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141.
Correlation of Infectivity and Concanavalin A Agglutinability of Algae Exsymbiotic from Paramecium bursaria 总被引:1,自引:0,他引:1
DALE S. WEIS 《The Journal of eukaryotic microbiology》1978,25(3):366-370
SYNOPSIS. Eighteen strains of algae, including 17 exsymbiotic from Paramecium bursaria , were tested for infectivity for P. bursaria , syngen 2 aposymbiotes, and Concanavalin A (Con A) agglutinability. All 6 infective algal strains were relatively resistant to agglutination by Con A, suggesting that algal surface characteristics are correlated with infectivity. Among the noninfective strains, high and low agglutinability were about equally represented, indicating that the Con A titer alone is not a sufficient indicator of infectivity. It is suggested that noninfective algal strains are the progeny of mutations occurring within the endozoic population and fortuitously selected by the external culture medium. 相似文献
142.
DALE S. WEIS 《The Journal of eukaryotic microbiology》1979,26(1):117-119
Synopsis.
Eighteen strains of algae, including 17 formerly symbiotic with Paramecium bursaria , were tested for capacity to release sugar. Detectable amounts of sugar were found in the supernatant fluids from 10 strains, including 6 strains infective for aposymbiotic P. bursaria syngen 2. The other 4 sugar-releasing strains were noninfective and released ˜26–46 g sugar/mg dry cell weight compared to ˜90–175 g sugar/mg dry cell weight for infective strains. This relationship of infectivity with capacity to release sugar supplements data that indicate a relationship of infectivity with resistance to Con A agglutination. The correlation is completed if we assume that resistance to Con A agglutination and capacity for sugar release must both be present in an algal strain for infectivity. The data thus strongly suggest that these 2 characteristics must be present for infectivity by any algal strains for aposymbiotic P. bursaria syngen 2. 相似文献
Eighteen strains of algae, including 17 formerly symbiotic with Paramecium bursaria , were tested for capacity to release sugar. Detectable amounts of sugar were found in the supernatant fluids from 10 strains, including 6 strains infective for aposymbiotic P. bursaria syngen 2. The other 4 sugar-releasing strains were noninfective and released ˜26–46 g sugar/mg dry cell weight compared to ˜90–175 g sugar/mg dry cell weight for infective strains. This relationship of infectivity with capacity to release sugar supplements data that indicate a relationship of infectivity with resistance to Con A agglutination. The correlation is completed if we assume that resistance to Con A agglutination and capacity for sugar release must both be present in an algal strain for infectivity. The data thus strongly suggest that these 2 characteristics must be present for infectivity by any algal strains for aposymbiotic P. bursaria syngen 2. 相似文献
143.
PHILIP J. DALE 《The Annals of applied biology》1979,93(3):285-288
Shoot tips from 0.2 to 4.8 mm long and tiller buds 0.2 to 5.1 mm long were cultured from cocksfoot ( Dactylis glomerata ) plants known to be infected with combinations of cocksfoot streak, cocksfoot mild mosaic and cocksfoot mottle viruses. Regenerated plants were tested for the presence of viruses by electron microscopy, serology and the expression of symptoms. All viruses were eliminated by culturing shoot tips and tiller buds less than 1.2 mm long but the maximum explant size capable of regenerating healthy plants depended upon the infecting virus. Viruses were not detected in shoot tip and tiller bud samples of similar size to the explants that gave healthy plants. The method is of value in eliminating viruses from desirable stocks of D. glomerata that must be vegetatively propagated. 相似文献
144.
A virus disease of cacao, discovered in Trinidad towards the end of 1943, is apparently confined to the north-western corner of the is land and does not occur in the main cacaogrowing areas of eastern, central and southern Trinidad; nor has it been found in Venezuela, Tobago or the Windward Islands of Grenada, St Vincent, St Lucia and Dominica. The symptoms resemble those of West African swollen shoot disease, consisting of vein-clearing or mosaic of the leaves and red-mottle of the leaves and pods. No swellings are formed, but recent observations indicate that the disease may cause both dieback and reduction in yield. There are two strains closely resembling each other. The spread of the disease under field conditions has been demonstrated, and although the rate of spread has varied somewhat, a mean increase of 41 % over the original number of infected trees has been found over a 10-month period. As with swollen shoot disease, existing diseased areas have increased in size and new outbreaks at short distances have occurred. Both strains were readily transmitted by budding, the incubation period varying from 34 to 136 days, with a mean around 90 days, but no insect vectors have been found. There is at present little reason to believe that any varieties of cacao are immune to the disease or are even symptomless carriers. The question of eradicating this virus, while its distribution remains limited, should be seriously considered. 相似文献
145.
Behavioural responses of a south-east Australian floodplain fish community to gradual hypoxia 总被引:1,自引:0,他引:1
1. Hypoxic conditions occur frequently during hot, dry summers in the small lentic waterbodies (billabongs) that occur on the floodplains of the Murray‐Darling River system of Australia. Behavioural responses to progressive hypoxia were examined for the native and introduced floodplain fish of the Ovens River, an unregulated tributary of the Murray River in south‐east Australia. 2. Given the high frequency of hypoxic episodes in billabongs on the Ovens River floodplain, it was hypothesised that all species would exhibit behaviours that would confer a degree of hypoxia‐tolerance. Specifically, it was hypothesised that as hypoxia progressed, gill ventilation rates (GVRs) would increase and aquatic surface respiration (ASR) would become increasingly frequent. Fish were subjected to rapid, progressive hypoxia from normoxia to anoxia in open tanks. 3. All tested species exhibited behaviours consistent with their use of potentially hypoxic habitats. As hypoxia progressed, GVRs increased and all species, with the exception of oriental weatherloach, began to switch increasingly to ASR with 90% of individuals using ASR at various oxygen concentrations below 1.0 mg O2 L−1. Australian smelt, redfin perch and flat‐headed galaxias were the first three species to rise to ASR, with 10% of individuals using ASR by 2.55, 2.29 and 2.21 mg O2 L−1 respectively. Goldfish and common carp were the last two species to rise to ASR, with 10% of individuals using ASR by 0.84 and 0.75 mg O2 L−1 respectively. In contrast to other species, oriental weatherloach largely ceased gill ventilation and used air‐gulping as their primary means of respiration during severe hypoxia and anoxia. 4. Australian smelt, redfin perch and flat‐headed galaxias were unable to maintain ASR under severe hypoxia, and began exhibiting erratic movements, termed terminal avoidance behaviour, and loss of equilibrium. All other species continued to use ASR through severe hypoxia and into anoxia. Following a rise to ASR, GVRs either remained steady or decreased slightly indicating partial or significant relief from hypoxic stress for these hypoxia‐tolerant species. 5. Behavioural responses to progressive hypoxia amongst the fish species of the Ovens River floodplain indicate a generally high level of tolerance to periodic hypoxia. However, species‐specific variation in hypoxia‐tolerance may have implications for community structure of billabong fish communities following hypoxic events. 相似文献
146.
DOUGLAS C. HEARD LANA M. CIARNIELLO DALE R. SEIP 《The Journal of wildlife management》2008,72(3):596-602
Abstract: Animal locations collected by Global Positioning System (GPS) collars will represent a biased sample of the sites an animal used if some position fixes fail and if those missed locations do not occur randomly. Probability of a GPS receiver obtaining a position fix is known to decline as canopy cover increases, but the impact of forest canopy cover was insufficient to account for the low fix rates we observed for GPS collars on grizzly bears (Ursus arctos). We tested the hypothesis that GPS fix rates were related to the interaction between animal activity (active vs. resting) and canopy cover by evaluating the following predictions: 1) grizzly bear activity should follow a circadian pattern similar to the circadian fix-rate pattern, 2) grizzly bear use of canopy cover should follow a circadian pattern similar to the circadian fix rates, 3) grizzly bear activity should be related to canopy cover (i.e., bears should rest in areas with relatively high canopy covers and feed and move in relatively open areas), and 4) collar orientation and canopy cover should interact to affect the fix rates of test collars. The GPS fix rates traced a bimodal circadian pattern that was directly related to the circadian pattern of grizzly bear activity. Fix rates declined when bears were more likely to be using denser cover, and fix rates of test collars demonstrated that collar orientation interacted with canopy cover, such that fix rates declined much more with increasing canopy cover when the collar was on its side than when the collar was upright. We concluded that inferences made about grizzly bear microhabitat use, based on GPS locations, will underrepresent high canopy cover sites, especially when grizzly bears are resting there. (JOURNAL OF WILDLIFE MANAGEMENT 72(3):596–602; 2008) 相似文献
147.
148.
149.
The influence of the root holoparasitic angiosperm Orobanche minor Sm. on the biomass, photosynthesis, carbohydrate and nitrogen content of Trifolium repens L. was determined for plants grown at two CO2 concentrations (350 and 550 μmol mol−1 ). Infected plants accumulated less biomass than their uninfected counterparts, although early in the association there was a transient stimulation of growth. Infection also influenced biomass allocation both between tissues (infected plants had lower root:shoot ratios) and within tissues:infected roots were considerably thicker before the point of parasite attachment and thinner below. Higher concentrations of starch were also found in roots above the point of attachment, particularly for plants grown in elevated CO2 . Elevated CO2 stimulated the growth of T. repens only during the early stages of development. There was a significant interaction between infection and CO2 on growth, with infected plants showing a greater response, such that elevated CO2 partly alleviated the effects of the parasite on host growth. Elevated CO2 did not affect total O. minor biomass per host, the number of individual parasites supported by each host, or their time of attachment to the host root system. Photosynthesis was stimulated by elevated CO2 but was unaffected by O. minor . There was no evidence of down-regulation of photosynthesis in T. repens grown at elevated CO2 in either infected or uninfected plants. The data are discussed with regard to the influence of elevated CO2 on other parasitic angiosperm-host associations and factors which control plant responses to elevated CO2 . 相似文献
150.
C. DALE BEERS 《The Journal of eukaryotic microbiology》1954,1(1):86-92
Of 165 sea urchins ( Strongylocentrotus dröbachiensis ) examined in the Mt. Desert Island region, 41 harbored the intestinal ciliate Plagiopyla minuta in considerable numbers. Division in this ciliate is clean; i.e. it is not accompanied by the visible elimination of macronuclear material. Long periods (probably several weeks) of vegetative life appear to alternate with brief periods of intense divisional activity in P. minuta. Twenty-five of these same urchins also contained in their digestive tracts a species of Euplotes which was identified as E. balteatus. This hypotrich was also found commonly in the region as a free-living organism. Dividing specimens were found regularly in the urchin, and such specimens showed the usual macronuclear reorganization which occurs in Euplotes and its near relatives. The evidence indicates that E. balteatus is a facultative commensal, which is perhaps now in the process of acquiring the endozoic habit. 相似文献