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   19639篇
  免费   982篇
  国内免费   101篇
耳鼻咽喉   149篇
儿科学   242篇
妇产科学   226篇
基础医学   2336篇
口腔科学   460篇
临床医学   1188篇
内科学   4755篇
皮肤病学   1232篇
神经病学   1877篇
特种医学   810篇
外科学   3227篇
综合类   113篇
预防医学   477篇
眼科学   188篇
药学   1714篇
中国医学   62篇
肿瘤学   1666篇
  2023年   75篇
  2022年   133篇
  2021年   332篇
  2020年   196篇
  2019年   236篇
  2018年   341篇
  2017年   269篇
  2016年   363篇
  2015年   377篇
  2014年   465篇
  2013年   523篇
  2012年   893篇
  2011年   941篇
  2010年   529篇
  2009年   460篇
  2008年   878篇
  2007年   952篇
  2006年   893篇
  2005年   891篇
  2004年   929篇
  2003年   981篇
  2002年   901篇
  2001年   641篇
  2000年   682篇
  1999年   677篇
  1998年   302篇
  1997年   192篇
  1996年   207篇
  1995年   178篇
  1994年   180篇
  1993年   134篇
  1992年   477篇
  1991年   409篇
  1990年   421篇
  1989年   442篇
  1988年   415篇
  1987年   400篇
  1986年   327篇
  1985年   299篇
  1984年   180篇
  1983年   153篇
  1982年   99篇
  1981年   75篇
  1979年   170篇
  1978年   85篇
  1977年   94篇
  1974年   73篇
  1973年   82篇
  1972年   88篇
  1970年   78篇
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
1.
2.

Purpose

Suppression of respiratory movement of the liver would be desirable for high-precision radiation therapy for liver tumors. We aimed to investigate the effect of our original device-free compressed shell fixation method and breathing instruction on suppression of respiratory movement. The characteristics of liver motion based on the movement of a fiducial marker were also analyzed.

Methods and Materials

First, respiratory amplitudes of the liver with the device-free compressed shell were analyzed from the data of 146 patients. The effect of this shell fixing method on liver movement was evaluated. Second, as another cohort study with 166 patients, interfractional internal motion of the liver for patients fixed in the shell was calculated using the fiducial marker coordinate data of images for position setting before daily irradiation. Third, in another 12 patients, intrafractional internal motion was calculated from the fiducial marker coordinate data using x-ray images before and after irradiation.

Results

The median respiratory movement without the shell, after fixing with the shell, and after instructing on the breathing method with the shell was 14.2 (interquartile range, 10.7-19.8), 11.5 (8.6-17.5), and 10.4 mm (7.3-15.8), respectively. Systematic and random errors of interfractional internal motion were all ≤2 mm in the left-right and anteroposterior directions and 3.7 and 3.0 mm, respectively, in the craniocaudal direction. Systematic and random errors of intrafractional internal motion were all ≤1.3 mm in the left-right and anteroposterior directions and 0.8 and 2.4 mm, respectively, in the craniocaudal direction.

Conclusions

The device-free compressed shell fixation method was effective in suppressing the respiratory movement of the liver. Irradiation position matching using the fiducial marker can correct the interfractional internal motion on each day, which would contribute to the reduction of the margin to be given around the target.  相似文献   
3.
4.
5.
6.
7.
neurogenetics - Mediator (MED) is a key regulator of protein-coding gene expression, and mutations in MED subunits are associated with a broad spectrum of diseases. Because mutations in MED17...  相似文献   
8.
9.
Purpose:It has been reported previously that intravenously administered gadolinium-based contrast agent (GBCA) leaks into the subarachnoid space around the cortical veins at 4 h after injection in all old people over 37 years, but not in younger people up to 37 years of age in 3D-real IR images. The purpose of this study was to investigate whether there was a strict threshold of 37 years of age for the leakage of the GBCA into the subarachnoid space.Methods:The subjects included 190 patients, that were scanned for 3D-real IR images at 4 hours after intravenous injection of GBCA as a diagnostic test for endolymphatic hydrops. The patient’s age ranged from 14 to 81 years. Two experienced neuroradiologists evaluated the images to determine whether the GBCA leakage around the cortical veins was positive or negative. Any discrepancies between the two observers were discussed and a consensus was obtained.A Mann–Whitney U test and receiver operating characteristic (ROC) curve analysis were used to compare the positive and the negative group and to set the age cut-off value for the prediction of GBCA leakage.Results:The GBCA leakage around the cortical veins was negative in 35 patients and positive in 155 patients. The average age was 33 ± 11 years in the negative group, and 55 ± 12 years in the positive group (P < 0.01). In the ROC analysis for the age and leakage of the GBCA, an area under the curve was 0.905 and the cut-off age was 37.317 years (sensitivity of 0.942 and specificity of 0.771).Conclusion:Intravenously administered GBCA leaks into the subarachnoid space around the cortical veins in most patients over 37 years of age. However, it should be noted that it can be found occasionally in patients under 37 years of age.  相似文献   
10.
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