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排序方式: 共有386条查询结果,搜索用时 15 毫秒
1.
K Curry D S Magnuson H McLennan M J Peet 《Canadian journal of physiology and pharmacology》1987,65(11):2196-2201
Intracellular recordings were obtained from rat hippocampal neurons during the microiontophoretic ejection of the stereoisomers of cis- and trans-1-amino-1,3-cyclopentane dicarboxylate into the dendritic region (stratum radiatum) of the impaled cells. L-(+)-cis-1-Amino-1,3-cyclopentane dicarboxylate, D(+)-trans-1-amino-1,3-cyclopentane dicarboxylate, and L-(-)-trans-1-amino-1,3-cyclopentane dicarboxylate all evoked patterns of excitation resembling that elicited by kainate. All of these responses were unaffected by D-(-)-2-amino-5-phosphonovalerate but were antagonized at comparable currents by kynurenate. The excitation produced by D-(-)-cis-1-amino-1,3-cyclopentane dicarboxylate was similar to that evoked by N-methyl-D-aspartate. At low ejection currents a slow depolarization triggered rhythmic burst firing, each burst consisting of a depolarizing shift in membrane potential upon which were superimposed four to five action potentials. These responses were antagonized both by D-(-)-2-amino-5-phosphonovalerate and by kynurenate. The results are discussed with respect to the conformational requirements considered to be necessary for interaction at the kainate and N-methyl-D-aspartate receptors on CA1 pyramidal neurones. It is important to note that the isopropylene side chain of kainate is absent from the 1-amino-1-3-cyclopentane dicarboxylate molecule. 相似文献
2.
Identification of basal and cyclic AMP regulatory elements in the promoter of the phosphoenolpyruvate carboxykinase gene. 总被引:29,自引:16,他引:13 下载免费PDF全文
P G Quinn T W Wong M A Magnuson J B Shabb D K Granner 《Molecular and cellular biology》1988,8(8):3467-3475
Promoter elements important for basal and cyclic AMP (cAMP)-regulated expression of the phosphoenolpyruvate carboxykinase (PEPCK) gene have been identified by analysis of a series of PEPCK promoter mutations in transfection experiments. Fusion genes containing wild-type and mutated PEPCK promoter sequences from -600 to +69 base pairs (bp) fused to the coding sequence for chloramphenicol acetyltransferase were studied. Internal deletion mutations that replaced specific bases with a 10-bp linker within the region from -129 bp to -18 bp of the PEPCK promoter were examined. In addition, wild-type and mutated DNA templates were used as probes in DNase I protection experiments to determine sites of protein-DNA interaction. The PEPCK promoter contains a binding site for nuclear factor 1-CAAT. Deletion of the 5' end of this binding site reduced the size of the DNase I footprint in this region but had no effect on promoter activity. In contrast, deletion or disruption of the 3' end of this binding site completely eliminated protein binding and reduced promoter activity by 50%. Deletion of core sequences of the cAMP regulatory element (CRE) resulted in loss of cAMP responsiveness and an 85% decrease in basal promoter activity, indicating that the CRE also functions as a basal stimulatory element. Mutation of the core sequence of the CRE resulted in loss of the DNase I footprint over the CRE. Internal deletions flanking the CRE showed no loss of induction by cAMP but did have reduced promoter activity. This delimits the CRE to an 18-bp region between nucleotides -100 and -82. Analysis of mutations that disrupted bases between the CRE and the initiation site identified a basal inhibitory element adjacent to a basal stimulatory element, both located just 3' of the CRE, as well as a basal stimulatory element coincident with the TATA consensus sequence centered at -27. These data demonstrate that several cis-acting elements are located within 130 nucleotides of the initiation site of the PEPCK gene and that the CRE is essential for both basal promoter activity and cAMP-regulated expression of this gene. 相似文献
3.
Shyam K. Sharan Bernadette Holdener-Kenny David W. Threadgill Terry Magnuson 《Mammalian genome》1992,3(2):79-83
Sensitive methods for analysis of DNA from limited amounts of tissue are often difficult, error prone, and time consuming. Here, we describe a procedure for molecular analysis of individual early post-implantation mouse embryos by Southern analysis. The procedure involves embedding single embryos in agarose before lysing and deproteinizing in situ. The embedded DNA can be digested with restriction enzymes and analyzed by standard Southern-blotting procedures. The procedure is sensitive enough to detect single-copy sequences in embryos as early as day 6.5 of development. We have used the technique to genotype embryos homozygous for an embryonic lethal deletion. Normally, the lethal phenotype associated with such mutations is identified by a retrospective statistical analysis of abnormal embryos produced from a heterozygous cross as compared to those produced from a control cross. Now, if associated with a detectable DNA abnormality, the mutant embryo can be genotyped directly. We also report the use of this method for mapping cloned markers relative to deletion breakpoints. This approach can save considerable time since mapping would conventionally be done using restriction fragment length polymorphisms (RFLPs) detected in Mus musculus/Mus spretus interspecies hybrids. Using this procedure, we have been able to redefine the distal limits of the region of Chromosome (Chr) 7 containing a gene (eed) needed for development of the embryonic ectoderm. 相似文献
4.
Eugene M. Rinchik Terry Magnuson Bernadette Holdener-Kenny Gavin Kelsey Albert Bianchi Claudio J. Conti Fran?ois Chartier Kathryn A. Brown Stephen D. M. Brown Josephine Peters 《Mammalian genome》1992,3(Z1):S104-S120
Chair of Committee for Mouse Chromosome 7 相似文献
5.
M J Peet K Curry D S Magnuson H McLennan 《Canadian journal of physiology and pharmacology》1986,64(2):163-168
The excitatory effects of microiontophoretically applied quisqualic (QUIS), N-methyl-D-aspartic (NMDA), and quinolinic (QUIN) acids were investigated using intracellular recording from CAl pyramidal neurones in slices of rat hippocampus. QUIS evoked only simple action potentials superimposed upon a depolarization which attained a clear plateau. When this level had been reached, increased ejecting currents did not produce further depolarization. By contrast, with low currents NMDA and QUIN elicited small membrane depolarizations which triggered bursts of action potentials superimposed upon rhythmically occurring depolarizing shifts. Larger currents caused depolarization which if sufficiently large completely blocked spike activity. Tetrodotoxin (TTX) prevented the spikes evoked by QUIS and the bursts of action potentials seen with NMDA and QUIN, and the rhythmic depolarizing shifts then appeared as broad spikes of up to 50 mV in amplitude. These and the underlying membrane depolarization were blocked by Co2+, by the NMDA antagonist D(-)-2-amino-5-phosphonovaleric acid (DAPV), and by kynurenic acid (KYNU). It thus appears that the depolarization and burst firing of rat CAl pyramidal neurones elicited by NMDA and QUIN are Ca2+ dependent while the actions of QUIS are not. 相似文献
6.
N S Magnuson L E Perryman C R Wyatt T Ishizaka P H Mason A E Namen K L Banks J A Magnuson 《Journal of immunology (Baltimore, Md. : 1950)》1984,133(5):2518-2524
Peripheral blood mononuclear cells (PBMC) from 14 foals with hereditary severe combined immunodeficiency (SCID) were studied to determine the extent of lymphocyte differentiation that occurs in this disorder. PBMC from all 14 horses had the morphologic characteristics of large granular lymphocytes (LGL). Cells from only one of 14 horses were responsive to phytolectin stimulation in a standard blastogenesis assay; however, PBMC from all 14 horses proliferated in continuous culture in the presence of partially purified interleukin 2. Furthermore, there were differences in the growth patterns of these cultured cells that correlated with their ability to respond to phytolectin stimulation. PBMC obtained from the 13 phytolectin-unresponsive foals survived in culture for only 4 to 5 wk, divided very slowly, developed large granules composed primarily of calcium phosphate, and accumulated high concentrations of histamine. In contrast, PBMC from the phytolectin-responsive SCID foal proliferated in continuous culture for over 100 days, divided as rapidly as normal equine PBMC under identical culture conditions, and did not accumulate granules or histamine. These observations indicate that lymphoid cell differentiation occurs in some horses with SCID even though the identity of the LGL is unresolved. Two possibilities are that LGL are products of a pathway separate from that of lymphocytes or that LGL are precursors of mature lymphocytes. 相似文献
7.
J. A. Magnuson E. R. Pandolfino G. R. Munske A. E. Namen M. S. Nissen 《Journal of biosciences》1983,5(1):83-91
Two lectins, a tetramer designated LBL4 and an octamer LBL8 designated have been purified from the lima beanPhaseolus lunatus. The tetramer appears to be nonmitogenic for human lymphocytes and is a weak mitogen for bovine cells. The octamer and a chemically cross-linked form of the tetramer are good mitogens. The lima bean lectin binds to only certain sub-populations of human lymphocytes. The primary class which does not bind appears to be a sub-population ofT-lymphocytes. Comparisons of cell binding with other lectins which bind to 2-acetamido-2-deoxy-D-galactose have been carried out. Quantitative analysis of the binding to human erythrocytes is co-operative but binding to lymphocytes is non-co-operative. These results show that there may not be a direct correlation between mitogenic stimulation and cooperative binding to membrane receptors. 相似文献
8.
9.
Comparison of extracellular peroxidase- and esterase-deficient mutants of Streptomyces viridosporus T7A. 总被引:3,自引:0,他引:3 下载免费PDF全文
Peroxidase-deficient mutants of the lignin-degrading bacterium Streptomyces viridosporus T7A were screened for their production of acid-precipitable polymeric lignin, extracellular peroxidases and esterases, and immunoreactivities against a polyclonal antibody produced against electrophoretically purified peroxidase isoform P3 of wild-type S. viridosporus. The mutants showed diminished abilities to solubilize lignin and produce acid-precipitable polymeric lignin. Their peroxidase activities were decreased, and their esterase production patterns were altered. Western immunoblots demonstrated that the mutants produced proteins immunologically reactive with the antibody, but with different mobilities from those of wild-type proteins. These findings confirm a direct role for peroxidases in lignin solubilization. They also indicate a possible role for esterases. 相似文献
10.
Raju Rajala V. S. Magnuson Bernadene A. Sharma Rajendra K. 《Molecular and cellular biochemistry》1995,149(1):191-202
Myristoyl CoA:Protein N-myristoyltransferase (NMT) is the enzyme which catalyses the covalent transfer of myristate from myristoyl CoA to the amino-terminal glycine residue of protein substrates. Although NMT is ubiquitous in eukaryotic cells, the enzyme levels and cellular distribution vary among tissues. In this article, we describe the properties of mammalian NMT(s) with reference to subcellular distribution, molecular weights, substrate specificity and the possible involvement of NMT in pathological processes. The cytosolic fraction of bovine brain contains multiple forms of NMT activity whereas bovine spleen contains only a single form. In bovine brain and spleen, the cytosol contained majority of NMT activity. In contrast, rabbit colon and rat liver NMT activity was predominantly particulate. Regional differences in NMT activity have been observed in both rabbit intestine and bovine brain. Results from our laboratory along with the existing knowledge, provide evidence for the existence of tissue specific isozymes of NMT. 相似文献