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   571篇
  免费   31篇
  国内免费   69篇
耳鼻咽喉   11篇
儿科学   63篇
妇产科学   8篇
基础医学   82篇
口腔科学   10篇
临床医学   80篇
内科学   101篇
皮肤病学   4篇
神经病学   55篇
特种医学   56篇
外科学   54篇
综合类   13篇
预防医学   35篇
眼科学   8篇
药学   57篇
肿瘤学   34篇
  2023年   4篇
  2022年   6篇
  2021年   5篇
  2020年   5篇
  2019年   10篇
  2018年   4篇
  2017年   6篇
  2016年   6篇
  2015年   10篇
  2014年   13篇
  2013年   26篇
  2012年   22篇
  2011年   19篇
  2010年   20篇
  2009年   14篇
  2008年   14篇
  2007年   58篇
  2006年   17篇
  2005年   28篇
  2004年   12篇
  2003年   20篇
  2002年   21篇
  2001年   25篇
  2000年   30篇
  1999年   24篇
  1998年   28篇
  1997年   22篇
  1996年   23篇
  1995年   18篇
  1994年   7篇
  1993年   10篇
  1992年   11篇
  1991年   18篇
  1990年   16篇
  1989年   18篇
  1988年   12篇
  1987年   9篇
  1986年   7篇
  1985年   4篇
  1984年   7篇
  1981年   2篇
  1980年   3篇
  1979年   7篇
  1978年   6篇
  1977年   10篇
  1975年   2篇
  1974年   2篇
  1973年   3篇
  1972年   2篇
  1969年   1篇
排序方式: 共有671条查询结果,搜索用时 15 毫秒
31.
Human and rhesus monkey platelets secrete at least two antiheparin proteins: platelet factor 4 (PF4) and low affinity platelet factor 4 (LA-PF4). Neither of these proteins showed species-related antigenic differences. As determined by radioimmunoassay, the levels of PF4 and LA-PF4 antigen per 10(9) monkey platelets amounted to 10.7 and 20.3 microgram, respectively. One milliliter of monkey plasma prepared from blood collected into an anticoagulant composed of EDTA, prostaglandin E1, and theophylline solution contained 22.4 ng LA-PF4 and 8.0 ng PF4. Concentrations of these two platelet-specific proteins in monkeys closely resembled levels found in human platelets and plasma. Infusion of prostacyclin (PGI2) (100 or 300 ng/kg/min) into monkeys for 15 min resulted in a significant decrease of plasma levels of LA-PF4 antigen and of PF4 by 40%--60% (p < 0.0001). This decrease was related to the inhibitory effect of PGI2 on the secretion of platelets stimulated by a catheter or by venipuncture. Longer infusion of PGI2 did not produce further significant change. The supernate obtained after aggregation of human platelets stimulated by thrombin was injected into monkeys receiving PGI2 infusion. The disappearance of LA-PF4 antigen in monkey plasma followed a biphasic exponential curve with half-lives for the fast and slow components of 8.4 and 63 min. PF4 disappeared faster but followed the same pattern (half-lives for the fast and slow component of 2.1 and 70 min). Analysis of the experimental data suggests that the low levels of secreted platelet proteins in monkey plasma are related to their minimal in vivo release and to their rapid clearance.  相似文献   
32.
Recent biochemical and cell-based studies identified G0/G1 switch gene 2 (G0S2) as an inhibitor of adipose triglyceride lipase (ATGL), a key mediator of intracellular triacylglycerol (TG) mobilization. Here, we show that upon fasting, G0S2 protein expression exhibits an increase in liver and a decrease in adipose tissue. Global knockout of G0S2 in mice enhanced adipose lipolysis and attenuated gain of body weight and adiposity. More strikingly, G0S2 knockout mice displayed a drastic decrease in hepatic TG content and were resistant to high-fat diet (HFD)-induced liver steatosis, both of which were reproduced by liver-specific G0S2 knockdown. Mice with hepatic G0S2 knockdown also showed increased ketogenesis, accelerated gluconeogenesis, and decelerated glycogenolysis. Conversely, overexpression of G0S2 inhibited fatty acid oxidation in mouse primary hepatocytes and caused sustained steatosis in liver accompanied by deficient TG clearance during the fasting-refeeding transition. In response to HFD, there was a profound increase in hepatic G0S2 expression in the fed state. Global and hepatic ablation of G0S2 both led to improved insulin sensitivity in HFD-fed mice. Our findings implicate a physiological role for G0S2 in the control of adaptive energy response to fasting and as a contributor to obesity-associated liver steatosis.  相似文献   
33.
OBJECTIVE: To investigate the influence of the major histocompatibility complex (MHC) class I molecule HLA-B27 on (i) the invasion of Salmonella and Yersinia into human intestinal epithelial cells, (ii) the survival of intracellular Salmonella in these cells, and (iii) the production of certain inflammatory cytokines by the cells after Salmonella infection. METHODS: The human intestinal epithelial cell line Henle-407 was transfected with HLA-B27 DNA. These cells and HLA-B27-negative control cells were infected with Salmonella or Yersinia, and viable intracellular bacteria were determined as colony-forming units. Cytokine production was assayed with ELISA. RESULTS: Salmonella invaded HLA-B27-positive Henle cells in higher numbers than HLA-B27-negative control cells. However, HLA-B27 did not affect the invasion of Yersinia or the survival of the intracellular bacteria in these intestinal epithelial cells. Salmonella infection induced production of interleukin-8 (IL-8), IL-6 and monocyte chemotactic protein 1 (MCP-1) by Henle cells that was not affected by HLA-B27 in a specific way. CONCLUSIONS: These findings suggest that HLA-B27 enhances the invasion of Salmonella into intestinal epithelial cells. The interaction between bacteria and intestinal epithelial cells plays an important role during the early phases of ReA. HLA-B27-linked modulation of Salmonella invasion may lead to an increased load of Salmonella in intestinal tissue and thus increased susceptibility to reactive arthritis.  相似文献   
34.
四种中成药对气血双虚模型小鼠血象及免疫水平的影响   总被引:1,自引:0,他引:1  
目的:为艾滋病抗病毒疗法所致的骨髓不良反应筛选疗效确切的中成药,观察分析参芪颗粒、复方阿胶浆、贞芪扶正颗粒、复方皂矾丸四种中成药对放血和注射环磷酰胺联合复制的气血双虚模型小鼠血象及免疫水平的影响。方法:实验于2005-08/09在河南中医学院药理实验室完成。①参芪颗粒(江西山高制药有限公司生产,批号040702);复方阿胶浆(山东东阿阿胶股份有限公司生产,批号050446);贞芪扶正颗粒(甘肃扶正药业科技股份有限公司生产,批号040803);复方皂矾丸(陕西郝其军制药有限责任公司生产,批号041014);当归补血口服液(郑州市协和制药厂生产,批号041122);环磷酰胺(上海华联制药有限公司生产,批号050101)。②选取清洁级昆明种小鼠150只,随机数字表法分为15组,10只/组:1~3组分别灌服参芪颗粒混悬液3,2,1g/kg;4~6组分别灌服复方阿胶浆30,20,10mL/kg;7~9组分别灌服贞芪扶正颗粒混悬液15,10,5g/kg;10~12组分别灌服复方皂矾丸混悬液2.4,1.6,0.8g/kg;第13组灌服当归补血口服液10g/kg;剩余2组为空白对照组和模型对照组,分别给于同体积生理盐水10g/kg。各组给药1次/d,连续给药10d。③除空白对照组外,其他各组从给药第1天开始建立气血双虚模型。每只鼠尾部放血0.25mL/10g,然后分别于第2,4,6,8天腹腔注射环磷酰胺80,40,40,40mg/kg。空白对照组同时间点仅腹腔注射等体积生理盐水。末次注射环磷酰胺后2h,眼眶取血,一部分用于血象测定,另一部分离心取血清,测定血细胞比容及血清中巨噬细胞集落刺激因子水平;解剖取胸腺和脾脏,检测胸腺皮质厚度、胸腺淋巴细胞数、脾小结大小、脾脏淋巴细胞数病理学指标的变化。结果:150只小鼠全部进入结果分析,放血和注射环磷酰胺并用可成功建立小鼠气血双虚模型。①与模型对照组比较,参芪颗粒3g/kg组、贞芪扶正颗粒10,5g/kg组、复方皂矾丸1.6g/kg组均可升高气血双虚模型小鼠白细胞水平(t=2.18~2.74,P<0.05),贞芪扶正颗粒15g/kg组作用更为显著(t=2.98,P<0.01);参芪颗粒1g/kg组、复方阿胶浆20mL/kg组、贞芪扶正颗粒15,10g/kg组均可升高红细胞水平(t=2.44~2.69,P<0.05),复方阿胶浆30mL/kg组、贞芪扶正颗粒5g/kg组、复方皂矾丸2.4,1.6g/kg组作用更为显著(t=2.91~3.66,P<0.01);当归补血口服液组、复方阿胶浆20mL/kg组、参芪颗粒3,1g/kg组、贞芪扶正颗粒15,10,5g/kg组均可升高血红蛋白水平(t=2.27~2.85,P<0.05),复方阿胶浆30mL/kg组、复方皂矾丸2.4,1.6g/kg组作用更为显著(t=3.07~4.04,P<0.01);当归补血口服液组、参芪颗粒3,2g/kg组均可升高血小板水平(t=2.20~2.41,P<0.05)。②与模型对照组比较,参芪颗粒2g/kg组、贞芪扶正颗粒5g/kg组均可升高气血双虚模型小鼠血细胞比容(t=2.01~2.62,P<0.05),参芪颗粒1g/kg组、复方阿胶浆30,20,10mL/kg组、贞芪扶正颗粒15,10,5g/kg组、复方皂矾丸2.4,1.6,0.8g/kg组作用更为显著(t=3.18~4.36,P<0.01);参芪颗粒2g/kg组、复方阿胶浆30,20,10mL/kg组、贞芪扶正颗粒15,10,5g/kg组、复方皂矾丸2.4,1.6g/kg组均可显著升高巨噬细胞集落刺激因子水平(t=3.60~6.80,P<0.01)。③与模型对照组比较,当归补血口服液组、参芪颗粒3,2,1g/kg组、复方阿胶浆30,20,10mL/kg组、贞芪扶正颗粒15,10,5g/kg组、复方皂矾丸2.4,1.6,0.8g/kg组均可显著增加气血双虚模型小鼠胸腺皮质厚度(t=3.71~9.34,P<0.01),增大脾小结(t=3.36~11.97,P<0.01),增加脾脏淋巴细胞数(t=4.29~10.44,P<0.01);复方阿胶浆30mL/kg组可明显增加小鼠胸腺淋巴细胞数(t=2.45,P<0.05),当归补血口服液组、参芪颗粒3,2,1g/kg组、复方阿胶浆20,10mL/kg组、贞芪扶正颗粒15,10,5g/kg组、复方皂矾丸2.4g/kg组作用更为显著(t=3.22~8.20,P<0.01)。结论:①四种中成药对气血双虚模型小鼠血红蛋白升高作用相近,以复方阿胶浆和贞芪扶正颗粒对白细胞和红细胞水平升高作用为强,以复方阿胶浆和贞芪扶正颗粒对血小板水平升高作用为优。②四种中成药对气血双虚模型小鼠血细胞比容的影响无差异,以贞芪扶正颗粒和复方皂矾丸对巨噬细胞集落刺激因子水平的升高作用为优。③以参芪颗粒、复方阿胶浆、贞芪扶正颗粒对胸腺皮质厚度和淋巴细胞数的促进作用为优,以参芪颗粒、贞芪扶正颗粒、复方皂矾丸对脾小结和脾脏淋巴细胞数的促进作用为优。  相似文献   
35.
Aim:  To study the association between carbohydrate intake and serum lipids in children, and influence of apolipoprotein E phenotype (apoE) on the association.
Subjects/methods:  A total of 644 children from a prospective, randomized atherosclerosis prevention trial (STRIP) participated in this longitudinal study at age 5 (n = 644), 7 (n = 585) and 9 (n = 550) years. ApoE phenotype, fasting triglyceride, total, low-density lipoprotein (LDL) and high-density lipoprotein (HDL) cholesterol concentrations and 4-day food records were analysed.
Results:  An increase in the total carbohydrate intake by 1 E% (percentage of total daily energy intake) associated with a decrease in HDL cholesterol by 0.006 mmol/L (p < 0.001) when adjusted for saturated, monounsaturated and polyunsaturated fatty acid, age, gender, body mass index and STRIP study group. The inverse association between total carbohydrate intake and HDL cholesterol was evident in children with apoE3 (p < 0.001) or apoE4 (p < 0.001), but not in those with apoE2 (p = 0.78). An increase in total carbohydrate intake by 1 E% increased triglycerides by 0.02 mmol/L (p < 0.001) independently of apoE phenotype, while 1 E% increase in sucrose intake increased triglycerides by 0.01 mmol/L (p < 0.001).
Conclusion:  Carbohydrate intake has a relatively small effect on serum lipids in children. Children with the apoE3 or E4 but not with E2 phenotype show reduction in HDL cholesterol with increasing carbohydrate intake indicating that genetic and environmental factors interact with children's lipoprotein metabolism.  相似文献   
36.

Background  

Several malaria risk maps have been developed in recent years, many from the prevalence of infection data collated by the MARA (Mapping Malaria Risk in Africa) project, and using various environmental data sets as predictors. Variable selection is a major obstacle due to analytical problems caused by over-fitting, confounding and non-independence in the data. Testing and comparing every combination of explanatory variables in a Bayesian spatial framework remains unfeasible for most researchers. The aim of this study was to develop a malaria risk map using a systematic and practicable variable selection process for spatial analysis and mapping of historical malaria risk in Botswana.  相似文献   
37.
A case of recurrent, disseminated retinoblastoma is presented. The primary intraocular tumor, a metastatic mass at recurrence, and the tumor cells infiltrating bone marrow were all positive for the anti-GD2 monoclonal antibody (Mab) 3A7. Indirect immunofluorescence using the monoclonal antibody 3A7 was an effective method of detecting residual disease in the marrow. After remission was achieved by conventional therapy, the patient underwent autologous bone marrow transplantation (ABMT). The preparative regimen consisted of VP-16, cisplatinum, high-dose melphalan, and total body irradiation. The autologous marrow inoculum was clean of tumor cells at the detection level of 1:10,000. The transplant course was uneventful, and the patient is well and disease-free 17 months after ABMT. We conclude that high-dose chemotherapy and total body irradiation in an ABMT setting is feasible and a potentially curative approach to disseminated retinoblastoma.  相似文献   
38.
Post-thrombotic symptoms after an isolated calf deep venous thrombosis   总被引:3,自引:0,他引:3  
BACKGROUND: To study the outcome of an isolated calf deep venous thrombosis (DVT). METHODS: This retrospective study with 62 patients was established in Tampere University Hospital in Finland. In all cases a venographically confirmed calf deep venous thrombosis was detected 6-10 years earlier. Complete review of the patient records was conducted, and the initial phlebograms were also reviewed. Symptoms and signs of the post-thrombotic syndrome in both legs were assessed by means of a questionnaire. Frequency of the post-thrombotic symptoms and signs in both legs were studied. Degree of subjective symptoms, need for visits to medical care centres and the current use of compression therapy in patients with previous DVT were observed. In addition, the incidence of objectively verified recurrences was recorded. RESULTS: Pain (26%), edema (39%), and pigmentation (26%) were frequent in legs with DVT. In contralateral legs the reported frequencies were 23%, 26% and 15% (p>0.05), respectively. In legs with DVT the rate of asymptomatic patients was 37%, 46% had visited medical care centers, and 25% were using compression therapy currently. Recurrent DVT was observed in 13%. Etiology of DVT had no impact on frequency of recurrent events. CONCLUSIONS: Leg symptoms and recurrent events are quite common after calf DVT. The current use of compression therapy and visits to medical care centers are frequently reported. By means of a questionnaire study it is difficult to exclude other reasons for leg symptoms, and this should be noted in judging the RESULTS.  相似文献   
39.
Functional characteristics of electrically stimulated quadriceps muscles of patients with multiple sclerosis (MS) were determined to investigate whether adaptations in muscle properties contribute to the higher fatigability of these patients. The estimated maximal isometric force generating capacity of MS patients was only 11.2% (P < 0.05) lower than control subjects. However, the patients were only able to voluntarily exert 75 +/- 22% (n = 12) of their maximal capacity, against 94 +/- 6% (n = 7) for the control subjects. There were no differences in muscle speed, suggesting that muscle fiber distribution was not different in the MS patients due to reduced muscle usage. During a series of repeated contractions, greater decrements occurred in isometric force and in maximal rate of force rise in the MS patients (by 31.3 +/- 10.3% and 50.1 +/- 10.0%, respectively; n = 13) than control subjects (23.8 +/- 6.6% and 39.0 +/- 8.1%, n = 15), suggesting a lower oxidative capacity. The results indicate that increasing the mass of their muscles by training may help to reduce the excessive muscle fatigue of MS patients.  相似文献   
40.
Gangrenous cholecystitis is a serious complication of acute cholecystitis and is associated with increased morbidity and mortality rates. We report a case in which the diagnosis was suggested by ultrasound, but cholecystectomy delayed due to atypical clinical presentation and a false negative radionuclide biliary scan.  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