全文获取类型
收费全文 | 487篇 |
免费 | 20篇 |
出版年
2022年 | 5篇 |
2021年 | 8篇 |
2020年 | 4篇 |
2019年 | 10篇 |
2018年 | 9篇 |
2017年 | 10篇 |
2016年 | 5篇 |
2015年 | 15篇 |
2014年 | 21篇 |
2013年 | 32篇 |
2012年 | 35篇 |
2011年 | 36篇 |
2010年 | 21篇 |
2009年 | 15篇 |
2008年 | 25篇 |
2007年 | 20篇 |
2006年 | 19篇 |
2005年 | 42篇 |
2004年 | 12篇 |
2003年 | 26篇 |
2002年 | 12篇 |
2001年 | 6篇 |
2000年 | 8篇 |
1999年 | 6篇 |
1998年 | 5篇 |
1997年 | 4篇 |
1996年 | 8篇 |
1995年 | 4篇 |
1994年 | 9篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 11篇 |
1989年 | 4篇 |
1987年 | 3篇 |
1986年 | 6篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1978年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1971年 | 2篇 |
1969年 | 1篇 |
1968年 | 3篇 |
1966年 | 1篇 |
1965年 | 2篇 |
排序方式: 共有507条查询结果,搜索用时 265 毫秒
1.
The assembly of a large physical map of genomes requires simultaneous analysis of many cosmid clones for overlapping regions. The search for overlapping regions may be achieved by various means. High-performance liquid chromatography (HPLC) provides an alternative to gel electrophoresis since microgram amounts of each DNA fragment may be collected into individual test tubes for further analysis. HPLC has been used to identify overlapping cosmid clones from a pool of cosmid DNA containing the terminal portion of the long arm of the human X chromosome (Xq24-qter). Among 400 cosmids analyzed, 3 were shown to overlap. 相似文献
2.
Pertussis Toxin Attenuates D2 Inhibition and Enhances D1 Stimulation of Adenylate Cyclase by Dopamine in Rat Striatum 总被引:2,自引:1,他引:1
The response of adenylate cyclase to GTP and to dopamine (DA) was investigated in synaptic plasma membranes isolated from rat striatum injected with pertussis toxin, which inactivates the inhibitory guanine nucleotide-binding regulatory protein (Ni) of adenylate cyclase. Pertussis toxin treatment reverted the inhibitory effects on the enzyme activity elicited by micromolar concentrations of GTP and reduced by 50% the DA inhibition of cyclase activity via D2 receptors. The toxin treatment enhanced the net stimulation of enzyme activity by DA in the presence of micromolar concentrations of GTP. However, the stimulatory effect of the selective D1 receptor agonist SKF 38393 was not significantly affected. The data indicate that Ni mediates D2 inhibition of striatal adenylate cyclase and participates in the modulation of D1 stimulation of the enzyme activity by DA. 相似文献
3.
Summary
1H-NMR spectra of bovine pancreatic trypsin inhibitor (BPTI) both native and oxidized by chloramine T, are reported. The spectrum of the oxidized form is characterized by the appearance of two singlets for methyl group shifted 0.60 and 0.46 ppm downfield with respect to the native form. 相似文献
4.
5.
Acetylcholine stimulates phosphatidylinositol turnover at nicotinic receptors of cultured myotubes 总被引:4,自引:0,他引:4
Acetylcholine treatment of [3H]inositol pre-labelled cultured chick embryo myotubes results in the stimulation of phosphatidylinositol breakdown, as shown by the measurement of inositol-1-phosphate accumulating in the presence of lithium. The described effect is dependent on agonist concentration and incubation time, and is inhibited by tubocurarine and alpha-bungarotoxin. The activation of phosphatidylinositol breakdown by acetylcholine at extrajunctional nicotinic receptors is likely to be involved in the modulation of the functional activity of the receptor. 相似文献
6.
Maria C. Olianas Pierluigi Onali Norton H. Neff Erminio Costa 《Journal of neurochemistry》1983,41(5):1364-1369
We investigated the effect of acetylcholine (ACh) on the activation of adenylate cyclase by dopamine (DA) in a lysed synaptosomal preparation from rat striatum. ACh reduced both basal and the DA-activated adenylate cyclase with an apparent IC50 of approximately 1 microM. From a kinetic analysis it appeared that ACh reduced the Vmax for activation by DA but not the activation constant for DA. For most preparations the Vmax was reduced by 30-40%. The presence of atropine did not affect the activation of the enzyme by DA but it blocked the inhibition by ACh. Following 6-hydroxydopamine lesion of the nigrostriatal pathway, the enzyme became supersensitive to activation by DA and also more sensitive to inhibition by ACh. Inhibition of adenylate cyclase by ACh appeared to be rather specific for activation by DA, as ACh had no effect on activation of adenylate cyclase by the adenosine analogue N6-(L-2-phenylisopropyl)adenosine. These results indicate that some striatal muscarinic and dopaminergic receptors are probably coupled to the same adenylate cyclase domain. Moreover, they suggest a biochemical model for the dynamic balance of cholinergic and dopaminergic neurons that innervate the striatum. 相似文献
7.
A volunteer was immunized by planned blood transfusions from an LA and FOUR incompatible donor. Among the several antibodies produced, an antibody population was found that cross-reacts with both LA and FOUR antigens; both these crossreacting determinants were present in the immunizing donor. Monospecificity of the antibody has been proven by adsorptions and elutions. Resistance to lysis experiments excluded the possibility that this antibody does not react against LA and FOUR, but reacts instead against an antigen belonging to another independentHL-A locus with alleles in strong linkage disequilibrium withLA andFOUR alleles. The following hypotheses are therefore formulated: a)LA andFOUR factors have structural analogies; b) LA and FOUR molecules lie in close proximity on the cell surface so that the appearance of a “hybrid” antigenic determinant becomes possible. 相似文献
8.
9.
10.
Maurizio Grimaldi Giacomo Pozzoli Pierluigi Navarra Paolo Preziosi Gennaro Schettini 《Journal of neurochemistry》1994,63(1):344-350
Abstract: In this study we analyzed the involvement of the cyclic AMP (cAMP)-protein kinase A system in the regulation of interleukin 6 production by cultured cortical astrocytes. Vasoactive intestinal peptide strongly increased, in a dose-dependent manner, interleukin 6 production. This effect was reduced when protein kinase A was blocked by KT-5720; it was not affected by calphostin C, a protein kinase C inhibitor. Forskolin caused a concentration-dependent increase in interleukin 6 release that was also inhibited by KT-5720. Because prostaglandins are believed to play a role in interleukin 6 production, we tried to determine whether the stimulatory effects of vasoactive intestinal peptide and forskolin on cytokine release might be mediated by stimulation of prostaglandin production in cortical astrocytes. Vasoactive intestinal peptide did not increase the production of either prostaglandin E2 or F2α. Conversely, forskolin concentration-dependently stimulated the production of both prostaglandins, an effect that was blocked by indomethacin. Indomethacin did not affect either vasoactive intestinal peptide- or forskolin-stimulated interleukin 6 production. To exclude the possibility that prostaglandins participate in interleukin 6 production induced by forskolin, we tested prostaglandins E2 and F2α. The former was completely ineffective in eliciting the cytokine production, whereas prostaglandin F2α slightly increased interleukin 6 production only at the highest concentrations. 8-Bromo-cAMP and dibutyryl-cAMP stimulated interleukin 6 production to a lesser extent than vasoactive intestinal peptide and forskolin. In conclusion, we provide evidence that vasoactive intestinal peptide increases interleukin 6 production by astrocytes through the stimulation of the cAMP-protein kinase A pathway, an effect that is reproduced by cAMP analogues. In addition, we point out that prostaglandins are not involved in vasoactive intestinal peptide- and forskolin-mediated induction of interleukin 6 production in cultured astrocytes. 相似文献