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211.
The molecular organization of the beta-globin complex of the deer mouse, Peromyscus maniculatus 总被引:1,自引:0,他引:1
Padgett RW; Loeb DD; Snyder LR; Edgell MH; Hutchison CA d 《Molecular biology and evolution》1987,4(1):30-45
Recombinant DNA clones have been isolated that contain 80 kb of the
beta-globin complex from the deer mouse, Peromyscus maniculatus.
Comparisons of this complex with that from the laboratory mouse, Mus
domesticus (with an order 5'-Hbby, Hbb-bhO, Hbb-bhl, Hbb-bh2, Hbb-bh3,
Hbb-bl, Hbb-b2 3') highlight organizational trends in the beta-globin
complex since the two species diverged. Unlike other mammals studied thus
far, the deer mouse possesses three adult genes. Partial sequence analysis
indicates that each of the three adult genes is intact and hence may be
functional. Hybridization of one of the two Mus pseudogenes, Hbb-bh3, to
genomic blots from Peromyscus reveals that it has a homologous counterpart
in Peromyscus. Homologous genes to the two gamma-like Mus genes, Hbb-bhO
and Hbb-bhl, are also found in Peromyscus. The strong hybridization between
the Hbb-bhl genes and significant nucleotide similarity between the Hbb-bhO
genes suggest that both pairs are important for the ontogeny of these mice
although no known product has been identified for the Hbb-bhO genes. The
presence of Hbb-bhO and Hbb-bhl in Peromyscus suggests that the duplication
that created this related gene set occurred before the two lineages
diverged. A single gene for Hbb-y has been isolated from Peromyscus. The
adult region in Peromyscus has undergone significant divergence from the
same region in Mus, having three rather than two adult genes, the
acquisition of at least 15 kb of extra DNA relative to Mus, and possibly
the loss of the Hbb-bh2 pseudogene. The nonadult region of the complex, in
contrast, contains the same set of genes apparently distributed over the
same amount of DNA as in the Mus beta- globin complex. This observation
suggests that the embryonic region of the complex is more evolutionarily
stable than the adult region.
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212.
213.
Prostaglandin synthesis by lymphoid tissue of mice experiencing a graft-versus-host reaction: relationship to immunosuppression 总被引:2,自引:0,他引:2
Studies were carried out on the induction of PGE synthesis during the GVH reaction and its role in GVH-induced immunosuppression. The results demonstrated that spleen, lymph node cells and, to a much lesser degree, thymus cells obtained from adult C57BL/6 × AF1 mice treated with 50–75 × 106 C57BL/6 lymphoid cells were stimulated to produce PGE during the course of the GVH reaction. The spleen and lymph node PGE production peaked at Day 9 post-GVH induction (30- and 15-fold higher than normal, respectively). Thereafter, it declined to near normal levels by Days 25–30 post-GVH induction. Passage of GVH spleen cells through a rayon column removed macrophages but not mitogen-responsive T and B cells and also removed nearly all of the PGE-producing cells, except during the later course of the GVH reaction. Removal of PGE-producing cells from GVH-immunosuppressed spleen cells significantly reconstituted the mitogen response to PHA and LPS. Treatment of mice experiencing a GVH reaction with indomethacin delayed the onset of suppression of the plaque-forming cell response to sheep erythrocytes. These results suggest that early GVH-induced immunosuppression which may represent an amplified normal regulatory mechanism is mediated by increased macrophage production of PGE which suppresses both B- and T-cell functions, whereas at later stages other immunosuppressive mechanisms become operational. 相似文献
214.
Previous studies by other investigators have shown that luteinizing hormone releasing hormone (LHRH) and amino acid derivatives of p-nitroanilide are probably degraded by a common enzymatic activity; however, most of these studies are inferential in that they are largely based upon kinetic inhibition data derived from relatively crude tissue preparations. The purpose of this work was to determine whether the synthetic substrate leucine-p- nitroanilide (Leu-p-NA) and LHRH were degraded by the same peptidase activity. Supernatants (10,000 X g) from homogenates of rat hypothalami were eluted from Sephadex G-200, and the resultant fractions were assayed for degrading activity toward LHRH and Leu-p-NA. Radioimmunoassay (RIA) indicated that loss of immunologically active LHRH occurred in the same fractions in which maximal Leu-p-NA degrading activity eluted. Kinetically, exogenous LHRH inhibited degradation of Leu-p-NA in a concentration-dependent manner. When fractions evidencing Leu-p-NA degrading activity were incubated with 125I-LHRH, polyacrylamide gel electrophoresis (PAGE) indicated a time-dependent loss of LHRH with the concomitant production of a radioactive peptide fragment. High-performance liquid chromatography (HPLC) analysis of unlabeled LHRH incubations revealed, within the Leu-p-NA degrading fractions, the formation of two peptide fragments. These studies have further substantiated the likelihood that LHRH and Leu-p-NA are degraded by a common enzyme activity as indicated not only by kinetic inhibition data, but also by cofractionation of activity toward both substrates and by two analytical methods capable of detecting LHRH fragmentation (PAGE and HPLC). 相似文献