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   4596篇
  免费   443篇
  国内免费   13篇
耳鼻咽喉   11篇
儿科学   139篇
妇产科学   85篇
基础医学   674篇
口腔科学   106篇
临床医学   402篇
内科学   729篇
皮肤病学   44篇
神经病学   367篇
特种医学   225篇
外科学   813篇
综合类   127篇
一般理论   31篇
预防医学   361篇
眼科学   63篇
药学   531篇
中国医学   10篇
肿瘤学   334篇
  2022年   33篇
  2021年   74篇
  2020年   40篇
  2019年   68篇
  2018年   73篇
  2017年   46篇
  2016年   60篇
  2015年   74篇
  2014年   99篇
  2013年   155篇
  2012年   214篇
  2011年   209篇
  2010年   125篇
  2009年   114篇
  2008年   175篇
  2007年   180篇
  2006年   231篇
  2005年   204篇
  2004年   208篇
  2003年   177篇
  2002年   179篇
  2001年   183篇
  2000年   192篇
  1999年   169篇
  1998年   74篇
  1997年   75篇
  1996年   48篇
  1995年   55篇
  1994年   56篇
  1993年   57篇
  1992年   122篇
  1991年   112篇
  1990年   98篇
  1989年   82篇
  1988年   94篇
  1987年   70篇
  1986年   66篇
  1985年   62篇
  1984年   45篇
  1983年   41篇
  1982年   34篇
  1980年   31篇
  1979年   56篇
  1978年   41篇
  1977年   44篇
  1976年   38篇
  1975年   36篇
  1974年   32篇
  1973年   43篇
  1972年   27篇
排序方式: 共有5052条查询结果,搜索用时 15 毫秒
991.
992.
993.
The effectiveness of influenza vaccine in reducing hospital admissions for pneumonia, influenza, bronchitis, or emphysema was assessed by a case-control study of people aged 16 years and older who were admitted to 10 Leicestershire hospitals between 1 December 1989 and 31 January 1990. Hospital and general practitioners'' records for 156 admissions (the cases) and 289 controls matched for age and sex were reviewed. Information was collected on demography, the usual place of residence (institutional or non-institutional), the existence of chronic illness, and vaccination during the 5 years before admission. The odds ratio for hospital admission among vaccinees was 0.67 (95% CI 0.39-1.12) giving an estimate of vaccine effectiveness in this setting of 33% (95% CI 0-61). However, multivariate logistic regression, adjusting for the effects of institutional care and chronic illness, revealed that influenza vaccination reduced hospital admissions by 63% (95% CI 17-84%). There was a strong trend towards improved vaccine effectiveness when used in institutional settings. Influenza vaccine is effective in reducing hospital admissions for influenza, pneumonia, bronchitis and emphysema, and effectiveness is comparable to that observed for influenza and pneumonia admissions in North America.  相似文献   
994.
995.
996.
997.
998.
The ligament of the head of femur (LHF) or ligamentum teres has been reported to tense during hip adduction and also to provide mechanical stability to the joint. LHF injury is more common in females and also in right hip joints compared with left ones. Although this could be due to leg dominance, pelvic size or muscle strength, there is no study that has looked into these differences. This cadaveric biomechanical study aimed to compare potential differences in the mechanical behavior of the LHF between neutral and 20° adducted hip joints, sex, and sides. Tensile tests of the LHF were performed on 25 hip joints (mean age at death of 85.7 ± 7.5 years; 9 females, 4 males; 13 left, 12 right), positioned either neutrally or in adduction. The maximum force required to rupture the ligament, its strain at failure, tensile strength, linear stiffness, and elastic modulus were obtained and statistically compared between analysis groups. The maximum force the LHF could withstand before rupture averaged 57 ± 37 N, strain at failure of 59 ± 33%, tensile strength of 2.9 ± 1.8 MPa, linear stiffness of 5.4 ± 3.5 N/mm, and elastic modulus of 7.2 ± 3.8 MPa. The LHF length at failure was significantly greater in males compared with females (P = 0.02). Irrespective of joint position, there were no statistical differences in the stress–strain properties of the LHF between females and males, or sides. There may be other anatomical, functional, and demographic factors that could render the ligament tissue vulnerable to injury in these groups. Clin. Anat., 33:705–713, 2020. © 2019 Wiley Periodicals, Inc.  相似文献   
999.
Thousands of kidneys from higher-risk donors are discarded annually because of the increased likelihood of complications posttransplant. Given the severe organ shortage, there is a critical need to improve utilization of these organs. To this end, normothermic machine perfusion (NMP) has emerged as a platform for ex vivo assessment and potential repair of marginal organs. In a recent study of 8 transplant-declined human kidneys on NMP, we discovered microvascular obstructions that impaired microvascular blood flow. However, the nature and physiologic impact of these lesions were unknown. Here, in a study of 39 human kidneys, we have identified that prolonged cold storage of human kidneys induces accumulation of fibrinogen within tubular epithelium. Restoration of normoxic conditions—either ex vivo during NMP or in vivo following transplant—triggered intravascular release of fibrinogen correlating with red blood cell aggregation and microvascular plugging. Combined delivery of plasminogen and tissue plasminogen activator during NMP lysed the plugs leading to a significant reduction in markers of renal injury, improvement in indicators of renal function, and improved delivery of vascular-targeted nanoparticles. Our study suggests a new mechanism of cold storage injury in marginal organs and provides a simple treatment with immediate translational potential.  相似文献   
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