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   2340956篇
  免费   175602篇
  国内免费   5846篇
耳鼻咽喉   32237篇
儿科学   79069篇
妇产科学   64216篇
基础医学   338890篇
口腔科学   63598篇
临床医学   217936篇
内科学   455795篇
皮肤病学   48890篇
神经病学   189977篇
特种医学   88734篇
外国民族医学   912篇
外科学   340318篇
综合类   51655篇
现状与发展   2篇
一般理论   800篇
预防医学   190915篇
眼科学   52043篇
药学   173598篇
  7篇
中国医学   5066篇
肿瘤学   127746篇
  2019年   18539篇
  2018年   26096篇
  2017年   19645篇
  2016年   21493篇
  2015年   24543篇
  2014年   33964篇
  2013年   52447篇
  2012年   71952篇
  2011年   76352篇
  2010年   44971篇
  2009年   42104篇
  2008年   71163篇
  2007年   75740篇
  2006年   76043篇
  2005年   73733篇
  2004年   71087篇
  2003年   68343篇
  2002年   66505篇
  2001年   107944篇
  2000年   111698篇
  1999年   94340篇
  1998年   26632篇
  1997年   24057篇
  1996年   24151篇
  1995年   22975篇
  1994年   21690篇
  1993年   20245篇
  1992年   75576篇
  1991年   74055篇
  1990年   71814篇
  1989年   68427篇
  1988年   63296篇
  1987年   62137篇
  1986年   58573篇
  1985年   56023篇
  1984年   42277篇
  1983年   35784篇
  1982年   21164篇
  1981年   19106篇
  1979年   38104篇
  1978年   26900篇
  1977年   22411篇
  1976年   21488篇
  1975年   22635篇
  1974年   27048篇
  1973年   26305篇
  1972年   24239篇
  1971年   22320篇
  1970年   20933篇
  1969年   18985篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
Chronic obstructive pulmonary disease (COPD) is characterised by a local pulmonary inflammatory response to respiratory pollutants and by systemic inflammation. Tumour necrosis factor (TNF)-alpha has been implicated in systemic effects of COPD and operates by binding the p55 (R1) and p75 (R2) TNF-alpha receptors. To investigate the contribution of each TNF-alpha receptor in the pathogenesis of COPD, the present study examined the effects of chronic air or cigarette smoke (CS) exposure in TNF-alpha R1 knockout (KO) mice, TNF-alpha R2 KO mice and wild type (WT) mice. CS was found to significantly increase the protein levels of soluble TNF-alpha R1 (by four-fold) and TNF-alpha R2 (by 10-fold) in the bronchoalveolar lavage of WT mice. After 3 months, CS induced a prominent pulmonary inflammatory cell influx in WT and TNF-alpha R1 KO mice. In TNF-alpha R2 KO mice, CS-induced pulmonary inflammation was clearly attenuated. After 6 months, no emphysema was observed in CS-exposed TNF-alpha R2 KO mice in contrast to WT and TNF-alpha R1 KO mice. CS-exposed WT and TNF-alpha R1 KO mice failed to gain weight, whereas the body mass of TNF-alpha R2 KO mice was not affected. These current findings suggest that both tumour necrosis factor-alpha receptors contribute to the pathogenesis of chronic obstructive pulmonary disease, but tumour necrosis factor-alpha receptor-2 is the most active receptor in the development of inflammation, emphysema and systemic weight loss in this murine model of chronic obstructive pulmonary disease.  相似文献   
52.
53.
54.
OBJECTIVE: To explore the presence and grade of denervation in three mimic muscles in facial nerve palsy. METHODS: The frontalis, orbicularis oculi (OO), and mentalis muscles were explored in 54 patients with Bell's palsy, after 30 days from the beginning of symptoms. Concentric needle electromyography, including fibrillation detection, was performed in the three muscles on the affected side. Compound muscle action potentials (CMAP) were recorded on both sides and a CMAP ratio was calculated from each muscle. The House-Brackman scale was used to assess the initial clinical evaluation and the follow-up until recovery. RESULTS: Fibrillation was recorded in 32 patients on the 30th day after the onset and was present in 100% of mentalis and in 90% of frontalis, but in only 34% of OO, a statistically significant difference. The grade of fibrillation in OO was also statistically lower from those in the other two muscles. The 32 patients were grouped according to the presence (A) or not (B) of fibrillation in OO. In group A, CMAP ratios (affected/normal side) did not differ significantly among the three muscles. However, in group B they were significantly greater in OO and frontalis than in mentalis. In between-group comparison, group B muscles had significantly higher CMAP ratios, lower degree of fibrillation, and better functional recovery. CONCLUSION: In facial palsy, the presence and grade of fibrillation in OO are lower than in frontalis and mentalis muscles and prognosis is more favorable for the non-fibrillating OO group of patients.  相似文献   
55.
OBJECTIVES: To evaluate a novel method for localization of subdural electrodes in presurgical assessment of patients with drug-resistant focal epilepsy. METHODS: We studied eight consecutive patients with posterior epilepsy in whom subdural electrodes were implanted for presurgical evaluation. Electrodes were detected on post-implantation brain CT scans through a semiautomated procedure based on a MATLAB routine. Then, post-implantation CT scans were fused with pre-implantation MRI to localize the electrodes in relation to the underlying cortical structures. The reliability of this procedure was tested by comparing 3D-rendered MR images of the electrodes with electrode position as determined by intraoperative digital photography. RESULTS: In each patient, all electrodes could be correctly localized and visualized in a stereotactic space, thus allowing optimal surgery planning. The agreement between the procedure-generated images and the digital photographs was good according to two independent raters. The mean mismatch between the 3D images and the photographs was 2 mm. CONCLUSIONS: While our findings need confirmation on larger samples including patients with anterior epilepsy, this procedure allowed to localize subdural electrodes and to establish the spatial relationship of each electrode to the underlying brain structure, either normal or damaged, on brain convessity, basal and medial cortex. SIGNIFICANCE: Being simple, rapid, unexpensive, and reliable, this procedure holds promise to be useful to optimize epilepsy surgery planning.  相似文献   
56.
57.
58.
59.
Here we report how the different types of regional muscle involvement, i.e. bulbar, ocular or generalized, in patients with myasthenia gravis (MG) influence the mental aspects of quality of life. Clinical examination according to Osserman was performed in 48 MG patients (45 women, three men; mean age 54, SD 12 years). Each patient was at the time for clinical evaluation asked to fill out the disease-specific Myasthenia Gravis Questionnaire (MGQ) and the Short-Form 36-item questionnaire for health survey (SF-36) as patient-oriented tools. We related the regional domains (generalized domain, bulbar domain and ocular domain) of the MGQ and the clinical findings, respectively, with mental quality of life as assessed by SF-36. Bulbar and generalized involvement results in impairment of mental aspects of quality of life, whereas ocular involvement does not.  相似文献   
60.
Summary Of the 105 great cormorants (Phalacrocorax carbo sinensins) from northern Poland (the Vistula Lagoon and Masurian Lake District), examined in 2000–2001, 67 proved hosts of the nematode Syncuaria squamata (Linstow, 1883). The prevalence, mean intensity, and intensity range amounted to 63.8 %, 36.2 specimens, and 1–120 specimens, respectively. The infection was heavier in the immature birds (84.6 %, 40.9 inds, and 1–120 inds) than in the adults (3.7 %, 1 ind.). The nematodes were dominated by gravid females (n=1846), followed by males (n=157), immature females (n=79), and L4 larvae (n=2). Measurements of the parasite are provided. S. squamata is a new species for the parasite fauna of Poland.  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