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561.
A regression method was developed for the hydrophobicity ruler approach, which is an indirect method for determining the octanol/water partition coefficients of very hydrophobic compounds. Two constants introduced into the mathematical model were obtained by regression of the absorption data sampled before the partition equilibrium. A water miscible organic solvent was used to increase the solubility of the very hydrophobic compounds in the aqueous solution so that the hydrophobicity scale was reduced and the equilibration was accelerated. Polydimethylsiloxane/methanol aqueous solution and a series of 21 polychlorinated biphenyls (PCBs) were used to demonstrate the regression method. The PCB compounds with known experimental logK(o/w) values served as reference compounds, while the PCB compounds without known logK(o/w) values were determined. The distribution coefficients (logK(p/s)), uptake and elimination rate constants were obtained from the two regression constants for each compound (reference or unknown). The correlation of the logK(p/s) values of the reference PCB compounds with their logK(o/w) values was linear (logK(o/w)=2.69logK(p/s)+0.76, R(2)=0.97). The logK(o/w) values were compared with literature values and suggested that some values from the literature far off the calibration line could be inaccurate. The critical experimental factors, the merits of the regression method were discussed. 相似文献
562.
The wedge sole Dicologlossa cuneata (Moreau, 1881) is a coastal species that lives along the inner shelf waters of the Gulf of Cadiz down to a depth of 115 m.
Its fishery, the size composition of the exploited population, and its reproduction have been studied on the basis of data
acquired from commercial statistics from 1984 to 1994 and from sampling carried out during 1993 and 1994. The relative abundance
of the species and its geographic and bathymetric distribution have been examined by analysis of four trawl surveys carried
out from 1992 to 1994. D. cuneata is captured mainly by the trawl fleet, and to a lesser extent by gillnet gears. Wedge sole fishery has a marked seasonality.
Size-frequency distributions from commercial samples and from bottom-trawl surveys are very similar, ranging from 12 to 26 cm
total body length (TL). D. cuneata is a “repeat-spawner”. Peak spawning is from January to May. Females attain sexual maturity at 18 cm TL, while sexually mature
males have been observed at 15 cm TL. The flexibility of the spawning strategy of D. cuneata throughout its distribution range is discussed. The scarcity of small specimens in the monthly samples and sequential spawning
throughout the year prevented the estimation of growth parameters by means of length-frequency analysis. D. cuneata is present in greatest abundances in the sandy–muddy bottoms of the Guadalquivir River mouth at 15 to 30 m depth. Its optimum
habitat coincides with the principal commercial fishing grounds. The possibility of reproductive vertical migration is discussed,
but more precise data are needed before a viable hypothesis can be made.
Received: 1 July 1997 / Accepted: 27 November 1997 相似文献
563.
M. Capobianco M. J. F. Stive J. A. Jiménez A. Sanchez-Arcilla 《Journal of Coastal Conservation》1998,4(1):7-16
Global climatic change is likely to take place and could eventually affect Mediterranean deltas and other lowlying coastal
regions. This would have serious implications for the natural resources of these deltaic areas, as well as for human settlements
and related economic activities.
To achieve sound decision making, to prevent damages and to avoid risky investments, it is necessary to understand the integral
functioning of deltaic areas and to determine their vulnerability and response to large-scale change phenomena. Optimal use
of the available knowledge will require that existing and new field measurements are combined and that integrated (physical/ecological)
conceptual models of deltaic behaviour are developed with socio-economics scenarios as boundary conditions.
This paper illustrates the methodological effort towards organizing a modeling framework to conduct budget computations at
various scales with reference to the most significant ‘physiogrpahic units’ and to the most significant deltaic processes.
The final objective is to handle the problem of evaluating possible changes under different scenarios. 相似文献
564.
Georgios Niarchos Lutz Ahrens Dan Berggren Kleja Gareth Leonard Jim Forde Jonny Bergman Erik Ribeli Matilda Schütz Fritjof Fagerlund 《补救:环境净化治理成本、技术与工艺杂志》2023,33(2):101-110
Soil and groundwater contamination by per- and polyfluoroalkyl substances (PFAS) has been a significant concern to human health and environmental quality. Remediation of contaminated sites is crucial to prevent plume expansion but can prove challenging due to the persistent nature of PFAS combined with their high aqueous mobility. In this case study, we investigated the potential of colloidal activated carbon (CAC) for soil stabilization at the pilot scale, aiming to entrap PFAS and prevent their leaching from soil into groundwater. Monitoring of the site revealed the presence of two potential sources of PFAS contamination at concentrations up to 23 μg L−1 for ∑11PFAS in groundwater. After CAC application, initial results indicated a 76% reduction of ∑11PFAS and high removal rates for long-chain PFAS, such as perfluorooctane sulfonic acid and perfluorooctanoic acid. A spike in concentrations was noticed 6 months after injection of CAC, showing a rebound of the plume and a reduction of treatment effectiveness. Based on long-term monitoring data, the treatment effectiveness for ∑11PFAS dropped to 52%. The rebound of concentrations was attributed to the plume bypass of the barrier due to the presence of high conductivity zones, which likely occurred because of seasonal changes in groundwater flow directions or the CAC application at the site. This demonstrates the need for a detailed and accurate hydrogeological understanding of contaminated sites before designing and applying stabilization techniques, especially at sites with high geologic and hydrologic complexity. The results herein can serve as a guideline for treating similar sites and help avoid potential pitfalls of remedial efforts. 相似文献