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   711篇
  免费   53篇
  国内免费   19篇
儿科学   26篇
妇产科学   19篇
基础医学   47篇
口腔科学   22篇
临床医学   67篇
内科学   139篇
皮肤病学   12篇
神经病学   129篇
特种医学   110篇
外科学   49篇
综合类   22篇
一般理论   1篇
预防医学   76篇
眼科学   5篇
药学   28篇
肿瘤学   31篇
  2023年   7篇
  2022年   5篇
  2021年   4篇
  2020年   5篇
  2019年   7篇
  2018年   5篇
  2017年   9篇
  2016年   10篇
  2015年   14篇
  2014年   23篇
  2013年   30篇
  2012年   31篇
  2011年   31篇
  2010年   26篇
  2009年   22篇
  2008年   23篇
  2007年   35篇
  2006年   26篇
  2005年   28篇
  2004年   20篇
  2003年   25篇
  2002年   22篇
  2001年   17篇
  2000年   10篇
  1999年   12篇
  1998年   25篇
  1997年   19篇
  1996年   13篇
  1995年   20篇
  1994年   14篇
  1993年   18篇
  1992年   16篇
  1991年   8篇
  1990年   16篇
  1989年   26篇
  1988年   21篇
  1987年   26篇
  1986年   17篇
  1985年   20篇
  1984年   5篇
  1982年   4篇
  1981年   11篇
  1980年   8篇
  1979年   4篇
  1978年   5篇
  1977年   8篇
  1976年   6篇
  1975年   10篇
  1955年   2篇
  1938年   1篇
排序方式: 共有783条查询结果,搜索用时 31 毫秒
1.
2.
3.
4.
A retrospective follow-up study to ascertain the relationship between the level of serum zinc and its rate of change during gestation and birthweight was conducted in 476 women of lower socioeconomic status. Serum zinc concentrations measured at approximately 16 (early) and 32 weeks (later) in gestation were both found to be significant predictors of birthweight. Even after controlling for gestational age at birth and other determinants of birthweight, for each microgram/dl increase in serum zinc early and later in pregnancy, birthweight increased by 5.8 and 8.6 g, respectively. Furthermore, after adjustment for initial zinc levels both the total change (beta = -7.0, P = 0.0007) and the rate of change (beta = -60.8, P = 0.007) in serum zinc during pregnancy were inversely associated with birthweight, i.e., the larger the fall in serum zinc during pregnancy, the smaller the infant. Low serum zinc level (less than 60 micrograms/dl) late in pregnancy was associated with greater than a five-fold increase in the odds (OR = 5.8, 95% CI = 1.8, 16.4) of giving birth to a low birthweight infant. The results of this study suggest a threshold for maternal serum zinc below which the prevalence of low birthweight increases rapidly.  相似文献   
5.
In animals, perfluorochemicals (PFCs) are effective ultrasound (US) contrast agents that produce hepatic, splenic, and tumor enhancement. The use of Fluosol-DA 20%, an emulsion of perfluorodecalin and perfluorotripropylamine, was studied in nine non-critically ill patients with cancer who had liver lesions. US studies without Fluosol were compared with studies obtained 24, 48, and 72 hours after Fluosol infusion. Vital signs and extensive laboratory analyses are performed before and after Fluosol infusion. Liver metastases from colonic, pancreatic, and gastric carcinoma exhibited rim or diffuse enhancement after a Fluosol dose of 1.6 g/kg or greater. Fluosol produced echogenic enhancement of the liver and spleen relative to kidney at a dose of 2.4 g/kg, allowing the detection of nonenhancing lesions. In addition, Fluosol at a dose of 1.6 g/kg or greater allowed detection of lesions not seen before contrast medium was administered in three of the seven patients studied. There was a mild increase in the level of serum glutamic oxaloacetic transaminase in two patients, one given 2.4 and the other 3.2 g/kg of Fluosol. Mild and transient allergic reactions without change in vital signs were experienced by two patients.  相似文献   
6.
In 1984, a prospective cohort study, Coronary Artery Risk Development in Young Adults (CARDIA) was initiated to investigate life-style and other factors that influence, favorably and unfavorably, the evolution of coronary heart disease risk factors during young adulthood. After a year of planning and protocol development, 5,116 black and white women and men, age 18-30 years, were recruited and examined in four urban areas: Birmingham, Alabama; Chicago, Illinois; Minneapolis, Minnesota, and Oakland, California. The initial examination included carefully standardized measurements of major risk factors as well as assessments of psychosocial, dietary, and exercise-related characteristics that might influence them, or that might be independent risk factors. This report presents the recruitment and examination methods as well as the mean levels of blood pressure, total plasma cholesterol, height, weight and body mass index, and the prevalence of cigarette smoking by age, sex, race and educational level. Compared to recent national samples, smoking is less prevalent in CARDIA participants, and weight tends to be greater. Cholesterol levels are representative and somewhat lower blood pressures in CARDIA are probably, at least in part, due to differences in measurement methods. Especially noteworthy among several differences in risk factor levels by demographic subgroup, were a higher body mass index among black than white women and much higher prevalence of cigarette smoking among persons with no more than a high school education than among those with more education.  相似文献   
7.
8.
OBJECTIVES. This study examined health care-seeking behaviors to elucidate factors that contribute to differences in patterns of coronary heart disease between African Americans and Whites. The prevalence of diagnosed coronary heart disease, patients' perceptions of symptoms and attribution of symptoms, and predictors of painful symptoms and attribution of cardiac symptoms were examined. METHODS. The study involved 2416 patients admitted with diagnoses of coronary artery disease, ischemic heart disease, or myocardial infarction or to rule out myocardial infarction. Structured interview questions were used to obtain demographic information, symptoms precipitating admission, and patients' attribution of their symptoms. Discharge diagnoses were obtained from hospital records. RESULTS. Acute myocardial infarction, unstable angina, nonacute ischemic heart disease, and atherosclerosis were more frequent in White patients. For Blacks, the odds of reporting painful symptoms were only 64% of the odds found for Whites when other factors were controlled, and the odds of attributing symptoms to cardiac origins were almost 50% lower for Blacks than for Whites. CONCLUSIONS. The tendency of Blacks to report fewer painful symptoms and to attribute their symptoms to noncardiac origins may contribute to differences in care-seeking and in medical management of heart disease in Blacks.  相似文献   
9.
Estimates of the cost effectiveness and cost benefit of health promotion-health education methods for pregnant smokers designed to increase birth weight are not available. This paper presents the results of a cost-effectiveness analysis from a recently completed randomized trial to evaluate the effectiveness of self-help smoking cessation methods for pregnant women in public health maternity clinics. The study population--309 pregnant smokers from 3 prenatal clinics--were randomly assigned, during their first clinic visit, to 1 of 3 groups: (a) group 1 received the standard clinic information and advice to quit smoking, (b) group 2 received the standard clinic information and advice to quit plus the manual "Freedom From Smoking in 20 Days" by the American Lung Association, and (c) group 3 received the standard clinic information and advice to quit plus the pregnancy-specific manual "A Pregnant Woman''s Self-Help Guide to Quit Smoking." The quit rates by the end of pregnancy were 2 percent for group 1, 6 percent for group 2, and 14 percent for group 3. Analyses also indicated that the method used for group 3 was the most cost effective: group 3 achieved smoking cessation at less than half the cost experienced by the other two groups. Although additional studies are needed concerning the behavioral impact, cost effectiveness, and cost benefit of self-help health education methods for smoking cessation, the methods tested in this trial are promising as solutions to part of the problem of low birth weight among infants of smoking mothers in the United States.  相似文献   
10.
The nitric oxide pathway in pre-eclampsia: pathophysiological implications   总被引:2,自引:0,他引:2  
Pre-eclampsia, one of the most significant health problems inhuman pregnancy, complicates 6-7% of all gestations and is theleading cause of fetal growth retardation, infant morbidityand mortality, premature birth and maternal death. Recent researchimplicates free radicals in the pathophysiology of pre-eclampsia.This review covers the biochemistry of nitric oxide (NO) andpossible interactions with other free radicals. Studies in therat show that pregnancy is associated with enhanced productionand responsiveness to NO in both reproductive tissues and bloodvessels. Rats infused with NG-nitro-L-arginine methyl ester(L-NAME, a NO synthase inhibitor) have been used as an animalmodel of pre-eclampsia, and the effects of steroid hormoneson blood pressure in this model have been tested. Results suggestthat pre-eclampsia may be a state of NO deficiency. However,in humans there seem to be contradictions regarding the involvementof NO in maternal adaptation to pregnancy. It is suggested thatNO may be one of several systems that act in concert to maintaina symbiotic relationship between mother and fetus. However,the input of each system may be genetically determined.  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