首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   4169篇
  免费   346篇
  国内免费   1402篇
安全科学   337篇
废物处理   201篇
环保管理   386篇
综合类   2393篇
基础理论   737篇
污染及防治   1281篇
评价与监测   274篇
社会与环境   178篇
灾害及防治   130篇
  2024年   19篇
  2023年   105篇
  2022年   205篇
  2021年   196篇
  2020年   193篇
  2019年   159篇
  2018年   185篇
  2017年   222篇
  2016年   223篇
  2015年   222篇
  2014年   299篇
  2013年   425篇
  2012年   366篇
  2011年   366篇
  2010年   311篇
  2009年   321篇
  2008年   302篇
  2007年   271篇
  2006年   240篇
  2005年   189篇
  2004年   124篇
  2003年   157篇
  2002年   114篇
  2001年   97篇
  2000年   100篇
  1999年   78篇
  1998年   79篇
  1997年   61篇
  1996年   64篇
  1995年   46篇
  1994年   34篇
  1993年   28篇
  1992年   36篇
  1991年   11篇
  1990年   18篇
  1989年   9篇
  1988年   3篇
  1987年   6篇
  1986年   4篇
  1985年   7篇
  1984年   4篇
  1983年   3篇
  1982年   1篇
  1981年   4篇
  1980年   1篇
  1979年   2篇
  1976年   1篇
  1974年   1篇
  1973年   4篇
  1972年   1篇
排序方式: 共有5917条查询结果,搜索用时 15 毫秒
381.
To investigate the variation of Zn and Cd accumulation and tolerance of Sedum alfredii (a newly reported Zn/Cd hyperaccumulator), field surveys and hydroponic experiments were conducted among three populations of this species: two originating from old Pb/Zn mines in Zhejiang (ZJ) and Hunan (HN) Provinces and one from a "clean" site in Guangdong (GD) Province, China. Under field conditions, up to 12,524 and 12,253 mg kg(-1) Zn, and 1400 and 97 mg kg(-1) Cd in shoots of ZJ and HN plants were recorded respectively. Under hydroponic conditions, ZJ and HN plants accumulated significantly higher Zn and Cd in their leaves and stems, and possessed significantly higher Zn and Cd tolerance than GD plants. Among the two contaminated populations, ZJ plants showed higher Cd tolerance and accumulation (in leaves) than HN plants. The present results indicate that significant differences in Zn and Cd accumulation and tolerance exist in populations of S. alfredii.  相似文献   
382.
采用浸渍法制备了Mn2O3/γ-Al2O3催化剂,在超临界水中催化氧化降解1,5-萘二磺酸,探索了催化剂Mn2O3活性组分负载量、催化剂空速和反应溶液pH对Mn2O3/γ-Al2O3催化剂活性的影响。结果表明:Mn2O3/γ-Al2O3的催化活性在一定范围内随Mn2O3活性组分负载量的增加而提高;在一定范围内,Mn2O3/γ-Al2O3空速越小,模拟废水的COD去除率越高;Mn2O3/γ-Al2O3催化活性在反应溶液呈酸性情况下比碱性时高。  相似文献   
383.
In Asia, limited studies have been published on the association between daily mortality and gaseous pollutants of nitrogen dioxide (NO2), ozone (O3), and sulfur dioxide (SO2). Our previous studies in Wuhan, China, demonstrated long-term air pollution effects. However, no study has been conducted to determine mortality effects of air pollution in this region. This study was to determine the acute mortality effects of the gaseous pollutants in Wuhan, a city with 7.5 million permanent residents during the period from 2000 to 2004. There are approximately 4.5 million residents in Wuhan who live in the city's core area of 201 km2, where air pollution levels are highest, and pollution ranges are wider than the majority of the cities in the published literature. We used the generalized additive model to analyze pollution, mortality, and covariate data. We found consistent NO2 effects on mortality with the strongest effects on the same day. Every 10-microg/m3 increase in NO2 daily concentration on the same day was associated with an increase in nonaccidental (1.43%; 95% confidence interval [CI]: 0.87-1.99%), cardiovascular (1.65%; 95% CI: 0.87-2.45%), stroke (1.49%; 95% CI: 0.56-2.43%), cardiac (1.77%; 95% CI: 0.44-3.12%), respiratory (2.23%; 95% CI: 0.52-3.96%), and cardiopulmonary mortality (1.60%; 95% CI: 0.85-2.35%). These effects were stronger among the elderly than among the young. Formal examination of exposure-response curves suggests no-threshold linear relationships between daily mortality and NO2, where the NO2 concentrations ranged from 19.2 to 127.4 microg/m3. SO2 and O3 were not associated with daily mortality. The exposure-response relationships demonstrated heterogeneity, with some curves showing nonlinear relationships for SO2 and O3. We conclude that there is consistent evidence of acute effects of NO2 on mortality and suggest that a no-threshold linear relationship exists between NO2 and mortality.  相似文献   
384.
Chen A  Lin C  Lu W  Wu Y  Ma Y  Li J  Zhu L 《Chemosphere》2007,70(2):248-255
An investigation into well water quality was carried out in a rural area subject to irrigation with acidic mine water from the Guangdong Dabaoshan Mine, southern China. The results of water pH measurements from 112 wells in two different seasons suggest that the well water has been contaminated to varying degrees in the investigated Shangba floodplain (approximately 11km south of the Guangdong Dabaoshan Mine). There is a trend that well water pH increased southwards, suggesting that the impacts of acidic irrigation water on groundwater decreased with increasing distance to the entry point of acidic irrigation water. Water quality monitoring results of the selected wells show that Cu and Cd in the water exceeded the limits set in the Chinese National Standards for Drinking Water (GB 5749-85) for the wells close to the irrigation water source. If the World Health Organization (WHO) standard was considered, Cd in some wells was almost 10 times as high as the WHO guideline value (0.003mg l(-1)). Water collected from the location closest to the acidic irrigation water source was acutely toxic to the test organism (Daphnia carinata) even after 51 time dilution. It is likely that the extremely high mortality rate of the local population reported for the study area is at least partly related to the high levels of heavy metals, particularly Cd in the drinking well water.  相似文献   
385.
Life cycle assessment (LCA) was applied to performance data from 1997-2002 to evaluate the environmental impacts of the energy input, airborne emission, waterborne emission, and solid waste inventories for Taiwan's electric power plants. Eco-indicator 95 was used to compare the differences among the generation processes and fuel purification. To better understand the environmental trends related to Taiwan's electric power industry, three fuel scenarios were selected for LCA system analysis. Results indicate that there are differences in characteristic environmental impact among the 13 power plants. Scenario simulation provided a basis for minimizing environmental impacts from fuel selection targets. Fuel selection priority should be a gas-fired combined cycle substituted for a coal-fired steam turbine to be more environmentally friendly, particularly in the areas of the greenhouse effect, acidification, winter smog, and solid waste. Furthermore, based purely on economic and environmental criteria, it is recommended that the gas-fired combined cycle be substituted for the oil-fired steam turbine.  相似文献   
386.
Previous studies have suggested that the ongoing global climate change will likely increase the intensity and frequency of extreme weather, such as typhoons. Since the beginning of global warming, it has become necessary to understand the influence of typhoons on air quality. Rare data, especially particulate measurements data could be used to establish the relationship between the air pollution and typhoons. One of main limiting factors is that most of the previous chemical analyses of particulates used a relatively long sampling time, which could dilute the temporal impact of particulate characteristics and their sources. This work, depending more time-resolved measurements, focus on the characteristics and sources of high particulate matter levels and the influence of typhoons and the Pacific high system. Depending on the measurements, two pollutant groups were clearly identified in this work. The first pollutant group was the emissions from neighboring riverbeds under the strong circulation of the typhoon in the driest season and characterized as high coarse particle concentrations with high mass fraction of Ca2+. The second pollutant group was characterized as the formation and transport of secondary particles with prevalent ions of NH4+, NO3?, and SO42? and occurred in the sea-land breeze circulation under the influence the Pacific high system.  相似文献   
387.
周林 《干旱环境监测》1992,6(3):139-145
通过对伊犁地区部分矿泉水水质分析,展示了该地区矿泉水中微量元素含量及其分布的特点,为今后开发和利用水地区的矿泉资源提供了一定的科学依据.  相似文献   
388.
一株贫营养异养硝化-好氧反硝化菌的筛选及脱氮特性   总被引:5,自引:0,他引:5  
为了探究并优化菌剂应用于微污染水源水体修复的机制和条件,主要针对水库沉积物内筛选出的贫营养好氧反硝化菌进行了菌种鉴定及脱氮特性研究,考察菌株在不同环境条件下的脱氮效果,明确了该菌株的最适宜生长条件,并基于水库水体中贫营养条件对菌株进行水源水库原水的驯化培养试验研究,以期实现该菌株对微污染水源水库原水中氮源污染物的脱除,为原位投菌技术实际工程应用提供理论依据。从微污染水源水库沉积物中驯化筛分出一株高效异养硝化-好氧反硝化菌A14,通过扫描电镜观察、生理生化特征、16S rRNA基因测序和Biolog GenⅢ鉴定,确定该菌株为革兰氏阴性短杆菌,鉴定为皮特不动杆菌(Acinetobacter pittii)。在好氧条件下,菌株细胞内表达反硝化功能基因napA,以NO3-为唯一氮源进行反硝化作用时,36 h时NO3-去除率为78.89%。以NH4+为唯一氮源时,48 h NH4+去除率为95.25%,TN去除率达80.42%,TOC去除率达98.30%,表明该菌株具有异养硝化-好氧反硝化特性。在改变环境条件过程中,该菌株在以乙酸钠为碳源,温度为30℃,C/N为12,pH为7,接种量为10%时,NO3-去除率最高为86.62%,并且在10℃下脱氮率达到40.18%。在水源水库原水脱氮实验中,接种处理TN去除率为50.95%,NO3-去除率为80.25%。结果表明,菌株A14在微污染水源水体菌剂脱氮修复中具有良好的应用潜力。  相似文献   
389.
A probabilistic analysis was performed on soil arsenic concentration data from 4 brownfield sites at Beijing (Chaoyang and Haidian Districts), involved in environmental assessment studies. The available data sets were processed to provide a statistical characterization of the background populations and differentiate “anomalous data” from the natural range of variation of arsenic concentrations in soil. The site-specific background distributions and the existing wide-scale background values defined for the Beijing area were compared, discussing related implications for the definition of metal contamination soil screening levels (SSLs) in site assessment studies. The statistical analysis of As data sets discriminated site-specific background populations, encompassing 88% to 94% of the sample data, from outliers values, associated with either subsoil natural enrichments or possible anthropogenic releases. Upper Baseline Concentration (UBC) limits (+ 2σ level), including most of the site-specific metal background variability, were derived based on the statistical characterization of the background populations. Sites in the Chaoyang South District area had UBC values in the range 10.4–12.6 mg·kg-1. These ranges provide meaningful SSL values to be adopted for As in local site assessment studies. Using the wide-scale background value for the Beijing area would have erroneously classified most of the areas in the subject sites as potentially contaminated.  相似文献   
390.
Batch sorption experiments were conducted to evaluate the sorption behavior of tetracycline (TC, H3L) on sediments and soils in the presence and absence of cadmium (Cd), as affected by pH and properties of sediments and soils. The results indicated stronger nonlinearity and higher capacity of TC sorption on sediments than on soils. Sorption of TC also strongly depended on environmental factors and sediment/soil properties. Lower pH facilitated TC sorption through a cation exchange mechanism, which also took place at pH values above 5.5, where TC existed as a zwitterion (H2L0) or anions (HL- and L2-). When pH was above 7, however, ligand-promoted dissolution of TC might occur due to TC weakening the Al-O bond of aluminum oxide and the Fe-O bond of iron oxide. Natural organic matter (NOM) plays a more important role in TC sorption than cation exchange capacity (CEC) and clay contents. The presence of Cd (II) increased TC sorption on both sediments and soils, which resulted from the decrease of equilibrium solution pH caused by Cd2+ exchange with H+ ions of sediment/soil surfaces. The increase of TC sorption was also related to the formation of TC-Cd complexes, where Cd2+ acted as a bridge between the sediment/soil and TC.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号