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   113638篇
  免费   7698篇
  国内免费   3898篇
耳鼻咽喉   424篇
儿科学   2269篇
妇产科学   520篇
基础医学   7483篇
口腔科学   578篇
临床医学   17182篇
内科学   22726篇
皮肤病学   350篇
神经病学   12792篇
特种医学   4246篇
外国民族医学   2篇
外科学   7212篇
综合类   22532篇
现状与发展   1篇
预防医学   6604篇
眼科学   445篇
药学   11627篇
  112篇
中国医学   6124篇
肿瘤学   2005篇
  2024年   89篇
  2023年   1531篇
  2022年   2520篇
  2021年   3803篇
  2020年   3669篇
  2019年   2917篇
  2018年   3157篇
  2017年   3147篇
  2016年   3943篇
  2015年   4241篇
  2014年   8341篇
  2013年   7996篇
  2012年   7322篇
  2011年   7449篇
  2010年   6299篇
  2009年   5751篇
  2008年   5612篇
  2007年   5615篇
  2006年   5288篇
  2005年   4606篇
  2004年   4140篇
  2003年   3307篇
  2002年   2773篇
  2001年   2582篇
  2000年   2177篇
  1999年   1877篇
  1998年   1572篇
  1997年   1592篇
  1996年   1294篇
  1995年   1164篇
  1994年   1252篇
  1993年   924篇
  1992年   876篇
  1991年   848篇
  1990年   748篇
  1989年   621篇
  1988年   589篇
  1987年   433篇
  1986年   430篇
  1985年   512篇
  1984年   431篇
  1983年   283篇
  1982年   349篇
  1981年   321篇
  1980年   225篇
  1979年   173篇
  1978年   125篇
  1977年   95篇
  1976年   69篇
  1975年   46篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.

Background

Aneurysmal subarachnoid hemorrhage is an important cause of premature death and disability worldwide. Magnesium sulphate is shown to have a neuroprotective effect and it reverses cerebral vasospasm. Milrinone is also used in the treatment of cerebral vasospasm. The aim of the present study was to compare the effect of prophylactic magnesium sulphate and milrinone on the incidence of cerebral vasospasm after subarachnoid hemorrhage.

Methods

The study included 90 patients with aneurysmal subarachnoid hemorrhage classified randomly (by simple randomization) into two groups: magnesium sulphate was given as an infusion of 500 mg.day?1 without loading dose for 21 days. Group B: milrinone was given as an infusion of 0.5 μg.kg?1.min?1 without loading dose for 21 days. The cerebral vasospasm was diagnosed by mean cerebral blood flow velocity in the involved cerebral artery (mean flow velocity  120 cm.s?1), neurological deterioration by Glasgow coma scale, or angiography (the decrease in diameter of the involved cerebral artery >25%).

Results

The mean cerebral blood flow velocity decreased significantly in the magnesium group compared to milrinone group through Day 7, Day 14 and Day 21 (p < 0.001). The incidence of cerebral vasospasm decreased significantly with magnesium compared to milrinone (p = 0.007). The Glasgow coma scale significantly improved in the magnesium group compared to milrinone group through Day 7, Day 14 and Day 21 (p = 0.036, p = 0.012, p = 0.016, respectively). The incidence of hypotension was higher with milrinone than magnesium (p = 0.012).

Conclusions

The incidence of cerebral vasospasm after aneurysmal subarachnoid hemorrhage was significantly lower and Glasgow coma scale significantly better with magnesium when compared to milrinone. Milrinone was associated with a higher incidence of hypotension and requirement for dopamine and norepinephrine when compared to magnesium.  相似文献   
103.

Objective

Acute mesenteric ischemia (AMI) is an emergent event with a high mortality rate; survivors have high rates of intestinal failure. Restoration of blood flow using endovascular or surgical revascularization is associated with better outcome in terms of survival rate and intestinal resection. Retrograde open mesenteric stenting (ROMS), which is a hybrid technique, combines two benefits: prompt blood flow restoration with an endovascular approach and inspection and resection of the small bowel. The aim of the study was to assess the results of ROMS in thrombotic AMI in a retrospective multicenter study.

Methods

We retrospectively enrolled all consecutive patients who underwent ROMS revascularization for occlusive thrombotic AMI in three participating tertiary care centers between November 2012 and March 2017.

Results

Twenty-five patients (14 men and 11 women; mean age, 64.9 ± 11.6 years) were included. In two patients, ROMS was not possible because of failure of re-entry in the aortic lumen (technical success, 92%). One patient required revascularization of two visceral arteries and underwent an aortohepatic bypass. Five patients (20%) underwent endarterectomy and patch angioplasty of the superior mesenteric artery before retrograde stenting. Thirteen patients (52%) required bowel or colon resection (11 patients required both resections) during the initial procedure with a mean length of small bowel resection of 52 ± 87 cm. The 30-day operative mortality rate was 25%, and the overall 1-year survival rate was 65%. The 1-year primary patency rate was 92%. In one patient, postoperative imaging at 1 month showed stent migration in the aortic bifurcation.

Conclusions

ROMS for thrombotic AMI has a high technical success rate and a high midterm primary patency rate. It could be an alternative procedure to retrograde superior mesenteric artery bypass for patients when percutaneous endovascular revascularization is not indicated or has failed.  相似文献   
104.
Objective: To investigate the changes in serum miR-124 levels in patients with acute cerebral infarction (ACI) and elucidate the underlying mechanism by a dynamic monitor.

Methods: Fifty-four patients with ACI and 51 healthy controls were included in our study. Baseline characteristics and blood samples were collected for further analysis. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to measure the serum miR-124 levels. The dual-luciferase reporter assay was used to evaluate the effect of miR-124 on iASPP, a protein that inhibits apoptosis stimulating proteins in the p53 family.

Results: Compared with normal controls, the miR-124 levels in the ACI group rapidly decreased at phase 1 (within 24?h after ischemia) (p?<?0.001) and then gradually increased at phase 2 (48?~?72?h after ischemia) (p?<?0.001) and phase 3 (the 7th day after ischemia) (p?<?0.001). The dual-luciferase reporter assay showed that miR-124 down-regulates iASPP expression in 293T cells.

Conclusion: The miR-124 levels are down-regulated in ACI patients. The dynamic changes of miR-124 might provide a possible method for the detection of ischemic stroke.

  • Highlights
  • The difference in miR-124 expression levels between ACI patients and normal controls.

  • Dynamic changes of miR-124 expression levels in ACI patients.

  • The down-regulation of miR-124 upon iASPP expression.

  相似文献   
105.
106.
BackgroundThe relationship between body mass index (BMI) and in-hospital mortality risk among patients with acute myocardial infarction (AMI) remains controversial.Methods and ResultsWe included 35,964 patients diagnosed with AMI in China Acute Myocardial Infarction registry between January 2013 and December 2016. Patients were categorized into 4 groups according to BMI level: BMI <18.5, 18.5–24.9, 25–30, and ≥30 kg/m2 for underweight, normal, overweight, and obese groups, respectively. Clinical data were extracted for each patient, and multivariable logistic regression analysis was used to examine the association between BMI level and in-hospital mortality. Compared with normal-weight patients, obese patients were younger, more often current smokers, and more likely to have hypertension, hyperlipidemia, and diabetes. Multivariable regression analysis results demonstrated that compared with normal group, underweight group had significantly higher in-hospital mortality (odds ratio [OR]: 1.34; 95% confidence interval [CI]: 1.06–1.69; p = 0.016), while overweight group (OR: 0.86; 95% CI: 0.77–0.97; p = 0.011) and obese group (OR: 0.65; 95% CI: 0.46–0.91; p = 0.013) had lower mortality. All subgroups showed a trend toward lower in-hospital mortality risk as BMI increased.ConclusionsOur study provided robust evidence supporting “obesity paradox” in a contemporary large-scale cohort of patients with AMI and demonstrated that increased BMI was independently associated with lower in-hospital mortality.  相似文献   
107.
108.
109.
目的比较胸腰椎骨折患者接受经椎旁肌间隙入路与微创经皮入路手术治疗的效果及关节功能。方法回顾性分析2014年4月-2015年10月在该院接受内固定手术治疗的胸腰椎骨折患者,根据手术入路不同分为椎旁入路组和经皮微创组,分别接受经椎旁肌间隙入路与微创经皮入路手术治疗。比较两组患者的手术情况、围手术期血清创伤分子含量以及远期功能恢复情况和矫正畸形效果。结果椎旁入路组的手术时间明显短于经皮微创组,差异有统计学意义(P0.05);术中出血量、术后引流量、术后卧床时间、住院总时间与经皮微创组比较,差异均无统计学意义(P0.05);两组患者术后当天的血清肌酸激酶(CK)、肌红蛋白(Myo)和乳酸脱氢酶(LDH)含量比较,差异均无统计学意义(P0.05),术后3、6和12个月时的伤椎前后缘高度比、Cobb角、视觉模拟评分(VAS)比较,差异均无统计学意义(P0.05)。结论椎旁肌间隙入路与微创经皮入路手术治疗胸腰椎骨折的效果和创伤程度相当,椎旁肌间隙入路的手术操作更为简单、手术时间更短。  相似文献   
110.
目的探讨GATA6基因启动区-493(rs144923558)G/A、-172(rs146748749)G/A 2个位点单核苷酸多态性(SNP)与急性心肌梗死(AMI)之间的关系及其相关的危险因素。方法采用病例-对照研究方法,收集328例AMI患者和344例正常对照;应用聚合酶链反应-限制性内切酶片段长度多态性技术结合DNA测序后的序列比对进行数据统计;运用Hardy-Weinberg平衡检验后,应用χ~2检验进行相关分析;利用Logistic回归对多种危险因素以及2个SNP位点与AMI发病进行关联性分析;利用Haplovview4.2软件和SHEsis网站进行连锁不平衡及单倍体分析。结果 2个SNP位点共检测出3种基因型为GG、GA和AA,其基因型分布均符合Hardy-Weinberg平衡(P0.05),同时在AMI组与对照组间差异无显著性(P0.05)。多因素Logistic回归分析:增龄、高血压病、吸烟、低密度脂蛋白胆固醇(LDLC)和甘油三酯(TG)升高是AMI发病的独立危险因素(P0.05),HDLC为保护因素(P0.05)。在显性、隐性和加性3种不同遗传模式下进行Logistic回归分析发现,2个SNP位点与AMI发病无关联性。进行连锁不平衡和单倍型分析提示,该2个SNP位点处于同一个连锁不平衡区域(D′=1.000,r~2=1.000),单倍型GG和AA均未增加AMI易感性(P0.05)。结论 GATA6基因启动区-493(rs144923558)G/A与-172(rs146748749)G/A两个SNP位点为完全连锁不平衡,其中GG为主要单倍型。该2个SNP位点及其单倍体型与AMI发病无相关性,但提供了GATA6基因启动区多态性的群体遗传学资料。  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