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111.
LAWRENCE G. MITCHELL 《The Journal of eukaryotic microbiology》1967,14(3):415-424
SYNOPSIS. Myxidium macrocheili n. sp. is described from the gall bladder, bile and pancreatic ducts of Catostomus macrocheilus Girard (largescale sucker) in western Montana. This parasite is markedly host specific; the trophozoite is nonmotile, polysporous, spheroidal, elongated or irregular, often arched and rolled at the edges, and up to 2.5 mm in greatest length; the ecto- and endoplasm are distinct; the sporonts are disporoblastic. The bipolar spore is longitudinally striated, usually ellipsoidal in front view, slightly S-shaped in side view, and averages 11.7 × 6.6 × 6.3 μ; the suture line and ridge are distinct; the polar filaments are coiled 4–6 times. An illustrated synopsis and a key of the 19 species and 10 unnamed forms of Myxidium of North American freshwater vertebrates are presented. At present members of the genus are known to infect fishes, amphibians and a single species of reptile on this continent. 相似文献
112.
Facility for studying the effects of elevated carbon dioxide concentration and increased temperature on crops 总被引:4,自引:3,他引:1
D. W. LAWLOR R. A. C. MITCHELL J. FRANKLIN V. J. MITCHELL S. P. DRISCOLL E. DELGADO 《Plant, cell & environment》1993,16(5):603-608
The requirements for the experimental study of the effects of global climate change conditions on plants are outlined. A semi-controlled plant growth facility is described which allows the study of elevated CO2 and temperature, and their interaction on the growth of plants under radiation and temperature conditions similar to the field. During an experiment on winter wheat (cv. Mercia), which ran from December 1990 through to August 1991, the facility maintained mean daytime CO2 concentrations of 363 and 692 cm3 m?3 for targets of 350 and 700 cm3 m?3 respectively. Temperatures were set to follow outside ambient or outside ambient +4°C, and hourly means were within 0.5°C of the target for 92% of the time for target temperatures greater than 6°C. Total photosynthetically active radiation incident on the crop (solar radiation supplemented by artifieal light with natural photoperiod) was 2% greater than the total measured outside over the same period. 相似文献
113.
DAVID G. HERBERT ANDREW MITCHELL 《Biological journal of the Linnean Society. Linnean Society of London》2009,96(1):203-221
The land snail superfamily Orthalicoidea, although generally assumed to be of Gondwanan origin, is considered by the majority of recent authors to be absent from the African continent. However, two poorly-known African genera, Aillya and Prestonella , have historically been referred to the orthalicoid family Bulimulidae s.l. Anatomical study of Aillya has subsequently shown it to be morphologically distinct from the Bulimulidae and referable to a family of its own, outside the Orthalicoidea, but Prestonella has remained an enigmatic taxon of unknown affinity. Using molecular and morphological evidence, we demonstrate conclusively that Prestonella is indeed a member of the Bulimulidae s.l. We thus confirm that this family is represented in Africa, and that it has a classical disjunct, tri-continental southern distribution. Thus, either the origin of the family must at the least predate the separation of Africa and South America in the Mid Cretaceous (under a vicariance scenario) or there must have been subsequent dispersal between the isolated Gondwanan fragments. In view of the limited dispersal ability of terrestrial snails, we consider the former more likely. Anatomically, Prestonella exhibits many character states thought to be plesiomorphic, suggesting a relationship with the subfamily Bulimulinae. Bayesian analysis of nuclear DNA sequence data places it as sister group (posterior probability = 1.0) to an Australasian clade comprising Bothriembryon and Placostylus . However, taxon sampling within the Orthalicoidea is currently inadequate to permit meaningful resolution of subfamilial affinity using molecular data. Similarly, although those orthalicoid taxa for which molecular data are available comprise a well-supported clade, the relationships of this clade to other stylommatophoran clades remain unresolved. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 203–221. 相似文献
114.
GREG W. MITCHELL NATHANIEL T. WHEELWRIGHT CHRISTOPHER G. GUGLIELMO D. RYAN NORRIS 《Ibis》2012,154(2):325-337
Costs of reproduction represent a common life‐history trade‐off. Critical to understanding these costs in migratory species is the ability to track individuals across successive stages of the annual cycle. We assessed the effects of total number of offspring fledged and date of breeding completion on pre‐migratory body condition, the schedule of moult and annual survival in a migratory songbird, the Savannah Sparrow Passerculus sandwichensis. Between 2008 and 2010, moult was delayed for individuals that finished breeding later in the breeding period and resulted in reduced lean tissue mass during the pre‐migratory period, suggesting an indirect trade‐off between the timing of breeding completion and condition just prior to migration. Lean tissue mass decreased as the number of offspring fledged increased in 2009, a particularly cool and wet year, illustrating a direct trade‐off between reproductive effort and condition just prior to migration in years when weather is poor. However, using a 17‐year dataset from the same population, we found that parents that fledged young late in the breeding period had the highest survival and that number of offspring fledged did not affect survival, suggesting that individuals do not experience long‐term trade‐offs between reproduction and survival. Taken together, our results suggest that adult Savannah Sparrows pay short‐term costs of reproduction, but that longer‐term costs are mitigated by individual quality, perhaps through individual variation in resource acquisition. 相似文献
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119.
BILL D. SPARKLIN MICHAEL S. MITCHELL LAURA B. HANSON D. BUCK JOLLEY STEPHEN S. DITCHKOFF 《The Journal of wildlife management》2009,73(4):497-502
ABSTRACT We examined home range behavior of female feral pigs (Sus scrofa) in a heavily hunted population on Fort Benning Military Reservation in west-central Georgia, USA. We used Global Positioning System location data from 24 individuals representing 18 sounders (i.e., F social groups) combined with mark-recapture and camera-trap data to evaluate evidence of territorial behavior at the individual and sounder levels. Through a manipulative experiment, we examined evidence for an inverse relationship between population density and home range size that would be expected for territorial animals. Pigs from the same sounder had extensive home range overlap and did not have exclusive core areas. Sounders had nearly exclusive home ranges and had completely exclusive core areas, suggesting that female feral pigs on Fort Benning were territorial at the sounder level but not at the individual level. Lethal removal maintained stable densities of pigs in our treatment area, whereas density increased in our control area; territory size in the 2 areas was weakly and inversely related to density of pigs. Territorial behavior in feral pigs could influence population density by limiting access to reproductive space. Removal strategies that 1) match distribution of removal efforts to distribution of territories, 2) remove entire sounders instead of individuals, and 3) focus efforts where high-quality food resources strongly influence territorial behaviors may be best for long-term control of feral pigs. 相似文献
120.
Preliminary observations on the daytime activity patterns of lesser kudu in Tsavo National Park, Kenya* 总被引:1,自引:0,他引:1
A. W. MITCHELL 《African Journal of Ecology》1977,15(3):199-206
Free-ranging lesser kudu were observed during the day in Tsavo (East) National Park for periods of up to 12 h and records of activity patterns were obtained. Data grouped into the percentage of animals engaged in feeding, resting, and other activities in each time class show a changing pattern of behaviour through the day. The presence of a biphasic resting rhythm is demonstrated, the initiation and duration of which are variable. Feeding generally predominated in the early morning and late afternoon. Rumination took place during resting periods which were also used for the avoidance of excessive heat stress. Possible factors controlling the phasing of the behaviour seen are discussed. 相似文献