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   1107569篇
  免费   77585篇
  国内免费   2029篇
耳鼻咽喉   15218篇
儿科学   29089篇
妇产科学   26605篇
基础医学   155798篇
口腔科学   31977篇
临床医学   98311篇
内科学   220438篇
皮肤病学   22076篇
神经病学   89717篇
特种医学   42935篇
外国民族医学   92篇
外科学   177741篇
综合类   20266篇
现状与发展   4篇
一般理论   433篇
预防医学   75160篇
眼科学   26009篇
药学   83828篇
  3篇
中国医学   2380篇
肿瘤学   69103篇
  2021年   8378篇
  2019年   8713篇
  2018年   12258篇
  2017年   9465篇
  2016年   10568篇
  2015年   12189篇
  2014年   16888篇
  2013年   25186篇
  2012年   35031篇
  2011年   36847篇
  2010年   21407篇
  2009年   20344篇
  2008年   35645篇
  2007年   37515篇
  2006年   37847篇
  2005年   37042篇
  2004年   35649篇
  2003年   34175篇
  2002年   33330篇
  2001年   56342篇
  2000年   57896篇
  1999年   48686篇
  1998年   13022篇
  1997年   11439篇
  1996年   11282篇
  1995年   10488篇
  1994年   9676篇
  1993年   8930篇
  1992年   36710篇
  1991年   35049篇
  1990年   33759篇
  1989年   32828篇
  1988年   29974篇
  1987年   29134篇
  1986年   27270篇
  1985年   26166篇
  1984年   19160篇
  1983年   16388篇
  1982年   9428篇
  1981年   8247篇
  1979年   16631篇
  1978年   11522篇
  1977年   9881篇
  1976年   8600篇
  1975年   9229篇
  1974年   11087篇
  1973年   10378篇
  1972年   9772篇
  1971年   9172篇
  1970年   8696篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
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   
22.
23.
Summary: A female patient with isovaleric acidaemia had a successful outcome from pregnancy.  相似文献   
24.
25.
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   
26.
27.
Levels of the soluble form of the triggering receptor expressed on myeloid cells (sTREM)-1 are elevated in severe sepsis. However, it is not known whether sTREM-1 measurements can distinguish milder bacterial infections from noninfectious inflammation. The present authors studied whether serum sTREM-1 levels differ in community-acquired pneumonia, exacerbations of chronic obstructive pulmonary disease (COPD), asthma and controls, and whether sTREM-1 may be used as a surrogate marker for the need for antibiotics. Serum sTREM-1 levels in 150 patients with pneumonia, COPD and asthma exacerbations and 62 healthy controls were measured. Serum sTREM-1 levels were significantly elevated in pneumonia (median 295.2 ng x mL(-1)), COPD (280.3 ng x mL(-1)) and asthma exacerbations (184.0 ng x mL(-1)) compared with controls (83.1 ng x mL(-1)). Levels were higher in pneumonia and Anthonisen type 1 COPD exacerbations than in type 2 and 3 COPD and asthma exacerbations. The area under the receiver operating characteristics curve for sTREM-1 as a surrogate marker for the need for antibiotics was 0.77. Serum levels of the soluble form of the triggering receptor expressed on myeloid cells-1 were elevated predominantly in pneumonia and Anthonisen type 1 COPD exacerbations versus type 2 and 3 chronic obstructive pulmonary disease exacerbations, asthma and controls. Serum levels of the soluble form of the triggering receptor expressed on myeloid cells-1 has moderate but insufficient accuracy as a surrogate marker for the need for antibiotics in lower respiratory tract infections.  相似文献   
28.
29.
BACKGROUND: Psychotic symptoms in Alzheimer disease (AD+P) identify a heritable phenotype associated with more rapid cognitive decline. The authors have proposed that AD+P is itself a composite of a misidentification and a paranoid subtype with increased cognitive impairment restricted to the misidentification type. Most prior studies of the clinical correlates of AD+P have been limited, however, by the inclusion of prevalent cases. METHODS: Subjects with possible or probable AD or mild cognitive impairment (MCI) without psychosis at study entry were assessed at the time of initial presentation and then annually. Psychotic symptoms were assessed using the CERAD Behavioral Rating Scale. Survival analyses used Cox proportional hazard models with time-dependent covariates to examine the predictors of psychosis onset. RESULTS: A total of 288 subjects completed at least one follow-up examination. Mean duration of follow-up was 22.1 months. The incidence of psychosis was 0.19 per person-year. Cognitive impairment was associated with onset of psychosis, largely as a result of its association with onset of the misidentification, but not the paranoid, subtype. Including psychotropic medication use in the model revealed an association of antidepressant use with the onset of psychosis. This latter association appeared to arise from an underlying association between depression and the risk of psychosis onset rather than from antidepressant treatment. CONCLUSION: These findings are consistent with the hypothesis that the misidentification and the paranoid subtypes each define a more biologically homogeneous group than AD+P as a whole. Further exploration of the relationship between depressive symptoms and psychosis in patients with AD is warranted.  相似文献   
30.
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