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   3407篇
  免费   678篇
  国内免费   27篇
耳鼻咽喉   80篇
儿科学   124篇
妇产科学   62篇
基础医学   456篇
口腔科学   94篇
临床医学   422篇
内科学   877篇
皮肤病学   53篇
神经病学   221篇
特种医学   76篇
外科学   511篇
综合类   88篇
一般理论   1篇
预防医学   234篇
眼科学   106篇
药学   270篇
中国医学   33篇
肿瘤学   404篇
  2023年   27篇
  2022年   47篇
  2021年   102篇
  2020年   111篇
  2019年   240篇
  2018年   195篇
  2017年   178篇
  2016年   188篇
  2015年   226篇
  2014年   255篇
  2013年   276篇
  2012年   224篇
  2011年   219篇
  2010年   232篇
  2009年   157篇
  2008年   173篇
  2007年   147篇
  2006年   128篇
  2005年   127篇
  2004年   114篇
  2003年   114篇
  2002年   110篇
  2001年   47篇
  2000年   44篇
  1999年   33篇
  1998年   26篇
  1997年   20篇
  1996年   20篇
  1995年   19篇
  1994年   17篇
  1993年   12篇
  1992年   31篇
  1991年   32篇
  1990年   23篇
  1989年   22篇
  1988年   23篇
  1987年   21篇
  1986年   8篇
  1985年   8篇
  1984年   11篇
  1983年   7篇
  1980年   7篇
  1979年   8篇
  1977年   7篇
  1976年   6篇
  1975年   6篇
  1974年   8篇
  1972年   9篇
  1971年   7篇
  1970年   6篇
排序方式: 共有4112条查询结果,搜索用时 15 毫秒
61.
62.
63.
64.
65.
66.
Background: The initial thickness of maxillary bone has significant impact on the responding level of facial bone and soft tissue after extraction and immediate implant placement. A prevailing notion is that following implant placement in fresh extraction sites, at least 2 mm of facial bone is needed to prevent soft tissue recession, fenestration, and dehiscence. Purpose: The purpose of this study was to use cone beam computed tomography (CBCT) to measure horizontal width of facial alveolar bone overlying healthy maxillary central incisors and to determine prevalence of bone thickness ≥2 mm. Materials and Methods: Tomographic data from 101 randomly selected patients were evaluated by two independent observers. Assessments were made of facial bone width at levels 1.0 to 10.0 mm apical to the bone crest. Results: Healthy maxillary central incisors (n = 202) were measured from 101 patient scans. The percent of teeth with facial bone ≥2 mm at levels 1, 2, 3, 4, and 5 mm from the bone crest was 0, 1.5, 2.0, 3.0, and 2.5%, respectively. Overall mean thickness of the bone was 1.05 mm for right and left central incisors combined. The range of individual measurements for all levels was 0 to 5.1 mm. The occurrence of ≥2 mm thickness bone measurements increased with increasing depth. However, mean widths observed at levels 6 to 10 mm from the crest ranged only 1.0 to 1.3 mm because of apparent fenestration occurrence (0 mm bone) in approximately 12% of teeth. Overall, no significant differences in bone thickness were found between ethnic, gender, age, or scan groups. Conclusions: Using CBCT, occurrences of ≥2 mm maxillary facial alveolar bone were found on no more than 3% of root surfaces 1.0 to 5.0 mm apical to the bone crest in this sample of maxillary central incisors. The study evidenced prevalence of a thin facial alveolar bone (<2 mm) that may contribute to risk of facial bone fenestration, dehiscence, and soft tissue recession after immediate implant therapy.  相似文献   
67.
Youth violence has long been regarded as a major social issue. The past decade has, however, seen the scrutiny which encompasses this violence intensify, largely due to a recent media focus on an apparently increasing tendency amongst some young people to engage in acts of ‘appetitive’ or ‘thrill-seeking’ violence. This is reported to be a new form of violence, in which young people act in an excitable state, rather than the more common form of anger-mediated violence. Whilst incidents of appetitive violence are overly represented in the news media and are presented as a major public concern, there is presently no empirical research exploring the validity of this phenomenon and no systematic analysis of the frequency and severity of this form of violent behaviour. Furthermore, the underlying causes of this type of violence are not understood. As such, preventative practices, risk assessment, treatment requirements and targeted management strategies are lacking. The purpose of this review is to examine the current literature on youth violence, particularly youth involvement in ‘thrill-seeking’ acts of violence, as well as describing a range of contemporary factors highlighted as integral to youth violence; specifically, gang involvement, alcohol use and the possession of weapons. This review will also examine an array of international strategies implemented in response to this form of youth violence. Finally, the General Aggression Model (GAM) will be considered to determine whether its framework can assist in advancing our understanding of appetitive violence, by elucidating those characteristics of the individual and their environment that contribute to its expression.  相似文献   
68.
69.
70.

Background

Little is known about the effects of diagnostic ureteroscopy on intravesical recurrence after nephroureterectomy.

Methods

This study was designed to determine the effect of diagnostic ureteroscopy on intravesical recurrence after nephroureterectomy. From 2004 to 2010, 446 patients underwent nephroureterectomy for upper urinary tract cancer at our tertiary medical center. We included 115 patients who underwent preoperative diagnostic ureteroscopy and 281 patients who did not. This study analyzed the impact of the reported risk factors and diagnostic ureteroscopy for intravesical recurrence after nephroureterectomy by multivariate Cox regression model.

Results

The rates of metastasis and cancer-specific mortality did not differ significantly between the two groups. Diagnostic ureteroscopy was associated with a higher incidence of intravesical recurrence in patients with (p = 0.02) and without (p = 0.016) a previous history of bladder cancer. Ureter tumor biopsy (p = 0.272) and ureter involvement (p = 0.743) were not associated with the rate of intravesical recurrence in this study. Multivariate Cox regression analysis showed that only bladder cancer history (p < 0.001), multifocal tumor (p = 0.05), and diagnostic ureteroscopy (p = 0.05) were independently associated with intravesical recurrence.

Conclusions

Diagnostic ureteroscopy for upper urinary tract cancer was not associated with metastasis and cancer-specific mortality. However, ureteroscopy was associated with an increased incidence of intravesical tumor recurrence. Methods of prevention should be considered to decrease intravesical recurrence and avoid repeated surgical interventions or the development of advanced bladder disease in patients at risk.  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