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1.
Heikki O. Laurila Helena Nevalainen Veijo Mäkinen 《Applied microbiology and biotechnology》1985,21(3-4):210-212
Summary Protoplast formation in Curvularia inaequalis was achieved using non-commercial and commercial snail gut enzymes or Trichoderma harzianum enzymes. The cells were grown for enzyme treatment on cellophane sheets or in liquid cultures for varying periods of time. The production of T. harzianum enzymes is discussed. The highest protoplast yields were 2.6x107 protoplasts/ml enzyme solution. Protoplasts were shown to have zero to four nuclei. Protoplast regeneration was succesfully carried out in semisolid agar. 相似文献
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3.
Hydrobiologia - Extreme climatic events, such as heat waves, may induce changes in nutrient acquisition by omnivorous ectotherms. Likely modulated by the intensity, frequency and duration of these... 相似文献
4.
Compensating for delayed hatching reduces offspring immune response and increases life‐history costs 下载免费PDF全文
Organisms are exposed to multiple sources of stress in nature. When confronted with a stressful period affecting growth and development, compensatory responses allow the restoration of individual fitness, providing an important buffering mechanism against climatic and other environmental variability. However, tradeoffs between increased growth/development and other physiological traits are predicted to prevent these high growth and development rates from becoming constitutive. Here, we investigated how compensatory responses in growth and development affect immune responses. By using low temperature to stop embryonic development, we exposed moor frog Rana arvalis tadpoles to two levels of time‐constraints: non‐delayed hatching and 12‐day delayed hatching. In a common garden experiment, we recorded larval growth and development, as well as their immune response, measured as the inflammatory reaction after the injection of phytohaemagglutinin (PHA). Tadpoles originating from delayed hatching treatments had a lower immune response to PHA challenge than those from the non‐delayed hatching treatment. In general, tadpoles from the delayed hatching treatment reached metamorphosis faster and at a smaller size than control tadpoles. However, immune‐challenged tadpoles were not able to accelerate their development in response to delayed hatching. Our results indicate that 1) the innate immune response can be reduced in organisms undergoing compensatory developmental responses in growth and development and 2) compensatory capacity can be reduced when organisms are immunologically challenged. These dual findings reveal the complexity of handling multiple stressors and highlight the importance of examining the costs and limits of mounting an immune response in the context of increasing phenological instability ascribed to climate change. 相似文献
5.
Fibronectin expression is determined by the genotype of the transformed parental cells in heterokaryons between normal and transformed fibroblasts 下载免费PDF全文
The expression of fibronectin, a cell surface-associated transformation-sensitive glycoprotein, was studied in hetero- and homokaryons of normal and SV40-transformed human fibroblasts. In immunofluorescence, fibroblast homokaryons had an intense surface-associated and intracelluar fibronectin fluorescence similar to that of normal fibroblasts. Transformed cells and their homokaryons had a minimal surface-associated and a weak intracellular fibronectin fluorescence. In heterokaryons formed between transformed and normal fibroblasts, the expression of fibronectin fell within 24 h to the level of the transformed cell homokaryons. The change was detectable already at 3 h after fusion and was gene-dose dependent. These results show that the transformed genotype determines fibronectin expression in the heterokaryons. 相似文献
6.
Seasonal time constraints can pose strong selection on life histories. Time-constrained animals should prioritise fast development over predation risk to avoid unfavourable growing conditions. However, changes in phenology could alter the balance between anti-predator and developmental needs. We studied variation of anti-predator strategies in common frog (Rana temporaria) tadpoles in four populations from the two extremes of a latitudinal gradient across Sweden. We examined, under common conditions in the laboratory, the anti-predator responses and life histories of tadpoles raised with predatory Aeshna dragonfly larvae in two consecutive years with a difference of 20 days in breeding time in the north, but no difference in breeding time in the nouth. In a year with late breeding, northern tadpoles did not modify their behaviour and morphology in the presence of predators, and metamorphosed faster and smaller than tadpoles born in a year with early breeding. In the year with early breeding, northern tadpoles showed a completely different anti-predator strategy by reducing activity and developing morphological defences in the presence of predators. We discuss the possible mechanisms that could activate these responses (likely a form of environmentally-mediated parental effect). To our knowledge, this is the first study to show that a vertebrate modifies the anti-predator strategy of its offspring in response to natural variation in reproductive phenology, which highlights the need to consider phenology in studies of life-history evolution. 相似文献
7.
Anssi Laurila 《Freshwater Biology》2000,43(2):161-174
- 1 I examined the competitive ability of larval common frogs (Rana temporaria) and common toads (Bufo bufo) in a laboratory experiment by manipulating the number and size of Rana and the number of Bufo.
- 2 Bufo was the most active tadpole type, whereas small Rana was more active than large Rana.
- 3 Especially at high food availability, the growth rate of large Rana at metamorphosis was reduced in the presence of small Rana, whereas that of small Rana was not affected by larger conspecifics.
- 4 Both size classes of Rana were negatively affected by the presence of Bufo. Size at metamorphosis of Bufo was greater when large Rana was present. These results suggest that activity level is important in determining competitive ability.
- 5 To study competition in the field, tadpoles of Bufo were introduced to small rock‐pools that did not support Bufo naturally, but were with or without Rana.
- 6 In the experimental pools, there were no interspecific effects on the growth rate of either species. However, the growth rate of Bufo was lower in the experimental pools than in pools inhabited naturally. Futher, survival of Bufo was low in small pools. Lower food availability or physical factors associated with small pools, rather than interspecific competition, may be the reason why Bufo avoids breeding in small rock‐pools.
8.
In animals with complex life cycles, the environment experienced early during the development may have strong effects on later performance and fitness. We investigated the intraspecific variation in the effects of larval temperature environment on the morphology and locomotory performance of juvenile pool frogs Rana lessonae originating from three closely located populations of the northern fringe metapopulation in central Sweden. Tadpoles were raised individually at two temperatures (20 and 25 °C) until metamorphosis. We measured the morphology of the metamorphs and tested the jumping performance of the froglets after complete tail absorption. We found that early temperature environment affected juvenile morphology, metamorphs from high-temperature environments having relatively longer hindlimbs (tibiofibulas) and longer tails when weight at metamorphosis was accounted for. In absolute terms, froglets from low temperature jumped significantly longer; however, after correcting for size differences the relationship was reversed, individuals raised at high temperature performing better. In both temperatures, relative jumping performance was positively associated with tibiofibula and body length. Populations differed both in metamorphic traits and in jumping capacity, especially at low temperature, suggesting microgeographical variation in temperature sensitivity within the metapopulation. Our results indicate that the temperature environment experienced during the early aquatic stages can influence the morphology and performance of juvenile frogs, and that these effects can be population specific. 相似文献
9.
Species with a wide distribution over latitudinal gradients often exhibit increasing growth and development rates towards
higher latitudes. Ecological theory predicts that these fast-growing genotypes are, in the absence of trade-offs with fast
growth, better competitors than low-latitude conspecifics. While knowledge on key ecological traits along latitudinal clines
is important for understanding how these clines are maintained, the relative competitive ability of high latitude individuals
against low latitude conspecifics has not been tested. Growth and development rates of the common frog Rana temporaria increase along the latitudinal gradient across Scandinavia. Here we investigated larval competition over food resources within
and between two R. temporaria populations originating from southern and northern Sweden in an outdoor common garden experiment. We used a factorial design,
where southern and northern tadpoles were reared either as single populations or as mixes of the two populations at two densities
and predator treatments (absence and non-lethal presence of Aeshna dragonfly larvae). Tadpoles from the high latitude population grew and developed faster and in the beginning of the experiment
they hid less and were more active than tadpoles from the low latitude population. When raised together with high latitude
tadpoles the southern tadpoles had a longer larval period, however, the response of high latitude tadpoles to the competition
by low latitude tadpoles did not differ from their response to intra-population competition. This result was not significantly
affected by density or predator treatments. Our results support the hypothesis that high latitude populations are better competitors
than their low latitude conspecifics, and suggest that in R. temporaria fast growth and development trade off with other fitness components along the latitudinal gradient across Scandinavia. 相似文献
10.
A basic premise of conservation geneticists is that low levels of genetic variation are associated with fitness costs in terms
of reduced survival and fecundity. These fitness costs may frequently vary with environmental factors and should increase
under more stressful conditions. However, there is no consensus on how fitness costs associated with low genetic variation
change under natural conditions in relation to the stressfulness of the environment. On the Swedish west coast, natterjack
toad Bufo calamita populations show a strong population genetic structure and large variation in the amount of within-population genetic variation.
We experimentally examined the survival of natterjack larvae from six populations with different genetic variation in three
thermal environments corresponding to (a) the mean temperature of natural ponds (stable, laboratory), (b) a high temperature
environment occurring in desiccating ponds (stable, laboratory) and (c) an outdoor treatment mimicking the natural, variable
thermal conditions (fluctuating, semi-natural). We found that larvae in the outdoor treatment had poorer survival than larvae
in the stable environments suggesting that the outdoor treatment was more stressful. Overall, populations with higher genetic
variation had higher larval survival. However, a significant interaction between treatments and genetic variation indicated
that fitness costs associated with low genetic variation were less severe in the outdoor treatment. Thus, we found no support
for the hypothesis that fitness costs associated with low genetic variation increase under more stressful conditions. Our
results suggest that natural thermal stress may mask fitness losses associated with low genetic variation in these populations. 相似文献