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   30191篇
  免费   3411篇
  国内免费   600篇
耳鼻咽喉   366篇
儿科学   4878篇
妇产科学   85篇
基础医学   5856篇
口腔科学   239篇
临床医学   2707篇
内科学   5910篇
皮肤病学   265篇
神经病学   430篇
特种医学   414篇
外国民族医学   1篇
外科学   1807篇
综合类   3816篇
现状与发展   3篇
一般理论   3篇
预防医学   1831篇
眼科学   265篇
药学   2922篇
  46篇
中国医学   1634篇
肿瘤学   724篇
  2024年   105篇
  2023年   693篇
  2022年   687篇
  2021年   1250篇
  2020年   1458篇
  2019年   1441篇
  2018年   1328篇
  2017年   1400篇
  2016年   1403篇
  2015年   1312篇
  2014年   1949篇
  2013年   3268篇
  2012年   1731篇
  2011年   1743篇
  2010年   1351篇
  2009年   1337篇
  2008年   1311篇
  2007年   1465篇
  2006年   1293篇
  2005年   1094篇
  2004年   842篇
  2003年   759篇
  2002年   664篇
  2001年   606篇
  2000年   472篇
  1999年   460篇
  1998年   378篇
  1997年   387篇
  1996年   306篇
  1995年   196篇
  1994年   201篇
  1993年   159篇
  1992年   144篇
  1991年   137篇
  1990年   128篇
  1989年   89篇
  1988年   94篇
  1987年   80篇
  1986年   89篇
  1985年   98篇
  1984年   56篇
  1983年   43篇
  1982年   44篇
  1981年   34篇
  1980年   48篇
  1979年   19篇
  1978年   15篇
  1977年   11篇
  1976年   6篇
  1975年   6篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
Modified ultrafiltration after cardiopulmonary bypass in children has been shown to be associated with an increase in arterial blood pressure. As part of a series of studies to investigate the possible causes of this blood pressure elevation, the hypothesis that if filtration was removing a significant amount of fentanyl, then the increase in blood pressure might be due to pain was proposed. Ten children, aged between 0.5 and 9.3 years (median 3.8 years), weighing 5.9 to 25..5 kg (median 15.7 kg), underwent corrective cardiac surgery (incorporating modified ultrafiltration). A standard anesthetic protocol was followed, with up to 78 μg/kg of fentanyl given prebypass for analgesia. After completion of cardiopulmonary bypass, modified ultrafiltration was commenced at 100 mL/min until a hematocrit of 35% was reached. Samples were taken of arterial blood (prefiltration, 3, 10, and 20 minutes postfiltration), the venous reservoir blood (prefiltration) and the filtrate (5 and 10 minutes into filtration). Hemodynamic data were recorded both prefiltration and postfiltration. The hemodynamic data showed the expected rise in both systemic arterial pressure and cardiac index after ultrafiltration. The plasma fentanyl concentrations did not significantly change after ultrafiltration: 1.59 to 12.39 ng/mL (median 6.27 ng/mL) prefiltration and 2.05 to 15.59 ng/mL (6.29 ng/mL) at 3 minutes, 2.22 to 12.64 ng/mL (6.87 ng/mL) at 10 minutes, and 1.83 to 11.52 ng/mL (5.85 ng/mL) at 20 minutes postfiltration. The concentration of fentanyl in the venous reservoir, 2.06 to 11.64 ng/mL (7.04 ng/mL), was not significantly different from the plasma levels. The level of fentanyl in the filtrate was significantly less than the plasma levels, 0.243 to 1.87 ng/mL (0.894 ng/mL) at 5 minutes and 0.385 to 1.688 ng / mL (0.952 ng / mL) at 10 minutes into filtration; (P < 0.02 by the Wilcoxon signed-rank method). The data show that the plasma fentanyl concentration was not significantly reduced by modified ultrafiltration. The fentanyl levels found prefiltration were maintained postfiltration, and the observed changes in systemic arterial pressure were not due to an acute fall in the plasma concentration of analgesic drug.  相似文献   
92.
Background Allergic rhinitis (AR) and asthma often coexist and may represent two manifestations of the same disease recently named combined AR and asthma syndrome (CARAS). Aim To review the common pathophysiology of combined AR and asthma and to investigate the efficacy of intranasal corticosteroids (INCS). Methods Medline was used to identify articles relevant to mechanisms. A Cochrane systematic review was performed to assess the efficacy of INCS in CARAS. Results There is cross‐talk, evidence of a common inflammatory response in both sites, linked by a systemic component. The efficacy of anti‐inflammatory INCS on asthma outcomes was assessed in a systematic review of 12 randomized controlled trials involving 425 subjects. After INCS there were non‐significant trends for improvement in asthma symptom score (standardized mean difference (SMD) of 0.61; P=0.07), forced expiratory volume in 1 s (SMD of 0.31; P=0.08), and morning peak expiratory flow (weighted mean difference of 36.51; P=0.06). There was no impact on methacholine airways responsiveness (SMD of ?0.20; P=0.4). The review identified two promising new treatment options in united airway disease such as INCS as monotherapy in rhinitis and mild asthma, and a combined intranasal and intrabronchial corticosteroid (IBCS) deposition technique. Conclusion Common mucosal inflammatory responses occur in CARAS. This systematic review shows trends for a benefit of INCS in CARAS, but recognizes that more research is needed. At this stage, the current best practice is to treat asthma conventionally with IBCS with or without β2‐agonist and to add INCS to improve specific rhinitis symptoms.  相似文献   
93.
BACKGROUND : Selectins participate in the initial phase of leucocyte migration from circulation to inflamed tissues and may play a role in inflammatory cellular influx into airways in asthma. In the sheep asthma model, TBC1269, a pan-selectin antagonist, reduced late allergen response by 74%. OBJECTIVE : To determine whether a single dose of TBC1269 inhibits early (EAR) and late (LAR) asthmatic responses, and whether it inhibits sputum leucocyte influx after inhalation allergen challenge in atopic asthmatic subjects treated with bronchodilators only. METHODS : Twenty-one asthmatic subjects (mean+/-SD, age=32.5+/-6.7 years, 8 males, FEV1 percent predicted=84+/-15%) with known late asthmatic response based on a screening inhalation allergen challenge were randomly assigned to receive intravenous treatment with either placebo (n=11) or TBC1269 (n=10, 30 mg/kg) infused over 15 min immediately prior to a second (post-treatment) allergen challenge at least 4 weeks after the screening challenge. After each challenge, EAR and LAR were monitored for 7 h. In addition, sputum was induced 1 day before and 1 day after each allergen challenge. RESULTS : TBC1269 did not attenuate the EAR compared with placebo (largest fall in FEV1 within 1 h of 34.1+/-13.9% vs. 31.8+/-12.2% for TBC1269 and placebo groups respectively, P=0.61) or the LAR (largest fall in FEV1 between 3 and 7 h of 39.3+/-15.3% vs. 32.6+/-13.8%, P=0.24). TBC1269 had only minor effects on allergen-induced sputum eosinophilia. CONCLUSION : We conclude that TBC1269 administered before allergen challenge as a single intravenous dose does not attenuate early or late asthmatic responses to allergen in asthmatic subjects.  相似文献   
94.
BACKGROUND: Mast cell chymase has the potential to be an important mediator of inflammation and remodelling in the asthmatic lung. Previous studies have examined association between promoter polymorphism of the chymase gene (CMA1) and allergic phenotypes but the significance of this polymorphism is unclear. We have examined association of a CMA1 variant in relation to asthma in a large UK Caucasian family cohort. METHODS: A polymorphism of the CMA1 gene promoter (-1903G/A) was genotyped in 341 asthmatic families and in 184 non-asthmatic adults recruited from the UK PCR-RFLP based genotyping. Association with asthma diagnosis, atopy, specific and total IgE, and atopy and asthma severity was examined. RESULTS: Case-control studies did not reveal a significant difference in allele frequency between asthmatics and controls. A significant association was found between CMA1 genotypes and total IgE levels in subjects with self-reported eczema that remained significant after correction for multiple testing (median total serum IgE GG 297 kU/L, GA 144 kU/L, AA 48.4 kU/L, Pc=0.0032). CONCLUSION: These data suggest that CMA1 promoter polymorphism does not contribute to asthma susceptibility or severity but may be involved in regulating IgE levels in patients with eczema.  相似文献   
95.
人胎盘脂多糖辅助治疗支气管哮喘临床疗效观察   总被引:1,自引:0,他引:1  
目的观察人胎盘脂多糖辅助治疗儿童支气管哮喘的临床疗效。方法将我院91例支气管哮喘患儿随机分成2组,治疗组46例,采用综合疗法,发作期应用沙丁胺醇、普米克令舒、氨茶碱治疗,缓解期肌内注射人胎盘脂多糖、气雾吸入倍氯米松;对照组45例,发作期用沙丁胺醇、普米克令舒、氨茶碱治疗,缓解期气雾吸入倍氯米松。结果治疗2周后治疗组、对照组对改善喘息、咳嗽症状比较,差异有显著性意义(P<0.05)。随访1年,治疗组复发率与对照组比较,差异有显著性意义(P<0.05)。结论人胎盘脂多糖辅助治疗支气管哮喘疗效确切,复发率低,值得临床推广应用。  相似文献   
96.
Sixty-four patients with persistent asthma receiving 200 to 800 μ g of fluticasone propionate daily were enrolled in this switchover study. The patients applied a tulobuterol patch 2 mg every 24 hours for 4 weeks followed by inhalation of salmeterol 100 μ g bid for 4 weeks. The mean values for morning and evening peak expiratory flow improved significantly compared with baseline during the 4 weeks of tulobuterol patch treatment. Further improvement was seen on switching to salmeterol treatment, which was significant even in the first week, and continued until the final week of the study. Use of salmeterol alone resulted in a significant increase in the percentage of forced expiratory volume in 1 second %FEV1 from baseline, with 51% of patients feeling that the treatment was effective (vs. 37% on tulobuterol). These data suggest that salmeterol can achieve better control in asthmatic patients after switching from using tulobuterol patches.  相似文献   
97.
BACKGROUND: Endotoxin was proposed to increase the severity of asthma. Endotoxin levels greatly differ according to settings. In domestic environments, airborne concentrations may be dramatically low compared with levels reported in occupational settings. OBJECTIVE: Our first objective was therefore to assess the effect of inhalation of low-level lipopolysaccharide (LPS) on the immediate and late-phase asthmatic bronchial response. Our second objective was to evaluate the effect of exposure to LPS on the local and systemic inflammatory response. METHODS: Nineteen asthmatics sensitized to cat underwent on two separate occasions a bronchial challenge test to cat allergen (cat BCT) preceded randomly by a pre-exposure to either saline or LPS (2 microg). Methacholine challenge test was performed 24 h before exposure to LPS or saline. The Borg scale for dyspnoea and lung function were recorded before and after exposure to LPS or saline, and before and after cat BCT. Induced sputum and blood samples were collected before and after cat BCT, and analysed for cell counts and eosinophil cationic protein (ECP) levels. RESULTS: Inhalation of 2 microg LPS did not induce any changes in forced expiratory volume in 1 s (FEV1), peak expiratory flow (PEF), FEF 25-75 and Borg scale of dyspnoea. It neither modified Fel d 1 PD20 (45.03 ng as compared with 87.03; P=0.42). As well, there was no significant difference in late-phase reaction. Pre-exposure to LPS did not influence eosinophil counts or ECP levels in blood and sputum. CONCLUSION: Our study demonstrated that pre-exposure to LPS at low levels, which may be encountered in domestic environment, had no significant effect on the immediate and late-phase bronchial response to cat allergen. It neither modified local and systemic eosinophilic inflammation.  相似文献   
98.
T cells are known to develop a critical role in the pathogenesis of atopic dermatitis (AD) and bronchial asthma. T cells involved in AD express the skin homing receptor CLA, but no lung homing receptor has been identified in bronchial asthma. We compared different cell markers and the cytokine production in T cells from children with AD or bronchial asthma. We studied the involvement of CLA+ and CLA- T-cell subpopulations in these diseases. We studied 20 children with acute AD lesions, 15 with mild persistent asthma, and 15 non-atopic controls. All patients were sensitized to house dust mite (DP) and evaluated during the acute phase. Total and specific IgE were measured by immunoassay and the expression of different cell markers and the cytokine production was analyzed by flow cytometry in peripheral blood mononuclear cells. Total IgE was significantly higher in AD children and IgE to DP in the asthmatic children. There was a significant increase in CD25+ CD4+ cells in asthmatic children and in HLA-DR+ CD4+ and HLA-DR+ CD8+ cells in AD. In the CD4+ subsets, there was an increase in IL-13, IL-5 and TNF-alpha in AD compared to controls, a decrease in IFN-gamma in asthmatic children compared to controls, and an increase in IL-13, IL5, IL2, TNF-alpha, and IFN-gamma in the AD compared to asthmatic children. Changes in cytokine production were mainly detected in CLA+ cells in AD and in CLA- cells in asthma. Differences exist in total and specific IgE, activation markers, and cytokine patterns between AD children and children with asthma, with the former expressing a Th2 pattern whereas in asthmatic children we only detected a decrease in IFN-gamma. Moreover, the subpopulations (CLA+ vs. CLA-) expressing these changes were different, indicating that the underlying mechanisms in the two diseases are not exactly the same.  相似文献   
99.
BACKGROUND: Allergic rhinitis (AR) precedes and is often associated with bronchial asthma. Indeed, local and systemic inflammations in both conditions are very similar. Cysteinyl-leukotrienes (cys-LTs) are generated during early- and late-phase allergic reactions and induce smooth-muscle contraction, microvascular leakage, and mucous hypersecretion. Cys-LTs are detected in exhaled breath condensate (EBC) of asthmatics and regardless of bronchial symptoms, they are also found in EBC of rhinitic patients. OBJECTIVE: To evaluate cys-LTs in EBC of allergic patients and to assess the activity of nasal fluticasone propionate (FP) on EBC cys-LTs levels. METHODS: Cys-LTs coefficient of variation (CV) was evaluated from different EBC in 5 healthy volunteers. Cys-LTs levels from EBCs in 13 healthy controls and 56 allergic rhinitic (n=31) and rhinitic/asthmatic (n=25) patients were also evaluated at baseline. Subsequently patients were randomized to receive either FP 100 microg/day per nostril or placebo for 2 weeks and then re-evaluated for EBC cys-LTs. RESULTS: The CV was 14.12%. EBC cys-LTs in allergic patients were significantly higher than in healthy subjects (70.9 vs. 20.6 pg/mL (median), P<0.05), while it did not differ between asthmatic/rhinitic and purely rhinitic patients. Treatment significantly reduced cys-LTs (from 93.6 to 19.9 pg/mL, P<0.001). This effect was evident both in asthmatic/rhinitic and in rhinitic patients. CONCLUSION: Treatment of AR with FP significantly reduces the levels of cys-LTs, major noninvasive markers of lower airway inflammation, suggesting that upper and lower airway inflammation is present and should be thus treated as a whole in subjects with AR with and without asthma.  相似文献   
100.
潘丽  黄福文 《广西医学》2004,26(11):1600-1603
目的 采用多普勒超声心动图评价儿童急性肾炎 (AGN)早期左室舒张功能 (LVDF)损害的严重程度及疗效观察。方法 将 76例急性肾炎患儿按病情程度分为轻度、重度两组与 5 4例健康对照组进行对照。应用HP - 10 0 0型超声诊断仪 ,分别于治疗前和治疗后 2周测定二尖瓣舒张早期峰值流速 (EV)、二尖瓣舒张晚期峰值流速 (AV)、EV AV比值、舒张早期充盈分数(EI)、舒张晚期充盈分数 (AI)、EI AI比值、E峰加速时间 (AT)、E峰减速时间 (DT)、DT AT比值、肺静脉收缩期最大前向血流速度(S)、舒张期最大前向血流速度 (D)、D S比值、左房内径 (LA)、主动脉内径 (AO)、LA AO比值等 11项指标。结果 EV AV、EI AI、LA AO、D S是判断LVDF损害的重要指标 ;LVDF损害与病情严重程度有关 ,其中 ,EV、EV AV、EI、EI AI、AT、D S随病情加重而降低 ,AV、AI、DT、DT AT、LA AO随病情加重而增高 ;EI、AI、AT、DT、DT AT是评价其疗效的重要指标 ;治疗后 ,LVDF恢复时间晚于临床症状恢复时间。结论 上述指标可动态检测LVDF ,对指导临床诊治具有重要意义。同时该检测方法操作简便易行、重复性强、无痛苦 ,结果较为精确。  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