for energetic residues. In this study, experimental (linear free energy relationships) and theoretical (ab initio calculation) approaches were employed to determine Eo(R-NO2/R-NO2−) for nitroaromatic, (caged) cyclic nitramine, and nitroimino explosives that are found in military installations or are emerging contaminants. The results indicate a close agreement between experimental and theoretical Eo(R-NO2/R-NO2−) and suggest a key trend: Eo(R-NO2/R-NO2−) value decreases from di- and tri-nitroaromatic (e.g., 2,4-dinitroanisole) to nitramine (e.g., RDX) to nitroimino compound (e.g., nitroguanidine). The observed trend in Eo(R-NO2/R-NO2−) agrees with reported rate trends for reductive degradation, suggesting a thermodynamic control on the reduction rate under anoxic/suboxic conditions. 相似文献
1000.
电子废弃物已成为城市环境的新压力。本文从加强立法、生产者负责制以及建立健康绿色的废旧电子回收体系三方面分析电子废物变废为宝的绿色途径,从而推动电子废物资源化、无害化发展。 相似文献