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391.
Abstract Surveying species that are present in low numbers is difficult because often the survey fails to locate any individuals. One strategy to improve the sample design is to survey the site repeatedly. With repeat surveys the abundance of the target species, and hence likelihood of detection, may change between visits. We present a model for deciding on the maximum surveillance interval between repeat surveys so that there is a high probability of detecting the species. We use as an example surveys for new weed infestations and model the chance of detecting the weed before control costs reach a threshold. The maximum surveillance interval depends on the rate of weed growth, the ability to detect the weed, and the cost of controlling the weed. Typically weed growth rates are high. Fast growing plants need to be detected early before they spread, but often weeds are difficult to detect when young and still comparatively cheap to control. Results from the model to determine maximum surveillance intervals are given for five broad habitat types and seven weed types. Surveillance intervals ranged from 1 to 10 years. Longer intervals are appropriate when searching for weeds with slower growth rates, that are easier to detect, and those that can be controlled cheaply. 相似文献
392.
SIMON DUCATEZ DELPHINE LEGRAND AUDREY CHAPUT‐BARDY VIRGINIE M. STEVENS HELENE FRÉVILLE MICHEL BAGUETTE 《Ecological Entomology》2012,37(5):377-385
1. One of the main drivers of the genesis and maintenance of biodiversity is mobility, i.e. the net result of the interaction between physiological performances (movement capacity) and behavioural decisions (movement decisions). Although several previous studies have found personality traits related to mobility, it is not yet clear whether mobility involves a real syndrome, i.e. whether individuals showing good movement capacity are also more likely to decide to move, and whether these inter‐individual differences are consistent across time. 2. The aim of the present study was therefore to disentangle the mechanisms underlying the maintenance of inter‐individual variation in mobility by measuring three traits related to mobility under experimental conditions in a butterfly species, and to test the existence of correlations between these traits. These measures implied movement capacity and movement decision. 3. It was shown that mobility‐related traits were (i) consistent across time, (ii) inter‐correlated, and (iii) dependent upon sex and morphology. 4. These results therefore suggest the existence of a mobility syndrome in a butterfly. Such findings highlight the necessity to accurately integrate inter‐individual variation (behavioural syndrome) in our comprehension of the evolution of movement strategies. 相似文献
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THE SYMPTOMS OF CALCIUM DEFICIENCY IN PLANTS 总被引:4,自引:1,他引:3
E. W. SIMON 《The New phytologist》1978,80(1):1-15
398.
A survey of a stratified eutrophic lake was undertaken to determine the degree of variability in direct counts of bacteria, electron transport system activity, ATP concentration, chlorophyll a concentration and chemiluminescence, in the water column and the sediment. Heterogeneity in the horizontal and vertical dimension was studied in detail and the scale of variability was compared with within-sample and between-sample errors, and with seasonal fluctuations. Variability was greater in the sediment samples, and the coefficient of variation of samples taken at a single site was often as large as that between sites in a transect across the lake. Although this was not an exhaustive survey, the values provided should allow rough estimates to be made of the number of samples required to achieve a given level of precision in future investigations. 相似文献
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The Development of Mitochondria in Arum Spadix 总被引:1,自引:0,他引:1
Electron micrographs of Arum spadix cells prepared at four stagesof development all showed abundant sections of mitochondriawith tubular ingrowths (microvilli). At the earliest stage (whenthe spadix cells were still dividing) there was an average of9 sections of microvilli per mitochondrion. In later stagesof development, when the cells were growing by elongation, thenumber of microvilli rose to 22. It was reported earlier that the succinoxidase activity of themitochondria of Arum spadix increased as the spadix developed,and it is now shown that the rise in enzyme activity parallelsthe increase in length of microvilli. 相似文献