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   2808篇
  免费   182篇
  国内免费   4篇
耳鼻咽喉   30篇
儿科学   109篇
妇产科学   97篇
基础医学   435篇
口腔科学   88篇
临床医学   267篇
内科学   478篇
皮肤病学   77篇
神经病学   303篇
特种医学   169篇
外科学   348篇
综合类   40篇
一般理论   3篇
预防医学   203篇
眼科学   35篇
药学   179篇
中国医学   4篇
肿瘤学   129篇
  2022年   20篇
  2021年   49篇
  2020年   27篇
  2019年   59篇
  2018年   57篇
  2017年   41篇
  2016年   45篇
  2015年   64篇
  2014年   62篇
  2013年   105篇
  2012年   153篇
  2011年   163篇
  2010年   90篇
  2009年   72篇
  2008年   166篇
  2007年   163篇
  2006年   135篇
  2005年   109篇
  2004年   111篇
  2003年   93篇
  2002年   91篇
  2001年   68篇
  2000年   70篇
  1999年   70篇
  1998年   42篇
  1997年   26篇
  1996年   28篇
  1995年   37篇
  1994年   27篇
  1993年   31篇
  1992年   49篇
  1991年   43篇
  1990年   40篇
  1989年   49篇
  1988年   47篇
  1987年   32篇
  1986年   29篇
  1985年   36篇
  1984年   33篇
  1983年   26篇
  1980年   20篇
  1979年   21篇
  1978年   16篇
  1977年   19篇
  1976年   24篇
  1974年   23篇
  1973年   19篇
  1972年   20篇
  1971年   17篇
  1970年   19篇
排序方式: 共有2994条查询结果,搜索用时 672 毫秒
71.
72.
73.
Limited data are available on the longitudinal occurrence of syndemic factors among women at risk for HIV infection in the USA and how these factors relate to sexual risk over time. HVTN 906 was a longitudinal study enrolling 799 HIV-uninfected women in three cities. Assessments were done at baseline, 6, 12, and 18 months to assess syndemic factors (low education, low income, unemployment, lack of health insurance, housing instability, substance use, heavy alcohol use, partner violence, incarceration) and sexual risk outcomes. For each sexual risk outcome, a GEE model was fit with syndemic factors or syndemic score (defined as sum of binary syndemics, ranging from 0 to 9), visit, study site, age and race/ethnicity as predictors to examine the multivariable association between syndemic factors and outcomes over time. Odds of unprotected sex while drunk or high were significantly higher when women reported lack of health insurance, substance and heavy alcohol use and partner violence. Housing instability, substance and heavy alcohol use, partner violence and recent incarceration were associated with higher odds of having multiple sexual partners. Odds of sex exchange were significantly higher in the presence of unemployment, housing instability, low education, lack of health insurance, substance and heavy alcohol use, partner violence and incarceration. Housing instability, substance and heavy alcohol use, and partner violence were significantly associated with higher odds of unprotected anal sex. Odds of having a recent STI were significantly higher when women reported housing instability and partner violence. There were significantly higher odds of the reporting of any risk outcomes during follow-up with higher syndemic score. This study highlights a group of women experiencing multiple poor social and health outcomes who need to be the focus of comprehensive interventions.  相似文献   
74.
Journal of Thrombosis and Thrombolysis - Despite evolving evidence, the use of direct oral anticoagulants (DOACs) in patients with extremes of body weight remains controversial. This study aimed to...  相似文献   
75.

A growing number of investigations are exploring the utility of intranasal insulin as a means of mitigating cognitive decline. However, as a basic tenant of dementia prevention programs is increasing physical activity, it is essential to obtain a preliminary assessment of the safety profile of combining intranasal insulin with physical activity; to ensure that undue risks are not incurred. Utilizing a randomized double-blind placebo-controlled design, a sample of 116 non-diabetic, fasted college-aged adults were randomly assigned to receive a dose of 0-to-120 IU of NovoLog (Insulin Aspart) before being randomized to 20 min of exercise or sitting control condition. The safety of intranasal insulin was assessed by examining the incidence of potential symptoms of hypoglycemia and changes in peripheral blood glucose. The efficacy of a combination therapeutic approach was assessed using behavioral measures of inhibition and sustained attention alongside neuroelectric indices of attentional engagement. The frequency of symptoms reported following administration of intranasal insulin were not observed to interact with exercise so as to make their occurrence any more or less prominent, nor was the frequency observed to relate to the dose of intranasal insulin. However, doses of intranasal insulin of 100 IU or more were observed to result in a 7-fold increase in the likelihood of a level 1 hypoglycemic event for those individuals in the exercise condition. This study provides preliminary evidence to suggest that exercise is not associated with an increase in risk when combined with lower doses of intranasal insulin.

Clinical trial registration The trial is registered at ClinicalTrials.gov, number NCT04292535.

  相似文献   
76.
Patients with the postural orthostatic tachycardia syndrome (POTS) have symptoms of orthostatic intolerance despite having a normal orthostatic blood pressure (BP), which suggests some impairment of cerebrovascular regulation. Cerebrovascular autoregulation refers to the maintenance of normal cerebral blood flow in spite of changing BP. Mechanisms of autoregulation include myogenic, metabolic and neurogenic vasoregulation. Beat-to-beat recording of blood-flow velocity (BFV) is possible using transcranial Doppler imaging. It is possible to evaluate autoregulation by regressing deltaBFV to deltaBP during head-up tilt. A number of dynamic methods, relating deltaBFV to deltaBP during sudden induced changes in BP by occluding then releasing peripheral arterial flow or by the Valsalva maneuver. The deltaBFV to deltaBP provides an index of autoregulation. In orthostatic hypotension, the autoregulated range is typically expanded. In contrast, paradoxical vasoconstriction occurs in POTS because of an increased depth of respiration, resulting in hypocapnic cerebrovascular constriction, and impaired autoregulation.  相似文献   
77.
78.
79.
Although to date, the major impetus for the development of computer-assisted diagnosis (CAD) has been the detection of pulmonary nodules, CAD should properly be viewed as a potential tool for assisting radiologic interpretation of the entire gamut of chest diseases, including not just enhanced detection of disease but also characterization and quantification, ideally leading to improved patient management. The use of CAD to improve visualization of the airways using advanced computer techniques, including sophisticated methods for obtaining 3-dimensional segmentation of the central airways and, in particular, the development of virtual bronchoscopy has been recently studied. In this paper, the authors review the development of a specific series of CAD applications enabling automated identification and characterization of chronically inflamed airways. The advantages to the use of computer methodologies to quantify peripheral airway disease include reproducible visualization methods to display the location, severity, and extent of airway dilatation, bronchial wall thickening, and the presence of mucoid impacted airways. Currently, a number of semiquantitative global scoring systems have been proposed to assess disease extent and severity in patients with bronchiectasis. Unfortunately, with the exception of patients with cystic fibrosis, these are rarely if ever employed, largely owing to the considerable inconvenience of measuring individual airway dimensions and computing a global score. It is apparent that for this specific purpose, CAD may be ideally suited. Automated staging allows for more complete assessment of the entire bronchial tree while providing improved standardization and eliminating an otherwise tedious and time-consuming task.  相似文献   
80.
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