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   6505篇
  免费   454篇
  国内免费   42篇
耳鼻咽喉   107篇
儿科学   202篇
妇产科学   121篇
基础医学   901篇
口腔科学   432篇
临床医学   510篇
内科学   1345篇
皮肤病学   144篇
神经病学   444篇
特种医学   301篇
外科学   879篇
综合类   32篇
一般理论   2篇
预防医学   630篇
眼科学   208篇
药学   410篇
中国医学   48篇
肿瘤学   285篇
  2023年   41篇
  2022年   102篇
  2021年   185篇
  2020年   126篇
  2019年   162篇
  2018年   213篇
  2017年   153篇
  2016年   169篇
  2015年   201篇
  2014年   274篇
  2013年   321篇
  2012年   477篇
  2011年   450篇
  2010年   276篇
  2009年   194篇
  2008年   322篇
  2007年   322篇
  2006年   303篇
  2005年   292篇
  2004年   274篇
  2003年   269篇
  2002年   177篇
  2001年   139篇
  2000年   141篇
  1999年   131篇
  1998年   63篇
  1997年   51篇
  1996年   68篇
  1995年   55篇
  1994年   45篇
  1993年   49篇
  1992年   85篇
  1991年   72篇
  1990年   82篇
  1989年   69篇
  1988年   80篇
  1987年   79篇
  1986年   59篇
  1985年   66篇
  1984年   36篇
  1983年   29篇
  1982年   32篇
  1981年   22篇
  1980年   19篇
  1979年   26篇
  1977年   18篇
  1976年   25篇
  1975年   22篇
  1973年   16篇
  1972年   15篇
排序方式: 共有7001条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
Hysterosalpingography was performed in 31 patients by means of a low-dose scanning-beam digital radiographic system. The technique permits adequate evaluation of gynecologic abnormalities while allowing significant reduction in radiation: 2.4-mR (6.1 X 10(-7) C/kg) exposure to the skin and 0.7-mrad (7 X 10(-6) Gy) mean dose to the ovaries per image obtained. Sixteen patients demonstrated readily recognizable and documented abnormalities, corroborated by laparoscopy, laparotomy, or other supportive evidence.  相似文献   
6.
7.
BACKGROUND: The role of local excision for pT2 distal rectal cancer has been challenged because of the observation of high rates of lymph node metastases and local failure. However, neoadjuvant chemoradiation therapy (CRT) has led to increased local disease control and significant tumor downstaging, possibly decreasing rates of lymph node metastases. In this setting, a possible role for local excision of ypT2 has been suggested. METHODS: A total of 401 patients with distal rectal cancer underwent neoadjuvant CRT. Tumor response assessment was performed after at least 8 weeks from CRT completion. One hundred and twelve patients with complete clinical response were not immediately operated on and were excluded from the study, and 289 patients with incomplete clinical response were managed by radical surgery. Patients with final pathological stage ypT2 were analyzed to determine the risk of unfavorable pathological features that could represent unacceptable risk for local failure after local excision. RESULTS: Eighty-eight (30%) patients had ypT2 rectal cancer. Final ypT status was not associated with pretreatment radiological staging (p = 0.62). ypT status was significantly associated with the risk of lymph node metastases, risk of perineural and vascular invasion, and recurrence (p = 0.001). Lymph node metastases were present in 19% of patients with ypT2 rectal cancer. The risk of lymph node metastases in ypT2 was associated with the presence of perineural invasion (47% vs 4%; p = <0.001), vascular invasion (59% vs 6%; p < 0.001), and decreased mean interval CRT surgery (12 vs 18 weeks; p < 0.001), but not with mean tumor size (3.2 vs 3.1 cm; p = 0.8). Disease-free and overall survival rates were significantly better for patients with ypT2N0 (p = 0.02 and 0.006, respectively). Fifty-five (63%) patients with ypT2 had at least one unfavorable pathological feature for local excision (lymph node metastases, vascular or perineural invasion, mucinous type or tumor size >3 cm). CONCLUSION: Lymph node metastases were present in 19% of patients with ypT2 and were significantly associated with poor overall and disease-free survival rates. The risk of lymph node metastases could not be predicted by radiological staging or tumor size. Radical surgery should be considered the standard treatment option for ypT2 rectal cancer after CRT.  相似文献   
8.
Several studies have reported that the heart is severely affected by chronic malnutrition. However, the influence of these alterations on cardiac function remains unclear. The aim of this study was to evaluate the effects of subacute starvation on the heart chronotropic response to a beta-adrenergic agonist (isoproterenol). Twelve rats were fed rat chow ad libitum or a 50%-restricted diet for 17 days. The rats were killed, the right atrium was isolated and incubated, and in vitro spontaneous cardiac contractions and frequency were registered. Cumulative doses of isoproterenol were added to the solution until maximal cardiac frequency was achieved. A deficit of 25% in the weight gain was observed in study rats compared with controls (92.6 +/- 10.2 vs. 113.8 +/- 19.2 g, p less than 0.05). Mean daily food intake was 4.8 +/- 0.1 and 9.8 +/- 0.5 g/day for semistarved and control rats, respectively. The in vitro cardiac frequency of the semistarved rats was similar to that of controls (290 +/- 15 and 305 +/- 23 beats/min, respectively, NS). However, when isoproterenol was added to the solution, maximal cardiac frequency of the semistarved rats (435 +/- 51 beats/min) was lower than that of control rats (508 +/- 34 beats/min, p less than 0.005). These findings suggest that subacute starvation may alter the cardiac response to beta-adrenergic agonists.  相似文献   
9.
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