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   1016篇
  免费   67篇
  国内免费   12篇
耳鼻咽喉   17篇
儿科学   46篇
妇产科学   16篇
基础医学   86篇
口腔科学   106篇
临床医学   86篇
内科学   213篇
皮肤病学   19篇
神经病学   46篇
特种医学   32篇
外科学   191篇
综合类   13篇
一般理论   2篇
预防医学   98篇
眼科学   18篇
药学   54篇
中国医学   1篇
肿瘤学   51篇
  2023年   5篇
  2022年   23篇
  2021年   46篇
  2020年   21篇
  2019年   38篇
  2018年   51篇
  2017年   24篇
  2016年   20篇
  2015年   14篇
  2014年   30篇
  2013年   40篇
  2012年   56篇
  2011年   55篇
  2010年   38篇
  2009年   31篇
  2008年   42篇
  2007年   50篇
  2006年   37篇
  2005年   33篇
  2004年   36篇
  2003年   58篇
  2002年   45篇
  2001年   32篇
  2000年   41篇
  1999年   20篇
  1998年   12篇
  1997年   5篇
  1995年   9篇
  1992年   7篇
  1991年   11篇
  1990年   12篇
  1989年   10篇
  1988年   9篇
  1987年   7篇
  1986年   7篇
  1985年   10篇
  1984年   16篇
  1983年   9篇
  1982年   5篇
  1980年   5篇
  1979年   5篇
  1978年   5篇
  1977年   5篇
  1976年   5篇
  1975年   5篇
  1974年   8篇
  1973年   7篇
  1972年   4篇
  1970年   6篇
  1968年   6篇
排序方式: 共有1095条查询结果,搜索用时 15 毫秒
11.
12.
Electron microscopic examination of an infantile hemangioendothelioma (IHE) type I of the liver, appearing in a five month old child, showed a high density of pericytes in the walls of the neoplastic vessels. These vessels, in part of the IHE patients, establish an important arteriovenous shunt leading to high output, congestive cardiac failure. It is unclear whether functions ascribed to pericytes, such as participation in microvascular contractility or as suppressors of endothelial cell proliferation are involved in two noteworthy aspects of the present case. The child exhibited no congestive heart failure and the multiple nodular lesions underwent spontaneous regression.  相似文献   
13.
14.
Extracellular neuraminidase production by group A streptococci was examined in 92 strains. Fourteen of these strains produced appreciable amounts of enzyme; 12 of the neuraminidase-producing strains belonged to T types 1, 4, and 12. Production of the enzyme paralleled bacterial growth in culture and was maximal in medium containing 0.2% glucose. The enzyme produced by one of these strains was partially purified by ammonium sulfate fractionation and filtration on G-200 Sephadex. Its molecular weight was estimated at 90,000. Activity was optimal at pH 5.7 and in the presence of 0.01 to 0.03 M calcium and magnesium cations. The enzyme was stable at temperatures of 4 and 37 degrees C for at least 24 h but was inactivated within 10 min at temperatures of 50 and 65 degrees C. The enzyme hydrolyzed 40% of the sialic acid in bovine submaxillary mucin, but was inactive on sialyl-lactose, porcine submaxillary mucin, oligosaccharides derived from porcine mucin, or human orosomucoid. The Km value for this enzyme with bovine submaxillary mucin as substrate was in the order of 3.6 x 10(-4) M.  相似文献   
15.
The Eastern Mediterranean Region (EMR) is experiencing a nutrition transition, characterized by the emergence of overnutrition and micro-nutrient deficiencies. No previous study has comparatively examined nutrient intake in adults across countries in the EMR. This review examined the adequacy of nutrients in adults living in the EMR. Moreover, it analyzed the food balance sheets (FBS) for 1961–2018 to identify the trajectory of energy supply from macro-nutrients in the EMR. A systematic search was conducted from January 2012 to September 2020. Only observational studies were retained with a random sampling design. An assessment of the methodological quality was conducted. Levels of nutrient daily intake and their adequacy compared to the daily reference intake of the Institute of Medicine were reported across the region. No studies were identified for half of the region’s countries. Although nutrient energy intake was satisfactory overall, fat and carbohydrate intake were high. Intake of vitamin D, calcium, potassium, zinc, and magnesium were below that recommended. The analysis of the FBS data allowed for the identification of four linear patterns of trajectories, with countries in the EMR best fitting the ‘high-energy-supply from carbohydrate’ group. This systematic review warrants multi-sectorial commitment to optimize nutrient intake.  相似文献   
16.
This study presents the relationships between ambient air pollutants and morbidity and emergency department visits among children and adults performed in Great Casablanca, the most populated and economic region in Morocco. This research was analyzed using conditional Poisson model for the period 2011–2013. In the period of study, the daily average concentrations of SO2, NO2, O3 and PM10 in Casablanca were 209.4 µg/m3, 61 µg/m3, 113.2 µg/m3 and 75.1 µg/m3, respectively. In children less than 5 years old, risk of asthma could be increased until 12% per 10 µg/m3 increase in NO2, PM10, SO2 and O3. In children over 5 years and adults, an increase of 10 µg/m3 air pollutant can cause an increase until 3% and 4% in respiratory consultations and acute respiratory infection, respectively. Similarly, impact on emergency department visits due to respiratory and cardiac illness was established. Our results suggest a not negligible impact on morbidity of outdoor air pollution by NO2, SO2, O3, and PM10.  相似文献   
17.
Substernal goiter is an infrequent occurrence and is found in two to five per cent of all patients undergoing thyroid surgery. These lesions are well known to cause respiratory symptoms and alterations in phonation due to direct compression of airway structures. Infrequently, unilateral recurrent nerve palsy has been reported in patients with substernal goiter. We report a case of bilateral recurrent nerve palsy associated with multinodular substernal goiter in an 89-year-old female who presented in respiratory distress.  相似文献   
18.
Extensible endoprostheses of the humerus after resection of bone tumours   总被引:2,自引:0,他引:2  
We carried out extensible endoprosthetic replacement of the proximal or total humerus in 18 children aged between six and 12 years, after resection of primary bone tumours mainly for osteosarcoma and Ewing's sarcoma. In 11 patients we performed 44 lengthening procedures, with an average of two per child annually and a mean total extension of 29.9 mm per patient. We were able to achieve lengthening of the operated limb with few complications and a mean functional rating of 79.3% according to the Enneking system. Progressive lengthening of these prostheses does not adversely affect the overall function of the arm, and superior subluxation of the head of the prosthesis has not been a problem.  相似文献   
19.
The bacterial extract OM-89 used for the prevention and treatment of recurrent urinary tract infections constitutes an effective immunostimulant in vitro and in vivo. Here we demonstrate that OM-89 shows mitogenic properties towards murine spleen cell cultures from LPS responder and non-responder mice. In macrophages the extract induces the translocation of NF-kappaB into the cell nucleus and RNI (radical nitrogen intermediates) release, which could be attributed to single fractions of the extract. Our findings on the in vitro immunostimulatory effect of OM-89, as well as its immunogenic and adjuvant properties, are of importance for understanding its therapeutic efficacy as demonstrated in clinical studies.  相似文献   
20.
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