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   187280篇
  免费   8017篇
  国内免费   353篇
耳鼻咽喉   3206篇
儿科学   7022篇
妇产科学   4867篇
基础医学   26349篇
口腔科学   4985篇
临床医学   15232篇
内科学   33915篇
皮肤病学   4852篇
神经病学   17631篇
特种医学   9130篇
外国民族医学   24篇
外科学   29504篇
综合类   1321篇
一般理论   74篇
预防医学   10520篇
眼科学   4914篇
药学   12705篇
中国医学   352篇
肿瘤学   9047篇
  2023年   872篇
  2021年   1574篇
  2020年   1314篇
  2019年   1617篇
  2018年   3236篇
  2017年   2642篇
  2016年   3591篇
  2015年   4039篇
  2014年   4355篇
  2013年   6211篇
  2012年   9476篇
  2011年   8964篇
  2010年   5255篇
  2009年   4231篇
  2008年   8744篇
  2007年   9660篇
  2006年   9719篇
  2005年   10063篇
  2004年   9539篇
  2003年   9395篇
  2002年   9291篇
  2001年   6342篇
  2000年   6391篇
  1999年   5572篇
  1998年   1787篇
  1997年   1464篇
  1996年   1127篇
  1995年   920篇
  1994年   879篇
  1993年   819篇
  1992年   2483篇
  1991年   2396篇
  1990年   2363篇
  1989年   2218篇
  1988年   1935篇
  1987年   1913篇
  1986年   1799篇
  1985年   1726篇
  1984年   1364篇
  1983年   1094篇
  1979年   1428篇
  1978年   1078篇
  1977年   915篇
  1975年   1146篇
  1974年   1164篇
  1973年   1070篇
  1972年   1063篇
  1971年   1024篇
  1970年   904篇
  1969年   855篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.

Background Context

The concept of dynamic stabilization (DS) of the lumbar spine for treatment of degenerative instability has been introduced almost two decades ago. Dynamic stabilization follows the principle of controlling movement in the coronal plane by providing load transfer of the spinal segment without fusion and, at the same time, reducing side effects such as adjacent segment disease (ASD). So far, only little is known about revision rates after DS due to ASD and screw loosening (SL).

Purpose

The present study aimed to evaluate the longitudinal revision rates following dynamic pedicle screw stabilization in the lumbar spine and to determine specific risk factors predictive for ASD, SL, and overall reoperation in a large cohort with considerable follow-up.

Design

We carried out a post hoc analysis of a prospectively collected database in a level I spine center.

Patients Example

The patient sample comprised 283 (151 female/132 male) consecutive patients suffering from painful degenerative lumbar segmental instability with or without spinal stenosis who underwent DS of the lumbar spine (Ulrich Cosmic, Ulrich Medical, Ulm, Germany) between January 2008 and December 2011.

Outcome Measures

Longitudinal reoperation rate and risk factors predictive for revision surgery were evaluated.

Methods

We analyzed the longitudinal reoperation rate due to ASD and SL and overall reoperation. Risk factors such as age, gender, body mass index, lumbar lordosis (LL), number of segments, and number of previous surgeries were taken into account. Regular and mixed model logistic regressions were performed to determine risk factors for revision surgery on a patient and on a screw level.

Results

The mean age was 65.7±10.2 years (range 31–88). One hundred thirty-two patients were stabilized in 1 segment, 134 in 2 segments, 15 in 3 segments, and 2 patients in 4 segments. Reoperation rate for ASD and SL after 1 year was 7.4 %, after 2 years was 15.0%, and after a mean follow-up of 51.4±15 months was 22.6%. Reasons for revision were SL in 19 cases (6.6%), ASD in 39 cases (13.7%), SL and ASD in 6 cases, hematoma in 2 cases (0.7%), cerebrospinal fluid fistulae in 3 cases (1.1%), infection in 6 cases (2.1%), and implant failure in 1 case (0.4%). The patients' age, the number of stabilized segments, and the number of previous surgeries and postoperative LL had a significant influence on the probability for revision surgery.

Conclusions

Reoperation rates after DS of the lumbar spine are comparable with rigid fixations. The younger the patient and the more segments are involved, the lower the LL and the more previous surgeries were found, the higher was the risk of revision. Risk of revision was almost twice as high in men compared with women. We therefore conclude that for clear clinical indication and careful evaluation of preoperative imaging data, DS using the Cosmic system seems to be a possible option. The presented data will help to further tailor indication and patient selection.  相似文献   
42.
43.
44.
45.
Background Although prostate cancer is a leading cause of cancer death, its aetiology is not well understood. We aimed to identify novel biochemical factors for prostate cancer incidence and mortality in UK Biobank.Methods A range of cardiovascular, bone, joint, diabetes, renal and liver-related biomarkers were measured in baseline blood samples collected from up to 211,754 men at recruitment and in a subsample 5 years later. Participants were followed-up via linkage to health administrative datasets to identify prostate cancer cases. Hazard ratios (HRs) and 95% confidence intervals were calculated using multivariable-adjusted Cox regression corrected for regression dilution bias. Multiple testing was accounted for by using a false discovery rate controlling procedure.Results After an average follow-up of 6.9 years, 5763 prostate cancer cases and 331 prostate cancer deaths were ascertained. Prostate cancer incidence was positively associated with circulating vitamin D, urea and phosphate concentrations and inversely associated with glucose, total protein and aspartate aminotransferase. Phosphate and cystatin-C were the only biomarkers positively and inversely, respectively, associated with risk in analyses excluding the first 4 years of follow-up. There was little evidence of associations with prostate cancer death.Conclusion We found novel associations of several biomarkers with prostate cancer incidence. Future research will examine associations by tumour characteristics.Subject terms: Predictive markers, Prostate cancer, Risk factors  相似文献   
46.
47.
48.
49.
50.
ABSTRACT

Purpose

To investigate the effect of 1% tropicamide on anterior chamber aqueous flare (ACAF) measurements acquired with laser flare meter in patients with pseudoexfoliation.  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