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451.
452.
Comparative morphology of the dermal palate in squamate reptiles, with comments on phylogenetic implications 总被引:1,自引:0,他引:1
OLIVIER RIEPPEL JACQUES GAUTHIER JESSICA MAISANO 《Zoological Journal of the Linnean Society》2008,152(1):131-152
The differentiation of the dermal palate and of the septomaxilla in extant squamate reptiles is reviewed in terms of Lakjer's distinctions of a palaeochoanate, incomplete neochoanate, and neochoanate condition. The differentiation of the bones surrounding the mushroom body, Jacobson's organ, and the internal naris (choana) supports a number of clades including Squamata, Scleroglossa, and Autarchoglossa, with Serpentes nested within Autarchoglossa. Dermal palate morphology and the differentiation of the septomaxilla in squamates reflect the evolution of the chemosensory system in general, and the vomeronasal system in particular, and strongly contradict a recent hypothesis of squamate phylogeny based on molecular data. © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society , 2008, 152 , 131–152. 相似文献
453.
A vibrating probe was used to detect and measure electricalcurrents at the surface of excised leaves and isolated leafepidermis from Commelina commnunis. Currents of up to 4.0 µAcm2 moving out from the leaf surface were observed whenthe stomata were open. When the stomata were almost closed nocurrent was detected and when they were fully closed a smallinwardly directed current was observed. There appeared to bea linear relationship between current and stomatal aperture.The current was stimulated by fusicoccin and eliminated by increasingthe external pH suggesting that it was brought about by a flowof H+ from the leaf surface. Key words: Electrical currents, leaves, stomata, vibrating probe 相似文献
454.
ANGELA J. BEAUMONT TREVOR J. EDWARDS JOHN MANNING OLIVIER MAURIN MARLINE RAUTENBACH MOLEBOHENG C. MOTSI MICHAEL F. FAY MARK W. CHASE MICHELLE VAN DER BANK 《Botanical journal of the Linnean Society. Linnean Society of London》2009,160(4):402-417
We address the generic limits of Gnidia (Thymelaeaceae) through a phylogenetic analysis of nuclear ribosomal DNA internal transcribed spacer (ITS) and plastid rbcL, trnL intron and trnL‐F intergenic spacer regions. Maximum parsimony and Bayesian inference were used to produce trees and assess internal support. The most significant conclusion drawn from the molecular analysis is that Gnidia is polyphyletic as currently circumscribed, comprising at least four distinct lineages that are each related to other genera within Thymelaeoideae. Gnidia pinifolia and G. racemosa are members of a clade within which Struthiola is embedded; a second group of species allies with Drapetes as sister to Passerina; and a third lineage corresponds to the previously recognized genus Lasiosiphon. The remaining species of Gnidia included in this study are allied with the Australian genus Pimelea. The taxonomic implications of these findings are discussed in relation to the principle of monophyly. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 160 , 402–417. 相似文献
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456.
Xylem in early tracheophytes 总被引:4,自引:0,他引:4
D. EDWARDS 《Plant, cell & environment》2003,26(1):57-72
457.
Abstract: Tracks and trackways of the vertebrate ichnotaxon Ichniotherium sphaerodactylum and a trace of the invertebrate ichnotaxon Striatichnium bromackerense are described for the first time in association outside of Europe. The tracks are identified as I. sphaerodactylum based on their characteristic rounded digit ends, the ovoid sole‐pad of the pedal imprint and the increase in digit lengths from digits I–IV, and the invertebrate trace is identifiable as S. bromackerense based on the band‐like systems of distally bifurcated striae. The tracks of I. sphaerodactylum are the largest known to date and represent rare evidence of large‐bodied terrestrial vertebrates in the Kildare Capes Formation of Prince Edward Island, Canada. Morphometric differences between ichnospecies of Ichniotherium and other ichnospecies previously collected from Prince Edward Island are examined in a multivariate analysis, and results suggest that the distance between the manus and pes of the same imprint pair, the width of pace and the length of certain digits is useful for species identification. The association between I. sphaerodactylum and S. bromackerense was previously known only from the Bromacker quarry, Tambach Formation, Germany, which is interpreted as a seasonally dry, semi‐arid upland environment. The co‐occurrence of these traces suggests that the Eldon locality of Prince Edward Island is similar in depositional environment to the Bromacker quarry in Germany, and allows for comparison of these two localities for the first time. As diadectids are thought to be the trackmakers of Ichniotherium, the Eldon locality of the Kildare Capes Formation may, with further work, be considered as another example of the rare, herbivore‐dominated palaeoenvironment, which is generally uncharacteristic of the Early Permian of North America. 相似文献
458.
The effects of changes in the inorganic nitrogen source of themedium on the growth and development of Marsilea in asepticculture are described. A change in nitrate concentration to0·2 or 5 x that of the normal medium had initially noeffect on growth or heteroblastic development, but in the 0·2nitrogen medium there was finally a reversion to juvenile stagesfollowed by early cessation of growth. Growth and heteroblastic development were stimulated by thesubstitution of the nitrate of the medium by ammonium saltsor urea. Nitrite was little inferior to nitrate as a nitrogensource, but hydroxylamine was toxic even at low concentrations.Addition of sodium chloride led to improved growth and developmentin nitrate media, an effect referred to beneficial effects ofthe chloride ion. Symptoms of toxicity and eventual death of the cultures whichoccurred after prolonged growth on ammonium media were due toan acid drift of the media rather than to a specific effectof the ammonium ion. 相似文献
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460.