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   221109篇
  免费   3911篇
  国内免费   258篇
耳鼻咽喉   1716篇
儿科学   8007篇
妇产科学   4097篇
基础医学   21178篇
口腔科学   3066篇
临床医学   16320篇
内科学   40764篇
皮肤病学   1606篇
神经病学   19082篇
特种医学   10448篇
外国民族医学   9篇
外科学   36875篇
综合类   3464篇
现状与发展   3篇
一般理论   35篇
预防医学   21123篇
眼科学   4368篇
药学   13280篇
  2篇
中国医学   1038篇
肿瘤学   18797篇
  2023年   477篇
  2022年   1170篇
  2021年   2240篇
  2020年   1341篇
  2019年   1751篇
  2018年   23650篇
  2017年   18576篇
  2016年   20845篇
  2015年   2625篇
  2014年   2993篇
  2013年   3422篇
  2012年   10860篇
  2011年   24612篇
  2010年   20883篇
  2009年   13203篇
  2008年   22069篇
  2007年   24301篇
  2006年   3071篇
  2005年   4408篇
  2004年   5348篇
  2003年   5955篇
  2002年   3923篇
  2001年   806篇
  2000年   866篇
  1999年   584篇
  1998年   457篇
  1997年   370篇
  1996年   269篇
  1995年   248篇
  1994年   235篇
  1993年   180篇
  1992年   250篇
  1991年   328篇
  1990年   326篇
  1989年   272篇
  1988年   202篇
  1987年   196篇
  1986年   159篇
  1985年   188篇
  1984年   134篇
  1983年   95篇
  1982年   99篇
  1981年   84篇
  1980年   105篇
  1979年   92篇
  1978年   74篇
  1977年   58篇
  1975年   66篇
  1974年   74篇
  1938年   65篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Aim: To evaluate the overall effect of disease modifying anti‐rheumatic drug (DMARD) combination therapy in daily practice. Methods: In a retrospective study, 161 consecutive files of patients who attended regular follow‐up sessions, seen from 1998, were analysed. Their data were extracted at baseline, 6 months, 1, 2, 3, 4 and 5 years. American College of Rheumatology ACR70 criteria was chosen for the evaluation of the global result. DMARD combination was methotrexate (7.5–15 mg weekly) and chloroquine (150 mg daily), with low‐dose prednisolone (less than 10 mg daily). In cases of remission, methotrexate was gradually tapered, then prednisolone. Chloroquine was discontinued after 1 year if no recurrence occurred at low‐dose (150 mg every other day). In cases of recurrence at any stage, the treatment scheme was stepped back. Results: The data of 161 patients were analysed. One hundred and six were rheumatoid factor positive (RF+) (66%). ACR 70 for all patients at 6 months follow‐up was 72.5% (95% CI = 7.0); at 1 year, 75.8% (95% CI = 6.7); at 2 years, 72.2% (95% CI = 7.2); at 3 years, 78.9% (95% CI = 6.6); at 4 years, 78.4% (95% CI = 6.9); and at 5 years, 70.6% (95% CI = 8.5). Conclusion: The classical DMARD combination therapy, when used with adequate low‐dose prednisolone, gave an ACR70 response from 71–79%. The efficacy of the treatment did not fade over time. RF– patients did better than RF+ patients, but the difference was not statistically significant.  相似文献   
62.
SPECT with 99mTc-labeled agents is better able to detect viability after nitrate administration. Nitrates induce vasodilation and may increase blood flow to severely hypoperfused but viable myocardium, thereby enhancing tracer delivery and improving the detection of viability. Quantitative data on the changes in blood flow are lacking in SPECT but can be provided by PET. The aim of the present study was to use PET to evaluate whether nitrate administration increases blood flow to chronically dysfunctional but viable myocardium. METHODS: 13N-Ammonia PET was used to quantitatively assess blood flow, and 18F-FDG PET was used as the gold standard to detect viable myocardium. Twenty-five patients with chronic ischemic left ventricular dysfunction underwent 13N-ammonia PET at rest and after nitrate administration. RESULTS: A significant increase in nitrate-enhanced blood flow was observed in viable segments (from 0.55 +/- 0.15 to 0.68 +/- 0.24 mL/min/g, P < 0.05). No statistically significant change in blood flow was observed in nonviable segments (0.60 +/- 0.20 vs. 0.55 +/- 0.18 mL/min/g). A ratio of at least 1.1 for nitrate-enhanced flow to resting flow allowed optimal detection of viable myocardium, yielding a sensitivity of 82% with a specificity of 100%. CONCLUSION: 13N-Ammonia PET showed a significant increase in nitrate-enhanced blood flow in viable myocardium, whereas blood flow remained unchanged after nitrate administration in nonviable myocardium. Nitrate use during myocardial perfusion imaging will lead to improved assessment of myocardial viability.  相似文献   
63.
64.
65.
BACKGROUND: Abnormalities in calcium and vitamin D metabolism have been reported after bariatric surgery. The purpose of this study was to evaluate vitamin D nutritional status among morbidly obese patients before gastric bypass surgery. METHODS: We prospectively studied 279 morbidly obese patients seeking gastric bypass surgery for vitamin D nutritional status as assessed by serum 25-hydroxyvitamin D level. In addition, serum samples were analyzed for calcium, alkaline phosphatase (AP), intact parathyroid hormone (PTH), and 1,25-dihydroxyvitamin D. RESULTS: Mean patient age was 43 +/- 9 years; 87% of the study patients were women, and 72% were white. Serum calcium and AP levels were normal in 88% and 89% of the patients, respectively. Vitamin D depletion, defined as serum 25-hydroxyvitamin D level 相似文献   
66.
67.
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   
68.
69.
70.
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