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   58667篇
  免费   3947篇
  国内免费   205篇
耳鼻咽喉   649篇
儿科学   1168篇
妇产科学   884篇
基础医学   7333篇
口腔科学   806篇
临床医学   5530篇
内科学   13969篇
皮肤病学   570篇
神经病学   5609篇
特种医学   2579篇
外科学   9365篇
综合类   667篇
一般理论   67篇
预防医学   4254篇
眼科学   995篇
药学   3503篇
  1篇
中国医学   52篇
肿瘤学   4818篇
  2023年   296篇
  2022年   637篇
  2021年   1508篇
  2020年   943篇
  2019年   1364篇
  2018年   1744篇
  2017年   1181篇
  2016年   1271篇
  2015年   1524篇
  2014年   2285篇
  2013年   2700篇
  2012年   4632篇
  2011年   4578篇
  2010年   2540篇
  2009年   2277篇
  2008年   3989篇
  2007年   4140篇
  2006年   3983篇
  2005年   3919篇
  2004年   3522篇
  2003年   3211篇
  2002年   2909篇
  2001年   493篇
  2000年   413篇
  1999年   484篇
  1998年   539篇
  1997年   471篇
  1996年   401篇
  1995年   361篇
  1994年   293篇
  1993年   279篇
  1992年   283篇
  1991年   255篇
  1990年   269篇
  1989年   242篇
  1988年   224篇
  1987年   200篇
  1986年   198篇
  1985年   197篇
  1984年   208篇
  1983年   174篇
  1982年   176篇
  1981年   139篇
  1980年   131篇
  1979年   95篇
  1978年   116篇
  1977年   93篇
  1976年   87篇
  1974年   91篇
  1973年   79篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Background and objective  The purpose of this study is to assess whether Chinese children with high apnea–hypopnea index (AHI) are sleepier by a modified Epworth Sleepiness Scale (ESS). Materials and methods  Records were retrospectively reviewed. We included children who were between 3 and 12 years old, admitted for overnight polysomnogram because of suspected obstructive sleep apnea syndrome (OSAS). A modified ESS was used to assess excessive daytime sleepiness (EDS) of the children. Results  One hundred ninety-two Chinese children were included. Children with high AHI, defined as AHI > 5.0, were sleepier than children with AHI less than or equal to 5. After adjustment by age, gender, and obesity, children with high AHI remained significantly sleepier. Modified ESS was significantly correlated with AHI (rho = 0.124, 95% CI = 0.004–0.281). Modified ESS score of >8 was the best cutoff point with the sensitivity and specificity of 0.29 and 0.91, respectively. The odds ratio of children with modified ESS > 10 having high AHI was 4.231 (95%CI = 1.248 to 14.338) and children with modified ESS > 8 had the highest odds ratio, 4.295(95%CI = 1.66 to 11.1), of having high AHI. Conclusion   Chinese children with high AHI appear to be sleepier than children with low AHI. Children with suspected OSAS and high modified ESS, i.e., ESS > 8, had significantly higher odds ratio of having high AHI. Increased sleepiness is a specific but not a sensitive symptom in snoring children with high AHI. Screening for EDS in snoring children may help us identify those with high AHI and prioritize the management of those children. All authors worked and the study was carried out in Kwong Wah Hospital in Hong Kong. There was no conflict of interest and no specific source of funding for the study.  相似文献   
32.
Ganoderma sinensis has been used widely in Oriental countries for the prevention and treatment of various diseases including cancer. Previous studies have shown that the lipid extract from Ganoderma exhibits direct cytotoxicity against tumor cells. Here, it is reported that the lipid extract from germinating G. sinensis spores, at lower concentrations that have no direct tumoricidal activity, induce potent antitumor immune responses in human monocytes/macrophages. Upon stimulation with the lipid extract, monocytes/macrophages exhibited markedly increased production of proinflammatory cytokines and surface expression of costimulatory molecules. Conditioned medium from stimulated cells effectively suppressed the growth of tumor cells. Apparently, the lipid extract triggered macrophage activation via a mechanism different from that associated with LPS. Moreover, it was observed that the lipid extract could partially re‐establish the antitumor activity of the immunosuppressive tumor‐associated macrophages. These results indicated that in addition to its direct tumoricidal activity, the lipid extract from G. sinensis spores could exert antitumor activity by stimulating the activation of human monocytes/macrophages. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   
33.
34.
A serotonin (5-HT)-mediated phosphoinositide hydrolysis response was characterized in fibroblasts cultured from rabbit choroid plexus. 5-HT elicited a maximum 8-fold increase in [3H]inositol-phosphate ([3H]IP) formation, while the partial agonists, (+)-lysergic acid diethylamide and (−)-1-(4-bromo-2,5-dimethyoxyphenyl)-2-aminopropane caused 2- and 5-fold increases, respectively. Mianserin, ketanserin, and spiperone were equipotent at blocking the 5-HT-mediated response. Thus, agonist and antagonist profiles indicate interactions with 5-HT2 receptors.  相似文献   
35.
Biting and scratching behaviors produced by intrathecal injection of excitatory amino acid (EAA) agonists were examined to determine whether the biting and scratching behavioral effects produced by these compounds are altered selectively in vivo by coadministration with divalent cations. N-methyl-D-aspartate (NMDA)-induced behavior was inhibited by both magnesium and calcium but not by zinc. Kainic acid (KA)-induced behavioral activity was also inhibited by coadministration with calcium but not by magnesium or zinc. In contrast to both NMDA and KA, calcium, magnesium and zinc failed to alter the intensity of quisqualic acid (Quis)-induced biting and scratching behaviors. Based on this selective inhibition of the three EAA subtypes by divalent cations, we examined the behavioral responses produced by Glu and Asp in combination with calcium or magnesium to identify the receptor population involved in these motor effects. Calcium antagonized the biting and scratching behavior produced by i.t. injected Glu in contrast with Asp which was inhibited significantly by magnesium. Our results support the concept that Glu and Asp produce biting and scratching behaviors by an interaction with distinct receptor populations in the spinal cord. To date, there are no selective antagonists at the KA or Quis receptors. Thus, a systematic examination of the selective inhibition of EAA activity by divalent cations in addition to currently available pharmacologic antagonists may prove to be a useful approach to the identification of NMDA, KA and Quis receptor interactions.  相似文献   
36.
A 53-year-old woman was examined at our medical center because of progressive dysphagia of 14 days' duration and a severe inability to open her mouth and swallow saliva. A barium esophagogram showed no obstruction, but pooling of barium in the hypopharynx suggested a neuromuscular disorder. The clinical diagnosis of tetanus was confirmed by electromyography. With appropriate therapy, the patient recovered during a period of 6 weeks. This case illustrates both an uncommon cause of dysphagia and an uncommon initial manifestation of tetanus.  相似文献   
37.
(18)F-FDG PET has a high accuracy in staging head and neck cancer, but its role in patients with clinically and radiographically negative necks (N0) is less clear. In particular, the value of combined PET/CT has not been determined in this group of patients. METHODS: In a prospective study, 31 patients with oral cancer and no evidence of lymph node metastases by clinical examination or CT/MRI underwent (18)F-FDG PET/CT before elective neck dissection. PET/CT findings were recorded by neck side (left or right) and lymph node level. PET/CT findings were compared with histopathology of dissected nodes, which was the standard of reference. RESULTS: Elective neck dissections (26 unilateral, 5 bilateral; a total of 36 neck sides), involving 142 nodal levels, were performed. Only 13 of 765 dissected lymph nodes harbored metastases. Histopathology revealed nodal metastases in 9 of 36 neck sides and 9 of 142 nodal levels. PET was TP in 6 nodal levels (6 neck sides), false-negative in 3 levels (3 neck sides), true-negative in 127 levels (23 neck sides), and false-positive in 6 levels (4 neck sides). The 3 false-negative findings occurred in metastases smaller than 3 mm or because of inability to distinguish between primary tumor and adjacent metastasis. TP and false-positive nodes exhibited similar standardized uptakes (4.8 +/- 1.1 vs. 4.2 +/- 1.0; P = not significant). Sensitivity and specificity were 67% and 85% on the basis of neck sides and 67% and 95% on the basis of number of nodal levels, respectively. If a decision regarding the need for neck dissection had been based solely on PET/CT, 3 false-negative necks would have been undertreated, and 4 false-positive necks would have been overtreated. CONCLUSION: (18)F-FDG PET/CT can identify lymph node metastases in a segment of patients with oral cancer and N0 neck. A negative test can exclude metastatic deposits with high specificity. Despite reasonably high overall accuracy, however, the clinical application of PET/CT in the N0 neck may be limited by the combination of limited sensitivity for small metastatic deposits and a relatively high number of false-positive findings. The surgical management of the N0 neck should therefore not be based on PET/CT findings alone.  相似文献   
38.

Background  

Although training and education have long been accepted as integral to disaster preparedness, many currently taught practices are neither evidence-based nor standardized. The need for effective evidence-based disaster training of healthcare staff at all levels, including the development of standards and guidelines for training in the multi-disciplinary health response to major events, has been designated by the disaster response community as a high priority. We describe the application of systematic evidence-based consensus building methods to derive educational competencies and objectives in criteria-based preparedness and response relevant to all hospital healthcare workers.  相似文献   
39.
Despite evidence from previous unit recording, microstimulation, lesioning and anatomical studies, the functions of the midbrain periaqueductal gray (PAG) remain unclear. We attempted to clarify the function of the PAG by recording activity of PAG units along with laryngeal and respiratory electromyograms (EMG) during vocalization in awake monkeys. PAG units were classified with respect to vocalization on the basis of their discharge patterns as 'early burst', 'late burst', 'tonic-increase' and 'tonic-off', with the vast majority being of the early- and late-burst type. Early-burst cells were correlated most frequently with inspiratory muscles of the respiratory system and laryngeal abductor muscles. Late-burst cells were most clearly correlated with laryngeal adductor and expiratory respiratory muscles. Data from spike-triggered averaging and parametric correlations indicate that most cells are related to single muscles, but a significant number were related to functionally related groups of two or more muscles. The results suggest that the PAG determines qualitative aspects of vocalization by the multisynaptic action its cells have on laryngeal and respiratory motoneurons.  相似文献   
40.
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