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   4626篇
  免费   278篇
  国内免费   26篇
耳鼻咽喉   52篇
儿科学   174篇
妇产科学   115篇
基础医学   647篇
口腔科学   104篇
临床医学   349篇
内科学   888篇
皮肤病学   169篇
神经病学   324篇
特种医学   143篇
外科学   645篇
综合类   141篇
一般理论   1篇
预防医学   247篇
眼科学   173篇
药学   445篇
中国医学   35篇
肿瘤学   278篇
  2023年   35篇
  2022年   62篇
  2021年   129篇
  2020年   70篇
  2019年   116篇
  2018年   136篇
  2017年   76篇
  2016年   119篇
  2015年   116篇
  2014年   138篇
  2013年   208篇
  2012年   298篇
  2011年   294篇
  2010年   183篇
  2009年   120篇
  2008年   218篇
  2007年   211篇
  2006年   214篇
  2005年   172篇
  2004年   178篇
  2003年   142篇
  2002年   116篇
  2001年   129篇
  2000年   129篇
  1999年   110篇
  1998年   41篇
  1997年   31篇
  1996年   25篇
  1995年   31篇
  1994年   25篇
  1993年   18篇
  1992年   66篇
  1991年   64篇
  1990年   67篇
  1989年   65篇
  1988年   52篇
  1987年   62篇
  1986年   57篇
  1985年   57篇
  1984年   50篇
  1983年   36篇
  1982年   21篇
  1981年   29篇
  1980年   30篇
  1979年   49篇
  1978年   31篇
  1977年   28篇
  1976年   21篇
  1975年   23篇
  1973年   19篇
排序方式: 共有4930条查询结果,搜索用时 15 毫秒
1.
2.
3.
Coronavirus disease 2019 (COVID-19) is associated with a high risk of mortality and complications in patients with diabetes mellitus. Achieving good glycemic control is very important in diabetic patients to reduce complications and mortality due to COVID-19. Recent studies have shown the mortality benefit and anti-inflammatory effects of Dipeptidyl-peptidase-4 inhibitors (DPP-4i) in diabetic patients with COVID-19. DPP-4i may have a beneficial role in halting the severity of infection primarily by three routes, namely viral entry inhibition, anti-inflammatory and anti-fibrotic effects and glycemic control. This has raised the pro-mising hypothesis that DPP-4i might be an optimal strategy for treating COVID-19 in patients with diabetes. This review aims to summarise the possible therapeutic non-glycemic effects of DPP-4i in diabetic patients diagnosed with COVID-19 in the light of available evidence.  相似文献   
4.
5.
AIM: To evaluate and compare the utility of polymerase chain reaction (PCR) for the diagnosis of tuberculous effusions in children. METHODS: PCR, adenosine deaminase (ADA) activity and absolute lymphocyte count (ALC) were evaluated in the fluid of 31 tuberculous (20 pleural, 8 ascites and 3 pericardial) and 24 non-tuberculous (10 transudtative ascites, 8 empyema thoracis, 3 malignant pleural and 3 pyopericardium) effusions. RESULTS: Fluid PCR for Mycobacterium tuberculosis was positive in 74% of tuberculous effusions, whereas it was falsely positive in 13% of the non-tuberculous group. The mean fluid ADA and ALC values were significantly higher in tuberculous effusions than in non-tuberculous effusions (p<0.001). The sensitivity and specificity of PCR, ADA (> or =38 IU/l) and ALC (> or =275/mm3) were 74% and 88%, 81% and 75%, and 90% and 83%, respectively, in diagnosing tuberculous effusions. The sensitivity of PCR, ADA and ALC was 100%, 100% and 88%, respectively, for confirmed tuberculous effusions. When the two tests were combined (either/or positive), the sensitivity increased (90-100%) at the expense of specificity. When both the tests were positive, then the specificity markedly increased (92-96%), but sensitivity of the tests decreased. CONCLUSION: Fluid PCR alone should not be relied on as a single test; rather, combined analysis with either ADA or ALC could be more useful in the diagnosis of tuberculous effusions in children.  相似文献   
6.
I(indigenous)-compounds are age-related, carcinogen adduct-like, putative indigenous DNA modifications detectable by 32P-postlabeling assay in untreated animals. To investigate the origins of these DNA derivatives, we examined the effects of dietary vitamin E, a natural antioxidant, on I-compounds of rat liver and kidney DNA. Weanling female Sprague-Dawley rats were fed Draper's diets containing 0, 100, 1000, or 10,000 mg/kg alpha-tocopheryl acetate for 6 mo. The DNA from four individual rats of each group was analyzed by a nuclease P1-enhanced version of the 32P-postlabeling assay for DNA adducts. The amount of vitamin E in the liver was measured by high performance liquid chromatography. Rats fed vitamin E-deficient diet (0 mg/kg) showed identical profiles and similar levels of I-compounds as those fed the 100 mg/kg diet. Most I-spots were significantly intensified and one tissue-specific extra spot was found in both liver and kidney DNA of rats fed the 1000 or 10,000 mg/kg vitamin E diet. However, one of the five major I-spots detected in the kidney was weaker in the 1000 and 10,000 mg/kg groups than in the 0 and 100 mg/kg groups. These results show that formation of most I-compounds was not affected by vitamin E-deficient diet, and that long-term feeding of diet containing high levels of vitamin E may cause metabolic alterations leading to an increased formation of DNA-reactive (potentially mutagenic or carcinogenic) electrophiles.  相似文献   
7.
The intestinal uptake of [14C]oxalate, [14C]glyoxylate, and [14C]glycolate are studied in brush border membrane vesicles (BBMV) isolated from vitamin A-deficient and pair-fed control rats. The data obtained indicate that oxalate and its precursors are transported across the BBMV by passive diffusion. The intestinal uptake of glyoxylate and glycolate remains unaltered in vitamin A deficiency, while uptake rate of oxalate was significantly increased (p less than 0.01) in vitamin A-deficient rats as compared to pair-fed controls. In conclusion, the results indicate that vitamin A deficiency leads to hyperabsorption of oxalate through the gut.  相似文献   
8.
Velopharyngeal incompetence (VPI) is a condition of incomplete closure of V.P. port area, normally formed by velum and posterior pharyngeal watt. The condition primarily results in various types of speech defects, which form- the main complaint of the patient. We have studied 10 cases of VPI due to various causes and the speech improvement obtained by flap pharyngoplasty procedures. The results have been evaluated with a follow-up of six months. Highly encouraging results only indicate a more frequent need to undertake such surgery without any hesitation if the ENT surgeon is familiar with and has an adequate exposure to this simple and effective procedure.  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