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   36545篇
  免费   3303篇
  国内免费   903篇
耳鼻咽喉   55篇
儿科学   748篇
妇产科学   290篇
基础医学   2185篇
口腔科学   107篇
临床医学   5953篇
内科学   10592篇
皮肤病学   241篇
神经病学   1191篇
特种医学   1504篇
外国民族医学   2篇
外科学   3654篇
综合类   4395篇
现状与发展   2篇
预防医学   2187篇
眼科学   108篇
药学   5605篇
  28篇
中国医学   1067篇
肿瘤学   837篇
  2024年   73篇
  2023年   907篇
  2022年   1389篇
  2021年   2052篇
  2020年   2027篇
  2019年   1907篇
  2018年   1764篇
  2017年   1422篇
  2016年   1313篇
  2015年   1457篇
  2014年   2769篇
  2013年   2851篇
  2012年   2050篇
  2011年   2230篇
  2010年   1701篇
  2009年   1579篇
  2008年   1529篇
  2007年   1440篇
  2006年   1258篇
  2005年   1132篇
  2004年   869篇
  2003年   761篇
  2002年   608篇
  2001年   579篇
  2000年   409篇
  1999年   486篇
  1998年   419篇
  1997年   418篇
  1996年   328篇
  1995年   343篇
  1994年   313篇
  1993年   260篇
  1992年   248篇
  1991年   238篇
  1990年   195篇
  1989年   142篇
  1988年   149篇
  1987年   137篇
  1986年   128篇
  1985年   166篇
  1984年   153篇
  1983年   102篇
  1982年   72篇
  1981年   94篇
  1980年   71篇
  1979年   46篇
  1978年   42篇
  1977年   40篇
  1976年   31篇
  1975年   18篇
排序方式: 共有10000条查询结果,搜索用时 562 毫秒
991.
Context Computerized physician order entry (CPOE) with clinical decision support (CDS) has been promoted as an effective strategy to prevent the development of a drug injury defined as an adverse drug event (ADE). Objective To systematically review studies evaluating the effects of CPOE with CDS on the development of an ADE as an outcome measure. Data Sources PUBMED versions of MEDLINE (from inception through March 2007) were searched to identify relevant studies. Reference lists of included studies were also searched. Methods We searched for original investigations, randomized and nonrandomized clinical trials, and observational studies that evaluated the effect of CPOE with CDS on the rates of ADEs. The studies identified were assessed to determine the type of computer system used, drug categories being evaluated, types of ADEs measured, and clinical outcomes assessed. Results Of the 543 citations identified, 10 studies met our inclusion criteria. These studies were grouped into categories based on their setting: hospital or ambulatory; no studies related to the long-term care setting were identified. CPOE with CDS contributed to a statistically significant (P ≤ .05) decrease in ADEs in 5 (50.0%) of the 10 studies. Four studies (40.0%) reported a nonstatistically significant reduction in ADE rates, and 1 study (10.0%) demonstrated no change in ADE rates. Conclusions Few studies have measured the effect of CPOE with CDS on the rates of ADEs, and none were randomized controlled trials. Further research is needed to evaluate the efficacy of CPOE with CDS across the various clinical settings.  相似文献   
992.
冠心病心室晚电位与冠状动脉病变的关系   总被引:2,自引:0,他引:2  
为观察心室晚电位(VLP)、心律失常事件(AE)与冠状动脉病变的关系,对145例冠心病患者(心绞痛55例、陈旧性心肌梗死90例)进行信号平均心电图的定性分析和24小时Holter监测,并同期进行冠状动脉造影,并长期随访观察。119例(失访26例)随访14.1±7.1(4~36)个月,发生AE7例。VLP阳性者AE发生率25%(4/16),明显高于VLP阴性者AE的发生率2.9%(3/103),P<0.001;VLP、AE与冠状动脉病变血管的支数和狭窄程度之间均无明显关系(P均>0.05)。结果提示VLP与AE密切相关,但VLP、AE与冠状动脉病变的范围和程度无明显关系。  相似文献   
993.
Studies of enzymatically isolated myocytes from atria of young male Sprague-Dawley rats at 11 days after left coronary artery ligation show that a major response of atrial myocytes to ventricular infarction is binucleation. In sham-operated animals, 23.2% of left and 15.5% of right atrial myocytes were binucleated, compared to 77.8% of left and 40.5% of right atrial myocytes of infarcted animals. Examination of 150 g and 250 g unoperated control animals indicate that this response is occurring at a time when a small but significant amount of binucleation is also occurring as a normal part of growth. Using a Feulgen-acriflavine-SO2 method for cytofluorometry, a significant increase in ploidy was seen in left atrial myocytes of infarcted animals over those of sham or control animals. The number of left atrial myocytes in infarcted animals having a ploidy level above 3C was 10.8% above sham values. The mean length of binucleated myocytes of left atrium was significantly greater in infarcted animals (119.8 μm) than in sham-operated animals (97 μm) and the mean length of mononucleated myocytes was greater in infarcted animals (104.1 μm) than in sham-operated animals (77 μm). Thus, cardiac myocytes are capable of a substantial response to a stressful situation by increases in cell length, number of nuclei and ploidy. Study of a model system such as the rat atrium may yield an understanding of the mechanisms involved in the induction of these nuclear changes.  相似文献   
994.
OBJECTIVES: To evaluate the role of cutting balloon angioplasty in children with pulmonary artery stenosis. BACKGROUND: Pulmonary artery stenoses can be either congenital or secondary to postoperative scar formation. Isolated multiple small-vessel pulmonary artery stenoses are very rare. No surgical procedures for their treatment are currently available. METHODS: We report on four patients in whom standard and high-pressure balloon angioplasty had failed. Three of the four (2.5-, 3-, and 3.5-years-old; two girls) had isolated multiple peripheral pulmonary artery stenosis. The fourth patient was an 11-month-old girl (8 kg) with tetralogy of Fallot and hypoplastic pulmonary artery branches treated with the implantation of two stents in the pulmonary arteries. During the follow-up this patient developed severe intrastent restenosis and showed severely hypoplasic distal left pulmonary artery. RESULTS: We treated 11 vessels. The mean vessel diameter increased by 81% (P<0.0001) and RV/LV pressure ratio decreased from 1.15 to 0.75 (P=0.05). Patient treated for intrastent restenosis underwent successful complete tetralogy of Fallot repair. None of the patients suffered procedure-related complications. At a median follow-up of 18 months, results were stable and no late complications had occurred. CONCLUSIONS: Cutting balloon angioplasty is a promising technique for the treatment of highly challenging pathologies such as small vessel pulmonary artery stenoses and intrastent restenosis.  相似文献   
995.
ObjectivesThis study sought to explore the Fabry myocardium in relation to storage, age, sex, structure, function, electrocardiogram changes, blood biomarkers, and inflammation/fibrosis.BackgroundFabry disease (FD) is a rare, x-linked lysosomal storage disorder. Mortality is mainly cardiovascular with men exhibiting cardiac symptoms earlier than women. By cardiovascular magnetic resonance, native T1 is low in FD because of sphingolipid accumulation.MethodsA prospective, observational study of 182 FD (167 adults, 15 children; mean age 42 ± 17 years, 37% male) who underwent cardiovascular magnetic resonance including native T1, late gadolinium enhancement (LGE), and extracellular volume fraction, 12-lead electrocardiogram, and blood biomarkers (troponin and N-terminal pro-brain natriuretic peptide).ResultsIn children, T1 was never below the normal range, but was lower with age (9 ms/year, r = −0.78 children; r = −0.41 whole cohort; both p < 0.001). Over the whole cohort, the T1 reduction with age was greater and more marked in men (men: −1.9 ms/year, r = −0.51, p < 0.001; women: −1.4 ms/year, r = −0.47 women, p < 0.001). Left ventricular hypertrophy (LVH), LGE, and electrocardiogram abnormalities occur earlier in men. Once LVH occurs, T1 demonstrates major sex dimorphism: with increasing LVH in women, T1 and LVH become uncorrelated (r = −0.239, p = 0.196) but in men, the correlation reverses and T1 increases (toward normal) with LVH (r = 0.631, p < 0.001), a U-shaped relationship of T1 to indexed left ventricular mass in men.ConclusionsThese data suggest that myocyte storage starts in childhood and accumulates faster in men before triggering 2 processes: a sex-independent scar/inflammation regional response (LGE) and, in men, apparent myocyte hypertrophy diluting the T1 lowering of sphingolipid.  相似文献   
996.
997.
The initial therapy for postmyocardial infarction ventricular septal defects is surgical repair of the defect. Unfortunately, a significant number of patients develop recurrent ventricular septal defects (VSDs) following operative repair. Transcatheter closure offers an alternative to reoperation in these critically ill patients. We present a series of four patients in whom recurrent ventricular septal defects were closed using an Amplatzer VSD device.  相似文献   
998.
We investigated the effects of an angiotensin-converting enzyme inhibitor and an angiotensin II type 1 receptor blocker on cardiac hypertrophy in rats with renovascular hypertension. Renovascular hypertensive (Goldblatt) rats were surgically prepared from Wistar rats. Four weeks later, the rats showed a significant increase in blood pressure. At high doses, both the perindopril (1 mg/kg/day) and the candesartan (2 mg/kg/day) decreased the systolic pressure in these rats to the level of control Wistar rats. At low doses (perindopril 0.1 mg/kg/day and candesartan 0.1 mg/kg/day), these drugs lowered blood pressure to 85% of that in hypertensive rats. Echocardiographic and morphological studies revealed severe cardiac hypertrophy and fibrosis in untreated Goldblatt rats. High-dose treatment with both drugs suppressed the progression of hypertrophy and fibrosis. Also, low-dose perindopril prevented cardiac hypertrophy and fibrosis. In contrast, at the same levels of blood-pressure reduction, low-dose candesartan did not prevent cardiac fibrosis nor the upregulation of cardiac collagen types I and III mRNA observed in untreated Goldblatt rats. Atrial natriuretic peptide mRNA was up-regulated in untreated Goldblatt rats. These changes were significantly decreased by both doses of perindopril or the high dose of candesartan. Serum levels of angiotensin II and aldosterone were significantly higher in untreated Goldblatt rats. Both doses of perindopril inhibited activation of the renin-angiotensin system, whereas candesartan had weaker effects. In particular, serum aldosterone was 347 ± 20 pg/ml in low-dose perindopril versus 1796 ± 324 pg/ml in low-dose candesartan. These results suggest that there were no differences between the cardioprotective actions of perindopril and candesartan at high dosages. On the other hand, low-dose treatment with perindopril was more effective in preventing cardiac fibrosis than was low-dose treatment with candesartan, despite similar changes in blood pressure. It is possible that changes in aldosterone secretion are related to this difference.  相似文献   
999.
BackgroundPatients with out-of-hospital cardiac arrest (OHCA) due to acute coronary syndromes (ACS) who undergo percutaneous coronary intervention (PCI) are at high risk of bleeding and thrombosis. While predictive bleeding and stent thrombosis risk scores have been established, their performance in patients with OHCA has not been evaluated.MethodsAll consecutive patients admitted for OHCA due to ACS who underwent PCI between January 2007 and December 2019 were included. The ACTION and CRUSADE bleeding risk scores and the Dangas score for early stent thrombosis risk were calculated for each patient. A C-statistic analysis was performed to assess the performance of these scores.ResultsAmong 386 included patients, 82 patients (21.2%) experienced severe bleeding and 30 patients (7.8%) experienced stent thrombosis. The predictive performance of the ACTION and CRUSADE bleeding risk scores for major bleeding was poor, with areas under the curve (AUCs) of 0.596 and 0.548, respectively. Likewise, the predictive performance of the Dangas stent thrombosis risk score was poor (AUC 0.513). Using multivariable analysis, prolonged low-flow (odds ratio [OR] 1.03, 95% confidence interval [CI] 1.00–1.05; P = 0.025), reduced haematocrit or fibrinogen at admission (OR 0.93, 95% CI 0.88–0.98; P = 0.010 and OR 0.61; 95% CI 0.41–0.89; P = 0.012, respectively) and the use of glycoprotein IIb/IIIa inhibitors (OR 2.10, 95% CI 1.18–3.73; P = 0.011) were independent risk factors for major bleeding.ConclusionThe classic bleeding and stent thrombosis risk scores have poor performance in a population of patients with ACS complicated by OHCA. Other predictive factors might be more pertinent to determine major bleeding and stent thrombosis risks in this specific population.  相似文献   
1000.
《JACC: Cardiovascular Imaging》2019,12(12):2373-2385
ObjectivesThis study sought to compare the prognostic value of 2-dimensional (2D) right ventricular (RV) speckle tracking (STE) against cardiac magnetic resonance (CMR) RV ejection fraction (EF) and feature tracking (FT) and conventional echocardiographic parameters on overall and cardiovascular (CV) survival in patients with heart failure with reduced EF (HFrEF).BackgroundPrior works showed that RV systolic function predicts prognosis in HFrEF. 2D RVSTE had recently been proposed as new echocardiographic method to evaluate RV dysfunction.MethodsA total of 266 patients with HFrEF (mean LVEF 23 ± 7%, 60 ± 14 years of age; 29% women) underwent RV function assessment using CMR and 2D echocardiography and were followed for a primary endpoint of overall death and secondary endpoint of CV death.ResultsAverage CMR-RVEF was 42 ± 15%, average STE RV global longitudinal strain (STE-RVGLS) was −18.0 ± 4.9%, and average CMR-FT-RVGLS was −11.8 ± 4.3%. After a median follow-up of 4.7 years, 102 patients died, 84 of a CV cause. RVEF, FT-RVGLS, tricuspid annulus plane systolic excursion (TAPSE), fractional area change (FAC), and STE-RVGLS were significant univariate predictors of overall and cardiac death. In multivariate Cox regression, age, ischemic etiology, diabetes, New York Heart Association functional class III to IV, and beta-blocker treatment were independent clinical predictors of overall mortality. CMR-RVEF (chi-square to enter = 3.9; p < 0.05), FT-RVGLS (chi-square to enter 3.7; p = 0.05), FAC (chi-square to enter 6.2; p = 0.02), and TAPSE (chi-square to enter = 4.1; p = 0.04) provided additional prognostic value over these baseline parameters, but the additional predictive value of STE-RVGLS (chi-square to enter = 10.8; p < 0.001) was significantly (p < 0.05) higher than the other tests. Additional hazard ratio to predict overall mortality was 2.5 (95% confidence interval [CI]: 1.6 to 3.9) for STE-RVGLS <−19%, 2.15 (95% CI: 1.34 to 3.43) for TAPSE >15 mm, 1.6 (95% CI: 1.02 to 2.49) for FAC >39%, 1.93 (95% CI: 1.25 to 2.99) for RVEF >41%, and 1.87 (95% CI: 1.10 to 3.19) for CMR-FT-RVGLS <−15%.Conclusions2D RVGLS provides strong additional prognostic value to predict overall and CV mortality in HFrEF, with higher predictive value than CMR-RVEF, CMR-FT-RVGLS, TAPSE, or FAC. This supports use of STE-RVGLS to identify higher-risk HFrEF patients.  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