首页 | 官方网站   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   12701篇
  免费   737篇
  国内免费   20篇
医药卫生   13458篇
  2022年   85篇
  2021年   186篇
  2020年   102篇
  2019年   153篇
  2018年   196篇
  2017年   152篇
  2016年   155篇
  2015年   193篇
  2014年   253篇
  2013年   325篇
  2012年   561篇
  2011年   611篇
  2010年   363篇
  2009年   330篇
  2008年   514篇
  2007年   519篇
  2006年   545篇
  2005年   622篇
  2004年   489篇
  2003年   470篇
  2002年   489篇
  2001年   425篇
  2000年   470篇
  1999年   372篇
  1998年   178篇
  1997年   148篇
  1996年   155篇
  1995年   119篇
  1994年   127篇
  1993年   111篇
  1992年   289篇
  1991年   261篇
  1990年   252篇
  1989年   280篇
  1988年   247篇
  1987年   246篇
  1986年   215篇
  1985年   224篇
  1984年   188篇
  1983年   157篇
  1982年   105篇
  1981年   103篇
  1979年   153篇
  1978年   110篇
  1977年   73篇
  1976年   79篇
  1975年   74篇
  1974年   105篇
  1973年   95篇
  1972年   71篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Vitiligo and psoriasis are both common skin disorders. However, psoriasis strictly confined to pre-existing vitiligo areas is rare and suggests a causal relationship. We report here on two patients with a strict anatomical colocalization of vitiligo and psoriasis. The histopathological examinations showed typical changes for both diseases together with a dense infiltrate of CD4+ and CD8+ T cells. By immunohistochemistry, intracytoplasmatic granzyme B and tumour necrosis factor alpha (TNF-alpha) were detected within the T-cell population, suggesting the functional activity of these cells and the creation of a local T helper 1 (Th1)-cytokine milieu. Additionally, in one patient we could identify anti-melanocytic T cells by tetramer staining and enzyme-linked immunospot (ELISPOT) analysis. These skin-infiltrating lymphocytes might trigger, by the local production of Th-1 cytokines such as TNF-alpha and interferon-gamma (IFN-gamma), the eruption of psoriatic plaques in patients with a genetic predisposition for psoriasis.  相似文献   
3.
4.
Many hospitals today have implemented widely disparate information systems on mainframe and mini-computer hardware. The advent of network technology in hospitals has made it possible to access information in these systems. Unfortunately, the user interfaces to applications on these systems are unique and difficult to learn, which makes them unsuitable for use by clinical services. In this paper we describe the development of a Physician's Workstation which integrates information from multiple existing information systems and discuss how the workstation makes it possible to move from the departmental systems of the present to the computer-based medical record system of the future.  相似文献   
5.
6.
This study describes the influence of isocalorically fed diets (containing different amounts of fat) on tumor incidence and parameters of fat metabolism in female Sprague-Dawley rats. Comparisons are made between rats induced with methylnitrosourea (25 mg/kg body wt) and untreated controls (Group I). The animals received either control diets (3.9% fat by weight, Groups I and II) or fat-enriched diets (10.7%, Group III; 15.6%, Group IV; 21.4%, Group V) over a period of 180 days. At the termination of the experiment, intake of the diet containing 10.7% fat by weight (24% fat per total calories) was associated with the highest tumor incidence. Comparing the different diets, liver lipid concentrations in the individual groups increased with increasing dietary fat, whereas the total lipid in plasma decreased. During the feeding period, total lipid of the liver and plasma, and plasma cholesterol, increased in all groups, but triglycerides of plasma decreased. However, when plasma cholesterol and triglycerides were calculated as a relative amount of total lipid in plasma, cholesterol was found to be significantly decreased in Groups III and IV, and triglycerides were increased in Group III but decreased significantly in Groups I, II, and V at the end of the experiment.  相似文献   
7.
The reconstruction of a part of the body that has lost or inhibited function has been the most important aspect of reconstructive surgery in the past. Because of the existence of better techniques and the patient's wish for social reintegration, the plastic surgeon today is forced to consider the aesthetic results of his work more than in the past. Sometimes microsurgical procedures in reconstructive surgery are the only chance for the patient to be healed or palliated. Experience with more than 350 free tissue transfers gave us the opportunity to estimate the value of a donor flap with respect to the requirements of the receiving site. To satisfy the high aesthetic demands in these cases, it was necessary for the right place and shape the flap to fit as closely as possible, even if further corrections were necessary to achieve a satisfactory result. The transfer of latissimus dorsi and radial forearm flaps to the face and lower leg is discussed in cases of tumorus diseases and severe injuries of young and old patients.Presented to the IXth Congress of the International Society of Aesthetic Plastic Surgery, New York, October 13, 1987  相似文献   
8.
Development of the central nervous system (CNS) involves the transformation of a two-dimensional epithelial sheet of uniform ectodermal cells, the neuroectoderm, into a highly complex three-dimensional structure consisting of a huge variety of different neural cell types. Characteristic numbers of each cell type become arranged in reproducible spatial patterns, which is a prerequisite for the establishment of specific functional contacts. The fruitfly Drosophila is a suitable model to approach the mechanisms controlling the generation of cell diversity and pattern in the developing CNS, as it allows linking of gene function to individually identifiable cells. This review addresses aspects of the formation and specification of neural stem cells (neuroblasts) in Drosophila in the light of recent studies on their segmental diversification.  相似文献   
9.
Cerebellar involvement in motor and non-motor sequence learning was examined with serial reaction time tasks (SRT). Our sample consisted of 8 children and adolescents who had undergone surgical removal of a benign posterior fossa tumor (PFT) during childhood. None of them had undergone chemotherapy or cranial radiation therapy (CRT). Ages ranged from 1-11 years at surgery and 9-17 years at testing. The children were tested not earlier than 2.5 years after surgery (M = 5.9 years), enabling brain plasticity and recovery of functions. Their performance was compared with a matched control sample. The PFT group was not impaired in the implicit learning of sequences, as reflected in their performance in blocks with a repeated sequence, both before and after a random block. However, in the perceptual task, their performance deteriorated more than that of the control group when a random block was introduced, suggesting that it was more difficult for the patients to respond flexibly or change their response set when encountering changing task demands. These results are in line with another study by our group on task switching with the same patients.  相似文献   
10.
OBJECTIVES: To assess prospectively the early time course of Transforming Growth Factor beta-1 (TGFbeta-1), basic Fibroblast Growth Factor (bFGF) and Tumor Necrosis Factor alpha (TNFalpha) as possible contributors to restenosis development after angioplasty. DESIGN: Prospective Study. METHODS: The levels of the soluble forms of these factors in the early response to Percutaneous Transluminal Angioplasty (PTA) in the arteries of the lower limb were prospectively assessed. 32 patients with peripheral arterial occlusive disease (PAOD), presenting with intermittent claudication (Fontaine stage IIb) were scheduled for angioplasty treatment. Serum levels of TGFbeta-1, TNFalpha and bFGF were assessed before intervention, 15 and 60 minutes after, 24 hours after as well as 2 and 4 weeks after intervention. We compared the distribution patterns between patients treated with balloon angioplasty and patients who required secondary stent implantation. Endpoint was the development of restenosis within 6 months after interventional treatment, defined as a lumen diameter reduction of more than 50% by ultrasound measurement compared to the result after PTA. RESULTS: The patients who later developed restenosis had significantly higher levels of TGFbeta-1 at 15 minutes, 24 hours and 2 weeks after PTA (p<0.05). TNFalpha and bFGF were only detected in a few patients and no significant change of serum levels was observed. CONCLUSION: The results demonstrate a possible role of TGFbeta-1 in the formation of restenosis after PTA.  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-23

京公网安备 11010802026262号