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71.
Paul van Nugteren Leon Moodley Geert-Jan Brummer Carlo H. R. Heip Peter M. J. Herman Jack J. Middelburg 《Marine Biology》2009,156(11):2277-2287
Organic matter (OM) remineralization may be considered a key function of the benthic compartment of marine ecosystems and
in this study we investigated if the input of labile organic carbon alters mineralization of indigenous sediment OM (OM priming).
Using 13C-enriched diatoms as labile tracer carbon, we examined shallow-water sediments (surface and subsurface layers) containing
organic carbon of different reactivity under oxic versus anoxic conditions. The background OM decomposition rates of the sediment
used ranged from 0.08 to 0.44 μmol C mlws−1 day−1. Algal OM additions induced enhanced levels of background remineralization (priming) up to 31% and these measured excess
fluxes were similar to mineralization of the added highly degradable tracer algal carbon. This suggests that OM priming may
be important in marine sediments. 相似文献
72.
Arrival time and magnitude of airborne fission products from the Fukushima, Japan, reactor incident as measured in Seattle, WA, USA 总被引:2,自引:0,他引:2
Leon JD Jaffe DA Kaspar J Knecht A Miller ML Robertson RG Schubert AG 《Journal of environmental radioactivity》2011,102(11):1032-1038
We report results of air monitoring started due to the recent natural catastrophe on 11 March 2011 in Japan and the severe ensuing damage to the Fukushima Dai-ichi nuclear reactor complex. On 17-18 March 2011, we registered the first arrival of the airborne fission products 131I, 132I, 132Te, 134Cs, and 137Cs in Seattle, WA, USA, by identifying their characteristic gamma rays using a germanium detector. We measured the evolution of the activities over a period of 23 days at the end of which the activities had mostly fallen below our detection limit. The highest detected activity from radionuclides attached to particulate matter amounted to 4.4 ± 1.3 mBq m−3 of 131I on 19-20 March. 相似文献
73.
Interacting effects of sulphate pollution, sulphide toxicity and eutrophication on vegetation development in fens: A mesocosm experiment 总被引:1,自引:0,他引:1
Jeroen J.M. Geurts Judith M. Sarneel Jan G.M. Roelofs Leon P.M. Lamers 《Environmental pollution (Barking, Essex : 1987)》2009,157(7):2072-2081
Both eutrophication and SO4 pollution can lead to higher availability of nutrients and potentially toxic compounds in wetlands. To unravel the interaction between the level of eutrophication and toxicity at species and community level, effects of SO4 were tested in nutrient-poor and nutrient-rich fen mesocosms. Biomass production of aquatic and semi-aquatic macrophytes and colonization of the water layer increased after fertilization, leading to dominance of highly competitive species. SO4 addition increased alkalinity and sulphide concentrations, leading to decomposition and additional eutrophication. SO4 pollution and concomitant sulphide production considerably reduced biomass production and colonization, but macrophytes were less vulnerable in fertilized conditions. The experiment shows that competition between species, vegetation succession and terrestrialization are not only influenced by nutrient availability, but also by toxicity, which strongly interacts with the level of eutrophication. This implies that previously neutralized toxicity effects in eutrophied fens may appear after nutrient reduction measures have been taken. 相似文献
74.
This study characterized some of the physical and chemical features of large outside field grease abatement devices (GADs). 24-hour measurements of several food service establishments' (FSEs') influent GAD flowrates indicated highly intermittent conditions with hydraulic retention times (HRTs) that exceeded the common recommendation (30 minutes) by two to five times. Investigation into the chemical characteristics of GADs indicated highly variable influent and effluent fat, oil, and grease (FOG) concentrations. Low pH and dissolved oxygen values were measured throughout the GAD, indicating the likely occurrence of anaerobic microbial processes. Detailed spatial and temporal observations of the accumulation of FOG and food solids were also discussed. Though the FOG layer remained relatively constant for all GAD configurations investigated, results indicated that commonly-used GAD configurations with a straight submerged inlet tee or no-inlet tee configuration may result in the transport of food solids into the second compartment. The present research showed increased accumulation of food solids in the first compartment with a retro-fit flow distributive inlet. This retro-fit displays promise for potentially improving the separation characteristics of existing GADs. 相似文献
75.
Leon S. Dochinger Alden M. Townsend Donald W. Seegrist Frederick W. Bender 《Journal of the Air & Waste Management Association (1995)》2013,63(5):369-371
This paper verifies the presence of significant interclonal variation in the tolerance of hybrid poplar (Populus deltoides Bartr. cv. Angulata × P. trichocarpa Torr. and Gray) to sulfur dioxide fumigation. Rooted stem cuttings of four hybrid poplar clones were exposed to 5 ppm sulfur dioxide for 0, 3, 6, 9, or 12 hours in controlled environment chambers. Multivariate analyses were made from the shoot growth measurements recorded for 4 weeks before and after fumigation and on the data of foliar injury induced by sulfur dioxide. The following factors were statistically significant in determining growth response and foliar injury: (1) genotype; (2) duration of treatment; and (3) interaction between genotype and hours of fumigation. All partial correlations between foliar injury and subsequent shoot growth were positive and significant. Sufficient genetic variation appears to exist in this Populus hybrid to encourage selection of clones tolerant to short-term exposures of high levels of sulfur dioxide. 相似文献
76.
Leon S. Dochinger Thomas A. Seliga 《Journal of the Air & Waste Management Association (1995)》2013,63(11):1103-1105
The First International Symposium on Acid Precipitation and the Forest Ecosystem sponsored by the United States Department of Agriculture, Forest Service, Northeastern Forest Experiment Station, and by the Atmospheric Sciences Program of The Ohio State University was held in Columbus, Ohio, May 12-15, 1975. Approximately 300 people from 12 countries attended the Symposium. 相似文献
77.
Food is the major source for polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) accumulation in human body. In infant period, breast milk and formula milk are the major food sources. Congener-specific analyses of 17 PCDD/PCDFs were performed on 10 brands of formula milk samples which were milk-based and 37 breast milk samples collected from women living in southern Taiwan. The levels of 17 PCDD/PCDFs in 10 formula milk samples ranged from 0.468 to 0.962 pg WHO-TEQ/g lipid, with a mean value of 0.713+/-0.163 pg WHO-TEQ/g lipid. For the 37 breast milk samples, their PCDD/PCDF levels were 14.7+/-9.36 pg WHO-TEQ/g lipid, with a range between 4.21 and 52.8 pg WHO-TEQ/g lipid. At 12th month of age for infants, average daily intakes (ADI) of PCDD/PCDFs were 2.1 pg WHO-TEQ/kg/day for the formula-feeding infants, and 13 pg WHO-TEQ/kg/day for the breast-feeding infants. The present data may provide useful information for risk-benefit evaluation of formula- and breast-feeding. 相似文献
78.
Limited occurrence of denitrification in four shallow aquifers in agricultural areas of the United States 总被引:1,自引:0,他引:1
Green CT Puckett LJ Böhlke JK Bekins BA Phillips SP Kauffman LJ Denver JM Johnson HM 《Journal of environmental quality》2008,37(3):994-1009
The ability of natural attenuation to mitigate agricultural nitrate contamination in recharging aquifers was investigated in four important agricultural settings in the United States. The study used laboratory analyses, field measurements, and flow and transport modeling for monitoring well transects (0.5 to 2.5 km in length) in the San Joaquin watershed, California, the Elkhorn watershed, Nebraska, the Yakima watershed, Washington, and the Chester watershed, Maryland. Ground water analyses included major ion chemistry, dissolved gases, nitrogen and oxygen stable isotopes, and estimates of recharge date. Sediment analyses included potential electron donors and stable nitrogen and carbon isotopes. Within each site and among aquifer-based medians, dissolved oxygen decreases with ground water age, and excess N(2) from denitrification increases with age. Stable isotopes and excess N(2) imply minimal denitrifying activity at the Maryland and Washington sites, partial denitrification at the California site, and total denitrification across portions of the Nebraska site. At all sites, recharging electron donor concentrations are not sufficient to account for the losses of dissolved oxygen and nitrate, implying that relict, solid phase electron donors drive redox reactions. Zero-order rates of denitrification range from 0 to 0.14 micromol N L(-1)d(-1), comparable to observations of other studies using the same methods. Many values reported in the literature are, however, orders of magnitude higher, which is attributed to a combination of method limitations and bias for selection of sites with rapid denitrification. In the shallow aquifers below these agricultural fields, denitrification is limited in extent and will require residence times of decades or longer to mitigate modern nitrate contamination. 相似文献
79.
E. Salinas J. Atalaya Y. Hamnerius C. J. Solano D. Gonzales C. Contreras C. Leon M. A. Sumari S. Dimitriou M. Rezinkina 《The Environmentalist》2007,27(4):571-576
When large structures such as residential compounds or public buildings are under the influence of extremely low frequency
(ELF) magnetic fields, such as the one generated by a system of railways fed by 16.67 Hz, standard methods of designing shielding
structures by numerical methods usually fail. The latter can be explained by the difficulty posed in the computing process
by the large aspect ratios involved due to thin layers of metal (a few millimetres or centimetres) in contrast to the large
dimensions of the affected structure (several tens of meters). In some cases one has to utilize special approximations such
as surface conductivity, which are not easy to handle when the designed shielding structure is clearly three -dimensional.
Other alternatives such as experimentation in situ are very costly. Here, a new technique is presented of mitigating the field
by using three-dimensional propagation of induced currents optimizing the field reduction factors and minimizing the cost
of shielding material. The particular designing method is a hybrid of numerical simulations combined with lab experimentation
using scaled models of the large structure. The method is rather cost-effective and flexible as various designs can be easily
tested. Results are presented in the form of magnetic field values, at various locations in the buildings, before and after this mitigation technique is applied. 相似文献
80.
Wildlife Conservation in Taiwan 总被引:3,自引:0,他引:3