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   57284篇
  免费   4955篇
  国内免费   1606篇
耳鼻咽喉   301篇
儿科学   1194篇
妇产科学   528篇
基础医学   7725篇
口腔科学   674篇
临床医学   3164篇
内科学   7267篇
皮肤病学   1143篇
神经病学   5166篇
特种医学   2427篇
外国民族医学   13篇
外科学   4545篇
综合类   5650篇
现状与发展   4篇
预防医学   3471篇
眼科学   592篇
药学   12091篇
  22篇
中国医学   1918篇
肿瘤学   5950篇
  2024年   131篇
  2023年   1167篇
  2022年   2330篇
  2021年   2390篇
  2020年   1975篇
  2019年   2319篇
  2018年   2222篇
  2017年   2047篇
  2016年   1731篇
  2015年   1873篇
  2014年   3102篇
  2013年   3676篇
  2012年   2845篇
  2011年   3360篇
  2010年   2784篇
  2009年   2617篇
  2008年   2687篇
  2007年   2472篇
  2006年   2205篇
  2005年   1854篇
  2004年   1772篇
  2003年   1563篇
  2002年   1195篇
  2001年   949篇
  2000年   977篇
  1999年   833篇
  1998年   817篇
  1997年   747篇
  1996年   642篇
  1995年   606篇
  1994年   526篇
  1993年   511篇
  1992年   479篇
  1991年   437篇
  1990年   379篇
  1989年   368篇
  1988年   293篇
  1987年   293篇
  1986年   278篇
  1985年   562篇
  1984年   652篇
  1983年   420篇
  1982年   489篇
  1981年   435篇
  1980年   377篇
  1979年   351篇
  1978年   281篇
  1977年   202篇
  1976年   174篇
  1975年   138篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.

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   
5.
6.
7.
8.
目的:探讨3D-CRT 低剂量区 V5体积的大小对非小细胞肺癌患者肺功能的影响。方法:收集我院肿瘤科2014年4月~2015年10月收治的46例首次行三维适形放射治疗且顺利完成治疗的非小细胞肺癌患者,对每例患者分别在治疗前以及治疗后的1、3个月进行肺功能检测,分析3D-CRT 低剂量区 V5体积的大小与肺功能变化之间的关系。结果:放疗后1个月的 FEV1%、FVC%值明显高于放疗前且差异均具有显著性。放疗后1个月、3个月的 DLCO%值明显低于放疗前,且放疗前的与放疗后3个月的差异具有显著性;V5≦45%、45%55%三组放疗前后的 FEV1%值和 FVC%值比较差异均不具有显著性。V5≦45%、45%55%三组放疗前后的 DLCO%值均呈逐渐下降趋势,且 V5>55%组的放疗前后 DLCO%值比较差异具有显著性。而 V5≦45%组和45%55%时,DLCO%值降低的趋势更加显著。  相似文献   
9.
10.
PurposeTo determine if cone-beam CT and digital subtraction angiography analysis of pelvic arterial anatomy has predictive value for radiation exposure and technical success of prostatic artery embolization (PAE).Materials and MethodsThis prospective, nonrandomized, single-center study included 104 consecutive patients with lower urinary tract symptoms secondary to benign prostatic hyperplasia. Cone-beam CT was performed in 160/208 (76.9%) hemipelves to determine prostatic artery (PA) origin. Classification of pelvic arterial tortuosity was possible in 73/104 (70.2%) patients. Learning curves of 2 interventionalists who performed 86.5% of PAEs were analyzed.ResultsTortuosity of pelvic arteries was classified as mild in 25 (34.2%) patients median age 64 years, moderate in 40 (54.8%) patients median age 69 years, and severe in 8 (11.0%) patients median age 70 years (mild vs moderate, P = .002; mild vs severe, P = .019); median fluoroscopy times were 24, 36, and 46 minutes (P = .008, P = .023); median contrast volumes were 105, 122.5, and 142 mL (P = .029, P = .064); and bilateral PAE rates were 84.0%, 77.5%, and 62.5% (P = .437), respectively. PA origin from superior vesical artery was most frequent (27.5%) and showed higher dose area product (median 402.4 vs 218 Gy ∙ cm2, P = .033) and fluoroscopy time (median 42.5 vs 27 min, P = .01) compared with PA origin from obturator artery, which was least frequent. Interventionalist experience revealed significant impact on procedure times (median 159 vs 130 min, P = .006).ConclusionsTortuosity of pelvic arteries was more frequent in older patients and predicted worse technical outcomes of PAE. PA origin from obturator artery was associated with lower dose area product and fluoroscopy time, especially compared with PA origin from superior vesical artery. Interventionalist experience showed significant influence on technical outcome.  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