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   2089篇
  免费   103篇
  国内免费   16篇
耳鼻咽喉   87篇
儿科学   23篇
妇产科学   11篇
基础医学   257篇
口腔科学   78篇
临床医学   123篇
内科学   618篇
皮肤病学   18篇
神经病学   330篇
特种医学   37篇
外科学   293篇
综合类   6篇
预防医学   103篇
眼科学   8篇
药学   135篇
中国医学   5篇
肿瘤学   76篇
  2023年   10篇
  2022年   13篇
  2021年   36篇
  2020年   15篇
  2019年   33篇
  2018年   53篇
  2017年   37篇
  2016年   29篇
  2015年   31篇
  2014年   44篇
  2013年   85篇
  2012年   142篇
  2011年   129篇
  2010年   81篇
  2009年   74篇
  2008年   118篇
  2007年   108篇
  2006年   117篇
  2005年   106篇
  2004年   92篇
  2003年   96篇
  2002年   83篇
  2001年   85篇
  2000年   82篇
  1999年   80篇
  1998年   15篇
  1997年   14篇
  1996年   16篇
  1995年   16篇
  1994年   11篇
  1993年   10篇
  1992年   32篇
  1991年   33篇
  1990年   23篇
  1989年   25篇
  1988年   32篇
  1987年   27篇
  1986年   21篇
  1985年   22篇
  1984年   14篇
  1983年   19篇
  1980年   5篇
  1979年   13篇
  1978年   8篇
  1977年   6篇
  1975年   8篇
  1974年   10篇
  1970年   8篇
  1969年   8篇
  1968年   7篇
排序方式: 共有2208条查询结果,搜索用时 31 毫秒
21.
Because the hemolysis produced by Listeria monocytogenes and Listeria seeligeri on blood agar is frequently difficult to interpret, we developed a microplate technique for the routine determination of hemolytic activity with erythrocyte suspensions. This microtechnique is a simple and reliable test for distinguishing clearly between hemolytic and nonhemolytic strains and could be used instead of the CAMP (Christie-Atkins-Munch-Petersen) test with Staphylococcus aureus in the routine typing of Listeria strains. Furthermore, our results suggest that the quantitation of the hemolytic activity of the Listeria strains, along with the D-xylose, L-rhamnose, and alpha-methyl-D-mannoside acidification tests, allows the differentiation of L. monocytogenes, L. seeligeri, and Listeria ivanovii. We also observed that the treatment of erythrocytes with crude exosubstances of rhodococcus equi, Pseudomonas fluorescens, Acinetobacter calcoaceticus, and S. aureus enhanced the hemolytic activity of all Listeria strains with this characteristic.  相似文献   
22.
The adult hippocampal neurogenesis is affected by vitamin E deficiency. In the present investigation we examined if neural precursor proliferation, newborn cell survival or both are altered by vitamin E deficiency. 5-Bromo-2'-deoxyuridine (BrdU) was employed as a marker of proliferating cells. BrdU-labelled cells were revealed 1 and 30 days after BrdU administration in order to evaluate proliferation and newborn cell survival, respectively. Cell proliferation decreased in controls from juvenile to adult age, and the decrease was lesser in vitamin E deficiency. Thus we found a higher number of proliferating cells in vitamin E-deficient rats than in age-matched controls at 5 months of age. Comparing the number of BrdU-positive cells between 1 and 30 days after the last BrdU injection revealed a remarkable decrease in all groups; this is the greatest in vitamin E-deficient rats and the lowest in control rats. Consistently cell death in the dentate gyrus, assessed by TUNEL technique, was found to decrease from 1 to 5 months of age, but at 5 months it was significantly higher in vitamin E-deficient rats than in age-matched controls. These data show that vitamin E deficiency enhances neural precursor proliferation and cell death during adult neurogenesis.  相似文献   
23.
Economy of locomotion in high-altitude Tibetan migrants exposed to normoxia   总被引:1,自引:0,他引:1  
High-altitude Tibetans undergo a pattern of adaptations to chronic hypoxia characterized, among others, by a more efficient aerobic performance compared with acclimatized lowlanders. To test whether such changes may persist upon descent to moderate altitude, oxygen uptake of 17 male Tibetan natives lifelong residents at 3500–4500 m was assessed within 1 month upon migration to 1300 m. Exercise protocols were: 5 min treadmill walking at 6 km h−1 on increasing inclines from +5 to +15% and 5 min running at 10 km h−1 on a +5% grade. The data (mean ± s.e.m. ) were compared with those obtained on Nepali lowlanders. When walking on +10, +12.5 and +15% inclines, net     of Tibetans was 25.2 ± 0.7, 29.1 ± 1.1 and 31.3 ± 0.9 ml kg−1 min−1, respectively, i.e. 8, 10 and 13% less ( P < 0.05) than that of Nepali. At the end of the heaviest load, blood lactate concentration was lower in Tibetans than in Nepali (6.0 ± 0.9 versus 8.9 ± 0.6 m m ; P < 0.05) . During running,     of Tibetans was 35.1 ± 0.8 versus 39.3 ± 0.7 ml kg−1 min−1 (i.e. 11% less; P < 0.01). In conclusion, during submaximal walking and running at 1300 m, Tibetans are still characterized by lower aerobic energy expenditure than control subjects that is not accounted for by differences in mechanical power output and/or compensated for by anaerobic glycolysis. These findings indicate that chronic hypoxia induces metabolic adaptations whose underlying mechanisms still need to be elucidated, that persist for at least 1 month upon descent to moderate altitude.  相似文献   
24.
C Urso  L Messerini  W de Meester  G Ferri 《Pathologica》1989,81(1076):611-616
Two rare cases of laryngeal paraganglioma are reported. The first patient was a 14-year-old girl, that had a new laterocervical paraganglioma, 4 years after the excision of a laryngeal tumor. The other patient was a 33-year-old man. In both the cases, the diagnosis was made on histopathological ground and the tumors displayed the typical histological pattern of paragangliomas: epithelioid tumor cell arranged in nests (Zell-ballen) in a vascular stroma. Neoplastic cells were found to contain argyrophil granules and chromogranin. Laryngeal paragangliomas reported in the literature are 73, they generally are supraglottic, show no sex predilection and prefer the V-VII decades of age.  相似文献   
25.
Cryoglobulins   总被引:9,自引:0,他引:9  
Serum cryoglobulins are found in a wide spectrum of disorders but are often transient and without clinical implications. Monoclonal cryoglobulins are usually associated with haematological disorders, whereas mixed cryoglobulins are found in many infectious and systemic disorders. So called essential mixed cryoglobulinaemia shows a striking association with hepatitis C virus (HCV) infection (> 90%). It is a systemic vasculitis (leucocytoclastic vasculitis) with cutaneous and multiple visceral organ involvement. Chronic HCV infection can lead to a constellation of autoimmune and neoplastic disorders. In this review, the aetiology, diagnosis, disease heterogeneity, and treatment of cryoglobulinaemia are discussed.  相似文献   
26.
Several investigators have described the altered sleep patterns in Down's syndrome subjects. The most relevant findings have been a reduction in percentage of REM sleep, a prolonged latency to the first REM episode, an increase in undifferentiated sleep, and a reduced ratio of the oculomotor frequencies. Because it is of interest to identify new drugs able to increase the percentage of REM sleep in mentally retarded subjects, we studied the effects of butoctamide hydrogen succinate (BAHS) on nocturnal sleep in eight young institutionalized Down's syndrome subjects.BAHS produced a significant increase in the percentage of REM sleep as well as a decrease in undifferentiated sleep and latency to the first REM.  相似文献   
27.
28.
This study aimed to estimate the incidence of hospital‐acquired pressure injury (PI) and its risk factors in inpatient and intensive care units of five hospitals (two public and three private) in the city of Sao Paulo, Brazil. A 6‐month follow‐up prospective cohort study (n = 1937) was conducted from April to September 2013. Baseline and follow‐up measurements included demographic and care information, as well as risk assessments for both undernutrition (NRS‐2002) and PI (Braden scale). Poisson regression with robust variance was used for data analysis. A total of 633 patients (32.60%) showed risk for PI. The incidence rate of PI was of 5.9% (9.9% in public hospitals vs 4.1% in private hospitals) and was higher in intensive care units, compared to inpatient care units (10% vs 5.7%, respectively). Risk for PI increased with age (RR = 1.05; 95% CI 1.04‐1.07); was higher in in public hospitals, compared to private hospitals (RR = 4.39; 95% CI 2.92‐6.61); in patients admitted for non‐surgical reasons compared to those admitted for surgical reasons (RR = 1.91; 95% CI 1.12‐3.27); in patients with longer hospital stays (RR = 1.04; 95% CI 1.03‐1.06); high blood pressure (RR = 1.76; 95% CI 1.17‐2.64); or had a risk for undernutrition (RR = 3.51; 95% CI 1.71‐7.24). Higher scores in the Braden scale was associated with a decreased risk of PI (RR = 0.79; 95% CI 0.75‐0.83). The results of our study indicate that 5.9% of all patients developed PI and that the most important factors that nurses should consider are: patient age, care setting, length of hospitalization, comorbidities, reason for admission and nutrition when planning and implementing PI‐preventative actions.  相似文献   
29.
BackgroundSleeve gastrectomy (SG) has become the most prevalent bariatric-metabolic surgical approach in the United States. Its popularity among surgeons and patients is mainly due to a better safety profile and less overall morbidity, with broad benefits from a systemic and metabolic perspective.ObjectiveComprehensively describe the short-term multiorgan metabolic effects of rapid weight loss after SG.SettingAcademic hospital, United States.MethodsWe retrospectively reviewed the charts of patients that underwent SG at our institution between 2012 and 2016. We analyzed the required variables to calculate multiple risk scores, such as cardiovascular, hypertension, and diabetes risk scores. Furthermore, the renal and hepatic functions and the metabolic and hematologic profiles were assessed at 12 months of follow-up.ResultsA total of 1002 patients were included in the analysis. The percentage of excess body mass index loss was, on average, 65% at 12 months of follow-up. We observed a positive cardio-renal-hepatic improvement, demonstrated by a substantial reduction of the 10-year cardiovascular risk. We noticed an improvement of renal function, which was more significant in chronic kidney disease (stage ≥2), and a significant improvement on liver function tests (measured by decreased aspartate aminotransferase and alanine transaminase) at 12 months of follow-up. Our data also show a positive impact on decreasing the risk of developing hypertension and type 2 diabetes. There was a positive impact on the lipid profile, with the exception of low-density lipoprotein.ConclusionThere are significant short-term benefits on multiorgan metabolic parameters after rapid weight loss in severely obese patients undergoing sleeve gastrectomy.  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