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   1661篇
  免费   191篇
  国内免费   35篇
耳鼻咽喉   6篇
儿科学   10篇
妇产科学   24篇
基础医学   163篇
口腔科学   10篇
临床医学   179篇
内科学   410篇
皮肤病学   16篇
神经病学   115篇
特种医学   51篇
外国民族医学   1篇
外科学   180篇
综合类   253篇
预防医学   81篇
眼科学   21篇
药学   143篇
  9篇
中国医学   41篇
肿瘤学   174篇
  2024年   9篇
  2023年   116篇
  2022年   173篇
  2021年   177篇
  2020年   179篇
  2019年   75篇
  2018年   69篇
  2017年   49篇
  2016年   59篇
  2015年   71篇
  2014年   105篇
  2013年   104篇
  2012年   86篇
  2011年   112篇
  2010年   98篇
  2009年   56篇
  2008年   47篇
  2007年   77篇
  2006年   67篇
  2005年   34篇
  2004年   25篇
  2003年   21篇
  2002年   25篇
  2001年   14篇
  2000年   9篇
  1999年   9篇
  1998年   4篇
  1997年   7篇
  1996年   10篇
排序方式: 共有1887条查询结果,搜索用时 390 毫秒
1.
2.
Epidemiological studies on magnesium intake and primary liver cancer (PLC) are scarce, and no prospective studies have examined the associations of magnesium intake with PLC incidence and mortality. We sought to clarify whether higher magnesium intake from diet and supplements was associated with lower risks of PLC incidence and mortality in the US population. Magnesium intake from diet and supplements was evaluated through a food frequency questionnaire in a cohort of 104,025 participants. Cox regression was employed to calculate hazard ratios for PLC incidence and competing risk regression was employed to calculate subdistribution hazard ratios for PLC mortality. Restricted cubic spline regression was employed to test nonlinearity. We documented 116 PLC cases during 1,193,513.5 person-years of follow-up and 100 PLC deaths during 1,198,021.3 person-years of follow-up. Total (diet + supplements) magnesium intake was found to be inversely associated with risks of PLC incidence (hazard ratiotertile 3 vs. 1: 0.44; 95% confidence interval: 0.24, 0.80; ptrend = 0.0065) and mortality (subdistribution hazard ratiotertile 3 vs. 1: 0.37; 95% confidence interval: 0.19, 0.71; ptrend = 0.0008). Similar results were obtained for dietary magnesium intake. Nonlinear inverse dose–response associations with PLC incidence and mortality were observed for both total and dietary magnesium intakes (all pnonlinearity < 0.05). In summary, in the US population, a high magnesium intake is associated with decreased risks of PLC incidence and mortality in a nonlinear dose–response manner. These findings support that increasing the consumption of foods rich in magnesium may be beneficial in reducing PLC incidence and mortality.  相似文献   
3.
Heat stress (HS) is a notable risk factor for female reproductive performance. In particular, impaired oocyte maturation was thought to contribute largely to the HS-induced reproductive dysfunctions. In this study, we confirmed that oocytes undergoing GVBD were much susceptible to HS, and thus compromising subsequent embryonic development. Using N-acetyl-l-cysteine (NAC), we found supplementation of a relatively high dose NAC during in vitro maturation, can protect oocytes from HS-induced complications, and thus rescuing impaired embryonic development. Further analysis indicated that mechanisms responsible for protecting GVBD oocytes from HS by NAC may include: (1) reversing disorganized spindle assembly and inhibited extracellular signal–regulated kinase (ERK) signaling; (2) correcting erroneous H3K27me3 modification and dysregulated expression of imprinted genes; (3) alleviating increased intraoocyte reactive oxygen species accumulation and apoptosis initiation. Our study, focusing on the oocyte meiotic maturation, may provide a safe and promising strategy for protecting reproductive sows under environmental hyperthermal conditions.  相似文献   
4.
Background and aimThis network meta-analysis (NMA) compares the effects of different types of olive oil (OO) on cardiovascular risk factors.Methods and resultsLiterature search was conducted on three electronic databases (Medline, Web of Science, and Cochrane Central). Inclusion criteria: Randomized controlled trials (RCTs) (≥3 weeks duration of intervention) comparing at least two of the following types of OO: refined OO (ROO), mixed OO (MOO), low phenolic (extra) virgin OO (LP(E)VOO), and high phenolic (extra) virgin OO (HP(E)VOO). Random-effects NMA was performed for seven outcomes; and surface under the cumulative ranking curve (SUCRA) was estimated, using an analytical approach (P-score). Thirteen RCTs (16 reports) with 611 mainly healthy participants (mean age: 26–70 years) were identified. No differences for total cholesterol, HDL-cholesterol, triacylglycerols, and diastolic blood pressure were observed comparing ROO, MOO, LP(E)VOO and HP(E)VOO. HP(E)VOO slightly reduce LDL-cholesterol (LDL-C) compared to LP(E)VOO (mean difference [MD]: −0.14 mmol/L, 95%–CI: −0.28, −0.01). Both, HP(E)VOO and LP(E)VOO reduces SBP compared to ROO (range of MD: −2.99 to −2.87 mmHg), and HP(E)VOO may improve oxidized LDL-cholesterol (oxLDL-C) compared to ROO (standardized MD: −0.68, 95%–CI: −1.31, −0.04). In secondary analyses, EVOO may reduce oxLDL-C compared to ROO, and a dose-response relationship between higher intakes of phenolic compounds from OO and lower SBP and oxLDL-C values was detected. HP(E)VOO was ranked as best treatment for LDL-C (P-score: 0.83), oxLDL-C (0.88), and SBP (0.75).ConclusionsHP(E)VOO may improve some cardiovascular risk factors, however, public health implications are limited by overall low or moderate certainty of evidence.  相似文献   
5.
6.
According to conservative estimates, >230 million people are infected with schistosomiasis,which becomes one of the most common parasitic diseases. This study focuses on investigating in vivo and in vitro effects of mmu-miR-92a-2-5p in Schistosoma japonicum-induced liver fibrosis by targeting TLR2. Through bioinformatic analysis, the overexpression of TLR2 and the down-regulation of mmu-miR-92a-2-5p were revealed in the progression of S. japonicum-induced liver fibrosis. BALB/C mice were taken advantage to construct normal control and schistosomiasis liver fibrosis (SLF) model. The mice in model groups were transfected recombinant lentivirus (Lenti-mmu-miR-92a-2-5p or Lenti-NC) to alter the expression of mmu-miR-92a-2-5p in vivo. HE and Masson staining were employed to observe the pathological changes and collagenous fibrosis. QRT-PCR showed that mmu-miR-92a-2-5p was decreased while TLR2 was elevated in the infected groups. However, lenti-mmu-miR-92a-2-5p group could inhibit liver fibrosis. Then the effect of mmu-miR-92a-2-5p on S. japonicum-induced liver fibrosis including cell apoptosis rates, proliferation and proteins related to liver fibrosis was examined in NIH-3T3 mouse embryonic fibroblasts. Moreover, the association between mmu-miR-92a-2-5p and TLR2 was detected by dual-luciferase reporter gene assay and the expression of cytokines IL-4, IFN-γ and TNF-α in SLF model was detected by ELISA. Further, the knockout of TLR2 in C57BL/6J mice was used to confirm the association between mmu-miR-92a-2-5p and TLR2. Thus, these findings demonstrated that mmu-miR-92a-2-5p inhibited S. japonicum-induced liver fibrosis by targeting TLR2 in vitro and in vivo.  相似文献   
7.
OBJECTIVE: To reduce the incidence of sensory deficits and Frey's syndrome by modifying the traditional superficial parotidectomy. STUDY DESIGN: After raising the skin flap, the parotid gland fascia (PGF) was elevated to form a posterior pedicle fascial flap and then was replaced after the gland removal. The great auricular nerve (GAN) that runs within the PGF was not separated, so both the GAN and the PGF were preserved. Before this modification, the GAN and PGF were examined anatomically. The complication rates in the modified and control groups were compared. RESULTS: 1) The GAN, which runs within the thick and pycnotic PGF, trifurcates into postauricular, preauricular and lobule branches. The modification could be carried out practically based on the anatomy study. 2) Long-term sensory deficit was encountered in 13.3% of the control group, but 0% in the modified one. Frey's syndrome was suffered by 66.7% and 16.7% cases in the control and modified group respectively. The incidence of other complications was not significantly different. CONCLUSION: Our modification is practical. It decreases the complications significantly. EBM rating: B-3b.  相似文献   
8.
We thank Drs Liu and Li for their interest in our randomizedtrial investigating the anti-arrhythmic effect of perindopriland losartan in the setting of lone paroxysmal atrial fibrillation(AF). While agreeing on modification of atrial remodelling asthe  相似文献   
9.
内毒素血症时大鼠脂多糖结合蛋白的变化及其意义   总被引:2,自引:0,他引:2  
目的 探讨内毒素血症时大鼠肝组织中脂多糖结合蛋白mRNA的表达、血浆中脂多糖结合蛋白 (LBP)含量的变化及其意义。方法 经大鼠尾静脉注入内毒素 (5mg/kg)建立内毒素血症动物模型 ,检测不同时点模型鼠肝组织中LBPmRNA的表达 ,同时检测血浆中LBP、内毒素、TNF α及IL 6含量的变化 ,并与对照组相比较。另取肝组织在电镜下观察其病理学改变。结果 随着内毒素血症时间的延长 ,内毒素组大鼠肝组织LBPmRNA的表达明显增强 ,血浆中LBP、TNF α和IL 6含量也明显增加 ,与对照组比较差异有高度显著性 (P<0 .0 1)。电镜观察见肝细胞脂肪变 ,线粒体空化 ,枯否氏细胞数量增多、体积增大、吞噬功能增强。结论 内毒素血症时 ,大鼠肝组织中LBPmRNA表达明显增强 ,血浆中LBP含量也明显增加。由此提示 ,增高的LBP可能在脂多糖介导的枯否氏细胞激活及产生、释放各种炎性介质中可能起了重要作用。  相似文献   
10.
医学生需要具备不同层次的能力,所以需要不同的考试形式来衡量能力的高低。不同考试方法的选择对于反映所选课程的学习效果至关重要。本文主要介绍了维也纳医科大学的考试设计及其作用,以及对我国医学教育评估的启示。通过学习奥地利先进的教学评估理念和方法,可为我国医学教育评估方式改革、培养高素质医学人才提供借鉴。  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