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61.
A human-specific subfamily of Alu sequences. 总被引:22,自引:0,他引:22
Of a total of 500,000 Alu family members, approximately 500 are present as a human-specific (HS) subfamily. Each of the HS subfamily members shares a high degree of nucleotide identity and is not present at orthologous positions in other primate genomes, suggesting that HS subfamily members have recently inserted within the human genome. This confirms the hypothesis that the majority of Alu family members are amplified copies of a "master" gene(s). This master gene appears to be amplifying at a rate much slower than that seen earlier in primate evolution. Some of the HS Alu subfamily members have amplified so recently that they are dimorphic in the human population, making them a potentially powerful tool for studies of human populations. 相似文献
62.
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
63.
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66.
Recognizing the forest for the trees: testing temporal patterns of cladogenesis using a null model of stochastic diversification 总被引:2,自引:1,他引:1
Computer simulations are developed and employed to examine the expected
temporal distributions of nodes under a null model of stochastic lineage
bifurcation and extinction. These Markovian models of phylogenetic process
were constructed so as to permit direct comparisons against empirical
phylogenetic trees generated from molecular or other information available
solely from extant species. For replicate simulated phylads with n extant
species, cumulative distribution functions (cdf's) of branching times were
calculated, and compared (using the Kolmogorov-Smirnov test statistic D) to
those from three published empirical trees. Molecular phylogenies for
columbine plants and avian cranes showed statistically significant
departures from the null expectations, in directions indicating recent and
ancient species' radiations, respectively, whereas a molecular phylogeny
for the Drosophila virilis species group showed no apparent historical
clustering of branching events. Effects of outgroup choice and phylogenetic
frame of reference were investigated for the columbines and found to have a
predictable influence on the types of conclusions to be drawn from such
analyses. To enable other investigators to statistically test for
nonrandomness in temporal cladogenetic pattern in empirical trees generated
from data on extant species, we present tables of mean cdf's and associated
probabilities under the null model for expected branching times in phylads
of varying size. The approaches developed in this report complement and
extend those of other recent methods for employing null models to assess
the statistical significance of pattern in evolutionary trees.
相似文献
67.
68.
Background
We report the expression pattern of 5S rDNA in the eggs of water frogs Rana lessonae, Rana ridibunda and Rana esculenta using the quantitative real-time PCR. This kind of research had never been performed before.Results
5S rDNA relative expression of the Rana ridibunda oocytes is approximately six times higher in comparison to the Rana lessonae oocytes. The oocytes of the investigated Rana esculenta frogs, in respect of 5S rDNA relative expression ratio, were very similar to the Rana ridibunda oocytes.Conclusion
We suggest the possibility of using 5S rDNA as the internal control gene, in the studies of relative mRNA quantitative assays in water frog oocytes, because of its characteristic specific expression pattern in the Rana lessonae, Rana ridibunda and Rana esculenta oocytes. 相似文献69.
Lake Kronotskoye (the Kronotsky Biosphere State Reserve, south-eastern Kamchatka Peninsula) contains three closely related
resident morphotypes charrs, which are considered to be either independent species (white charr Salvelinus albus, longhead charr Salvelinus kronocius, Schmidt’s charr Salvelinus schmidti) or a united lacustrine-riverine charrs, represented by several phenotypes. Salvelinus malma malma is isolated from the lake charr populations by an upstream migration barrier in the Kronotskaya River, which flows out of
the lake. We examined the level of genetic variability and divergence of mtDNA both between charrs from Kronotsky Lake and
between resident lacustrine charrs and the hypothetical ancestor species S. m. malma. The RFLP-PCR analysis was used to examine six regions (ND1/ND2, ND3/ND4L/ND4, ND5/ND6, COI/COII/A8, A8/A6/COIII/ND3, and
Cytb/D-loop), comprising ~80% of the mtDNA. Significantly different levels of diversity were found among the populations of lacustrine
charrs. S. albus and S. schmidti had the highest indices of mtDNA diversity among the investigated populations from the different habitats. Heterogeneity
tests revealed highly significant differentiation among lake populations and among riverine (Kronotskaya River) and lake (Lake
Kronotskoye) populations of charrs, indicating their reproductive isolation. Hierarchical analysis of molecular variance revealed
the following regularities of diversity distribution: the high proportion of interpopulation variation (93.25%) and low but
statistically significant subdivision between charr populations (6.75%, P < 0.001). Results of the present study suggest that the populations of S. albus, S. kronocius, S. schmidti belong to the S. m. malma phylogenetic group. The divergence value of mtDNA of resident charrs (0.0357–0.0010%) does not exceed the intraspecific variability
of S. m. malma. The analysis of the mtDNA haplotypes genealogy of charrs showed that the low values of nucleotide divergence reflect a short
period from the beginning of divergence from the ancestral lineages and are due to ancestral polymorphism, as well as to haplotype
exchange between the diverged phylogenetic groups as a result of introgressive hybridization. 相似文献
70.
Yongqiang Ma Rong Zhang Guangyu Sun Haixia Zhu Ming Tang Jean C. Batzer Mark L. Gleason 《Mycological Progress》2010,9(2):151-155
Zygophiala qianensis is described as a new fungal species associated with the cuticle of apple fruit sampled from an orchard in Shaanxi Province,
China. Conidiophores were separate, arising from superficial hyphae, erect, scattered, subcylindrical, irregularly flexuous,
consisting of four parts: a hyaline supporting cell that gives rise to a smooth, dark brown stipe, terminating in a finely
verruculose, medium brown apical cell that gives rise to (1–)2(–3) medium brown, finely verruculose, doliiform to ellipsoidal,
polyblastic conidiogenous cells, with 1–2 prominent scars, apical and lateral, darkened, thickened. Conidia were solitary,
fusiform to obclavate, hyaline, smooth and thick-walled, transversely (0–)1(–7)-septate, mostly 1–2-septate, prominently constricted
at the septum; apex obtuse, base subtruncate, with a darkened, thickened hilum. Zygophiala qianensis is compared morphologically to other species of Zygophiala, and a phylogenetic analysis of their DNA sequence data is presented. 相似文献