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191.
Michael W. Butler Matthew B. Toomey Kevin J. McGraw 《Behavioral ecology and sociobiology》2011,65(2):401-413
For a variety of technical and conceptual reasons, biologists have come to use several different methods to quantify the colors
of animals. However, the relative abilities of these different color-scoring procedures to capture variation in the actual
color-generating mechanisms—pigment or structural composition of the integument—have never been tested systematically. Here,
we examined which commonly employed color metrics predict carotenoid content of ornaments in three avian species (house finch
Carpodacus mexicanus, mallard duck Anas platyrhynchos, and zebra finch Taeniopygia guttata). We used spectrophotometry to measure reflectance spectra from beak and feather tissue, calculated numerous color metrics
(e.g., hue, chroma, brightness, principal components, and tetrahedral color space position) from these spectra, and determined
carotenoid content at the site of color measurement with high-performance liquid chromatography. We found that several principal
component, tristimulus, and avian visual model metrics significantly correlated with carotenoid content of house finch feathers
and duck beaks. Carotenoid content of mallard beaks was most closely correlated with brightness and saturation metrics, whereas
in house finch feathers, carotenoid concentration was best captured by hue and saturation metrics. According to tristimulus
scores and visual models, we found that the ultraviolet portion of the spectrum was not an essential predictor of variation
in carotenoid content. Also, visual model chromatic contrasts generally were not significant predictors of carotenoid content,
although some achromatic contrasts and tetrahedral color space vector parameters were. Our results indicate that numerous
methods, especially tristimulus scores, are suitable for capturing pigment-based color variation in two carotenoid-containing
ornaments, and we discuss the merits and shortcomings of these different approaches. In contrast, there were no significant
relationships between any color metrics and the carotenoid content of zebra finch beaks, suggesting that other color-generating
mechanisms besides carotenoids may contribute to color variability in this species. 相似文献
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194.
Seaweed diversity enhances nitrogen uptake via complementary use of nitrate and ammonium 总被引:1,自引:0,他引:1
The consequences of declining biodiversity remain controversial, in part because many studies focus on a single metric of ecosystem functioning and fail to consider diversity's integrated effects on multiple ecosystem functions. We used tide pool microcosms as a model system to show that different conclusions about the potential effects of producer diversity on ecosystem functioning may result when ecosystem functions are measured separately vs. together. Specifically, we found that in diverse seaweed assemblages, uptake of either nitrate or ammonium alone was equal to the average of the component monocultures. However, when nitrate and ammonium were available simultaneously, uptake by diverse assemblages was 22% greater than the monoculture average because different species were complementary in their use of different nitrogen forms. Our results suggest that when individual species have dominant effects on particular ecosystem processes (i.e., the sampling effect), multivariate complementarity can arise if different species dominate different processes. Further, these results suggest that similar mechanisms (complementary nutrient uptake) may underlie diversity-functioning relationships in both algal and vascular-plant-based systems. 相似文献
195.
Separate effects of ammonium (NH4+) and nitrate (NO3-) on boreal forest understorey vegetation were investigated in an experiment where 12.5 and 50.0 kg nitrogen (N) ha(-1) year(-1) was added to 2 m2 sized plots during 4 years. The dwarf-shrubs dominating the plant community, Vaccinium myrtillus and V. vitis-idaea, took up little of the added N independent of the chemical form, and their growth did not respond to the N treatments. The grass Deschampsia flexuosa increased from the N additions and most so in response to NO3-. Bryophytes took up predominately NH4+ and there was a negative correlation between moss N concentration and abundance. Plant pathogenic fungi increased from the N additions, but showed no differences in response to the two N forms. Because the relative contribution of NH4+ and NO3- to the total N deposition on a regional scale can vary substantially, the N load a habitat can sustain without substantial changes in the biota should be set considering specific vegetation responses to the predominant N form in deposition. 相似文献
196.
Yang K Xu Q Townsend TG Chadik P Bitton G Booth M 《Journal of the Air & Waste Management Association (1995)》2006,56(8):1130-1138
Hydrogen sulfide (H2S) generation in construction and demolition (C&D) debris landfills has been associated with the biodegradation of gypsum drywall. Laboratory research was conducted to observe H2S generation when drywall was codisposed with different C&D debris constituents. Two experiments were conducted using simulated landfill columns. Experiment 1 consisted of various combinations of drywall, wood, and concrete to determine the impact of different waste constituents and combinations on H2S generation. Experiment 2 was designed to examine the effect of concrete on H2S generation and migration. The results indicate that decaying drywall, even alone, leached enough sulfate ions and organic matter for sulfate-reducing bacteria (SRB) to generate large H2S concentrations as high as 63,000 ppmv. The codisposed wastes show some effect on H2S generation. At the end of experiment 1, the wood/drywall and drywall alone columns possessed H2S concentrations > 40,000 ppmv. Conversely, H2S concentrations were < 1 ppmv in those columns containing concrete. Concrete plays a role in decreasing H2S by increasing pH out of the range for SRB growth and by reacting with H2S. This study also showed that wood lowered H2S concentrations initially by decreasing leachate pH values. Based on the results, two possible control mechanisms to mitigate H2S generation in C&D debris landfills are suggested. 相似文献
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198.
Summary. Late instar larvae of the monarch butterfly (Danaus plexippus L., Lepidoptera: Nymphalidae) deactivate the latex defense of milkweeds by chewing a furrow in the leaf midrib or petiole. The larva then feeds beyond the cut where latex outflow is minimal. If a larva does encounter latex exudate during feeding, it often returns to its initial cut to damage the midrib or petiole more extensively before resuming feeding. We used this response to latex as an assay for testing what cue triggers vein cutting. A sticky solution of polyethylene glycol and a mixture of cardenolides both were ineffective; drops applied to the mouthparts of feeding monarchs failed to elicit renewed vein cutting. Activity resided instead within a methanol extract of the supernatant obtained from centrifuged latex of the milkweed, Asclepias curassavica L. (Asclepiadaceae). Treatment with proteinase K did not eliminate activity documenting that the active compound is unlikely to be proteinaceous. Our results indicate that latex adhesiveness and low polarity cardenolides are relatively unimportant releasers of vein cutting. We propose that milkweeds contain noncardenolide stimulants of vein cutting; these compounds presumably serve a defensive role for milkweeds. Over 50 species of insects are known to employ vein-cutting before feeding on plants with canal-borne exudates; most of these species are dietary specialists like the monarch. Our behavioral assay provides a novel approach for identifying ecologically-significant compounds in the exudates of their diverse host plants. 相似文献
199.
Efforts to increase the use of waste materials as substitutes for virgin primary materials in industry are considered an important step toward sustainable industrial development. Some industries, however, have struggled to increase the recycling of materials for a variety of reasons. This study proposes a new approach to searching for recycling across industry boundaries. By focusing on an entire industry, the locations where economic and environmental benefit exists can be identified. This research identifies brick manufacturing facilities in the United States that are most likely to gain substantial economic benefit from the recycling of waste products. The results of this case study indicate that an industry-based approach can provide economically feasible pathways towards sustainable industrial development, especially for data rich manufacturing nations like the United States. 相似文献
200.