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481.
John H. Christy Patricia R. Backwell Ursula Schober 《Behavioral ecology and sociobiology》2003,53(2):84-91
Male fiddler crabs Uca musica sometimes build sand hoods and male Uca beebei sometimes build mud pillars next to their burrows to which they attract females for mating. Mate-searching females preferentially approach these structures and subsequently mate with structure builders. Here we show that the preference for structures is not species-specific and argue that it may not have evolved for mate choice. When not near burrows, many species of fiddler crabs approach and temporarily hide near objects, suggesting that hoods and pillars may attract females because they elicit this general predator-avoidance behavior. To test this sensory trap hypothesis we individually released female U. musica, U. beebei and Uca stenodactylus, a non-builder, in the center of a circular array of empty burrows to which we added hoods and pillars and then moved a model predator toward the females. All species ran to structures to escape the predator and the two builders preferred hoods. Next, we put hood replicas on male U. beebei burrows and pillar replicas on male U. musica burrows. When courted, females of both species preferentially approached hoods as they did when chased with a predator. However, males of both species with hoods did not have higher mating rates than males with pillars perhaps because hoods block more of a male's visual field so he sees and courts fewer females. Sexual selection may often favor male signals that attract females because they facilitate general orientation or navigation mechanisms that reduce predation risk in many contexts, including during mate search. 相似文献
482.
Dr Christopher J. Danpure Patricia R. Jennings Richard J. Penketh Pauline J. Wise Penelope J. Cooper Charles H. Rodeck 《黑龙江环境通报》1989,9(4):271-281
Primary hyperoxaluria type 1 (PH1) is caused by a deficiency of the hepatic peroxisomal enzyme alanine: glyoxylate aminotransferase (AGT, EC 2.6.1.44) (Danpure and Jennings, FEBS Lett., 201 , 20–24, 1986). The activity of AGT has been measured in fetal livers of gestational age 14–21 weeks. Activity increases up to 17 weeks and then levels off between 17 and 21 weeks. At this time, the mean AGT activity is about 30 per cent of the mean normal postnatal level. As in adult liver, the AGT enzyme activity and the AGT immunoreactive protein are peroxisomal. Prenatal diagnosis has been performed by measuring AGT enzyme activity and immunoreactive AGT protein on liver biopsies from two fetuses at risk for primary hyperoxaluria type 1. One was unaffected and one was affected. 相似文献
483.
Deficiency of amylo-1,6–glucosidase activity was expressed in parallel in liver and skin fibroblasts from a patient with type III glycogenosis. In crude extracts of control liver and muscle, amylo-1, 6–glucosidase (M.W. 164000) was identified by immunoprecipitation; no cross-reacting material was found in the patient's liver. Assay of amylo-1,6–glucosidase activity in cultured skin fibroblasts from the affected family revealed less than 10 per cent of control value in mutant homozygous cells whereas in cells from the parents, activity was reduced to 40–60 per cent of the control value. Activity in cultured amniotic fluid cells was similar to that of control fibroblasts. In cultured amniotic fluid cells obtained during the mother's subsequent pregnancy, the normal amylo–1,6–glucosidase activity measured, predicted correctly the outcome of this pregnancy prior to the 20th week of gestation. 相似文献
484.
485.
Avifaunal responses to fire in southwestern montane forests along a burn severity gradient. 总被引:1,自引:0,他引:1
The effects of burn severity on avian communities are poorly understood, yet this information is crucial to fire management programs. To quantify avian response patterns along a burn severity gradient, we sampled 49 random plots (2001-2002) at the 17351-ha Cerro Grande Fire (2000) in New Mexico, USA. Additionally, pre-fire avian surveys (1986-1988, 1990) created a unique opportunity to quantify avifaunal changes in 13 pre-fire transects (resampled in 2002) and to compare two designs for analyzing the effects of unplanned disturbances: after-only analysis and before-after comparisons. Distance analysis was used to calculate densities. We analyzed after-only densities for 21 species using gradient analysis, which detected a broad range of responses to increasing burn severity: (I) large significant declines, (II) weak, but significant declines, (III) no significant density changes, (IV) peak densities in low- or moderate-severity patches, (V) weak, but significant increases, and (VI) large significant increases. Overall, 71% of the species included in the after-only gradient analysis exhibited either positive or neutral density responses to fire effects across all or portions of the severity gradient (responses III-VI). We used pre/post pairs analysis to quantify density changes for 15 species using before-after comparisons; spatiotemporal variation in densities was large and confounded fire effects for most species. Only four species demonstrated significant effects of burn severity, and their densities were all higher in burned compared to unburned forests. Pre- and post-fire community similarity was high except in high-severity areas. Species richness was similar pre- and post-fire across all burn severities. Thus, ecosystem restoration programs based on the assumption that recent severe fires in Southwestern ponderosa pine forests have overriding negative ecological effects are not supported by our study of post-fire avian communities. This study illustrates the importance of quantifying burn severity and controlling confounding sources of spatiotemporal variation in studies of fire effects. After-only gradient analysis can be an efficient tool for quantifying fire effects. This analysis can also augment historical data sets that have small samples sizes coupled with high non-process variation, which limits the power of before-after comparisons. 相似文献
486.
Stream ecosystem response to limestone treatment in acid impacted watersheds of the Allegheny Plateau. 总被引:1,自引:0,他引:1
Sarah E McClurg J Todd Petty Patricia M Mazik Janet L Clayton 《Ecological applications》2007,17(4):1087-1104
Restoration programs are expanding worldwide, but assessments of restoration effectiveness are rare. The objectives of our study were to assess current acid-precipitation remediation programs in streams of the Allegheny Plateau ecoregion of West Virginia (USA), identify specific attributes that could and could not be fully restored, and quantify temporal trends in ecosystem recovery. We sampled water chemistry, physical habitat, periphyton biomass, and benthic macroinvertebrate and fish community structure in three stream types: acidic (four streams), naturally circumneutral (eight streams), and acidic streams treated with limestone sand (eight streams). We observed no temporal trends in ecosystem recovery in treated streams despite sampling streams that ranged from 2 to 20 years since initial treatment. Our results indicated that the application of limestone sand to acidic streams was effective in fully recovering some characteristics, such as pH, alkalinity, Ca2+, Ca:H ratios, trout biomass and density, and trout reproductive success. However, recovery of many other characteristics was strongly dependent upon spatial proximity to treatment, and still others were never fully recovered. For example, limestone treatment did not restore dissolved aluminum concentrations, macroinvertebrate taxon richness, and total fish biomass to circumneutral reference conditions. Full recovery may not be occurring because treated streams continue to drain acidic watersheds and remain isolated in a network of acidic streams. We propose a revised stream restoration plan for the Allegheny Plateau that includes restoring stream ecosystems as connected networks rather than isolated reaches and recognizes that full recovery of acidified watersheds may not be possible. 相似文献
487.
Summary Behavior of mice whose T-locus genotype was either +/+ or +/t was observed in a seminatural environment. Heterozygous females were less likely to be dominant, less likely to go into behavioral estrus, and less likely to become pregnant than were +/+ females. The relative fitness of +/t as compared with +/+ females was 0.32:1.00. In contrast, +/t males produced 35% more young than did +/+ males. The higher fitness of +/t males was primarily due to a greater production of young on the part of +/t as compared with +/+ subordinate males. Little evidence was found under these naturalistic conditions, of non-random mating with respect to T-locus genotype. The indication of overdominance for +/t males makes it unlikely that heterozygote disadvantage will be sufficient to account for the frequency of t-alleles in natural populations. 相似文献
488.
The fiddler crab Uca perplexa has a conspicuous male courtship signal that is directed at females to attract them to the male’s burrow for mating. The signal involves waving the unflexed large claw up and down. To determine whether the spatiotemporal structure of the wave is under selection by female choice, we examined whether females had a preference for any particular features of the wave. Females respond to a waving display by either visiting the male’s burrow entrance or by electing to pass without visiting the burrow. We filmed mate-searching females and the waving males that they visited or passed. We documented the wave structure of these males using frame-by-frame analysis. Males produce a two-part wave with component A preceding component B. Both components have an upstroke, a pause at the apex and a downstroke. The tip of the claw was raised much higher in B than in A. Visited males had a shorter delay between the two wave components than did males that the females passed without visiting. Visited males also produced component B waves that had a slower upstroke than those of passed males. There was a significant correlation between the relative height of the raised claw and the duration of the upstroke of component B. Females were selecting males that raised their major claw to the highest position (two to three times as high as the carapace width). Passed males brought down their major claw earlier and from a lower position than did visited males. The data suggests that wave structure has evolved through female choice. Male display rate and body size were not female choice cues. An earlier study showed that display duration was also not used by females in selecting mates. 相似文献
489.
Patricia A. Tester 《Marine Biology》1985,89(1):45-53
Experimental results indicate that both parental acclimation temperature and egg-incubation temperature have significant effects on the egg-hatching time of Acartia tonsa Dana between 15° and 25°C. Effects of parental acclimation temperature and egg-incubation temperature are additive if the long-term parental acclimation temperature is constant. A. tonsa are sensitive to temperature and changes of temperature during development (in vivo) and after they are laid (in vitro), up to the time of hatching. A temperature change of the parent culture for time periods of 86 h to 8 d is sufficient to change egg-hatching times. The time required for a temperature change to affect egg-hatching times depends on the magnitude and direction of the temperature change. Field collected A. tonsa demonstrate that changes in egg-hatching times occur in the field populations and can be predicted by mean weekly water temperature. 相似文献
490.
J. Haydock Patricia G. Parker Kerry N. Rabenold 《Behavioral ecology and sociobiology》1996,38(1):1-16
We investigated parentage using multilocus DNA fingerprinting for 222 juveniles produced during 99 group-years in the bicolored
wren Campylorhynchus griseus, a cooperatively breeding bird of the Venezuelan savanna. Young adult bicolored wrens (auxiliaries) remain in their natal
territories and substantially enhance the production of young there. We have previously used behavioral indicators of dominance
by a single male/female pair (principals) to infer breeding status, resulting in the commonly applied model of helping in
which current fitness accrues to auxiliaries only indirectly, in proportion to their relatedness to the principals and the
effect of their assistance on breeding success. Our parentage analysis has demonstrated that 8.6% of the juveniles found on
territories were not produced by the principal pair. Parentage of 4.1% of the juveniles was completely outside the social
group; these appear to result from early dispersal of juveniles rather than from brood parasitism, most likely resulting from
breakup of nearby groups. Principal females mated outside of their group (2.3%), or with an auxiliary male (2.3%), in the
remaining cases of parentage outside the principal pair. No matings were detected between close relatives (e.g. mother-son);
matings detected between the principal female and an auxiliary male followed a typical replacement of the principal female
by an unrelated immigrant female. Our finger-printing results indicate that: (1) current fitness benefits accruing to most
auxiliaries do not exceed their likely reproductive success had they dispersed successfully to a breeding position; (2) nearly
all wren mating is monogamous and (3) behavioral dominants (especially females) can monopolize breeding.
Received: 23 September 1994/Accepted after revision: 10 June 1995 相似文献