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Biocontrol of Rhizoctonia crown and root rot of sugar beet by binucleate Rhizoctonia spp. and Laetisaria arvalis 总被引:1,自引:0,他引:1
LEONARD J. HERR 《The Annals of applied biology》1988,113(1):107-118
Two isolates of Laetisaria arvalis and 10 of binucleate Rhizoctonia spp. (BNR) from the Ohio sugar beet production area, were tested in the greenhouse and field for biocontrol of Rhizoctonia crown and root rot of sugar beet, caused by Rhizoctonia solani anastomosis group 2, type 2. L. arvalis was ineffective in standard greenhouse tests, and the single isolate used in the field was generally ineffective. Seven of 10 BNR isolates effectively controlled crown and root rot in greenhouse tests. Delayed application of biocontrol agents to plants 5 – 10 wk old was generally more effective than applications made at planting. A BNR isolate significantly reduced % plant loss and disease ratings and increased yield in a 1985 field test as compared with the control infested with R. solani alone. Two BNR isolates were effective in a 1986 field test and increased yields c. 22% in comparison to a L. arvalis treatment, which did not differ from the R. solani-infested control. The Ohio binucleate Rhizoctonia isolates appear to have considerable potential as applied biocontrol agents and may play a role in the natural ecology of R. solani in the sugar beet production area of Ohio. 相似文献
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LEONARD B. RADINSKY 《Biological journal of the Linnean Society. Linnean Society of London》1984,22(1):31-41
Skull length is the measurement most commonly used as a standard against which other aspects of cranial morphology are compared to derive an index of relative size or proportions. However, skull length is composed of two different functional components, facial skull and cerebral skull, which vary independently and have different scaling relationships with body size. An analysis of carnivore skull shape with measurements standardized against basicranium length produced very different results than an analysis using skull length as the standard. For example, expressions of relative size of cranial measurements were reduced by 13% in mustelids and increased by 20% in canids, reflecting removal of jaw length (short in mustelids and long in canids) from the comparative standard (basicranial axis length). Cranial measurements scale with higher allometric exponents against basicranial axis length than against skull length. 相似文献
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LEONARD A. SMOCK 《Freshwater Biology》1983,13(4):313-321
SUMMARY.
- 1 The influence of organism size on whole-body metal concentrations of eight metals was examined in aquatic insects in field and laboratory studies. Information on the partitioning of metals between adsorbed, absorbed and gut content material was also obtained.
- 2 For Co, Cr, Fe, Sb and Sc, an exponential decrease in concentration with increasing organism size was observed, indicating surface adsorption as an important mode of metal accumulation.
- 3 No, or only a slight, concentration-size relationship was found for K, Mn and Na. This is expected for metals with high absorption efficiencies and a low capacity to be adsorbed.
- 4 Clearing of the gut of the mayfly Stenonema modestum (Ephemeroptera: Heptageniidae) did not significantly after the concentration size relationship for any of the metals studied.
- 5 Studies of Cr uptake with Stenacron interpunctatum (Ephemeroptera: Heptageniidae) indicate that the concentration-size relationship is not affected by variability in the concentration of available Cr.
- 6 About 52% of the whole-body burden of Cr in S. interpunctatum was associated with gut material while at least 33% was adsorbed to the organism's exoskeleton and at most 15% was internally absorbed.
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SYNOPSIS. As a homozygous recessive, gene e in the Mexican axolotlprevents optic vesicles from forming, thus producing an eyelessanimal. Previous experimental evidence has indicated that thegene acts by affecting the ability of anterior medullary plateectoderm in the eye field to respond to inductive mesodermalsignals. Other possible mechanisms of gene action are described.The hypothalamus is also affected and "eyeless" animals aresterile. The absence of eyes results in increased levels ofcirculating MSH and thus the animal is also highly pigmented.Eyes may be grafted into the heads of "eyeless" axolotls. Theseeyes become functional and lead to normal pigmentation. Whenpresent as a homozygous recessive, gene r acts to allow thepenetration of heterozygous e (E/e r/r). This results in abnormaleye development. 相似文献
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Phyletic Relationships of Living Sharks and Rays 总被引:3,自引:1,他引:2
A set of hypotheses are developed for the origin of living sharksand rays and the interrelationships of their major groups, usingsome methods of cladistic analysis to relate groups with sharedderived characters. Comparative studies on living sharks andrays combined with new data on fossil sharks suggests that theliving groups ultimately stem from a common ancestral groupof "neoselachian" sharks with many modern characters. Reinterpretationsof "amphistyly" in modern sharks is presented on new data. 相似文献
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LEONARD B. RADINSKY 《Biological journal of the Linnean Society. Linnean Society of London》1981,15(4):369-388
Fifteen variables, selected primarily to reflect functionally significant aspects of cranial morphology, were measured on one skull each of 62 species of modern carnivores, including viverrids, canids, mustelids and felids. To allow comparisons between species of different sizes without the potentially confounding effects of allometric shape changes, the measurements were transformed to dimensionless variables, based on the residuals from allometric equations. Fourteen out of 15 of the transformed variables distinguish one or more of the four family groups and the rotated first two axes of a principal components analysis distinguish all four families from each other. The following functional hypotheses are proposed: mustelids and felids have the most powerful bites and canids the weakest among the four family groups studied; mustelids and, to a lesser degree, felids have more powerful neck musculature than do canids and viverrids; and visual abilities are best developed among felids and least developed among mustelids. The first two functional hypotheses suggest possible differences in killing behaviour, which are supported by a preliminary survey of the literature on such behaviour. Allometric analysis of the 15 cranial measures shows that the neurocranial components scale with negative allometry, while most of the other measures scale approximately isometrically. 相似文献
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TIM J. CLOUGH JANET E. BERTRAM ROBERT R. SHERLOCK ROBERT L. LEONARD BARBARA L. NOWICKI† 《Global Change Biology》2006,12(2):352-363
There is considerable uncertainty in the estimates of indirect N2O emissions as defined by the Intergovernmental Panel on Climate Change's (IPCC) methodology. Direct measurements of N2O yields and fluxes in aquatic river environments are sparse and more data are required to determine the role that rivers play in the global N2O budget. The objectives of this research were to measure the N2O fluxes from a spring‐fed river, relate these fluxes to the dissolved N2O concentrations and NO3‐N loading of the river, and to try to define the indirect emission factor (EF5‐r) for the river. Gas bubble ebullition was observed at the river source with bubbles containing 7.9 μL N2O L?1. River NO3‐N and dissolved N2O concentrations ranged from 2.5 to 5.3 mg L?1 and 0.4 to 1.9 μg N2O‐N L?1, respectively, with N2O saturation reaching 404%. Floating headspace chambers were used to sample N2O fluxes. N2O‐N fluxes were significantly related to dissolved N2O‐N concentrations (r2=0.31) but not to NO3‐N concentrations. The N2O‐N fluxes ranged from 38 to 501 μg m?2 h?1, averaging 171 μg m?2 h?1 (±SD 85) overall. The measured N2O‐N fluxes equated to an EF5‐r of only 6.6% of that calculated using the IPCC methodology, and this itself was considered to be an overestimate because of the degassing of antecedent dissolved N2O present in the groundwater that fed the river. 相似文献