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   314篇
  免费   0篇
  国内免费   9篇
安全科学   17篇
废物处理   19篇
环保管理   46篇
综合类   53篇
基础理论   58篇
污染及防治   87篇
评价与监测   21篇
社会与环境   19篇
灾害及防治   3篇
  2023年   8篇
  2022年   14篇
  2021年   18篇
  2020年   8篇
  2019年   4篇
  2018年   5篇
  2017年   10篇
  2016年   6篇
  2015年   7篇
  2014年   11篇
  2013年   38篇
  2012年   9篇
  2011年   13篇
  2010年   13篇
  2009年   17篇
  2008年   13篇
  2007年   16篇
  2006年   16篇
  2005年   14篇
  2004年   7篇
  2003年   11篇
  2002年   3篇
  2001年   1篇
  2000年   3篇
  1999年   2篇
  1998年   4篇
  1997年   3篇
  1996年   5篇
  1995年   1篇
  1994年   5篇
  1993年   5篇
  1992年   3篇
  1991年   1篇
  1990年   4篇
  1989年   4篇
  1987年   1篇
  1986年   4篇
  1985年   2篇
  1982年   3篇
  1981年   1篇
  1978年   1篇
  1973年   2篇
  1955年   1篇
  1938年   1篇
  1933年   1篇
  1931年   2篇
  1926年   1篇
  1920年   1篇
排序方式: 共有323条查询结果,搜索用时 984 毫秒
81.
Microbial populations in tetra-distilled water collapsed when cultured in a permalloy chamber shielding the populations from the suns and earths electromagnetic field, but thrived when cultured in an ordinary thermostat open to the electromagnetic field. Theoretically, protons in liquid water can be excited at their natural resonance frequencies through Langmuir oscillations and obtain enough kinetic energy to charge the transmembrane potential of a cell. Microbes may be capable of converting this energy into chemical energy to supplement their energy needs.  相似文献   
82.
83.
The Murcia Este Wastewater Treatment Plant is the largest wastewater treatment plant in Murcia (Spain). The plant operators have continuously found pipe blockage and accumulation of solids on equipment surfaces during the anaerobic digestion and post-digestion processes. This work studies the precipitation problems in the Murcia Este Wastewater Treatment Plant in order to locate the sources of precipitation and its causes from an exhaustive mass balance analysis. The DAF thickener and anaerobic digester mass balances suggest that most of the polyphosphate is released during excess sludge thickening. Despite the high concentrations achieved in the thickened sludge, precipitation does not occur at this point due to the low pH. The increases in ammonium and pH during anaerobic digestion cause precipitation to take place mainly inside the digesters and in downstream processes. This study shows that 50.7% of the available phosphate is fixed in the digester of which 52.0% precipitates as ammonium struvite, 39.2% precipitates as hydroxyapatite and the remaining 8.8% is adsorbed on the surface of the solids. Thermodynamic calculations confirm the precipitation of struvite and hydroxyapatite and also confirm that potassium struvite does not precipitate in the anaerobic digesters.  相似文献   
84.
Forty-two families of which the vast majority associated with particles >2000?µm were found. Sediment particle sizes <2000?µm had a detrimental effect on biodiversity. The highest biodiversity was recorded at sites characterised by riffle and run habitats. Although relatively high concentrations of selected metals were present in the sediment, it was largely from geological origin and most probably not bioavailable. No significant correlation was demonstrated between variation in temperature, pH, and electrical conductivity and diversity and abundance of macroinvertebrates. Therefore, it can be concluded that, under these conditions, sediment particle size and biotope availability played a decisive role on the distribution and abundance of macroinvertebrate taxa.  相似文献   
85.
86.
Published estimates for base metal emissions from the copper–nickel industry on the Kola Peninsula are re-examined in the light of (a) chemical data on the composition of the ores; (b) official emission figures for 1994; and (c) modelled emissions based on dry and wet deposition estimates derived from data for snow and rain samples collected in 1994. The modelled emissions, official emission figures and chemical data are mutually compatible for Ni, Cu and Co and show that previously published figures underestimated the emissions of the major elements, Ni and Cu (though within the same order of magnitude) and overestimated the emissions of As, Pb, Sb and Zn by up to several orders of magnitude, in some cases exceeding the calculated total input to the plants. Published estimates have neglected information on the nature and chemistry of the ores processed in metallurgical industries in the Noril'sk area of Siberia and the Urals. Revised emission estimates for 1994, using knowledge of the chemistry of the ores, are proposed: taken with published information on total emissions up to 2000 these data give an indication of emission levels in more recent years.  相似文献   
87.
In common with other technical fields and disciplines, the air pollution area has “information explosion” problems, compounded by the interdisciplinary nature of the field and the current increased emphasis on air pollution and its control. The development of technical information programs to meet these needs is traced, with emphasis on the Air Pollution Technical Infor-mation Center established by the National Air Pollution Control Administration of the Department of Health, Education, and Welfare. The Center is based on a delegation of responsibility by the Office of Science and Technology, Executive Office of the President, and now contains over 12,000 current references, with an acquisition rate of approximately 200 per month. In addition to the U. S. journal literature, particular emphasis is placed on the foreign literature and on U. S. Government research reports. Other programs discussed include the Air Pollution Control Association, Bay Area Air Pollution Control District, Center for Air Environment Studies at Penn State, and centers serving particular industries. Services available from each are described.  相似文献   
88.
89.
A comparative analysis of forest precipitation depositions was performed using pine tree barks as biomonitoring tools and throughfall collectors in pine stands at various test sites in eastern Germany. For the elements sulfate sulfur (SO4-S), nitrate nitrogen (NO3-N), ammonium nitrogen (NH4-N), calcium (Ca), and iron (Fe), regression equations with r2 values between 0.81 and 0.96 were derived, enabling yearly conversion of bark loads to throughfall rates (TFRs) in pine stands (g*m-2*year-1).

Applying this method to a network of 53 measuring sites in Dübener Heide nature park, north of Leipzig, lead to discovering spatial patterns of TFRs for SO4-S, NO3-N, and NH4-N in 1994. Differences between the TFRs of sulfur and nitrogen were traced back to different emission sources and the temporal trend related to major infrastructural changes in that region since 1990. Results suggest that the bark method will be particularly suited to identifying forest precipitation depositions of ecotoxicologically relevant airborne pollutants on regional scales.  相似文献   
90.
Emissions of reduced sulphur compounds (RSCs) from the primary and secondary clarifiers at a Kraft mill were measured for respectively 8 and 22 days using a floating flux chamber. In the primary clarifier, dimethyl disulphide (DMDS) had the highest mean flux (0.83 microg s(-1) m(-2)) among all RSCs, and the mean flux of total reduced sulphur (TRS) was 1.53 microg s(-1) m(-2). At the secondary clarifier, dimethyl sulphide (DMS) had the highest mean flux (0.024 microg s(-1) m(-2)), and the mean flux of total reduced sulphur (TRS) was 0.025 microg s(-1) m(-2). Large variations in fluxes as a function of sampling date were observed in both clarifiers. Emission fluxes of DMS from the secondary clarifier were correlated with temperature in the flux chamber and with the biological and chemical oxygen demands (BOD and COD) of the wastewater. Emission rates of RSCs from the clarifiers were found to be insignificant by comparison with other mill sources.  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