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   23155篇
  免费   1090篇
  国内免费   118篇
耳鼻咽喉   263篇
儿科学   393篇
妇产科学   270篇
基础医学   3259篇
口腔科学   475篇
临床医学   1620篇
内科学   6231篇
皮肤病学   366篇
神经病学   1895篇
特种医学   920篇
外科学   3485篇
综合类   91篇
一般理论   2篇
预防医学   618篇
眼科学   451篇
药学   1657篇
中国医学   97篇
肿瘤学   2270篇
  2023年   118篇
  2022年   223篇
  2021年   361篇
  2020年   169篇
  2019年   284篇
  2018年   337篇
  2017年   271篇
  2016年   325篇
  2015年   419篇
  2014年   523篇
  2013年   667篇
  2012年   1049篇
  2011年   1124篇
  2010年   629篇
  2009年   535篇
  2008年   961篇
  2007年   1116篇
  2006年   1095篇
  2005年   1119篇
  2004年   1089篇
  2003年   1031篇
  2002年   1095篇
  2001年   754篇
  2000年   783篇
  1999年   743篇
  1998年   314篇
  1997年   266篇
  1996年   277篇
  1995年   237篇
  1994年   236篇
  1993年   186篇
  1992年   567篇
  1991年   558篇
  1990年   519篇
  1989年   486篇
  1988年   385篇
  1987年   358篇
  1986年   374篇
  1985年   345篇
  1984年   249篇
  1983年   211篇
  1982年   127篇
  1981年   121篇
  1980年   117篇
  1979年   188篇
  1978年   135篇
  1977年   126篇
  1974年   106篇
  1972年   111篇
  1968年   105篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.

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   
2.
3.
4.

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   
5.
<正>Stroke is a leading cause of mortality and severe neurological disability worldwide; however, curative therapeutic options are limited. Although recanalization therapy using endovascular thrombectomy has demonstrated great benefits in the functional outcome of patients with acute ischemic stroke, the rate of excellent clinical outcomes remains limited. Therefore, the current recanalization  相似文献   
6.
7.
Syphilis is a sexually transmitted disease caused by Treponema pallidum. Syphilitic aortitis might coexist in a dysfunctional aortic valve, but the etiology remains unclear, because microbiological diagnosis is difficult. A 62-year-old man with low-grade fever was diagnosed with aortitis and infective endocarditis, due to Treponema pallidum infection, using polymerase chain reaction analysis. This case suggests that syphilis might cause infective endocarditis.  相似文献   
8.
9.
10.
The feasibility of ventilation imaging with hyperpolarized (HP) 129Xe MRI has been investigated for quantitative and regional assessment of ventilation in spontaneously breathing mice. The multiple breath ventilation imaging technique was modified to the protocol of spontaneous inhalation of HP 129Xe delivered continuously from a 129Xe polarizer. A series of 129Xe ventilation images was obtained by varying the number of breaths before the 129Xe lung imaging. The fractional ventilation, r, was successfully evaluated for spontaneously breathing mice. An attempt was made to detect ventilation dysfunction in the emphysematous mouse lung induced by intratracheal administration of porcine pancreatic elastase (PPE). As a result, the distribution of fractional ventilation could be visualized by the r map. Significant dysfunction of ventilation was quantitatively identified in the PPE‐treated group. The whole‐lung r value of 0.34 ± 0.01 for control mice (N = 4) was significantly reduced, to 0.25 ± 0.07, in PPE‐treated mice (N = 4) (p = 0.038). This study is the first application of multiple breath ventilation imaging to spontaneously breathing mice, and shows that this methodology is sensitive to differences in the pulmonary ventilation. This methodology is expected to improve simplicity as well as noninvasiveness when assessing regional ventilation in small rodents. Copyright © 2014 John Wiley & Sons, Ltd.  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