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81.
In a pot experiment, the growth and the nutrient status of in vitro propagated coffee (Coffea arabica L.) microcuttings were investigated for 5 months following vesicular-arbuscular mycorrhizal (VAM) inoculation with either
Acaulospora melleae or Glomus clarum at four soil P availabilities. Control plants remained P-deficient even at the highest soil P availability while mycorrhizal
plants were P-sufficient at all soil P availabilities. Growth of control plants was only improved at the highest soil P availability.
In P-deficient soil, neither of the two VAM species improved plant growth. Plant growth increased by 50% following inoculation
with either A. melleae or G. clarum when P availability went from deficient to low. No further plant growth improvement was induced by either VAM species at
intermediate and high soil P levels. Nevertheless, growth of plants inoculated with G. clarum was still significantly greater than that of non-mycorrhizal plants at the highest soil P availability. Root colonization
by G. clarum increased with increasing soil P availability while root colonization by A. mellea decreased with soil P level increasing above low P availability. Soil P availability also affected Zn nutrition through its
influence on VAM symbiosis. With increasing soil P availability, foliar Zn status increased with G. clarum or decreased with A. mellea in parallel to root colonization by VAM. This study demonstrates the beneficial effects of VAM inoculation on in vitro propagated
Arabica coffee microcuttings, as shown previously for seedlings. This study also demonstrates differences in tolerance to
soil P availability between VAM species, most likely resulting from their differing abilities to enhance coffee foliar P status.
Accepted: 14 November 1996 相似文献
82.
83.
Soils from valley oak (Quercus lobata Nee) riparian areas of the Cosumnes River Nature Conservancy Preserve near Sacramento, California were added to growth medium
of valley oak seedlings grown in a greenhouse or in agricultural fields at Cosumnes which probably once supported valley oak
trees and are now replanted with native riparian vegetation or allowed to revegetate naturally. Agricultural field soil from
the Cosumnes River Preserve was presumed to be low or lacking in ectomycorrhizal inoculum. The study was designed to (1) determine
whether valley oak stand soil transfer could cause mycorrhizal infection on valley oak seedlings in an agricultural field
and in a greenhouse, (2) describe ectomycorrhizal morphological types formed on valley oak seedlings, and (3) determine whether
seedling growth is enhanced more by transfer of natural valley oak stand soil than agricultural field soil. In the field study,
transfer of forest soil increased average ectomycorrhizal diversity (2.4 types) more than transfer of agricultural field soil
(1.2 types). Valley oak seedlings were responsive to ectomycorrhizal infection in the field study. With increase in mycorrhizal
infection there was an increase in shoot growth at the expense of root growth. In the greenhouse study, both percent mycorrhizal
infection and mycorrhizal diversity were increased more by transfer of oak forest and woodland soils than agricultural field
soil. Eight morphotypes occurred on seedlings in forest and woodland soils but only three morphotypes in agricultural soil.
This result strongly suggests that the agricultural field also harbors ectomycorrhizal propagules but forest and woodland
soils support a more abundant and diverse ectomycorrhizal flora.
Accepted: 17 August 1997 相似文献
84.
Multidimensional heteronuclear NMR studies have been applied to the
resonance assignment and conformational analysis of 13C-enriched
Neu5Acalpha2-3Galbeta1-4Glc. It is demonstrated that three-dimensional
ROESY-HSQC experiments provide through-space distance restraints which
cannot be observed with conventional homonuclear 1H techniques due to
resonance overlap. In particular, connectivities demonstrating the
existence of the "anti" conformation about the Galbeta1-4Glc glycosidic
linkage are unambiguously observed. It is shown that 13C isotopic
enrichment of the trisaccharide at a level >95% enables straightforward
measurement of trans-glycosidic 1H-13C and 13C-13C coupling constants and a
Karplus-type relation is derived for the latter. In total 15 conformational
restraints were obtained for the trisaccharide in aqueous solution, all of
which were in excellent agreement with theoretical parameters computed from
a 5 ns molecular dynamics simulation of the glycan.
相似文献
85.
Morphometry of the human pulmonary vasculature 总被引:2,自引:0,他引:2
Huang, W., R. T. Yen, M. McLaurine, and G. Bledsoe.Morphometry of the human pulmonary vasculature.J. Appl. Physiol. 81(5):2123-2133, 1996.The morphometric data on the branching patternand vascular geometry of the human pulmonary arterial and venous treesare presented. Arterial and venous casts were prepared by the siliconeelastomer casting method. Three recent innovations are used to describethe vascular geometry: the diameter-defined Strahler ordering model isused to assign branching orders, the connectivity matrix is used todescribe the connection of blood vessels from one order to another, anda distinction between vessel segments and vessel elements is used toexpress the series-parallel feature of the pulmonary vessels. A totalof 15 orders of arteries were found between the main pulmonary arteryand the capillaries in the left lung and a total of 15 orders of veinsbetween the capillaries and the left atrium in the right lung. Theelemental and segmental data are presented. The morphometric data arethen used to compute the total cross-sectional areas, blood volumes, and fractal dimensions in the pulmonary arterial and venous trees. 相似文献
86.
Pilot-Scale Selenium Bioremediation of San Joaquin Drainage Water with Thauera selenatis 总被引:1,自引:0,他引:1
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A. W. Cantafio K. D. Hagen G. E. Lewis T. L. Bledsoe K. M. Nunan J. M. Macy 《Applied microbiology》1996,62(9):3298-3303
This report describes a simple method for the bioremediation of selenium from agricultural drainage water. A medium-packed pilot-scale biological reactor system, inoculated with the selenate-respiring bacterium Thauera selenatis, was constructed at the Panoche Water District, San Joaquin Valley, Calif. The reactor was used to treat drainage water (7.6 liters/min) containing both selenium and nitrate. Acetate (5 mM) was the carbon source-electron donor reactor feed. Selenium oxyanion concentrations (selenate plus selenite) in the drainage water were reduced by 98%, to an average of 12 (plusmn) 9 (mu)g/liter. Frequently (47% of the sampling days), reactor effluent concentrations of less than 5 (mu)g/liter were achieved. Denitrification was also observed in this system; nitrate and nitrite concentrations in the drainage water were reduced to 0.1 and 0.01 mM, respectively (98% reduction). Analysis of the reactor effluent showed that 91 to 96% of the total selenium recovered was elemental selenium; 97.9% of this elemental selenium could be removed with Nalmet 8072, a new, commercially available precipitant-coagulant. Widespread use of this system (in the Grasslands Water District) could reduce the amount of selenium deposited in the San Joaquin River from 7,000 to 140 lb (ca. 3,000 to 60 kg)/year. 相似文献
87.
Cotyledons from Pisum sativum L. cv. Alaska seeds were excised 12, 36, 108, 132, and 156 hours after imbibition in aerated distilled water. They were then incubated under aseptic conditions for 6 hours in solutions containing either uridine-2-14C or orotic acid-6-14C. Uridine was more extensively degraded to 14CO2 at all germination stages than was orotate, and these rates remained essentially constant at each stage. Incorporation of each compound into RNA increased about 2-fold from the 12th to the 156th hour, although the total RNA present decreased slightly over this interval. Paper chromatography of soluble labeled metabolites produced from orotate showed that the capacity to metabolize this pyrimidine increased markedly as germination progressed. Radioactivity in uridine-5′-P, uridine diphosphate-hexoses, and uridine diphosphate increased most, while smaller or less consistent increases in uridine, uracil, uridine triphosphate, and an unidentified UDPX compound were also observed. The data suggest that orotate metabolism was initially limited by orotidine-5′-phosphate pyrophosphorylase or by 5-phosphoribosyl-1-pyrophosphate. Incorporation of uridine into RNA appeared to be limited at the earliest germination periods by conversion of uridine-5′-P to uridine diphosphate. Thus, during the 1st week of germination the orotic acid pathway and a salvage pathway converting uridine into RNA become activated. 相似文献
88.
Comparative actions of glutamate and related substances on the lateral line of xenopus laevis 总被引:1,自引:0,他引:1
S C Bledsoe D M Chihal R P Bobbin D N Morgan 《Comp. Biochem. Physiol. C, Comp. Pharmacol. Toxicol.》1983,75(2):199-206
The effects of compounds structurally related to L-glutamate were compared on spontaneous activity of afferent nerve fibres in Xenopus laevis lateral-line. The potencies (EPMR) of several compounds relative to L-glutamate (EPMR = 1) were: L-aspartate (EPMR = 1), D-aspartate (EPMR = 1), D-glutamate (EPMR = 1.98), quisqualate (EPMR = 0.0015), kainate (EPMR = 0.0045), dihydrokainate (EPMR = 0), ibotenate (EPMR = 1.5), L-homocysteate (EPMR = 0.17), 2,4,5-trihydroxyphenylalanine (6-OH-DOPA, EPMR = 0.23), and D-homocysteate (EPMR = 0.73), N-methyl-D,L-aspartate (EPMR = 5), and N-methyl-D-aspartate (NMDA, EPMR = 1). Several compounds, including gamma-aminobutyrate (GABA), suppressed spontaneous activity without eliciting excitatory responses. The results reveal receptors that are present at this vertebrate peripheral synapse. 相似文献
89.
90.