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   1541篇
  免费   178篇
  国内免费   28篇
耳鼻咽喉   6篇
儿科学   143篇
妇产科学   24篇
基础医学   201篇
口腔科学   90篇
临床医学   156篇
内科学   281篇
皮肤病学   49篇
神经病学   33篇
特种医学   173篇
外科学   223篇
综合类   38篇
预防医学   114篇
眼科学   40篇
药学   81篇
中国医学   2篇
肿瘤学   93篇
  2023年   14篇
  2022年   10篇
  2021年   13篇
  2020年   14篇
  2019年   7篇
  2018年   44篇
  2017年   46篇
  2016年   41篇
  2015年   61篇
  2014年   76篇
  2013年   107篇
  2012年   49篇
  2011年   31篇
  2010年   77篇
  2009年   92篇
  2008年   33篇
  2007年   51篇
  2006年   49篇
  2005年   29篇
  2004年   28篇
  2003年   19篇
  2002年   21篇
  2001年   15篇
  2000年   11篇
  1999年   26篇
  1998年   102篇
  1997年   86篇
  1996年   99篇
  1995年   63篇
  1994年   74篇
  1993年   39篇
  1992年   15篇
  1991年   21篇
  1990年   14篇
  1989年   31篇
  1988年   31篇
  1987年   30篇
  1986年   27篇
  1985年   26篇
  1984年   12篇
  1983年   11篇
  1982年   23篇
  1981年   16篇
  1980年   16篇
  1979年   5篇
  1978年   6篇
  1977年   9篇
  1976年   13篇
  1975年   9篇
  1966年   1篇
排序方式: 共有1747条查询结果,搜索用时 15 毫秒
991.
992.
Multicore myopathy with restrictive cardiomyopathy   总被引:1,自引:0,他引:1  
A 10-y-old girl is presented who suffered mild muscular weakness and exercise intolerance from the age of 1 y onwards, with progression appearing from the age of about 8 y. Multicore myopathy and restrictive cardiomyopathy were diagnosed. Literature concerning the coexistence of multicore myopathy and cardiomyopathy is reviewed.  相似文献   
993.
OBJECTIVE: To determine how young children changed their overall diet when they changed their fat intake after 3 months of participating in a nutrition education demonstration study designed to lower low-density lipoprotein cholesterol and cardiovascular risk. METHODS: Three 24-hour dietary recalls were collected from 303 4- to 10-year-old children at baseline and 3 months later. At both times, mean number of servings from food groups, grams of fat contributed from food groups, and intake of calories and nutrients were calculated and compared among quartiles of children formed according to change in their percent of calories from total fat after 3 months. RESULTS: Children who reduced their percent of calories from total fat most (ie, by an average of 8.5%) after 3 months consumed fewer servings from meats, eggs, dairy, fats/oils, and breads but tended to increase their number of servings from lower-fat foods within those food groups, particularly from dairy foods. These children also increased their mean intake of fruits, vegetables, and desserts, and maintained average intakes of all nutrients (except vitamin D) in excess of two thirds of the respective recommended dietary allowance. CONCLUSIONS: Young children who reduced their percent of calories from total fat in accordance with the current National Cholesterol Education Program recommendations accomplished this by reducing their overall intake of higher-fat foods, replacing higher-fat foods with lower-fat foods within several food groups, particularly within the dairy group (eg, drinking skim milk instead of whole milk) and by consuming more servings of fruits, vegetables, and very-low-fat desserts. These behaviors did not compromise their mean calorie or nutrient intakes, showing that it is possible for young children to lower their fat intake safely to reduce their risk of future heart disease.  相似文献   
994.
995.
Cyclic food restriction, insulin and mammary cell proliferation in the rat   总被引:1,自引:1,他引:1  
We reported recently that weight cycling significantly increased the incidence of mammary cancer in virgin female rats that were pretreated with N-methyl-N-nitrosourea. The present study investigated the effect of weight cycling on mammary epithelial cell proliferation and its relationship to changes in plasma insulin, estrogen, progesterone and urinary corticosterone in 30 female virgin Sprague-Dawley rats. Animals were fed a modified AIN-76A diet containing 24.6% corn oil by weight. Weight-cycled (WC) rats were food restricted daily by either 33% or 50% of non-restricted controls for 1 week followed by 3 weeks compensatory refeeding and weight recovery over 18 weeks or 4.5 weight cycles. WC rats consumed 6-10% less food than controls (P = 0.01) but showed a 71- 89% greater efficiency of food utilization for growth (P < 0.0001) than controls. There were no differences in total weight gain during treatment. Mammary lobuloalveolar and ductal cell proliferation of WC rats, measured by 5-bromo-2'deoxyuridine labelling, increased in a dose- response fashion, P = 0.03, P = 0.06 respectively in comparison to controls. Energy and substrate utilization measured by indirect calorimetry indicated WC animals expended less energy (P = 0.005) and utilized less glucose (P = 0.0001) and protein (P = 0.006) during restriction, and less lipid during recovery (P = 0.05) than controls. There were no significant differences in hormone levels between groups. Multiple regression analysis with plasma insulin, estrogen, progesterone and urinary corticosterone as independent variables (r = 0.947, r2 = 0.897, P = 0.003) showed that plasma insulin was the only significant predictor (P < 0.01) of mammary cell proliferation. In accord with this observation, tyrosine-phosphorylated activation of insulin receptor substrate-1, detected by immunoprecipitation and Western immunoblot analysis in mammary tumors of WC rats from our previous study, was 3-5 times greater than in non-restricted controls (P < 0.01). Present findings suggest that weight cycling in rats increases risk of breast cancer development via insulin stimulated mammary cell proliferation.   相似文献   
996.
The lack of oral anticoagulant guidelines specific to paediatric practice has led to the adoption of adult regimens, often without scientific evidence of efficacy or safety. A two year prospective study of anticoagulant control was carried out in 45 children aged 9 months to 18 years, the majority of whom were receiving primary prophylactic anticoagulation. The main indication was congenital heart disease, either with (n = 8) or without (n = 34) mechanical valve prosthesis. During a follow up period of 602 patient months the average interval between visits was three weeks. Target international normalised ratios (INRs) were achieved on 62% and 39% of visits for children with low target INR (2.0-3.0) and high target INR (3.0-4.0) respectively. However warfarin dose was altered on only 22% of visits. Warfarin doses required to achieve a stable INR of 2.0-3.0 in 33 children were strongly correlated with weight [dose (mg/d) = 0.07 x weight (kg) + 0.54] but independently influenced by age. No thrombotic complications were recorded, and haemorrhagic events were infrequent (2.1% of visits) and, with one exception, minor. Safe outpatient oral anticoagulation is feasible in children, whose warfarin requirements appear moderately predictable and whose control is no more erratic than that of adults.  相似文献   
997.
Biliary obstruction by viscid mucus, although important, may not be the only factor for the development of liver disease in some patients with cystic fibrosis. In the present study the relationship between immune responses to liver antigens and the presence of liver damage was investigated using the leucocyte migration test and lymphocyte cytotoxicity to isolated rabbit hepatocytes. Inhibition of leucocyte migration by purified liver-specific lipoprotein, derived from hepatocyte plasma membrane, was found in 9 of 11 children with liver disease, but in only 5 of 14 with cystic fibrosis and no overt liver disease (P < 0.025). Lymphocyte toxicity to isolated rabbit hepatocytes was significantly increased in 10 of 13 children with liver disease, but in only 6 of 29 children without liver disease (P < 0.001). Experiments using lymphocyte subpopulations showed that the cytotoxicity was mediated by a non-T-cell population and could be blocked with liver-specific lipoprotein in 7 out of 10 cases, suggesting that the reaction in these patients was specifically directed against liver-specific lipoprotein. The study suggests that sensitisation against liver membrane antigens, whether arising primarily or secondarily in some way to other hepatic lesions, may contribute to the progression of liver damage in cystic fibrosis.  相似文献   
998.
Serial changes in plasma levels of calcium, phosphorus, magnesium, alkaline phosphatase, and total proteins have been investigated in 138 healthy, term Caucasian infants. Blood samples were obtained for each infant from cord blood and on day 1 and day 6. The infants were studied in three groups according to whether they were breast fed, received 'Ostermilk No. 1' or 'Cow and Gate V' formulas. Levels of calcium, phosphorus, magnesium, alkaline phosphatase, and total proteins did not differ between the groups at birth or on day 1. By day 6 calcium levels were higher and phosphorus levels lower in the breast-fed infants compared with either of the artificially-fed groups. Phosphorus levels were lower in the V Formula group compared with the Ostermilk group but the mean calcium levels of these two groups did not differ significantly. However, only 2-8% of the V Formula group developed hypocalcaemia compared with 18-2% of the Ostermilk group. The only infant developing clinical tetany belonged to the group fed Ostermilk. Evidence is also given which suggests that those infants with low calcium levels on day 1 who were fed the high-solute milk tended to show a fall in calcium by day 6. This did not apply to the two other groups. It is concluded that the use of adapted cows' milk preparations for infant feeding should lead to a reduction in the incidence of neonatal tetany.  相似文献   
999.
Infections of the musculoskeletal system: high-field-strength MR imaging   总被引:1,自引:0,他引:1  
Beltran  J; Noto  AM; McGhee  RB; Freedy  RM; McCalla  MS 《Radiology》1987,164(2):449-454
Twenty-two patients with clinical findings consistent with osteomyelitis, soft-tissue infection, or both were studied with magnetic resonance (MR) imaging at 1.5 T. Another 15 patients with joint effusion but no clinical or laboratory signs of infection served as controls. Soft-tissue abscesses, osteomyelitis, joint and tendon sheath effusion, and cellulitis were well depicted on MR imaging, allowing the correct diagnosis of presence and extent of infection in all but two cases. MR imaging was as sensitive as technetium-99m methylene diphosphonate bone scintigraphy in demonstrating osteomyelitis and was more specific and more sensitive than other scintigraphic techniques in demonstrating soft-tissue infections, primarily because of its superior spatial resolution. Computed tomography, performed in seven cases, was as accurate as MR imaging in demonstrating bone and soft-tissue infections. Infected and noninfected synovial effusions had the same signal intensity, but associated findings such as soft-tissue fluid collections or osteomyelitis made the distinction possible.  相似文献   
1000.
Gastrointestinal tract: dynamic MR studies with echo-planar imaging   总被引:2,自引:0,他引:2  
Gastrointestinal (GI) tract motility was depicted in four human volunteers with the high-speed echo-planar imaging technique: modulus blipped echo-planar single-pulse technique (MBEST). Data acquisition times of 64 and 128 msec obviate image degradation due to motion without the need for gut paralysis and allow imaging of the GI tract in real time. Peristaltic patterns of the gastric antrum and proximal small intestine were depicted for fasting and fed subjects and subjects in whom peristalsis had been pharmacologically stimulated. The potential for quantitative measurements of GI tract motion with this new technique was demonstrated.  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