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   30102篇
  免费   1912篇
  国内免费   81篇
耳鼻咽喉   202篇
儿科学   1016篇
妇产科学   792篇
基础医学   4497篇
口腔科学   495篇
临床医学   4104篇
内科学   5621篇
皮肤病学   532篇
神经病学   3109篇
特种医学   761篇
外科学   2595篇
综合类   221篇
一般理论   27篇
预防医学   3368篇
眼科学   492篇
药学   2133篇
  1篇
中国医学   63篇
肿瘤学   2066篇
  2023年   224篇
  2022年   412篇
  2021年   768篇
  2020年   497篇
  2019年   692篇
  2018年   852篇
  2017年   587篇
  2016年   652篇
  2015年   842篇
  2014年   983篇
  2013年   1577篇
  2012年   2189篇
  2011年   2376篇
  2010年   1229篇
  2009年   1167篇
  2008年   1920篇
  2007年   2007篇
  2006年   1917篇
  2005年   1823篇
  2004年   1722篇
  2003年   1564篇
  2002年   1407篇
  2001年   316篇
  2000年   278篇
  1999年   305篇
  1998年   284篇
  1997年   202篇
  1996年   203篇
  1995年   144篇
  1994年   152篇
  1993年   144篇
  1992年   173篇
  1991年   206篇
  1990年   205篇
  1989年   176篇
  1988年   137篇
  1987年   121篇
  1986年   131篇
  1985年   129篇
  1984年   131篇
  1983年   110篇
  1982年   113篇
  1981年   86篇
  1980年   84篇
  1979年   96篇
  1978年   68篇
  1977年   82篇
  1976年   64篇
  1974年   57篇
  1972年   57篇
排序方式: 共有10000条查询结果,搜索用时 20 毫秒
51.
Piribedil is a non-ergot D2/D3 agonist with a significant antagonist action on alpha2A and alpha2C adrenergic receptor subtypes. This double-blind placebo-controlled study was undertaken to confirm the efficacy of 150 mg/day piribedil po in improving motor symptoms of idiopathic Parkinson's disease (PD) in nonfluctuating patients insufficiently controlled by a stable daily dose of levodopa (L-dopa). Efficacy was assessed using the Unified Parkinson's Disease Rating Scale (UPDRS) III score as primary criterion over 4 months. A second comparison was planned at 6 months, after possible adjustment of L-dopa. At 4 months, the rate of response, defined as a 30% decrease from baseline on UPDRS III score, was significantly greater with piribedil compared with placebo (56.4% vs. 37.7%; P = 0.040). At 6 months, the better efficacy of piribedil was maintained (61.8% of responders vs. 39.6% on placebo; P = 0.020). The difference between groups on UPDRS III change from baseline reached statistical significance only at 6 months: -10.0 points in the piribedil group vs. -6.7 points in the placebo group (P = 0.037). Secondary end-points were not significantly different. The most frequently reported adverse events were gastrointestinal symptoms (27 of 61 patients in the piribedil group vs. 13 of 54 patients in the placebo group). In conclusion, a 6-month oral administration of 150 mg/day piribedil in combination with L-dopa is well tolerated, except for minor gastrointestinal symptoms at the beginning of the treatment and significantly improves motor symptoms compared with placebo in PD nonfluctuating patients.  相似文献   
52.
At the present time, there are many fundamental issues coming from the Department of Health or from other national organizations, which will have an effect on the future development of the dietetic profession. The British Diatetic Association (BDA) Professional Development Committee will consider these issues, as and when appropriate, and will publish the information in the form of Briefing Papers.
The first Briefing Paper on 'Quality Assurance' was published by the BDA in November 1989. The second on 'Measuring clinical outcome' is published below. In each case the opinion of BDA members and specialist groups has been sought and the Professional Development Committee wishes to thank individuals and the specialist groups for their comments.
The Briefing Papers are intended to provide information and promote discussion among the membership. I would welcome further comments from readers, which may be directed to the British Dietetic Association Office.  相似文献   
53.
54.
Clinical practice guidelines have emerged as a reality for medical practitioners over the past 20 years. Although virtually all groups interested in the development of practice guidelines hope for improvements in patient care, secondary expectations vary widely among those using them. Their use in daily practice by physicians has met with resistance from barriers including concerns of “cookbook” medicine, a loss of autonomy, and increased professional liability. The recent experience of the ACR in addressing these challenges illustrates that physicians are receptive to steps perceived to mitigate the risks accompanying the use of guidelines as well as to efforts to increase their understanding of implementing guidelines in clinical practice. The experiences of other medical societies and an inventory of future trends reveal additional challenges associated with the use of practice guidelines, as third parties look to guidelines as points of reference for gauging the performance of health care providers.  相似文献   
55.
56.
A series of studies designed to define the requirement of normal infants for sulfur-containing amino acids (methionine, cystine) was conducted with formulas providing 3.0, 2.8, 2.6, 2.2 or 1.8 g of isolated soy protein per 100 kcal. The formulas were fed with or without a methionine supplement. Adequacy of the diet was determined by measurement of growth, serum chemical indices and nitrogen balance. Nitrogen balance demonstrated a beneficial effect of methionine supplementation only at the lowest protein concentration (1.8 g/100 kcal). However, measurement of weight gain and/or serum concentrations of urea nitrogen and albumin clearly showed a beneficial effect of methionine supplementation at protein concentrations of 2.2 and 2.6 g/100 kcal. Intakes of sulfur-containing amino acids of 435 and 495 mumol/100 kcal therefore appear inadequate. At higher intakes of protein (2.8 and 3.0 g/100 kcal) there was no beneficial effect of methionine supplementation. Possible exceptions were male infants provided with 3.0 g protein per 100 kcal, in whom weight gain between 8 and 56 d of age was significantly (P less than 0.05) greater with than without a methionine supplement. Based on intakes of sulfur-containing amino acids from the formula providing 2.8 g of isolated soy protein per 100 kcal without methionine supplementation, we conclude that for male infants older than 56 d the requirement for sulfur-containing amino acids is no more than 588 mumol/100 kcal when intake of methionine is 264 mumol/100 kcal. However, it seems possible that such intake fails to meet the requirement in male infants less than 56 d of age. For female infants, regardless of age, 533 mumol/100 of sulfur-containing amino acids per 100 kcal meet the requirement when intake of methionine is 239 mumol/100 kcal.  相似文献   
57.
58.
The combination of small-animal PET and MRI data provides quantitative in vivo insights into cardiac pathophysiology, integrating information on biology and morphology. We sought to determine the feasibility of PET and MRI for the quantification of ischemic injury in the rat model. METHODS: Fourteen healthy male Wistar rats were studied with 18F-FDG PET and cine MRI. Myocardial viability was determined in a transmural myocardial infarction model in 12 additional rats, using 18F-FDG PET and delayed-enhancement MRI with gadolinium-diethylenetriaminepentaacetic acid. All PET was acquired with a dedicated small-animal PET system. MRI was performed on a 1.5-T clinical tomograph with a dedicated small-animal electrocardiographic triggering device and a small surface coil. RESULTS: In normal rats, 18F-FDG uptake was homogeneous throughout the left ventricle. The lowest mean uptake of the 18F-FDG was found in the apical regions (79% +/- 6.0% of maximum) and the highest uptake was in the anterior wall (93% +/- 4.3 % of maximum). Myocardial infarct size as determined by histology correlated well with defects of glucose metabolism obtained with 18F-FDG PET (r = 0.89) and also with delayed-enhancement MRI (r = 0.91). Left ventricular ejection fraction in normal rats measured by cine MRI was 57% +/- 5.4% and decreased to 38% +/- 12.9% (P < 0.001) in the myocardial infarction model. CONCLUSION: Integrating information from small-animal PET and clinical MRI instrumentation allows for the quantitative assessment of cardiac function and infarct size in the rat model. The MRI measurements of scar can be complemented by metabolic imaging, addressing the extent and severity of ischemic injury and providing endpoints for therapeutic interventions.  相似文献   
59.
PURPOSE: The objective of this survey was to examine the services offered by multidisciplinary pain treatment facilities (MPTFs) across Canada and to compare access to care at these MPTFs. METHODS: A MPTF was defined as a clinic that advertised specialized multidisciplinary services for the diagnosis and management of patients with chronic pain, having a minimum of three different health care disciplines (including at least one medical speciality) available and integrated within the facility. The search method included approaching all hospital and rehabilitation centre administrators in Canada, the Insurance Bureau of Canada, the Workplace Safety and Insurance Board or similar body in each province. Designated investigators were responsible for confirming and supplementing MPTFs from the preliminary list for each province. Administrative leads at each eligible MPTF were asked to complete a detailed questionnaire regarding their MPTF infrastructure, clinical, research, teaching and administrative activities. RESULTS: Completed survey forms were received from 102 MPTFs (response rate 85%) with 80% concentrated in major cities, and none in Prince Edward Island and the Territories. The MPTFs offer a wide variety of treatments including non-pharmacological modalities such as interventional, physical and psychological therapy. The median wait time for a first appointment in public MPTFs is six months, which is approximately 12 times longer than non-public MPTFs. Eighteen pain fellowship programs exist in Canadian MPTFs and 64% engage in some form of research activities CONCLUSION: Canadian MPTFs are unable to meet clinical demands of patients suffering from chronic pain, both in terms of regional accessibility and reasonable wait time for patients' first appointment.  相似文献   
60.
A study was made of glucose tolerance and insulin secretion in 33 persons who later developed insulin-dependent diabetes (aged 4-24 years) and observation continued further in the first years after manifestation. Patients who developed the typical labile type of diabetes were of normal weight and had either normal glucose tolerance tests before diagnosis or had impaired glucose tolerance (IGT) for a short interval of 2-16 months. Subjects with IGT over a significantly (p less than 0.01) longer period of 32.30 +/- 6.25 (normal body weight) or 94.71 +/- 20.62 (obese) months developed a milder form of diabetes with retarded insulin dependency in obese subjects. The severe and mild form of IDDM are distinct with respect to insulin requirement (0.75 +/- 0.03 or 0.28 +/- 0.04 U/kg b.w., P less than 0.01) and glucagon stimulated C-peptide (0.18 +/- 0.05 or 1.41 +/- 0.27, P less than 0.01) in the first 2.5-3.5 years after onset. The two forms were not different regarding HLA-DR antigens. Islet cell surface antibodies investigated in 15 probands at 27 occasions before diabetes onset had no prognostic value. The development of a mild form of IDDM may be expected in cases with pre-existing IGT for more than one year. The insulin secretion is of low predictive value under these conditions. The observation is of practical use and theoretical interest.  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