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Distribution of isoaccepting tRNAs and codons for proline and glycine in collagenous and noncollagenous chicken tissues 总被引:2,自引:0,他引:2
B Ouenzar B Agoutin F Reinisch D Weill F Perin G Keith T Heyman 《Biochemical and biophysical research communications》1988,150(1):148-155
The relation between codon usage and tRNA content for proline and glycine, the major constituents of collagen, was studied in two tissues: the magnum of laying hen oviduct and the leg tendons of chick embryo where collagen is produced. Although the relative contents of tRNA(GCCGly) and tRNA(IGGPro) in tendons, as compared to magnum indicate a specialization of the tRNA population for collagen synthesis, the distribution of the preponderant codons in collagen mRNA is correlated but at a lesser extent to that of their cognate tRNAs. 相似文献
4.
The relative amounts of iso-tRNAsGly and iso-tRNAsPro existing in chick embryo tendon are indicative of a specialization of the tRNA population for collagen synthesis. These amounts are not modified (i) in primary avian tendon (PAT) cells in culture for which the procollagen production varies from about 10% of total protein synthesis to 60% and (ii) in tendons from immature chicks, which show a 3-fold decrease of procollagen production with increasing age. The characteristic tRNA pattern was not maintained in cells which had lost the ability to make high levels of collagen as observed in the cases of: (i) PAT cells reaching confluency; (ii) virus-transformed PAT cells and (iii) tendon from adult chick. Our data are consistent with the idea that tendon tRNA specialization for collagen synthesis is a differentiation feature independent of the expression level of the collagenic function but related to its maintenance. 相似文献
5.
Three families presenting one or several cases of brain or ophthalmic abnormalities and an hypopituitarism at least by one of the members have been observed. In the first family, the mother and one of her sons present bilateral choroidoretineal coloboma with amblyopia; one of these two suffers as well from panhypopituitarism. In the second family two premature twins, a brother and his sister, present a syndrome with hypophyseal dwarfism and ophthalmic abnormalities, consisting in the boy's case in an peripapillary depigmentation with no visible sight trouble whereas girl's is showing an extreme microphthalmia with major mental retardation. In the third family two 2nd degree cousins present a panhypopituitarism but only one of the two reveals through neuroradiological investigations corpus callosum and septum lucidum agenesia. The karyotype is normal in all the cases. An hereditary mechanism appears clearly in the first family. It is possible in the second, probable in the third one. 相似文献
6.
A comparative description of mitochondrial DNA differentiation in selected avian and other vertebrate genera 总被引:14,自引:1,他引:13
Levels of mitochondrial DNA (mtDNA) sequence divergence between species
within each of several avian (Anas, Aythya, Dendroica, Melospiza, and
Zonotrichia) and nonavian (Lepomis and Hyla) vertebrate genera were
compared. An analysis of digestion profiles generated by 13-18 restriction
endonucleases indicates little overlap in magnitude of mtDNA divergence for
the avian versus nonavian taxa examined. In 55 interspecific comparisons
among the avian congeners, the fraction of identical fragment lengths (F)
ranged from 0.26 to 0.96 (F = 0.46), and, given certain assumptions, these
translate into estimates of nucleotide sequence divergence (p) ranging from
0.007 to 0.088; in 46 comparisons among the fish and amphibian congeners, F
values ranged from 0.00 to 0.36 (F = 0.09), yielding estimates of P greater
than 0.070. The small mtDNA distances among avian congeners are associated
with protein-electrophoretic distances (D values) less than approximately
0.2, while the mtDNA distances among assayed fish and amphibian congeners
are associated with D values usually greater than 0.4. Since the
conservative pattern of protein differentiation previously reported for
many avian versus nonavian taxa now appears to be paralleled by a
conservative pattern of mtDNA divergence, it seems increasingly likely that
many avian species have shared more recent common ancestors than have their
nonavian taxonomic counterparts. However, estimates of avian divergence
times derived from mtDNA- and protein-calibrated clocks cannot readily be
reconciled with some published dates based on limited fossil remains. If
the earlier paleontological interpretations are valid, then protein and
mtDNA evolution must be somewhat decelerated in birds. The empirical and
conceptual issues raised by these findings are highly analogous to those in
the long-standing debate about rates of molecular evolution and times of
separation of ancestral hominids from African apes.
相似文献
7.
Methods for computing the standard errors of branching points in an evolutionary tree and their application to molecular data from humans and apes 总被引:23,自引:2,他引:21
Statistical methods for computing the standard errors of the branching
points of an evolutionary tree are developed. These methods are for the
unweighted pair-group method-determined (UPGMA) trees reconstructed from
molecular data such as amino acid sequences, nucleotide sequences,
restriction-sites data, and electrophoretic distances. They were applied to
data for the human, chimpanzee, gorilla, orangutan, and gibbon species.
Among the four different sets of data used, DNA sequences for an
895-nucleotide segment of mitochondrial DNA (Brown et al. 1982) gave the
most reliable tree, whereas electrophoretic data (Bruce and Ayala 1979)
gave the least reliable one. The DNA sequence data suggested that the
chimpanzee is the closest and that the gorilla is the next closest to the
human species. The orangutan and gibbon are more distantly related to man
than is the gorilla. This topology of the tree is in agreement with that
for the tree obtained from chromosomal studies and DNA-hybridization
experiments. However, the difference between the branching point for the
human and the chimpanzee species and that for the gorilla species and the
human-chimpanzee group is not statistically significant. In addition to
this analysis, various factors that affect the accuracy of an estimated
tree are discussed.
相似文献
8.
J Lamy M Farges R Vargues J Weill 《Comptes rendus des séances de la Société de biologie et de ses filiales》1969,162(11):2003-2009
9.
The polarization of fluorescence of a chromophore chemically bound on the NH2 end of a poly(L -benzyl glutamate) molecule has been studied as a function of temperature, viscosity, and solvent. The relaxation times depend on both the overall rotation of the helix and the local rotation of the endgroup. In m–cresol the endgroup is rigidly bound and the rotational diffusion constant of the molecule is in good agreement with the values obtained by Kerr effect and dielectric relaxation. In other helicogenic solvents (DMF, DCE, etc.) the local rotation is nearly free. In m-cresol-DMF mixtures a sharp decrease of the polarization around a composition of 40% DMF can be interpreted as a change in the freedom of rotation of the endgroup. No discontinuity in the optical rotation is observed in the solvent mixture. The question of how a rapidly rotating endgroup could show an extrinsic Cotton effect as observed by Bloutand Yamaoka for the system Acridine Orange–PBLG in chloroform is then raised. Polarization of fluorescence measurements on this system show a nearly complete freedom of rotation of the dye and OH D measurements show no detectable Cotton effect in the dye absorption band. 相似文献
10.
The study of the orientation of single-stranded DNA in polyacrylamide gels in denaturing conditions has been undertaken by electric birefringence in order to determine the mechanism involved in the electrophoretic transport. The presence of an overshoot in the birefringence signal, when applying the electric field, and the study of the influences of the electric field and of the gel concentration on the dynamics show that a mechanism of reptation with elongation of the molecule occurs in polyacrylamide gels with low T values. Therefore it is suggested that the use of pulsed fields in sequencing electrophoresis is possible and can lead to a large increase of the length of the fragments that can be sequenced in one single run. 相似文献