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   7345篇
  免费   373篇
  国内免费   46篇
耳鼻咽喉   173篇
儿科学   353篇
妇产科学   289篇
基础医学   635篇
口腔科学   307篇
临床医学   632篇
内科学   1596篇
皮肤病学   125篇
神经病学   377篇
特种医学   205篇
外科学   1302篇
综合类   373篇
一般理论   4篇
预防医学   390篇
眼科学   254篇
药学   443篇
中国医学   32篇
肿瘤学   274篇
  2024年   7篇
  2023年   100篇
  2022年   283篇
  2021年   441篇
  2020年   213篇
  2019年   251篇
  2018年   295篇
  2017年   209篇
  2016年   266篇
  2015年   331篇
  2014年   366篇
  2013年   418篇
  2012年   579篇
  2011年   556篇
  2010年   315篇
  2009年   282篇
  2008年   441篇
  2007年   439篇
  2006年   420篇
  2005年   367篇
  2004年   295篇
  2003年   258篇
  2002年   189篇
  2001年   49篇
  2000年   53篇
  1999年   43篇
  1998年   32篇
  1997年   23篇
  1996年   22篇
  1995年   15篇
  1994年   15篇
  1993年   9篇
  1992年   23篇
  1991年   19篇
  1990年   19篇
  1989年   13篇
  1988年   14篇
  1987年   13篇
  1986年   5篇
  1985年   10篇
  1984年   5篇
  1983年   6篇
  1980年   5篇
  1979年   5篇
  1977年   5篇
  1974年   6篇
  1973年   4篇
  1972年   4篇
  1970年   5篇
  1969年   4篇
排序方式: 共有7764条查询结果,搜索用时 15 毫秒
91.
92.
93.
Polysaccharides isolated from mushrooms have recently attracted attention due to its potential immune-stimulatory activity. The aim of this study was to validate the in vitro immune-stimulatory activities of various mushroom extracts. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay revealed that Pleurotus eryngii, with the highest β-glucan (18.94%) content, displayed highest viability on macrophage cells of 62.59% at 200?μg/ml concentration. Pleurotus cystidiosus, with 18.16% β-glucan, content showed highest activation of NF-kB (0.7?µg/ml) at a concentration of 100?µg/ml. Termitomyces heimii, with the lowest percentage of β-glucan (0.51%), exhibited highest phagocytosis index of 9.38 at 12.5?µg/ml. The brown strain of Agaricus bisporus with 1.54% of β-glucan stimulates the highest nitric oxide (NO) production of 12.39?µM nitrite oxide at 100?µg/ml. This study revealed that hot water extracts of mushrooms have different β-glucan contents and produced varying immune-stimulatory activities. Among these, Pleurotus spp. demonstrated the highest percentage of β-glucan content and viability of macrophage cells. Pleurotus spp. are deemed immune-stimulatory by increasing phagocytic activity, NO production, and triggered the activation of NF-kB.  相似文献   
94.
95.
96.

Background

Dental caries is still the most prevalent chronic disease worldwide. In the occupied Palestinian territory, data about oral health status and its determinants are scarce. This study aimed to assess the prevalence of dental caries and associated factors among schoolchildren in a random sample of marginalised schools in the West Bank.

Methods

Marginalised schools (according to the School Support Program [SPP] criteria) were stratified by district, gender, and grade level to select a random sample of 20 schools. Students in the sixth and ninth grades were interviewed by senior dental students about their oral hygiene and diet habits. Students' weight, height, gingival health, and dental caries experience were assessed. Senior dental students were trained and calibrated to carry out the interviews and the examinations. Parental informed consents were collected by school administrative staff. Ethics approval for the study was obtained from the Al-Quds University Scientific Research Ethics Committee.

Findings

In total, 1282 students completed the interviews and the clinical screening. The mean decayed, missing and filled teeth (DMFT) index was 6·4 (SD 4·4). According to the WHO dental caries experience classification, 49% (309 of 623) of the sixth grade students and 74% (484 of 658) of the ninth grade students fell in the high and very high categories. The mother's level of education and recent visit to the dentist correlated negatively with DMFT score (ρ=–0·06, p=0·029; ρ=–0·063, p=0·024). BMI was correlated positively with DMFT (r=0·092, p=0·001). Drinking milk and fresh juices was related to lower DMFT scores (r=–0·077, p=0·006 and r=–0·072, p=0·010). In the final model, grade (β=0·314, p<0·0001), gender (β=0·058, p=0·034), recent visit to the dentist (β=–0·059, p=0·029) and drinking fresh juices (β=–0·054, p=0·047) were significant factors in explaining the high level of dental caries in this sample.

Interpretation

Students in the marginalised schools of the West Bank have high DMFT scores that indicate high prevalence of dental caries. Access to dental care and bad oral health habits are associated with high disease prevalence. Interventions to improve access to care and increase awareness about healthy diet and hygiene habits are crucial to alleviate the burden of oral disease in this population.

Funding

AMIDEAST School Support Program (SSP).  相似文献   
97.
98.
Objective Familial Mediterranean fever (FMF) is an autosomal recessive recurrent polyserositis with a higher prevalence in some ethnic groups, including Turks. Mutations in the FMF gene (MEFV) were found associated with FMF. The aim of this study was to analyze MEFV gene mutations in FMF patients to gain insight into the mutation phenotype correlation.Objectives We analyzed the most frequent mutations (M680I, M694V, V726A, and E148Q) in a group of young male Turkish FMF patients using an amplification refractory mutation system and a commercial kit.Results M694V mutation was detected in 80% of the patients. After making a strict diagnostic discrimination between arthralgia and arthritis, arthritis was present in 71% of homozygous and 29.4% of heterozygous patients for M694V mutation. Other mutations were not found to correlate with specific symptoms or findings.Conclusion The homozygosity of M694V mutation in the MEFV gene is associated with arthritis in FMF patients.  相似文献   
99.
Malloy PJ  Xu R  Peng L  Peleg S  Al-Ashwal A  Feldman D 《Endocrinology》2004,145(11):5106-5114
Hereditary vitamin D-resistant rickets (HVDRR) is an autosomal recessive disease caused by mutations in the vitamin D receptor (VDR). We studied a young Saudi Arabian girl who exhibited the typical clinical features of HVDRR, but without alopecia. Analysis of her VDR gene revealed a homozygous T to C mutation in exon 7 that changed isoleucine to threonine at amino acid 268 (I268T). From crystallographic studies of the VDR ligand-binding domain, I268 directly interacts with 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] and is involved in the hydrophobic stabilization of helix H12. We recreated the I268T mutation and analyzed its effects on VDR function. In ligand binding assays, the I268T mutant VDR exhibited an approximately 5- to 10-fold lower affinity for [(3)H]1,25(OH)(2)D(3) compared with the wild-type (WT) VDR. The I268T mutant required approximately a 65-fold higher concentration of 1,25(OH)(2)D(3) to be equipotent in gene transactivation. Both retinoid X receptor heterodimerization and coactivator binding were reduced in the I268T mutant. Analogs of 1,25(OH)(2)D(3) have been proposed as potential therapeutics for patients with HVDRR. Interestingly, in protease sensitivity assays, treatment with the potent vitamin D analog, 20-epi-1,25(OH)(2)D(3), stabilized I268T mutant proteolytic fragments better than 1,25(OH)(2)D(3). Moreover, 20-epi-1,25(OH)(2)D(3) restored transactivation of the I268T mutant to levels exhibited by WT VDR treated with 1,25(OH)(2)D(3). In conclusion, we describe a novel mutation, I268T, in the VDR ligand-binding domain that alters ligand binding, retinoid X receptor heterodimerization, and coactivator binding. These combined defects in VDR function cause resistance to 1,25(OH)(2)D(3) action and result in the syndrome of HVDRR.  相似文献   
100.
BACKGROUND/AIMS: Apoptotic and anti-proliferative effects of heparin on a number of cancers have been described. There have been no studies analyzing the effect of heparin on human hepatoma cells. The aim of this study was to investigate the effect of heparin on human hepatoma cell line, HepG2. METHODOLOGY: HepG2 cell line was cultured with different concentrations of heparin. Colony count, viability assay, percentage of the apoptosis and proliferative index were assessed at the end of the 7th day. Trypan blue was used to assess viability. Apoptosis and proliferative indexes were assessed by flow-cytometry. RESULTS: Hepatoma cells were arrested at the G0/G1 phase with heparin incubation and proliferative indexes decreased significantly in 20, 40 and 80 U/mL of heparin concentrations in comparison with the control (36 +/- 1%, 30 +/- 5% and 29 +/- 8% vs. 44 +/- 1%, p < 0.01). Flow cytometry revealed a statistically significant increase in apoptosis in groups incubated with 40 and 80 U/mL of heparin in comparison with the control (39 +/- 26% and 58 +/- 18% vs. 0.83 +/- 1.3%, p < 0.01). Colony counts per well and viable cells per microL decreased significantly in 80 U/mL of heparin. CONCLUSIONS: Heparin leads to a significant anti-proliferative and an apoptotic effect on human hepatoma cells in vitro.  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