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   7289篇
  免费   556篇
  国内免费   29篇
耳鼻咽喉   113篇
儿科学   253篇
妇产科学   145篇
基础医学   1053篇
口腔科学   460篇
临床医学   555篇
内科学   1506篇
皮肤病学   175篇
神经病学   508篇
特种医学   267篇
外科学   987篇
综合类   64篇
一般理论   2篇
预防医学   700篇
眼科学   233篇
药学   425篇
中国医学   48篇
肿瘤学   380篇
  2023年   39篇
  2022年   76篇
  2021年   191篇
  2020年   138篇
  2019年   179篇
  2018年   244篇
  2017年   170篇
  2016年   201篇
  2015年   237篇
  2014年   314篇
  2013年   370篇
  2012年   522篇
  2011年   503篇
  2010年   333篇
  2009年   255篇
  2008年   380篇
  2007年   369篇
  2006年   357篇
  2005年   321篇
  2004年   307篇
  2003年   300篇
  2002年   201篇
  2001年   159篇
  2000年   156篇
  1999年   153篇
  1998年   80篇
  1997年   70篇
  1996年   75篇
  1995年   73篇
  1994年   50篇
  1993年   53篇
  1992年   91篇
  1991年   86篇
  1990年   83篇
  1989年   75篇
  1988年   82篇
  1987年   70篇
  1986年   75篇
  1985年   68篇
  1984年   40篇
  1983年   34篇
  1982年   19篇
  1981年   25篇
  1980年   17篇
  1979年   27篇
  1977年   20篇
  1976年   16篇
  1975年   18篇
  1973年   17篇
  1972年   16篇
排序方式: 共有7874条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
6.
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   
7.
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   
8.
Summary A possible basis for risk assessment of human exposure to vibration when using hand-held tools may be to determine the amount of mechanical energy that is absorbed by the hand-arm system. The aim of this investigation was to study the absorption of mechanical energy in the human hand-arm system during exposure to sinusoidal vibration within the frequency range of 20 to 1500 Hz. A handle, specially designed for this type of experiments, was used during the measurements. The influence of various experimental conditions, such as three different hand-arm postures, grip force (25–75 N) and vibration levels (27–53 mm/srms), were studied on eight subjects. The outcome clearly shows that the energy absorption properties of the human hand-arm system are more or less dependent on all of the experimental conditions studied, but mainly to the frequency of the vibration stimuli. Furthermore, the results indicate a non-linear relationship between the energy absorbed and all other variables studies.  相似文献   
9.
10.
The objective of this study was to validate the Spanish version of the Othmer and DeSouza Screening Test for Somatization Disorder. We have designed a validity study using the Standardized Polyvalent Psychiatric Interview, an instrument specifically designed to diagnose psychiatric morbidity in medical settings as the ‘golden rule’. The control group displayed ‘functional’ and ‘presenting’ somatization. The Othmer and DeSouza Screening Test, with a threshold of three symptoms, shows 88% sensitivity, 78% specificity and a misclassification rate of 17%. It is concluded that Othmer and DeSouza's screening test, with a threshold of three symptoms, is a useful tool for the diagnosis of somatization disorder in medical and primary care settings in Spain. Discrepancies with US findings are discussed on a cross-cultural basis.  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