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811.
In a pilot project performed at a fertilizer manufacturing facility, a one‐step chemical oxidation technique successfully treated urea‐ and ammonium‐contaminated groundwater. The oxidation reaction occurred in an 1,100‐gallon batch reactor. The contaminated inflow was buffered by the metered addition of sodium bicarbonate solution and subsequently treated with sodium hypochlorite in an 8:1 weight ratio of Cl2:N. In an instantaneous reaction, the urea and ammo‐nium‐N were completely oxidized to nitrogen gas that was vented to the atmosphere during mixing. The pH of the reactor discharge was ?6.5. Sodium sulfite was used to reduce residual hypochlorite in the reactor effluent to chloride to provide process water with characteristics suitable for discharge. Oxidation rates were similar with different strengths of hypochlorite; however, a 5 to 6 percent sodium hypochlorite (as Cl2) solution was the most stable. © 2005 Wiley Periodicals, Inc. 相似文献
812.
Theodore K. Miller Lawrence J. Onesti 《Journal of the American Water Resources Association》1988,24(6):1207-1217
ABSTRACT: Stream channel development is a complicated process involving many factors. A major goal of research in fluvial geomorphology is to develop an understanding of the relations between channel form, water discharge, and sediment discharge characteristics. The concept of thresholds has been introduced as an element in fluvial processes, with the implication that the factors involved in a process might change in some way as threshold boundaries are passed. This study is focused on the extent to which a particular regional boundary represents a threshold in the process of stream channel development. Twenty-four alluvial stream channels from the Great Plains region and 24 from the Central Lowlands region are compared with regard to the distributional form, central tendency and dispersion characteristics, and correlation structure of ten variables, including indicators of discharge, channel sediment, and channel morphology. The results suggest that these aspects of the data are very similar between the regions, except for certain differences in central tendency characteristics, which are assumed to reflect underlying differences between the regions in geology and climate. In general, the results support the idea that this regional boundary is not an effective threshold with respect to the stream channel development process, and that, therefore, stream channels develop in these environmentally distinct regions by way of a similar process. 相似文献
813.
814.
Karen L. Bushaw‐Newton David D. Hart James E. Pizzuto James R. Thomson Jennifer Egan Jeffrey T. Ashley Thomas E. Johnson Richard J. Horwitz Melissa Keeley Joy Lawrence Don Charles Catherine Gatenby Daniel A. Kreeger Tim Nightengale Roger L. Thomas David J. Velinsky 《Journal of the American Water Resources Association》2002,38(6):1581-1599
ABSTRACT: Dam removal has been proposed as an effective method of river restoration, but few integrative studies have examined ecological responses to the removal of dams. In 1999, we initiated an interdisciplinary study to determine ecological responses to the removal of a 2 m high dam on lower Manatawny Creek in southeastern Pennsylvania. We used an integrative monitoring program to assess the physical, chemical, and biological responses to dam removal. Following removal in 2000, increased sediment transport has led to major changes in channel form in the former impoundment and downstream reaches. Water quality did not change markedly following removal, probably because of the impoundment's short hydraulic residence time (less than two hours at base flow) and infrequent temperature stratification. When the impoundment was converted to a free flowing reach, the composition of the benthic macroinvertebrate and fish assemblages in this portion of Manatawny Creek shifted dramatically from lentic to lotic taxa. Some fish species inhabiting the free flowing reach downstream from the dam were negatively affected by large scale sediment transport and habitat alteration following dam removal, but this appears to be a short term response. Based on our observations and experiences in this study, we provide a list of issues to evaluate when considering future dam removals. 相似文献
815.
This two‐level study of child welfare and juvenile justice case management teams addresses construct, measurement, and composition issues that plague multilevel research on organizational culture and climate. Very few empirical studies have examined both culture and climate simultaneously, and none have provided evidence that culture and climate are distinct or similar constructs. Confirmatory factor analysis (CFA), within‐group consistency analysis (rwg), between‐group differences (ICC and eta‐squared), and hierarchical linear models (HLM) analysis provide evidence that climate and culture are separate constructs that vary by organizational unit, and are related to work attitudes, perceptions, and behavior. Findings link team‐level culture and climate to individual‐level job satisfaction and commitment, perceptions of service quality, and turnover. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
816.
N. Gruchy F. Vialard E. Blondeel N. Le Meur G. Joly-Hélas P. Chambon M. Till M. Herbaut-Graux A. Vigouroux-Castera A. Coussement J. Lespinasse F. Amblard M. Jimenez L. Lebel Roy Camille F. Carré-Pigeon E. Flori F. Mugneret S. Jaillard C. Yardin R. Harbuz M. Collonge Rame P. Vago M. Valduga N. Leporrier 《黑龙江环境通报》2014,34(12):1133-1138
817.
818.
Wanjun Liu Amar K. Mohanty Per Askeland Lawrence T. Drzal Manjusri Misra 《Journal of Polymers and the Environment》2008,16(3):177-182
Chemical modification of soy protein with monomers such as maleic anhydride, glycidyl methacrylate and styrene was accomplished
using reactive extrusion technology. Thermal and mechanical properties of the modified soy protein plastics were characterized
with differential scanning calorimetry (DSC), a dynamic mechanical analyzer (DMA) and a United Testing System load frame.
It was found that the denaturation temperature and the glass transition temperature of soy protein plastic changed. In addition,
the tensile properties of modified soy protein plastic improved. Attenuated total reflection Fourier transform infrared (ATR-FTIR)
and X-ray photoelectron spectroscopy (XPS) were used to characterize the structure of modified soy proteins. A suggestion
of the interaction between soy protein and functional group in functional polymers is given. Through the in-situ interaction
between the polymer and soy protein plastic, the mechanical properties of the soy protein plastic can be adjusted and controlled. 相似文献
819.
Economic effects of CO2 fertilization of crops: transforming changes in yield into changes in supply 总被引:1,自引:0,他引:1
Increasing concentrations of atmospheric carbon dioxide CO2 have a beneficial effect on crop production that would tend to offset some of the economic losses that might be generated in some areas by the climatic effects of atmospheric CO2 and other greenhouse gases. Previous estimates of the economic benefits of CO2 fertilization on world crop production, however, were based on the assumption that percent changes in supply are equal to percent changes in yield. This assumption is not valid, however, because it confounds changes in supply with changes in quantity supplied. This error leads to an overestimation of the real economic benefits of CO2 fertilization by 61–166%. The effects of CO2 fertilization on crop production, therefore, will reduce some of the potential damages caused by the climatic impacts of greenhouse gases, but by significantly less than that indicated in earlier research. 相似文献
820.
Henry P. Huntington Lawrence C. Hamilton Craig Nicolson Ronald Brunner Amanda Lynch Astrid E. J. Ogilvie Alexey Voinov 《Regional Environmental Change》2007,7(4):173-186
Human dimensions research focuses on the interrelationships between humans and the environment. To date, human dimensions
research in arctic regions has concentrated primarily on local events and contexts. As such, it complements analysis elsewhere
of adaptation and sustainable development within broad institutional, social, and environmental contexts. This paper reviews
five projects from the Human Dimensions of the Arctic System (HARC) initiative, established by the US National Science Foundation
in 1997. Common themes and findings are highlighted: climatic variations or change affect societies through interactions with
human activities; population dynamics provide key quantitative indicators of social impacts and well being; and specific impacts
and responses are the result of complex, context-sensitive interactions. Congruent approaches to the challenges of interdisciplinary
research are also identified: multivariate time plots aid the integration of data, retrospective and prospective studies are
part of a continuum and reinforce one another, comparative studies are essential for understanding general principles of human
dimensions, and arctic residents can play a vital role in research and action. 相似文献