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   65529篇
  免费   3251篇
  国内免费   474篇
耳鼻咽喉   686篇
儿科学   1217篇
妇产科学   783篇
基础医学   8718篇
口腔科学   1449篇
临床医学   4151篇
内科学   16877篇
皮肤病学   1374篇
神经病学   4587篇
特种医学   2462篇
外科学   11224篇
综合类   285篇
一般理论   7篇
预防医学   1870篇
眼科学   1526篇
药学   4240篇
中国医学   236篇
肿瘤学   7562篇
  2023年   282篇
  2022年   656篇
  2021年   1234篇
  2020年   657篇
  2019年   915篇
  2018年   1277篇
  2017年   975篇
  2016年   1232篇
  2015年   1306篇
  2014年   1691篇
  2013年   2159篇
  2012年   3399篇
  2011年   3812篇
  2010年   2157篇
  2009年   1928篇
  2008年   3496篇
  2007年   3841篇
  2006年   3827篇
  2005年   3872篇
  2004年   3920篇
  2003年   4016篇
  2002年   3885篇
  2001年   1336篇
  2000年   1267篇
  1999年   1375篇
  1998年   1021篇
  1997年   856篇
  1996年   827篇
  1995年   681篇
  1994年   615篇
  1993年   634篇
  1992年   970篇
  1991年   887篇
  1990年   794篇
  1989年   857篇
  1988年   767篇
  1987年   671篇
  1986年   650篇
  1985年   612篇
  1984年   456篇
  1983年   351篇
  1982年   250篇
  1981年   242篇
  1980年   226篇
  1979年   296篇
  1978年   265篇
  1977年   208篇
  1976年   156篇
  1974年   145篇
  1969年   154篇
排序方式: 共有10000条查询结果,搜索用时 358 毫秒
1.
The aim of the present review was to clarify how we should detect and diagnose sessile serrated polyps (SSP) endoscopically. A systematic search was conducted of MEDLINE from January 2004 through March 2018. Nine findings: (i) proximal location; (ii) size >10 mm; (iii) irregular shape; (iv) indistinctive border; (v) cloud‐like surface; (vi) mucus cap; (vii) rim of debris in white‐light endoscopy; (viii) dilated vessels; and (ix) dilated crypts (pits) in image‐enhanced endoscopy were considered to be candidate discriminators of SSP from hyperplastic polyps. Prospective studies in a general setting are warranted to validate the above‐mentioned endoscopic features of SSP during real‐time colonoscopy and to determine whether these features are useful for the differential diagnosis of SSP.  相似文献   
2.

Background

Photosensitizers used for photodynamic therapy (PDT) to treat dermatologic disease are metabolized into mainly protoporphyrin IX (PpIX), which has five absorption wavelength peaks: 410?nm, 510?nm, 545?nm, 580?nm, and 630?nm. Although only red light around 635?nm and blue light around 400?nm are used as light sources for PDT, the efficiency of PDT might be improved by using multiple wavelengths, including those that correspond to the other absorption peaks of PpIX. Furthermore, because the target disease often occurs on the face, a flexible-type light-source unit that can be fitted to the lesion without unnecessarily exposing the mucous membranes, e.g., the eyes, nostrils, and mouth, is preferred.

Objective

We investigated the efficacy of a flexible light-emitting diode (LED) unit that emits multiple wavelengths to improve PDT effects.

Methods

HaCaT cells were incubated with 5-ALA and subsequently irradiated with either a single wavelength or sequentially with two wavelengths. Cell viability and reactive oxygen species were analyzed. Nude mice were implanted with COLO679 cells by subcutaneous injection into the flank. 5-ALA was subcutaneously injected into the tumor. The tumor was irradiated with 50?J/cm2 (day 0) and assessed daily until day 21.

Results

The synergistic PDT effects of dual-wavelength irradiation and reactive oxygen species production were highest with the 405-nm and 505-nm wavelength combination. This dual wavelength combination was also the most effective in vivo.

Conclusion

We could therefore conclude that dual-wavelength PDT is an efficient strategy for improving the therapeutic effects of PDT. Using a flexible LED unit is expected to achieve more uniform irradiation of uneven areas.  相似文献   
3.
4.
5.
6.
7.
8.

Background

There were few studies assessed the postoperative sarcopenia in patients with cancers. The objective of present study was to assess whether postoperative development of sarcopenia could predict a poor prognosis in patients with adenocarcinoma of esophagogastric junction, (AEG) and upper gastric cancer (UGC).

Methods

Patients with AEG and UGC who were judged as non-sarcopenic before surgery were reassessed the presence of postoperative development of sarcopenia 6 months after surgery. Patients were divided into the development group or non-development group, and clinicopathological factors and prognosis between these two groups were analyzed.

Results

The 5-year overall survival rates were significantly poorer in the development group than non-development group (68.0% vs. 92.6%, P?=?0.0118). Multivariate analyses showed that postoperative development of sarcopenia was an independent prognostic factor for poor overall survival (P?=?0.0237).

Conclusions

Postoperative development of sarcopenia was associated with a poor prognosis in patients with AEG and UGC.  相似文献   
9.
10.
Our aim was to evaluate the long-term skeletal stability of the mandible in 21 patients after orthognathic surgery with physiological positioning. The measurement points SNB, B point (X, Y), Pog (X, Y), and the angle of the ramus were measured on cephalometric photographs to assess skeletal stability preoperatively, immediately after operation, and one and two years postoperatively. In addition, we evaluated the clinical symptoms of disorders of the temporomandibular joint (TMJ). The analysis of the cephalometric photographs showed that SNB, B point X, and Pog X showed no significant differences among the postoperative time points. On the other hand, B point Y and Pog Y showed no significant differences throughout the study period. We compared the angle of the ramus before operation and two years postoperatively, and no significant difference was found. In addition, no cases showed any pathological symptoms of disorders of the TMJ two years postoperatively. The long-term stability after orthognathic surgery with physiological positioning was confirmed, and it seems to be a reliable orthognathic treatment in patients with mandibular prognathism.  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