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   20687篇
  免费   1275篇
  国内免费   113篇
耳鼻咽喉   190篇
儿科学   673篇
妇产科学   451篇
基础医学   2896篇
口腔科学   1062篇
临床医学   1863篇
内科学   4272篇
皮肤病学   515篇
神经病学   1851篇
特种医学   420篇
外科学   2198篇
综合类   96篇
一般理论   19篇
预防医学   1975篇
眼科学   379篇
药学   1420篇
中国医学   95篇
肿瘤学   1700篇
  2024年   19篇
  2023年   214篇
  2022年   341篇
  2021年   801篇
  2020年   497篇
  2019年   664篇
  2018年   770篇
  2017年   576篇
  2016年   617篇
  2015年   710篇
  2014年   948篇
  2013年   1134篇
  2012年   1768篇
  2011年   1793篇
  2010年   1038篇
  2009年   808篇
  2008年   1383篇
  2007年   1338篇
  2006年   1230篇
  2005年   1120篇
  2004年   1021篇
  2003年   945篇
  2002年   781篇
  2001年   158篇
  2000年   148篇
  1999年   154篇
  1998年   130篇
  1997年   105篇
  1996年   94篇
  1995年   72篇
  1994年   60篇
  1993年   70篇
  1992年   73篇
  1991年   60篇
  1990年   35篇
  1989年   40篇
  1988年   34篇
  1987年   35篇
  1986年   30篇
  1985年   34篇
  1984年   32篇
  1983年   23篇
  1982年   26篇
  1981年   14篇
  1980年   16篇
  1979年   16篇
  1978年   12篇
  1977年   14篇
  1972年   9篇
  1969年   7篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
BackgroundLittle is known about the extent of ordering low-value services by.PurposeTo compare the rates of low-value back images ordered by primary care physicians (PCMDs) and primary care nurse practitioners (PCNPs).MethodWe used 2012 and 2013 Medicare Part B claims for all beneficiaries in 18 hospital referral ?regions (HRRs) and a measure of low-value back imaging from Choosing Wisely. Models included random clinician effect and fixed effects for beneficiary age, disability, Elixhauser comorbidities, clinician sex, the emergency department setting, back pain visit volume, organization, and region (HRR).FindingsPCNPs (N = 231) and PCMDs (N = 4,779) order low-value back images at similar rates (NP: all images: 26.5%; MRI/CT: 8.4%; MD: all images: 24.5%; MRI/CT: 7.7%), with no detectable significant difference when controlling for covariates.DiscussionPCNPs and PCMDs order low-value back images at an effectively similar rate.  相似文献   
3.
4.
5.
6.
7.
8.
9.

Background

In the emergency department, rib fractures are a common finding in patients who sustain chest trauma. Rib fractures may be a sign of significant, underlying pathology, especially in the elderly patients where rib fractures are associated with significant morbidity and mortality. To date, no studies have evaluated the ability of ultrasound to detect rib fractures using cadaver models and subsequently use this model as a teaching tool.

Objectives

The purpose of this study was to determine if it is possible to generate rib fractures on cadaver models which could be accurately identified using ultrasound.

Methods

This was a cross-sectional study performed during one session at a cadaver lab. A single hemithorax from four adult cadavers were used as models. Single rib fractures on each of rib five through eight were created. Four subjects, blinded to the normal versus fractured ribs, were asked to identify the presence of a fracture on each rib.

Results

A total of 8 of 16 potential ribs had fractured induced by study staff. Mean accuracy was 55% for all subjects. The overall sensitivity and specificity for detecting rib fractures was 50% (CI: 31.89–68.11) and 59.38% (CI: 35.69–73.55) respectively. The overall PPV and NPV was 55.17% and 54.29% respectively.

Conclusions

In this pilot study, subjects were not able to detect induced rib fractures using ultrasound on cadaver models. The use of this model as a teaching tool in the detection of rib fractures requires further investigation.  相似文献   
10.
Melatonin, the main hormone produced by the pineal gland, is secreted in a circadian manner (24‐hr period), and its oscillation influences several circadian biological rhythms, such as the regulation of clock genes expression (chronobiotic effect) and the modulation of several endocrine functions in peripheral tissues. Assuming that the circadian synchronization of clock genes can play a role in the regulation of energy metabolism and it is influenced by melatonin, our study was designed to assess possible alterations as a consequence of melatonin absence on the circadian expression of clock genes in the epididymal adipose tissue of male Wistar rats and the possible metabolic repercussions to this tissue. Our data show that pinealectomy indeed has impacts on molecular events: it abolishes the daily pattern of the expression of Clock, Per2, and Cry1 clock genes and Pparγ expression, significantly increases the amplitude of daily expression of Rev‐erbα, and affects the pattern of and impairs adipokine production, leading to a decrease in leptin levels. However, regarding some metabolic aspects of adipocyte functions, such as its ability to synthesize triacylglycerols from glucose along 24 hr, was not compromised by pinealectomy, although the daily profile of the lipogenic enzymes expression (ATP‐citrate lyase, malic enzyme, fatty acid synthase, and glucose‐6‐phosphate dehydrogenase) was abolished in pinealectomized animals.  相似文献   
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