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61.
1. Adaptive divergence in sympatry is supposed to be inhibited by the homogenizing role of gene flow. However, studies continue to uncover examples of sympatric divergence. In this study, two divergent phenotypes in a complex of four syntopic gall midge morphotypes [nominally Asteromyia carbonifera Osten Saken, Diptera: Cecidomyiidae: Alycaulini] are characterised. The first is a behavioural phenotype governing within‐host tissue preference and the second is a trait governing accessory‐gland carotenoid quality and quantity. 2. One gall morphotype (crescents) lay most of their eggs on mature tissue whereas the other three gall morphotypes oviposit only on young emerging leaves. Ecological maintenance of this divergent trait appears to be driven by enemy‐reduced space. That is, nearly 40% of the crescent morphotype galls that develop high on the plant are attacked by the egg parasitoid Platygaster solidaginis Ashmed, whereas those low on the plant are relatively protected. 3. All morphotypes contain carotenoids in their accessory glands, but the quality and quantity of these pigments differs significantly between the morphotypes and is positively associated with the probability of parasitism by P. solidaginis. 4. Larval salivary glands also contain carotenoids and the plant hormone abscisic acid, which in plants is synthesized from carotenoid precursors and is involved in regulating plant defences. This hormone may facilitate gall development and influence gall morphology. 5. Ecological fitness trade‐offs between carotenoids, parasitoid attack, and plant resistance may be fostering adaptive divergence in ovipositional phenotypes and sympatric speciation in this complex of gall midge morphotypes.  相似文献   
62.
Experiments on the effect of Cd, Cu, Ni, Pb and Zn, suppliedas single salt solutions between 10 µM and 0·1M, on the moss Rhytidiadelphus squarrosus showed little alterationto respiratory rates but reduced photosynthetic rates, and somemembrane damage as assessed by K leakage. Two distinct morphologicalforms of the moss showed different responses to supplied heavymetal. Storage of material, after 30 mins exposure to heavymetals, resulted in a further decrease in the photosyntheticrate. Expressing the photosynthetic decline relative to thetotal heavy metal recovered from the moss showed a similar pattern.Transfer of metal from extracellular exchange sites into theprotoplast was also demonstrated with storage after exposure.An approximately linear relationship was demonstrated betweenphotosynthetic decline and intracellular heavy-metal concentration,irrespective of the duration of exposure or morphological natureof the material used. Photosynthetic decline on storage is concludedto be a response to additional metal stress rather than a progressivedeterioration of the physiological process. Cadmium, copper, lead, nickel, zinc, photosynthesis, respiration, membrane damage, intracellular metals, Rhytidiadelphus squarrosus (Hedw.) Warnst  相似文献   
63.
Patelloida nigrosulcata on intertidal platforms in the Perthmetropolitan area live on the backs of shells of living abalone,Haliotis roei. Over 95% of abalone 30 mm have one or more limpets,and there is a close relationship between abalone and limpetdensity. Sexes are usually separate in P. nigrosulcata, butabout 4% of the population in hermaphroditic. The animals spawntwice annually in winter (May–June) and spring (October–November).The reproductive periodicity of P. nigrosulata is compared toother published data on acmaeids. *Present address: Australian Institute of Marine Science, PMBNo. 3, Townsville, Queensland 4810, Australia (Received 23 March 1987;  相似文献   
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We developed eight microsatellite markers for Cryptocarya mackinnoniana to study the spatial genetic structure and ecological correlates of parentage in secondary rainforests in Australia's Wet Tropics. The microsatellite loci were screened in 99 trees, and 623 seedlings < 0.24 m tall, at a site extending from primary rainforest into adjacent 50‐year‐old secondary rainforest. The eight loci were polymorphic, exhibiting between three and 11 alleles, and gene diversity (HE) from 0.25 to 0.84. For the trees, no departures from Hardy–Weinberg equilibrium were detected, except at locus Cm03, which had an estimated null allele frequency of 0.0903. No locus combinations exhibited linkage disequilibrium.  相似文献   
66.
The subfamily Chrysomyinae includes blowflies of considerable ecological and applied importance. Previous extensive morphological investigations have affirmed chrysomyine monophyly, but did not support the monophyly of traditional chrysomyine tribes. Conversely, molecular systematic analyses suggested a para‐ or polyphyletic Chrysomyinae. Conflicting hypotheses have been proposed about the tribe‐level classification, and about the relationships of the obligate bird parasites Protocalliphora Hough and Trypocalliphora Peus. To understand chrysomyine evolution better, we reconstructed phylogenies of the Chrysomyinae based on 2285 bp of combined data from mitochondrial cytochrome oxidase c subunit 1 (COI) and nuclear carbamoylphosphate synthetase (CPS) genes. Maximum parsimony (MP), maximum likelihood (ML) and Bayesian analysis (BA) strongly supported the monophyly of Chrysomyinae and the paraphyly of the tribe Chrysomyini. BA and ML yielded a monophyletic tribe Phormiini, but this was unresolved by MP. A sister‐group relationship between Trypocalliphora and Protocalliphora indicates that obligate bird parasitism evolved once within the Calliphoridae. For the first time all Neotropical genera (Cochliomyia Townsend, Compsomyiops Townsend, Paralucilia Brauer and Bergenstamm, Hemilucilia Brauer and Chloroprocta Wulp) were found to comprise a single lineage, and Chrysomya Robineau‐Desvoidy, traditionally a member of Chrysomyini, was found to be closer to the Phormiini. Similarly, Hemilucilia + Chloroprocta was a monophyletic group. Every genus for which we examined more than one species was monophyletic.  相似文献   
67.
DNA Ligase and Exonuclease Activities in Virions of Rous Sarcoma Virus   总被引:17,自引:0,他引:17  
Virions of Schmidt-Ruppin avian sarcoma virus have both polynucleotide ligase activity and DNA exonuclease activity. These enzymes complete the machinery necessary to transfer information from RNA to double stranded DNA integrated in the host DNA.  相似文献   
68.
By collating the evidence provided by written records and herbaria, and with a knowledge of the present-day habits of individual species, it is sometimes possible to reconstruct the vegetation pattern and, thereby, changes in the natural environment of a site or region during the last few centuries. This paper takes the form of a case study of the records left by the Marchioness of Huntly (1821–1893) and the information they provide, for example, on changes in the Huntingdonshire fenland.  相似文献   
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