首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   239篇
  免费   11篇
  国内免费   5篇
  2023年   8篇
  2022年   1篇
  2021年   11篇
  2020年   8篇
  2019年   14篇
  2018年   16篇
  2017年   11篇
  2016年   4篇
  2015年   8篇
  2014年   11篇
  2013年   28篇
  2012年   12篇
  2011年   17篇
  2010年   8篇
  2009年   6篇
  2008年   6篇
  2007年   6篇
  2006年   5篇
  2005年   8篇
  2004年   1篇
  2003年   7篇
  2002年   4篇
  2001年   4篇
  2000年   5篇
  1997年   1篇
  1996年   1篇
  1995年   1篇
  1992年   8篇
  1991年   2篇
  1990年   4篇
  1989年   5篇
  1988年   5篇
  1987年   7篇
  1986年   4篇
  1985年   2篇
  1984年   1篇
  1983年   1篇
  1980年   2篇
  1978年   1篇
  1974年   1篇
排序方式: 共有255条查询结果,搜索用时 31 毫秒
1.
Recurrence risks are derived explicitly in terms of gene frequencies and penetrance coefficients for the general case in which all genotypes have incomplete penetrance. Maximum likelihood estimation of recurrence risks is achieved through the use of the semi-symmetric intraclass contingency table. The resulting formulas and estimation procedure can be useful for the analysis of population and family data, and in genetic counselling.  相似文献   
2.
The steroid, 19-hydroxyandrost-4-ene-3, 17-dione (19-hydroxyandrostene-dione, 19-OH-A-dione) has been known to enhance the mineralocorticoid action of aldosterone. To investigate the age-related change in the plasma 19-OH-A-dione concentration, plasma 19-OH-A-dione, androst-4-ene-3, 17-dione (A-dione), aldosterone and cortisol of 38 non-hypertensive healthy subjects (18 young men and 20 aged men) measured by specific radioimmunoassays. The basal plasma 19-OH-A-dione and A-dione concentration in aged men was significantly lower than in young men (P less than 0.01). Moreover, there was found to be a positive correlation between plasma 19-OH-A-dione and A-dione (P less than 0.01). On the other hand, plasma aldosterone and cortisol in aged men showed a tendency to decrease, but no statistical significance compared to young men was observed. This study demonstrated that there was an apparent age-related decrease not only in plasma A-dione, but also in plasma 19-OH-A-dione, an amplifier or aldosterone action.  相似文献   
3.
Atlantic salmon (Salmo salar) were treated with 17- estradiol to induce vitellogenin synthesis in liver. This led to an increase in liver wet weight and total DNA. After incubation with micrococcal nuclease (EC 3.1.31.1) less soluble chromatin was obtained from nuclei of the estradiol treated than the control fish, but active gene regions were solubilized by the nuclease. Thus, in the estradiol treated fish soluble mononucleosomes contained hybridizable vitellogenin gene sequences. As a result of estradiol treatment the content in total liver of putrescine rose 3-fold, that of spermidine 2-fold, while spermine was unchanged. In muscle no significant changes were observed. The regulatory functions of polyamines during gene expression were investigated by binding (14C)spermine to isolated liver nuclei depleted of endogenous polyamines. The number of binding sites was higher in nuclei of estradiol treated than control fish. (14C)spermine associated preferentially with micrococcal nuclease insensitive chromatin. Thus, the high content of putrescine and spermidine in liver supported the view of polyamine accumulation in proliferating tissues. The preferential binding to condensed chromatin indicated a stabilizing effect of polyamines on the organization of inactive chromatin structures.Abbreviations MNase micrococcal nuclease - PMSF phenylmethylsulfonylfluoride  相似文献   
4.
A 34-yr-old woman with hypertension (142/102 mmHg), hypokalemia, high plasma and urinary aldosterone and low plasma renin activity was studied. A left adrenal tumor and enlarged right adrenal gland were demonstrated by adrenal venography. During administration of dexamethasone (2 mg daily, for 3 weeks), urinary aldosterone excretion decreased abruptly from 22.5 to 9-11 micrograms/day, serum potassium increased and blood pressure fell to 120-130/80-90 mmHg. After left adrenalectomy, all manifestations improved with no medication. The resected adrenal gland revealed clear cell adenoma and micronodular adrenocortical hyperplasia. The patient was considered to be a rare case of glucocorticoid-suppressible hyperaldosteronism with an aldosterone-producing adenoma.  相似文献   
5.
The authors present a new technic to point out the rheumatoid factor by immunofluorescence and compare this technic and the others to classical technics of agglutination. This technic allows to avoid the absorption of rheumatoid factor in the serological reactions using the immunofluorescence.  相似文献   
6.
The action of porcine brain natriuretic peptide (pBNP) on the steroidogenesis was investigated in cultured bovine adrenocortical cells. Porcine BNP induced a significant dose-dependent inhibition of both ACTH- and A II-stimulated aldosterone secretion. 10(-8) M and 10(-7) M pBNP also significantly inhibited ACTH-stimulated cortisol and dehydroepiandrosterone (DHEA) secretions. Binding studies of [125I]-pBNP to bovine adrenocortical membrane fractions showed that adrenal cortex had high-affinity and low-capacity pBNP binding sites, with a dissociation constant (Kd) of 1.70 x 10(-10) M and a maximal binding capacity (Bmax) of 19.9 fmol/mg protein. Finally, the 135 Kd radioactive band was specially visualized in the affinity labeling of bovine adrenal cortex with disuccinimidyl suberate (DSS). These results suggest that pBNP may have receptor-mediated suppressive actions on bovine adrenal steroidogenesis, similar to that in atrial natriuretic peptide (ANP).  相似文献   
7.
We isolated a cDNA encoding type-1 angiotensin II receptor from a human liver cDNA library. The cDNA had an open reading frame encoding a protein of 359 amino acid residues with a relative Mr of 41,060. The deduced amino acid sequence of the human angiotensin II (Ang II) receptor was 95.3% and 94.2% identical to those of bovine and rat type-1 Ang II receptors, respectively, and had a significant similarity with the G protein-coupled receptor. The rank order of the binding to the receptor expressed in COS-7 cells was Ang II greater than Ang III greater than Ang I. The expression of the Ang II receptor mRNA was detected in human liver, lung, adrenal and adrenocortical adenomas but not in adrenomedullary tumor, pheochromocytoma, by Northern blot analysis.  相似文献   
8.
Naturally-derived drugs have drawn much attention in recent decades. Efficiency, lower toxicity, and economic reasons are some of their advantages that justify this broad range of administration for different diseases, including cancer. If we can find a specific combination that boosts the effects of their single therapy, leading to synergism effect, increased efficiency, and decreased toxicity, they can act even better. Quercetin and fisetin, two well-known flavonoids, have been used to fight against various cancers. In this study, we investigated their possible synergism quercetin and fisetin on MCF7, MDA-MB-231, BT549, T47D, and 4T1 breast cancer cell lines. Then the optimum combined dose was used to study their impacts on wound healing abilities and clonogenic properties. The real-time qPCR was used to study the expression of their validated downstream effectors in predicted pathways. A significant synergism effect (p < .01, combination index: <1) was observed for all cell lines. Combination therapy was significantly more effective in colony formation (p < .0001) and wound healing assays (p < .001) compared to single therapies. The expression level of potential effectors was also showed a greater change. In vivo study confirmed the in vitro results and showed how significantly (p < .001) their synergism promotes their singular function in inhibiting cancer progression. The breast cancer mouse models receiving combined therapy lived longer with higher average body weight and smaller tumor sizes. These results exhibit that quercetin and fisetin inhibit cancer cell proliferation, migration and colony formation synergistically, and matrix metalloproteinase signaling and apoptotic pathways are relatively responsible for inhibitory activities.  相似文献   
9.
Production of peaches (Prunus persica (L.) Batsch) for both local market and export is increasing each year in Egypt. Brown rot disease, caused by Monilinia laxa and Monilinia fructigena, is considered one of the most important postharvest rots affecting peaches in Egypt and economic losses are increasing. Antifungal activity of glycyrrhizic acid nanoparticles (GA-NPs) and glycyrrhizic acid (GA) at 0.2 and 0.4 mmol/L was investigated as a control for both these brown rot pathogens on peach fruits in both in vitro and in vivo studies. In the in vitro studies, GA-NPs were the most effective as shown by the ability to decrease linear growth of both brown rot pathogens in potato dextrose agar (PDA) amended with 0.4 mmol/L GA-NPs. Micrographs of M. fructigena exposed to 0.4 mmol/LGA showed mycelial deformations, nodule formation, detachment of the cell wall, shrinkage and inhomogeneous cytoplasmic materials with large vacuoles. Mycelium of M. laxa exposed to 0.4 mmol/ LGA-NPs resulted in thinner and distorted hyphae, nodule formation, cell wall thinning, and swellings. The GANPs and GA treatments improved fruit quality by maintaining firmness and total soluble solids (TSS). GA-NPs were more effective in decreasing decay incidence than their bulk material. The 0.4 mmol/L GA-NPs completely inhibited the disease on naturally infected peach fruits for both seasons of 2018 and 2019. Furthermore, 0.4 mmol/L GA-NPs reduced the disease incidence in inoculated fruits by 95 (M. laxa) and 88% (M. fructigena) in 2018 season and 96 (M. laxa) and 85% (M. fructigena) in 2019 season. In conclusion, GA-NPs could enhance the resistance of peaches against brown rot caused by M. laxa and M. fructigena.  相似文献   
10.
Shawurenine C ( 1a ) and D ( 1b ), a new pair of regioisomeric C19-diterpenoid alkaloids, and five known C19-diterpenoid alkaloids ( 2 – 6 ) were isolated from the aerial part of Delphinium shawurense W. T. Wang. The chemical structures of new compounds were established based on spectroscopic analyses: HR-ESI-MS, and 1D, 2D NMR spectroscopic data. The anti-inflammatory and cytotoxic activities of these diterpenoid alkaloids were also evaluated.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号