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991.
992.
993.
Sanchez D; Ganfornina MD; Gutierrez G; Bastiani MJ 《Molecular biology and evolution》1998,15(4):415-426
Arthropodan hemocyanins, prophenoloxidases (PPOs), and insect hexamerins
form a superfamily of hemolymph proteins that we propose to call the AHPH
superfamily. The evolutionary and functional relationships of these
proteins are illuminated by a new embryonic hemolymph protein (EHP) that is
expressed during early stages of development in the grasshopper embryo. EHP
is a 78-kDa soluble protein present initially in the yolk sac content, and
later in the embryonic hemolymph. Protein purification and peptide
sequencing were used to identify an embryonic cDNA clone coding for EHP. In
situ hybridization identifies hemocytes as EHP-expressing cells. As deduced
from the cDNA clone, EHP is a secreted protein with two potential
glycosylation sites. Sequence analysis defines EHP as a member of the AHPH
superfamily. Phylogenetic analyses with all the currently available AHPH
proteins, including EHP, were performed to ascertain the evolutionary
history of this protein superfamily. We used both the entire protein
sequence and each of the three domains present in the AHPH proteins. The
phylogenies inferred for each of the domains suggest a mosaic evolution of
these protein modules. Phylogenetic and multivariate analyses consistently
group EHP with crustacean hemocyanins and, less closely, with insect
hexamerins, relative to cheliceratan hemocyanins and PPOs. The grasshopper
protein rigorously preserves the residues involved in oxygen binding,
oligomerization, and allosteric regulation of the oxygen transport
proteins. Although insects were thought not to have hemocyanins, we propose
that EHP functions as an oxygen transport or storage protein during
embryonic development.
相似文献
994.
995.
996.
Multidimensional heteronuclear NMR studies have been applied to the
resonance assignment and conformational analysis of 13C-enriched
Neu5Acalpha2-3Galbeta1-4Glc. It is demonstrated that three-dimensional
ROESY-HSQC experiments provide through-space distance restraints which
cannot be observed with conventional homonuclear 1H techniques due to
resonance overlap. In particular, connectivities demonstrating the
existence of the "anti" conformation about the Galbeta1-4Glc glycosidic
linkage are unambiguously observed. It is shown that 13C isotopic
enrichment of the trisaccharide at a level >95% enables straightforward
measurement of trans-glycosidic 1H-13C and 13C-13C coupling constants and a
Karplus-type relation is derived for the latter. In total 15 conformational
restraints were obtained for the trisaccharide in aqueous solution, all of
which were in excellent agreement with theoretical parameters computed from
a 5 ns molecular dynamics simulation of the glycan.
相似文献
997.
Phage Peptide Libraries 总被引:1,自引:0,他引:1
Filamentous phage particles have been central in the construction of libraries displaying vast numbers of random peptides. These random peptides can be antigenically presented as fusions to coat proteins III and VIII of the phage. The isolation of ligate-reactive phage from an immense background of nonspecific phage is achieved by the biopanning process. Enrichment of reactive phage relative to unreactive phage occurs with alternate rounds of affinity selection to the desired molecular target and amplification of the specifically bound phage. This allows the isolation of rare binding species contained in the phage peptide libraries. Each phage particle contains the information in its genome pertaining to the type of random peptide insert displayed. Hence, the identification of binding motifs displayed on ligate-reactive phage is revealed by sequencing the relevant insert site in the phage genome. Phage peptide libraries have been used to isolate ligands to an array of protein ligates. The libraries have proved particularly effective in defining the binding sites of monoclonal antibodies and to some extent polyclonal sera. The analysis of the peptide insert sequences of a number of different clones of antibody binding phage can reveal a great deal about the nature and restriction of the amino acid residues critical for the antibody–antigen interaction. 相似文献
998.
Analysis of the Escherichia coli genome VI: DNA sequence of the region from 92.8 through 100 minutes. 总被引:20,自引:0,他引:20
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V Burland G Plunkett rd H J Sofia D L Daniels F R Blattner 《Nucleic acids research》1995,23(12):2105-2119
999.
Molecular phylogenetics of Stenodermatini bat genera: congruence of data from nuclear and mitochondrial DNA 总被引:2,自引:1,他引:1
Van den Bussche RA; Baker RJ; Wichman HA; Hamilton MJ 《Molecular biology and evolution》1993,10(5):944-959
Within the tribe Stenodermatini the systematics of the complex of species
allied with the genus Artibeus has generated several alternative
phylogenetic hypotheses. The most recent treatment recognized four genera
(Artibeus, Dermanura, Enchisthenes, and Koopmania) and suggested that the
most recent common ancestor of these four genera would include the common
ancestor of all other currently recognized Stenodermatini genera except
Sturnira. To test this hypothesis, we examined an EcoRI-defined nuclear
satellite DNA repeat and 402 bp of DNA sequence variation from the
mitochondrial cytochrome b gene. Phylogenetic conclusions based on Southern
blot analyses, in situ hybridization, and mitochondrial DNA sequence data
indicate that Enchisthenes is not closely related to Dermanura, Artibeus,
or Koopmania and that Dermanura, Artibeus, and Koopmania shared a common
ancestor after diverging from the remainder of the Stenodermatini. If our
conclusions are correct, then justification for recognizing Dermanura and
Koopmania as generically distinct from Artibeus must be based on the
magnitude of difference that distinguishes each rather than on the
conclusion that to place them as congeneric with Artibeus creates a
paraphyletic taxon.
相似文献
1000.
We measured F420-dependent N5,N10-methylenetetrahydro-methanopterin dehydrogenase, N5, N10-methenyltetrahydro-methanopterin cyclohydrolase, and F420-reducing hydrogenase levels in Methanosarcina barkeri grown on various substrates. Variation in dehydrogenase levels during growth on a specific substrate was usually <3-fold, and much less for cyclohydrolase. H2–CO2-, methanol-, and H2–CO2+ methanol-grown cells had roughly equivalent levels of dehydrogenase and cyclohydrolase. In acetate-grown cells cyclohydrolase level was lowered 2 to 3-fold and dehydrogenase 10 to 80-fold; this was not due to repression by acetate, since, if cultures growing on acetate were supplemented with methanol or H2–CO2, dehydrogenase levels increased 14 to 19-fold, and cyclohydrolase levels by 3 to 4-fold. Compared to H2–CO2- or methanol-grown cells, acetate-or H2–CO2 + methanol-grown cells had lower levels of and less growth phase-dependent variation in hydrogenase activity. Our data are consistent with the following hypotheses: 1. M. barkeri oxidizes methanol via a portion of the CO2-reduction pathway operated in the reverse direction. 2. When steps from CO2 to CH3-S-CoM in the CO2-reduction pathway (in either direction) are not used for methanogenesis, hydrogenase activity is lowered.Abbreviations MF
methanofuran
- H4MPT
5,6,7,8-tetrahydromethanopterin
- HS-HTP
7-mercaptoheptanoylthreonine phosphate
- CoM-S-S-HTP
heterodisulfide of HS-CoM and HS-HTP
- F420
coenzyme F420 (a 7,8-didemethyl-8-hydroxy-5-deaza-riboflavin derivative)
- H2F420
reduced coenzyme F420
- HC+=H4MPT
N5,N10-methenyl-H4MPT
- H2C=H4MPT
N5,N10-methylene-H4MPT
- H3C=H4MPT
N5-methyl-H4MPT
- BES
2-bromoethanesulfonic acid 相似文献