全文获取类型
收费全文 | 134篇 |
免费 | 0篇 |
国内免费 | 1篇 |
专业分类
安全科学 | 2篇 |
环保管理 | 4篇 |
综合类 | 10篇 |
基础理论 | 114篇 |
灾害及防治 | 5篇 |
出版年
2021年 | 1篇 |
2012年 | 1篇 |
2011年 | 1篇 |
2010年 | 1篇 |
2009年 | 9篇 |
2008年 | 8篇 |
2007年 | 17篇 |
2006年 | 9篇 |
2005年 | 9篇 |
2004年 | 10篇 |
2003年 | 4篇 |
2002年 | 2篇 |
2001年 | 4篇 |
2000年 | 6篇 |
1999年 | 6篇 |
1998年 | 6篇 |
1997年 | 4篇 |
1996年 | 7篇 |
1995年 | 7篇 |
1994年 | 8篇 |
1993年 | 7篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 3篇 |
排序方式: 共有135条查询结果,搜索用时 78 毫秒
91.
Cuckoo growth performance in parasitized and unused hosts: not only host size matters 总被引:4,自引:0,他引:4
Tomáš Grim 《Behavioral ecology and sociobiology》2006,60(5):716-723
The quality and quantity of food delivered to young are among the major determinants of fitness. A parental provisioning capacity is known to increase with body size. Therefore, brood parasitism provides an opportunity to test the effects of varying provisioning abilities of different-sized hosts on parasitic chick growth and fledging success. Knowledge of growth patterns of common cuckoo, Cuculus canorus, chicks in nests of common hosts is very poor. Moreover, no study to date has focused on any currently unused hosts (i.e., suitable cuckoo host species in which parasitism is currently rare or absent). Here, I compare the growth performance of cuckoo chicks in nests of a common host (the reed warbler, Acrocephalus scirpaceus) and two unparasitized hosts (the song thrush, Turdus philomelos, and the blackbird, Turdus merula). Parasitic chicks were sole occupants of the observed nests, thus eliminating the confounding effect of competition with host chicks. Experiments revealed striking differences in parasitic chick growth in the two closely related Turdus hosts. Cuckoo chicks cross-fostered to song thrush nests grew much quicker and attained much higher mass at fledging than those in nests of their common reed warbler host. Alternatively, parasitic chicks in blackbird nests grew poorly and did not survive until fledging. I discuss these observations with respect to host selection by parasitic cuckoos. 相似文献
92.
Summary. Qualitative and quantitative differences among pear cultivars were found
in constitutive and Cacopsylla-induced volatiles, depending on
experimental treatment of the trees (i.e., uninfested and partly or
completely infested by psyllids). Blend differences were also found
between pear cultivars and wild-type pear, alder and hawthorn–the
latter trees are frequently present in pear orchard
hedgerows. ?Interesting differences were found in the presence of methyl
salicylate and (E,E)-α-farnesene, two compounds previously found to
mediate attraction of predatory bugs towards psyllid-infested pear
trees. Methyl salicylate is expressed constitutively and is induced
systemically by infestation in the whole plant of all four cultivars.
(E,E)-α-farnesene on the other hand showed also systemic induction in
Bartlett, NY10355 and Beurré Hardy, but in partially infested Conference
trees it was induced locally, only in herbivore-damaged leaves. No
methyl salicylate or (E,E)-α-farnesene were identified in honeydew. In
field collected headspace samples of alder leaves infested by aphids and
leaf beetles we found methyl salicylate but no (E,E)-α-farnesene,
whereas in uninfested hawthorn neither were identified. Insight in the
variability of damage-related pear volatiles will have important
implications for integrated pest management in the field.
Received 27 August 2002; accepted 28 November 2002
R1D="
Correspondence to: Petru Scutareanu, e-mail:scuterea@science.uva.nl 相似文献
93.
Foraging behavior and the mechanisms that regulate foraging activity are important components of social organization. Here
we test the hypothesis that brood pheromone modulates the sucrose response threshold of bees. Recently the honeybee proboscis
extension response to sucrose has been identified as a ”window” into a bee’s perception of sugar. The sucrose response threshold
measured in the first week of adult life, prior to foraging age, predicts forage choice. Bees with low response thresholds
are more likely to be pollen foragers and bees with high response thresholds are more likely to forage for nectar. There is
an associated genetic component to sucrose response thresholds and forage choice such that bees selected to hoard high quantities
of pollen have low response thresholds and bees selected to hoard low quantities of pollen have higher response thresholds.
The number of larvae in colonies affects the number of bees foraging for pollen. Hexane-extractable compounds from the surface
of larvae (brood pheromone) significantly increase the number of pollen foragers. We tested the hypothesis that brood pheromone
decreases the sucrose response threshold of bees, to suggest a pheromone- modulated sensory-physiological mechanism for regulating
foraging division of labor. Brood pheromone significantly decreased response thresholds as measured in the proboscis extension
response assay, a response associated with pollen foraging. A synthetic blend of honeybee brood pheromone stimulated and released
pollen foraging in foraging bioassays. Synthetic brood pheromone had dose-dependent effects on the modulation of sucrose response
thresholds. We discuss how brood pheromone may act as a releaser of pollen foraging in older bees and a primer pheromone on
the development of response thresholds and foraging ontogeny of young bees.
Received: 24 May 2000 / Revised: 26 September 2000 / Accepted: 15 October 2000 相似文献
94.
重视减灾投入,增强灾害防御能力 总被引:1,自引:0,他引:1
本文从加强灾害防御的重要意义、忽视防灾的惨痛教训以及减灾的经济效益等几方面论述了要增强灾害防御能力,必须重视减灾的投入,并讨论了如何筹集防灾经费。 相似文献
95.
Ernesto Mollo Margherita Gavagnin Marianna Carbone Yue-Wei Guo Guido Cimino 《Chemoecology》2005,15(1):31-36
Summary. Two Ceratosoma species, C. trilobatum and C. gracillimum (Mollusca: Gastropoda: Opistobranchia), collected along the South China Sea coast, have been studied in order to investigate their defensive strategies. Both species contain four typical sponge furanosesquiterpenoids, probably with a dietary origin. The tissue distribution of these compounds has been studied by 1H-NMR analysis and preliminary bioassays have been carried out in order to evaluate the ecological role of the isolated metabolites. The main sesquiterpene component in both species was (–)-furodysinin (2), which showed significant feeding-deterrent and ichthyotoxic properties in bioassays with freshwater organisms. The work has been performed studying a very limited number of molluscs that prevented the realization of ecologically relevant experiments. However, the almost exclusive presence of compound 2 in the crude extract of the mantle glands concentrated in the dorsal horn of C. gracillimum strongly supports the defensive role of that dorsal protuberance, which probably acts as a defensive lure attracting potential predators to the part of the animal that contains the distasteful chemicals. 相似文献
96.
Summary. The ontogeny of pyrrolizidine alkaloid (PA) synthesis
and constraints on defence level during the seedling stage were examined
in the annual Senecio vulgaris and the monocarpic perennial
Senecio jacobaea. In both species, PAs were actively
synthesized from the onset of seedling growth so that juvenile stages
did not go through an undefended stage. Roots are known to be the
exclusive sites where PAs are produced. Root biomass was the single most
important biomass parameter explaining variation in total PAs per
seedling. All correlation coefficients between—relative growth
rate and PA concentration were negative, but none was significant.
However, a significant negative—correlation was found between
shoot to root ratio and PA concentration in S. jacobaeaseedlings, suggesting a dilution effect of the PAs. Earlier studies have
shown that the shoot to root ratio is positively correlated with
relative growth—rate of established S. jacobaea plants.
It is therefore suggested that young S. jacobaea plants
with a high shoot to root ratio and hence a high growth capacity
necessarily have lower PA defence levels than plants with a low
shoot to root ratio.
Received 10 July 2002; accepted 16 November 2002. 相似文献
97.
Summary 7-spot ladybirds secrete alkaloid (coccinelline)-rich fluid (reflex blood) from leg joints as a defence mechanism against predators. A technique is described that enables the collection and accurate quantification of reflex blood produced, and the amount of coccinelline therein. Coccinelline was found distributed throughout the body, although concentrated in the reflex blood. Reflex blood was collected from a large set of beetles at several time points. Significant variation was found among beetles in the amount of reflex blood produced (for males and for females corrected for body weight) and the coccinelline concentration of the reflex blood. The results are discussed in relation to automimicry and the maintenance of variation through energy trade-offs. The relationships between tendency to aggregate, ability to reflex bleed and the possession of aposematic coloration are also considered. 相似文献
98.
Stephen B. Malcolm 《Chemoecology》1990,1(1):12-21
Summary Cardenolide sequestration by a hemimetabolous aphid and a holometabolous butterfly from the neotropical milkweed,Asclepias curassavica L., is compared. The oleander aphid,Aphis nerii B. de F., sequestered a similarly narrow range of cardenolide concentrations to the monarch butterfly,Danaus plexippus (L.), from the wide range of concentrations available in leaves of A.curassavica. However, A.nerii sequestered significantly less cardenolide (269 µg/0.1 g) thanD. plexippus (528 µg/0.1 g). The honeydew excreted by A.nerii was comprised of 46% cardenolide. The complete polarity range of 25 cardenolides detected by thin layer chromatography in A.curassavica was represented in the 17 whole aphid cardenolides and the 20 aphid honeydew cardenolides detected. D.plexippus sequestered a narrower polarity range of 11 cardenolides, having eliminated low polarity cardenolide genins and glycosides. It is suggested that these chemical differences may be related to interactions among the broad feeding tactics of sucking or chewing milkweed leaves, life history constraints of holometabolyversus hemimetaboly, the distribution of milkweed food resources in space and time, and the dynamics of natural enemies. 相似文献
99.
Ethan D. Clotfelter 《Behavioral ecology and sociobiology》1997,41(3):193-201
Parental investment by red-winged blackbirds (Agelaius phoeniceus) in response to natural and experi‐mental parasitism by brown-headed cowbirds (Molothrus ater), and in response to freeze-dried, female cowbird mounts presented near redwing nests during the egg-laying period was measured.
Two measures of redwing parental investment were used: nest defense effort toward a model predator, and rate of feeding nestlings.
There were no significant differences in levels of parental investment among unparasitized nests, naturally parasitized nests,
or experimentally parasitized nests. Similarly, parental investment did not differ between redwings that were exposed to the
cowbird mount and those that were not exposed to the mount, or among redwings exposed to the cowbird mount at different distances
from the nest. This suggests that red-winged blackbirds do not recognize when they have been parasitized, and hence do not
associate parasitism with a decrease in their parentage, or that parentage is not an important predictor of parental investment
in this species.
Received: 24 January 1997 / Accepted after revision: 7 June 1997 相似文献
100.
The reproductive trade-off hypothesis predicts that the investment made in current reproduction determines the breeders’ future fitness as a consequence of intra-or inter-generational reproductive costs. Long-lived species are expected to favour their own reproductive value at the expense of their offspring, hence incurring in inter-generational costs, whereas short-lived species are expected to invest in the current breeding attempt even at the expense of their own survival, thus incurring in intra-generational costs. We tested whether intensity of current reproductive effort has intra-or inter-generational costs in a short-lived bird, the blue tit Parus caeruleus, with a brood size manipulation experiment. We expected more intra-generational (parental reproduction and/or survival) than inter-generational (offspring quality and survival) reproductive costs. We found that parental effort, measured as the hourly rate of parental visits to nests, increased gradually with experimental manipulation. Brood size manipulation resulted in a gradual increase in the number of fledglings per nest from reduced to increased treatments. We found an effect of the manipulation on the probability of making a second clutch, with adults rearing enlarged broods being less likely to undertake such a second reproduction during the season compared to those rearing control or decreased broods. We found no evidence of other reproductive costs; neither as adult weight after manipulation, apparent parental local survival, apparent offspring local survival or local recruitment. Although the results seem to support the a priori expectations, alternative explanations are discussed.Communicated by M. Soler 相似文献