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   993篇
  免费   94篇
  国内免费   22篇
耳鼻咽喉   2篇
儿科学   68篇
妇产科学   8篇
基础医学   147篇
口腔科学   55篇
临床医学   85篇
内科学   218篇
皮肤病学   29篇
神经病学   40篇
特种医学   220篇
外科学   50篇
综合类   37篇
预防医学   42篇
眼科学   5篇
药学   39篇
肿瘤学   64篇
  2022年   7篇
  2018年   12篇
  2016年   13篇
  2015年   13篇
  2014年   18篇
  2013年   15篇
  2012年   15篇
  2011年   15篇
  2010年   27篇
  2009年   28篇
  2008年   25篇
  2007年   27篇
  2006年   25篇
  2005年   18篇
  2004年   15篇
  2003年   16篇
  2002年   19篇
  2001年   22篇
  2000年   24篇
  1999年   21篇
  1998年   41篇
  1997年   46篇
  1996年   44篇
  1995年   36篇
  1994年   27篇
  1993年   33篇
  1992年   22篇
  1991年   22篇
  1990年   15篇
  1989年   27篇
  1988年   32篇
  1987年   49篇
  1986年   31篇
  1985年   20篇
  1984年   12篇
  1983年   14篇
  1982年   14篇
  1981年   22篇
  1980年   18篇
  1979年   10篇
  1978年   8篇
  1977年   11篇
  1976年   23篇
  1975年   12篇
  1934年   8篇
  1932年   17篇
  1931年   16篇
  1930年   14篇
  1929年   7篇
  1926年   6篇
排序方式: 共有1109条查询结果,搜索用时 31 毫秒
31.
Background Isolating sufficient material for molecular testing remains challenging in non-small cell lung cancer (NSCLC). The use of new ultra-microsamples (uMS) is proven sufficient for DNA and mRNA detection, but whether uMS are useful for quantifying mRNA expression is unknown. We investigated if uMS from lung cancer patients can be used to generate quantitative data on mRNA expression. Methods uMS were collected from primary tumors and lymph nodes from patients suspected of having lung cancer. mRNA was isolated, reverse-transcribed into cDNA and quantified with quantitative PCR assays for hepatocyte growth factor receptor (MET), hepatocyte growth factor (HGF), epidermal growth factor receptor (EGFR) and amphiregulin (AREG) mRNA. The fraction of tumor cells to normal cells was estimated in each sample. Results MET, HGF, EGFR, and AREG expression were evaluated in 90 samples (30 containing cancer cells and 60 without cancer cells). MET and EGFR expression were negligible in samples without cancer cells. In samples containing cancer cells, MET and EGFR could be quantified in 13 samples each. Adjustment for tumor-cell fraction made it possible to obtain a quantitative result for the tumor-cell mRNA expression of MET and EGFR. In contrast, AREG and HGF were expressed in samples without tumor cells. These samples were used to establish the AREG and HGF mRNA expression in normal cells. Seven out of 14?AR-positive and two out of eight HGF-positive samples with tumor cells were above a cut-off of the mean?+?2SD established in samples without tumor cells. Conclusion We demonstrate that uMS contain high-quality mRNA, and quantitative studies can be performed when the tumor-cell fraction is considered.  相似文献   
32.
33.
34.
35.
36.
OBJECTIVES: The aim of this study was to assess the diagnostic accuracy of noninvasive markers of liver fibrosis in alcoholic liver disease. PATIENTS AND METHODS: Fifty-four clinical and biochemical parameters including serum fibrosis markers (hyaluronate and transforming growth factor beta1) were analyzed in 146 consecutive heavy drinkers (106 men, 40 women; mean age 49.2 years). Following liver biopsy, fibrosis was evaluated using a semi-quantitative scoring system (no fibrosis (0) to severe fibrosis (3 + )). Multivariate analysis was performed to determine the markers that were best correlated with the fibrosis score. RESULTS: Fifty-nine patients (40.4 %) had severe fibrosis (3 +) while 87 (59.6 %) had no fibrosis or moderate fibrosis (0 to 2 +). In multivariate analysis, serum hyaluronate and the prothrombin index were the best markers for the prediction of severe fibrosis. Hyaluronate and the prothrombin index had a diagnostic accuracy of 91.1 % and 89.7 %, respectively in the whole population. Finally, a significant negative correlation was found between hyaluronate and the prothrombin index (r =- 0.86, P <0.0001). CONCLUSIONS: Using only hyaluronate and the prothrombin index, 9 out of 10 alcoholic patients can be correctly classified according to the severity of liver fibrosis.  相似文献   
37.
Successful long-term phrenic nerve pacing has been reported in adults with acquired central hypoventilation syndrome. This report summarizes our experience with phrenic nerve pacing in 3 infants with congenital central hypoventilation syndrome. The electrodes were implanted in the lower thoracic portion of each phrenic nerve. In all patients. bilateral simultaneous pacing was required to maintain an adequate arterial PO2, tidal volume, and minute ventilation during quiet sleep. Case 1 died of problems primarily related to the severe cor pulmonale that had been present before pacemaker insertion; at autopsy, the pacemaker system was intact and there were no significant phrenic nerve abnormalities. Case 2 later developed failure of awake ventilatory control and died because of extensive phrenic nerve damage incurred by 19 days of continuous pacing. Case 3 has received quiet sleep pacemaker support since September 1977 and has been able to maintain normal quiet sleep ventilation in this manner. Phrenic nerve pacing can be successful in infants as long as continuous pacing is not required. Bilateral simultaneous pacing appears to be an appropriate alternative to home-based intermittent positive-pressure breathing for long-term management of children with central hypoventilation syndrome.  相似文献   
38.
BACKGROUND & AIMS: Shwachman syndrome is an inherited condition with multisystemic abnormalities, including exocrine pancreatic dysfunction. The aim of this study was to evaluate the occurrence and progression of features in a large cohort of patients. METHODS: Clinical records of 25 patients with Shwachman syndrome were reviewed. RESULTS: Mean birth weight (2.92 +/- 0.51 kg) was at the 25th percentile. However, by 6 months of age, mean heights and weights were less than the 5th percentile. After 6 months of age, growth velocity was normal. Severe fat maldigestion due to pancreatic insufficiency was present in early life (fecal fat, 26% +/- 17% of fat intake; age, < 2 years). Serial assessment of exocrine pancreatic function showed persistent deficits of enzyme secretion, but 45% of patients showed moderate age-related improvements leading to pancreatic sufficiency. Neutropenia was the most common hematologic abnormality (88%), but leukopenia, thrombocytopenia, and anemia were also frequently encountered. Patients with hypoplasia of all three bone marrow cellular lines (n = 11) had the worst prognosis; 5 patients died, 2 of sepsis and 3 of acute myelogenous leukemia. Other findings included hepatomegaly and/or abnormal liver function test results and skeletal abnormalities. CONCLUSIONS: A wide and varied spectrum of phenotypic abnormalities among patients with Shwachman syndrome is described. Pancreatic acinar dysfunction is an invariable abnormality. Patients with severe bone marrow involvement may have a guarded prognosis. (Gastroenterology 1996 Dec;111(6):1593-602)  相似文献   
39.
INTRODUCTION: Nonsustained ventricular tachycardia (NSVT) is a frequent phenomenon in some patients with heart disease, but its association with sustained ventricular tachycardias (ventricular tachycardia [VT]/ventricular fibrillation [VF]) is still not clear. The aim of this study was to determine whether NSVT incidence was associated with sustained VT/VF in patients with an implantable cardioverter defibrillator (ICD). METHODS AND RESULTS: Retrospective data analysis was conducted in 923 ICD patients with a mean follow-up of 4 months. NSVT and sustained VT/VF were defined as device-detected tachycardias. The incidence rates of NSVT and sustained VT/VF as well as ICD therapies were determined as episodes per patient. The NSVT index was defined as the product of NSVT episodes/day times the mean number of beats per episode, i.e., total beats/day. The NSVT index peak was defined as the highest value on or prior to the day with sustained VT/VF episodes. Patients (n = 393) with NSVT experienced a higher incidence of sustained VT/VF (17.2 +/- 63.0 episodes/patient) and ICD therapies (15.2 +/- 61.4 episodes/patient) than patients (n = 530) without NSVT (sustained VT/VF: 0.5 +/- 6.6 and therapies: 0.5 +/- 5.6; P < 0.0001). Approximately 74% of NSVT index peaks occurred on the same day or <3 days prior to sustained VT/VF episodes. The index was higher for peaks < or =3 days prior to the day with sustained VT/VF (94.3 +/- 140.1 total beats/day) than for peaks >3 days prior to the day with sustained VT/VF (32.7 +/- 55.9 total beats/day; P < 0.0001). CONCLUSION: ICD patients with NSVT represent a population more likely to experience sustained VT/VF episodes with a temporal association between an NSVT surge and sustained VT/VF occurrence.  相似文献   
40.
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