全文获取类型
收费全文 | 2382篇 |
免费 | 115篇 |
出版年
2022年 | 11篇 |
2021年 | 9篇 |
2020年 | 6篇 |
2019年 | 17篇 |
2018年 | 32篇 |
2017年 | 23篇 |
2016年 | 41篇 |
2015年 | 66篇 |
2014年 | 89篇 |
2013年 | 153篇 |
2012年 | 180篇 |
2011年 | 153篇 |
2010年 | 113篇 |
2009年 | 85篇 |
2008年 | 154篇 |
2007年 | 149篇 |
2006年 | 149篇 |
2005年 | 164篇 |
2004年 | 139篇 |
2003年 | 141篇 |
2002年 | 146篇 |
2001年 | 20篇 |
2000年 | 18篇 |
1999年 | 23篇 |
1998年 | 37篇 |
1997年 | 48篇 |
1996年 | 22篇 |
1995年 | 25篇 |
1994年 | 10篇 |
1993年 | 20篇 |
1992年 | 15篇 |
1991年 | 24篇 |
1990年 | 16篇 |
1989年 | 16篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 14篇 |
1985年 | 15篇 |
1984年 | 15篇 |
1983年 | 8篇 |
1982年 | 20篇 |
1981年 | 20篇 |
1980年 | 16篇 |
1979年 | 13篇 |
1978年 | 10篇 |
1977年 | 6篇 |
1976年 | 10篇 |
1975年 | 5篇 |
1973年 | 5篇 |
1971年 | 4篇 |
排序方式: 共有2497条查询结果,搜索用时 15 毫秒
21.
Protein Kinases Are Involved in Prolonged Acetylcholine Release from Rat Hippocampus Induced by Thyrotropin-Releasing Hormone Analogue NS-3 总被引:2,自引:0,他引:2
Michiko Oka Yoshinori Itoh Yojiro Ukai Yoshiaki Yoshikuni Kiyoshi Kimura 《Journal of neurochemistry》1996,66(5):1889-1893
Abstract: The effects of various protein kinase inhibitors on acetylcholine release from the rat hippocampus induced by the local application of NS-3 (montirelin hydrate, CG-3703), a thyrotropin-releasing hormone analogue, into the medial septum-diagonal band were examined using in vivo microdialysis. Perfusion of NS-3 (1 µ M ) into the medial septum-diagonal band for 20 min produced a pronounced and prolonged increase in the hippocampal acetylcholine efflux. Pretreatment of the medial septum-diagonal band with either K-252a, a nonselective protein kinase inhibitor, or selective protein kinase A inhibitor H-89 almost completely blocked the acetylcholine efflux evoked by NS-3, and selective protein kinase C inhibitor calphostin C inhibited the action of NS-3. On the other hand, NS-3 (0.1–10 µ M ) or TRH (1–100 µ M ) increased the cyclic AMP efflux from the medial septum-diagonal band in a concentration-dependent manner, as measured by microdialysis. These findings suggest that protein kinases A and C in the neurons of the medial septum-diagonal band are involved in the mechanism of the prolonged stimulation of acetylcholine release from the hippocampus induced by thyrotropin-releasing hormone and its analogue, NS-3. 相似文献
22.
Ahmed S. Rahman Mieko Kimura Katsuhiko Yokoi Tanvir-E Naher Yoshinori Itokawa 《Biological trace element research》1996,53(1-3):57-64
Three groups of rats were fed two types of synthetic diets for 52 d. The—A group was allowed free access to a vitamin A-deficient
diet and showed classical signs of vitamin A deficiency. The brain was the only organ in our experiment where no significant
weight difference was present among the three groups. In the brain, calcium concentration was significantly higher in the—A
group when compared with the PF (Pair-fed; allowed restricted amount of control diet) and +A groups (allowed free access to
control diet). In the tibia, calcium and magnesium concentrations were significantly lower in the—A group when compared with
other two groups. Excessive accumulation of calcium in brain and apparently similar unbalance in bone, mineral concentration
were observed in central nervous system (CNS) degenerative diseases. Our results suggest that abnormal metabolism of calcium
and magnesium in some tissues and excessive accumulation of calcium in brain may be responsible for the development of neurological
disorders in vitamin A-deficient rats. 相似文献
23.
Twenty-four weanling male Wistar rats were divided into four groups fed diets containing adequate or deficient levels of selenium
(0.5 ppm [+ Se] or <0.02 ppm [−Se] and protein (15% [+Pro] or 5% [−Pro]), but adequate levels of all other nutrients for 4
wk to determine the effects of Se deficiency and protein deficiency on tissue Se and glutathione peroxidase (GSHPx) activity
in rats. Plasma, heart, liver, and kidney Se and GSHPx were significantly lower in Se-deficient groups in relation to Se-sufficient
groups. In Se-deficient groups, Se and GSHPx were significantly higher in −Se−Pro rats in heart, liver, and kidney. Data analysis
showed that there were significant interaction effects between dietary Se and protein on Se and GSHPx of rats. It is assumed
that under the condition of Se deficiency. a low level of protein may decrease Se and GSHPx utilization, increase GSHPx synthesis,
and result in Se redistribution. This could account for high levels of Se and GSHPx in the −Se−Pro rats compared to −Se+Pro
rats. 相似文献
24.
Presynaptic α2 Adrenoceptors Inhibit Glutamate Release from Rat Spinal Cord Synaptosomes 总被引:1,自引:0,他引:1
Yoshinori Kamisaki Toshihiro Hamada Kazuhisa Maeda Masahiko Ishimura Tadao Itoh 《Journal of neurochemistry》1993,60(2):522-526
Abstract: The presynaptic regulation of amino acid release from nerve terminals was investigated using synaptosomes prepared from the rat spinal cord. The basal releases of endogenous glutamate (Glu), aspartate (Asp), and γ-amino-butyric acid (GABA) were 34.6, 21.5, and 10.0 pmol/min/mg of protein, respectively. Exposure to a depolarizing concentration of KCl (30 m M ) evoked 2.7-, 1.5-, and 2.9-fold increases in Glu, Asp, and GABA release, respectively. Clonidine reduced the K+ -evoked overflow of Glu to 56% of the control overflow with a potency (IC50 ) of 17 n M , but it did not affect K+ -evoked overflow of Asp, GABA, and their basal releases. Similarly, noradrenaline inhibited the K+ -evoked overflow of Glu, although phenylephrine and isoproterenol showed no effect. The inhibitory effect of clonidine was counteracted by α2 -adrenoceptor antagonists, rauwolscine, yohimbine, and idazoxan, regardless of the imidazoline structures. Because Glu is considered a neurotransmitter of primary afferents that transmit both nociceptive and nonnociceptive stimuli in the spinal cord, these data suggest that part of Glu release may be regulated by the noradrenergic system through α2 adrenoceptors localized on the primary afferent terminals. 相似文献
25.
26.
A genomic fragment containing the dihydroflavonol 4-reductase B (DFR-B) gene was cloned from the sweet potato (Ipomoea batatas) and its nucleotide sequence was analyzed. The exons and flanking regions were highly homologous to those of previously reported DFR-B genes of the Japanese morning glory, whereas the introns and the intergenic region were less conserved. In addition to the sequences of three miniature inverted-repeat transposable elements (MITEs) and one direct repeat previously reported in the DFR-B gene of Japanese morning glory, two mobile element-like sequences were newly identified in the sweet potato DFR-B gene. At least four allelic sequences were found to exist by amplification of the DFR-B gene from various sweet potato cultivars. One of these allelic sequences had a 2-kb deletion in the intergenic region and was observed in the cultivars with high anthocyanin content in their storage roots. 相似文献
27.
Bo Liu Shigeru Nakashima Seiji Ito Yoshinori Nozawa 《Prostaglandins & other lipid mediators》1996,51(4):233-248
Pertussis toxin-insensitive GTP-binding protein was observed to be involved in prostaglandin F2α(PGF2α)-induced phosphoinositide metabolism in Chinese hamster ovary (CHO) cells transfected with PGF2α receptor cDNA (CHO-PGF2α·R cells) (Ito, S. et al. Biochem. Biophys. Res. Commun. 200: 756, 1994). In the present study, we investigated PGF2α-induced PLD activation in CHO-PGF2α·R cells. PLD activation was examined by measuring the production of [3H]phosphatidylbutanol ([3H]PBut), a specific product of the PLD-catalyzed transphosphatidylation reaction. PGF2α-induced [3H]PBut formation was concentration-dependent with the maximal level obtained at 1 μM PGF2α. The maximal [3H]PBut formation was observed at 2 min after addition of PGF2α. Depletion of extracellular Ca2+ with EGTA suppressed PGF2α-induced PLD activation by 50%. PKC inhibitors Ro31–8425 and calphostin C inhibited PGF2α-induced [3H]PBut formation by 50%. PTK inhibitors genistein and herbimycin A failed to inhibit PGF2α-induced PLD activation. A combination of maximal effective concentrations of PGF2α (1 μM) and PMA (100 nM) enhanced PLD activation in an additive manner. Pretreatment of the cells with PMA for 2 h down-regulated PKCα and decreased PGF2α-induced PLD activation. These results suggest that PLD activation by PGF2α is mediated by both PKC-dependent and -independent pathways and that PKCα is involved in the former pathway. 相似文献
28.
We examined the effect of methionine deficiency on iodothyronine 5’-deiodinase activity in selenium-deficient rats or selenium-sufficient
rats fed sodium selenate or selenomethionine. Forty-two weanling male Wistar rats were divided into six groups and pair fed
the respective purifiedl-amino acid-based diets for 4 wk.l-methionine concentrations in the diet were 8.0 g/kg for sufficient rats, and 2.0 g/kg for deficient rats. Selenium concentrations
in the diet were 0.5 mg/kg (as sodium selenate or selenomethionine) for selenium-sufficient rats and less than 0.005 mg/kg
for selenium-deficient rats. Type I 5’-deiodinase activities were significantly lower in liver and higher in kidney of methionine-deficient
rats than in those of methionine-sufficient rats fed either the selenium-sufficient or the selenium-deficient diets. The type
I 5’-deiodinase activity in brain was significantly lower in the methionine-deficient rats than in the methionine-sufficient
rats fed the selenium-deficient diet. Type II 5’-deiodinase activity in brain was significantly higher in the methionine-deficient
rats than in the methionine-sufficient rats fed selenium-sufficient diet as sodium selenate. Both thyroxine and 3,3’,5-triiodothyronine
concentrations in plasma were significantly higher in the methionine-deficient rats than in the methionine-sufficient rats.
It is suggested that the methionine deficiency affects the 5’-deiodinase activity and thyroid hormones level in the rats. 相似文献
29.
30.
Physical effects of negative air ions in a wet sauna 总被引:10,自引:0,他引:10
I. Watanabe Hiroshi Noro Yoshinori Ohtsuka Yukio Mano Yuko Agishi 《International journal of biometeorology》1997,40(2):107-112
The physical effects of negative air ions on humans were determined in an experimental sauna room equipped with an ionizer.
Thirteen healthy persons took a wet sauna bath (dry bulb temperature 42° C, relative humidity 100%, 10 min exposure) with
or without negative air ions. The subjects were not told when they were being exposed to negative air ions. There were no
differences in the moods of these persons or changes in their blood pressures between the two saunas. The surface temperatures
of the foreheads, hands, and legs in the sauna with negative ions were significantly higher than those in the sauna without
ions. The pulse rates and sweat produced in the sauna with ions were singificantly higher than those in the sauna without
ions. The results suggest that negative ions may amplify the effects on humans of the sauna.
Received: 31 March 1995 / Revised: 25 July 1995 / Accepted: 26 July 1996 相似文献