首页 | 官方网站   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   2515篇
  免费   148篇
  国内免费   12篇
医药卫生   2675篇
  2023年   24篇
  2022年   13篇
  2021年   54篇
  2020年   29篇
  2019年   60篇
  2018年   55篇
  2017年   54篇
  2016年   50篇
  2015年   61篇
  2014年   62篇
  2013年   106篇
  2012年   166篇
  2011年   184篇
  2010年   102篇
  2009年   77篇
  2008年   130篇
  2007年   169篇
  2006年   158篇
  2005年   142篇
  2004年   121篇
  2003年   105篇
  2002年   108篇
  2001年   55篇
  2000年   68篇
  1999年   67篇
  1998年   22篇
  1997年   20篇
  1996年   19篇
  1995年   21篇
  1994年   21篇
  1993年   21篇
  1992年   38篇
  1991年   35篇
  1990年   23篇
  1989年   35篇
  1988年   16篇
  1987年   19篇
  1986年   16篇
  1985年   18篇
  1984年   8篇
  1983年   8篇
  1982年   10篇
  1981年   7篇
  1980年   7篇
  1979年   12篇
  1978年   11篇
  1977年   7篇
  1976年   6篇
  1974年   9篇
  1972年   12篇
排序方式: 共有2675条查询结果,搜索用时 31 毫秒
1.
2.
We have measured systolic and diastolic blood pressure and excretions of sodium, potassium, calcium and magnesium in groups of about 50 8- and 9-year-old boys from 19 European centres using standardized methods for the measurement of blood pressure and collection of urine, and by carrying out all analyses in one laboratory. Weight, height, pulse rate and environmental temperature were also studied. Mean systolic blood pressure ranged from 91 to 105 mm Hg and diastolic blood pressure from 51 to 66 mm Hg. Mean 24-h excretion of sodium was between 91 and 146 mmol/d, that of potassium between 29 and 60 mmol/d, that of calcium between 1.5 and 2.6 mmol/d and that of magnesium between 2.7 and 4.2 mmol/d. Mean sodium excretion tended to be lower and potassium excretion tended to be higher in the boys from the north-western parts of Europe. Relations between either systolic or diastolic blood pressure and electrolyte excretions were generally weak or absent. Most remarkable is that only the association between mean diastolic blood pressure and 24-h magnesium excretion (partial regression coefficient (b +/- s.e., -5.04 +/- 2.08 mm Hg/mmol/d) was statistically significant after adjusting for differences in creatinine excretion and environmental temperature. Mean systolic blood pressure was not significantly related with any of the variables measured. The partial regression coefficient (b +/- s.e.) for diastolic blood pressure on weight was 0.186 +/- 0.062 mm Hg/kg, on height 0.165 +/- 0.056 mm Hg/cm, on pulse rate 0.364 +/- 0.100 mm Hg/beats per min and on outside temperature -0.25 +/- 0.07 mm Hg/degrees C.  相似文献   
3.
BACKGROUND: Season of birth (SOB) has been regarded as a risk factor for atopy. The aim of this study was to explore the relationship between season of birth (SOB) and later development of atopic disease in children and adolescents. METHODS: A total of 1,007 randomly selected subjects, 7 to 17 years of age, who were living in urban Copenhagen, Denmark were studied. All participants were interviewed about respiratory symptoms and possible risk factors for atopic disease. Skin test reactivity, serum total immunoglobulin E (IgE), and airway responsiveness were measured using standard techniques. RESULTS: The overall risk of atopy, as judged by skin test reactivity and serum total IgE, was the same regardless of SOB. On the contrary, asthma was more common in subjects born in the autumn compared with subjects born during the remaining part of the year (12.4% vs. 5.6%), OR = 2.40, 95% CI (1.56-3.94), p < 0.001. This was observed both for atopic asthma OR = 2.41, 95% CI (1.25-4.64), p = 0.007, non-atopic asthma, OR = 2.35, 95% CI (1.14-4.83), p = 0.02, and house dust mite (HDM) sensitive airway hyperresponsiveness, OR = 3.00, 95% CI (1.44-6.24), p = 0.002. Rhinitis and pollen allergy were not significantly related to SOB. CONCLUSIONS: Atopy itself is independent of season of birth, whereas asthma is more prevalent among subjects born during the autumn. Regarding asthma, these results suggest that the first months of life enclose a period of particular vulnerability towards environmental risk factors, especially exposure to aeroallergens like HDM.  相似文献   
4.
Antioxidant defence during cardiopulmonary bypass surgery.   总被引:1,自引:0,他引:1  
OBJECTIVE: Cardiac surgery may lead to severe oxidative stress due to formation of oxidation products generated during ischemia and reperfusion. We investigated to which extent oxidative stress influences a number of endogenous antioxidants and markers of cellular activation. METHODS: At six time points blood was withdrawn from patients undergoing coronary artery bypass grafting, using the on-pump procedure. RESULTS: Both glutathione peroxidase and superoxide dismutase show a gradual and strong increase in activity during surgery (40 and 30%, respectively), returning to baseline values 24 h after surgery. The total antioxidant capacity has a maximum increase of 60%. Markers of cellular activation, such as eosinophil cationic protein and tryptase also increase during the procedure. CONCLUSION: Cardiac surgery results in systemic inflammation accompanied or caused by severe oxidative stress. The human body has a strong innate oxidative defence screen, which is probably not sufficient to fully compensate for the total amount of oxidative damage.  相似文献   
5.
A bstract Background : Ventricular-to-pulmonary artery conduits in growing patients with congenital heart disease will require replacement from time to time due to somatic growth, neointimal hyperplasia, and pulmonary artery stenosis. The purpose of this article is to review our experience with ascending aortic extension for significant long-segment pulmonary artery stenosis in patients undergoing reoperation for right ventricular-to-pulmonary artery conduit replacement. Methods : From 1989 to 1997, 8 patients had aortic transection, right pulmonary artery augmentation arterioplasty, and aortic interposition graft (Hemashield in 7 and Gore-tex in 1) in association with right ventricular-to-pulmonary artery conduit replacement in 7 patients and completion Fontan operation in 1 patient. Aortic cross-clamp time was 90 ± 34 minutes, and the cardiopulmonary bypass time was 205 ± 37 minutes. Results : All patients survived. In those 7 patients who had conduit replacement, the RV/LV ratio declined from 0.78 ± 0.15 to 0.45 ±; 0.05 postoperatively (P < 0.05). Average length of stay was 8.9 ± 7.2 days. Follow-up range is 18 months to 8 years (mean 4 years). Two complications included cardiac transplantation for pre-existing poor left ventricular function and accelerated conduit stenosis leading to conduit re-replacement. Conclusion : Ascending aortic extension facilitates long-segment pulmonary artery augmentation arterioplasty and enlarges the retroaortic space, preventing future compression restenosis.  相似文献   
6.
Due to decreased functional capacity as well as high environmental demands there is a risk of diminishing activity outside home in very old age (age 80+). In order to explore differences according to functional limitations (FL) among very old people with respect to frequency of activity, perceived health, overall perception of neighbourhood environment, and perceived problems in the pedestrian environment, data derived from a postal questionnaire survey to very old people living in an urban area in Sweden were used. This explorative study is based on the sub-sample of people aged 80+ who reported outdoor activities (n = 97). Four groups of respondents with different types of FL were identified: with no FL (n = 23), with only movement-related FL (n = 26), with only perception/cognition-related FL (n = 16), and with both movement- and perception/ cognition-related FL (n = 32). The majority of the respondents reported rather high frequency of activity outside home. When examining differences between the four groups, the analysis indicated how the complexity of FL and perceived problems in the pedestrian environment impacted on their activity performance. Persons with both movement- and perception/cognition-related FL were less satisfied with their frequency of activity, experienced their health more negatively and experienced more problems in the pedestrian environment than in the other groups. The findings from this study indicate the importance of considering combinations of FL in creating supportive environments for activity and health.  相似文献   
7.
To study the relationship between development of lung function and bronchial responsiveness, we examined 106 subjects recruited from a random sample of 527 subjects, aged 8-18 years, from Copenhagen. Lung function and bronchial responsiveness to inhaled histamine were measured at two occasions, in 1986 and 1988. The participating subjects (n = 106) were divided into three groups: (a) 20 asthmatics with bronchial hyperresponsiveness (BHR), (b) 42 nonasthmatic subjects with BHR in 1986, and (c) 44 controls without BHR. In 1986, FEV1 expressed as percentage of predicted value, was found to be similar in the three groups (91%, 94%, and 99%, respectively). The increase in height during the observation period was found to be 5, 6, and 6 cm, respectively, in the three groups. However, at the second examination, in 1988, FEV1 was found to be significantly reduced in both asthmatics (87%) and nonasthmatic subjects (85%) compared with the controls (103%). In 1988, 16 asthmatics (80%) and 24 (57%) nonasthmatic subjects were found to have BHR, whereas none of the controls were found to have BHR. A multiple regression analysis was used to determine the correlation between change in FEV1 and potential factors of importance. The change in FEV1 was highly correlated with the presence of BHR in 1986, however, no correlation was found between change in FEV1 and change in bronchial responsiveness. In conclusion, nonasthmatic subjects with former BHR showed signs of airflow obstruction and less increase in lung function during growth irrespective of the change in level of bronchial responsiveness, which may suggest a risk for subsequent development of obstructive lung disease.  相似文献   
8.
9.
BACKGROUND: Regular seafood consumption is recommended in dietary guidelines. The aim of this study was to investigate the importance of seafood as a nutrient source in adolescents' diet and the extent to which seafood consumption can increase the intake of omega-3 polyunsaturated fatty acids and vitamin D. METHODS: Consumption data recorded during seven consecutive days for 341 adolescents selected in Ghent (Belgium) were used to estimate the intake of vitamin D, linoleic (LA), alpha-linolenic (LNA), arachidonic (AA), eicosapentaenoic (EPA), docosapentaenoic (DPA) and docosahexaenoic (DHA) acid. RESULTS: The adolescents consumed on average 3.21 microg/day vitamin D, 11.7 g/day LA and 1.4 g/day LNA. The mean intakes of AA, EPA, DPA and DHA were 83.2, 55.9, 18.4 and 111.4 mg/day respectively. The major source of vitamin D was fortified margarine. Fats and oils were the main sources for LA and LNA. The intake of AA was mainly contributed by meat, poultry and eggs. Fish and seafood contributed for 84.1%, 59.3% and 64.4% respectively for EPA, DPA and DHA. CONCLUSION: Flemish adolescents would benefit from increased seafood consumption, as this would lead to a higher intake of EPA and DHA as well as of vitamin D. Moreover, replacement of foods rich in saturated fat (SFA) by seafood products can help to reduce SFA intake.  相似文献   
10.
BACKGROUND: Mediastinal germ cell tumors presenting during childhood are extremely rare. Publications on this entity are very scarce. This paper reports on the clinical presentations, method(s) of treatment, complications, results and outcomes in a series of children with mediastinal germ cell tumors. METHODS: A retrospective chart review of 7 children treated between 1971 and 2001 for mediastinal germ cell tumor was carried out. Age at diagnosis and symptoms were recorded. Each patient's surgical treatment, peri- and postoperative complications, histological staging and final outcome were analysed. RESULTS: The median age of the 4 boys and 3 girls was 3 years (range 21 months-15 years). The most frequent symptoms were respiratory distress, persistent coughing, thoracic pain and anorexia/weight loss. Four patients had histologically benign tumors (mature teratoma). Their sole treatment consisted of complete surgical excision of the tumor and (part of) the thymus using either median sternotomy or left-sided thoracotomy. Recovery was uneventful. No recurrences have been observed. All four are alive with no evidence of disease, between 2.5 and 29 years after treatment. Malignant tumors were observed in three patients (1 yolk sac tumor, 1 choriocarcinoma and 1 malignant teratoma). Treatment consisted of either biopsy or debulking followed by chemotherapy (and radiotherapy in 1 case). Two of them died from uncontrollable metastatic disease. The patient with yolk sac tumor survived; he is now in remission, 4 years after diagnosis. CONCLUSIONS: Both this study and the literature review testify to the extreme rarity of mediastinal germ cell tumors in childhood. Children with this type of tumor usually are severely symptomatic. Histologically benign tumors carry an excellent prognosis provided surgical excision is complete. Histologically malignant tumors, on the other hand, have a worse prognosis. However, the use of platinum-based combination chemotherapy has considerably increased the survival rates.  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-23

京公网安备 11010802026262号