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571.
A study of phosphate assimilation by coastal marine plankton revealed that both phytoplankton and microheterotrophs incorporated radioactive phosphorus (33P). Size fractionation of the particulate matter (using 1 m pore diameter Nucleopore® membrane filters), antibiotic treatment (using garamycin), and independent estimaties of photoautotrophic (14CO2 uptake) and heterotrophic (3H-glucose uptake) activities were employed to separate phyto- and bacterioplankton phosphate uptake. Results indicated that phytoplankton 33P-uptake was best estimated by the fraction of particulate matter retained on the 1 m membrane filters. Usually, less than 10% of the phytoplankton (based on chlorophyll a measurements) passed the 1 m pore-diameter filters, whereas about 90% of the heterotrophic activity passed. At least 50% of the 33P-uptake was associated with the <1 m fraction. It may be possible to resolve the phytoplankton and bacterial contributions to 33P-uptake by comparing the percent of total 33P-uptake with the percent of total 3H-glucose uptake associated with the >1 m fraction. 相似文献
572.
Boris M. Petrikovsky MD Phd Margaret I. Cuomo Elizabeth P. Schneider Linda J. Wyse Harris L. Cohen Martin Lesser 《黑龙江环境通报》1995,15(9):827-829
The aim was to assess the role that fetal bladder size has in the determination of fetal hydronephrosis. Forty-three fetuses were evaluated for fetal hydronephrosis in the second trimester of pregnancy. Anteroposterior measurements of the renal pelvis were obtained with a full bladder and again when the bladder emptied in each fetus. Statistical analysis was performed using the Spearman rank order correlation coefficient to assess the relationship between bladder status and renal dilation. The anteroposterior size of the fetal renal pelvis diminished from 6.8 ± 1.8 mm on a full bladder scan to 4.5 ± 1.6 mm when the bladder was emptied (P<0.001). Fifty-three per cent of the fetuses whose renal pelvic measurements were 5 mm or more on a full bladder scan had normal-appearing renal pelvises when their bladders emptied. The status of the fetal bladder should be considered when evaluating fetal hydronephrosis. 相似文献
573.
Dr. Elizabeth J. T. Winsor B. St. John Brown Edwin R. Luther Stephen A. Heifetz J. Philip Welch 《黑龙江环境通报》1987,7(7):485-489
A pregnancy was terminated because of persistently elevated amniotic fluid AFP (+10 S.D.) and an AChE band of low intensity on gel electrophoresis. No fetal anomalies were detected by ultrasonographic examination. Autopsy revealed an apparently normal fetus of about 20 weeks gestation. Attached to the placenta was a small sac containing a fetus papyraceus co-twin of about 8–9 weeks gestation. The small deceased co-twin and its gestational sac were not detected prenatally despite multiple ultrasonographic examinations. The difficulty in the interpretation of apparently conflicting results is emphasized. 相似文献
574.
Nitrogen inputs to the US from human activity doubled between 1961 and 1997, with most of the increase in the 1960s and 1970s. The largest increase was in use of inorganic N fertilizer, but emissions of NOx from fossil-fuel combustion also increased substantially. In 1961, N fixation in agricultural systems was the largest single source of reactive N in the US. By 1997, even though N fixation had increased, fertilizer use and NOx emissions had increased more rapidly and were both larger inputs. In both 1961 and 1997, two thirds of reactive N inputs were denitrified or stored in soils and biota, while one third was exported. The largest export was in riverine flux to coastal oceans, followed by export in food and feeds, and atmospheric advection to the oceans. The consumption of meat protein is a major driver behind N use in agriculture in the US Without change in diet or agricultural practices, fertilizer use will increase over next 30 years, and fluxes to coastal oceans may increase by another 30%. However, substantial reductions are possible. 相似文献
575.
Little EE Calfee RD Fabacher DL Carey C Blazer VS Middleton EM 《Environmental science and pollution research international》2003,10(3):167-172
Background Exposure to harmful levels of ultraviolet-B radiation (UVB), a component of solar radiation, has been suggested as a potential
cause of amphibian declines.
Methods We measured solar radiation (UVB, ultraviolet-A, and visible) wavebands in breeding ponds of Bufo boreas (boreal toad, a montane species that has undergone severe population declines) and Bufo woodhousii (Woodhouse’s toad, a plains toad that has not experienced declines) and examined tolerances of these species to simulated
solar UVB exposures in the laboratory.
Results We found larvae of both species to be tolerant of simulated solar UVB in excess of solar UVB levels observed in their breeding
ponds. B. boreas tadpoles were more tolerant of simulated solar UVB exposure than B. woodhousii tadpoles, possibly because of greater amounts of photoprotective melanin in B. boreas skin.
Conclusions UVB levels observed in B. boreas habitats do not currently appear to constitute a threat to the survival of these animals; however, long-term (>1 month) exposure
to UVB levels comparable to levels associated with the water interface appears to reduce survival in B. woodhousii tadpoles. Therefore, future increases in surface and water column UVB radiation in bufonid habitats might pose significant
survival risks to B. boreas or B. woodhousii populations. 相似文献
576.
Brooks BW Turner PK Stanley JK Weston JJ Glidewell EA Foran CM Slattery M La Point TW Huggett DB 《Chemosphere》2003,52(1):135-142
Ecological risk assessments of pharmaceuticals are currently difficult because little-to-no aquatic hazard and exposure information exists in the peer-reviewed literature for most therapeutics. Recently several studies have identified fluoxetine, a widely prescribed antidepressant, in municipal effluents. To evaluate the potential aquatic toxicity of fluoxetine, single species laboratory toxicity tests were performed to assess hazard to aquatic biota. Average LC(50) values for Ceriodaphnia dubia, Daphnia magna, and Pimephales promelas were 0.756 (234 microg/l), 2.65 (820 microg/l), and 2.28 microM (705 microg/l), respectively. Pseudokirchneriella subcapitata growth and C. dubia fecundity were decreased by 0.044 (14 microg/l) and 0.72 microM (223 microg/l) fluoxetine treatments, respectively. Oryias latipes survival was not affected by fluoxteine exposure up to a concentration of 28.9 microM (8.9 mg/l). An LC(50) of 15.2 mg/kg was estimated for Chironomus tentans. Hyalella azteca survival was not affected up to 43 mg/kg fluoxetine sediment exposure. Growth lowest observed effect concentrations for C. tentans and H. azteca were 1.3 and 5.6 mg/kg, respectively. Our findings indicate that lowest measured fluoxetine effect levels are an order of magnitude higher than highest reported municipal effluent concentrations. 相似文献
577.
Perez-Perez E Rodríguez-Malaver AJ 《Journal of environmental biology / Academy of Environmental Biology, India》2005,26(3):603-608
The effect of Kraft black liquor on the lipid peroxidation of rat homogenates was examined. The lipid peroxidation of homogenates from different organs (kidney, brain, lung, and liver) was induced by Fenton's reagent. The products of lipid peroxidation, lipid hydroperoxides and TBARS were measured by FOX method and TBA assay, respectively. It was found that black liquor significantly reduced the concentration of TBARS, but not the concentration of lipid hydroperoxides. This inhibition was directly proportional to the concentration of Kraft black liquor and the incubation temperature. Conclusively, the black liquor from pulp and paper industry exhibited an antioxidant activity. 相似文献
578.
Is There a Link between Wild Meat and Food Security? 总被引:2,自引:0,他引:2
Elizabeth L. Bennett 《Conservation biology》2002,16(3):590-592
579.
Elizabeth Kline 《Local Environment》2000,5(3):343-350
Eco-cities strive to become more liveable, enjoyable, and healthy. Indicators can be an effective mechanism for understanding people's values, needs, concerns, and expectations; guiding development decisions; evaluating progress and making revisions; and gaining support for desired actions. This Viewpoint describes how sustainability indicators can be developed to measure a community's environment, economy, quality of life, and governance. Five helpful hints are offered to guide this process. 相似文献
580.