全文获取类型
收费全文 | 14176篇 |
免费 | 202篇 |
国内免费 | 164篇 |
专业分类
安全科学 | 485篇 |
废物处理 | 678篇 |
环保管理 | 2429篇 |
综合类 | 1563篇 |
基础理论 | 3659篇 |
环境理论 | 7篇 |
污染及防治 | 3792篇 |
评价与监测 | 1013篇 |
社会与环境 | 822篇 |
灾害及防治 | 94篇 |
出版年
2023年 | 59篇 |
2022年 | 118篇 |
2021年 | 121篇 |
2020年 | 92篇 |
2019年 | 125篇 |
2018年 | 212篇 |
2017年 | 220篇 |
2016年 | 333篇 |
2015年 | 267篇 |
2014年 | 329篇 |
2013年 | 1247篇 |
2012年 | 460篇 |
2011年 | 670篇 |
2010年 | 534篇 |
2009年 | 570篇 |
2008年 | 705篇 |
2007年 | 709篇 |
2006年 | 625篇 |
2005年 | 510篇 |
2004年 | 494篇 |
2003年 | 544篇 |
2002年 | 478篇 |
2001年 | 574篇 |
2000年 | 430篇 |
1999年 | 284篇 |
1998年 | 205篇 |
1997年 | 193篇 |
1996年 | 207篇 |
1995年 | 231篇 |
1994年 | 185篇 |
1993年 | 160篇 |
1992年 | 191篇 |
1991年 | 160篇 |
1990年 | 180篇 |
1989年 | 170篇 |
1988年 | 123篇 |
1987年 | 122篇 |
1986年 | 107篇 |
1985年 | 127篇 |
1984年 | 130篇 |
1983年 | 130篇 |
1982年 | 117篇 |
1981年 | 125篇 |
1980年 | 98篇 |
1979年 | 88篇 |
1978年 | 67篇 |
1977年 | 69篇 |
1976年 | 60篇 |
1975年 | 66篇 |
1973年 | 61篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
941.
Removal of insoluble chloride from bottom ash for recycling 总被引:2,自引:0,他引:2
In order to recycle bottom ash and use it as raw material for cement production, the removal of insoluble chloride was investigated by testing various washing techniques. The present work is also focused on investigating the properties of insoluble chlorides and determining the conditions for dissolving these compounds in order to reduce the chlorine content to the required level, i.e., less than 0.1 wt%. Within this framework, the effect of washing with water and CO2 bubbling was investigated, because the main insoluble chloride found in bottom ash, i.e., Friedel's salt, can be dissolved by CO2. Then, in order to better understand the removal of Cl, Friedel's salt was artificially synthesized by hydration and then the effect of CO2 bubbling was investigated. If all chlorides in the ash are converted into Friedel's salt by hydration, all chlorides can then be dissolved by CO2 bubbling. In addition, the effect of pH on removing the remaining insoluble chlorides was investigated by washing the ash with sulfuric acid solution. It was found that the most effective technique to reduce the Cl content to less than 1000 ppm was washing with sulfuric acid solution, while keeping the pH value at less than 4. By using this method, Friedel's salt and other insoluble chlorides were dissolved. 相似文献
942.
943.
944.
945.
John M. Onyari Francis Mulaa Joshua Muia Paul Shiundu 《Journal of Polymers and the Environment》2008,16(3):205-212
In this study, the biodegradation of PLA films using microorganisms from Lake Bogoria (Kenya) were investigated. The biodegradation
tests done using certain strains of thermophilic bacteria showed faster biodegradation rates and demonstrated temperature
dependency. The biodegradation of the PLA films was studied using Gel Permeation Chromatography (GPC) and light microscopy.
The biodegradation of PLA was demonstrated by decrease in molecular weight. The preparation and characterization of PLA/Gum
Arabic blends were also investigated using DSC, TGA, TMA and NMR. In summary, the results obtained in this research show that
PLA films undergo fast biodegradation using thermophiles isolated from Lake Bogoria. The PLA/GA blends studies show it is
possible to prepare films of varying hydrophobic–hydrophilic properties for various applications. 相似文献
946.
K. Pritsch D. Ernst F. Fleischmann S. Gayler T. E. E. Grams A. Göttlein W. Heller N. Koch H. Lang R. Matyssek J. C. Munch M. Olbrich H. Scherb S. Stich J. B. Winkler M. Schloter 《Water, Air, & Soil Pollution: Focus》2008,8(2):139-154
A lysimeter study was performed to monitor effects of elevated ozone on juvenile trees of Fagus sylvatica L. as well as on the plant–soil system. During a fumigation period over almost three growing seasons, parameters related
to plant growth, phenological development and physiology as well as soil functions were studied. The data analyses identified
elevated ozone to delay leaf phenology at early and to accelerate it at late developmental stages, to reduce growth, some
leaf nutrients (Ca, K) as well as some soluble phenolics (hydroxycinnamic acid derivatives, total flavonol glycosides). No
or very weak ozone effects were found in mobile carbon pools of leaves (starch, sucrose), and other phenolic compounds (flavans).
Altered gene expression related to stress and carbon cycling corresponded well with findings from leaf phenology and chemical
composition analyses indicating earlier senescence and oxidative stress in leaves under elevated ozone. Conversely in the
soil system, no effects of ozone were detected on soil enzyme activities, rates of litter degradation and lysimeter water
balances. Despite the fact that the three reported years 2003–2005 were climatically very contrasting including a hot and
dry as well as an extremely wet summer, and also mild as well as cold winters, the influence of ozone on a number of plant
parameters is remarkably consistent, further underlining the phytotoxic potential of elevated tropospheric ozone levels. 相似文献
947.
Sumana Siripattanakul Wanpen Wirojanagud John McEvoy Eakalak Khan 《Water, Air, & Soil Pollution: Focus》2008,8(3-4):257-266
Atrazine biodegradation by immobilized pure and mixed cultures was examined. A pure atrazine-degrading culture, Agrobacterium radiobacter J14a (J14a), and a mixed culture (MC), isolated from an atrazine-contaminated crop field, were immobilized using phosphorylated-polyvinyl
alcohol (PPVA). An existing cell immobilization procedure was modified to enhance PPVA matrix stability. The results showed
that the matrices remained mechanically and chemically stable after shaking with glass beads over 15 days under various salt
solutions and pH values. The immobilization process had a slight effect on cell viability. With the aid of scanning electron
microscopy, a suitable microstructure of PPVA matrices for cell entrapment was observed. There were two porous layers of spherical
gel matrices, the outside having an encapsulation property and the inside containing numerous pores for bacteria to occupy.
J14a and MC were immobilized at three cell-to-matrix ratios of 3.5, 6.7, and 20 mg dry cells/mL matrix. The atrazine biodegradation
tests were conducted in an aerobic batch system, which was inoculated with cells at 2,000 mg/L. The tests were also conducted
using free (non-immobilized) J14a and MC for comparative purpose. The cell-to-matrix ratio of 3.5 mg/mL provided the highest
atrazine removal efficiency of 40–50% in 120 h for both J14a and MC. The free cell systems, for both cultures, presented much
lower atrazine removal efficiencies compared to the immobilized cell systems at the same level of inoculation. 相似文献
948.
A. A. Olajire E. T. Ayodele F. E. Imeokparia 《Environmental monitoring and assessment》1999,57(2):183-194
Samples of compost-amended soil from waste dumping sites in Lagos Metropolis were extracted with dichloromethane (3 × 20 cm3) and the extract was evaporated at 35 °>C. The residue was extracted with 2,2,4-trimethylpentane, and portions of the solution were applied to a column containing silica gel from which aliphatic and aromatic hydrocarbons were eluted with n-hexane and toluene respectively. Analysis of the n-hexane fraction using gas chromatography showed the presence of a mixture of aliphatic hydrocarbons, ranging from C9 to C25, while ultraviolet analysis of the toluene fraction suggested 1,2-benzanthracene; 2,3-benzphenanthrene, chrysene and pyrene as polyaromatic compounds present in samples analyzed. The crude extracts were highly coloured and viscous. Total extractable organic residues in the 2,2,4-trimethylpentane extracts ranged from 36 to 89 mg g-1 of soil. 相似文献
949.
Many environmental surveys require the implementation of estimation techniques to determine the spatial distribution of the variable being investigated. Traditional methods of interpolation and estimation, for example, inverse distance squared and triangulation often ignore features of the data set such as anisotropy which may have a significant impact on the quality of the estimates produced. Geostatistical techniques may offer an improved method of estimation by modelling the spatial continuity of the variable using semi-variogram analysis. The theoretical model fitted to the semi-variogram is then used in the assignation of weighting factors to the samples surrounding the location to be estimated. This paper outlines the results of a comparison between three common estimation methods, polygonal, triangulation and inverse distance squared and a geostatistical method, in the estimation of soil radionuclide activities. The geostatistical estimation method known as kriging performed best over a range of parameters used to test the performance of the methods. Kriging exhibited the best correlation between actual and estimated values, the narrowest error distribution and the lowest overall estimation error. Polygonal estimation was best at reproducing the data set distribution. Conditional bias was evident in all the methods, low values being over-estimated and high values being under-estimated. 相似文献
950.
H. T. Schreuder R. Czaplewski R. G. Bailey 《Environmental monitoring and assessment》1999,56(3):269-291
A forest ecological inventory and monitoring system combining information derived from maps and samples is proposed based on ecosystem regions (Bailey, 1994). The system extends the design of the USDA Forest Service Region 6 Inventory and Monitoring System (R6IMS) in the Pacific Northwest of the United States. The key uses of the information are briefly discussed and expected results are illustrated with examples. The system is flexible, allowing regions based on ecological considerations to be modified. Sampling intensities that are affordable are likely to be insufficient to provide meaningful estimates for key parameters relating to rare and endangered species, watersheds, and other ecological units. Methods are proposed for collecting additional information in follow-up surveys and combining it with relevant information obtained in R6IMS. Near-continuous information on weather and possible pollution variables recorded by instruments at sampling sites is needed to develop meaningful models to understand what is happening in the ecoregions. R6IMS and the proposed additions constitute a dynamic system which will be modified further as data are analyzed. 相似文献