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   58171篇
  免费   3180篇
  国内免费   1497篇
耳鼻咽喉   359篇
儿科学   921篇
妇产科学   812篇
基础医学   4079篇
口腔科学   309篇
临床医学   7696篇
内科学   14514篇
皮肤病学   104篇
神经病学   3479篇
特种医学   5136篇
外国民族医学   3篇
外科学   9128篇
综合类   9153篇
现状与发展   3篇
预防医学   1350篇
眼科学   489篇
药学   3417篇
  27篇
中国医学   1215篇
肿瘤学   654篇
  2024年   73篇
  2023年   803篇
  2022年   1297篇
  2021年   2198篇
  2020年   1976篇
  2019年   1786篇
  2018年   1834篇
  2017年   1636篇
  2016年   1706篇
  2015年   1856篇
  2014年   3970篇
  2013年   3800篇
  2012年   3230篇
  2011年   3604篇
  2010年   3097篇
  2009年   3094篇
  2008年   3148篇
  2007年   3197篇
  2006年   2917篇
  2005年   2420篇
  2004年   1922篇
  2003年   1661篇
  2002年   1357篇
  2001年   1314篇
  2000年   993篇
  1999年   907篇
  1998年   906篇
  1997年   842篇
  1996年   639篇
  1995年   638篇
  1994年   524篇
  1993年   479篇
  1992年   423篇
  1991年   339篇
  1990年   291篇
  1989年   260篇
  1988年   243篇
  1987年   213篇
  1986年   174篇
  1985年   209篇
  1984年   170篇
  1983年   89篇
  1982年   139篇
  1981年   100篇
  1980年   85篇
  1979年   82篇
  1978年   63篇
  1977年   48篇
  1976年   42篇
  1975年   17篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
32.
33.
34.
患者男,22岁,无明显诱因咳嗽、痰中带血1周,起初干咳,后咳痰并痰中带血,偶咯出少量暗红色血液;无发热、盗汗、乏力,无胸闷、胸痛及呼吸困难,平素体健,无家族病史。查体:双肺呼吸音稍粗,右肺下叶闻及细湿啰音。胸部增强CT:右肺下叶基底段见片状磨玻璃影,内见直径约8mm粗大供血动脉自腹腔干发出;支气管树分支及肺发育正常,未见隔离肺(图1A^1C)。肺动脉CTA示右下肺基底段动脉部分缺如(图1D),考虑为右下肺异常体动脉供血并周围肺组织肺泡出血可能。  相似文献   
35.
36.
37.
Introduction: It is important to know how to treat hypertension in patients with coronary artery disease (CAD). The reason for the review was to update this treatment and to discuss the 2015 American Heart Association/American College of Cardiology/American Society of Hypertension 2015 guidelines of treatment of hypertension in patients with CAD.

Areas covered: Studies between 1968 and 2015 were reviewed on treatment of hypertension in patients with CAD using a Medline search, and studies between 1977 and 2015 were reported. Hypertension should be treated with beta blockers and ACE inhibitors or angiotensin receptor blockers (ARBs). Long-acting nitrates are effective antianginal and anti-ischemic drugs. Calcium-channel blockers (CCBs) may be added if angina persists despite beta blockers and long-acting nitrates. The 2015 guidelines recommend that the blood pressure should be < 140/90 mm Hg in patients aged ≤ 80 years and the systolic blood pressure < 150 mm Hg if they are ≥ 80 years.

Expert opinion: Hypertension in patients with CAD should be treated with beta blockers and ACE inhibitors or ARBs. Long-acting nitrates are effective antianginal and anti-ischemic drugs. CCBs may be added if angina persists despite beta blockers and long-acting nitrates. The blood pressure should be < 140/90 mm Hg in patients aged < 80 years and the systolic blood pressure < 150 mm Hg if they are ≥ 80 years.  相似文献   
38.

Objective

Hypertonic saline (HTS) has potent immune and vascular effects. We assessed recipient pretreatment with HTS on allograft function in a porcine model of heart transplantation and hypothesized that HTS infusion would limit endothelial and left ventricular (LV) dysfunction following transplantation.

Methods

Heart transplants were performed after 6 hours of cold ischemic storage. Recipient pigs were randomized to treatment with or without HTS (7.5% NaCl) before cardiopulmonary bypass (CPB). Using a myograft apparatus, coronary artery endothelial-dependent (Edep) and -independent (Eind) relaxation was assessed. LV performance was determined using pressure-volume loop analysis. Pulmonary interleukin (IL)-2, IL-6, and tumor necrosis factor (TNF)-α expression was measured.

Results

Weaning from CPB and LV performance after transplantation were improved in HTS-treated animals. Successful weaning from CPB was greater in the HTS-treated hearts (8 of 8 vs 2 of 8; P < .05). Mean LV functional recovery was improved in the HTS-treated animals, as assessed by preload recruitable stroke work (65 ± 10% vs 27 ± 10%; P < .001) and end-systolic elastance (55 ± 7% vs 37 ± 4%; P < .001). Treatment with HTS resulted in improved Edep (mean maximum elastance [Emax], 56 ± 5% vs 37 ± 7%; P < .001) and Eind (mean Emax%, 77 ± 6% vs 52 ± 4%; P < .001) vasorelaxation compared with control. Pulmonary expression of IL-2, IL-6, and TNF-α increased following transplantation, whereas HTS therapy attenuated IL production (P < .001). Transplantation increased plasma TNF-α levels and LV TNF-α expression, whereas HTS prevented this up-regulation (P < .001).

Conclusions

Recipient HTS pretreatment preserves allograft vasomotor and LV function, and HTS therapy limits CPB-induced injury. HTS may be a novel recipient intervention to prevent graft dysfunction.  相似文献   
39.

Background

Etomidate is frequently selected over propofol for induction of anaesthesia because of a putatively favourable haemodynamic profile, but data confirming this perception are limited.

Methods

Patients undergoing cardiac surgery were randomised to induction of anaesthesia with propofol or etomidate. Phase I (n=75) was conducted as open-label, whereas Phase II (n=75) was double blind. Mean arterial blood pressure (MAP) and boluses of vasopressor administered after induction were recorded. The primary endpoint was the area under the curve below baseline MAP (MAP-time integral) during the 10 min after induction. Secondary endpoints were the use of vasopressors over the same period, and the effect of blinding on the aforementioned endpoints. Groups were compared using regression models with phase and anaesthetist as factors.

Results

The mean difference between etomidate and propofol in the MAP-time integral below baseline was 2244 mm Hg s (95% confidence interval, 581–3906; P=0.009), representing a 34% greater reduction with propofol. Overall, vasopressors were used in 10/75 patients in the etomidate group vs 21/75 in the propofol group (P=0.38), and in 20/74 patients during the blinded phase vs 11/76 during the open-label phase (P=0.31). The interaction between randomisation and phase (open-labelled or blinded) was not significant for either primary (P=0.73) or secondary endpoints (P=0.90).

Conclusions

Propofol caused a 34% greater reduction in MAP-time integral from baseline after induction of anaesthesia than etomidate, despite more frequent use of vasopressors with propofol, confirming the superior haemodynamic profile of etomidate in this context. The proportion of patients receiving vasopressors increased slightly, albeit not significantly, in both groups in the blinded phase.

Clinical trial registration

Australian and New Zealand Clinical Trials Registry, ACTRN12614000717651.  相似文献   
40.

Background

Acute myocardial infarction (AMI) causes irreversible myocardial damage and release of inflammatory mediators, including cytokines, chemokines and miRNAs. We aimed to investigate changes in the levels of cytokines (IL-6, TNF-α and IL-10), miRNAs profiles (miR-146 and miR-155) and distribution of different monocyte subsets (CD14++CD16-, CD14++CD16+, CD14+CD16++) in the acute and post-healing phases of AMI.

Methods

In eighteen consecutive AMI patients (mean age 56.78?±?12.4 years, mean left ventricle ejection fraction – LVEF: 41.9?±?9.8%), treated invasively, monocyte subsets frequencies were evaluated (flow cytometry), cytokine concentrations were analyzed (ELISA) as well as plasma miRNAs were isolated twice – on admission and after 19.2?±?5.9 weeks of follow-up. Measurements were also performed among healthy volunteers.

Results

AMI patients presented significantly decreased frequencies of classical cells in comparison to healthy controls (median 71.22% [IQR: 64.4–79.04] vs. 84.35% [IQR: 81.2–86.7], p?=?0.001) and higher percent of both intermediate and non-classical cells, yet without statistical significance (median 6.54% [IQR: 5.14–16.64] vs. 5.87% [IQR: 4.48–8.6], p?=?0.37 and median 5.99% [IQR: 3.39–11.5] vs. 5.26% [IQR: 3.62–6.2], p?=?0.42, respectively). In AMI patients both, analyzed plasma miRNA concentrations were higher than in healthy subjects (miR-146: median 5.48 [IQR: 2.4–11.27] vs. 1.84 [IQR: 0.87–2.53], p?=?0.003; miR-155: median 25.35 [IQR: 8.17–43.15] vs. 8.4 [IQR: 0.08–16.9], p?=?0.027, respectively), and returned back to the values found in the control group in follow-up. miR-155/miR-146 ratio correlated with the frequencies of classical monocytes (r=0.6, p?=?0.01) and miR-155 correlated positively with the concentration of inflammatory cytokines ? IL-6 and TNF-α.

Conclusions

These results may suggest cooperation of both pro-inflammatory and anti-inflammatory signals in AMI in order to promote appropriate healing of the infarcted myocardium.  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