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   5378篇
  免费   322篇
  国内免费   16篇
耳鼻咽喉   66篇
儿科学   206篇
妇产科学   243篇
基础医学   621篇
口腔科学   34篇
临床医学   623篇
内科学   986篇
皮肤病学   67篇
神经病学   575篇
特种医学   159篇
外科学   571篇
综合类   46篇
一般理论   12篇
预防医学   702篇
眼科学   85篇
药学   310篇
中国医学   4篇
肿瘤学   406篇
  2024年   6篇
  2023年   50篇
  2022年   80篇
  2021年   164篇
  2020年   89篇
  2019年   175篇
  2018年   177篇
  2017年   124篇
  2016年   116篇
  2015年   139篇
  2014年   190篇
  2013年   303篇
  2012年   427篇
  2011年   424篇
  2010年   220篇
  2009年   199篇
  2008年   363篇
  2007年   340篇
  2006年   356篇
  2005年   333篇
  2004年   292篇
  2003年   237篇
  2002年   235篇
  2001年   49篇
  2000年   38篇
  1999年   40篇
  1998年   51篇
  1997年   50篇
  1996年   38篇
  1995年   37篇
  1994年   40篇
  1993年   29篇
  1992年   26篇
  1991年   36篇
  1990年   15篇
  1989年   22篇
  1988年   17篇
  1987年   22篇
  1986年   10篇
  1985年   15篇
  1984年   16篇
  1983年   14篇
  1982年   14篇
  1981年   8篇
  1980年   9篇
  1979年   10篇
  1978年   9篇
  1977年   6篇
  1975年   9篇
  1972年   6篇
排序方式: 共有5716条查询结果,搜索用时 15 毫秒
11.
12.
13.
The effectiveness of educational activities on changing the handwashing habits of preschool children was evaluated using parental surveys and direct observations. Baseline handwashing behaviors were observed and recorded, and parents completed a pre-intervention survey. After interventions were administered, post-intervention data was collected on preschoolers' handwashing habits. Children participated in one, three or five handwashing intervention activities. Results of this study indicate that the educational activities implemented resulted in increased knowledge of the importance of proper handwashing and in positive changes in the children's handwashing habits, particularly for the children who participated in all five interventions.  相似文献   
14.
The agreement between neuropsychologists identifying cognitive impairment (CI) in older adults was examined, as were factors influencing the classification process. Twenty four neuropsychologists in 18 study centers classified cases with or without CI after reviewing neuropsychological findings and other relevant information. All cases were participants in the third wave of the Canadian Study of Health and Aging, a study of CI in later life. For 117 randomly selected cases, a second neuropsychologist reviewed the same material and reclassified the cases. Cases given the same (concordant) or different (discordant) classifications were compared with respect to patient and rater characteristics. The inter-rater agreement was moderate (77.7% agreement, kappa = .49). On all measures of cognitive functioning, the concordant group without impairment obtained a higher mean score than the discordant group, and the discordant group obtained a higher mean score than the concordant group with impairment. For 5 out of 8 cognitive measures, the concordant group with impairment differed from the concordant group without impairment and the discordant group, but the latter two groups did not differ significantly. The findings are comparable to others in the field and highlight the need for neuropsychologists to further clarify procedures for identifying subtle, or mild, forms of cognitive impairment.  相似文献   
15.
BACKGROUND: Hemodialysis (HD) patients typically have reduced muscle mass and diminished functional capacity. The role of the muscle insulin-like growth factors (IGFs), a principal anabolic system that is involved in protein synthesis and that has downregulation that is implicated in muscle loss in animal models of uremia, has previously not been assessed in vivo in HD patients. METHODS: Seventeen HD patients were compared cross-sectionally with 17 age-, sex-, and body mass index-matched healthy controls. Body composition was assessed by dual energy x-ray absorptiometry and bioelectrical impedance spectrometry; functional capacity by hand grip strength, quadriceps strength, and 30-second sit-to-stand test; systemic inflammation by tumor necrosis factor-alpha (TNF-alpha) and TNF receptor 1 (TNFR1); serum and muscle IGF-I and IGFBP-3 by radioimmunoassay; and fragmentation of serum IGFBP-3 by Western immunoblotting. RESULTS: Appendicular lean mass was significantly decreased in HD patients compared with controls (17.6 +/- 0.9 versus 21.5 +/- 1.5 kg, P < .05), as were all measures of functional capacity (P < .01 to .001), and highly significant positive correlations between appendicular lean mass and functional capacity were evident (appendicular lean mass and hand-grip strength, quadriceps strength, 30-second sit-to-stand test, all P < .001). TNF-alpha and TNFR1 were elevated in patients (P < .001). Although serum IGF-I and IGFBP-3 levels did not differ between the groups (P = .295 and .379 respectively), fragmented IGFBP-3 levels were increased (53.1 +/- 16.0 versus 29.81 +/- 15.3%, P < .005). In contrast, muscle IGF-I was substantially diminished in the patient group (n = 7) relative to control (n = 5) levels (0.84 +/- 0.06 versus 2.78 +/- 1.80 pg/microg, P < .05). CONCLUSIONS: We provide evidence of reduced IGF-I in HD patients' skeletal muscle that may be a causal factor in the muscle wasting characteristic of this population. Future research should determine the exact consequences and causes of alterations to the muscle IGF system in HD patients.  相似文献   
16.
Context Previous research on ethical issues encountered by medical professionals in training and practice have presented the thematic content of the cases they encounter rather than the activities in which clinicians engage and in which they most often encounter ethical issues. We conducted a direct observation study of paediatrics residents and their preceptors seeing patients in an out‐patient general paediatrics clinic. Our objectives were to describe the everyday ethics‐related issues paediatrics residents encounter as they interact with patients. Our ultimate goal is to use this knowledge to enhance current efforts to teach ethics to paediatrics residents. Methods The study team directly observed paediatrics residents discussing patients with their faculty preceptors (19 half‐day sessions, 76 hours) in an out‐patient general paediatrics clinic located in an urban academic medical centre. Each interaction between resident and preceptor about a single patient was considered a case for further analysis. Results A total of 247 cases were recorded. Forty‐one of the cases were coded as having ethics‐related content. A constant comparative method of qualitative data analysis revealed that residents were most likely to encounter ethical issues when engaged in the following activities: (i) maintaining a therapeutic alliance with the caregiver (e.g. the parent); (ii) prioritising patient or family needs; (iii) adjusting to the power embodied by the role of doctors, and (iv) distinguishing suboptimal care from abuse or neglect. In addition, our findings indicate that it is through their efforts to maintain the therapeutic alliance with the caregivers of their patients that residents engage in and integrate three processes: developing their medical knowledge; adhering to professional norms, and balancing the power inherent in the doctor’s role with their responsibility to serve the patient’s interests. Conclusions Medical faculty tasked with teaching ethics to paediatrics residents can utilise the results of this project to better target and enhance their ethics education efforts directed at residents in the out‐patient setting. Future research could further examine and test these findings in other clinical settings (e.g. adult general medicine).  相似文献   
17.
Lipopolysaccharide (LPS) preconditioning provides neuroprotection against subsequent cerebral ischemic injury. Tumor necrosis factor-alpha (TNFalpha) is protective in LPS-induced preconditioning yet exacerbates neuronal injury in ischemia. Here, we define dual roles of TNFalpha in LPS-induced ischemic tolerance in a murine model of stroke and in primary neuronal cultures in vitro, and show that the cytotoxic effects of TNFalpha are attenuated by LPS preconditioning. We show that LPS preconditioning significantly increases circulating levels of TNFalpha before middle cerebral artery occlusion in mice and show that TNFalpha is required to establish subsequent neuroprotection against ischemia, as mice lacking TNFalpha are not protected from ischemic injury by LPS preconditioning. After stroke, LPS preconditioned mice have a significant reduction in the levels of TNFalpha (approximately threefold) and the proximal TNFalpha signaling molecules, neuronal TNF-receptor 1 (TNFR1), and TNFR-associated death domain (TRADD). Soluble TNFR1 (s-TNFR1) levels were significantly increased after stroke in LPS-preconditioned mice (approximately 2.5-fold), which may neutralize the effect of TNFalpha and reduce TNFalpha-mediated injury in ischemia. Importantly, LPS-preconditioned mice show marked resistance to brain injury caused by intracerebral administration of exogenous TNFalpha after stroke. We establish an in vitro model of LPS preconditioning in primary cortical neuronal cultures and show that LPS preconditioning causes significant protection against injurious TNFalpha in the setting of ischemia. Our studies suggest that TNFalpha is a twin-edged sword in the setting of stroke: TNFalpha upregulation is needed to establish LPS-induced tolerance before ischemia, whereas suppression of TNFalpha signaling during ischemia confers neuroprotection after LPS preconditioning.  相似文献   
18.
The production of phonological features of African American English (AAE) was examined for 64 typically developing African American children in the 2nd through the 5th grade. Students read aloud passages written in Standard American English. Sixty of the students read the passages using AAE, and 8 different phonological features were represented in their readings. Phonological features were more frequent than morphosyntactic features. The findings as a whole support use of the taxonomy developed for this investigation in characterizing the phonological features of child AAE.  相似文献   
19.
Background Associations between allergen challenge-induced sites of epithelial damage and the distribution of leucocytes and extravasated plasma remain unexplored. Objective To study neutrophils, eosinophils, and fibrinogen at allergen challenge-induced patchy epithelial damage-restitution sites in guinea-pig trachea. Methods After local challenge tracheal tissue (cryo sections and whole-mounts) and lumen (selective tracheal lavage) were examined at 1, 5, and 24 h. Eosinophils, neutrophils and fibrinogen were identified by histochemistry. Results Neutrophils increased markedly in tracheal lavage fluids and in tissue and were strongly associated with the challenge-induced epithelial craters of damage-restitution. At 1 and 24 h eosinophils were increased in the tracheal lumen whereas the surrounding tissue displayed a reversed pattern. Gels rich in fibrinogen, neutrophils, and eosinophils were present in epithelial crater areas, protruding into the lumen. Clusters of free eosinophil granules, Cfegs, released through lysis of eosinophils, and neutrophils with long cytoplasmatic protrusions abounded in these crater areas. Conclusions The present findings provide important new insights into allergic airways where sites of epithelial damage-restitution processes emerge as the major loci for eosinophil, neutrophil, and plasma protein activities, the latter likely causing leukocyte adhesion and activation in vivo. The disttibution of eosinophils in this study suggests roles of these cells both in airway mucosa and in regional lymph nodes. Based on the present study we also propose that lysis of eosinophils and Cfegs generation are a major paradigm for activation of these cells in vivo.  相似文献   
20.
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