全文获取类型
收费全文 | 1225篇 |
免费 | 53篇 |
国内免费 | 5篇 |
出版年
2024年 | 3篇 |
2023年 | 22篇 |
2022年 | 44篇 |
2021年 | 103篇 |
2020年 | 48篇 |
2019年 | 47篇 |
2018年 | 71篇 |
2017年 | 47篇 |
2016年 | 56篇 |
2015年 | 81篇 |
2014年 | 81篇 |
2013年 | 89篇 |
2012年 | 99篇 |
2011年 | 90篇 |
2010年 | 44篇 |
2009年 | 45篇 |
2008年 | 43篇 |
2007年 | 41篇 |
2006年 | 21篇 |
2005年 | 32篇 |
2004年 | 25篇 |
2003年 | 27篇 |
2002年 | 18篇 |
2000年 | 8篇 |
1999年 | 3篇 |
1998年 | 6篇 |
1997年 | 7篇 |
1996年 | 4篇 |
1995年 | 7篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 6篇 |
1991年 | 9篇 |
1990年 | 4篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1985年 | 4篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1970年 | 1篇 |
1966年 | 1篇 |
1965年 | 2篇 |
1964年 | 1篇 |
1962年 | 1篇 |
排序方式: 共有1283条查询结果,搜索用时 457 毫秒
141.
AIMS/METHODS: We established age- and sex-related reference ranges for serum insulin-like growth factor-I (IGF-I) and insulin-like growth factor binding protein-3 (IGFBP-3) levels in 807 healthy Turkish children (428 boys, 379 girls), and constructed a model for calculation of standard deviation scores of IGF-I and IGFBP-3 according to age, sex and pubertal stage. RESULTS: Serum IGF-I and IGFBP-3 concentrations tended to be higher in girls compared to boys of the same ages, but the differences were statistically significant only in pubertal ages (9-14 years) for IGF-I and only in prepubertal ages for IGFBP-3 (6-8 years) (p < 0.05). Peak IGF-I concentrations were observed earlier in girls than boys (14 vs. 15 years, Tanner stage IV vs. V) starting to decline thereafter. IGFBP-3 levels peaked at age 13 and at Tanner stage IV in both sexes with a subsequent fall. Serum levels of IGF-I and IGFBP-3 increased steadily with age in the prepubertal stage followed by a rapid increase in IGF-I in the early pubertal stages. A relatively steeper increase in IGF-I but not in IGFBP-3 levels was observed at age 10-11 years in girls and at 12-13 years in boys which preceded the reported age of pubertal growth spurt. At late pubertal stages, both IGF-I and IGFBP-3 either did not change or decreased by increasing age. Interrelationships between growth factors and anthropometric measurements have been described, and the physiologic consequences of these have been discussed in detail. CONCLUSIONS: Differences in the pattern of IGF-I and IGFBP-3 in the present paper and those reported in other studies emphasize the importance of locally established reference ranges. Establishment of this reference data and a standard deviation score prediction model based on age, sex and puberty will enhance the diagnostic power and utility of IGF-I and IGFBP-3 in evaluating growth disorders in our population. 相似文献
142.
Vishnubalaji R Al-Nbaheen M Kadalmani B Aldahmash A Ramesh T 《Cell and tissue research》2012,347(2):419-427
Mesenchymal stem cells (MSCs) hold promise for cell-based therapy in regenerative medicine. To date, MSCs have been obtained
from conventional bone marrow via a highly invasive procedure. Therefore, MSCs are now also isolated from sources such as
adipose tissue, cord blood and cord stroma, a subject of growing interest. As the characterization and differentiation potential
of adipose-derived MSCs (AD-MSCs) and bone-marrow-derived MSCs (BM-MSCs) have not been documented, we have evaluated and compared
the characteristics of both MSC types by qualitative and quantitative analyses. Both cell types show similar morphology and
surface protein expression, being positive for stromal-associated markers and negative for hematopoietic and endothelial markers.
The colony-forming potential of AD-MSCs is distinctly higher than that of BM-MSCs. Nonetheless, similar adipogenic and osteogenic
differentiation is observed in both groups of MSCs. Cytochemical qualitative analysis and calcium mineralization demonstrate
higher levels toward osteogenic differentiation in BM-MSCs than in AD-MSCs. On the contrary, the percentage of Nile red oil
staining for differentiated adipocytes is higher in AD-MSCs than in BM-MSCs. Quantitative real-time polymerase chain reaction
shows similar patterns of osteogenic- and adipogenic-associated gene expression in both cell types. Each of the MSCs respond
in functional analysis by exhibiting unique properties at the differentiation level according to their micro-environmental
niche. Thus, quantitative analysis might be a valuable means of describing stem cell multipotency, in addition to qualitative
investigation. 相似文献
143.
The aim of this study was to investigate the interaction between nitric oxide (NO) and acetylcholine (ACh) in penicillin-induced experimental epilepsy. Adult male Wistar rats weighing 220 ± 35 g were used in the experiments. The epileptiform activity was induced by microinjection of penicillin (200 IU/1 μl) into the left sensorymotor cortex. Electrocorticogram was recorded by using Ag/AgCl ball electrodes. Sodium nitroprusside (SNP), a NO donor, given intracortically 30 min after penicillin significantly reduced the spike frequency whereas ACh increased the epileptiform activity for 5 min. Atropine, an antagonist for muscarinic receptors, was given intracortically 30 min after penicillin and did not significantly affect epileptiform activity for 30 min. SNP given after atropine significantly suppressed the epileptiform activity. ACh given 10 min after Nω-nitro-L: -arginine methyl ester (L-NAME), a nonspecific nitric oxide synthase inhibitor, did not have a significant effect on spike frequency. When ACh and SNP were administered together, penicillin induced epileptiform activity and spike frequency were significantly suppressed from the 10th minute onwards. It can be concluded that ACh increases the penicillin-induced epileptiform activity while co-administration of ACh and SNP produces a potent anticonvulsant effect as compared to SNP alone. 相似文献
144.
Oh RS Pan WC Yalcin A Zhang H Guilarte TR Hotamisligil GS Christiani DC Lu Q 《The Journal of biological chemistry》2012,287(8):6025-6034
145.
146.
147.
Md. Abdullahil Baque Abdullah Elgirban Eun-Jung Lee Kee-Yoeup Paek 《Acta Physiologiae Plantarum》2012,34(2):405-415
The effect of initial sucrose concentration was investigated in root suspension cultures of Morinda citrifolia to improve root growth and secondary metabolites production, i.e. anthraquinone, phenolics and flavonoids. Besides, oxidative
stress level, antioxidant enzymes activity and membranes damage under different sucrose concentration were estimated. A 5%
sucrose supply was shown to be optimal for the production of root dry mass, but higher sucrose concentrations of 7–9% inhibited
the accumulation of root dry weight (DW). However, the maximum production of anthraquinone (251.89 g L−1 DW), phenolics (165.14 g L−1 DW) and flavonoids (163.56 g L−1 DW) were achieved at 1% sucrose-treated culture, which may be a source carbon skeletons for secondary metabolism. At the
same time was observed low oxidative damage, which could be associated with high levels of secondary metabolites and the increased
activity of catalase. Although, catalase (CAT) activity were stimulated at 7–9% sucrose-treated cultures, high accumulation
of hydrogen peroxide (H2O2) and peroxidation of lipid (MDA) was induced. The observed high activity of CAT and guaiacol peroxidase (G-POD) were not
sufficient enough to mitigate the toxic effect of H2O2. 相似文献
148.
149.
The Naturally occurring novel cyclohexanonyl bromophenol 2(R)-2-(2,3,6-tribromo-4,5-dihydroxybenzyl)cyclohexanone (4) was synthesized as a racemic compound. Cyclohexylphenyl methane derivatives (10-17) with Br, OMe, CO, and OH were also obtained. Inhibition of four human carbonic anhydrase (hCA, EC 4.2.1.1) isozymes I, II, IV, and VI, with compounds 2-4, 8, and 10-26 was investigated. These compounds were found to be promising carbonic anhydrase inhibitors and some of them showed interesting inhibitory activity. Some of the compounds investigated here showed effective hCA inhibitory activity, and might be used as leads for generating novel carbonic anhydrase inhibitors which are valuable drug candidates for the treatment of glaucoma, epilepsy, gastric and duodenal ulcers, neurological disorders, and osteoporosis. 相似文献