全文获取类型
收费全文 | 4707篇 |
免费 | 20篇 |
国内免费 | 58篇 |
专业分类
安全科学 | 81篇 |
废物处理 | 139篇 |
环保管理 | 474篇 |
综合类 | 1359篇 |
基础理论 | 1005篇 |
环境理论 | 3篇 |
污染及防治 | 1018篇 |
评价与监测 | 310篇 |
社会与环境 | 378篇 |
灾害及防治 | 18篇 |
出版年
2022年 | 40篇 |
2021年 | 68篇 |
2020年 | 32篇 |
2019年 | 42篇 |
2018年 | 73篇 |
2017年 | 66篇 |
2016年 | 94篇 |
2015年 | 64篇 |
2014年 | 126篇 |
2013年 | 351篇 |
2012年 | 134篇 |
2011年 | 195篇 |
2010年 | 142篇 |
2009年 | 178篇 |
2008年 | 172篇 |
2007年 | 196篇 |
2006年 | 152篇 |
2005年 | 125篇 |
2004年 | 119篇 |
2003年 | 141篇 |
2002年 | 130篇 |
2001年 | 146篇 |
2000年 | 102篇 |
1999年 | 81篇 |
1998年 | 39篇 |
1997年 | 46篇 |
1996年 | 33篇 |
1995年 | 61篇 |
1994年 | 38篇 |
1993年 | 37篇 |
1992年 | 45篇 |
1991年 | 41篇 |
1990年 | 55篇 |
1989年 | 47篇 |
1987年 | 32篇 |
1985年 | 36篇 |
1984年 | 28篇 |
1983年 | 41篇 |
1982年 | 30篇 |
1981年 | 43篇 |
1980年 | 35篇 |
1979年 | 35篇 |
1978年 | 29篇 |
1976年 | 33篇 |
1972年 | 30篇 |
1968年 | 27篇 |
1967年 | 29篇 |
1966年 | 33篇 |
1965年 | 30篇 |
1964年 | 31篇 |
排序方式: 共有4785条查询结果,搜索用时 296 毫秒
921.
Minimizing atmospheric emissions of soil fumigants is critical for protecting human and environmental health. Covering the soil surface with a plastic tarp is a common approach to restrict fumigant emissions. The mass transfer of the fumigant vapors through the tarp is often the rate-limiting factor in fumigant emissions. An approach for standardizing measurements of film permeability is proposed that is based on determining the resistance (R) of films to diffusion of fumigants. Using this approach, values were determined for more than 200 film-chemical combinations under a range of temperature, relative humidity, and film handling conditions. Resistance to diffusion was specific for each fumigant/film combination, with the largest range of values observed for the fumigant chloropicrin. For each fumigant, decreased with increasing temperature. Changes in film permeability due to increases in temperature or field installation were generally less than a factor of five. For one film, values determined under conditions of very high relative humidity (approximately 100%) were at least 100 times lower than when humidity was very low (approximately 2%). This approach simplifies the selection of appropriate films for soil fumigation by providing rapid, reproducible, and precise measurements of their permeability to specific fumigants and application conditions. 相似文献
922.
Surface application of manures leaves nitrogen (N) and phosphorus (P) susceptible to being lost in runoff, and N can also be lost to the atmosphere through ammonia (IH3) volatilization. Tillage immediately after surface application of manure moves manure nutrients under the soil surface, where they are less vulnerable to runoff and volatilization loss. Tillage, however, destroys soil structure, can lead to soil erosion, and is incompatible with forage and no-till systems. A variety of technologies are now available to place manure nutrients under the soil surface, but these are not widely used as surface broadcasting is cheap and long established as the standard method for land application of manure. This collection of papers includes agronomic, environmental, and economic assessments of subsurface manure application technologies, many of which clearly show benefits when comparedwith surface broadcasting. However, there remain significant gaps in our current knowledge, some related to the site-specific nature of technological performance, others related to the nascent and incomplete nature of the assessment process. Thus, while we know that we can improve land application of manure and the sustainability of farming systems with alternatives to surface broadcasting, many questions remain concerning which technologies work best for particular soils, manure types, and farming and cropping systems. 相似文献
923.
Ben Vanpeperstraete Sébastien Duyck Medani P. Bhandari Janis Brizga Leida Rijnhout Sylvia Lorek A. Peter Castro Chiung Ting Chang Herman Daly Robert J. Didham Gianluca Ferraro Oliver Greenfield Ashok Khosla Ernst Ulrich von Weizsäcker Birgit Lode Simon Miles Henrique Pacini Semida Silveira Leisa Perch Jaap Rijnsburger Mukul Sanwal Sameera Savarala S. Jacob Scherr Kallidaikurichi E. Seetharam A.M.M. Adeeb Donna Shepherd Adrian Smith Lisinka Ulatowska Alice Vincent Werner John 《Natural resources forum》2011,35(4):334-342
924.
Moreno-Jiménez E Vázquez S Carpena-Ruiz RO Esteban E Peñalosa JM 《Journal of environmental management》2011,92(6):1584-1590
Re-vegetation is the main aim of ecological restoration projects, and in Mediterranean environments native plants are desirable to achieve successful restoration. In 1998, the burst of a tailings dam flooded the Guadiamar river valley downstream from Aznalcóllar (Southern Spain) with sludges that contained elevated concentrations of metals and metalloids, polluting soils and waters. A phytoremediation experiment to assess the potential use of native shrub species for the restoration of soils affected by the spillage was performed from 2005 to 2007, with soils divided into two groups: pH < 5 and pH > 5. Four native shrubs (Myrtus communis, Retama sphaerocarpa, Rosmarinus officinalis and Tamarix gallica) were planted and left to grow without intervention. Trace element concentrations in soils and plants, their extractability in soils, transfer factors and plant survival were used to identify the most-interesting species for phytoremediation. Total As was higher in soils with pH < 5. Ammonium sulphate-extractable zinc, copper, cadmium and aluminium concentrations were higher in very-acid soils, but arsenic was extracted more efficiently when soil pH was >5. Unlike As, which was either fixed by Fe oxides or retained as sulphide, the extractable metals showed significant relationships with the corresponding total soil metal concentration and inverse relationships with soil pH. T. gallica, R. officinalis and R. sphaerocarpa survived better in soils with pH > 5, while M. communis had better survival at pH < 5. R. sphaerocarpa showed the highest survival (30%) in all soils. Trace element transfer from soil to harvestable parts was low for all species and elements, and some species may have been able to decrease trace element availability in the soil. Our results suggest that R. sphaerocarpa is an adequate plant species for phytostabilising these soils, although more research is needed to address the self-sustainability of this remediation technique and the associated environmental changes. 相似文献
925.
Rita JC Gama-Rodrigues EF Gama-Rodrigues AC Polidoro JC Machado RC Baligar VC 《Environmental management》2011,48(1):134-141
Agroforestry systems (AFSs) have an important role in capturing above and below ground soil carbon and play a dominant role
in mitigation of atmospheric CO2. Attempts has been made here to identify soil organic matter fractions in the cacao-AFSs that have different susceptibility
to microbial decomposition and further represent the basis of understanding soil C dynamics. The objective of this study was
to characterize the organic matter density fractions and soil size fractions in soils of two types of cacao agroforestry systems
and to compare with an adjacent natural forest in Bahia, Brazil. The land-use systems studied were: (1) a 30-year-old stand
of natural forest with cacao (cacao cabruca), (2) a 30-year-old stand of cacao with Erythrina glauca as shade trees (cacao + erythrina), and (3) an adjacent natural forest without cacao. Soil samples were collected from 0-10 cm
depth layer in reddish-yellow Oxisols. Soil samples was separated by wet sieving into five fraction-size classes (>2000 μm,
1000–2000 μm, 250–1000 μm, 53–250 μm, and <53 μm). C and N accumulated in to the light (free- and intra-aggregate density
fractions) and heavy fractions of whole soil and soil size fraction were determined. Soil size fraction obtained in cacao
AFS soils consisted mainly (65 %) of mega-aggregates (>2000 μm) mixed with macroaggregates (32–34%), and microaggregates (1–1.3%).
Soil organic carbon (SOC) and total N content increased with increasing soil size fraction in all land-use systems. Organic
C-to-total N ratio was higher in the macroaggregate than in the microaggregate. In general, in natural forest and cacao cabruca
the contribution of C and N in the light and heavy fractions was similar. However, in cacao + erythrina the heavy fraction
was the most common and contributed 67% of C and 63% of N. Finding of this study shows that the majority of C and N in all
three systems studied are found in macroaggregates, particularly in the 250–1000 μm size aggregate class. The heavy fraction
was the most common organic matter fraction in these soils. Thus, in mature cacao AFS on highly weathered soils the main mechanisms
of C stabilization could be the physical protection within macroaggregate structures thereby minimizing the impact of conversion
of forest to cacao AFS. 相似文献
926.
CO2 capture and storage from a bioethanol plant: Carbon and energy footprint and economic assessment
A. Laude O. Ricci G. Bureau J. Royer-Adnot A. Fabbri 《International Journal of Greenhouse Gas Control》2011,5(5):1220-1231
Biomass energy and carbon capture and storage (BECCS) can lead to a net removal of atmospheric CO2. This paper investigates environmental and economic performances of CCS retrofit applied to two mid-sized refineries producing ethanol from sugar beets. Located in the Region Centre France, each refinery has two major CO2 sources: fermentation and cogeneration units. “carbon and energy footprint” (CEF) and “discounted cash flow” (DCF) analyses show that such a project could be a good opportunity for CCS early deployment. CCS retrofit on fermentation only with natural gas fired cogeneration improves CEF of ethanol production and consumption by 60% without increasing much the non renewable energy consumption. CCS retrofit on fermentation and natural gas fired cogeneration is even more appealing by decreasing of 115% CO2 emissions, while increasing non renewable energy consumption by 40%. DCF shows that significant project rates of return can be achieved for such small sources if both a stringent carbon policy and direct subsidies corresponding to 25% of necessary investment are assumed. We also underlined that transport and storage cost dilution can be realistically achieved by clustering emissions from various plants located in the same area. On a single plant basis, increasing ethanol production can also produce strong economies of scale. 相似文献
927.
928.
Dunxi Yu William J. Morris Raphael Erickson Jost O.L. Wendt Andrew Fry Constance L. Senior 《International Journal of Greenhouse Gas Control》2011
Ash deposition is still an unresolved problem when retrofitting existing air-fired coal power plants to oxy-fuel combustion. Experimental data are quite necessary for mechanism validation and model development. This work was designed to obtain laboratory combustor data on ash and deposits from oxy-coal combustion, and to explore the effects of oxy-firing on their formation. Two bituminous coals (Utah coal and Illinois coal) and one sub-bituminous coal (PRB coal) were burned on a down-fired combustor under both oxy- and air-firing. Two oxy-fired cases, i.e., 27 vol% O2/73 vol% CO2 and 32 vol% O2/68 vol% CO2, were selected to match the radiation flux and the adiabatic flame temperature of air combustion, respectively. Once-through CO2 was used to simulate fully cleaned recycled flue gas. The flue gas excess oxygen was fixed at 3 vol%. For each case, both size-segregated fly ash and bulk fly ash samples were obtained. Simultaneously, ash deposits were collected on an especially designed un-cooled deposition probe. Ash particle size distributions and chemical composition of all samples were characterized. Data showed that oxy-firing had insignificant impacts on the tri-modal ash particle size distributions and composition size distributions in the size range studied. Bulk ash compositions also showed no significant differences between oxy- and air-firing, except for slightly higher sulfur contents in some oxy-fired ashes. The oxy-fired deposits were thicker than those from air-firing, suggesting enhanced ash deposition rates in oxy-firing. Oxy-firing also had apparent impacts on the deposit composition, especially for those components (e.g., CaO, Fe2O3, SO3, etc.) that could contribute significantly to ash deposition. Based on these results, aerodynamic changes in gas flow and changes in combustion temperature seemed more important than chemical changes of ash particles in determining deposit behavior during oxy-coal combustion. 相似文献
929.
A. Bischi Ø. Langørgen I. Saanum J. Bakken M. Seljeskog M. Bysveen J.-X. Morin O. Bolland 《International Journal of Greenhouse Gas Control》2011,5(3):467-474
Nowadays the lab scale feasibility of the chemical looping combustion technology has been proved. This article deals with many of the design requirements that need to be fulfilled to make this technology applicable at industrial scale. A design for a 150 kWth chemical looping combustion reactor system is proposed. In the base case it is supposed to work with gaseous fuels and inexpensive oxygen carriers derived from industrial by-products or natural minerals. More specifically the fuel will be methane and a manganese ore will be the basis for the oxygen carrier. It is a double loop circulating fluidized bed where both the air reactor and the fuel reactor are capable to work in the fast fluidization regime in order to increase the gas solids contact along the reactor body. High operational flexibility is aimed, in this way it will be possible to run with different fuels and oxygen carriers as well as different operating conditions such as variation in air excess. Compactness is a major goal in order to reduce the required solid material and possibly to enclose the reactor body into a pressurized vessel to investigate the chemical looping combustion under pressurized conditions. The mass and heat balance are described, as well as the hydrodynamic investigations performed. Most design solutions presented are taken from industrial standards as one main objective is to meet commercial requirements. 相似文献
930.
Integrated remote sensing and GIS techniques for landslide hazard zonation: a case study Wadi Watier area,South Sinai,Egypt 总被引:3,自引:0,他引:3
Mohamed O. Arnous 《Journal of Coastal Conservation》2011,15(4):477-497
Natural hazard analysis involves mapping and identifying future hazardous zones through the analysis of the controls influencing
hazard initiation and occurrence. One of such natural hazard is the landslide. Landslides are amongst the most costly and
damaging natural hazards especially in mountain regions and are triggered mainly by seismic activity and/or rainfall. The
aim of the present study is to integrate Remote Sensing (RS) and Geographic Information System (GIS) tools to create thematic
layers for assessment and the estimation of landslide hazard zones in and surrounding the Wadi Watier area, South Sinai, Egypt.
Various factors, variables and/or parameters can be derived from thematic layers such as lithology, structural lineaments,
land-cover/land-use, terrain analysis and earthquakes. Intensity risk layers were created by using ERDAS Imagine 9.2, ARC
GIS 9.2 and ARC INFO 7.2.1 software. Enhanced Thematic Mapper (ETM+7) Landsat satellite images were used to discriminate and
extract structural lineaments, lithology and land-use/land-cover variables for the study area. The Digital Elevation Model
(DEM) was generated from digitized topographic maps to produce terrain analysis maps such as; slope, aspect, height elevation,
and 3D. The weighting score rating system based on the relative importance of various causal factors derived from RS data
and other thematic layers was used for landslide hazard zonation (LHZ). Based on these data, a simple algorithm was created
to classify the area into different risk zones. By overlaying all hazard layers a final landslide hazard map was produced.
Using trial and error and statistical methods the weight score rating values have been readjusted. GIS integration with RS
data can greatly facilitate classifying landslide hazard zones into low risk, moderate risk and high risk by using a slicing
operation. Seismic data are integrated with final the LHZ to generate a LHZ scenario map for the future and to draw up an
action plan of mitigation measures to avoid the damage, loss of life and socio-economic impacts in the study area. 相似文献