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   737篇
  免费   19篇
  国内免费   18篇
安全科学   24篇
废物处理   62篇
环保管理   94篇
综合类   66篇
基础理论   175篇
环境理论   2篇
污染及防治   265篇
评价与监测   50篇
社会与环境   16篇
灾害及防治   20篇
  2022年   10篇
  2021年   9篇
  2020年   4篇
  2019年   10篇
  2018年   18篇
  2017年   26篇
  2016年   22篇
  2015年   19篇
  2014年   24篇
  2013年   68篇
  2012年   44篇
  2011年   40篇
  2010年   31篇
  2009年   40篇
  2008年   51篇
  2007年   55篇
  2006年   36篇
  2005年   28篇
  2004年   31篇
  2003年   29篇
  2002年   18篇
  2001年   17篇
  2000年   9篇
  1999年   10篇
  1998年   7篇
  1997年   3篇
  1996年   6篇
  1995年   4篇
  1994年   6篇
  1993年   6篇
  1992年   3篇
  1991年   6篇
  1990年   4篇
  1989年   6篇
  1988年   6篇
  1987年   7篇
  1986年   5篇
  1985年   3篇
  1984年   3篇
  1983年   5篇
  1981年   2篇
  1979年   7篇
  1978年   5篇
  1977年   4篇
  1974年   2篇
  1973年   2篇
  1972年   3篇
  1971年   3篇
  1970年   5篇
  1967年   3篇
排序方式: 共有774条查询结果,搜索用时 15 毫秒
21.
In this study, the physicochemical properties of the char of Indonesian SM coal following heat treatment at various temperatures were evaluated using X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and morphological and specific surface area analysis. Based on these analyses, heat treatment of coal was determined to be the most effective in increasing the coal rank. In the XPS analysis, the C-O and C-O-C groups and quaternary-N species were found to be of a lower grade coal when the pretreatment temperature decreased, meanwhile the C-C group and pyridinic species increased. In the FT-IR analysis, the collapse of the C-O and C-O-C group was observed due to the collapse of the ether group. In SEM and Brunauer-Emmett-Teller (BET) analysis, a decrease in the ether group was shown to be accompanied with the formation of micropores.  相似文献   
22.
Can we develop land use policy that balances the conflicting views of stakeholders in a catchment while moving toward long term sustainability? Adaptive management provides a strategy for this whereby measures of catchment performance are compared against performance goals in order to progressively improve policy. However, the feedback loop of adaptive management is often slow and irreversible impacts may result before policy has been adapted. In contrast, integrated modelling of future land use policy provides rapid feedback and potentially improves the chance of avoiding unwanted collapse events. Replacing measures of catchment performance with modelled catchment performance has usually required the dynamic linking of many models, both biophysical and socio-economic—and this requires much effort in software development. As an alternative, we propose the use of variable environmental intensity (defined as the ratio of environmental impact over economic output) in a loose coupling of models to provide a sufficient level of integration while avoiding significant effort required for software development. This model construct was applied to the Motueka Catchment of New Zealand where several biophysical (riverine water quantity, sediment, E. coli faecal bacteria, trout numbers, nitrogen transport, marine productivity) models, a socio-economic (gross output, gross margin, job numbers) model, and an agent-based model were linked. An extreme set of land use scenarios (historic, present, and intensive) were applied to this modelling framework. Results suggest that the catchment is presently in a near optimal land use configuration that is unlikely to benefit from further intensification. This would quickly put stress on water quantity (at low flow) and water quality (E. coli). To date, this model evaluation is based on a theoretical test that explores the logical implications of intensification at an unlikely extreme in order to assess the implications of likely growth trajectories from present use. While this has largely been a desktop exercise, it would also be possible to use this framework to model and explore the biophysical and economic impacts of individual or collective catchment visions. We are currently investigating the use of the model in this type of application.  相似文献   
23.
Hospital wastes are infectious wastes generated in hospitals and need to be disposed in such a way that they do not spread disease. In this experiment, 5, 10, 15 and 20% cow manure (CM) were mixed with hospital wastes (HW), and mixed wastes were subjected to vermicomposting. In control treatment, only HW was used for vermicomposting. Results suggested that significantly (P ≤ 0.05) higher total nitrogen content was recorded in vermicomposts when 10% or more CM was added to HW. Higher mineralization rate (decrease in C/N ratio) and cellulase activity is probably responsible for rapid organic matter decomposition (loss of total organic carbon). Ergosterol content i.e., total fungal biomass and cellulolytic fungal population were almost constant initially, but increased in the latter stage of vermicomposting. All the vermicompost samples, prepared in this experiment, showed the absence of coliform bacteria. Therefore, it could be concluded that 10% CM addition with HW was the most economical to obtain best quality vermicompost in terms of nutrient content and microbial status.  相似文献   
24.
ABSTRACT

To test the possible use of composted food waste and wastewater sludge as biofilters to treat gas-phase volatile organic compounds (VOCs), batch experiments were conducted with an isolated strain that could degrade aromatic compounds under aerobic conditions. A benzene and trichloroethylene (TCE) mixture was used as the gas-phase pollutant in experiments with composted food waste, sludge, and soil. Under aerobic conditions, benzene was degraded as a primary substrate and TCE was degraded cometabolically, with water contents varying from 6 to 60% (volume of water added/volume of solid). Optimal water content for VOC removal was 12% for the soil, 36% for the composted food waste, and 48% for the sludge.

The extent of VOC sorption and biodegradation at the optimal water content was different for each material. With the same initial VOC concentration, more VOCs were removed by sorption onto the composted food waste and the sludge, while less VOCs were biodegraded in comparison with the results using soil. The reason the biodegradation in the soil was greater may be partly attributed to the fact that, due to less sorption, the aqueous-phase concentration of VOCs, which microorganisms could utilize as a carbon source or cometabolize, was higher. We also speculate that the distribution of microorganisms in each medium affects the rate of biodegradation. A large number of microorganisms were attached to the composted food waste and sludge. Mass transfer of VOCs and oxygen to these microorganisms, which appear to have been heterogeneously distributed in clusters, may have been limited, resulting in hindered biodegradation.  相似文献   
25.
ABSTRACT

A speciated, hourly, and gridded air pollutants emission modeling system (SHEMS) was developed and applied in predicting hourly nitrogen dioxide (NO2) and ozone (O3) levels in the Seoul Metropolitan Area (SMA). The primary goal of the SHEMS was to produce a systemized emission inventory for air pollutants including ozone precursors for modeling air quality in urban areas.

The SHEMS is principally composed of three parts: (1) a pre-processor to process emission factors, activity levels, and spatial and temporal information using a geographical information system; (2) an emission model for each source type; and (3) a post-processor to produce report and input data for air quality models through database modeling. The source categories in SHEMS are point, area, mobile, natural, and other sources such as fugitive emissions. The emission database produced by SHEMS contains 22 inventoried compounds: sulfur dioxide, NO2, carbon monoxide, and 19 speciated volatile organic compounds. To validate SHEMS, the emission data were tested with the Urban Airshed Model to predict NO2 and O3 concentrations in the SMA during selected episode days in 1994. The results turned out to be reliable in describing temporal variation and spatial distribution of those pollutants.  相似文献   
26.
Abstract

The total alkaloid content and individual alkaloid composition were determined by colorimetry and high performance liquid chromatography, respectively, for Canadian triticale and barley ergot (Claviceps purpurea). The total alkaloid content was highly variable between individual sclerotia from the same or different sources and ranged from 0.042 to 0.752% for triticale and from 0.082 to 1.04% for barley; average values were 0.239% for Ottawa triticale, 0.289% for Prairie triticale, and 0.264% for barley. Ergocristine and its isomer ergocristinine were the major constituents in both grains. On average, Canadian ergot pooled from rye, wheat, triticale, and barley consists of ergocristine (31%), ergocristinine (13%), ergocristinine (13%), ergotamine (17%), ergotaminine (8%), ergocryptine (5%), ergocryptinine (3%), ergo‐metrine (5%), ergometrinine (2%), ergosine (4%), ergosinine (2%), ergocornine (4%), ergocorninine (2%), and unidentified alkaloids (3%) and an average total alkaloid content of 0.236%. With the exception of rye and barley ergot from the maritime regions, Canadian rye, wheat, triticale, and barley ergot is fairly uniform in individual alkaloid composition.  相似文献   
27.
The various aspects of two similar but indeed different air pollution problems are discussed. Both fugitive emissions (industrial) and fugitive dust emissions represent problems affecting attainment of national standards. Both are difficult to quantify so as to determine the relative magnitude of the problem. Both have been generally overlooked in the past in relation to developing an effective and widespread air pollution control program. Both problems will generally require the use of non-conventional air pollution control measures. Both are also becoming the subject of more intensive investigation as more knowledge is being gathered to implicate such emissions as significant air pollution problems.  相似文献   
28.
We characterize the monthly variation in (1 → 3)-β-d-glucan concentration measured over the course of 1 year, and we evaluate the characteristics of size selection using a two-stage cyclone sampler. The (1 → 3)-β-d-glucan concentrations were measured in four bio-related laboratories. A total of 156 samples were collected using a new two-stage cyclone sampler. Analysis of (1 → 3)-β-d-glucan was performed using the kinetic Limulus amebocyte lysate assay. The study showed that airborne (1 → 3)-β-d-glucan concentrations were significantly higher in laboratory D (mean ± SD 1,105?±?1,893 pg/m3) and in the spring (5,458 pg/m3). The highest concentration of (1 → 3)-β-d-glucan occurred in the spring, particularly in May.  相似文献   
29.
Abstract

Combustion of spent vacuum residue hydrodesulfurization catalyst and incineration of paper sludge were carried out in thermo-gravimetric analyzer and an internally circulating fluidized-bed (ICFB) reactor. From the thermogravimetric analyzer-differential thermo-gravimetric curves, the pre-exponential factors and activation energies are determined at the divided temperature regions, and the thermo-gravimetric analysis patterns can be predicted by the kinetic equations. The effects of bed temperature, gas velocity in the draft tube and annulus, solid circulation rate, and waste feed rate on combustion efficiency of the wastes have been determined in an ICFB from the experiments and the model studies. The ICFB combustor exhibits uniform temperature distribution along the bed height with high combustion efficiency (>90%). The combustion efficiency increases with increasing reaction temperature, gas velocity in the annulus region, and solid circulation rate and decreases with increasing waste feed rate and gas velocity in the draft tube. The simulated data from the kinetic equation and the hydrodynamic models predict the experimental data reasonably well.  相似文献   
30.
A high prevalence of intersex or testicular oocytes (TO) in male smallmouth bass within the Potomac River drainage has raised concerns as to the health of the river. Studies were conducted to document biomarker responses both temporally and spatially to better understand the influence of normal physiological cycles, as well as water quality and land-use influences. Smallmouth bass were collected over a 2-year period from three tributaries of the Potomac River: the Shenandoah River, the South Branch Potomac and Conococheague Creek, and an out-of-basin reference site on the Gauley River. The prevalence of TO varied seasonally with the lowest prevalence observed in July, post-spawn. Reproductive maturity and/or lack of spawning the previous spring, as well as land-use practices such as application of manure and pesticides, may influence the seasonal observations. Annual, seasonal, and site differences were also observed in the percentage of males with measurable concentrations of plasma vitellogenin, mean concentration of plasma vitellogenin in females, and plasma concentrations of 17β-estradiol and testosterone in both sexes. Bass collected in the South Branch Potomac (moderate to high prevalence of TO) had less sperm per testes mass with a lower percentage of those sperm being motile when compared to those from the Gauley River (low prevalence of TO). An inverse relationship was noted between TO severity and sperm motility. An association between TO severity and wastewater treatment plant flow, percent of agriculture, total number of animal feeding operations, the number of poultry houses, and animal density within the catchment was observed.  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