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81.
The analysis of the first plant genomes provided unexpected evidence for genome duplication events in species that had previously been considered as true diploids on the basis of their genetics. These polyploidization events may have had important consequences in plant evolution, in particular for species radiation and adaptation and for the modulation of functional capacities. Here we report a high-quality draft of the genome sequence of grapevine (Vitis vinifera) obtained from a highly homozygous genotype. The draft sequence of the grapevine genome is the fourth one produced so far for flowering plants, the second for a woody species and the first for a fruit crop (cultivated for both fruit and beverage). Grapevine was selected because of its important place in the cultural heritage of humanity beginning during the Neolithic period. Several large expansions of gene families with roles in aromatic features are observed. The grapevine genome has not undergone recent genome duplication, thus enabling the discovery of ancestral traits and features of the genetic organization of flowering plants. This analysis reveals the contribution of three ancestral genomes to the grapevine haploid content. This ancestral arrangement is common to many dicotyledonous plants but is absent from the genome of rice, which is a monocotyledon. Furthermore, we explain the chronology of previously described whole-genome duplication events in the evolution of flowering plants.  相似文献   
82.
Astrocytes are a heterogeneous population of cells that are endowed with a great variety of receptors for neurotransmitters and neuromodulators. Recently prostaglandin E2 has attracted great interest since it is not only released by astrocytes but also activates receptors coupled to either phospholipase C or adenylyl cyclase. We report that EP2 receptor stimulation triggers cAMP production but also causes release of Ca2+ from intracellular stores. This effect is shared by other receptors similarly coupled to adenylyl cyclase and elicited by direct stimulation of the enzyme or application of cAMP analogues. However, the stimulation of the Ca2+ response by cAMP is not mediated by protein kinase A, since a specific antagonist of this kinase had no effect. Such a cross-talk between cAMP and Ca2+ was not observed in all astrocytes. It might therefore reflect a specific resource of either a subpopulation or astrocytes in a specific functional state. Received 6 June 2006; received after revision 25 July 2006; accepted 31 August 2006  相似文献   
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Stimulation of certain receptor tyrosine kinases results in the tyrosine phosphorylation and activation of phospholipase C gamma (PLC gamma), an enzyme that catalyses the hydrolysis of phosphatidylinositol (PtdIns). This hydrolysis generates diacylglycerol and free inositol phosphate, which in turn activate protein kinase C and increase intracellular Ca2+, respectively. PLC gamma physically associates with activated receptor tyrosine kinases, suggesting that it is a substrate for direct phosphorylation by these kinases. Here we report that a fibroblast growth factor (FGF) receptor with a single point mutation at residue 766 replacing tyrosine with phenylalanine fails to associate with PLC gamma in response to FGF. This mutant receptor also failed to mediate PtdIns hydrolysis and Ca2+ mobilization after FGF stimulation. However, the mutant receptor phosphorylated itself and several other cellular proteins, and it mediated mitogenesis in response to FGF. These findings show that a point mutation in the FGF receptor selectively eliminates activation of PLC gamma and that neither Ca2+ mobilization nor PtdIns hydrolysis are required for FGF-induced mitogenesis.  相似文献   
86.
In this study, we examined the effect of intracerebroventricular (i.c.v) injection of melatonin and/or ACTH1–10 and ACTH4–10 on [3H]flunitrazepam binding sites in the cerebral cortex of hypophysectomized rats. Hypophysectomy increased the Bmax (maximum number of binding sites) of benzodiazepine (BNZ) receptors for at least 7 days after surgery, without changing KD (dissociation constant). The i.c.v. injection of melatonin to hypophysectomized rats significantly increased Bmax, whereas the same doses of melatonin were ineffective in sham-operated animals. In both cases, KD values were unchanged. The i.c.v injection of ACTH1–10 to hypophysectomized animals significantly increased Bmax, an effect that was enhanced by simultaneous i.c.v. injection of ACTH1–10+melatonin, reaching higher values of Bmax than the i.c.v. injection of these hormones individually. No significant changes in KD values were found after ACTH1–10 and/or melatonin administration. However, the i.c.v. injection of ACTH4–10 to hypophysectomized rats did not change Bmax, although it significantly increased KD values, indicating a decrease in the BNZ binding affinity. Melatonin injection counteracted this effect of ACTH4–10, returning KD to the control value. Moreover, although the lower dose of i.c.v. melatonin used, 10 ng, was unable to modify Bmax of BNZ binding in the ACTH4–10-injected group, the higher dose, 20 ng, significantly increased Bmax. The results suggest that these ACTH-derived peptides can modulate the effect of melatonin on brain benzodiazepine receptors.  相似文献   
87.
This paper publishes the correspondence between S. Germain and C.F. Gauss. The mathematical notes enclosed in her letters are published for the first time. These notes, in which she submitted some of her results, proofs and conjectures to Gauss for his evaluation, were inspired by her study of the Disquisitiones Arithmeticae. The interpretation of these mathematical notes not only shows how deeply she went into Gauss’s treatise and mastered it long before any other mathematician, but also, more importantly, shows that she obtained interesting results in the theory of power residues that have never previously been attributed to her.  相似文献   
88.
Among the heterogeneous population of circulating hematopoietic and endothelial progenitors, we identified a subpopulation of CD133+ cells displaying myogenic properties. Unexpectedly, we observed the expression of the B-cell marker CD20 in blood-derived CD133+ stem cells. The CD20 antigen plays a role in the modulation of intracellular calcium homeostasis through signaling pathways activation. Several observations suggest that an increase in intracellular calcium concentration ([Ca2+]i) could be involved in the etiology of the Duchenne muscular dystrophy (DMD). Here, we show that a CD20-related signaling pathway able to induce an increase in [Ca2+]i is differently activated after brain derived neurotrophic factor (BDNF) stimulation of normal and dystrophic blood-derived CD133+ stem cells, supporting the assumption of a “CD20-related calcium impairment-affecting dystrophic cells. Presented findings represent the starting point toward the expansion of knowledge on pathways involved in the pathology of DMD and in the behavior of dystrophic blood-derived CD133+ stem cells. Received 15 October 2008; received after revision 27 November 2008; accepted 05 December 2008  相似文献   
89.
iASPP is one of the most evolutionarily conserved inhibitors of p53, whereas ASPP1 and ASPP2 are activators of p53. We show here that, in addition to the DNA-binding domain, the ASPP family members also bind to the proline-rich region of p53, which contains the most common p53 polymorphism at codon 72. Furthermore, the ASPP family members, particularly iASPP, bind to and regulate the activity of p53Pro72 more efficiently than that of p53Arg72. Hence, escape from negative regulation by iASPP is a newly identified mechanism by which p53Arg72 activates apoptosis more efficiently than p53Pro72.  相似文献   
90.
Kras is the most frequently mutated ras family member in lung carcinomas, whereas Hras mutations are common in tumors from stratified epithelia such as the skin. Using a Hras knock-in mouse model, we demonstrate that specificity for Kras mutations in lung and Hras mutations in skin tumors is determined by local regulatory elements in the target ras genes. Although the Kras 4A isoform is dispensable for mouse development, it is the most important isoform for lung carcinogenesis in vivo and for the inhibitory effect of wild-type (WT) Kras on the mutant allele. Kras 4A expression is detected in a subpopulation of normal lung epithelial cells, but at very low levels in lung tumors, suggesting that it may not be required for tumor progression. The two Kras isoforms undergo different post-translational modifications; therefore, these findings can have implications for the design of therapeutic strategies for inhibiting oncogenic Kras activity in human cancers.  相似文献   
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