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   53865篇
  免费   3750篇
  国内免费   133篇
耳鼻咽喉   433篇
儿科学   1977篇
妇产科学   1846篇
基础医学   6497篇
口腔科学   1009篇
临床医学   9084篇
内科学   9940篇
皮肤病学   835篇
神经病学   4754篇
特种医学   1041篇
外国民族医学   33篇
外科学   4702篇
综合类   726篇
一般理论   80篇
预防医学   7389篇
眼科学   637篇
药学   3030篇
  1篇
中国医学   138篇
肿瘤学   3596篇
  2023年   325篇
  2022年   458篇
  2021年   1150篇
  2020年   766篇
  2019年   1169篇
  2018年   1383篇
  2017年   934篇
  2016年   1055篇
  2015年   1190篇
  2014年   1617篇
  2013年   2591篇
  2012年   3698篇
  2011年   3961篇
  2010年   2147篇
  2009年   1966篇
  2008年   3453篇
  2007年   3886篇
  2006年   3719篇
  2005年   3585篇
  2004年   3439篇
  2003年   3271篇
  2002年   3087篇
  2001年   448篇
  2000年   343篇
  1999年   456篇
  1998年   712篇
  1997年   559篇
  1996年   485篇
  1995年   393篇
  1994年   405篇
  1993年   393篇
  1992年   294篇
  1991年   252篇
  1990年   239篇
  1989年   201篇
  1988年   202篇
  1987年   223篇
  1986年   179篇
  1985年   208篇
  1984年   222篇
  1983年   222篇
  1982年   281篇
  1981年   252篇
  1980年   200篇
  1979年   145篇
  1978年   126篇
  1977年   141篇
  1976年   122篇
  1975年   100篇
  1973年   89篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
OBJECTIVE: The purpose of this study was to examine the association between intensive care unit nurse (ICU) staffing and the likelihood of complications for patients undergoing abdominal aortic surgery. DESIGN: The study is a retrospective review of hospital discharge data linked to data on ICU organizational characteristics. SETTING: Research took place in ICUs in non-federal, short-stay hospitals in Maryland. PATIENTS: Study included 2606 patients undergoing abdominal aortic surgery in Maryland between January 1994 and December 1996. Outcome Measures: Outcome measures included cardiac, respiratory, and other complications. RESULTS: Cardiac complications occurred in 13% of patients, respiratory complications occurred in 30%, and other complications occurred in 8% of patients. Multiple logistic regression revealed a statistically significant increased likelihood of respiratory complications (odds ratio [OR], 2.33; 95% confidence interval [CI], 1.50-3.60) in abdominal aortic surgery patients cared for in ICUs with low- versus high-intensity nurse staffing, an increased likelihood of cardiac complications (OR, 1.78; CI, 1.16-2.72) and other complications (OR, 1.74; CI, 1.15-2.63) in ICUs with medium- versus high-intensity nurse staffing, after controlling for patient and organizational characteristics. CONCLUSIONS: Within the range of ICU nurse staffing levels present in Maryland hospitals, decreased nurse staffing was significantly associated with an increased risk of complications in patients undergoing abdominal aortic surgery.  相似文献   
992.
The development of total biliary casts is very unusual, especially in patients who have not undergone liver transplantation. The aetiology of these casts is uncertain but several factors are believed to play a role, including periods of fasting, haemolysis, cholangitis and recent surgery. Resultant bile stasis and/or gallbladder hypocontractility promote sludge and subsequent stone formation. Here we present the case of a previously well 66-year-old woman who developed a total biliary cast several weeks after being involved in a road traffic accident during which she sustained head injuries but no obvious liver insult. This cast was removed at laparotomy but the patient had resultant diffuse biliary tree abnormalities and persistent cholestasis and subsequently required a liver transplant. The possible aetiologies of biliary cast formation and subsequently cholangiopathy necessitating transplantation in this patient are described.  相似文献   
993.
Background: The female liver is more sensitive to the toxic effect of chronic alcohol intake than the male liver. The aim of the study was to compare the influence of gender and sex hormonal status on apoptosis and cell proliferation following chronic ethanol intake.
Methods: Male and female rats were pair fed for 8 weeks a liquid diet containing 36% of their total daily calories as ethanol (ETOH group) or sucrose (control group). Liver samples were analyzed for apoptosis and hepatocyte proliferation by immunohistochemistry. The hepatic production of factors able to influence cell death and proliferation, such as tumor necrosis factor alpha (TNFα) and interleukin 6 (IL-6) were determined.
Results: In both male and female rats, ethanol intake promoted apoptosis in the liver. This effect of ethanol was more evident in female than male rat livers. Hepatic TNFα levels, which promote apoptosis, are significantly more elevated in female than in male livers. Hepatic IL-6 production, which promotes hepatocyte proliferation, was induced by ethanol only in males, but not female animals.
Conclusion: This observed difference in cytokine responses may contribute to the enhanced sensitivity of female liver to EtOH-induced injury.  相似文献   
994.
995.
A factor that augmented the phagocytosis of IgG-coated ox red blood cells by the human monocyte/macrophage line U937 was identified in cell culture supernatants from two of two patients with angiocentric peripheral T cell lymphomas, three of three patients with angiocentric immunoproliferative lesions that were not frankly malignant, and one of two patients with T lymphoblastic malignancies. The factor was not present in supernatants derived from 14 nonangiocentric peripheral T cell lymphomas of other histologic types nor in ten cases of B cell lymphoma and two cases of Hodgkin's disease. A similar factor was present in the supernatants of concanavalin A (Con A)-stimulated normal peripheral blood mononuclear cells and in the supernatants of IL-2- dependent T cell lines derived from normal peripheral blood. The factor had an apparent mol wt of greater than 50,000 daltons, was heat labile (100 degrees C for two minutes), and stable at pH 2.0. Its stimulation of phagocytosis was independent of any increase in number of Fc receptors. Thus, this factor is probably not gamma-interferon. This factor may play a pathogenetic role in the hemophagocytic syndromes associated with certain T cell malignancies and immunodeficient states.  相似文献   
996.
997.
998.
BackgroundThe American Heart Association (AHA) has defined Life's Simple 7 (LS7) as a measure of overall cardiovascular health . Nonalcoholic fatty liver disease (NAFLD) has been involved as a risk factor for cardiovascular disease. We evaluated the association between LS7 and NAFLD.MethodsWe evaluated participants form the Multi-Ethnic Study of Atherosclerosis (MESA) cohort. Cardiovascular health score was calculated from the Life's Simple 7 metrics. A score of 0-8 was considered inadequate, 9-10 average, and 11-14 optimal. NAFLD was defined using noncontrast cardiac computed tomography (CT) and a liver/spleen attenuation ratio (L/S) < 1. Multivariable regression were performed to evaluate the association.ResultsOur cross-sectional analysis of 3901 participants showed 19% (n = 747) had optimal cardiovascular health, 33% (n = 1270) had average, and 48% (n = 1884) had inadequate. White participants were most likely to have an optimal score (51%, n = 378), whereas African American participants had the lowest proportion with optimal scores (16%, n = 120; P < 0.001). The overall prevalence of NAFLD was 18% with a distribution of 7%, 14%, and 25% in the optimal, average, and inadequate score categories, respectively (P < 0.001). Adjusted for risk factors, average and optimal health categories had lower odds of NAFLD compared to those with inadequate scores: odds ratio for average, 0.44 (95% confidence interval 0.36-0.54); optimal, odds ratio 0.19 (95% confidence interval 0.14-0.26). This association was similar across gender, race and age groups.ConclusionA more favorable cardiovascular health score was associated with a lower prevalence of NAFLD. This study may suggest a potential of Life's Simple 7 in the prevention of liver disease.  相似文献   
999.
BackgroundWhether deep venous thrombosis involving the pelvic veins or inferior vena cava is associated with higher in-hospital mortality or higher prevalence of in-hospital pulmonary embolism than proximal or distal lower extremity deep venous thrombosis is not known.MethodsThis was a retrospective cohort study based on administrative data from the Nationwide Inpatient Sample, 2016, 2017. Patients hospitalized with a primary diagnosis of deep venous thrombosis at known locations were identified by International Classification of Diseases-10-Clinical Modification codes.ResultsIn-hospital all-cause mortality with deep venous thrombosis involving the inferior vena cava in patients treated only with anticoagulants was 2.2% versus 0.8% with pelvic vein deep venous thrombosis (p<0.0001), 0.7% with proximal deep venous thrombosis (p<0.0001) and 0.2% with distal deep venous thrombosis (p<0.0001). Mortality with anticoagulants was similar with pelvic vein deep venous thrombosis compared with proximal lower extremity deep venous thrombosis, 0.8% versus 0.7% (p=0.39). Lower mortality was shown with pelvic vein deep venous thrombosis treated with thrombolytics than with anticoagulants, 0% versus 0.8% (p<0.0001). In-hospital pulmonary embolism occurred in 11% to 23%, irrespective of the site of deep venous thrombosis.ConclusionPatients with deep venous thrombosis involving the inferior vena cava had higher in-hospital mortality than patients with deep venous thrombosis at other locations. Pelvic vein deep venous thrombosis did not result in higher mortality or more in-hospital pulmonary embolism than proximal lower extremity deep venous thrombosis. The incidence of in-hospital pulmonary embolism was considerable with deep venous thrombosis at all sites.  相似文献   
1000.
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