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71.
We investigated physiological constraints on calling behaviour in the túgara frog, Physalaemus pustulosus. First, we examined the hypothesis that energetic factors limit calling. Time spent in chorus activity is the best predictor of male mating success (Ryan, 1985). Manipulation of food availability demonstrated that males given supplemental food were more likely to call than males without supplemental food. Males without supplemental food were less likely to call even though their lipid reserves were only slightly less than males given the supplemental food, suggesting that part of the increased energy obtained from the supplemental food may have been channelled into calling to attract females. Secondly, we examined the role of steroid hormones in switching between reproductive and non-reproductive behaviours. Calling males had higher levels of plasma testosterone than silent males. Experimental elevation of corticosterone decreased testosterone levels and the likelihood of calling, thus linking both of these steroid hormones to calling behaviour. Males who responded to supplemental food by increasing calling had higher levels of testosterone than those without supplemental food, but there was no difference in plasma corticosterone levels. Overall, the results suggest that energetic factors affect calling behaviour and that one potential mechanism for this affect is through plasma testosterone levels. Corticosterone can decrease calling behaviour, however, corticosterone does not appear to mediate the effect of energetic factors on calling behaviour. These data are consistent with the hypothesis that energetic factors ultimately constrain sexual selection for calling behaviour. 相似文献
72.
73.
In an attempt to prepared tetrakis(tert-butoxy)uranium(IV) a trinuclear oxo-alkoxide of uranium(IV) was obtained instead. The compound has the formula U3O[(CH3)3CO]10 and it crystallizes in the hexagonal space group P63mc with a = b = 18.256(4) Å, c = 10.013(2) Å, Z = 2. The trinuclear unit is strikingly reminiscent of that in Mo3O(OCH2CMe3)10. In contrast to the molybdenum compound where there is metal-metal bonding, the U?U distance of 3.574(1) Å indicates a non-bonded interaction. 相似文献
74.
Free-ranging rhesus monkeys on Cayo Santiago (Puerto Rico) give five acoustically distinct scream vocalizations during agonistic encounters. These calls are thought to be an important mechanism in the recruitment of support from allies against opponents. Alliance formation during agonistic encounters is known to vary with the dominance rank and matrilineal relatedness of opponents, as well as with the severity of aggression. In contrast to previous interpretations of screams as graded signals reflecting the level of arousal of the caller, we found these calls to be much more discrete, with each of the five acoustic types significantly associated with a particular class of opponent and level of physical aggression. We performed a series of field experiments in which tape-recorded screams of immature rhesus monkeys were played to their mothers in the absence of any other information. The results suggest that the information necessary for differential responses is conveyed by the scream vocalizations themselves. We conclude that screams are representational signals that refer to external objects and events and function in the system of agonistic alliance formation. 相似文献
75.
Peter Marler 《Developmental neurobiology》1997,33(5):501-516
Research on avian song learning has traditionally been based on an instructional model, as exemplified by the sensorimotor model of song development. Several large-scale, species-wide field studies of learned birdsongs have revealed that variation is narrowly restricted to certain aspects of song structure. Other aspects are sufficiently stereotyped and so widely shared by species' members that they qualify as species-specific universals. The limitations on natural song variation are difficult to reconcile with a fully open, instructive model of song learning. An alternative model based on memorization by selection postulates a system of innate neural templates that facilitate the recognition and rapid memorization of conspecific song patterns. Behavioral evidence compatible with this model includes learning preferences, rapid conspecific song learning, and widespread ocurrence of species-specific song universals that are recognized innately but fail to develop in songs of social isolates. A third model combines instruction, in the memorization phase, with selection during song production. An overproduced repertoire of plastic songs previously memorized by instruction is winnowed by selection imposed during social interactions at the time of adult song crystallization. Selection during production is well established as a factor in the song development of several species, in the form of action-based learning. The possible role of selective processes in song memorization merits further neurobiological investigation. © 1997 John Wiley & Sons, Inc. J Neurobiol 33: 501–516, 1997 相似文献
76.
Gades NM Ohash A Mills LD Rowley MA Predmore KS Marler RJ Couch FJ 《Comparative medicine》2008,58(3):271-275
Mice in a colony used for pancreatic cancer research and maintained in a barrier animal facility presented with vulvar masses. A census and examination of all colony animals was conducted on 17 February 2006; line, gender, and mass location were recorded; a slide caliper was used to measure the width, length, and height of each mass; and the volume of each mass was calculated. Progeny female mice from crossbreeding of the B6.FVB-Tg(Ipf1-cre)1Tuv and B6;129-Kras2tm4Tyj (KRAS(G12D/+)) strains presented with external vulvar and periauricular papillomas. The papillomas were present in 41.2% of all female crossbred mice and ranged in size from 8 to 36 mm3. Age of mice and tumor size were not correlated. Compared with the B6.FVB-Tg(Ipf1-cre)1Tuv line, the crossbred female mice were more likely to have a vulvar mass, with an odds ratio of 29.3, 95% confidence interval (1.5, 563.9) and a positive predictive value of 42.9%. Diagnostic evaluation, including electron microscopy, light microscopy, serology, and bacteriology, did not reveal a viral or other infectious etiology. Therefore, we speculate that interaction between the genetic background of the mice and the introduced Kras oncogene may be responsible for these papillomas. 相似文献
77.
Angélica Cibrián-Jaramillo Thomas E. Marler Rob DeSalle Eric D. Brenner 《Conservation Genetics》2008,9(4):1051-1054
We developed a set of 12 EST-microsatellite markers (EST-STRs) from Cycas rumphii Miq. and tested them on an ex situ collection of the endangered Cycas micronesica K.D. Hill. The number of alleles per locus in both species ranged from 1 to 15. Observed and expected heterozygosities ranged
from 0.000 to 0.842, and 0.000 to 0.883, respectively. All primers amplified in four additional Cycas species. These markers are the first genome-enabled tools for cycad population level studies, and are now available to inform
conservation efforts and disentangle the biogeographic history of the genus. 相似文献
78.
Thomas E. Marler 《The Botanical review》2004,70(1):63-71
The photosynthetic characteristics ofCycas micronesica K.D. Hill were studied from August 1998 until February 1999 using chlorophyll fluorescence and gas-exchange techniques to
determine the responses to long-term shade of 35% ambient light transmission, followed by the transfer of shade-grown leaves
into full-sun conditions. The shade-grown leaves exhibited increased photosynthetic light use efficiency and effective quantum
efficiency of photosystem II (PS II) and decreased photosynthetic light saturation point and dark respiration when compared
with leaves grown in full sun. Shade was removed from shade-grownC. micronesica leaves during midday on December 14, 1998, when effective quantum efficiency of shaded leaves was 45% greater than that of
sun leaves. Following one hour in full sun, effective quantum efficiency of the shade-grown leaves declined to below that
of the sun-grown leaves. After receiving full sunlight for the rest of the photoperiod, maximum quantum efficiency of PS II
photochemistry for shade-grown leaves was below that of sun-grown leaves throughout the night. The damage caused by excessive
light to shade-grown leaves progressed for the first three days after shade removal. On day 3, effective quantum efficiency
during midday was 30%, net photosynthesis was 47%, apparent quantum yield was 65%, and light compensation point was 136% of
that for sun-grown leaves. After day 3, the relationship between full-sun leaves and the previously shaded leaves for these
response variables was relatively stable. Two months following removal of shade, the previously shaded leaves continued to
exhibit damage from high light. These results have application to transplanting cycad plants from a shaded nursery to a field
site or, after tropical cyclones, where protective forest canopy cover has been destroyed and cycad plants in the forest subcanopy
are abruptly exposed to full-sun conditions. 相似文献
79.
80.
Marler TE 《American journal of botany》2010,97(5):841-845
Specialist insects share obligate mutualisms with some contemporary cycad species whereby the insect's pollination services are rewarded with a nursery in which the insect's larvae consume the postdispersal male cone. I prevented visits of the pollinator moth Anatrachyntis sp. to male Cycas micronesica (Cycadaceae) cones to show that consumption of the cone tissue by the mutualist hastened initiation of the plant's subsequent reproductive event. This is the first documented case where removal of a postdispersal cycad pollination organ speeds up subsequent reproductive events, and the current paradigm that the offering of cone tissue as a nursery is a sacrifice by the plant in return for the pollination services is therefore inaccurate. In C. micronesica, the herbivory stage of pollination mutualism confers a cryptic benefit of cone tissue disposal, which translates into an increase in ultimate lifetime reproductive effort. The plant population relies on the pollinator for moving gametes, as well as for increasing the number of male coning events. The dual benefits afforded to the plant by associating with this pollinator shows that mutualism can operate simultaneously on very different traits. 相似文献