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   389726篇
  免费   48408篇
  国内免费   3291篇
耳鼻咽喉   7518篇
儿科学   11637篇
妇产科学   6857篇
基础医学   35837篇
口腔科学   5971篇
临床医学   50297篇
内科学   96870篇
皮肤病学   10555篇
神经病学   37886篇
特种医学   14322篇
外国民族医学   11篇
外科学   76458篇
综合类   3675篇
现状与发展   72篇
一般理论   318篇
预防医学   27801篇
眼科学   9699篇
药学   17736篇
  6篇
中国医学   367篇
肿瘤学   27532篇
  2023年   5661篇
  2022年   3352篇
  2021年   8168篇
  2020年   8811篇
  2019年   7220篇
  2018年   12820篇
  2017年   11271篇
  2016年   12716篇
  2015年   13640篇
  2014年   23046篇
  2013年   26351篇
  2012年   22997篇
  2011年   23879篇
  2010年   20258篇
  2009年   22669篇
  2008年   21942篇
  2007年   21092篇
  2006年   23296篇
  2005年   20649篇
  2004年   18945篇
  2003年   16824篇
  2002年   15947篇
  2001年   5662篇
  2000年   4393篇
  1999年   5251篇
  1998年   6457篇
  1997年   5758篇
  1996年   5299篇
  1995年   5054篇
  1994年   3568篇
  1993年   3051篇
  1992年   2560篇
  1991年   2473篇
  1990年   1984篇
  1989年   2078篇
  1988年   1928篇
  1987年   1741篇
  1986年   1784篇
  1985年   1642篇
  1984年   1731篇
  1983年   1602篇
  1982年   1851篇
  1981年   1695篇
  1980年   1494篇
  1979年   1001篇
  1978年   1057篇
  1977年   1018篇
  1976年   815篇
  1975年   736篇
  1974年   690篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
Background:  Melatonin is gaining popularity as a sedative agent with children. This study sought to characterise this practice more precisely as well as examine aspects of its safety and efficacy in order to develop treatment guidelines.
Method:  Postal surveys of two groups of psychiatrists: generic child psychiatrists and psychiatrists who regularly treat learning disabled children.
Results:  Both groups (all of the specialists and 81% of the non-specialists) reported regular but not frequent use of melatonin in their usual practice, mostly for night-settling sleep problems refractory to behavioural modification strategies, commonly in the context of neurodevelopmental disability (especially autism). Treatment was described as being 'usually successful' and side-effects were highly infrequent and mild in nature. Variations in most prescribing practices were identified (dosage, timing).
Conclusions:  Melatonin appears to represent a useful and relatively safe drug when used in specific circumstances; however, the evidence-base underpinning its use, particularly over the long-term, remains modest. Thus caution and clinical audit of practice is required.  相似文献   
994.
OBJECTIVES: 1) To assess, with a peripheral magnetic resonance imaging system (pMRI), the prevalence of bony and soft tissue abnormalities in the knee joints of normal subjects, osteoarthritis (OA) patients, and individuals who have suffered an anterior cruciate ligament (ACL) rupture; and 2) to compare the prevalence among groups. METHODS: Magnetic resonance (MR) images of 28 healthy, 32 OA, and 26 ACL damaged knees were acquired with a 1.0-T pMRI system. Two radiologists graded the presence and severity of 9 MR image features: cartilage degeneration, osteophytes, subchondral cyst, bone marrow edema, meniscal abnormality, ligament integrity, loose bodies, popliteal cysts, and joint effusion. RESULTS: Ten of 28 healthy (35.7%), 24 of 26 ACL (92.3%), and all OA knees (100%) showed prevalent cartilage defects; 5 healthy (17.9%), 20 ACL (76.9%), and all OA knees (100%) had osteophytes; and 9 normal (32.1%), 21 ACL (80.8%), and 29 OA knees (90.6%) had meniscal abnormalities. One-half of the knees in the OA group (16 of 32, 50%) had subchondral cysts, and almost one-half had bone marrow edema (15 of 32, 46.9%). These features were not common in the ACL group (7.7%, and 11.5%, respectively) and were not observed in healthy knees. The OA group had the most severe cartilage defects, osteophytes, bone marrow edema, subchondral cysts, and meniscal abnormalities; the ACL group showed more severe cartilage defects, osteophytes, and meniscal abnormalities than did normal subjects. CONCLUSION: The results suggest that knees that have sustained ACL damage have OA-like reatures; most subjects (19 of 26, 73.1%) could be identified as in the early stage of OA. The prominent abnormalities present in ACL-damaged knees are cartilage defects, osteophytes, and meniscal abnormalities.  相似文献   
995.
996.
BACKGROUND: Studies have reported an increase in median Lipoprotein (Lp) (a) in patients with high molecular weight (HMW) apolipoprotein (apo) (a) isoforms and renal impairment. Some studies identify Lp (a) levels as a risk factor for vascular disease in renal failure whilst others have demonstrated an association with apo (a) isoform type and vascular disease. METHODS: A total of 239 patients at end-stage renal failure (ESRF) were studied prior to the initiation of dialysis. Blood was taken for Lp (a) levels and apo (a) isoforms. Clinical vascular disease (CVD) was assessed on the basis of clinical history and Rose questionnaire. The control group for Lp (a) levels consisted of 228 healthy volunteers. RESULTS: Despite a higher median Lp (a) level in those with HMW isoforms, 30% of patients had Lp (a) levels <10 mg/dl. Overall, 49% patients were identified as having CVD. Diabetes, smoking history and Lp (a) levels were significantly associated with CVD in logistic regression analysis, although when patients with low molecular weight (LMW) and HMW isoforms were analysed separately, Lp (a) levels were not significantly associated with CVD in those with LMW isoforms. The rates of CVD in those with HMW isoform and low Lp (a) levels were significantly lower than those with HMW isoforms and elevated Lp (a) levels, 34 vs 57% (P < 0.01). CONCLUSIONS: Although median Lp (a) levels in those patients at ESRF with HMW isoforms are higher than controls, in a third of such patients Lp (a) levels remain relatively low. These patients have lower rates of CVD than those with high levels of Lp (a).  相似文献   
997.
998.
999.
1000.
The World Wide Web creates new challenges and opportunities for medical educators. Prominent among these are the lack of consistent standards by which to evaluate web-based educational tools. We present the instrument that was used to review web-based innovations in medical education submissions to the 2003 Society of General Internal Medicine (SGIM) national meeting, and discuss the process used by the SGIM web-based clinical curriculum interest group to develop the instrument. The 5 highest-ranked submissions are summarized with commentary from the reviewers.  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