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1.
In order to understand the coordinate regulation between the alpha-like and beta-like globins during the developmental switches in hemoglobin synthesis, we have studied the rabbit alpha-like globin gene family. A cluster of six linked genes arranged 5'-zeta 1-alpha 1-theta 1-zeta 2-zeta 3-theta 2-3' has been isolated as a set of overlapping clones from a library of rabbit genomic DNA. Blot-hybridization analysis of genomic DNA not only confirms this linkage arrangement but also reveals the presence of additional zeta and theta genes. We propose that this gene cluster was generated by a block duplication of a set of alpha-like genes; the proposed duplication unit is zeta-zeta-alpha-theta. Further duplications of a zeta-zeta-theta set are also proposed to have occurred. As expected for a duplicated locus, the rabbit alpha-like gene cluster contains long blocks of internal homology. The Z homology block is about 7.2 kilobase pairs long and contains the zeta genes; the T homology block is about 4.7 kilobase pairs long and contains a theta gene. Surprisingly, both Z and T homology blocks are flanked by a common junction sequence (J) which contains a region very similar to the 3'-untranslated sequence of an alpha-globin gene. Analysis of the J sequences suggests a recombination mechanism by which the alpha gene could have been deleted from the second set of genes in the cluster (zeta 2-zeta 3-theta 2). The relationships among the genes in characterized alpha-like gene clusters in mammals are summarized. The rabbit gene cluster differs from those of other mammals principally in the loss of a gene orthologous to the human psi alpha 1 and in the block duplication of the zeta-zeta-alpha-theta gene set. 相似文献
2.
Plastid DNA was isolated from the chloroplasts of tomato (Lycopersicon esculentum var Traveler 76) leaves and the chromoplasts of ripe tomato fruit. Comparisons of the two DNAs were made by restriction endonuclease analysis using PvuII, HpaI, and Bg1I. No differences in the electrophoretic banding patterns of the restricted plastid DNAs were detected, indicating that no major rearrangements, losses, or gains of plastid DNA accompany the transition from chloroplast to chromoplast. 相似文献
3.
The rabbit C family of short, interspersed repeats. Nucleotide sequence determination and transcriptional analysis 总被引:9,自引:0,他引:9
When the entire adeno-associated virus (AAV) genome is inserted into a bacterial plasmid, infectious AAV genomes can be rescued and replicated when the recombinant AAV-plasmid DNA is transfected into human 293 cells together with helper adenovirus particles. We have taken advantage of this experimental system to analyze the effects of several classes of mutations on replication of AAV DNA. We obtained AAV mutants by molecular cloning in bacterial plasmids of naturally occurring AAV variant or defective-interfering genomes. Each of these mutants contains a single internal deletion of AAV coding sequences. Also, some of these mutant-AAV plasmids have additional deletions of one or both AAV terminal palindromes introduced during constructions in vitro. We show here that AAV mutants containing internal deletions were defective for replicative form DNA replication (rep-) but could be complemented by intact wild-type AAV. This indicates that an AAV replication function, Rep, is required for normal AAV replication. Mutants in which both terminal palindromes were deleted (ori-) were also replication defective but were not complementable by wild-type AAV. The cis-dominance of the ori- mutation shows that the replication origin is comprised in part of the terminal palindrome. Deletion of only one terminal palindrome was phenotypically wild-type and allowed rescue and replication of AAV genomes in which the deleted region was regenerated apparently by an intramolecular correction mechanism. One model for this correction mechanism is proposed. An AAV ori- mutant also complemented replication of AAV rep- mutants as efficiently as did wild-type AAV. These studies also revealed an unexpected additional property of the deletion mutants in that monomeric single-stranded single-stranded DNA accumulated very inefficiently even though monomeric single-stranded DNA from the complementing wild-type AAV did accumulate. 相似文献
4.
Sequences within and flanking hypersensitive sites 3 and 2 of the beta-globin locus control region required for synergistic versus additive interaction with the epsilon-globin gene promoter. 总被引:2,自引:0,他引:2 下载免费PDF全文
The locus control region is required for high-level, position-independent expression of mammalian beta-globin genes. It is marked by five major DNase hypersensitive sites (HSs) in a 16 kb region of chromatin, and the protein-DNA complexes that form these HSs may interact in a holocomplex that carries out the full function of the locus control region. Previous studies showed that a large rabbit DNA fragment containing both HS2 and HS3 in their native sequence context and spacing produced a much larger increase in expression of a linked reporter gene than the sum of the largest effects observed with DNA fragments containing HS2 or HS3 individually. To test whether this reflected a synergistic interaction between the 200-400 bp cores of the HSs or if this effect required additional sequences outside the cores, combinations of different restriction fragments containing HS2 or HS3 were tested for their ability to increase the expression of a hybrid epsilon-globin-luciferase reporter gene in transfected K562 cells. The results show that the human HS2 and HS3 cores do not interact either additively or synergistically with the reporter gene when juxtaposed, and separation by spacer DNA has little effect on their function. Fragments of human DNA containing cores plus flanking sequences for HS3 or HS2 show an additive effect in combination, whereas homologous fragments of rabbit DNA containing HS3 and HS2 interact synergistically. At least part of this difference localizes to the rabbit DNA fragment containing HS3, which can interact synergistically with the human DNA fragment containing HS2. The region 5' to the HS3 core plays a role both in the cooperative interaction observed with the rabbit DNA fragment and the domain-opening observed with the human DNA. A minor DNase HS maps to this region, and the pattern of sequence conservation is consistent with some difference in function between species. 相似文献
5.
The phosphorylation of several proteins in isolated nuclei from Pisum sativum L. was stimulated by spermine. Although spermine increased the general protein phosphorylation by 10 to 20%, it increased the phosphorylation of a 47 kilodalton polypeptide by 150%. By comparison other polyamines, spermidine, putrescine, and cadavarine had far less effect on the phosphorylation of the 47 kilodalton or any other polypeptide. Sodium fluoride was able to inhibit the phosphorylation of the 47 kilodalton polypeptide in the control, implying the participation of protein phosphatase(s) in the phosphorylation of nuclear proteins. Spermine stimulated the phosphorylation of the 47 kilodalton polypeptide over the controls, even in the presence of NaF. This result indicates that spermine probably activates a nuclear kinase, a conclusion supported also by thiophosphorylation data. The inability of ethyleneglycol-bis (β-amino-ethyl ether)-N, N′-tetraacetic acid and Compound 48/80, a calmodulin antagonist, to inhibit this spermine stimulated phosphorylation renders improbable any role of calcium and calmodulin in mediating this response. 相似文献
6.
Assignment of orthologous relationships among mammalian alpha-globin genes by examining flanking regions reveals a rapid rate of evolution 总被引:1,自引:0,他引:1
In order to study the relationships among mammalian alpha-globin genes, we
have determined the sequence of the 3' flanking region of the human alpha 1
globin gene and have made pairwise comparisons between sequenced
alpha-globin genes. The flanking regions were examined in detail because
sequence matches in these regions could be interpreted with the least
complication from the gene duplications and conversions that have occurred
frequently in mammalian alpha-like globin gene clusters. We found good
matches between the flanking regions of human alpha 1 and rabbit alpha 1,
human psi alpha 1 and goat I alpha, human alpha 2 and goat II alpha, and
horse alpha 1 and goat II alpha. These matches were used to align the
alpha-globin genes in gene clusters from different mammals. This alignment
shows that genes at equivalent positions in the gene clusters of different
mammals can be functional or nonfunctional, depending on whether they
corrected against a functional alpha-globin gene in recent evolutionary
history. The number of alpha-globin genes (including pseudogenes) appears
to differ among species, although highly divergent pseudogenes may not have
been detected in all species examined. Although matching sequences could be
found in interspecies comparisons of the flanking regions of alpha- globin
genes, these matches are not as extensive as those found in the flanking
regions of mammalian beta-like globin genes. This observation suggests that
the noncoding sequences in the mammalian alpha-globin gene clusters are
evolving at a faster rate than those in the beta-like globin gene clusters.
The proposed faster rate of evolution fits with the poor conservation of
the genetic linkage map around alpha-globin gene clusters when compared to
that of the beta-like globin gene clusters. Analysis of the 3' flanking
regions of alpha-globin genes has revealed a conserved sequence
approximately 100-150 bp 3' to the polyadenylation site; this sequence may
be involved in the expression or regulation of alpha-globin genes.
相似文献
7.
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9.
Seasonal resource availability may act as a constraint on plant phenology and thereby influence the range of growth responses
observed among populations of annual species, especially those occupying a wide range of environments. We compared a mesic
and a xeric population of the non-native, annual grass, Bromus tectorum, to examine phenology in response to interspecific competition and water availability. Using a target-neighborhood approach,
we assessed how phenological patterns of the two populations affected morphological and growth responses to enhanced resource
availability represented by late-season soil moisture. The xeric population exhibited a highly constrained phenology and was
unable to extend the growing season despite available soil resources. Because of the low phenotypic variation, allocation
to reproduction was similar across resource conditions. In contrast, the mesic population flowered later and showed a more
opportunistic phenology in response to late-season water availability. The mesic population was not able to maintain consistent
reproductive allocation at low resource levels. The responses of the two populations to late-season water availability were
not affected by the density of neighboring plants. We suggest that post-introduction selection pressure on B. tectorum in the xeric habitat has resulted in a more fixed phenology which limits opportunistic response to unpredictable, particularly
late-season resource availability. Opportunistic and fixed responses represent contrasting strategies for optimizing fitness
in temporally varying environments and, while both play important roles for ensuring reproductive success, these results suggest
that local adaptation to temporal resource variation may reflect a balance between flexible and inflexible phenology. 相似文献
10.
With the tremendous expansion of molecular sequence data in recent years, multiple alignment is arguably one of the two most important analytic techniques (the other being fast database searching). A number of useful approaches to this problem have previously been developed, but often they are limited to only a subset of multiple-alignment applications and cannot easily deal with the complex structural organization seen in an increasing number of sequences. For example, a single sequence may contain several domains of different evolutionary origins, and the multiplicities and relative ordering of these domains may be quite different among related sequences. Here we describe an integrated set of interactive Unix tools that combines several multiple-alignment techniques with traditional "dot-plot" visualization to provide a flexible environment for approaching complex sequence analysis problems. We apply these tools to the identification and characterization of "catalytic" domains in ras and rho/rac GTPase-activating proteins, to "Src homology" (SH2, SH3) domains in cytoplasmic signaling proteins, to repetitive sequence motifs in the alpha and beta subunits of protein prenyltransferases, and to regulatory DNA sequences in the locus control region of the beta-globin gene cluster. 相似文献