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   45201篇
  免费   2336篇
  国内免费   165篇
耳鼻咽喉   667篇
儿科学   2799篇
妇产科学   819篇
基础医学   5233篇
口腔科学   1292篇
临床医学   3214篇
内科学   8280篇
皮肤病学   1194篇
神经病学   2672篇
特种医学   1383篇
外科学   7195篇
综合类   1338篇
现状与发展   1篇
一般理论   22篇
预防医学   2184篇
眼科学   1551篇
药学   4322篇
  2篇
中国医学   359篇
肿瘤学   3175篇
  2023年   350篇
  2022年   1015篇
  2021年   1754篇
  2020年   938篇
  2019年   1075篇
  2018年   1503篇
  2017年   1109篇
  2016年   1436篇
  2015年   1491篇
  2014年   2185篇
  2013年   2496篇
  2012年   3549篇
  2011年   3529篇
  2010年   2094篇
  2009年   1697篇
  2008年   2407篇
  2007年   2454篇
  2006年   2239篇
  2005年   2038篇
  2004年   1889篇
  2003年   1623篇
  2002年   1412篇
  2001年   825篇
  2000年   744篇
  1999年   622篇
  1998年   304篇
  1997年   250篇
  1996年   244篇
  1995年   208篇
  1994年   184篇
  1993年   155篇
  1992年   366篇
  1991年   362篇
  1990年   374篇
  1989年   345篇
  1988年   293篇
  1987年   246篇
  1986年   237篇
  1985年   234篇
  1984年   181篇
  1983年   129篇
  1982年   77篇
  1981年   84篇
  1980年   73篇
  1979年   115篇
  1978年   72篇
  1977年   91篇
  1976年   68篇
  1973年   62篇
  1971年   61篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Cholinergic deficits in Alzheimer's disease are accompanied by a number of alterations in other transmitter systems including glutamate, noradrenaline and serotonin, suggesting the involvement also of other neurotransmitter systems in the pathogenesis of the disease. To address the question whether beta-amyloid may contribute to these deficits, brain tissue from transgenic Tg2576 mice with Alzheimer plaque pathology at ages of 5 (still no significant plaque load) and 17 months (moderate to high cortical beta-amyloid plaque load) were examined for a number of cholinergic and non-cholinergic markers. Transgenic mice with no significant plaque load demonstrated reduced hemicholinium-3 (HCh-3) binding to choline uptake sites in anterior brain regions as compared to non-transgenic littermates, while in aged transgenic mice with high number of plaque deposits decreased HCh-3 binding levels were accompanied by increased vesicular acetylcholine transporter binding in selected cortical brain regions. In aged transgenic mice GABA(A), NMDA, AMPA, kainate, and beta-adrenergic as well 5-HT(1A)- and 5-HT(2A)-receptor binding levels were hardly affected, whereas alpha(1)- and alpha(2)-adrenoceptor binding was increased in selected cerebral cortical regions as compared to non-transgenic littermates. The development of changes in both cholinergic and non-cholinergic markers in transgenic Tg2576 mouse brain already before the onset of progressive plaque deposition provides in vivo evidence of a modulatory role of soluble beta-amyloid on cortical neurotransmission and may be referred to the deficits in learning and memory observed in these mice also before significant plaque load.  相似文献   
82.
Twenty-four patients between the ages of 8 and 48 years (median 27.5) with high-risk for relapse hematologic malignancy received a marrow transplant from an HLA and MLC compatible sibling donor after chemotherapy with busulfan, 4 mg/kg/day for 4 days by mouth, cyclophosphamide 60 mg/kg/day i.v. for 2 days, and etoposide 60 mg/kg i.v. over 4 h on the first day of cyclophosphamide treatment (BU/CY/VP). Toxicity consisted of mucositis, skin rash, and nausea and vomiting in all patients, transient fever thought to be due to etoposide administration in 16/24 (67%) patients, and clinical veno-occlusive disease (VOD) of the liver in 4/24 (17%). There were nine deaths from causes other than recurrent disease in the first 100 days after transplant and two deaths after day 100, a total transplant mortality of 11/24 (46%). Three patients relapsed, but 10/24 (40%) remain alive and disease free 26-182 weeks (median 60 weeks) from transplant. These results compare favorably with results in a group of 12 similar risk patients treated with total body irradiation (TBI) containing regimens during an overlapping time period. Six of the TBI patients have had persistent or recurrent disease and only two (17%) are currently alive and disease free. The probability of disease persistence or relapse is 67% in the TBI group and 20% in the BU/CY/VP group (p less than 0.02).  相似文献   
83.
84.
OBJECTIVE: To determine the impact of nutritional status on peritonitis in patients on continuous ambulatory peritoneal dialysis (CAPD) in a developing country. METHODS: 56 patients with end-stage renal disease on CAPD were randomly selected for this study. These patients were assessed for nutritional status and peritonitis episodes. Nutritional parameters were assessed by anthropometry, diet, body mass index (BMI), Nutritional Risk Index (NRI), serum albumin level, and Subjective Global Assessment (SGA). Based on SGA, patients were categorized into either group 1 (malnutrition, n = 31) or group 2 (normal nutritional status, n = 25). Peritonitis was considered the primary outcome and was compared between the two groups. RESULTS: Demographic profiles, Kt/V, creatinine clearance, and mean follow-up of the two groups were similar. Number of peritonitis episodes was significantly higher in patients with malnutrition (25/31) compared to patients with normal nutritional status (4/25) (p = 0.001). Mean peritonitis rate per patient per year was also significantly higher in patients with malnutrition (0.99 +/- 1.07) compared to patients with normal nutritional status (0.18 +/- 0.42) (p = 0.007). On univariate analysis, malnutrition based on SGA (p = 0.009), NRI (p = 0.02), serum albumin level (p = 0.005), and calorie intake (p = 0.006) was a significant predictor of peritonitis. On multivariate Cox regression analysis, only SGA (p = 0.001, odds ratio 0.08, 95% confidence interval 0.02-0.36) was found to be a significant predictor of peritonitis. On general linear model, the observed power of prediction of peritonitis was 0.96 based on SGA. On Kaplan-Meier survival analysis, peritonitis-free survival in patients with normal nutrition (42 months) was significantly higher compared to patients with malnutrition (21 months) based on SGA (log rank p = 0.003). CONCLUSION: We conclude that peritonitis rate is high in patients with malnutrition and that malnutrition indices, especially SGA, can predict the peritonitis rate in CAPD patients.  相似文献   
85.
Reverse coitus, a rarely used sexual position, makes the male urethra more vulnerable to injury from the pubic arch and symphysis pubis of the female partner. Severe pain, bleeding and immediate detumescence were observed in 3 patients. The lesion usually occurred at the fossa navicularis, responded well to conservative management and did not hinder micturition. Potency has been well preserved in all 3 patients.  相似文献   
86.
87.
The activities of the enzymes related to glutathione synthesis, degradation, and functions as well as reactive oxygen scavenging enzymes were analyzed in different brain regions, such as cerebral hemisphere, cerebellum, brainstem, thalamus, and hypothalamus after 1 and 3 mo of streptozotocin-induced diabetes in rats. Parallel studies were also made in age-matched control rats and insulin-treated diabetic rats. The content of glutathione (GSH) and its synthesizing enzyme γ-glutamylcystein synthetase and also superoxide dismutase (SOD) and catalase activities (reactive oxygen scavenging enzymes) were significantly decreased from almost all the brain regions studied. However, glutathione peroxidase (GPx), glutathione reductase (GR), glutathione S-transferase (GST), γ-glutamyl transpeptidase (γ-GTP), and glutamine synthetase (GS) activities were increased in the diabetic rat brain. Insulin treatment to the diabetic rats resulted in partial to full recovery in these enzymes activities. The present results emphasize the potentially serious alterations of brain free radical scavenger system in uncontrolled Type I diabetes.  相似文献   
88.
The prime objective of oral cavity reconstruction is restoration of function, which must be carefully studied while evaluating the success of any reconstructive endeavour. We devised a unique comprehensive test series for the purpose that is suitable for use in routine follow-ups, and capable of providing objective documentation. Functional assessment included evaluation of general health, food intake, oral competence, mastication, speech, swallowing, tongue mobility, and shoulder–neck function. Fifty patients who had had surgery were analyzed and their functional scores compared with those of 10 normal volunteers. The extent of mandibular resection and the magnitude of soft tissue excision significantly affected overall scores of function. Oral competence, as reflected by the water holding test (WHT), was uniformly impaired in the 50 patients, and in dentate individuals, the quality of bolus provided good correlation with all other functional scores. Among reconstructive modalities employed here, the bi-paddled pectoralis major flap produced the best overall scores.  相似文献   
89.
90.
A range of 17 derivatives of flavone-8-acetic acid (FAA) with a 6-methyl substituent have been prepared and their anti-tumour activity evaluated in vitro against a panel of human and murine tumour cell lines and in vivo against MAC 15A. While many of the compounds show activity comparable to FAA in vitro, this essentially disappears in vivo, possibly due to degradation before the compounds can reach the tumour site.  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