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31.
Aldair JW Pinto Maria M Figueiredo Fabiana L Silva Trycia Martins Marilene SM Michalick Washington L Tafuri Wagner L Tafuri 《Acta veterinaria Scandinavica》2011,53(1):1-8
Background
A nationwide survey on the microbial etiology of cases of subclinical mastitis in dairy cows was carried out on dairy farms in Sweden. The aim was to investigate the microbial panorama and the occurrence of antimicrobial resistance. Moreover, differences between newly infected cows and chronically infected cows were investigated.Methods
In total, 583 quarter milk samples were collected from 583 dairy cows at 226 dairy farms from February 2008 to February 2009. The quarter milk samples were bacteriological investigated and scored using the California Mastitis Test. Staphylococci were tested for betalactamase production and presence of resistance was evaluated in all specific udder pathogens. Differences between newly infected cows and chronically infected cows were statistically investigated using logistic regression analysis.Results
The most common isolates of 590 bacteriological diagnoses were Staphylococcus (S) aureus (19%) and coagulase-negative staphylococci (CNS; 16%) followed by Streptococcus (Str) dysgalactiae (9%), Str. uberis (8%), Escherichia (E.) coli (2.9%), and Streptococcus spp. (1.9%). Samples with no growth or contamination constituted 22% and 18% of the diagnoses, respectively. The distribution of the most commonly isolated bacteria considering only bacteriological positive samples were: S. aureus - 31%, CNS - 27%, Str. dysgalactiae - 15%, Str. uberis - 14%, E. coli - 4.8%, and Streptococcus spp. - 3.1%. There was an increased risk of finding S. aureus, Str. uberis or Str. dysgalactiae in milk samples from chronically infected cows compared to findings in milk samples from newly infected cows. Four percent of the S. aureus isolates and 35% of the CNS isolates were resistant to penicillin G. Overall, resistance to other antimicrobials than penicillin G was uncommon.Conclusions
Staphylococcus aureus and CNS were the most frequently isolated pathogens and resistance to antimicrobials was rare. 相似文献32.
Robin M. Tinghitella Emily G. Weigel Megan Head Janette W. Boughman 《Ecology and evolution》2013,3(9):2820-2831
Female mate choice is much more dynamic than we once thought. Mating decisions depend on both intrinsic and extrinsic factors, and these two may interact with one another. In this study, we investigate how responses to the social mating environment (extrinsic) change as individuals age (intrinsic). We first conducted a field survey to examine the extent of natural variation in mate availability in a population of threespine sticklebacks. We then manipulated the sex ratio in the laboratory to determine the impact of variation in mate availability on sexual signaling, competition, and mating decisions that are made throughout life. Field surveys revealed within season heterogeneity in mate availability across breeding sites, providing evidence for the variation necessary for the evolution of plastic preferences. In our laboratory study, males from both female‐biased and male‐biased treatments invested most in sexual signaling late in life, although they competed most early in life. Females became more responsive to courtship over time, and those experiencing female‐biased, but not male‐biased sex ratios, relaxed their mating decisions late in life. Our results suggest that social experience and age interact to affect sexual signaling and female mating decisions. Flexible behavior could mediate the potentially negative effects of environmental change on population viability, allowing reproductive success even when preferred mates are rare. 相似文献
33.
Joann A. Boughman 《American journal of human genetics》2006,78(3):527-528
34.
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36.
Premelting at the surface of ice crystals is caused by factors such as temperature, radius of curvature, and solute composition. When polycrystalline ice samples are warmed from well below the equilibrium melting point, surface melting may begin at temperatures as low as -15 degrees C. However, it has been reported (. Biophys. J. 65:1853-1865) that when polycrystalline ice was warmed in a differential scanning calorimetry (DSC) pan, melting began at about -50 degrees C, this extreme behavior being attributed to short-range forces. We show that there is no driving force for such premelting, and that for pure water samples in DSC pans curvature effects will cause premelting typically at just a few degrees below the equilibrium melting point. We also show that the rate of warming affects the slope of the DSC baseline and that this might be incorrectly interpreted as an endotherm. The work has consequences for DSC operators who use water as a standard in systems where subfreezing runs are important. 相似文献
37.
38.
Positions of multiple insertions in SSU rDNA of lichen-forming fungi 总被引:11,自引:3,他引:8
Lichen-forming fungi, in symbiotic associations with algae, frequently have
nuclear small subunit ribosomal DNA (SSU rDNA) longer than the 1,800
nucleotides typical for eukaryotes. The lichen-forming ascomycetous fungus
Lecanora dispersa contains insertions at eight distinct positions of its
SSU rDNA; the lichen-forming fungi Calicium tricolor and Porpidia
crustulata each contain one insertion. Insertions are not limited to fungi
that form lichens; the lichen ally Mycocalicium albonigrum also contains
two insertions. Of the 11 insertion positions now reported for
lichen-forming fungi and this ally, 6 positions are known only from
lichen-forming fungi. Including the 4 newly reported in this study,
insertions are now known from at least 17 positions among all reported SSU
rDNA sequences. Insertions, most of which are Group I introns, are reported
in fungal and protistan lineages and occur at corresponding positions in
genomes as phylogenetically distant as the nuclei of fungi, green algae,
and red algae. Many of these positions are exposed in the mature rRNA
tertiary structure and may be subject to independent insertion of introns.
Insertion of introns, accompanied by their sporadic loss, accounts for the
scattered distribution of insertions observed within the SSU rDNA of these
diverse organisms.
相似文献
39.
The extent of polylactosamine glycosylation of MDCK LAMP-2 is determined by its Golgi residence time 总被引:2,自引:1,他引:1
The increased polylactosamine glycosylation of LAMP-2 in MDCK cells
cultured for 1 day relative to cells cultured for 3 days has been
correlated with its slower rate of Golgi transit (Nabi and Rodriguez-
Boulan, 1993, Mol. Biol. Cell., 4, 627-635). To determine if the
differential polylactosamine glycosylation of LAMP-2 is a consequence of
glycosyltransferase expression levels, the activities of beta1- 6GlcNAc-TV,
beta1-3GlcNAc-T(i), beta1-2GlcNAc-TI, beta1, 4Gal-T, alpha2- 6sialyl-T, and
alpha2-3sialyl-T were assayed and no significant differences in the
activities of these enzymes in 1 and 3 day cell extracts were detected.
During MDCK epithelial polarization, the Golgi apparatus undergoes
morphological changes and apiconuclear Golgi networks were more evident in
3 day cells. Treatment with nocodazole disrupted Golgi networks and
generated numerous Golgi clusters in both 1 day and 3 day cells. In the
presence of nocodazole the differential migration of LAMP-2 in 1 and 3 day
MDCK cells was maintained and could be eliminated by treatment with
endo-beta-galactosidase, indicating that gross Golgi morphology did not
influence the extent of LAMP-2 polylactosamine glycosylation. Nocodazole
treatment did, however, result in the faster migration of LAMP-2 which was
not due to modification of core N-glycans as the precursor form of the
glycoprotein migrated with an identical molecular size. Following
incubation at 20 degrees C, which prevents the exit of proteins from the
trans-Golgi network, the molecular size of LAMP-2 increased to a similar
extent in both 1 and 3 day MDCK cells. Extending the time of incubation at
20 degrees C did not influence the size of LAMP-2, demonstrating that its
glycosylation is modified not by its retention within the Golgi but rather
by its equivalent slower Golgi passage at the lower temperature in both 1
and 3 day cells. An identical effect was observed in nocodazole treated
cells, demonstrating that Golgi residence time determines the extent of
LAMP-2 polylactosamine glycosylation, even in isolated Golgi clusters.
相似文献
40.
Incorporation of axonally transported glycoproteins into axolemma during nerve regeneration 总被引:14,自引:4,他引:10 下载免费PDF全文
The insertion of axonally transported fucosyl glycoproteins into the axolemma of regenerating nerve sprouts was examined in rat sciatic motor axons at intervals after nerve crush. [(3)H]Fucose was injected into the lumbar ventral horns and the nerves were removed at intervals between 1 and 14 d after labeling. To follow the fate of the “pulse- labeled” glycoproteins, we examined the nerves by correlative radiometric and EM radioautographic approaches. The results showed, first, that rapidly transported [(3)H]fucosyl glycoproteins were inserted into the axolemma of regenerating sprouts as well as parent axons. At 1 d after delivery, in addition to the substantial mobile fraction of radioactivity still undergoing bidirectional transport within the axon, a fraction of label was already associated with the axolemma. Insertion of labeled glycoproteins into the sprout axolemma appeared to occur all along the length of the regenerating sprouts, not just in sprout terminals. Once inserted, labeled glycoproteins did not undergo extensive redistribution, nor did they appear in sprout regions that formed (as a result of continued outgrowth) after their insertion. The amount of radioactivity in the regenerating nerves decreased with time, in part as a result of removal of transported label by retrograde transport. By 7-14 d after labeling, radioautography showed that almost all the remaining radioactivity was associated with axolemma. The regenerating sprouts retained increased amounts of labeled glycoproteins; 7 or 14 d after labeling, the regenerating sprouts had over twice as much of radioactivity as comparable lengths of control nerves or parent axons. One role of fast axonal transport in nerve regeneration is the contribution to the regenerating sprout of glycoproteins inserted into the axolemma; these membrane elements are added both during longitudinal outgrowth and during lateral growth and maturation of the sprout. 相似文献