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211.
Killifish () were exposed in the laboratory to pentachlorophenol (PCP) at concentrations of 57 to 610 μg PCP/L. Bioaccumulation reached a plateau value of about 53 by 168 hrs and remained at this level for at least 72 hrs. One-half the plateau value was reached in about 25 hrs. Following exposure, fish placed in PCP-free aquaria lost PCP rather slowly (). The depuration data were suggestive of a pool of PCP which was lost more rapidly (). The results of this study are compared to similar studies in other species. The bioaccumulation factors measured in this study agree relatively well with those in other marine species, but are lower than reported for fresh water species. Possible reasons for this difference are discussed. 相似文献
212.
Emissions from a 1988 GM Corsica with adaptive learning closed loop control were measured with 4 fuels at 40, 75, and 90 degrees F. Evaporative and exhaust emissions were examined from each fuel at each test temperature. Test fuels were unleaded summer grade gasoline; a blend of this gasoline containing 8.1 percent ethanol; a refiner's blend stock; and the blend stock containing 16.2 percent methyl tertiary butyl ether. The ethanol and MTBE blends contained 3.0 percent oxygen by weight. Regulated emissions (total hydrocarbons, carbon monoxide, and oxides of nitrogen), detailed aldehydes, detailed hydrocarbons, ethanol, MTBE, benzene, and 1,3-butadiene were determined. The highest levels of regulated emissions were produced at the lower temperature. Blended fuels produced almost twice the evaporative hydrocarbon emissions at high temperatures as did the base fuels. Benzene emissions varied with fuels and operating temperatures, while 1,3-butadiene emissions decreased slightly with increasing temperatures. Formaldehyde emissions were not sensitive to fuel or temperature changes. Ethanol fuel blend total aldehyde emissions increased by 40 percent due to increased acetaldehyde emissions. Fuel blends had approximately a 3 percent economy decrease. The MTBE fuel blend appeared to offer the most reduction in total hydrocarbon, carbon monoxide, and oxides of nitrogen for the fuels and temperatures tested. 相似文献
213.
Hugh A. Ford Harry Bell Ray Nias Richard Noske 《Behavioral ecology and sociobiology》1988,22(4):239-249
Summary Australia has many cooperatively breeding species of birds. These tend to occur in eucalypt and semi-arid woodlands rather than in rainforests or deserts. They tend to be insectivores that pursue rather than sit and wait for their prey, and tend to forage on the ground rather than above it. We propose that environments where resources do not show marked seasonal fluctuations are those in which cooperative breeding is most likely to evolve. Under these conditions birds might experience difficulty acquiring the extra food necessary to breed, especially if inexperienced. When adult survival was high, young and inexperienced birds could delay breeding. Unpredictable environments may also favor cooperative breeding, but our data do not strongly support this. Groupliving would be favored further if young birds are particularly vulnerable to predators when alone. They should therefore remain in the family group and delay their dispersal unitl a suitable breeding vacancy becomes available. These hypotheses are not mutually exclusive, but are complementary. Both may be required to ensure that at least some year-old birds do not breed and also do not disperse. We believe that they give rise to predictions, which can be tested in future field studies. 相似文献
214.
S. P. Pathak Sanjay Kumar P. W. Ramteke R. C. Murthy K. P. Singh J. W. Bhattacherjee P. K. Ray 《Environmental monitoring and assessment》1992,22(3):227-236
Water samples from 30 rivers in northern and north-eastern hilly states of India were analysed for bacteriological and physicochemical parameters along with metals and pesticide residues. It was found that 34% of samples had >50 coliforms/100 ml, while 24% of samples demonstrated >50 thermotolerant (faecal) coliforms/100 ml. Among the metals, iron was found to be above maximum permissible limits in the rivers of all the states, while manganese was found to be above the maximum permissible limit in the rivers of Tripura and some northern states. Zinc, lead, nickel, chromium, copper, cobalt and cadmium plus physicochemical parameters and residual pesticides, however, were within their maximum permissible limits. 相似文献
215.
216.
Vaishali Sharda Prasanna H. Gowda Gary Marek Isaya Kisekka Chittaranjan Ray Pradip Adhikari 《Journal of the American Water Resources Association》2019,55(1):56-69
There is an increasing need to strategize and plan irrigation systems under varied climatic conditions to support efficient irrigation practices while maintaining and improving the sustainability of groundwater systems. This study was undertaken to simulate the growth and production of soybean [Glycine max (L.)] under different irrigation scenarios. The objectives of this study were to calibrate and validate the CROPGRO‐Soybean model under Texas High Plains’ (THP) climatic conditions and to apply the calibrated model to simulate the impacts of different irrigation levels and triggers on soybean production. The methodology involved combining short‐term experimental data with long‐term historical weather data (1951–2012), and use of mechanistic crop growth simulation algorithms to determine optimum irrigation management strategies. Irrigation was scheduled based on five different plant extractable water levels (irrigation threshold [ITHR]) set at 20%, 35%, 50%, 65%, and 80%. The calibrated model was able to satisfactorily reproduce measured leaf area index, biomass, and evapotranspiration for soybean, indicating it can be used for investigating different strategies for irrigating soybean in the THP. Calculations of crop water productivity for biomass and yield along with irrigation water use efficiency indicated soybean can be irrigated at ITHR set at 50% or 65% with minimal yield loss as compared to 80% ITHR, thus conserving water and contributing toward lower groundwater withdrawals. Editor's note: This paper is part of the featured series on Optimizing Ogallala Aquifer Water Use to Sustain Food Systems. See the February 2019 issue for the introduction and background to the series. 相似文献
217.
Ziming Zhao Wenjun Sun Madhumita B. Ray Ajay K Ray Tianyin Huang Jiabin Chen 《Frontiers of Environmental Science & Engineering》2019,13(5):75
218.
Fenitrothion, an acetylcholinesterase inhibitor, causes bradycardia following long‐term exposure. To analyse the mechanism underlying these cardiac changes, ginea pigs were exposed to fenitrothion 5 and 10 mg/kg for 30 consecutive days. Electrocardiogram (ECG) showed increase in PR and RR intervals. These changes were more prominent in the animals receiving 10 mg/kg fenitrothion which occasionally showed extrasystoles. In isolated atria preparation heart rate was decreased at higher dose. Amplitude of cardiac rhythm decreased with respect to increased ACh concentration. Hypocalcemia was recorded in fenitrothion‐treated animals. The residual content of fenitrothion was increased in both groups of animals following a pattern: brain> spleen> heart> liver> kidney. 相似文献
219.
The effect of crosslinkers on the biodegradation behavior of starch/polyvinyl alcohol (PVA) blend films was investigated by weight loss study, Scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). Starch/PVA films were prepared by solution casting method and 5 weight% of four different crosslinking agents like epichlorohydrin, formaldehyde, zinc oxide and borax were used in four different sets to crosslink the films. These crosslinked starch/PVA films were biodegraded in compost. Weight loss study showed that crosslinking retarded the biodegradation of the films in the first 15?days, but after that, there was a significant increase in weight loss. The DSC analysis revealed that the consumption of starch and consequent rearrangement of the PVA molecules were distinctly different in the crosslinked films due to the effect of different crosslinking agents. 相似文献
220.
Hooghly–Matla estuarine ecosystem of India is very rich in natural resources and receives large amount of nutrients through litterfall from adjacent mangrove forest. Nitrogen as an important nutrient occurs in various forms and plays a crucial role in the regulation of productivity in this estuarine system. Modelling of nitrogen dynamics from mangrove litterfall and particularly the release of dissolved inorganic nitrogen in this estuarine system is important because of its role in augmenting growth of phytoplankton and other higher plants and all other biological components of grazing food chain. 相似文献