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231.
Keith T. Maddy 《Agriculture, ecosystems & environment》1983,9(2):159-172
In recent years, pesticide usage in the United States has increased markedly. As measured in 1980 for the U.S.A., there were: (1) more than 45 000 individually products registered; (2) more than 1500 active ingredients involved; and (3) about 2.5 billion pounds of active ingredients used annually. Pesticide usage in agriculture has probably peaked and will probably level off and may even decrease in the 1980's because of public health concerns, environmental concerns, lower dose levels of newer pesticides, and the introduction and use of integrated pest management programs and bio-control programs. 相似文献
232.
Most species of social insects have singly mated queens, although there are notable exceptions. Competing hypotheses have been proposed to explain the evolution of high levels of multiple mating, but this issue is far from resolved. Here we use microsatellites to investigate mating frequency in the army ant Eciton burchellii and show that queens mate with an exceptionally large number of males, eclipsing all but one other social insect species for which data are available. In addition we present evidence that suggests that mating is serial, continuing throughout the lifetime of the queen. This is the first demonstration of serial mating among social hymenoptera. We propose that high paternity within colonies is most likely to have evolved to increase genetic diversity and to counter high pathogen and parasite loads. 相似文献
233.
Disruptive selection for responsiveness to queen mandibular gland pheromone (QMP) in the retinue bioassay resulted in the
production of high and low QMP responding strains of honeybees (Apis mellifera L.). Strains differed significantly in their retinue response to QMP after one generation of selection. By the third generation
the high strain was on average at least nine times more responsive than the low strain. The strains showed seasonal phenotypic
plasticity such that both strains were more responsive to the pheromone in the spring than in the fall. Directional selection
for low seasonal variation indicated that phenotypic plasticity was an additional genetic component to retinue response to
QMP. Selection for high and low retinue responsiveness to QMP was not an artifact of the synthetic blend because both strains
were equally responsive or non-responsive to whole mandibular gland extracts compared with QMP. The use of these strains clearly
pointed to an extra-mandibular source of retinue pheromones (Pankiw et al. 1995; Slessor et al. 1998; Keeling et al. 1999).
Received: 2 March 2000 / Accepted in revised form: 4 September 2000 相似文献
234.
Buckman AH Norstrom RJ Hobson KA Karnovsky NJ Duffe J Fisk AT 《Environmental pollution (Barking, Essex : 1987)》2004,128(3):327-338
Organochlorine contaminants (OCs) were determined in liver and fat of seven species of seabirds (Alle alle, Uria lomvia, Cepphus grylle, Rissa tridactyla, Pagophila eburnea, Larus hyperboreus, and Fulmaris glacialis) collected in May/June 1998 from the Northwater Polynya in northern Baffin Bay. OC concentrations ranged over an order of magnitude between seabird species and OC groups, with PCBs having the highest concentrations followed by DDT, chlordane, HCH and ClBz. Positive relationships between delta15N (estimator of trophic level) and OC concentrations (lipid basis) were found for all OC groups, showing that trophic position and biomagnification significantly influence OC concentrations in Arctic seabirds. Concentrations of a number of OCs in particular species (e.g., HCH in P. eburnean) were lower than expected based on delta15N and was attributed to biotransformation. P. eburnea and F. glacialis, which scavenge, and R. tridactyla, which migrate from the south, were consistently above the delta15N-OC regression providing evidence that these variables can elevate OC concentrations. Stable isotope measurements in muscle may not be suitable for identifying past scavenging events by seabirds. OC relative proportions were related to trophic position and phylogeny, showing that OC biotransformation varies between seabird groups. Trophic level, migration, scavenging and biotransformation all play important roles in the OCs found in Arctic seabirds. 相似文献
235.
T L Johnson D W Keith 《Journal of the Air & Waste Management Association (1995)》2001,51(10):1452-1459
The decoupling of fossil-fueled electricity production from atmospheric CO2 emissions via CO2 capture and sequestration (CCS) is increasingly regarded as an important means of mitigating climate change at a reasonable cost. Engineering analyses of CO2 mitigation typically compare the cost of electricity for a base generation technology to that for a similar plant with CO2 capture and then compute the carbon emissions mitigated per unit of cost. It can be hard to interpret mitigation cost estimates from this plant-level approach when a consistent base technology cannot be identified. In addition, neither engineering analyses nor general equilibrium models can capture the economics of plant dispatch. A realistic assessment of the costs of carbon sequestration as an emissions abatement strategy in the electric sector therefore requires a systems-level analysis. We discuss various frameworks for computing mitigation costs and introduce a simplified model of electric sector planning. Results from a "bottom-up" engineering-economic analysis for a representative U.S. North American Electric Reliability Council (NERC) region illustrate how the penetration of CCS technologies and the dispatch of generating units vary with the price of carbon emissions and thereby determine the relationship between mitigation cost and emissions reduction. 相似文献
236.
In this study, we examined the influence of the long-range transport of dust particles and air pollutants on the photochemistry of OH and NO3 on Jeju Island, Korea (33.17 degrees N, 126.10 degrees E) during the Asian-dust-storm (ADS) period of April 2001. Three ADS events were observed during the periods of April 10-12, 13-14, and 25-26. Average concentration levels of daytime OH and nighttime NO3 on Jeju Island during the ADS period were estimated to be about 1x10(6) and 2x10(8) moleculescm(-3) ( approximately 9 pptv), respectively. OH levels during the ADS period were lower than those during the non-Asian-dust-storm (NADS) period by a factor of 1.5. This was likely to result from higher CO levels and the significant loading of dust particles, reducing the photolysis frequencies of ozone. Decreases in NO3 levels during the ADS period was likely to be determined mainly by the enhancement of the N2O5 heterogeneous reaction on dust aerosol surfaces. Averaged over 24 h, the reaction between HO2 and NO was the most important source of OH during the study period, followed by ozone photolysis, which contributed more than 95% of the total source. The reactions with CO, NO2, and non-methane hydrocarbons (NMHCs) during the study period were major sinks for OH. The reaction of N2O5 on aerosol surfaces was a more important sink for nighttime NO3 during the ADS due to the significant loading of dust particles. The reaction of NO3 with NMHCs and the gas-phase reaction of N2O5 with water vapor were both significant loss mechanisms during the study period, especially during the NADS. However, dry deposition of these oxidized nitrogen species and a heterogeneous reaction of NO3 were of no importance. 相似文献
237.
Qureshi S Richards BK Steenhuis TS McBride MB Baveye P Dousset S 《Environmental pollution (Barking, Essex : 1987)》2004,132(1):61-71
Leaching of sludge-borne trace elements has been observed in experimental and field studies. The role of microbial processes in the mobilization of trace elements from wastewater sludge is poorly defined. Our objectives were to determine trace element mobilization from sludge subjected to treatments representing microbial acidification, direct chemical acidification and no acidification, and to determine the readsorption potential of mobilized elements using calcareous sand. Triplicate columns (10-cm diameter) for incubation and leaching of sludge had a top layer of digested dewatered sludge (either untreated, acidified with H2SO4, or limed with CaCO3; all mixed with glass beads to prevent ponding) and a lower glass bead support bed. Glass beads in the sludge layer, support layer or both were replaced by calcareous sand in four treatments used for testing the readsorption potential of mobilized elements. Eight sequential 8-day incubation and leaching cycles were operated, each consisting of 7.6 d of incubation at 28 degrees C followed by 8 h of leaching with synthetic acid rain applied at 0.25 cm/h. Leachates were analyzed for trace elements, nitrate and pH, and sludge layer microbial respiration was measured. The largest trace element, nitrate and S losses occurred in treatments with the greatest pH depression and greatest microbial respiration rates. Cumulative leaching losses from both microbial acidification and direct acidification treatments were > 90% of Zn and 64-80% of Cu and Ni. Preventing acidification with sludge layer lime or sand restricted leaching for all trace elements except Mo. Results suggested that the primary microbial role in the rapid leaching of trace elements was acidification, with results from direct acidification being nearly identical to microbial acidification. Microbial activity in the presence of materials that prevented acidification mobilized far lower concentrations of trace elements, with the exception of Mo. Trace elements mobilized by acidification were readsorbed by calcareous sand when present. 相似文献
238.
Seasonal treatment performance of small-surface flow wetlands was evaluated during their second operational year and compared with community-level physiological profiles (CLPP) of the heterotrophic bacterial community obtained from sole-carbon source utilization patterns in BIOLOG GN (Haywood, California) microplates. The CLPP patterns varied significantly by season, indicating reduced functional diversity in the heterotrophic community during warmer months of active plant growth (April through October). Principal component analysis (PCA) suggested that the functional community differed in planted versus unplanted wetlands during the growing season. Wetlands generally improved wastewater quality; however, treatment performance was reduced in the second year. Despite differences in the heterotrophic community suggested by CLPP, treatment efficiency with respect to removal of five-day biochemical oxygen demand or reduction in fecal indicator organisms generally was not significantly changed as a function of growing season or plant treatment. 相似文献
239.
The distribution and diet of juvenile (<750 mm) Patagonian toothfish are described from four annual trawl surveys (2003–2006)
around the island of South Georgia in the Atlantic sector of the Southern Ocean. Recruitment of toothfish varies inter-annually,
and a single large cohort dominated during the four years surveyed. Most juveniles were caught on the Shag Rocks shelf to
the NW of South Georgia, with fish subsequently dispersing to deeper water around both the South Georgia and Shag Rocks shelves.
Mean size of juvenile toothfish increased with depth of capture. Stomach contents analysis was conducted on 795 fish that
contained food remains and revealed that juvenile toothfish are essentially piscivorous, with the diet dominated by notothenid
fish. The yellow-finned notothen, Patagonotothen guntheri, was the dominant prey at Shag Rocks whilst at South Georgia, where P. guntheri is absent, the dominant prey were Antarctic krill and notothenid fish. The diet changed with size, with an increase in myctophid
fish and krill as toothfish grow and disperse. The size of prey also increased with fish size, with a greater range of prey
sizes consumed by larger fish. 相似文献
240.
The sorption of cadmium, copper and zinc from aqueous solutions onto bone char has been studied in both single and binary multi-component systems. Equilibrium experimental studies have been performed to determine the sorption capacity of bone char for each metal ion. The isotherm results have been analysed using single and multi-component equilibrium models. The rate of sorption of the metal ions onto bone char has been studied using an agitated batch adsorber. The concentration versus time decay curves have been measured and a number of mass transfer models have been developed and tested based on diffusion controlled sorption. The results of the equilibrium and rate studies are presented and discussed in the paper. The possible mechanisms of metal sorption are also discussed. Finally a series of fixed bed column studies have been performed and analysed using a diffusion mass transport model. The experimental results show a displacement effect for the binary metal ion breakthrough curves. 相似文献