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   42549篇
  免费   3017篇
  国内免费   147篇
耳鼻咽喉   297篇
儿科学   1559篇
妇产科学   992篇
基础医学   4973篇
口腔科学   813篇
临床医学   4444篇
内科学   8855篇
皮肤病学   746篇
神经病学   4186篇
特种医学   1424篇
外科学   6564篇
综合类   700篇
一般理论   60篇
预防医学   3476篇
眼科学   1042篇
药学   2963篇
中国医学   41篇
肿瘤学   2578篇
  2023年   134篇
  2022年   203篇
  2021年   631篇
  2020年   404篇
  2019年   680篇
  2018年   803篇
  2017年   637篇
  2016年   648篇
  2015年   817篇
  2014年   1172篇
  2013年   1784篇
  2012年   2751篇
  2011年   2935篇
  2010年   1675篇
  2009年   1540篇
  2008年   2716篇
  2007年   2910篇
  2006年   2871篇
  2005年   2951篇
  2004年   2810篇
  2003年   2571篇
  2002年   2610篇
  2001年   461篇
  2000年   334篇
  1999年   472篇
  1998年   645篇
  1997年   487篇
  1996年   447篇
  1995年   380篇
  1994年   332篇
  1993年   334篇
  1992年   322篇
  1991年   291篇
  1990年   253篇
  1989年   235篇
  1988年   239篇
  1987年   211篇
  1986年   251篇
  1985年   237篇
  1984年   311篇
  1983年   264篇
  1982年   340篇
  1981年   294篇
  1980年   295篇
  1979年   181篇
  1978年   164篇
  1977年   168篇
  1976年   151篇
  1974年   149篇
  1973年   127篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
EUS in the management of the patient with dysplasia in Barrett's esophagus   总被引:2,自引:0,他引:2  
Barrett's esophagus is the most important risk factor in the development of adenocarcinoma of the esophagus. Barrett's esophagus is generally regarded as the most significant complication of gastroesophageal reflux disease. Adenocarcinoma occurs more frequently in the setting of high-grade dysplasia. The prognosis of adenocarcinoma of the esophagus is strongly correlated with the stage of disease. The prognosis of late stage disease is extremely poor. Cure may be achieved when disease is found at an early stage. Esophagectomy has been the definitive treatment of limited stage adenocarcinoma of the esophagus. The morbidity and mortality rate for esophagectomy is high. Therefore, alternative endoscopic methods for curative treatments have gained popularity. The two main endoscopic therapies, photodynamic therapy and endoscopic mucosal resection, are both effective when applied to early-stage disease. Traditional evaluation of the patient with Barrett's esophagus with high-grade dysplasia includes esophago-gastro-duodenoscopy (EGD) with biopsy and computed tomography of the chest. Endoscopic ultrasound (EUS) has gained popularity in the evaluation of the patient with Barrett's esophagus and high-grade dysplasia because it is the only imaging technique capable of delineating the separate histologic layers of the gastrointestinal tract. The principal role of EUS in evaluating patients with Barrett's-associated dysplasia is to identify patients who may be candidates for endoscopic ablative (endoscopic mucosal resection, photodynamic therapy) therapies. EUS has been shown to be superior to computed tomography (including high resolution spiral CT) or magnetic resonance imaging for preoperative staging in patients with high-grade dysplasia and carcinoma. This review of the literature summarizes the ability of EUS to evaluate patients with Barrett's esophagus and high-grade dysplasia.  相似文献   
992.
BACKGROUND: Mediastinal masses represent a diagnostic challenge because of their proximity to numerous critical structures, difficulty of access for tissue sampling, and myriad potential pathologic etiologies. A large, single-center experience with EUS-guided fine-needle aspiration (EUS-FNA) in the diagnosis of non-lung cancer-related mediastinal masses is presented. METHODS: An EUS database was reviewed and all cases of mediastinal mass or lymphadenopathy encountered between 1994 and 1999 were included. Final diagnoses were determined by EUS-FNA cytology and clinical follow-up. RESULTS: Forty-nine patients were identified (27 women, 22 men; mean age 58.1 years, range 30-89 years). A malignant process was diagnosed in 22 cases (45%) and a benign process in 24 (49%). The EUS-FNA specimen was nondiagnostic in 3 cases (6%). An accurate diagnosis was made in 46 of the 49 patients (94%). No complication was noted. CONCLUSIONS: EUS-FNA is a minimally invasive technique that facilitates detection and tissue sampling of mediastinal masses. It is a safe procedure that can be performed with the patient under conscious sedation in an outpatient setting.  相似文献   
993.
994.
Diastolic heart failure (DHF) currently accounts for more than 50% of all heart failure patients. DHF is also referred to as heart failure with normal left ventricular (LV) ejection fraction (HFNEF) to indicate that HFNEF could be a precursor of heart failure with reduced LVEF. Because of improved cardiac imaging and because of widespread clinical use of plasma levels of natriuretic peptides, diagnostic criteria for HFNEF needed to be updated. The diagnosis of HFNEF requires the following conditions to be satisfied: (i) signs or symptoms of heart failure; (ii) normal or mildly abnormal systolic LV function; (iii) evidence of diastolic LV dysfunction. Normal or mildly abnormal systolic LV function implies both an LVEF > 50% and an LV end-diastolic volume index (LVEDVI) <97 mL/m(2). Diagnostic evidence of diastolic LV dysfunction can be obtained invasively (LV end-diastolic pressure >16 mmHg or mean pulmonary capillary wedge pressure >12 mmHg) or non-invasively by tissue Doppler (TD) (E/E' > 15). If TD yields an E/E' ratio suggestive of diastolic LV dysfunction (15 > E/E' > 8), additional non-invasive investigations are required for diagnostic evidence of diastolic LV dysfunction. These can consist of blood flow Doppler of mitral valve or pulmonary veins, echo measures of LV mass index or left atrial volume index, electrocardiographic evidence of atrial fibrillation, or plasma levels of natriuretic peptides. If plasma levels of natriuretic peptides are elevated, diagnostic evidence of diastolic LV dysfunction also requires additional non-invasive investigations such as TD, blood flow Doppler of mitral valve or pulmonary veins, echo measures of LV mass index or left atrial volume index, or electrocardiographic evidence of atrial fibrillation. A similar strategy with focus on a high negative predictive value of successive investigations is proposed for the exclusion of HFNEF in patients with breathlessness and no signs of congestion. The updated strategies for the diagnosis and exclusion of HFNEF are useful not only for individual patient management but also for patient recruitment in future clinical trials exploring therapies for HFNEF.  相似文献   
995.

Objective

To estimate the dynamic causal effects of depressive symptoms on osteoarthritis (OA) knee pain.

Methods

Marginal structural models were used to examine dynamic associations between depressive symptoms and pain over 48 months among older adults (n = 2,287) with radiographic knee OA (Kellgren/Lawrence grade 2 or 3) in the Osteoarthritis Initiative. Depressive symptoms at each annual visit were assessed (threshold ≥16) using the Center for Epidemiologic Studies Depression Scale. OA knee pain was measured using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain subscale, rescaled to range from 0 to 100.

Results

Depressive symptoms at each visit were generally not associated with greater OA knee pain at subsequent time points. Causal mean differences in WOMAC pain score comparing depressed to nondepressed patients ranged from 1.78 (95% confidence interval [95% CI] ?0.73, 4.30) to 2.58 (95% CI 0.23, 4.93) within the first and fourth years, and the depressive symptoms by time interaction were not statistically significant (P = 0.94). However, there was a statistically significant dose‐response relationship between the persistence of depressive symptoms and OA knee pain severity (P = 0.002). Causal mean differences in WOMAC pain score comparing depressed to nondepressed patients were 0.89 (95% CI ?0.17, 1.96) for 1 visit with depressive symptoms, 2.35 (95% CI 0.64, 4.06) for 2 visits with depressive symptoms, and 3.57 (95% CI 0.43, 6.71) for 3 visits with depressive symptoms.

Conclusion

The causal effect of depressive symptoms on OA knee pain does not change over time, but pain severity significantly increases with the persistence of depressed mood.
  相似文献   
996.
997.
998.
999.
1000.
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