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   2611篇
  免费   132篇
  国内免费   4篇
耳鼻咽喉   22篇
儿科学   149篇
妇产科学   115篇
基础医学   316篇
口腔科学   99篇
临床医学   300篇
内科学   482篇
皮肤病学   35篇
神经病学   236篇
特种医学   37篇
外科学   215篇
综合类   8篇
预防医学   289篇
眼科学   49篇
药学   210篇
中国医学   3篇
肿瘤学   182篇
  2023年   11篇
  2022年   13篇
  2021年   30篇
  2020年   26篇
  2019年   46篇
  2018年   49篇
  2017年   33篇
  2016年   55篇
  2015年   67篇
  2014年   82篇
  2013年   131篇
  2012年   171篇
  2011年   169篇
  2010年   109篇
  2009年   101篇
  2008年   166篇
  2007年   198篇
  2006年   181篇
  2005年   169篇
  2004年   142篇
  2003年   157篇
  2002年   129篇
  2001年   23篇
  2000年   25篇
  1999年   34篇
  1998年   30篇
  1997年   30篇
  1996年   35篇
  1995年   27篇
  1994年   25篇
  1993年   25篇
  1992年   17篇
  1991年   23篇
  1990年   15篇
  1989年   18篇
  1988年   14篇
  1987年   13篇
  1986年   12篇
  1985年   9篇
  1984年   9篇
  1983年   11篇
  1982年   10篇
  1981年   16篇
  1980年   11篇
  1979年   11篇
  1978年   9篇
  1975年   7篇
  1974年   6篇
  1972年   6篇
  1967年   6篇
排序方式: 共有2747条查询结果,搜索用时 171 毫秒
81.
BackgroundA better understanding of the environmental factors leading to inflammatory bowel disease should help to prevent occurrence of the disease and its relapses.AimTo review current knowledge on dietary risk factors for inflammatory bowel disease.MethodsThe PubMed, Medline and Cochrane Library were searched for studies on diet and risk of inflammatory bowel disease.ResultsEstablished non-diet risk factors include family predisposition, smoking, appendectomy, and antibiotics. Retrospective case–control studies are encumbered with methodological problems. Prospective studies on European cohorts, mainly including middle-aged adults, suggest that a diet high in protein from meat and fish is associated with a higher risk of inflammatory bowel disease. Intake of the n-6 polyunsaturated fatty acid linoleic acid may confer risk of ulcerative colitis, whereas n-3 polyunsaturated fatty acids may be protective. No effect was found of intake of dietary fibres, sugar, macronutrients, total energy, vitamin C, D, E, Carotene, or Retinol (vitamin A) on risk of ulcerative colitis. No prospective data was found on risk related to intake of fruits, vegetables or food microparticles (titanium dioxide and aluminium silicate).ConclusionsA diet high in protein, particular animal protein, may be associated with increased risk of inflammatory bowel disease and relapses. N-6 polyunsaturated fatty acids may predispose to ulcerative colitis whilst n-3 polyunsaturated fatty acid may protect. These results should be confirmed in other countries and in younger subjects before dietary counselling is recommended in high risk subjects.  相似文献   
82.
During the period 1964–73, 286 patients were treated for mandibular fractures. 229 patients (80%) attended the follow-up examination. The length of observation was from 1 to 9 years. The treatment and the follow-up evaluations in the 229 patients are described. Early fracture treatment has been the objective, also in patients who have undergone severe cerebral traumas. Antibiotic prophylaxis was implemented in cases of compound fractures. Preservation of teeth and tooth buds in the line of fracture was attempted. Clinical infection occurred in 0.4% of the patients. At the follow-up examination 1 patient presented with a fracture displacement outside the condylar process. Neither malocclusion nor pseudarthrosis following fracture or after treatment were seen. Permanent sensory disturbances in the innervation area of the mental nerve following fracture occurred in 8%. Radiological examination of the teeth in the line of fracture revealed unnoticed apical bone lesions in 17% of 118 patients. In a further 23% there was a negative response to the vitality test. Follow-up control of mandibular fractures is advised at 12 to 18 months after treatment.  相似文献   
83.
Previous results point towards a lateralization of dorsolateral prefrontal cortex (DLPFC) function in risky decision making. While the right hemisphere seems involved in inhibitory cognitive control of affective impulses, the left DLPFC is crucial in the deliberative processing of information relevant for the decision. However, a lack of empirical evidence precludes definitive conclusions. The aim of our study was to determine whether anodal transcranial direct current stimulation (tDCS) over the right DLPFC with cathodal tDCS over the lDLPFC (anodal right/cathodal left) or vice versa (anodal left/cathodal right) differentially modulates risk‐taking in a task [the Columbia Card Task (CCT)] specifically engaging affect‐charged (Hot CCT) vs. deliberative (Cold CCT) decision making. The facilitating effect of the anodal stimulation on neuronal activity was emphasized by the use of a small anode and a big cathode. To investigate the role of individual differences in risk‐taking, participants were either smokers or non‐smokers. Anodal left/cathodal right stimulation decreased risk‐taking in the ‘cold’ cognition version of the task, in both groups, probably by modulating deliberative processing. In the ‘hot’ version, anodal right/cathodal left stimulation led to opposite effects in smokers and non‐smokers, which might be explained by the engagement of the same inhibitory control mechanism: in smokers, improved controllability of risk‐seeking impulsivity led to more conservative decisions, while inhibition of risk‐aversion in non‐smokers resulted in riskier choices. These results provide evidence for a hemispheric asymmetry and personality‐dependent tDCS effects in risky decision making, and may be important for clinical research on addiction and depression.  相似文献   
84.
85.
Rett syndrome (RTT) is a neurodevelopmental disorder, including autonomic nervous system dysfunctions and severe communication impairment with an extremely limited ability to use verbal language. These individuals are therefore dependent on the capacity of caregivers to observe and interpret communicative signals, including emotional expressions. People in general, including therapists tend to focus on changes in facial expressions to interpret a person's emotional state or choices, but with this population it is difficult to know if the interpretations are correct. The aims of this study were to investigate if the Facial Action Coding System (FACS) could be used to identify facial expressions, and differentiate between those that expressed emotions and those that were elicited by abnormal brainstem activation in RTT. The sample comprised 29 participants with RTT and 11 children with a normal developmental pattern, exposed to six different musical stimuli during non-invasive registration of autonomic brainstem functions. The results indicate that FACS makes it possible both to identify facial expressions and to differentiate between those that stem from emotions and those caused by abnormal brainstem activation. This knowledge may be a great help to an uninitiated observer, who otherwise might incorrectly interpret the latter as an expression of emotion.  相似文献   
86.

Objective

The aim of this study was to evaluate the clinical retention of a one-step self-etching adhesive system (Xeno III) in Class V non-carious cervical lesions and the effect of restorative material and curing techniques on longevity of the restorations.

Materials and methods

A total of 139 Class V restorations were placed with the self-etching primer Xeno III and a resin composite (Tetric Ceram) or a poly-acid modified resin composite (Dyract AP) in non-carious cervical lesions without intentional enamel involvement. The materials were cured with a conventional continuous light, a soft-start or a pulse-delay curing mode. The restorations were evaluated at baseline, 6, 12, 18 and 24 months and then yearly during a 7 year follow-up with modified USPHS criteria. Dentine bonding efficiency was determined by the percentage of lost restorations.

Results

During the 7 years, 135 restorations could be evaluated. No post-operative sensitivity was reported by the participants. Overall relative cumulative loss rate frequencies for the adhesive system at 6 and 18 months and 7 years, independent of curing technique and restorative material, were 0.8%, 6.9% and 23.0%, respectively. The self-etching adhesive fulfilled at 18 months the full acceptance ADA criteria. Tetric Ceram showed at 7 years a 20.9% loss of retention and Dyract AP a 25.0% loss rate (Log rank p = 0.48). The loss rates for the 3 curing techniques: continuous, soft start and pulse delay were 17%, 27.9% and 24.4%, respectively (Log rank p = 0.52). No secondary caries was observed.

Significance

The single-step self-etching adhesive showed acceptable clinical long-time retention rates to dentine surfaces independent of restorative material and curing technique used.  相似文献   
87.
Journal of Neurology - Determining the cause of acute ischemic stroke is crucial for patient management, particularly for preventing future stroke. In recent years, carotid web (CW), a...  相似文献   
88.
89.

Introduction and hypothesis

We evaluated the effect of adding pelvic floor muscle training (PFMT) to a structured lifestyle advice program.

Methods

This was a single-blinded randomized trial of women with symptomatic pelvic organ prolapse (POP) stage?≥?II. Participants were randomized to a structured lifestyle advice program with or without PFMT. Both groups received similar lifestyle advice in six separate group sessions. The combined group performed group PFMT after an individual assessment. Primary outcome was a global improvement scale at six-month follow-up. Secondary outcomes were the global scale and objective POP at three-month follow-up, symptoms and quality of life including sexuality, at three and six-month follow-up. A clinically relevant change of symptoms was defined as ≥15 %.

Results

We included 109 women. Eighty-nine women (82 %) completed three months follow-up; 85 (78 %) completed six-month follow-up. At both follow-ups, significantly more women in the combined group reported improvement in the global scale. At the three-month follow-up, the combined group only had significant improvement of POP symptoms while only the lifestyle advice group had significant improvement of quality of life. Change in objective POP and sexuality was nonsignificant. The symptom score improved 17 % in the combined group and 14 % in the lifestyle advice group (P?=?0.57). Significantly more women in the lifestyle advice group had sought further treatment at the six-month follow-up.

Conclusion

Adding PFMT to a structured lifestyle advice program gave superior results in a global scale and for POP symptoms. Overall effect of either intervention barely reached clinical relevance.
  相似文献   
90.
Exclusive breastfeeding is recommended during the first 6 months of life; thereafter, continued breastfeeding along with nutritious complementary foods is recommended. Continued breastfeeding contributes a substantial proportion of nutrient needs and promotes healthy growth and development, but the quantity of breast milk consumed may be highly variable and little is known about the factors associated with breast milk intake after 6 months of age. The present study was conducted to assess factors associated with breast milk intake of Malawian infants at 9–10 months of age. Breast milk intake was measured using the dose‐to‐mother deuterium oxide dilution method in a subsample of 358 Malawian infants who were participating in a randomized controlled trial of lipid‐based nutrient supplements. Regression analysis was used to assess associations between breast milk intake and several maternal and infant variables. Mean (standard deviation) breast milk intake was 752 (244) g day–1. In multiple regression, breast milk intake was positively associated with infant weight (+62 g per kg body weight, P < 0.01) and maternal height (P < 0.01) and negatively associated with maternal education and age (P < 0.01). There was a non‐significant (P = 0.063) inverse association between energy from non‐breast milk sources and breast milk intake. In this rural Malawian population, infant weight is the main predictor of breast milk intake, even after the first 6 months of life.  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