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991.
Petra Hirschberger 《Oecologia》1998,116(1-2):136-142
Competitive interactions in northern temperate dung beetles are poorly understood. This investigation therefore comprises
a series of field and experimental work on a dung beetle species common in northern Europe, Aphodius ater, with special focus on intraspecific competitive interactions. The between-pat distribution of adult A. ater in relation to the age of sheep dung pats was studied in the field. The distribution of both sexes was contagious in the
fresh pats but became more regular with increasing pat age. The successional occurrence of males and females did not differ,
but immature females tended to occur in fresh pats while mature females were mainly found in older pats. With increasing age
of pats, the egg load of females also increased. Egg-laying behaviour of the beetles was studied in laboratory experiments.
The mean number of eggs laid per female per dung pat decreased with increasing beetle density. Thus, density-dependent processes
seem to regulate resource utilisation with regard to breeding behaviour, resulting in equal exploitation of the available
pats. Survival and weight of recently hatched beetles decreased with increasing initial density of eggs. Hence, in A. ater, competition between larvae for food within pats does occur.
Received: 4 February 1998 / Accepted: 20 April 1998 相似文献
992.
Experimental manipulation of the number of altricial offspring is supposed to modify parental expenditure in birds. In addition
to the observed increase in parental feeding rate, it is also possible that the choice of prey or the size of load may change
with the changing demand for food. Sexual differences in the provisioning response are also expected, on the basis of earlier
studies. We examined the effect of brood size manipulation on choice of prey brought to nestlings and load size in the pied
flycatcher. The composition and size of loads differed between years, possibly depending on varying availability of different
prey types. Males responded to brood size enlargement by gathering heavier loads, whereas females showed no response. The
alteration of load size in males was not explained by a larger number of prey items or mean prey size, but was a combination
of these components. It is likely that males also increased their work rate in response to increased food demand at the nest.
The absence of response in females might be because they are unable to increase work rate any further, or because food delivery
rate in females can not be optimized by changing load properties.
Received: 18 December 1997 / Accepted: 1 March 1998 相似文献
993.
Interspecific variation in the escape responses of aphids: effect on risk of predation from foliar-foraging and ground-foraging predators 总被引:1,自引:0,他引:1
A series of laboratory experiments was conducted to determine the effect of interspecific differences on prey defensive behavior
on the susceptibility of two aphid species (Acyrthosiphon pisum and A. kondoi) to a ground-foraging predator, Harpalus pennsylvanicus, and a foliar-foraging predator, Coccinella septempunctata. These organisms are representative of a biologically and economically important predator/prey system in alfalfa. The primary
defensive behavior of both aphid species toward C. septempunctata was to “drop” from the plant. Both aphid species were significantly more likely to drop from the plant in the presence of
C. septempunctata. However, when C. septempunctata was present, a significantly lower proportion of A. kondoi individuals dropped (0.42 ± 0.07) compared to A. pisum (0.73 ± 0.08). As a result of their lower propensity to drop from the plant A. kondoi individuals are significantly more likely to be consumed by C. septempunctata. Conversely, the higher propensity of A. pisum individuals to drop increased their susceptibility to ground-foraging predators. When A. pisum was the prey species, ground-foraging predators made a significant contribution to overall aphid suppression and there was
a significant synergistic interaction between ground and foliar-foraging predators. When A. kondoi was the prey there was no interaction between the predator species. As either a cause or consequence of its higher propensity
to drop, A. pisum seems to be more adapted for survival and dispersal off the plant. In comparison to A. kondoi individuals, A. pisum individuals relocate plants more quickly (63 ± 41 s vs. 164 ± 39 s), disperse farther (18 ± 1.7 cm vs. 13 ± 0.66 cm), and
survive longer (37 ± 2.0 h vs. 25 ± 2.0) off the plant. This study demonstrates the importance of prey defensive behavior
in determining the susceptibility of a prey species to a multiple-predator complex.
Received: 24 February 1997 / Accepted:17 December 1997 相似文献
994.
Pollinator behavior influences plant reproduction in many ways. A traditional measure of pollination, the number of visits
received, may be a poor predictor of plant reproductive success, particularly when there are trade-offs between visit quantity
and components of visit quality. For example, the duration of pollinator visits may be negatively correlated with the number
of visits received by a flower. We tested for a trade-off between the number of bumblebee visits and the duration of those
visits in an experimental population of snapdragons (Antirrhinummajus: Scrophulariaceae). The duration of a bumblebee visit to a flower increased significantly with the time interval since the
flower had last been visited. Over the lifetime of a flower the correlation between the total number and average duration
of visits received by a flower was weakly negative. However, at the whole-plant level the correlation was positive: plants
whose flowers received more visits also received visits of longer duration. Factors affecting the relationship between quantity
and duration of pollinator visits to flowers also were investigated. Two factors weakened the negative dependence of average
visit duration on number of visits received by individual snapdragon flowers: (1) the correlation between the total number
of visits to a flower and the average interval between visits was only −0.53, as visits to individual flowers were not very
evenly spaced over time, and (2) newly opened flowers received fewer and shorter visits than older flowers. Comparing whole
plants, nectar production per flower varied dramatically across individuals, a probable explanation for the positive correlation
between visit number and average duration per flower observed at the plant level. The potential for a trade-off between these
two components of pollinator service exists when visit duration depends on reward quantity; whether the trade-off is realized
will depend on variation in nectar production and on whether pollinators forage systematically.
Received: 3 October 1997 / Accepted: 16 June 1998 相似文献
995.
The transient behavior of a class of nonlinear differential systems representing stage-structured populations is studied.
The qualitative dynamics are described in terms of succession of extrema for the state variables, or for the integrated difference
between two trajectories. The rules giving the possibilities of extrema are derived, they characterize the classical stage-structured
models. These rules can be compared with experiments to validate the structure of the model. An explanation for the disagreement
of this transition scheme with some experiments could be an unexpected interaction with another variable. A new model taking
the interaction into account thus engenders new transition rules, which are to be compared with experiments. These results
are illustrated with experiments on copepods, showing how the qualitative experimental features can help the construction
and the validation of the models.
Received: 13 May 1996 / Revised version: 20 March 1998 相似文献
996.
S. Blumberg A. J. Susswein 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1998,182(2):175-181
In Aplysia fasciata, pheromones released by conspecifics with access to mates increase the quantity of food eaten. This effect is blocked when
the chemosensory rhinophores are ablated, indicating that the rhinophores sense pheromones. The modulation of feeding by pheromones
can be monitored by an increase in the amplitude of swallowing movements in the presence of conspecifics with access to mates.
Atrial gland homogenates and four bag cell peptides (egg-laying hormone, and α, β, and γ bag cell peptides) amplify the swallow
amplitude in a manner similar to that caused by conspecifics with access to mates, suggesting that peptides from the bag cell/atrial
gland family that are released from the atrial gland into the surrounding water may be pheromones regulating feeding and reproductive
behaviors.
Accepted: 14 June 1997 相似文献
997.
R. Huber A. Delago 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1998,182(5):573-583
The biogenic amine serotonin is thought to play an important role in aggression in many species, including man. This paper
summarizes experimental approaches which attempt to link this neuromodulator with fighting in a crayfish model for which the
complex agonistic behavior is well characterized. Based on a quantitative analysis of fighting we demonstrate that the infusion
of small amounts of serotonin into freely-moving crayfish alters fighting behavior by specifically interfering with the timing
of a treated animal's decision to withdraw from an encounter. In the presence of added serotonin, fights last considerably
longer compared to controls, but no changes were detected in the rules of escalation, the likelihood of initiating an interaction,
or its eventual outcome. Attempts to dissect the underlying neuronal mechanisms pharmacologically hinged on fluoxetine as
a potent inhibitor of serotonin re-uptake. Although no behavioral changes were associated with acute infusion of fluoxetine
alone, in combination with serotonin it effectively prevented the previously observed fight-enhancing effects. Our data strongly
support the significance of functional amine re-uptake mechanisms for behavior and continued use of this invertebrate model
should prove a promising route to unravel further the complex bases of aggression.
Accepted: 11 October 1997 相似文献
998.
999.
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