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91.
92.
Social play behaviour is a well-described phenomenon, almost ubiquitous among mammals. Despite its prevalence, social play takes several forms and may vary in function across species. For solitary species, the function of play outside of the family group remains unclear. Here, we describe the motor patterns of play among non-littermate wild brown bears Ursus arctos of different age-sex class. Play was documented during a time of abundant food availability in three different scenarios: play among non-littermate subadults, play among non-littermate cubs, and play among a ‘group’ of bears of different age and sex class. We used a previously described behavioural ethogram to recognise play. Play followed typical motor patterns and postures expressed by bears during play-fighting: relaxed face, puckered-lip, ears partially flattened to crescent, wrestling, jaw gaping, play-biting, paw-swatting, and lunging. No vocalisations were conducted during play bouts. Older bears displayed ‘self-handicapping’ and ‘role-reversal’ in the play postures they selected when playing with younger bears, suggesting that tactics vary according to age class and dominance ranking. Playing likely allows for the evaluation of conspecifics in a non-aggressive way during times of reduced competition and could also relieve stress in complex social situations. 相似文献
93.
J Arthos K C Deen M A Chaikin J A Fornwald G Sathe Q J Sattentau P R Clapham R A Weiss J S McDougal C Pietropaolo 《Cell》1989,57(3):469-481
The CD4 molecule is a T cell surface glycoprotein that interacts with high affinity with the envelope glycoprotein of the human immunodeficiency virus, HIV, thus serving as a cellular receptor for this virus. To define the sites on CD4 essential for binding to gp120, we produced several truncated, soluble derivatives of CD4 and a series of 26 substitution mutants. Quantitative binding analyses with the truncated proteins demonstrate that the determinants for high affinity binding lie solely with the first 106 amino acids of CD4 (the V1 domain), a region having significant sequence homology to immunoglobulin variable regions. Analysis of the substitution mutants further defines a discrete binding site within this domain that overlaps a region structurally homologous to the second complementarity-determining region of antibody variable domains. Finally, we demonstrate that the inhibition of virus infection and virus-mediated cell fusion by soluble CD4 proteins depends on their association with gp120 at this binding site. 相似文献
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Pseudomonas aeruginosa diaminopimelate decarboxylase: evolutionary relationship with other amino acid decarboxylases 总被引:1,自引:0,他引:1
Martin C; Cami B; Yeh P; Stragier P; Parsot C; Patte JC 《Molecular biology and evolution》1988,5(5):549-559
The lysA gene encodes meso-diaminopimelate (DAP) decarboxylase
(E.C.4.1.1.20), the last enzyme of the lysine biosynthetic pathway in
bacteria. We have determined the nucleotide sequence of the lysA gene from
Pseudomonas aeruginosa. Comparison of the deduced amino acid sequence of
the lysA gene product revealed extensive similarity with the sequences of
the functionally equivalent enzymes from Escherichia coli and
Corynebacterium glutamicum. Even though both P. aeruginosa and E. coli are
Gram-negative bacteria, sequence comparisons indicate a greater similarity
between enzymes of P. aeruginosa and the Gram- positive bacterium C.
glutamicum than between those of P. aeruginosa and E. coli enzymes.
Comparison of DAP decarboxylase with protein sequences present in data
bases revealed that bacterial DAP decarboxylases are homologous to mouse
(Mus musculus) ornithine decarboxylase (E.C.4.1.1.17), the key enzyme in
polyamine biosynthesis in mammals. On the other hand, no similarity was
detected between DAP decarboxylases and other bacterial amino acid
decarboxylases.
相似文献
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98.
Microsatellite genetic distances between oceanic populations of the humpback whale (Megaptera novaeangliae) 总被引:1,自引:0,他引:1
Valsecchi E; Palsboll P; Hale P; Glockner-Ferrari D; Ferrari M; Clapham P; Larsen F; Mattila D; Sears R; Sigurjonsson J; Brown M; Corkeron P; Amos B 《Molecular biology and evolution》1997,14(4):355-362
Mitochondrial DNA haplotypes of humpback whales show strong segregation
between oceanic populations and between feeding grounds within oceans, but
this highly structured pattern does not exclude the possibility of
extensive nuclear gene flow. Here we present allele frequency data for four
microsatellite loci typed across samples from four major oceanic regions:
the North Atlantic (two mitochondrially distinct populations), the North
Pacific, and two widely separated Antarctic regions, East Australia and the
Antarctic Peninsula. Allelic diversity is a little greater in the two
Antarctic samples, probably indicating historically greater population
sizes. Population subdivision was examined using a wide range of measures,
including Fst, various alternative forms of Slatkin's Rst, Goldstein and
colleagues' delta mu, and a Monte Carlo approximation to Fisher's exact
test. The exact test revealed significant heterogeneity in all but one of
the pairwise comparisons between geographically adjacent populations,
including the comparison between the two North Atlantic populations,
suggesting that gene flow between oceans is minimal and that dispersal
patterns may sometimes be restricted even in the absence of obvious
barriers, such as land masses, warm water belts, and antitropical migration
behavior. The only comparison where heterogeneity was not detected was the
one between the two Antarctic population samples. It is unclear whether
failure to find a difference here reflects gene flow between the regions or
merely lack of statistical power arising from the small size of the
Antarctic Peninsula sample. Our comparison between measures of population
subdivision revealed major discrepancies between methods, with little
agreement about which populations were most and least separated. We suggest
that unbiased Rst (URst, see Goodman 1995) is currently the most reliable
statistic, probably because, unlike the other methods, it allows for
unequal sample sizes. However, in view of the fact that these alternative
measures often contradict one another, we urge caution in the use of
microsatellite data to quantify genetic distance.
相似文献
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