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   417136篇
  免费   29575篇
  国内免费   5775篇
耳鼻咽喉   5628篇
儿科学   8656篇
妇产科学   10641篇
基础医学   56907篇
口腔科学   12465篇
临床医学   35111篇
内科学   83214篇
皮肤病学   8976篇
神经病学   28678篇
特种医学   15452篇
外国民族医学   97篇
外科学   64468篇
综合类   18459篇
现状与发展   19篇
一般理论   69篇
预防医学   20965篇
眼科学   10359篇
药学   35547篇
  50篇
中国医学   4896篇
肿瘤学   31829篇
  2021年   4158篇
  2020年   3162篇
  2019年   4056篇
  2018年   5885篇
  2017年   4874篇
  2016年   4764篇
  2015年   5913篇
  2014年   8038篇
  2013年   9794篇
  2012年   13240篇
  2011年   13556篇
  2010年   8680篇
  2009年   7963篇
  2008年   11781篇
  2007年   12645篇
  2006年   12389篇
  2005年   11297篇
  2004年   10557篇
  2003年   10530篇
  2002年   9900篇
  2001年   29581篇
  2000年   29652篇
  1999年   24334篇
  1998年   5450篇
  1997年   4517篇
  1996年   3940篇
  1995年   3736篇
  1994年   3335篇
  1993年   2990篇
  1992年   16183篇
  1991年   14947篇
  1990年   14256篇
  1989年   14037篇
  1988年   12641篇
  1987年   12104篇
  1986年   11146篇
  1985年   10353篇
  1984年   6920篇
  1983年   5613篇
  1982年   2723篇
  1979年   5486篇
  1978年   3349篇
  1977年   2970篇
  1975年   2637篇
  1974年   3071篇
  1973年   2869篇
  1972年   2834篇
  1971年   2775篇
  1970年   2511篇
  1969年   2546篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
81.
82.

Background

In cardiothoracic surgery, little data exist on the transition to operative independence. We aimed to compare current perceptions of operative autonomy of junior cardiothoracic surgeons and senior colleagues who oversee transitional years.

Methods

An anonymous online survey was sent to currently practicing North American board-certified/eligible cardiothoracic surgeons to assess reported time to operative independence and comfort with cardiothoracic operations. The χ2 test, Fisher exact test, and Mann-Whitney U test were used to compare junior surgeons’ self-reported experience to the junior experience as reported by the midcareer and senior surgeons with whom they practiced. Logistic regression was performed to assess factors associated with operative independence.

Results

Responses from 436 completed surveys were analyzed (82 juniors and 354 midcareer/seniors). Two hundred fifty-four midcareer/senior surgeons reported on the experience of 531 junior partners. Juniors reported high immediate posttraining comfort with basic cardiac cases and moderate comfort with all other categories. Time to operative independence was significantly different between juniors' self-report and midcareer/senior reports of junior partners except for complex thoracic cases. In multivariable logistic regression analysis, senior, and not midcareer, surgeon status was independently associated with junior operative independence status for cardiac cases and for basic thoracic cases.

Conclusions

Most junior surgeons perceived operative independence with basic thoracic, basic cardiac, and complex cardiac operations earlier in their surgical career than that reported by senior colleagues. Objective measures of operative independence may clarify this discrepancy. This study establishes a baseline by which to compare the effects of integrated 6-year programs on operative independence. The discrepant perceptions may have implications for how training programs prepare graduates for the transition to independent practice.  相似文献   
83.

Introduction

Breast cancer incidence increases from the age of 30 years. As this age range coincides with that in which women usually pursue pregnancy, undergoing medical examinations for conditions such as breast cancer is a concern, especially when pregnancy is uncertain during the first eight weeks. Moreover, in this age range, breast often exhibits a high density, thus compromising diagnosis. For such density, digital breast tomosynthesis (DBT) provides a more accurate diagnosis than 2D mammography given its higher sensitivity and specificity. However, radiation exposure increases during DBT, and it should be determined.

Methods

We determined the entrance surface dose, scattered radiation dose, and average glandular dose (AGD), which can be mutually compared following an international protocol. Using our proposed method, the distribution of scattered radiation can be easily and quickly obtained with a minor load to the equipment. Then, we can determine the indoor scattered radiation and surface dose on patients during DBT.

Results

We obtained a maximum AGD of 2.32 mGy. The scattered radiation was distributed over both sides with maximum of approximately 40 μGy, whereas the maximum dose around the eye was approximately 10 μGy.

Conclusion

By measuring doses using the proposed method, a correct dose information can be provided for patients to mitigate their concerns about radiation exposure. Although the obtained doses were low, their proper management is still required. Overall, the results from this study can help to enhance dose management for patients and safety management regarding indoor radiation.  相似文献   
84.
85.
86.
Objective: This cross-sectional study assessed the effect of food donations on total nutrient intake of clients of a food pantry in Central Texas.

Methods: Nutrient intakes of total, base and food donation diets were estimated for 112 food pantry recipients using specific questionnaires; and then compared to the dietary reference intakes (DRI) and 2015–2020?US Dietary Guidelines.

Results: Food donations accounted for more than half of the client’s daily intake of energy, carbohydrates, vitamin B6, phosphorus, copper and selenium. Yet, daily total intake remained less than their DRIs for carbohydrates, poly-unsaturated fats, dietary fiber, fat soluble vitamins and vitamin C, and was even lower for calcium, magnesium and potassium. Total food intake of clients almost met the US Dietary Guidelines for refined grains, fruits, vegetables, and meat; however, the amount of whole grains and dairy was inadequate.

Conclusions: Supplemental foods offered at food pantries are an important resource for improving nutrient intake of low-income populations.  相似文献   

87.
88.
89.
90.
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