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   5081篇
  免费   310篇
  国内免费   75篇
耳鼻咽喉   70篇
儿科学   92篇
妇产科学   125篇
基础医学   787篇
口腔科学   224篇
临床医学   533篇
内科学   1021篇
皮肤病学   83篇
神经病学   327篇
特种医学   504篇
外科学   508篇
综合类   128篇
一般理论   1篇
预防医学   298篇
眼科学   45篇
药学   332篇
中国医学   53篇
肿瘤学   335篇
  2023年   22篇
  2022年   90篇
  2021年   160篇
  2020年   70篇
  2019年   109篇
  2018年   130篇
  2017年   99篇
  2016年   146篇
  2015年   188篇
  2014年   234篇
  2013年   270篇
  2012年   422篇
  2011年   357篇
  2010年   208篇
  2009年   177篇
  2008年   260篇
  2007年   259篇
  2006年   253篇
  2005年   208篇
  2004年   152篇
  2003年   156篇
  2002年   147篇
  2001年   118篇
  2000年   128篇
  1999年   75篇
  1998年   66篇
  1997年   64篇
  1996年   59篇
  1995年   44篇
  1994年   36篇
  1993年   40篇
  1992年   49篇
  1991年   46篇
  1990年   40篇
  1989年   47篇
  1988年   50篇
  1987年   78篇
  1986年   58篇
  1985年   24篇
  1984年   20篇
  1983年   31篇
  1982年   23篇
  1981年   31篇
  1980年   23篇
  1979年   19篇
  1978年   18篇
  1976年   26篇
  1975年   14篇
  1974年   14篇
  1972年   16篇
排序方式: 共有5466条查询结果,搜索用时 0 毫秒
61.
Sex impacts the development of the brain and cognition differently across individuals. However, the literature on brain sex dimorphism in humans is mixed. We aim to investigate the biological underpinnings of the individual variability of sexual dimorphism in the brain and its impact on cognitive performance. To this end, we tested whether the individual difference in brain sex would be linked to that in cognitive performance that is influenced by genetic factors in prepubertal children (N = 9,658, ages 9–10 years old; the Adolescent Brain Cognitive Development study). To capture the interindividual variability of the brain, we estimated the probability of being male or female based on the brain morphometry and connectivity features using machine learning (herein called a brain sex score). The models accurately classified the biological sex with a test ROC–AUC of 93.32%. As a result, a greater brain sex score correlated significantly with greater intelligence (p fdr < .001, ηp2 = .011–.034; adjusted for covariates) and higher cognitive genome‐wide polygenic scores (GPSs) (p fdr < .001, ηp2 < .005). Structural equation models revealed that the GPS‐intelligence association was significantly modulated by the brain sex score, such that a brain with a higher maleness score (or a lower femaleness score) mediated a positive GPS effect on intelligence (indirect effects = .006–.009; p = .002–.022; sex‐stratified analysis). The finding of the sex modulatory effect on the gene–brain–cognition relationship presents a likely biological pathway to the individual and sex differences in the brain and cognitive performance in preadolescence.  相似文献   
62.
BACKGROUND/OBJECTIVESAdolescents who skip breakfast have an increased prevalence of chronic diseases. Thus, we aimed to evaluate whether the intake of rice-based breakfast had positive effects on blood glucose indices and to determine the possibility of diabetes prevalence in Korean youths who habitually skip breakfast.SUBJECTS/METHODSIn this randomized parallel-group controlled trial, 81 subjects who were suitable for compliance among 105 middle-and high-school students aged 12-18 years who usually skipped breakfast were included in this study (rice-meal group [RMG], n = 26; wheat-meal group [WMG], n = 29; general-meal group [GMG], n = 26). The RMG and WMG received a rice-based breakfast and a wheat-based breakfast for 12 weeks, respectively. The anthropometric indices, blood glucose indices, and metabolites were measured at baseline and the endpoint, respectively.RESULTSThe mean body weights in the RMG, WMG, and GMG groups at the endpoint were 62.44 kg, 61.80 kg, and 60.28 kg, respectively, and the mean body weights of the WMG and GMG groups at the endpoint were significantly higher than that at baseline (P < 0.05). The levels of fasting insulin and homeostasis model assessment of insulin resistance (HOMA-IR) values were significantly decreased in the RMG group at the endpoint compared to baseline (P < 0.05, P < 0.05, respectively). The levels of tryptophan and tyrosine in the WMG group at the endpoint were significantly higher than that those at baseline (P < 0.01, P < 0.05, respectively).CONCLUSIONSRice-based breakfast has positive effects on fasting insulin levels and HOMA-IR in Korean adolescents who skip breakfast. Additionally, it was found that a skipping breakfast could increase the prevalence of diabetes in adolescents who skip breakfast. Therefore, in addition to reducing breakfast skipping, it is vital to develop a rice-based menu that fits teenage preferences to prevent chronic diseases such as diabetes.Trial RegistrationClinical Research Information Service Identifier: KCT0004089  相似文献   
63.
1 临床资料 患者男性,16岁,因牙列不齐要求矫正.临床检查:恒牙,左上侧切牙先天缺失,左上尖牙为乳牙滞留且松动Ⅰ°,头颅正侧位片均显示左上尖牙埋伏阻生:牙冠向近中,牙根向远中横斜向位阻生.右上侧切牙唇倾,上中切牙内倾,咬及下前牙唇侧根部,使下前牙龈萎缩,牙根暴露且下颌牙列拥挤.诊断为:左上尖牙埋伏阻生 深覆 牙列拥挤(图1).  相似文献   
64.
A previous animal study demonstrated that the administration of Omija extract and soybean mixture (OSM) improved glycemic control in the type 2 diabetes model. In this study, we conducted a 12-week, randomized, double-blinded, and placebo-controlled clinical trial to determine the effects of OSM in humans with hyperglycemia. Participants with fasting plasma concentrations of 100–140 mg/dL were enrolled (n = 80) and administered either OSM or placebo products for 12 weeks. The outcomes included measurements of efficacy (fasting plasma glucose (FPG), postprandial glucose (PPG), fasting plasma insulin (FPI), postprandial insulin (PPI), hemoglobin A1c (HbA1c), C-peptide, fructosamine, and lipid parameters) and safety at baseline and at 12 weeks. After the intervention, the OSM group showed significantly decreased levels of FPG, PPG (30, 60 min), PPI (60 min), insulin area under the curve (AUC), fructosamine, and low-density-lipoprotein (LDL) cholesterol compared to the placebo group. No clinically significant changes in any safety parameter were observed. Therefore, it is hypothesized that OSM supplementation is an effective and safe functional food supplement for humans with hyperglycemia.  相似文献   
65.
66.
OBJECTIVES: To estimate the combined screening performance of first and early second trimester prenatal serum markers for Down syndrome, in screening for the development of preeclampsia, and analyze the correlation among marker levels, week of onset, and severity of the disease. METHODS: A retrospective cohort study was carried out on 32 women with preeclampsia and 3044 controls. Serum samples from these pregnancies were assayed for pregnancy-associated plasma protein-A (PAPP-A), alpha-fetoprotein (AFP), unconjugated estriol (uE3), human chorionic gonadotrophin (hCG), and inhibin-A. A likelihood ratio and the odds of being affected given a positive result (OAPR) of various combinations of markers were calculated and receiver operating characteristic (ROC) curves analysis was performed. RESULTS: In the pregnancies that subsequently developed preeclampsia, first trimester PAPP-A concentration was significantly lower and concentrations of early second trimester inhibin-A and hCG significantly elevated. Levels of early second trimester uE3 and AFP were not significantly altered. We also found that inhibin-A correlates with both onset of the disease and the severity. CONCLUSION: Down syndrome biochemical markers levels are altered in those patients who subsequently developed preeclampsia and may be a useful screening test for preeclampsia. Inhibin-A is the most predictive marker and correlates with the severity of subsequent preeclampsia and inversely with the week of occurrence of preeclampsia.  相似文献   
67.
68.
69.
70.
Abnormal expression of hepatoma specific gamma-glutamyl transferase and alteration of gamma-glutamyl transferase gene methylation status in patients with hepatocellular carcinoma@Jiang DR @Huang ZW @Lu JX @Tao QY @Yu JZ @Meng XY  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