首页 | 官方网站   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   46869篇
  免费   2410篇
  国内免费   385篇
医药卫生   49664篇
  2023年   322篇
  2022年   294篇
  2021年   1533篇
  2020年   842篇
  2019年   1175篇
  2018年   1619篇
  2017年   1069篇
  2016年   1183篇
  2015年   1371篇
  2014年   1874篇
  2013年   2484篇
  2012年   3767篇
  2011年   3719篇
  2010年   2099篇
  2009年   1830篇
  2008年   3173篇
  2007年   3279篇
  2006年   3041篇
  2005年   3043篇
  2004年   2742篇
  2003年   2463篇
  2002年   2174篇
  2001年   332篇
  2000年   241篇
  1999年   353篇
  1998年   401篇
  1997年   353篇
  1996年   308篇
  1995年   308篇
  1994年   241篇
  1993年   176篇
  1992年   186篇
  1991年   136篇
  1990年   140篇
  1989年   118篇
  1988年   98篇
  1987年   77篇
  1986年   94篇
  1985年   91篇
  1984年   89篇
  1983年   81篇
  1982年   98篇
  1981年   70篇
  1980年   76篇
  1979年   42篇
  1978年   53篇
  1977年   43篇
  1976年   39篇
  1974年   36篇
  1973年   32篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
To analyse if a four-drug combination including two protease inhibitors (PIs) accelerates viral decay and suppression as compared with standard triple therapy in heavily immunosuppressed HIV-1 infected patients, an open label clinical trial was designed. PIs naive patients receiving their first highly active antiretroviral therapy were included if their CD4 cell count was lower than 200/mm3 and their HIV viral load (VL) >100,000 RNA copies/mL. Every patient received two analogues and was randomized in two groups receiving either one PI (saquinavir soft gel capsule) or two PIs (saquinavir + nelfinavir). Viral efficacy (VL <50), time to reach VL <50, viral clearance rate constant and plasmatic elimination half-life were determined. In all, 30 patients were enrolled. No viral variable was significatively improved by the four-drug combination in the short term. No clinical benefit should be expected with a four-drug (two PIs) regimen in patients with low CD4+ cell count and high VL.  相似文献   
992.
993.
We evaluated the clinical effect of selective use of sirolimus-eluting stents (SESs) in real-world, high-risk patients. A total of 4,237 consecutive patients who underwent percutaneous coronary intervention (SES, n = 872, bare metal stents [BMSs], n = 3,365) was enrolled in a prospective regional survey. A prespecified high-risk subset of patients was selected on the basis of clinical and angiographic characteristics. A propensity score analysis was performed to compare patients who received SESs with those who received BMSs. Patients in the SES group more often had diabetes and more frequently had previous myocardial infarction or coronary revascularization, type C lesions, and multivessel procedures. Patients who presented with acute myocardial infarction were treated more often with BMSs. At 9 months, the use of SESs was associated with fewer major adverse cardiac events (death, myocardial infarction, or target lesion revascularization; hazard ratio 0.56, 95% confidence interval 0.37 to 0.85) and target lesion revascularizations (hazard ratio 0.43, 95% confidence interval 0.20 to 0.91). This decrease was more evident in a prespecified high-risk subgroup of patients (major adverse cardiac events, 8.0% SES vs 15.6% BMS, hazard ratio 0.45, 95% confidence interval 0.29 to 0.72). We conclude that selective SES use in real-world patients who have high-risk clinical and angiographic characteristics is associated with significant decreases in major adverse cardiac events and repeat revascularizations compared with BMS use.  相似文献   
994.
The etiology of refractory celiac sprue (RCS) is unclear. In a high proportion of cases, the clonal nature of intestinal intraepithelial lymphocytes (IEL) can be demonstrated and a pathogenetic implication of intestinal IEL has been postulated. The prognosis of this subgroup of RCS is poor, with a high risk to develop an overt lymphoma and uncontrolled malabsorption despite steroid/immunosuppressive therapy. Cases with a relatively indolent clinical course, however, exist and their early diagnosis may be difficult. To gain insight into the pathogenic implication of intestinal IEL in refractory celiac sprue, we have performed an extensive phenotypic and functional characterization of clonal intestinal IEL in a patient with an indolent form of refractory celiac sprue, using multiparametric flow cytometry. The abnormal lymphocyte infiltrate lacked surface membrane expression of CD3/T-cell receptor (TCR) complexes (TCR(-), CD4(-), CD8(-), sCD3(-)), but contained intracellular CD3(epsilon) (CyCD3(+)) and surface CD103(+) and CD7(+). In particular, these cells showed a unique spontaneous ex-vivo cytokine secretion profile with an increased percentage of CD3(-) IEL containing TNF-alpha and IL-10, in the absence of IL-2, IL-4 and IFN-gamma. Altogether our results suggest that flow cytometry immunophenotyping of intestinal IEL, in cases suspected of celiac disease and their complicated forms, could be of great help in the correct diagnosis of RCS and the understanding of the immunopathogenic mechanisms of the disease and their clinical and/or therapeutical implications.  相似文献   
995.
Limited information is available on the efficacy of cryoablation in the coronary venous system in humans. A patient with a lateral accessory pathway was referred to our center after several unsuccessful endocardial and epicardial (within the coronary sinus) attempts using standard radiofrequency energy. Ablation was subsequently performed successfully by applying cryoenergy distally into the coronary sinus, using a temperature of -50 degrees C and a freezing application time of 45 s. There were no complications. Angiography of the left coronary circumflex artery and coronary venous system was performed at 12 months follow-up using cardiac multislice computed tomography, and no coronary stenosis or anatomic anomaly was found. Neither pre-excitation or any arrhythmia recurred during follow-up. This experience suggests that ablating in the distal coronary sinus can be safely performed using cryoenergy.  相似文献   
996.
Objectives. We sought to compare myocardial contrast echocardiography with low dose dobutamine echocardiography for predicting 1-month recovery of ventricular function in acute myocardial infarction treated with primary coronary angioplasty.

Background. The relation between myocardial perfusion and contractile reserve in patients with acute myocardial infarction, in whom anterograde flow is fully restored without significant residual stenosis, is still unclear.

Methods. Thirty patients with acute myocardial infarction treated successfully with primary coronary angioplasty underwent intracoronary contrast echocardiography before and after angioplasty and dobutamine echocardiography 3 days after the index infarction. One month later, two-dimensional echocardiography and coronary angiography were repeated in all patients and contrast echocardiography in 18 patients.

Results. After coronary recanalization, 26 patients showed myocardial reperfusion within the risk area, although 4 did not. At 1-month follow-up, all patients had a patent infarct-related artery without significant restenosis. Both left ventricular ejection fraction and wall motion score index within the risk area significantly improved in the patients with reperfusion ([mean ± SD] 38 ± 8% vs. 48 ± 12%, p < 0.005; and 2.35 ± 0.5 vs. 2 ± 0.6, p < 0.001, respectively), but not in those with no reflow. Of the 72 nonperfused segments before angioplasty, 27 showed functional improvement at follow-up. Myocardial contrast echocardiography had a sensitivity and a negative predictive value similar to dobutamine echocardiography in predicting late functional recovery (96% vs. 89% and 89% vs. 93%, respectively), but a lower specificity (18% vs. 91%, p < 0.001), positive predictive value (41% vs. 86%, p < 0.001) and overall accuracy (47% vs. 90%, p < 0.001).

Conclusions. Microvascular integrity is a prerequisite for myocardial viability after acute myocardial infarction. However, contrast enhancement shortly after recanalization does not necessarily imply a late functional improvement. Thus, contractile reserve elicited by low dose dobutamine is a more accurate predictor of regional functional recovery after reperfused acute myocardial infarction than microvascular integrity.

(J Am Coll Cardiol 1996;28:1677–83)>  相似文献   

997.
ObjectivesThe aim of this study was to define predictors of prosthesis-patient mismatch (PPM) and its impact on mortality after transcatheter aortic valve replacement (TAVR) with self-expandable valves (SEVs) in patients with small annuli.BackgroundTAVR seems to reduce the risk for PPM compared with surgical aortic valve replacement, especially in patients with small aortic annuli. Nevertheless, predictors and impact of PPM in this population have not been clarified yet.MethodsPredictors of PPM and all-cause mortality were investigated using multivariable logistic regression analysis from the cohort of the TAVI-SMALL (International Multicenter Registry to Evaluate the Performance of Self-Expandable Valves in Small Aortic Annuli) registry, which included patients with severe aortic stenosis and small annuli (annular perimeter <72 mm or area <400 mm2 on computed tomography) treated with transcatheter SEVs: 445 patients with (n = 129) and without (n = 316) PPM were enrolled.ResultsIntra-annular valves conferred increased risk for PPM (odds ratio [OR]: 2.36; 95% confidence interval [CI]: 1.16 to 4.81), while post-dilation (OR: 0.46; 95% CI: 0.25–0.84) and valve oversizing (OR: 0.53; 95% CI: 0.28–1.00) seemed to protect against PPM occurrence. At a median follow-up of 354 days, patients with severe PPM, but not those with moderate PPM, had a higher all-cause mortality rate compared with those without PPM (log-rank p = 0.008). Multivariable Cox regression confirmed severe PPM as an independent predictor of all-cause mortality (hazard ratio: 4.27; 95% CI: 1.34 to 13.6).ConclusionsAmong patients with aortic stenosis and small aortic annuli undergoing transcatheter SEV implantation, use of intra-annular valves yielded higher risk for PPM; conversely, post-dilation and valve oversizing protected against PPM occurrence. Severe PPM was independently associated with all-cause mortality.  相似文献   
998.
BACKGROUND: Few studies have assessed the relationship between ambulatory blood pressure (BP) and cardiac damage in essential hypertensive patients with inverse white coat hypertension (IWCH). OBJECTIVES: To determine the frequency of IWCH in untreated grade 1-2 hypertension and to assess possible differences in cardiac damage among patients with IWCH, white coat hypertension (WCH) and the rest of patients with grade 1-2 hypertension. PATIENTS AND METHODS: Two hundred and eleven patients with grade 1-2 hypertension were sequentially included. A good quality 24-h ambulatory BP monitoring was obtained in 204 patients (age: 41 +/- 12 years, 56% males). IWCH was defined as a daytime systolic and/or diastolic BP higher than diagnostic office systolic and/or diastolic BP, respectively. WCH was defined as a daytime BP < 135/85 mmHg. A good quality echocardiogram was obtained in 174 patients. We considered left ventricular hypertrophy a left ventricular mass index (LVMI) > or = 125 g/m2. RESULTS: We found IWCH in 29 subjects (14%), and WCH in 68 (33%). Office BP in patients with IWCH was in an intermediate position between WCH and the rest of grade 1-2 hypertension patients. The IWCH patients showed 24-h, daytime and night-time BP higher than the other groups. Left ventricular mass was significantly greater in patients with IWCH than in the other grade 1-2 hypertension patients after adjusting for age, gender, body mass index, smoking and office BP (regression coefficient 28.14, 95%CI: 7.36-48.91). CONCLUSION: IWCH is independently associated with higher values of left ventricular mass in patients with grade 1-2 hypertension.  相似文献   
999.
Urinary incontinence is a common problem in older subjects, very often wrongfully accepted as a normal part of the aging process. A total of 520 subjects (208 males and 312 females; mean age 74.8 +/- 11.8 years), from both private- and nursing-home dwelling populations, were included in this study aimed to estimate the incidence of urinary incontinence and identify factors associated with condition, in aged subjects. The incidence and type of urinary incontinence (stress, urge or mixed incontinence) were assessed by structured questionnaires and diagnosis was confirmed by a seven-day consecutive voiding diary. Assessment of physical, cognitive and emotional functions was performed on each subject using the Mini Mental State Examination (MMSE), Instrumental Activities of Daily Living Scale (IADL), Tinetti Scale (gait), Tinetti Scale (balance) and Geriatric Depression Scale (GDS) instruments. In the total population sample the incidence of urinary incontinence was 47.9%. The incontinence cases were classified, according to the different types, as: stress incontinence (males: 3.4%; females: 8.7%; males+females: 6.5%); urge incontinence (males: 27.4%; females: 31.4%; males+females: 29.8%); mixed incontinence (males: 20.2%; females: 5.8%; males+females: 11.5%). In the total population sample, no significant relationship was found between age and prevalence of urinary incontinence. In the elderly female group, age significantly correlated in a direct manner with urge incontinence (P<0.01) and inversely with stress incontinence (P<0.001). Only in the male sex group age significantly correlated with mixed incontinence (P<0.005). Multiple linear regression analysis showed that the dependent variable 'incontinence' could be predicted by MMSE (P<0.001) in the male sex group and by the Tinetti Scale (gait) (P<0.001) in the female sex group.  相似文献   
1000.
OBJECTIVE: Chromogranin A (CgA) is an acidic glycoprotein co-stored in vesicles and co-released with catecholamines. Although currently used as a humoral marker of endocrine tumours, several aspects of CgA secretion still need to be clarified in humans. PATIENTS: Fifty-four controls, 83 essential hypertensive and six adrenalectomized patients were studied. DESIGN: In the controls and hypertensive patients, CgA and catecholamines were measured before (supine position) and after changes in posture (2' upright position), insulin-induced hypoglycaemia (0.15 IU/kg i.v.) and glucagon injection (1 mg i.v.). In addition, blood samples were taken in the morning (0800 h) and in the afternoon (1800 h), and every 5 h for 24 h. In the adrenalectomized patients, blood samples were obtained in the morning and in the afternoon. MEASUREMENTS: CgA was measured by an immunoradiometric assay, and noradrenaline and adrenaline by high-performance liquid chromatography. RESULTS: In controls, posture slightly increased plasma catecholamines without affecting CgA levels. Hypoglycaemia evoked a rise in noradrenaline (P < 0.04), adrenaline (P < 0.01) and CgA (79.6 +/- 11.8 vs. 46.1 +/- 10.1 microg/l, P < 0.03). Glucagon injection increased plasma adrenaline (P < 0.01) but not noradrenaline or CgA levels. At variance with blood pressure and catecholamines, CgA increased significantly in the afternoon (51.1 +/- 4.0 vs. 45.0 +/- 3.9 microg/l, P < 0.05); it also had a circadian rhythm, with peak values during the night (at 2300 h, 65.4 +/- 9.0 microg/l) and a nadir in the morning (at 0800 h, 43.1 +/- 6.6 microg/l). In hypertensives, basal and stimulated CgA levels as well as diurnal/circadian variations of this peptide were similar to those in normal subjects. In adrenalectomized patients plasma CgA in the morning (34.3 +/- 6.5 microg/l) was lower (P < 0.03) than in all controls and hypertensives studied, but also showed an afternoon increment (46.4 +/- 6.6 microg/l, P < 0.003). No correlation was found between CgA and catecholamines or blood pressure in all subjects or in the subgroups. CONCLUSIONS: In normal humans, chromogranin A and catecholamines are not always co-secreted, and co-secretion occurs only for marked exocytotic adrenergic stimuli, such as hypoglycaemic stress. In addition, chromogranin A has a circadian rhythm unrelated to plasma catecholamines. Basal plasma concentrations and the secretory pattern of chromogranin A in hypertensives do not differ from the findings in controls. Finally, the adrenal glands contribute partially to circulating chromogranin A and are not involved in the circadian rhythm of this peptide in humans.  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-23

京公网安备 11010802026262号