全文获取类型
收费全文 | 4098篇 |
免费 | 483篇 |
出版年
2021年 | 40篇 |
2019年 | 39篇 |
2018年 | 48篇 |
2016年 | 64篇 |
2015年 | 106篇 |
2014年 | 133篇 |
2013年 | 155篇 |
2012年 | 171篇 |
2011年 | 184篇 |
2010年 | 112篇 |
2009年 | 87篇 |
2008年 | 168篇 |
2007年 | 153篇 |
2006年 | 130篇 |
2005年 | 131篇 |
2004年 | 120篇 |
2003年 | 108篇 |
2002年 | 126篇 |
2001年 | 119篇 |
2000年 | 144篇 |
1999年 | 113篇 |
1998年 | 58篇 |
1997年 | 47篇 |
1996年 | 50篇 |
1995年 | 45篇 |
1994年 | 44篇 |
1993年 | 36篇 |
1992年 | 77篇 |
1991年 | 82篇 |
1990年 | 93篇 |
1989年 | 94篇 |
1988年 | 75篇 |
1987年 | 86篇 |
1986年 | 71篇 |
1985年 | 86篇 |
1984年 | 66篇 |
1983年 | 53篇 |
1982年 | 48篇 |
1981年 | 46篇 |
1979年 | 57篇 |
1978年 | 50篇 |
1977年 | 46篇 |
1976年 | 45篇 |
1975年 | 57篇 |
1974年 | 38篇 |
1973年 | 55篇 |
1972年 | 66篇 |
1971年 | 43篇 |
1970年 | 50篇 |
1969年 | 41篇 |
排序方式: 共有4581条查询结果,搜索用时 312 毫秒
941.
The destruction of cytochrome P-450 by allylisopropylacetamide (2-isopropyl-4-pentenamide) in microsomes from phenobarbital-pretreated rats has been shown to require oxygen, to be inhibited by NADP through inhibition of cytochrome P-450 reductase, and to be slightly stimulated by NADH. Glutathione (1 mm) does not inhibit destruction, but methyl 4,5-epoxy-2-isopropylpentanoate (5 mm), an analog of the epoxide of allylisopropylacetamide, does. The inactivation of cytochrome P-450 is both time dependent and saturable, although no more than approximately 40% of the microsomal enzyme appears to be normally destructible. However, mechanical perturbation of the microsomal suspension by rehomogenization initiates renewed destruction. Kinetic analysis shows that the destructive process is pseudo-first-order, with an apparent inactivation rate constant of 1.4 × 10?3 s?1 and an apparent Km of 1.14 mm. Approximately 230 molecules of substrate are turned over for each destructive event. These results, in conjunction with previously reported data, clearly and unambiguously establish that inactivation of cytochrome P-450 by allylisopropylacetamide is a suicidal process. 相似文献
942.
Harry G. Rittenhouse Edward B. Seguin Stephen K. Fisher Bernard W. Agranoff 《Journal of neurochemistry》1981,36(3):991-999
Enzymatic hydrolysis of the pyrophosphate bond of CDP-diglyceride (CDP-DG), previously shown to occur in bacteria, is demonstrable in mammalian tissues. Activity was enriched in a lysosomal fraction obtained from guinea pig cerebral cortex and was purified 92-fold relative to the homogenate by a combination of XM-300 ultrafiltration and DEAE-cellulose column chromatography. When incubated with CDP-dipalmitin, the purified enzyme produced stoichiometric amounts of CMP and phosphatidate. dCDP-DG served as a substrate, while ADP-DG was an inhibitor, as were 5'-AMP and 5'-dAMP. CDP-DG hydrolysis was not affected by the presence of excess amounts of CDP-choline, CDP-glycerol, sodium pyrophosphate, or cyclic 3',5'-AMP. 相似文献
943.
Michael Steinmetz John G. Frelinger Douglas Fisher Tim Hunkapiller Dennis Pereira Sherman M. Weissman Hiroshi Uehara Stanley Nathenson Leroy Hood 《Cell》1981,24(1):125-134
We constructed cDNA libraries from poly(A)+ RNA isolated from cell lines of two different inbred strains of mice, and screened the libraries with a cDNA clone encoding a human transplantation antigen. Three cDNA clones were identified, sequenced and found to encode amino acid sequences highly homologous to portions of a known mouse transplantation antigen. Comparison of the cDNA sequences of mouse transplantation antigens with the constant region domains of the mouse immunoglobulin μ gene reveals a striking homology, which suggests that the two genes share a common ancestor. Antibody genes undergo DNA rearrangements during B cell differentiation that are correlated with their expression. In contrast, DNA blots with these cDNA probes suggest that the genes for the transplantation antigens are not rearranged in the genomes of liver or embryo cells, which express these antigens, as compared with sperm cells, which do not express these antigens. In Bam HI-digested liver DNAs from different inbred strains of mice, 10–15 bands of hybridization were found. Accordingly, the genes encoding the transplantation antigens appear to constitute a multigene family with similar gene numbers in different mice. 相似文献
944.
945.
Protein staining of ribboned epon sections for light microscopy 总被引:19,自引:0,他引:19
Donald B. Fisher 《Histochemistry and cell biology》1968,16(1):92-96
Summary Procedures are described for obtaining and handling ribboned epon sections 0.3–2 thick for light microscopy, and for the cytological application of two intense acid dyes, Aniline Blue Black and Coomassie Brilliant Blue R 250. The technique allows precise localization of proteins and some other materials, and, because the sections are ribboned, facilitates three-dimensional visualization of the structures involved. The dyes may be used in combination with the periodic acid-Schiff reaction and with autoradiography.This work was supported in part by a Public Health Service fellowship 5-F2-GM-22, 031-02 to the author and in part by NSF grant GB 3460 to Dr. W. A. Jensen. 相似文献
946.
947.
948.
949.
Otto T. Solbrig John Skok David French John W. Thieret Kling L. Anderson M. T. Hilborn John Popenoe Floyd Swink George L. Mcnew Ray Schulenberg William L. Stern William G. Walter T. W. Fisher C. Earle Smith Wynne Thoene Anna P. Kummer Hugh Cutler Alexander H. Smith Henry T. Skinner Joseph H. Caro Harold F. Madsen L. W. R. Jackson Lawrence Kaplan Duane Isely Alphons Th. Czaja Willard A. Taber 《Economic botany》1961,15(2):180-204
950.