全文获取类型
收费全文 | 15441篇 |
免费 | 123篇 |
国内免费 | 98篇 |
专业分类
安全科学 | 338篇 |
废物处理 | 753篇 |
环保管理 | 1705篇 |
综合类 | 3098篇 |
基础理论 | 3414篇 |
环境理论 | 10篇 |
污染及防治 | 4398篇 |
评价与监测 | 1062篇 |
社会与环境 | 819篇 |
灾害及防治 | 65篇 |
出版年
2022年 | 218篇 |
2021年 | 212篇 |
2020年 | 104篇 |
2019年 | 116篇 |
2018年 | 301篇 |
2017年 | 248篇 |
2016年 | 435篇 |
2015年 | 288篇 |
2014年 | 479篇 |
2013年 | 1215篇 |
2012年 | 565篇 |
2011年 | 695篇 |
2010年 | 533篇 |
2009年 | 548篇 |
2008年 | 677篇 |
2007年 | 737篇 |
2006年 | 645篇 |
2005年 | 488篇 |
2004年 | 482篇 |
2003年 | 482篇 |
2002年 | 434篇 |
2001年 | 477篇 |
2000年 | 354篇 |
1999年 | 237篇 |
1998年 | 130篇 |
1997年 | 137篇 |
1996年 | 118篇 |
1995年 | 179篇 |
1994年 | 166篇 |
1993年 | 136篇 |
1992年 | 137篇 |
1991年 | 153篇 |
1990年 | 128篇 |
1989年 | 137篇 |
1988年 | 136篇 |
1987年 | 118篇 |
1986年 | 86篇 |
1985年 | 105篇 |
1984年 | 124篇 |
1983年 | 128篇 |
1982年 | 128篇 |
1981年 | 97篇 |
1980年 | 95篇 |
1979年 | 108篇 |
1978年 | 89篇 |
1977年 | 86篇 |
1976年 | 79篇 |
1975年 | 95篇 |
1974年 | 102篇 |
1965年 | 88篇 |
排序方式: 共有10000条查询结果,搜索用时 437 毫秒
351.
Despite the great importance that formaldehyde has in atmospheric photochemistry, few studies have been reported on rain water. In this paper, concentrations of HCHO in rain fractions within rain events are presented. Two sampling sites were chosen: one at Mexico City, a great polluted urban area, and the second at Rancho Viejo, a forested area under the meteorological influence of the city. The results show a general decrease during the early portion of the rain event. This seems to indicate that below-cloud scavenging is the most important mechanism while, from the small variations observed in the latter portion of the rainfall, it is possible to assume within-cloud scavenging as the predominant mechanism. Using the HCHO concentrations in rain water, the mixing ratios were estimated for the two sampling sites. The values were 0.68 ppb and 0.44 ppb at Mexico City and Rancho Viejo, respectively. Measurements at ground level in Mexico City gave a mean HCHO concentration in air of 24 ppb, much higher than the estimated mixing ratio. The high levels of HCHO found in ambient air and in rain water reflect anthropogenic emissions as the potential atmospheric sources. 相似文献
352.
Bacterial leaching of metals from sewage sludge by indigenous iron-oxidizing bacteria 总被引:4,自引:0,他引:4
Bioleaching of metals can be achieved in sewage sludge using Thiobacillus ferrooxidans, which obtains its energy requirements from the oxidation of added ferrous iron. The purpose of this study was to verify the presence of indigenous T. ferroxidans and to evaluate their adaptive capacity and leaching potential. Nineteen sludges (primary, secondary, aerobically and anaerobically digested, oxidation pond) were tested and all of them contained indigenous iron-oxidizing bacteria. The acclimation of these organisms by successive transfers allowed a rise of sludge redox potential over 450 mV and a decrease of sludge pH between 3.8 and 2.2 over a 10-day incubation period. The metal solubilization efficiencies were Cd: 55-98%, Cr: 0-32%, Cu: 39-94%, Mn: 71-98%, Ni: 37-98%, Pb: 0-31% and Zn: 66-98%, were reached with these indigenous strains. The results obtained show that the metal bioleaching may be easily realized by direct acclimation of sludge microflora. 相似文献
353.
354.
The significant processes controlling the fate of particulates are convection an dispersion on one hand, and sedimentation on the other hand. Due to inteparticulated reactions, larger aggregates can be formed from smaller units thus changing the sedimentation characteristics. These phenomena are summarized in a mathematical model whereby hydrodynamic effects as well as the control mechanisms of the dissolved phase are included. A relationship was derived on the basis of energy considerations leading to the formulation of a critical sedimentation velocity of the suspensa, which determines the transport capacity of the flowing system. The sedimentation term is calculated from the above discussed transport capacity, hydro-dynamic parameters and suspending media properties. Aggregation effects are taken into account as an increase of sedimentation velocities of the particles. The equations are solved in a particular computational routine such that the horizontal distribution of suspended solids in a natural system can be describe as function of the above discussed phenomena. The model was tested with in situ-measurements. It was found that the observed processes are described satisfactorily by this model. 相似文献
355.
A disastrous flood in Ibadan City, Nigeria in April 1978 aroused public interest in the Ogunpa river channelization scheme which had earlier been embarked upon by government. A questionnaire survey of 399 residents near the river was designed to examine three issues: (a) the losses sustained and the people's reaction to and perception of the causes of the flood; (b) their perception of the present and future uses of the river; and (c) their perception of the prospects of the channelization scheme.The results show that about 75% of the respondents were affected by the flood; 41% each lost property worth about N2960.00. Yet, many could not hope to move out of the flood zone mainly because of shortage of residential accomodation in the city. The factors given as being responsible for the flood were poor drainage, heavy rains, refuse disposal in the river, shallowness of the river channel and the unplanned layout of streets and buildings. Indeed, the major use of the river has been as a refuse dump, so that it is heavily polluted. Many respondents would like the river to be reclaimed to alleviate some of the socioeconomic problems confronting them. Recreational use of the river was not much considered. Majority of respondents thought the channelization scheme would bring some benefit. But, they are sceptical about its lasting impact unless it is done within the framework of a comprehensive programme of urban land management and protection and the improvement of living conditions in the city. 相似文献
356.
357.
358.
359.
360.