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   20981篇
  免费   1686篇
  国内免费   475篇
耳鼻咽喉   124篇
儿科学   1761篇
妇产科学   54篇
基础医学   5155篇
口腔科学   24篇
临床医学   1457篇
内科学   4812篇
皮肤病学   67篇
神经病学   46篇
特种医学   404篇
外科学   313篇
综合类   3462篇
现状与发展   3篇
预防医学   1435篇
眼科学   6篇
药学   2358篇
  22篇
中国医学   1497篇
肿瘤学   142篇
  2024年   39篇
  2023年   200篇
  2022年   386篇
  2021年   741篇
  2020年   715篇
  2019年   672篇
  2018年   635篇
  2017年   734篇
  2016年   819篇
  2015年   813篇
  2014年   1272篇
  2013年   2415篇
  2012年   1250篇
  2011年   1301篇
  2010年   967篇
  2009年   954篇
  2008年   952篇
  2007年   1113篇
  2006年   1023篇
  2005年   825篇
  2004年   699篇
  2003年   619篇
  2002年   548篇
  2001年   498篇
  2000年   399篇
  1999年   395篇
  1998年   316篇
  1997年   313篇
  1996年   226篇
  1995年   161篇
  1994年   162篇
  1993年   111篇
  1992年   110篇
  1991年   95篇
  1990年   107篇
  1989年   70篇
  1988年   66篇
  1987年   55篇
  1986年   67篇
  1985年   72篇
  1984年   36篇
  1983年   34篇
  1982年   33篇
  1981年   29篇
  1980年   33篇
  1979年   19篇
  1978年   14篇
  1977年   6篇
  1976年   8篇
  1975年   4篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
目的探讨哮喘患儿血清中肺表面活性蛋白A、D(SP-A,SP-D)、白介素8(IL-8)、免疫球蛋白E(IgE)含量的变化及其分析研究。方法测定30例儿童哮喘急性发作期和缓解期的SP-A、SP-D、IL-8、IgE及同期健康儿童30例。结果急性发作期的SP-A、SP-D水平均显著低于对照组(P<0.01),IL-8、IgE水平均显著高于对照组(P<0.01);缓解期的SP-A、SP-D水平明显高于发作期(P<0.05),IL-8水平明显低于发作期(P<0.05),IgE水平与发作期相比差异无显著性(P>0.05)。结论儿童哮喘的发作虽然是多种病因引起,IL-8、IgE等在其中的病理生理、免疫病理改变有重要作用。证明SP-A、SP-D含量及功能改变与哮喘的发病、发展关系密切。  相似文献   
992.
Involvement of small airways, those of <2 mm in internal diameter, is present in all stages of asthma and contributes substantially to its pathophysiologic expression. Therefore, small airways are a potential target to achieve optimal asthma control. Airway tone, which is increased in asthma, is mainly controlled by the vagus nerve that releases acetylcholine (ACh) and activates muscarinic ACh receptors (mAChRs) post-synaptically on airway smooth muscle (ASM). In small airways, M3 mAChRs are expressed, but there is no vagal innervation. Non-neuronal ACh released from the epithelial cells that may express choline acetyltransferase in response to inflammatory stimuli, as well as from other structural cells in the airways, including fibroblasts and mast cells, can activate mAChRs. By antagonizing M3 mAChR, the contraction of the ASM is prevented and, potentially, local inflammation can be reduced and the progression of remodeling may be averted. In fact, ACh also contributes to inflammation and remodeling of the airways and regulates the growth of ASM. Several experimental studies have demonstrated the potential benefit derived from the use of mAChR antagonists, mainly long-acting mAChR antagonists (LAMAs), on small airways in asthma. However, there are several confounding factors that may cause a wrong estimation of the relationship between LAMAs and small airways in asthma. Further studies are needed to differentiate broncholytic and anti-inflammatory effects of LAMAs and to better understand the interaction between LAMAs and corticosteroids, also in the context of a triple therapy that includes a β2-AR agonist, at different levels of the bronchial tree.  相似文献   
993.
994.
995.
Background:  Health-related quality-of-life (HRQL) has been poorly studied in large samples of asthmatics from the general population. HRQL and its relationship to asthma-severity were assessed among 900 asthmatics enrolled in the European Community Respiratory Health Survey.
Methods:  Among asthmatics, 864 completed the short form-36 (SF-36) questionnaire and 477 also completed the Asthma Quality-of-life Questionnaire (AQLQ). A 4-class asthma-severity scale, combining clinical items, forced expiratory volume in 1 s and the level of treatment and the different asthma-severity components (each of the clinical items and hospitalization) were studied in relation to HRQL.
Results:  Mean SF-36 Physical Component Summary (PCS) and Mental Component Summary (MCS) scores (45.5 and 48.8 respectively) were lower than expected in a general population. The mean total AQLQ score was 5.8. The AQLQ score and to a lesser extent the PCS score were significantly related to the 4-class asthma-severity scale, although the risk of having a lower HRQL score did not vary proportionally across the levels of severity. Asthma-severity had no impact on the MCS score. Asthma attack frequency and hospitalization were associated with both total AQLQ and PCS scores, whereas nocturnal symptoms and lung function were more strongly related to the AQLQ and PCS score respectively.
Conclusion:  In population-based asthmatics, the specific AQLQ questionnaire, and also to a lesser extent the generic SF-36 questionnaire, were sensitive to asthma-severity. Frequencies of asthma attacks, of nocturnal symptoms and hospitalization for asthma have independent impact on HRQL.  相似文献   
996.
997.
 We identified eight patients with bronchiolitis obliterans (BO) in the autopsies of 81 bone marrow transplant (BMT) recipients. Rapidly progressive dyspnoea and cough were the main presenting symptoms in all eight patients, associated with overinflation and/or infiltrative opacity seen on chest X-ray and obstructive disorder revealed by pulmonary function tests. Early lesions were characterized by epithelial loss and an inflammatory infiltrate containing foamy histiocytes with mild luminal narrowing. Partial or total occlusion of the bronchiolar lumina by fibrous connective tissue was the feature of late lesions. Both changes were coexistent in all cases. In one case, small bronchi with cartilage were also affected by the obstructive process, showing bronchitis obliterans. All eight patients showed non-obstructive broncho-bronchiolitis characterized by denuding of respiratory epithelium, mural oedema and an inflammatory infiltrate in addition to BO, and these changes were also seen in 18 patients without BO. The submucosal glands of large bronchi and the trachea showed mucous retention and a mild inflammatory infiltrate in four of the eight patients. Coexistent infectious processes were seen in all cases, cytomegalovirus and Aspergillus being the most frequent organisms. BO probably develops as an immunopathological event related to graft-versus-host disease (GVHD) during the impaired immune status phase of the post-BMT period, possibly initiated by infection. Bronchial gland involvement in chronic GVHD is one of the factors responsible for this abnormal immune status. Received: 14 January 1997 / Accepted: 5 March 1997  相似文献   
998.
支气管哮喘患儿红细胞免疫功能与脂质过氧化关系的探讨   总被引:6,自引:0,他引:6  
目的 :探讨了支气管哮喘患儿红细胞免疫功能的变化及其与脂质过氧化的关系。方法 :应用红细胞酵母花环法测定了 32例支气管哮喘患儿红细胞免疫功能和化学比色法测定血浆丙二醛 (MDA) ,超氧化物歧化酶 (SOD) ,谷胱甘肽过氧化物酶 (GSH -PX)含量 ,并与 35名正常健康儿童作对照。结果 :支气管哮喘患儿RBC-IC花环率和MDA水平明显地升高 (P <0 .0 1 ) ,而RBC -C3bR、SOD、GSH -PX、SOD/MDA低于正常 (P <0 .0 1 ) ,相关分析显示 :RBC -C3b花环与MDA呈显著的负相关 (r=- 0 .4 30 7,P <0 .0 5 ) ,RBC -ICR与MDA呈正相关 (r=0 .6 384 ,P <0 .0 1 )。结论 :支气管哮喘患儿红细胞免疫粘附功能降低 ,与活性氧代谢紊乱密切相关  相似文献   
999.
目的 观察过敏性哮喘患儿外周血嗜酸性粒细胞及淋巴细胞表面趋化因子受体CCR3与CCR5表达的改变。方法 以16例急性发作及25例缓解期过敏性哮喘患儿和20例健康儿童为主要观察对象,用流式细胞术测定外周血粒细胞群及淋巴细胞群中CCR3与CCR5的表达。结果 过敏性哮喘患儿缓解组CCR3~+淋巴细胞亚群百分率[(4.2±1.9)%],尤其是CCR3~+嗜酸性粒细胞百分率[(3.5±1.6)%]较正常组[(3.0±1.3)%,(1.2±0.5)%]明显增高;急性发作组CCR3~+淋巴细胞亚群与嗜酸性粒细胞百分率[(3.5±1.5)%,(2.2±1.0)%]虽也高于正常组,但较缓解组则出现下降。发作组CCR5~+淋巴细胞亚群仅见增高趋势。结论 CCR3~+嗜酸性粒细胞与淋巴细胞亚群异常升高可能为过敏性哮喘患儿免疫系统异常的一个特征性表现;与缓解组比较,发作组CCR3~+嗜酸性粒细胞及淋巴细胞亚群反而降低,可能和该类细胞向炎症部位趋化并参与了过敏性免疫炎症反应有关。  相似文献   
1000.
对哮喘模型大鼠气管的无载荷状态和零应力状态进行分析。与正常组相比,模型大鼠气管软骨剪开的张开角及所对应的残余应变绝对值均较正常组显著增大(P〈0.05),而且随着x/L的增大而呈明显上升趋势。模型大鼠气管肌肉剪开的张开角及所对应的残余应变绝对值无显著变化,且沿气管轴向变化不明显。结果表明哮喘大鼠气管为了适应外在应力环境的变化,肌肉部分不断进行代偿性生长,导致哮喘大鼠气道重建。  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