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1.
Phylogenetic position of a remarkable new fideliine bee from northern Chile (Hymenoptera: Megachilidae) 下载免费PDF全文
Fideliine bees are an archaic group with a disjunct distribution mostly restricted to deserts of South America and South Africa. This group was previously thought to be more diverse in Africa than in South America, where only one genus (Neofidelia) comprising five species is known. Here we describe a species belonging to a second South American genus: Xenofidelia colorada Packer gen. et sp.n. , from northern Chile. The species is illustrated and its phylogenetic position within Megachilidae is assessed using morphological, molecular and combined data. The 214 character morphological matrix includes 55 new characters with an additional 16 hitherto unexplored for megachilid phylogeny. The molecular dataset is based upon seven nuclear gene sequences, totalling 6439 bp, many of which are published for the first time for particular megachilid taxa. In all analyses, Xenofidelia was found as sister to Neofidelia (endemic to Chile and Peru). It differs from that genus most notably in its short mouthparts, absence of a glossal rod, unmodified female metabasitarsus and an elongate and horizontal dorsal surface of the metapostnotum. Morphological and combined data support a monophyletic Fideliinae (excluding Pararhophites), while molecular data alone failed to recover fideliine monophyly. Dating analyses suggest that Xenofidelia and Neofidelia diverged 34.3–40.6 Ma, indicating that New World fideliines were probably present in arid habitats of South America during the Eocene. This divergence time predates both the main orogenic events that resulted in the formation of the Andean mountains and the origin of hyperarid conditions in the Atacama Desert; it also corresponds to a period prior to the origin of the summer rainfall area in the far north of Chile where the new genus is found. These results support the view that arid habitats have been present continuously in South America since the Eocene. This published work has been registered in ZooBank, http://zoobank.org/urn:lsid:zoobank.org:pub:EA69BB4A‐6F59‐4A15‐AB44‐2A8949E3CF8F . 相似文献
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Dependence of the Post-Illumination Burst of CO2 on Temperature, Light, CO2 , and O2 Concentration in Wheat (Triticum aestivum) 总被引:3,自引:0,他引:3
The effect of environmental factors on the post-illumination burst of CO2 (PIB) and O2 inhibition of apparent photosynthesis (APS) in wheat (Triticum aestivum L.) was studied in an open gas exchange system utilizing the mathematics of non-steady-state systems. Two components of inhibition by O2 are suggested: one is caused by photorespiration as measured from the maximum rate of the PIB, and the second is direct inhibition as taken as APS2%O2— (APSx%O2+ PIBx%O2) where X is the oxygen concentration. A primary PIB which occurred from 16–28 s after the darkening of the foliage was attributed to photorespiration. No primary PIB was observed at 2% O2. At a CO2 concentration of 100 μ/1 in the atmosphere (about 2.5 μM based on leaf intercellular concentration) and at 30°C and 145 nE/cm2 nE/cm2·s, APS decreased curve-linearly with increasing O2 and reached an O2 compensation point of 560 μM (48% by volume), above which there was a net loss of CO2 in the light. The PIB increased with increasing O2 and became saturated at about 500 μM O2 but decreased above 900 μM O2. Direct inhibition of photosynthesis by O2 increased with increasing O2 concentration. Decreasing CO2 concentration had an effect on the magnitude of the PIB similar to that of increasing O2. At 30°C and 21% O2, the PIB increased with decreasing CO2 down to the CO2 compensation point (I) of 1.4 μM (47 μM/l). Below Γ, both PIB and CO2 evolution into the air in the light (at 21% O2) increased and then decreased at CO2 below 0.8 μM. The ratio of the PIB to APS2% o O2 increased linearly with increasing O2/CO2 ratio where O2 was held constant at 21% and CO2 was varied from 1.4 to 8.5 μM, while direct inhibition of photosynthesis expressed as a proportion of APS2%O2 remained constant over this range. At low CO2 concentration photorespiration as estimated by the PIB is the major part of O2 photosynthesis, while at atmospheric CO2 levels, direct inhibition is the major component. The PIB and APS at 2% and 21% O2 increased hyperbolically with increasing irradiance and all became light-saturated at about 65 nE/cm2 s. The percentage total O2 inhibition of photosynthesis remained constant with increasing irradiance as did the relative contribution of direct O2 inhibition or photorespiration (PIB) to total O2 inhibition. The PIB and APS at 21% O2 had similar temperature optima of 30°C when experimental conditions were adjusted to provide a constant internal O2/CO2 solubility ratio at varying temperatures. However, with a constant external CO2 concentration, the temperature optimum for the PIB shifted upward to 35°C while that for APS at 21% O2 remained at 30°C, which may be due to an increased O2/CO2 concentration in the leaf with increasing temperature. 相似文献
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Growth and maintenance respiration in leaves of northern red oak seedlings and mature trees after 3 years of ozone exposure 总被引:1,自引:0,他引:1
A two-component model of growth and maintenance respiration is used to study the response of northern red oak (Quercus rubra L.) seedlings and 32-year-old trees to sub-ambient (10 μmol h; cumulative dose based on 7 h daily mean), ambient (43 μmol h), and twice-ambient (85 μmolh) ozone. The relative growth rates (RGR) of leaves sampled from seedlings and trees were similar across treatments, as were specific leaf respiration rates (SRR). Growth coefficients estimated from the SRR versus RGR relationship averaged 25-3 mol CO2 kg?1 leaf dry mass produced for seedlings and 21-5 mol kg?1 for trees. Maintenance coefficients ranged from 0-89 to 1-07 mol CO2 kg?1 leaf dry mass d?1 for seedlings and from 0-64 to 0-84 mol kg-1 d?1 for trees. Neither coefficient was affected by ozone. Leaves sampled throughout the growing season also showed little response of respiration to ozone. This occurred despite a 30% reduction in net photosynthesis for trees grown at twice-ambient ozone. These results suggest that growth and maintenance respiration in young northern red oak leaves are not affected by ozone and that in older leaves injury can occur without a parallel increase in so-called ‘maintenance’ respiration. 相似文献
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A diverse assemblage of early land plants from the Lower Devonian of the Welsh Borderland 总被引:1,自引:0,他引:1
U. FANNING D. EDWARDS F.L.S. J. B. RICHARDSON 《Botanical journal of the Linnean Society. Linnean Society of London》1992,109(2):161-188
FANNING, U., EDWARDS, D. & RICHARDSON, J. B., 1992. A diverse assemblage of early land plants from the Lower Devonian of the Welsh Borderland. Nine rhyniophytoid taxa are described from an early Gedinnian locality ( middle micromatus-newportensis spore Biozone) near Ludlow, England. They include Cooksonia pertoni, C. hemisphaerica, C. cambrensis, Tortilicaulis transwalliensis and three new taxa, Salopella marcensis sp. nov., Uskiella reticulata sp. nov. and Tarrantia salopensis gen. et sp. nov. Isolated sporangia of reniform shape, and those subtended by short lengths of axis, contain spores of Apiculiretusispora type and may belong to C. caledonica or Renalia . Morphologically distinctive forking, terminal sporangia lacking identifiable spores are not placed in a new taxon, because evidence based on in situ spores from elsewhere suggests they may belong to Salopella . Structures previously interpreted as clusters of sporangia of Yarravia- type are shown to be ± globular sporangia longitudinally split into valves. Sterile axes are dominated by smooth forms; although rare examples possess small enations. Tracheids have not been seen in axes of fertile specimens nor in sterile coalified compressions. A single pyrite permineralization contains tracheids of zosterophyll type. The assemblage demonstrates diversity among rhyniophytoids in the early Devonian and the existence of low vegetation 'alongside' the much larger zosterophyll dominated type. 相似文献
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