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   36989篇
  免费   1811篇
  国内免费   166篇
耳鼻咽喉   487篇
儿科学   664篇
妇产科学   428篇
基础医学   4640篇
口腔科学   1160篇
临床医学   2502篇
内科学   8503篇
皮肤病学   784篇
神经病学   3487篇
特种医学   1922篇
外国民族医学   1篇
外科学   5703篇
综合类   127篇
一般理论   6篇
预防医学   1152篇
眼科学   774篇
药学   2362篇
中国医学   77篇
肿瘤学   4187篇
  2023年   161篇
  2022年   316篇
  2021年   594篇
  2020年   357篇
  2019年   457篇
  2018年   581篇
  2017年   493篇
  2016年   636篇
  2015年   603篇
  2014年   814篇
  2013年   985篇
  2012年   1627篇
  2011年   1689篇
  2010年   1022篇
  2009年   879篇
  2008年   1521篇
  2007年   1775篇
  2006年   1642篇
  2005年   1610篇
  2004年   1626篇
  2003年   1525篇
  2002年   1568篇
  2001年   1336篇
  2000年   1433篇
  1999年   1294篇
  1998年   504篇
  1997年   422篇
  1996年   393篇
  1995年   324篇
  1994年   325篇
  1993年   307篇
  1992年   1010篇
  1991年   862篇
  1990年   828篇
  1989年   822篇
  1988年   769篇
  1987年   773篇
  1986年   677篇
  1985年   628篇
  1984年   435篇
  1983年   352篇
  1979年   305篇
  1978年   211篇
  1977年   188篇
  1974年   194篇
  1973年   167篇
  1972年   173篇
  1971年   181篇
  1970年   162篇
  1969年   179篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
We report a case of a diaphragmatic hernia after a heart transplant operation. A 43-year-old woman, who underwent orthotropic heart transplantation for hypertrophic cadiomyopathy two year earlier, presented with vomiting and epigastric pain. A computed tomography scan showed that the stomach and transverse colon were dislocated in the left thoracic cavity. We diagnosed left diaphragmatic hernia incarceration and performed laparoscopic repair of the diaphragmatic hernia. A 12 × 8 cm diaphragmatic defect was found intraoperatively on the ventrolateral aspect of the left diaphragm, and the stomach with volvulus had herniated into the thorax through the defect. The hernia was considered to be iatrogenic. The diaphragmatic defect was large, and the diaphragm was thinning. We closed the defect by mesh repair. Laparoscopic mesh repair of the diaphragmatic hernia could be performed safely and with minimal invasiveness.  相似文献   
6.
7.
8.
We prospectively evaluated the effectiveness of contrast-enhanced ultrasonography (CEUS) for differentiation of benign versus malignant portal vein thrombosis (PVT). We studied a total of 43 patients with chronic liver disease, hepatocellular carcinoma-suggestive nodules and confirmed PVT, in whom the nature of the PVT was confirmed by follow-up imaging (US, computed tomography and/or magnetic resonance imaging) performed up to 6 mo after CEUS. PVT was assessed by US, Doppler US and CEUS with respect to vessel wall disruption and/or invasion, color Doppler vascularization, pulsed Doppler vascularization pattern and CEUS enhancement and vascularization pattern, and thrombi were classified as benign or malignant based on these findings. Follow-up studies revealed malignant PVT in 22 of the 43 patients (51%) and benign PVT in 21 patients (49%). CEUS findings were consistent with follow-up studies in 41 of the 43 patients (95%), with κ?=?0.903 (p < 0.0001), sensitivity?=?91% and specificity?=?100%, indicating that CEUS can be confidently used to differentiate benign from malignant portal vein thrombosis in the setting of chronic liver disease.  相似文献   
9.
10.
Purpose: Orthodontic tooth movement occurs during the bone remodeling induced by therapeutic mechanical strain. It is important to investigate the relation between the strength of mechanical stress and bone formation activity. The aim of this study was to determine the effect of high-magnitude mechanical strain on bone formation in detail.

Materials and methods: Osteoblast-like cells isolated from fetal rat calvariae were loaded with 18% cyclic tension force (TF) for 48?h. To phenotypically investigate the effect of TF, we measured the number and the size of bone nodules stained by von Kossa technique on day 21 after cell seeding and determined the calcium content of bone nodules on day 14. Furthermore, we examined the gene expression of BMP-2, Runx2 and Msx2, which are important factors for bone nodule formation, on days 1, 4 and 7 after TF loading.

Results: The maximum bone nodule size in the control group was 1620 and 719?μm in the TF group. Furthermore, the mean number of bone nodules sized over 360?μm in the TF group was significantly decreased compared to the control group. The calcium content was also significantly decreased to 42% by TF loading. The mRNA expression of BMP-2, Runx2 and Msx2 was decreased 1 and 4 days after TF loading.

Conclusion: The differentiation of bone forming progenitor cells into bone nodule forming cells was inhibited by TF due to the decreased expression of bone formation related factors such as BMP-2, Runx2 and Msx2.  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