全文获取类型
收费全文 | 853篇 |
免费 | 0篇 |
专业分类
化学工业 | 4篇 |
轻工业 | 2篇 |
无线电 | 1篇 |
一般工业技术 | 5篇 |
冶金工业 | 838篇 |
自动化技术 | 3篇 |
出版年
2018年 | 2篇 |
2011年 | 1篇 |
2010年 | 1篇 |
2008年 | 1篇 |
2003年 | 1篇 |
2000年 | 1篇 |
1999年 | 29篇 |
1998年 | 224篇 |
1997年 | 143篇 |
1996年 | 108篇 |
1995年 | 64篇 |
1994年 | 43篇 |
1993年 | 54篇 |
1992年 | 6篇 |
1991年 | 17篇 |
1990年 | 10篇 |
1989年 | 15篇 |
1988年 | 18篇 |
1987年 | 14篇 |
1986年 | 9篇 |
1985年 | 17篇 |
1983年 | 2篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 13篇 |
1976年 | 47篇 |
排序方式: 共有853条查询结果,搜索用时 15 毫秒
761.
In vivo neuroprotective effects of melatonin on the nigrostriatal dopaminergic system in rats unilateral 6-hydroxydopamine (6-OHDA) lesions were tested. Two weeks after lesioning the dopamine receptor agonist, apomorphine produced rotational asymmetry. In contrast, melatonin treatment significantly reduced the motor deficit following apomorphine challenge. Analysis by tyrosine hydroxylase (TH) immunocytochemistry revealed the loss of cell bodies in the substantia nigra (SN) and absence of terminals in the dorsolateral striatum ipsilaterally. Melatonin treatment also resulted in the survival of dopaminergic neurons in SN and TH-immuoreactive terminals in the dorsolateral striatum. These behavioral and histochemical results may indicate a neuroprotective action of melatonin and suggest a potential pharmacological role in the treatment of Parkinson's disease. 相似文献
762.
CH Bailey BK Kaang M Chen KC Martin CS Lim A Casadio ER Kandel 《Canadian Metallurgical Quarterly》1997,18(6):913-924
The synaptic growth that accompanies 5-HT-induced long-term facilitation of the sensory to motor neuron connection in Aplysia is associated with the internalization of apCAM at the surface membrane of the sensory neuron. We have now used epitope tags to examine the fate of each of the two apCAM isoforms (membrane bound and GPI-linked) and find that only the transmembrane form is internalized. This internalization can be blocked by overexpression of transmembrane constructs with a single point mutation in the two MAPK consensus sites, as well as by injection of a specific MAPK antagonist into sensory neurons. These data suggest MAPK phosphorylation at the membrane is important for the internalization of apCAMs and, thus, may represent an early regulatory step in the growth of new synaptic connections that accompanies long-term facilitation. 相似文献
763.
Phosphorylation of elongation factor 2 (EF-2) by specific Ca2+/calmodulin-dependent kinase is considered as a possible mechanism of regulation of protein biosynthesis in animal cells at the level of polypeptide chain elongation. In this report we show that wheat germ EF-2 can be intensively phosphorylated by the rabbit reticulocyte EF-2 kinase. Phosphorylation results in inhibition of the activity of plant EF-2 in poly(U)-dependent cell-free translation system. Thus, the activity of EF-2 in plant cells can be potentially regulated by phosphorylation. However, we could not detect endogenous EF-2 kinase activity in wheat germ either in vitro or in vivo. Furthermore, EF-2 kinase activity is not displayed in different organs of wheat and other higher plants. 相似文献
764.
765.
CC Silliman D Tedder JW Ogle J Simon BK Kleinschmidt-DeMasters M Manco-Johnson MJ Levin 《Canadian Metallurgical Quarterly》1993,123(3):418-422
Novel techniques have made possible in situ analyses of the lymphocyte populations responding to antigen. In the spleen, antigen-specific T and B cells are first observed in the periarteriolar lymphoid sheath. Following conjugate formation between specific T and B lymphocytes, B-cell proliferation and differentiation takes place in two distinct sites, the periarteriolar lymphoid sheath-associated foci and germinal centers. 相似文献
766.
767.
768.
769.
770.
HB Jie CW Bailey BK Ray DM Estes N Kumar CA Carson 《Canadian Metallurgical Quarterly》1996,83(2):241-246
The glucose-6-phosphate dehydrogenase-encoding gene (G6PD) belongs to a group with constitutive expression in all tissues. The regulation of these housekeeping genes is poorly understood, as compared to what is known about many genes whose expression is restricted to a particular tissue or stage of development, and which are often regulated by locus control regions (LCR) able to act over wide distances. In order to identify sequences in human G6PD which are necessary for its expression, we have generated transgenic mice carrying a 20-kb G6PD construct, including only 2.5 kb of upstream and 2.0 kb of downstream flanking sequence. All mice which carried the transgene (TG) expressed it, and the levels of expression detected in a range of tissues from three independent lines of mice were comparable to that of the endogenous murine G6PD. The variation in enzyme activity from tissue to tissue was remarkably similar for both the TG and the endogenous gene, and was shown to be due in both cases to variations in the steady-state mRNA levels. 相似文献