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111.
112.
William J. Mitchell M. Rodney Midgett 《Journal of the Air & Waste Management Association (1995)》2013,63(5):491-495
Results from four field based collaborative tests and from one laboratory based collaborative test of the Orsat analytical procedure are discussed. The results from the five collaborative tests demonstrate that routinely using Orsat data to convert particulate emissions from combustion sources to the reference conditions of 50 % excess air and 12% carbon dioxide may introduce sizeable errors in the corrected particulate loading. Ways to improve the Orsat apparatus and increase the reliability of the data are suggested. Also reported are the results from field and laboratory studies on the reliability of using individual carbon dioxide and oxygen analyzers of the Fyrite* type to determine stack gas molecular weight. The laboratory study, which was done using three cylinders containing mixtures of carbon dioxide, oxygen, carbon monoxide, and nitrogen of known concentration, determined that these analyzers give carbon dioxide and oxygen analyses of sufficient reliability to yield accurate molecular weights. The results of the field studies, which were done on actual flue gas samples, also support this conclusion. 相似文献
113.
Although many studies focus on mercury (Hg) and methylmercury (MeHg) dynamics in streams, challenges remain in identifying the relative importance of land cover and seasonality at regulating Hg and MeHg dynamics at the watershed scale. Developing robust proxies for Hg and/or MeHg determination also remains a challenge. Our study used Hg, MeHg, and dissolved organic carbon (DOC) concentration measurements and various DOC fluorescence indices to characterize Hg and DOC dynamics in a forested watershed of the US Northeast. Principal component analysis indicated that land cover/landscape position (i.e., headwater vs. wetland-influenced area vs. lake-influenced area) explained 44 % of the variance in Hg, MeHg, DOC concentrations, and DOC quality during the snow-free season, while seasonality (i.e., air temperature and discharge) explained only 21 % of the variance in the results. Furthermore, finding a good proxy for Hg that is valid across a range of landscape positions remains a challenge; however, regression analysis indicated that the fluorescence peak Humic C (excitation?=?350 nm; emission?=?max (420–480)), which corresponds to the presence of melanoidins in water, explained 21 % of the variability in MeHg concentrations across both space and time (p?=?0.001), and thus appears to be a possible proxy for MeHg determination in our study watershed. From a management perspective, land cover modifications (lake, reservoir, and wetland) are likely to play more important roles at regulating Hg, MeHg, and DOC exports at the watershed scale than long-term changes in the climate of this region. 相似文献
114.
M. M. Lyons P. Aas J. D. Pakulski L. Van Waasbergen R. V. Miller D. L. Mitchell W. H. Jeffrey 《Marine Biology》1998,130(3):537-543
Ultraviolet radiation (UVR) has been implicated in coral-bleaching processes and UVR may create stress to marine organisms
by damage to DNA. Absorption of energy from UVB (280 to 320 nm) induces direct damage to DNA via cyclobutane pyrimidine dimer
photoproduct-formation. We examined the extent of DNA damage created by UVR in coral reef microbial communities and whether
the coral-surface microlayer (CSM) provides protection from UVR to the microorganisms found there. Diel patterns and depth
profiles of UVR effects were examined in coral mucus (coral-surface microlayer, CSM) from Montastraea faveolata and Colpophyllia natans, and water-column samples of similar depths. UV-induced photodamage was determined using a radioimmunoassay specific for
cyclobutane pyrimidine dimers (thymine dimers). Significant photodamage was detected in water-column and CSM samples, although
the level of damage in CSM samples was consistently lower than in water-column samples collected from the same depth, suggesting
the presence of photoprotective mechanisms within the CSM. Diel patterns of photodamage were detected in both water-column
and CSM samples, but peak damage occurred earlier in the day for the CSM samples, suggesting differences in damage and repair
kinetics between the water column and CSM. The results suggest that microorganisms within the CSM are afforded some protection
from UVR stress and that changes in the amount of DNA damage in these organisms may be an indicator of changing UVR stress
to corals.
Received: 10 January 1997 / Accepted: 15 September 1997 相似文献
115.
Ann D. Mitchell Elizabeth L. Evans Mary Margaret Jotz Edward S. Riccio Kristien E. Mortelmans Vincent F. Simmon 《Environment international》1981,5(4-6)
The Saccharomyces cerevisiae D3 recombinogenic assay, the assay for forward mutagenesis in L5178Y mouse lymphoma cells, and the sister chromatid exchange (SCE) assay using Chinese hamster ovary cells were used to evaluate the in vitro mutagenic and DNA-damaging effects of eight samples of diesel engine emissions and related environmental emissions. The recombinogenic assay was not sufficiently sensitive for this evaluation, but mutagenicity was detected in the L5178Y mutagenesis assay following exposures of the cells to all of the emission samples, and DNA damage in the SCE assay was induced by most of the emission samples in the presence and absence of metabolic activation. The observation of positive results in the absence of activation indicated that the samples contained substances that were direct-acting mutagens and DNA-damaging agents. 相似文献
116.
117.
Wolfgang Holzgreve Barry S. Mahony Philip L. Glick Roy A. Filly Michael R. Harrison Alfred A. Delorimier Alfred C. Holzgreve Klaus M. Muller Peter W. Callen Robert L. Anderson Mitchell S. Golbus 《黑龙江环境通报》1985,5(4):245-257
Six cases of sonographically diagnosed fetal sacrococcygeal teratoma (SCT) are presented and illustrate the variable features of fetal SCT. The sonographic findings assisted the parents and perinatal team in making decisions, and in two of the cases the children survived after elective Cesarean section and prompt neonatal resection of the tumors. None of the patients showed signs of malignant degeneration of the teratoma or metastases. Fetal SCT no longer should be considered a uniformly fatal condition. The literature on sacrococcygeal teratoma detected after birth indicates that the mortality rate is correlated with the degree of extension of the tumor. Therefore, the classification of sonographically diagnosed fetal SCT according to its size and position is important for decisions regarding pregnancy management. 相似文献
118.
Peter A. Benn Mitchell Sugarman M. Alba Greco Gloria Harris George B. Deguire Lillian Y. F. Hsu 《黑龙江环境通报》1982,2(4):309-312
The first prenatally diagnosed case of 49,XXXYY is reported. The pathological findings of the fetus included bilateral clinodactyly, decreased carrying angles (OO), and hypertelorism, slightly low set ears and mildly prominent forehead. A minimum of two independent non- disjunctional events are postulated for this polysomy to arise. 相似文献
119.
Dr Mitchell S. Golbus Joe Leigh Simpson Sarah E. Fowler Felix de la Cruz Robert J. Desnick Ronald Wapner David H. Ledbetter Herbert Lubs Maurice J. Mahoney Eugene Pergament George G. Rhoads Joseph D. Schulman Julia Zachary 《黑龙江环境通报》1992,12(5):373-376
Factors found to be associated with pregnancy loss after transcervical CVS were race (higher for non-white), history of spontaneous abortion, unplanned pregnancy, history of spotting or bleeding during the pregnancy prior to CVS, and placental position (higher for fundal or lateral locations). Whether the increase in loss risk is due to the factor, per se, or the factor plus the CVS cannot be determined due to the lack of appropriate control data. 相似文献
120.
Mitchell ER 《Journal of environmental science and health. Part. B》2002,37(3):277-290
Experiments were conducted in plantings of cabbage in spring 1999 and 2000 to evaluate a novel, new matrix system for delivering sex pheromone to suppress sexual communication by diamondback moth, Plutella xylostella (L.). The liquid, viscous, slow-release formulation contained a combination of diamondback moth pheromone, a blend of Z-11-hexadecenyl acetate, 27%:Z-11-hexadecen-1-ol, 1%:Z-11-tetradecen-1-ol, 9%:Z-11-hexadecenal, 63%, and the insecticide permethrin (0.16% and 6% w/w of total formulated material, respectively). Field trapping experiments showed that the lure-toxicant combination was highly attractive to male moths for at least four weeks using as little as a 0.05 g droplet of formulated material per trap; and the permethrin insecticide had no apparent influence on response of moths to lure baited traps. Small field plots of cabbage were treated with the lure-toxicant-matrix combination using droplets of 0.44 and 0.05 g each applied to cabbage in a grid pattern at densities ranging from 990 to 4396 droplets/ha to evaluate the potential for disrupting sexual communication of diamondback moth. There was no significant difference in the level of suppression of sexual communication of diamondback moth, as measured by captures of males in pheromone-baited traps located in the treated plots, versus moths captured in untreated control plots, among the treatments regardless of droplet size (0.05 or 0.44 g) or number of droplets applied per ha. Plots treated with the smallest droplet size (0.05 g) and with the fewest number of droplets per ha (990) suppressed captures of male diamondback moths > 90% for up to 3 weeks post treatment. Although laboratory assays showed that the lure-toxicant combination was 100% effective at killing the diamondback moth, the mode of action in the field trials was not determined. The results indicate that the liquid, viscous, slow release formulation containing diamondback moth pheromone could be used to effectively suppress sexual communication of this pest in cabbage and other crucifers, although as many as three applications probably would be required for suppression over an entire growing season. 相似文献