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61.
TOMÁ HERBEN FRANTIEK KRAHULEC VRA HADINCOVÁ MARCELA KOVÁOVÁ HANA SKÁLOVÁ 《Plant Species Biology》1994,9(3):183-189
Abstract Festuca rubra forms tillers in two different ways: extravaginally and intravaginally. Demography of these two tiller types was observed in seventeen selected tussocks of Festuca rubra s.s. over four growing seasons. Extravaginal tillers were bigger at birth and on the average produced twice as many daughter tillers per tiller. In general, the natality and mortality of extravaginal tillers were less regular than that of intravaginal tillers. Overall tillering rate per tiller was correlated with the density of the surrounding vegetation; mortality, natality and tiller life span were not. High density of the surrounding vegetation did not result in increased formation of extravaginal tillers. The proportion of the extravaginal tillers was not correlated with the density of the F. rubra tussocks. There is no evidence for foraging by extravaginal tillers, but they do act as founders of small clusters of tillers. 相似文献
62.
Distribution and conservation of mobile elements in the genus Drosophila 总被引:13,自引:1,他引:12
Essentially nothing is known of the origin, mode of transmission, and
evolution of mobile elements within the genus Drosophila. To better
understand the evolutionary history of these mobile elements, we examined
the distribution and conservation of homologues to the P, I, gypsy, copia,
and F elements in 34 Drosophila species from three subgenera. Probes
specific for each element were prepared from D. melanogaster and hybridized
to genomic DNA. Filters were washed under conditions of increasing
stringency to estimate the similarity between D. melanogaster sequences and
their homologues in other species. The I element homologues show the most
limited distribution of all elements tested, being restricted to the
melanogaster species group. The P elements are found in many members of the
subgenus Sophophora but, with the notable exception of D. nasuta, are not
found in the other two subgenera. Copia-, gypsy-, and F-element homologues
are widespread in the genus, but their similarity to the D. melanogaster
probe differs markedly between species. The distribution of copia and P
elements and the conservation of the gypsy and P elements is inconsistent
with a model that postulates a single ancient origin for each type of
element followed by mating-dependent transmission. The data can be
explained by horizontal transmission of mobile elements between
reproductively isolated species.
相似文献
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TOSHIHIRO TOKIWA DAVID MODRÝ AKIRA ITO KATEŘINA POMAJBÍKOVÁ KLÁRA J. PETRŽELKOVÁ SOICHI IMAI 《The Journal of eukaryotic microbiology》2010,57(2):115-120
ABSTRACT. Troglocorys cava n. g., n. sp. is described from the feces of wild eastern chimpanzee, Pan troglodytes schweinfurthii, in Uganda. This new species has a spherical body with a frontal lobe, a long vestibulum, a cytoproct located at the posterior dorsal side of the body, an ovoid macronucleus, a contractile vacuole near the cytoproct, and a large concavity on the left surface of the body. Buccal ciliature is non‐retractable and consists of three ciliary zones: an adoral zone surrounding the vestibular opening, a dorso‐adoral zone extending transversely at the basis of the frontal lobe, and a vestibular zone longitudinally extending in a gently spiral curve to line the surface of the vestibulum. Two non‐retractable somatic ciliary zones comprise arches over the body surface: a short dorsal ciliary arch extending transversely at the basis of the frontal lobe and a wide C‐shaped left ciliary arch in the left concavity. Because of the presence of three ciliary zones in the non‐retractable buccal ciliature, the present genus might be a member of the family Blepharocorythidae, but the large left concavity and the C‐shaped left ciliary arch are unique, such structures have never been described from other blepharocorythids. 相似文献
65.
The worldwide increase in the use of antibiotics as an integral part of poultry and livestock production industry has recently received increasing attention as a contributory factor in the international emergence of antibiotic-resistant bacteria in human beings. To gauge the presence of the aforementioned scenario in the Indian context, a preliminary survey was conducted to assess the use of chlortetracycline (CTC) in 12 commercial layer farms and to quantify and confirm its residue in the egg. Samples of feed and eggs were collected at day 0 (prior to CTC addition), 3rd, 5th and 7th day during treatment and on the 9th and 14th day (2nd and 7th day after withdrawal of CTC) from each of the 12 commercial poultry farms studied. Concentration of CTC in feed was significantly (P<0.01) high on the 3rd, 5th and 7th day. On the 9th day and 14th day CTC concentration in feed was significantly (P<0.01) lower compared to the earlier 3 days studied. A highly significant difference (P<0.01) of the antibiotic residue in egg was observed in all the 5 days with high residual levels of CTC in egg. CTC in feed and its residue in egg were detected even on the 9th and 14th day respectively. 相似文献
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The pteropod mollusc, Clione limacina, swims by alternate dorsal–ventral flapping movements of its wing-like parapodia. The basic swim rhythm is produced by a network of pedal swim interneurons that comprise a swim central pattern generator (CPG). Serotonergic modulation of both intrinsic cellular properties of the swim interneurons and network properties contribute to swim acceleration, the latter including recruitment of type 12 interneurons into the CPG. Here we address the role of the type 12 interneurons in swim acceleration. A single type 12 interneuron is found in each of the pleural ganglia, which contributes to fast swimming by exciting the dorsal swim interneurons while simultaneously inhibiting the ventral swim interneurons. Each type 12 interneuron sends a single process through the pleural–pedal connective that branches in both ipsilateral and contralateral pedal ganglia. This anatomical arrangement allowed us to manipulate the influence of the type 12 interneurons on the swim circuitry by cutting the pleural–pedal connective followed by a “culture” period of 48 h. The mean swim frequency of cut preparations was reduced by 19% when compared to the swim frequency of uncut preparations when stimulated with 10−6 M serotonin; however, this decrease was not statistically significant. Additional evidence suggests that the type 12 interneurons may produce a short-term, immediate effect on swim acceleration while slower, modulatory inputs are taking shape. 相似文献
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70.
KLARA BJÖRG JAKOBSDÓTTIR þÓRA DÖGG JÖRUNDSDÓTTIR SIGURLAUG SKÍRNISDÓTTIR SIGRÍÐUR HJÖRLEIFSDÓTTIR GUÐMUNDUR Ó. HREGGVIÐSSON ANNA KRISTÍN DANÍELSDÓTTIR CHRISTOPHE PAMPOULIE 《Molecular ecology resources》2006,6(2):337-339
Nine out of 22 microsatellite primers tested were successfully amplified on three samples of cod Gadus morhua L. (two contemporary and one archived otolith samples). All loci were polymorphic (5–23 alleles/locus). The average observed heterozygosity across loci and samples was 0.625, ranging from 0.294 to 0.895 at each locus. All loci were under Hardy–Weinberg equilibrium, except PGmo56 that showed significant excess of heterozygotes in all studied samples. The isolated loci were suitable for degraded DNA and therefore useful for conducting a long‐term temporal study with DNA obtained from archived otoliths of cod. 相似文献