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   68073篇
  免费   5002篇
  国内免费   1496篇
耳鼻咽喉   106篇
儿科学   1859篇
妇产科学   4271篇
基础医学   4161篇
口腔科学   517篇
临床医学   8435篇
内科学   18509篇
皮肤病学   281篇
神经病学   733篇
特种医学   1059篇
外国民族医学   17篇
外科学   7065篇
综合类   11497篇
现状与发展   5篇
预防医学   3178篇
眼科学   92篇
药学   5934篇
  53篇
中国医学   3081篇
肿瘤学   3718篇
  2024年   47篇
  2023年   1065篇
  2022年   1512篇
  2021年   2763篇
  2020年   2687篇
  2019年   2401篇
  2018年   2337篇
  2017年   2324篇
  2016年   2406篇
  2015年   2455篇
  2014年   4976篇
  2013年   5216篇
  2012年   3906篇
  2011年   4495篇
  2010年   3566篇
  2009年   3494篇
  2008年   3444篇
  2007年   3484篇
  2006年   3219篇
  2005年   2949篇
  2004年   2256篇
  2003年   1954篇
  2002年   1619篇
  2001年   1496篇
  2000年   1144篇
  1999年   929篇
  1998年   724篇
  1997年   663篇
  1996年   634篇
  1995年   587篇
  1994年   553篇
  1993年   402篇
  1992年   361篇
  1991年   349篇
  1990年   295篇
  1989年   287篇
  1988年   264篇
  1987年   199篇
  1986年   163篇
  1985年   162篇
  1984年   154篇
  1983年   93篇
  1982年   98篇
  1981年   87篇
  1980年   69篇
  1979年   73篇
  1978年   53篇
  1977年   37篇
  1976年   43篇
  1974年   19篇
排序方式: 共有10000条查询结果,搜索用时 250 毫秒
21.
目的 探讨蜂巢提取物Elixir-X对自然衰老及辐射衰老小鼠的影响,为Elixir-X的进一步研发提供药理学基础。方法 采用小鼠肝脏切除术建立自然衰老小鼠模型,将其分为空白对照组、Elixir-X组、白藜芦醇组及模型组,连续给药7 d后,检测小鼠70%肝脏切除后的再生过程中,衰老细胞、肝脏功能恢复与肝脏再生的变化,观察Elixir-X对自然衰老的影响;采用60CO辐射法建立辐射衰老小鼠模型,将其分为模型组、空白对照组、白藜芦醇组、Elixir-X高、低剂量组,通过检测小鼠肠隐窝干细胞再生、小肠绒毛结构以及衰老细胞的变化,对比不同剂量Elixir-X对辐射后衰老的影响。结果 在肝脏切除术的小鼠模型中,Elixir-X组的肝功能水平明显低于模型组的肝脏自然再生小鼠,显著促进了肝功能恢复(P<0.05);同时与模型组相比,Elixir-X组清除了肝脏切除后再生过程中产生的衰老细胞(P<0.05),Ki-67的着色斑块明显增加,促进肝脏的再生,且肝血窦的扫描电镜影像结果中Elixir-X组肝血窦再生加快。60CO辐照小鼠模型中,与模型组相比,Elixir-X组有效促进辐照后肝脏功能恢复(P<0.05),Elixir-X高剂量组体重也恢复到正常水平,与空白对照组无显著差异;与模型组相比,Elixir-X低剂量组小肠的β-Gal着色细胞减少,Elixir-X高剂量组甚至能更有效地减少衰老细胞(P<0.05);小肠HE染色的结果中,Elixir-X组小肠绒毛结构得到恢复;Ki-67的IHC染色中,与模型组相比,Elixir-X组着色板块更多,且着色区域都在肠隐窝干细胞位置。结论 Elixir-X能有效清除肝脏切除术引起的自然衰老与辐射引起的损伤性衰老细胞,对衰老具有显著地抑制作用。  相似文献   
22.
ObjectiveTo investigate the feasibility of transnasal heated humidified high flow nasal cannula oxygen therapy (HFNC) in the treatment of acute exacerbation of chronic obstructive pulmonary disease (AECOPD) with respiratory failure in elderly patients. MethodsA total of 176 elderly patients with AECOPD complicated with respiratory failure who were hospitalized at Peking University Shougang Hospital from December 2016 to January 2022 were enrolled, including 82 patients in an HFNC group and 94 patients in an NPPV group. After treatment, pulse oxygen saturation (SPO2), arterial partial pressure of carbon dioxide (PaCO2), oxygenation index (OI), respiratory rate (RR), heart rate (HR), mean arterial pressure (MAP), comfort score, discharge rate, rate of endotracheal intubation, rate of transfer to intensive care unit (ICU), and mortality were compared between the two groups. The independent sample t-test was used for comparison between the two groups. Statistical data are expressed in percentage or number of cases and the χ2 test was used for their comparisons. ResultsThe SPO2 values at 30 min, 1 h, and 6 h were significantly higher in the HFNC group than in the NPPV group (t=-2.049,-2.618, and -3.314, P=0.043, 0.010, and 0.001, respectively). SPO2 before discharge was significantly lower than that of the NPPV group (t=2.162, P=0.033), but OI at each time point and before discharge had no statistical significance (P>0.05). MAP at 6 h was significantly higher in the HFNC group than in the NPPV group (t=-2.209, P=0.029), but within the normal range. HRs at 2 h and 3 h in the HFNC group were significantly higher than those of the NPPV group (t=-2.199 and -2.336, P=0.030 and 0.021, respectively). There were no significant differences in RR, HR, or MAP between the two groups at other time points and before discharge (P>0.05). There was no significant difference in PaCO2 between the two groups (P>0.05). Comfort score in the HFNC group was significantly higher than that of the NPPV group (t=-46.807, P<0.001). There were no significant differences in discharge rate, ICU transfer rate, endotracheal intubation rate, and mortality between the two groups (P>0.05). ConclusionHFNC is as effective as NPPV in treating elderly patients with AECOPD complicated with type Ⅰ or mild type Ⅱ respiratory failure, and HFNC is more comfortable than NPPV.  相似文献   
23.
24.
ObjectiveThe objective of this feasibility study was to examine the implementation and usefulness of an intervention for extremely premature infant (EPI) caregivers.ResultsOne caregiver and five nurses provided feedback with a mean score of 4.4 out of 5 pertaining to helpfulness.ConclusionsImplementation of the Caregiver's Guide was feasible and was positively received by NICU nurses and caregivers. We recommend implementing a revised version of this tool based on nurse and caregiver feedback. The delivery of education should be divided between dayshift and nightshift nurses so that one nurse is not responsible for providing all the information. The education should be categorized by gestational age and day of life and only given when it is pertinent to the care of the child. A section should be added to include a quick reference guide for the medical jargon used in the NICU.  相似文献   
25.
Hepatitis E virus (HEV) is the most common cause of acute liver failure (LF) and one of the most common factors causing acute injury in acute-on-chronic LF (ACLF). When HEV-related LF occurs, a series of changes take place in both the intrahepatic environment and extrahepatic microenvironment. The changed types and distribution of immune cells (infiltrating macrophages and increased lymphocytes) in liver tissue, as well the increased proinflammatory cytokines and chemokines in the blood, indicate that the occurrence and progression of HEV-related LF are closely related to immune imbalance. The clinical features and immune reaction in the body during HEV-related acute LF (ALF) and ACLF are complicated. This review highlights recent progress in elucidating the clinical manifestations of HEV-associated ALF and ACLF and discusses the corresponding systemic immune changes and possible regulatory mechanisms.  相似文献   
26.
BackgroundCoronary artery bypass grafting (CABG) improves survival in patients with heart failure and severely reduced left ventricular systolic function (LVEF). Limited data exist regarding adverse cardiovascular event rates after CABG in patients with heart failure with midrange ejection fraction (HFmrEF; LVEF > 40% and < 55%).MethodsWe analyzed data on isolated CABG patients from the Veterans Affairs national database (2010-2019). We stratified patients into control (normal LVEF and no heart failure), HFmrEF, and heart failure with reduced LVEF (HFrEF) groups. We compared all-cause mortality and heart failure hospitalization rates between groups with a Cox model and recurrent events analysis, respectively.ResultsIn 6533 veterans, HFmrEF and HFrEF was present in 1715 (26.3%) and 566 (8.6%) respectively; the control group had 4252 (65.1%) patients. HFrEF patients were more likely to have diabetes mellitus (59%), insulin therapy (36%), and previous myocardial infarction (31%). Anemia was more prevalent in patients with HFrEF (49%) as was a lower serum albumin (mean, 3.6 mg/dL). Compared with the control group, a higher risk of death was observed in the HFmrEF (hazard ratio [HR], 1.3 [1.2-1.5)] and HFrEF (HR, 1.5 [1.2-1.7]) groups. HFmrEF patients had the higher risk of myocardial infarction (subdistribution HR, 1.2 [1-1.6]; P = .04). Risk of heart failure hospitalization was higher in patients with HFmrEF (HR, 4.1 [3.5-4.7]) and patients with HFrEF (HR, 7.2 [6.2-8.5]).ConclusionsHeart failure with midrange ejection fraction negatively affects survival after CABG. These patients also experience higher rates myocardial infarction and heart failure hospitalization.  相似文献   
27.

Background

Glutamate plays a key role for post-ischaemic recovery of myocardial metabolism. According to post hoc analyses of the two GLUTAMICS trials, patients without diabetes benefit from glutamate with less myocardial dysfunction after coronary artery bypass surgery (CABG). Copeptin reflects activation of the Arginine Vasopressin system and is a reliable marker of heart failure but available studies in cardiac surgery are limited. We investigated whether glutamate infusion is associated with reduced postoperative rises of plasma Copeptin (p-Copeptin) after CABG.

Methods

A prespecified randomised double-blind substudy of GLUTAMICS II. Patients had left ventricular ejection fraction ≤0.30 or EuroSCORE II ≥3.0 and underwent CABG ± valve procedure. Intravenous infusion of 0.125 M L-glutamic acid or saline at 1.65 mL/kg/h was commenced 10–20 min before the release of the aortic cross-clamp and then continued for another 150 min P-Copeptin was measured preoperatively and postoperatively on day one (POD1) and day three. The primary endpoint was an increase in p-Copeptin from the preoperative level to POD1. Postoperative stroke ≤24 h and mortality ≤30 days were safety outcomes.

Results

We included 181 patients of whom 48% had diabetes. The incidence of postoperative mortality ≤30 days (0% vs. 2.1%; p = .50) and stroke ≤24 h (0% vs. 3.2%; p = .25) did not differ between the glutamate group and controls. P-Copeptin increased postoperatively with the highest values recorded on POD1 without significant inter-group differences. Among patients without diabetes, p-Copeptin did not differ preoperatively but postoperative rise from preoperative level to POD1 was significantly reduced in the glutamate group (73 ± 66 vs. 115 ± 102 pmol/L; p = .02). P-Copeptin was significantly lower in the Glutamate group on POD1 (p = .02) and POD 3 (p = .02).

Conclusions

Glutamate did not reduce rises of p-Copeptin significantly after moderate to high-risk CABG. However, glutamate was associated with reduced rises of p-Copeptin among patients without diabetes. These results agree with previous observations suggesting that glutamate mitigates myocardial dysfunction after CABG in patients without diabetes. Given the exploratory nature of these findings, they need to be confirmed in future studies.  相似文献   
28.
卵巢过度刺激综合征是辅助生殖技术常见的并发症,通常在排卵后2周或2周以上发生。然而自发性卵巢过度刺激综合征极其罕见,一些病例报道表明,自发性卵巢过度刺激综合征的发生与卵泡刺激素受体突变、高人绒毛膜促性腺激素水平、高促甲状腺激素水平、促性腺激素垂体腺瘤等有关。现报告1例双胎妊娠合并自发性卵巢过度刺激综合征的病例,并进一步探讨自发性卵巢过度刺激综合征的可能病因、诊断和治疗原则。  相似文献   
29.
30.
目的探析西地兰联合胺碘酮治疗急诊重症心衰合并快速性心律失常患者的临床效果。方法60例急诊重症心衰合并快速性心律失常患者,以电脑Excel表格按照1∶1比例分为对比组和研究组,每组30例,对比组患者采用西地兰治疗,研究组患者采用西地兰联合胺碘酮治疗。比较两组患者治疗前后QT离散度、心功能指标及治疗后临床指标。结果治疗后,两组患者QT离散度均较本组治疗前降低,且研究组患者QT离散度(32.69±2.69)ms低于对比组的(41.32±3.11)ms,差异具有统计学意义(P<0.05)。治疗后,研究组患者心室率(78.51±5.17)次/min低于对比组的(94.23±6.67)次/min,起效时间(18.23±2.11)min短于对比组的(32.11±3.51)min,窦性心律转复率93.33%(28/30)高于对比组的70.00%(21/30),差异具有统计学意义(P<0.05)。治疗后,两组患者左室舒张末期内径、室间隔厚度、左室后壁厚度、左室重量指数、左室射血分数、舒张早期最大流速/舒张晚期最大流速(E/A)、N末端B型脑钠肽前体(NT-proBNP)水平均较本组治疗前改善,且研究组优于对比组,差异具有统计学意义(P<0.05)。结论在急诊重症心衰合并快速性心律失常患者治疗中选择西地兰联合胺碘酮用药方案,能够更好降低QT离散度,提高窦性心律转复率,且心室率更低、起效时间更短,同时,在改善心功能方面效果较显著。  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