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   2819篇
  免费   135篇
  国内免费   25篇
耳鼻咽喉   23篇
儿科学   114篇
妇产科学   97篇
基础医学   319篇
口腔科学   271篇
临床医学   223篇
内科学   549篇
皮肤病学   63篇
神经病学   171篇
特种医学   182篇
外科学   322篇
综合类   43篇
预防医学   266篇
眼科学   11篇
药学   194篇
中国医学   24篇
肿瘤学   107篇
  2023年   18篇
  2022年   35篇
  2021年   86篇
  2020年   55篇
  2019年   83篇
  2018年   94篇
  2017年   62篇
  2016年   64篇
  2015年   99篇
  2014年   113篇
  2013年   141篇
  2012年   175篇
  2011年   187篇
  2010年   131篇
  2009年   111篇
  2008年   132篇
  2007年   142篇
  2006年   124篇
  2005年   100篇
  2004年   73篇
  2003年   75篇
  2002年   85篇
  2001年   46篇
  2000年   53篇
  1999年   49篇
  1998年   58篇
  1997年   51篇
  1996年   51篇
  1995年   25篇
  1994年   41篇
  1993年   32篇
  1992年   40篇
  1991年   26篇
  1990年   29篇
  1989年   34篇
  1988年   25篇
  1987年   38篇
  1986年   25篇
  1985年   15篇
  1984年   16篇
  1983年   14篇
  1982年   15篇
  1981年   12篇
  1980年   14篇
  1977年   16篇
  1976年   10篇
  1975年   10篇
  1970年   8篇
  1967年   4篇
  1964年   5篇
排序方式: 共有2979条查询结果,搜索用时 0 毫秒
41.
OBJECTIVES: To compare the short-term prognosis of patients with severe acute rheumatic carditis when treated with an intravenous pulse of methylprednisolone in comparison with conventional treatment using oral prednisone. METHODS: We designed a randomized clinical trial in the setting of a university general hospital in Brazil. We randomly allocated 18 patients with the diagnosis of severe acute rheumatic carditis and congestive heart failure to receive an intravenous pulse as opposed to oral prednisolone. Methylprednisolone was administered in a dose of 1 g intravenously for 3 consecutive days in the first and second weeks, for two days in the third, and one day in the fourth week. Prednisone was administered in a dose of 1.5 mg/kg/day over the period of 4 weeks. RESULTS: The mean age of the patients was 11.1 +/- 3.7 years, with a median of 12 years. Patients on oral treatment showed a more pronounced decrease in the heart rate, sedimentation rate, and in the titres of C-reactive protein than those receiving intravenous therapy. At the end of treatment, a mild decrease in the left ventricular end-systolic dimension was found in those having oral treatment, compared to an increase in the group having intravenous treatment (p = 0.036). The ejection fraction showed a median increase of 5% in those undergoing oral treatment, and a median decrease of 6% in the group with intravenous therapy (p = 0.009). There were 5 therapeutic failures in those receiving intravenous therapy (56%), including 1 death. Therapeutic failures were not observed in those treated orally (p = 0.03). CONCLUSION: Intravenous treatment of methylprednisolone, as a single anti-inflammatory agent, was inferior to conventional treatment with oral prednisone in the control of severe rheumatic carditis.  相似文献   
42.
Accurate noninvasive tests for diagnosing Helicobacter pylori infection in very young children are strongly required. We investigated the agreement between the [13C]urea breath test ([13C]UBT) and a monoclonal ELISA (HpSA) for detection of H. pylori antigen in stool. From October 2007 to July 2011, we enrolled 414 infants (123 from Brazil and 291 from Peru) of ages 6 to 30 months. Breath and stool samples were obtained at intervals of at least 3 months from Brazilian (n = 415) and Peruvian (n = 908) infants. [13C]UBT and stool test results concurred with each other in 1,255 (94.86%) cases (kappa coefficient = 0.90; 95% confidence interval [CI] = 0.87 to 0.92). In the H. pylori-positive group, delta-over-baseline (DOB) and optical density (OD) values were positively correlated (r = 0.62; P < 0.001). The positivity of the tests was higher (P < 0.001; odds ratio [OR] = 6.01; 95% CI = 4.50 to 8.04) in Peru (546/878; 62.2%) than in Brazil (81/377; 21.5%) and increased with increasing age in Brazil (P = 0.02), whereas in Peru it decreased with increasing age (P < 0.001). The disagreement between the test results was associated with birth in Brazil and female gender but not with age and diarrhea. Our results suggest that both [13C]UBT and the stool monoclonal test are reliable for diagnosing H. pylori infection in very young children, which will facilitate robust epidemiological studies in infants and toddlers.  相似文献   
43.
44.
Postexercise blood pressure reduction in elderly hypertensive patients   总被引:2,自引:0,他引:2  
OBJECTIVES: We sought to study: 1) the impact of hemodynamic and left ventricular function on short-term postexercise blood pressure reduction in elderly hypertensive patients; and 2) the 22-h postexercise effects on ambulatory blood pressure in elderly hypertensive patients. BACKGROUND: Although early exercise provokes postexercise blood pressure reduction, the mechanisms underlying this response are not completely understood. Besides, it is unclear whether the reduction in blood pressure after exercise lasts long enough to have clinical relevance in elderly hypertensive patients. METHODS: We studied 24 elderly hypertensive patients (age 68.9 +/- 1.5 years) and 18 age-matched normotensive control subjects (age 68.1 +/- 1.2 years). Cardiac output (carbon dioxide rebreathing) and blood pressure (auscultatory) were measured at rest and after a 45-min period of low-intensity bicycle exercise (50% maximal oxygen uptake) and at 15, 30, 60 and 90 min after exercise. Left ventricular function (by Doppler echocardiography) was also evaluated. Ambulatory blood pressure monitoring was evaluated after 45 min of exercise or 45 min of rest, in a randomized order. RESULTS: In the hypertensive patients, exercise provoked a significant reduction in blood pressure, cardiac output, stroke volume and left ventricular end-diastolic volume. It also provoked a significant reduction in systolic, mean and diastolic blood pressure during a 22-h period, at daytime and nighttime. CONCLUSIONS: The short-term reduction in blood pressure after exercise in elderly hypertensive patients is associated with a decrease in stroke volume and left ventricular end-diastolic volume. The 22-h postexercise reduction in blood pressure demonstrates the clinical relevance of low-intensity exercise in elderly hypertensive patients.  相似文献   
45.

Background

Spontaneous coronary artery dissection (SCAD) is an unusual cause of acute coronary syndrome (ACS). Better recognition and diagnosis has raised awareness of this condition. However, the pathophysiology of SCAD and its prognosis are still little understood. We aimed to investigate the characteristics and prognosis of patients with SCAD, and subsequently performed a review of literature.

Methods

Single-center, retrospective study performed in patients hospitalized from January 2010 to December 2016 with suspected ACS (n=5002) whose final diagnosis was SCAD (n=27; 0.5%).

Results

Patients with SCAD were mainly female (81.5%; n=22), with median age of 56. Predisposing factors were identified in 12 (44%) patients and precipitating factors in three (11.1%). Non-ST elevation myocardial infarction (NSTEMI) was the main form of presentation (51.9%). The left anterior descending artery (LAD) territory was the most commonly involved (n=12, 44.4%). Type 2 dissection was the most prevalent angiographic pattern (n=17, 63%). The majority of patients (n=15; 55.6%) were managed medically and the remaining patients underwent percutaneous coronary intervention (PCI) with drug-eluting stents. Seven patients re-infarcted while in the hospital. Over the median follow-up period of 20 months, 7.4% of patients (n=2) had symptoms of heart failure (HF) and 14.8% developed ACS (in three patients the event occurred in a coronary territory other than that of the index case, and in one patient it occurred in the previously affected territory). There were no deaths.

Conclusion

In the studied population, SCAD was more prevalent in middle-aged women. Despite the high prevalence of in-hospital re-infarction or during follow-up, the prognosis was good overall.  相似文献   
46.
47.
48.
Calcium phosphates (CaP) are the main constituents of the mineral phase in bones and teeth and, along with calcium silicates and bioactive glasses, have been extensively investigated in remineralization of enamel and dentin. When used as ion-releasing fillers in resin-based materials, they could contribute to extend the service life of adhesive restorations, remineralize caries-affected dentin or prevent caries lesions under sealants and orthodontic brackets. However, the development of resin-based bioactive materials is not straightforward because of the several compositional variables involved in ion release. Also, CaP particles do not reinforce the material; therefore, if high mechanical properties are required, the ratio between CaP particles and reinforcing fillers must be observed. Several research groups have investigated how CaP phase, particle size and content, as well as resin matrix formulation affect remineralization, ion release kinetics and mechanical properties of these materials. This review presents an overview of the main findings reported in the literature.  相似文献   
49.
50.
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