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51.
Francis L. Marcrina R.Paul Evans Janet Ash Tobian Donna L. Hartley Don B. Clewell Kevin R. Jones 《Gene》1983,25(1):145-150
A novel plasmid vector that is able to replicate both in Escherichia coli and in Streptococcus sanguis is described. This 9.2-kb plasmid, designated pVA856, carries Cmr, Tcr and Emr determinants that are expressed in E. coli. Only the Emr determinant is expressed in S. sanguis. Both the Cmr and the Tcr of pVA856 may be insertionally inactivated. This plasmid affords several different cleavage-ligation strategies for cloning in E. coli followed by subsequent introduction of chimeras in to S. sanguis. In addition, we have modified a previously described E. coli-S. sanguis shuttle plasmid [pVA838; Macrina et al., Gene 19 (1982) 345–353], so that it is unable to replicate in S. sanguis. The utility of such a plasmid for cloning and selecting sequences enabling autonomous replication in S. sanguis is demonstrated. 相似文献
52.
Donna M. Charponiere-Rickenberg Mukta M. Webber 《In vitro cellular & developmental biology. Plant》1983,19(5):373-375
Summary Adult human prostatic epithelium was cultured in a defined medium consisting of RPMI 1640 supplemented with transferrin, insulin,
epidermal growth factor, dexamethasone, and vitamin A. In the presence of insulin, stabilized with zinc, maximum epithelial
multiplication was obtained at an insulin concentration of 0.03 to 0.1 U/ml, corresponding to a zinc concentration of 1.4×10−7
M. At higher insulin concentrations, growth stimulation declined. Zinc-free insulin, on the other hand, stimulated cell multiplication
with an optimum concentration of 0.3 to 1.0 U/ml. At this concentration the maximum growth was twice that obtained with zinc-stabilized
insulin. Results demonstrate that growth inhibition caused by zinc limits the concentration of zinc-stabilized insulin, which
can be used in serum-free, defined culture media.
This work was supported by the Division of Cancer Cause and Prevention, National Cancer Institute, DHHS Grant No. CA-28279
to Webber. 相似文献
53.
The uptake of morphine was significantly reduced in most regions of the brains of conscious, unrestrained rats within 10 minutes after treatment with an analog of ACTH/MSH (4–9), ORG-2766. The effect was most obvious in regions with significant densities of enkephalin receptors, namely basal ganglia, hippocampus and cortex. The results explain, in part, how some fragments and analogs of ACTH/MSH may antagonize behavioral actions of morphine, even though some of these peptides lack significant opiate receptor binding properties. We believe that this effect of ORG-2766 is related to an action on the permeability characteristics of the brain microvasculature. The underlying mechanism is unknown. 相似文献
54.
Restrictive control (“repression”) of 3-O-methylglucose transport (or of galactose uptake) in confluent NIL hamster fibroblast cultures was found to be highly pronounced after preconditioning the cultures in medium containing d-glucosamine. The “repression” exerted by glucosamine developed slowly over several hours. The transport “repression” was counteracted by anaerobiosis, by 2,4-dinitrophenol (H. M. Kalckar, C. W. Christopher, and D. Ullrey, 1979, Proc. Nat. Acad. Sci. USA76, 6453–6455), and by fluoride as well as by malonate. In “de-repressed” cultures, i.e., in the absence of glucosamine in the medium or by using fructose during preconditioning, malonate did not affect regulation of the hexose transport system. In culture medium deprived of l-glutamine and serum, repressive control of the transport system by glucose as well as by glucosamine was greatly aggravated. However, the simultaneous addition of malonate abolished the severe “repression” by either of the hexoses. In all cases, preconditioning with fructose permitted high (“de-repressed”) transport activity. Unlike glucose, galactose, or glucosamine, fructose was not found to compete in the transport assay. The metabolic inhibitors which prevent the aerobic curtailment of the hexose transport system are all more or less directly interfering with the flow of metabolites through the tricarboxylate cycle, which may therefore play an important role in the “repressive” control of transport. 相似文献
55.
Francine C. Eden Anna Maria Musti Donna A. Sobieski 《Journal of molecular biology》1981,148(2):129-151
In the chicken genome there are middle repetitive DNA sequences with a clustered organization. Each cluster is composed of members of different families of repeated DNA sequences and usually contains only one member of each family. Many clusters have the same assortment of repeated sequences but they are in scrambled order from cluster to cluster. These clusters usually exceed 20 × 103 bases in length and comprise at least 10% of the repeated DNA of the chicken. The repeated sequences that are cluster components are extensively methylated. Methylation was detected by comparing HpaII and MspI digests of total DNA, where the occurrence of the sequence C-m5C-G-G is indicated when HpaII (cleaves C-C-G-G) fragments are larger than those generated by MspI (cleaves C-m5C-G-G or C-C-G-G). In hybridization experiments with Southern (1975) blots of total DNA digested with either HpaII or MspI, the cloned probes representing clustered repeated sequences showed a dramatic difference in the lengths of restriction fragments detected in the two digests. Many of the sequences that comprise these clusters are methylated in most of their genomic occurrences. There are patterns of methylation that are reproduced faithfully from copy to copy. The overall distribution of methylation within clusters seems to be regional, with long methylated DNA segments interrupted by specific undermethylated regions. 相似文献
56.
Population Ecology - Female deermice housed from weaning with groups of five females, five males or five males plus five females had significantly smaller uteri at 35–38 days of age compared... 相似文献
57.
Surface staining of the intact vascular endothelial cell layer lining the lumen of guinea pig thoracic aorta with antibodies to vimentin revealed that at least 70% of the cells contained intact perinuclear rings of 10-nm filaments. This correlated with the observations made on these cells in culture: 60–80% of the endothelial cells at confluence have complete perinuclear rings. By one- and two-dimensional gel electrophoresis and immunoprecipitation we confirmed that vimentin [17, 18] is the major constituent polypeptide of the 10-nm filaments in guinea pig endothelial cells. These results indicate that the vimentin [17] 10-nm filament cytoskeleton found in guinea pig endothelial cells in vitro is similar to the cytoskeleton found in situ. 相似文献
58.
59.
Cora E. Lewis John P. Bantle Alain G. Bertoni George Blackburn Frederick L. Brancati George A. Bray Lawrence J. Cheskin Jeffrey M. Curtis Caitlin Egan Mary Evans John P. Foreyt Siran Ghazarian Bethany Barone Gibbs Stephen P. Glasser Edward W. Gregg Helen P. Hazuda Louise Hesson James O. Hill Edward S. Horton Van S. Hubbard John M. Jakicic Robert W. Jeffery Karen C. Johnson Steven E. Kahn Abbas E. Kitabchi Dalane Kitzman William C. Knowler Edward Lipkin Sara Michaels Maria G. Montez David M. Nathan Ebenezer Nyenwe Jennifer Patricio Anne Peters Xavier Pi‐Sunyer Henry Pownall David M. Reboussin Donna H. Ryan Thomas A. Wadden Lynne E. Wagenknecht Holly Wyatt Rena R. Wing Susan Z. Yanovski 《Obesity (Silver Spring, Md.)》2020,28(2):247-258
60.