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281.
Summary Dwarf mongooses in the Taru desert region of Kenya form foraging communities with a variety of endemic bird species, especially hornbills. The prey spectra of the mongooses and hornbills overlap almost completely. For the other bird species forming the foraging community only partial overlap exists. The association between the birds and mongooses is actively sought by both parties. The birds wait in tress around the termite mound where the monogooses are sleeping for them to emerge and the mongooses delay their foraging departure if no birds are present. There is a positive relationship between the number of mongooses in the group and the number of birds accompanying them. A true mutualism only exists between the mongooses and the two hornbill species Tockus deckeni and T. flavirostris since their presence or arrival affects the subsequent start of foraging. These two hornbill species have also been observed to influence the start of foraging actively by means of two behaviour patterns termed chivvying and waking. Both the mongooses and birds are exposed to a high predator pressure from raptors with an overlap in the birds of prey predating the various species. This predator pressure is counteracted behaviourally by the mongooses by means of an altruistic behaviour pattern, guarding. Both mongooses and birds warn vocally and flee when a raptor is sighted. The mongooses modify their guarding behaviour to compensate for the warning behaviour of the birds in two ways: (a) fewer mongooses guard when large numbers of birds are present and vice versa, (b) the frequency of the mongooses' intraspecific warning calls is significantly reduced in cases where birds are present in comparison with those where they are absent. The birds also sight and respond to the raptor first on significantly more occasions than the mongooses. In addition, the birds also warn for raptor species which do not predate them but which are mongoose predators, not, however, for raptors which are not mongoose predators. This mutualistic association with its high degree of compensatory behaviour by both parties appears to be unique for free-living vertebrates and has its closest parallel in the trophobiosis described for ants and aphids. 相似文献
282.
283.
Temime B Francois S Monod A Wortham H 《Environmental pollution (Barking, Essex : 1987)》2002,120(3):656-616
The aim of this work is to develop and test a dynamic gas generator for semi-volatile organic compounds (SVOC). A single compound, naphthalene, is used as a surrogate PAH to test the system. The dynamic generation of PAH is based on the permeation technique [Analyst 106 (1981) 817; Am. Ind. Hyg. Assoc. J. 38 (1977) 712]. Monitoring the temperature and measuring the mass of PAH present in the permeation chamber every 48 h gives a direct measurement of the sublimation rate of the PAH. Knowing the flow rate, gives an accurate value of the concentration of PAH from the generator. It was found stable over a period of time under constant operating conditions. This concentration is diluted down to between 0.3 and 30 ppbv by a controlled flow of pure air. The diluting airflow is a mixture of dry and wet air, making it possible to control the relative humidity of the flow from the generator as well as its concentration in PAH. We used this generator to calibrate an annular denuder tube, based on the study by Gundel et al. [Atmos. Environ. 29 (1995) 1719]. Although this technique has been shown to be artefact-free for sampling gaseous PAH [Polycyclic Aromatic Compounds 9 (1996) 67; Atmos. Environ. 28 (1994) 3083], its trapping efficiency still depends on environmental parameters (temperature, relative humidity and sampling duration). Accordingly, we used our generator to calibrate a single annular denuder under controlled conditions (T degrees C, HR%, CPAH, sampling duration). The trapping efficiency of the denuder was calculated by two independent methods. Firstly, by comparing the amount trapped on a denuder with the measured mass sublimated in the generator. Secondly, by putting two denuders in series and comparing the mass collected on the first and the second tube. These two methods gave similar results, within the 10% relative uncertainties of both methods. The first results obtained show that, in environmental conditions, the efficiency ranges between 90 and 100%. 相似文献
284.
Suorsa M Jokela A Sarjala T Manninen S Huttunen S 《Environmental pollution (Barking, Essex : 1987)》2002,119(3):279-281
The study aimed to assess the ozone-induced response in Scots pine (Pinus sylvestris L.) needles by measuring free polyamine concentrations. An open-top chamber experiment with realistically elevated ozone concentrations was carried out in northern Finland. A carry-over effect was detected: the concentrations of free polyamines, especially putrescine, were decreased at the beginning of the next growing season in the ozone-exposed trees. This indicates that the free polyamine pathway was not activated by ozone stress in Scots pines in northern conditions. 相似文献
285.
Recombinant luminescent bacterial sensors for the measurement of bioavailability of cadmium and lead in soils polluted by metal smelters 总被引:9,自引:0,他引:9
Environmental hazard of heavy metals in soils depends to a large extent on their bioavailability. The approach used in this study enables the determination of bioavailable metals in solid-phase samples. Two recombinant bacterial sensors, one responding specifically to cadmium and the other to lead and cadmium by increase of luminescence (firefly luciferase was used as a reporter) were used to determine the bioavailability of these metals in soil-water suspensions (a contact assay) and respective particle-free extracts. Fifty agricultural soils sampled near zinc and lead smelters in the Northern France containing up to (mg/kg) 20.1 of Cd, 1050 of Pb and 1390 of Zn were analysed. As the soil matrix interferes with the assay, recombinant luminescent control bacteria lacking the metal recognizing protein and corresponding promoter (thus, being not metal-inducible) but otherwise comparable to the sensor bacteria (the same host bacterium and plasmid encoding luciferase) were used in parallel to take into account the possible quenching and/or stimulating effects of the sample on the luminescence of the sensor bacteria. Both, chemical and sensor analysis showed that only microg/l levels of metals were extracted from the soil into the water phase (0.1% of the total Cd, 0.07% of Pb and 0.5% of Zn). However, 115-fold more Cd and 40-fold more Pb proved bioavailable if the sensor bacteria were incubated in soil suspensions (i.e., in the contact assay). The bioavailability of metals in different soils varied (depending probably on soil type) ranging from 0.5% to 56% for cadmium and from 0.2% to 8.6% for lead. 相似文献
286.
Summary
Parastizopus armaticeps andEremostibes opacus are two closely related desert tenebrionids which also live in close association, the former having biparental brood care and the latter cleptoparasitising the brood.E. opacus is unable to discriminate between the conspecific and host odour even in the absence of physical contact. Gas chromatographic analysis of headspace volatiles of resting animals showed almost complete qualitative and quantitative odour congruity between them. Comparison of these odour profiles with those of two other tenebrionids sharing the same ecological niche,Gonopus agrestis andHerpiscius sp. (damaralis?) showed that congruity was independent of common foodplant utilisation. It is also independent of common defensive gland secretions. Parallels between resting odour spectra, defensive secretion spectra and systematic status suggest that the origins of congruity lie in odour homology, by means of which the cleptoparasite was able to exploit its host. 相似文献
287.
Scott Nunes Peter A. Zugger Anne L. Engh Kurt O. Reinhart Kay E. Holekamp 《Behavioral ecology and sociobiology》1997,40(3):199-207
We examined the effects of food provisioning on the natal dispersal behavior of Belding's ground squirrels (Spermophilus beldingi). We provided extra food to adult and yearling females in their maternal territories during pregnancy and lactation, and
to offspring of these females in their natal areas for 6 weeks after weaning. We used unprovisioned young of unprovisioned
mothers as controls. Provisioning influenced the probability of dispersal from the natal area by female but not male S. beldingi. All surviving male S.␣beldingi dispersed by 55 weeks of age, regardless of whether they and their mothers received extra food. By contrast, we observed
a significant trend, beginning 3 weeks after weaning and continuing through the yearling year, for a greater proportion of
provisioned than control female S. beldingi to emigrate from the natal area. Competition for food did not appear to influence natal dispersal of females. However, overall
population density, density of females weaning litters, and rates of aggression and vigilance among these females, were higher
in provisioned than control areas, suggesting that competition for non-food resources was unusually intense in provisioned
areas. We propose that juvenile female, but not juvenile male, S. beldingi may emigrate from the natal site to increase access to areas with low densities of conspecifics. Together with findings of
earlier workers, our results suggest that spatial and temporal distributions of environmental resources are important influences
on the dispersal behavior of female ground squirrels.
Received: 28 February 1996 / Accepted after revision: 16 October 1996 相似文献
288.
289.
Ana M. M. Viana Anne Frézard Christian Malosse Terezinha M. C. Della Lucia Christine Errard Alain Lenoir 《Chemoecology》2001,11(1):29-36
Summary. Leaf cutting ants live in symbiosis with a basidiomycete fungus that is exploited as a source of nutrients for the ant larvae.
Tests of fungus transport demonstrated that Acromyrmex subterraneus subterraneus workers discriminate concolonial fungus from alien fungus, and rejected the latter. Larvae and pupae of the ant were used
as controls. Chemical analysis of the fungus revealed a great similarity between its hydrocarbon profile and that found on
the ant brood. Experiments with lures showed that chemical extracts from the fungus are responsible for this discrimination
process. Moreover, the presence of brood inside the fungus seemed to be important for discrimination of the fungus by workers.
Resident workers accepted concolonial broodless fungus less than concolonial fungus inoculated with brood odor. Fungus seems
to acquire colonial odor passively, simply by contact with the brood. The impact of fungus volume present in the nest on closure
of the colony is discussed. We show here for the first time the importance of a symbiotic vegetal organism in colonial recognition
in social insects.
Received 14 April 2000; accepted 29 September 2000 相似文献
290.
Invasion of Exotic Plant Species in Tallgrass Prairie Fragments 总被引:4,自引:0,他引:4