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   2688441篇
  免费   204081篇
  国内免费   8507篇
耳鼻咽喉   34831篇
儿科学   88149篇
妇产科学   72938篇
基础医学   375124篇
口腔科学   76177篇
临床医学   243118篇
内科学   534707篇
皮肤病学   62517篇
神经病学   214090篇
特种医学   104925篇
外国民族医学   504篇
外科学   412604篇
综合类   63740篇
现状与发展   6篇
一般理论   903篇
预防医学   207711篇
眼科学   61451篇
药学   193356篇
  11篇
中国医学   5920篇
肿瘤学   148247篇
  2018年   29295篇
  2017年   22481篇
  2016年   25591篇
  2015年   29007篇
  2014年   40429篇
  2013年   60054篇
  2012年   78837篇
  2011年   83882篇
  2010年   50879篇
  2009年   48304篇
  2008年   77935篇
  2007年   83045篇
  2006年   84317篇
  2005年   81010篇
  2004年   77894篇
  2003年   74773篇
  2002年   71639篇
  2001年   134525篇
  2000年   138117篇
  1999年   114593篇
  1998年   32178篇
  1997年   28362篇
  1996年   29103篇
  1995年   28623篇
  1994年   26485篇
  1993年   24660篇
  1992年   90614篇
  1991年   87849篇
  1990年   84709篇
  1989年   81201篇
  1988年   74599篇
  1987年   73221篇
  1986年   68998篇
  1985年   65938篇
  1984年   49456篇
  1983年   41767篇
  1982年   24737篇
  1981年   22197篇
  1980年   20552篇
  1979年   43997篇
  1978年   31147篇
  1977年   26528篇
  1976年   24564篇
  1975年   25737篇
  1974年   30669篇
  1973年   29536篇
  1972年   27436篇
  1971年   25258篇
  1970年   23314篇
  1969年   21869篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
73.
74.
75.
76.
77.
78.
79.

Background

Obesity is a risk factor for acetabular component malposition when total hip arthroplasty is performed with manual techniques. The utility of imageless navigation in obese patients remains unknown. This study compared the accuracy and precision of imageless navigation for component orientation between obese and nonobese patients.

Methods

A total of 459 total hip arthroplasties performed for osteoarthritis using imageless navigation were reviewed from a single surgeon’s institutional review board–approved database. Einzel-Bild-Roentgen Analyse determined component orientation on 6-week postoperative anteroposterior radiographs. Mean orientation error (accuracy) and precision were compared between obese (body mass index ≥ 30 kg/m2) and nonobese patients. Regression analysis evaluated the influence of obesity on component position.

Results

The difference in mean inclination and anteversion between obese and nonobese groups was 1.1° (43.0° ± 3.5°; range, 35.8°-57.8° vs 41.9° ± 4.4°; range, 33.0°-57.1° and 24.9° ± 6.3°; range, 14.2°-44.3° vs 23.8° ± 6.6°; range, 7.0°-38.6°, respectively). Inclination precision was better for nonobese patients. No difference in inclination accuracy or anteversion accuracy or precision was detected between groups. And 83% of components were placed within the target range. There was no relationship between obesity (dichotomized) and component placement outside the target ranges for inclination, anteversion, or both. As a continuous variable, increased body mass index correlated with higher odds of inclination outside the target zone (odds ratio, 1.06; P = .001).

Conclusion

Using imageless navigation, inclination orientation was less precise for obese patients, but the observed difference is likely not clinically relevant. Accurate superficial registration of landmarks in obese patients is achievable, and the use of imageless navigation similarly improves acetabular component positioning in obese and nonobese patients.

Level of Evidence

Therapeutic Level IV.  相似文献   
80.

Background

The purpose of the study was to evaluate the association between fetal echocardiographic measurements and the need for intervention (primary coarctation repair, staged coarctation repair, or catheter intervention) in prenatally diagnosed coarctation of the aorta.

Methods

A single-centre retrospective cohort study (2005-2015) of 107 fetuses diagnosed with suspected coarctation of the aorta in the setting of an apex-forming left ventricle and antegrade flow across the mitral and aortic valves.

Results

Median gestational age at diagnosis was 32 weeks (interquartile range, 23-35 weeks). Fifty-six (52%) did not require any neonatal intervention, 51 patients (48%) underwent a biventricular repair. In univariable analysis, an increase in ascending aorta (AAo) peak Doppler flow velocity (odds ratio [OR], 1.40 [95% confidence interval [CI], 1.05-1.91] per 20 cm/s; P = 0.03) was associated with intervention. No intervention was associated with larger isthmus size (OR, 0.23; P < 0.001), transverse arch diameter (OR, 0.23; P < 0.001), and aortic (OR, 0.72; P = 0.02), mitral (OR, 0.58; P = 0.001), and AAo (OR, 0.53; P < 0.001) z-scores. In multivariable analysis, higher peak AAo Doppler (OR, 2.51 [95% CI, 1.54-4.58] per 20 cm/s; P = 0.001) and younger gestational age at diagnosis (OR, 0.81 [95% CI, 0.70-0.93] per week; P = 0.005) were associated with intervention, whereas a higher AAo z-score (OR, 0.65 [95% CI, 0.43-0.94] per z; P = 0.029) and transverse arch dimension (OR, 0.44 [95% CI, 0.18-0.97]; P = 0.05) decreased the risk of intervention.

Conclusions

In prenatally suspected coarctation, the variables associated with intervention comprised smaller AAo and transverse arch size, earlier gestational age at diagnosis, and the additional finding of a higher peak AAo Doppler.  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