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961.
Benjamin C. Stone 《Nordic Journal of Botany》1993,13(1):55-57
The genus Parardisia is shown to be synonymous with the large pantropical genus Ardisia . The species on which Parardisia was based, A. involucrata , should therefore retain that original name. The only other species assigned to Parardisia, P. gamblei , is reduced to synonymy with Ardisia moultonii; both were described (and still known only) from Sarawak. The first species retains its position in Ardisia subgenus Tinus , while the latter belongs in subgenus Tinopsis . 相似文献
962.
Approximately 24% (170/710) of porcine (dG-dT)n·(dC-dA)n microsatellites isolated in our laboratory are associated with a previously described porcine Short Interdispersed Element (SINE) termed PRE-1 SINE. Another 5.6% (40/710) of the microsatellites were adjacent to two previously unidentified SINE sequences, which we have designated ARE-1P (Artiodactyl Repetitive Element-1 Porcine) and ARE-2P. The ARE repeats were also found in bovine microsatellite and genomic sequences in the GenBank database. Genotypic information was obtained from 68.9% of primers where at least one primer sequence was obtained from the PRE-1 SINE and 66.6% of primer pairs designed from the ARE SINEs. The use of primers derived from SINEs significantly increases the number of primer pairs available for genetic linkage studies in swine. 相似文献
963.
R. T. Stone J. C. Pulido G. M. Duyk S. M. Kappes J. W. Keele C. W. Beattie 《Mammalian genome》1995,6(10):714-724
A bovine genomic phagemid library was constructed with randomly sheared DNA. Enrichment of this single-stranded DNA library with CA or GT primers resulted in 45% positive clones. The 14% of positive clones with (CA · GT)>12, and not containing flanking repetitive elements, were sequenced, and the efficiency of marker production was compared with random M13 bacteriophage libraries. Primer sequences and genotyping information are presented for 390 informative bovine microsatellite markers. The genomic frequency for 11 tri- and tetranucleotide repeats was estimated by hybridization to a lambda genomic library. Only GCT, GGT, and GGAT were estimated to have a frequency of >100 per genome. Enrichment of the phagemid library for these repeats failed to provide a viable source of microsatellite markers in the bovine. Comparison of map interval lengths between 100 markers from the enriched library prepared from randomly sheared DNA and M13 bacteriophage libraries prepared from Mbo1 restriction digests suggested no bias in skeletal genomic coverage based on source of small insert DNA. In conclusion, enrichment of the bovine phagemid library provides a sufficient source of microsatellites so that small repeat lengths and flanking repetitive sequences common in the bovine can be eliminated, resulting in a high percentage of informative markers.The nucleotide sequence data reported in this paper have been submitted to GenBank and have been assigned the accession numbers U25689 and U25690. 相似文献
964.
A mutant rat cell clone that suppresses the transformation defects of RAS effector loop substitutions is heterozygous for mutations in c-raf1 and MEK1. The mutant cells can be transformed by many otherwise defective RAS effector mutants, including RAS genes with the effector regions of distantly related GTPases, even though the encoded RAS proteins do not interact with either the mutant or wild-type RAF in Saccharomyces cerevisiae. While the significance of the c-raf1 mutation is unclear, the MEK1 mutation increases MEK1 activity and leads to activation of mitogen-activated protein kinase. The mutant MEK1 is coupled to the epidermal growth factor pathway but exhibits decreased physical interaction with RAF. When overexpressed, the MEK1 mutation is transforming and causes hyperphosphorylation of RAF. Signalling from RAS to MEK1 may be mediated by something other than RAF alone, but signalling through MEK1 is probably sufficient for RAS transformation. 相似文献
965.
Joel D. Stone Carla C. Heise Don R. Canfield Mariano J. Elices Satya Dandekar 《Journal of medical primatology》1995,24(3):132-140
We investigated SIV infection and expression of adhesion molecules in the small intestine of rhesus macaques infected with pathogenic SIV (SIVmac) or nonpathogenic clone (SIV1A11). There was a wider dissemination and marked difference in tissue localization of SIVmac relative to SIV1A11. Our results also indicate that viral pathogenicity is associated with increased migration of inflammatory cells expressing VLA-α4, LFA-1α, Mac-1α, ICAM-1, and β2 integrin into the intestinal mucosa. 相似文献
966.
967.
J. R. Stone 《Biological journal of the Linnean Society. Linnean Society of London》1998,64(2):223-238
Strombid shells were used to exemplify how to construct ontogenic tracks and evolutionary vestiges in morphological space (morphospace). Parameters in a mathematical model of shell form were used to construct morphospaces. Ontogenic information was mapped into these morphospaces to form 'tracks' Ontogenic tracks showed that the predominant trend of morphological evolution of strombid species consisted of an increase of vertical dimensions of whorls (apertures). Integrating information extracted from cladograms with ontogenic tracks in morphospace, 'evolutionary vestiges' were determined and used to infer and reconstruct ancestral shell forms. 相似文献
968.
The pheromone-responsive Gβ subunit of Saccharomyces cerevisiae (encoded by STE4) is rapidly phosphorylated at multiple sites when yeast cells are exposed to mating pheromone. It has been shown that a mutant
form of Ste4 lacking residues 310–346, ste4Δ310–346, cannot be phosphorylated, and that its expression leads to defects in
recovery from pheromone stimulation. Based on these observations, it was proposed that phosphorylation of Ste4 is associated
with an adaptive response to mating pheromone. In this study we used site-directed mutagenesis to create two phosphorylation
null (Pho−) alleles of STE4: ste4-T320 A/S335A and ste4-T322 A/S335A and ste4-T322A/S335A. When expressed in yeast, these mutant forms of Ste4 remained unphosphorylated upon pheromone stimulation. The elimination
of Ste4 phosphorylation has no discernible effect on either signaling or adaptation. In addition, disruption of the FUS3 gene, which encodes a pheromone-specific MAP kinase, leads to partial loss of pheromone-induced Ste4 phosphorylation. Two-hybrid
analysis suggests that the ste4Δ310–346 deletion mutant is impaired in its interaction with Gpa1, the pheromone-responsive
Gα of yeast, whereas the Ste4-T320A/S335A mutant has normal affinity for Gpa1. Taken together, these results indicate that pheromone-induced
phosphorylation of Ste4 is not an adaptive mechanism, and that the adaptive defect exhibited by the 310–346 deletion mutant
is likely to be due to disruption of the interaction between Ste4 and Gpa1.
Received: 14 February 1998 / Accepted: 28 February 1998 相似文献
969.
Productive persistent infection of hematopoietic cells by human foamy virus. 总被引:3,自引:2,他引:1
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Human foamy virus can establish persistent infections in human hematopoietic cell lines, such as H92.1.7 (erythroblastoid cells), Jurkat (CD4+ T cells), and U937 (myeloid-monocytic cells). The infection is characterized by constant production of infectious viruses (for > 2 1/2 years) with no cytopathic effects on the host cells. Electron microscopy of the infected cells showed a viral morphology similar to that observed for particles produced after acute infection. We have detected, in addition to the full-length form of bel1, a previously described deletion in the bel1 gene of the proviral DNA in these cells. RNA containing this 301-bp deletion, which mapped to the splice donor and acceptor sites of the intron of the bet gene, was also found in encapsidated virion RNA. However, the presence of this defective provirus harboring the deletion in bel1 does not prevent productive persistence in these chronically infected cells, since the virus titer does not decrease during cultivation. 相似文献
970.
Identification of a 23S rRNA Gene Mutation in Clarithromycin-Resistant Helicobacter pylori 总被引:10,自引:0,他引:10
Gregory G. Stone Dee Shortridge Robert K. Flamm James Versalovic † Jill Beyer Ken Idler ‡ Laura Zulawinski † S. Ken Tanaka 《Helicobacter》1996,1(4):227-228
Background Transition mutations (A-G) at residue 2143, cognate to position 2058 in the Escherichia coli 23S rRNA gene, have been shown to confer resistance to macrolides in Helicobacter pylori. This study reports the finding that transversion mutations (A-C) can occur at 2143 as well.
Materials and Methods. Three clarithromycin-resistant H. pylori isolated from three different patients after treatment with clarithromycin were analyzed for point mutations by cycle sequencing of a 163-bp amplified region surrounding residue 2143 within the conserved loop of the 23S rRNA gene.
Results. Nucelotide sequence comparisons of a 163-bp amplified product revealed that A-C transversion mutations occurred at position 2143. H. pylori isolated from the patients prior to treatment were susceptible to clarithromycin and displayed no polymorphism at 2143.
Conclusion. This is the first report to show that A-C transversion mutations at position 2143 can confer resistance to clarithromycin in H. pylori and further support the role that mutations at position 2143 play in conferring macrolide resistance in H. pylori. 相似文献
Materials and Methods. Three clarithromycin-resistant H. pylori isolated from three different patients after treatment with clarithromycin were analyzed for point mutations by cycle sequencing of a 163-bp amplified region surrounding residue 2143 within the conserved loop of the 23S rRNA gene.
Results. Nucelotide sequence comparisons of a 163-bp amplified product revealed that A-C transversion mutations occurred at position 2143. H. pylori isolated from the patients prior to treatment were susceptible to clarithromycin and displayed no polymorphism at 2143.
Conclusion. This is the first report to show that A-C transversion mutations at position 2143 can confer resistance to clarithromycin in H. pylori and further support the role that mutations at position 2143 play in conferring macrolide resistance in H. pylori. 相似文献