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   49835篇
  免费   3973篇
  国内免费   137篇
耳鼻咽喉   393篇
儿科学   1994篇
妇产科学   1375篇
基础医学   7088篇
口腔科学   1014篇
临床医学   6818篇
内科学   9648篇
皮肤病学   981篇
神经病学   5124篇
特种医学   1133篇
外科学   4383篇
综合类   418篇
一般理论   66篇
预防医学   6056篇
眼科学   763篇
药学   2845篇
  2篇
中国医学   57篇
肿瘤学   3787篇
  2024年   65篇
  2023年   464篇
  2022年   651篇
  2021年   1379篇
  2020年   1014篇
  2019年   1506篇
  2018年   1657篇
  2017年   1297篇
  2016年   1425篇
  2015年   1479篇
  2014年   1903篇
  2013年   2789篇
  2012年   3910篇
  2011年   4015篇
  2010年   2170篇
  2009年   1937篇
  2008年   3215篇
  2007年   3288篇
  2006年   3217篇
  2005年   3047篇
  2004年   2928篇
  2003年   2682篇
  2002年   2426篇
  2001年   383篇
  2000年   270篇
  1999年   324篇
  1998年   540篇
  1997年   410篇
  1996年   362篇
  1995年   352篇
  1994年   278篇
  1993年   273篇
  1992年   195篇
  1991年   163篇
  1990年   152篇
  1989年   116篇
  1988年   133篇
  1987年   93篇
  1986年   95篇
  1985年   105篇
  1984年   106篇
  1983年   109篇
  1982年   134篇
  1981年   129篇
  1980年   106篇
  1979年   67篇
  1978年   68篇
  1977年   50篇
  1976年   49篇
  1972年   36篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Diagnosis and management of anaphylaxis   总被引:7,自引:0,他引:7       下载免费PDF全文
ANAPHYLAXIS IS A SEVERE SYSTEMIC ALLERGIC reaction that is potentially fatal. It requires prompt recognition and immediate management. Anaphylaxis has a rapid onset with multiple organ–system involvement and is mostly caused by specific antigens in sensitized individuals. Reactions typically follow a uniphasic course, however, 20% will be biphasic in nature. The second phase usually occurs after an asymptomatic period of 1–8 hours, but there may be a 24-hour delay. Protracted anaphylaxis may persist beyond 24 hours. Concurrent β-blocker therapy may adversely affect the response to management. Epinephrine is the treatment of choice and should be administered immediately. Secondary measures include circulatory support, H1 and H2 antagonists, corticosteroids and, occasionally, bronchodilators. Post-treatment observation of these patients is necessary, and they should remain within ready access of emergency care for the following 48 hours.  相似文献   
62.
63.
Context One in seven US children and adolescents is obese, yet little is known about their health‐related quality of life (QOL). Objective To examine the health‐related QOL of obese children and adolescents compared with children and adolescents who are healthy or those diagnosed as having cancer. Design, setting and participants Cross‐sectional study of 106 children and adolescents (57 males) between the ages of 5 and 18 years [mean (SD) 12.1 (3) years], who had been referred to an academic children's hospital for evaluation of obesity between January and June 2002. Children and adolescents had a mean (SD) body mass index (BMI) of 34.7 (9.3) and BMI z‐score of 2.6 (0.5). Main outcome measures Child self‐report and parent‐proxy report using a paediatric QOL inventory generic core scale (range 0–100). The inventory was administered by an interviewer for children aged 5 through 7 years. Scores were compared with previously published scores for healthy children and adolescents and children and adolescents diagnosed as having cancer. Results Compared with healthy children and adolescents, obese children and adolescents reported significantly (P < 0.001) lower health‐related QOL in all domains [mean (SD) total score, 67 (16.3) for obese children and adolescents; 83 (14.8) for healthy children and adolescents]. Obese children and adolescents were more likely to have impaired health‐related QOL than healthy children and adolescents [odds ratio (OR) 5.5; 95% confidence interval (CI) 3.4–8.7] and were similar to children and adolescents diagnosed as having cancer (OR 1.3; 95% CI 0.8–2.3). Children and adolescents with obstructive sleep apnoea reported a significantly lower health‐related QOL total score [mean (SD), 53.8 (13.3)] than obese children and adolescents without obstructive sleep apnoea [mean (SD), 67.9 (16.2)]. For parent‐proxy report, the child or adolescent's BMI z‐score was significantly inversely correlated with total score (r = ?0.246; P = 0.01), physical functioning (r = ?0.263; P < 0.01), social functioning (r = ?0.347; P < 0.001), and psychosocial functioning (r = ?0.209; P = 0.03). Conclusions Severely obese children and adolescents have lower health‐related QOL than children and adolescents who are healthy and similar QOL as those diagnosed as having cancer. Physicians, parents and teachers need to be informed of the risk for impaired health‐related QOL among obese children and adolescents to target interventions that could enhance health outcomes.  相似文献   
64.
65.
Although several studies have demonstrated the efficacy of subcutaneous immunotherapy in allergic asthma, few have shown the same benefit using sublingual immunotherapy (SLIT) in asthmatic patients. This study was conducted to assess the efficacy of house dust mite (HDM) SLIT in addition to allergen avoidance and standard pharmacologic treatment. A double-blind, placebo-controlled trial was performed in 111 children (aged 5-15 yr) with HDM-induced mild-to-moderate asthma. After a 4-week baseline phase, patients were randomly assigned to receive SLIT with tablets of HDM extract (n = 55) or placebo (n = 56) for 18 months. Pharmacologic treatment was adjusted every 3 months following a step-down approach. Asthma symptom scores, reduction in use of inhaled corticosteroids and inhaled beta(2)-agonists, rhinitis symptoms, lung function tests, skin sensitivity to HDM, dust mite-specific immunoglobulin (Ig) E and IgG(4), and quality of life (QoL) were assessed during the study. After 18 months of treatment, diurnal and nocturnal asthma symptoms scores did not show significant differences between SLIT and placebo groups. Inhaled corticosteroids and inhaled beta(2)-agonists use was reduced in both groups without significant differences between groups. There were no significant differences in lung function (forced expiratory volume in 1 s and peak flow rate variations) between groups. Rhinitis symptom score decreased in both groups, with no difference between the two groups. The severity dimension of QoL was significantly improved in the SLIT group (age 6-12 yr). SLIT induced a significant reduction of skin sensitivity to HDM (p < 0.01) and a significant increase in HDM-specific IgE and IgG(4) antibodies (p < 0.001) in the SLIT group compared with the placebo group. SLIT was well tolerated with mild/moderate local adverse events. No severe systemic reactions were reported. This study indicates that, when mild-moderate asthmatic children are optimally controlled by pharmacologic treatment and HDM avoidance, SLIT does not provide additional benefit, despite a significant reduction in allergic response to HDM. Under such conditions, only a complete, but ethically unfeasible, discontinuation of inhaled corticosteroid would have demonstrated a possible benefit of SLIT.  相似文献   
66.
This paper identifies the need for more specific guidelines in preparing faculty to use and develop computer-based instructional materials. Cory's model for faculty development is described and planning considerations are outlined. Finally, components of this multifaceted approach to faculty development—identifying available resources, emphasizing the current uses of computers, providing computer literacy/faculty awareness sessions, focusing on the instructional use of microcomputers, collaboration, and communication—are discussed.  相似文献   
67.
Legionnaire's disease was first identified and described in January 1977. Even today, it is often regarded as an unusual or exotic disease, when in fact it is a very common form of community and nosocomial acquired pneumonia. The major roles of the acute care nurse, including patient health education; psychosocial needs of the patient; and strategies for disease prevention and control, are discussed.  相似文献   
68.
BACKGROUND: Psychological morbidity after an acute myocardial infarction (AMI) is known to be common, but can be addressed by appropriate rehabilitation. The area in which this research was conducted experiences high rates of deprivation and of coronary heart disease and limited access to hospital-based rehabilitation. Responding to concern about psychological needs of AMI patients, a self-help package was introduced and evaluated alongside standard hospital-based cardiac rehabilitation. AIMS: To evaluate the impact of a home-based self-help package (the Heart Manual), alongside existing cardiac rehabilitation provision, on psychological morbidity and health status after AMI. A secondary aim was to assess the suitability of the Heart Manual for older patients aged over 80 years. METHODS: A controlled observational study, comparing two cohorts of patients discharged from hospital after AMI. The intervention group was given the self-help package in addition to standard care. The control group received standard care alone. Outcome measures used were the Hospital Anxiety and Depression Scale and the EuroQol. RESULTS: The intervention group showed significant improvement in anxiety and depression scores after 3 months and nonsignificant improvement in general health status. Patients who attended hospital-based rehabilitation classes, and those aged over 80 years, also benefited from the intervention. CONCLUSION: A home-based self-help rehabilitation package is an effective tool alongside hospital-based rehabilitation classes and can be given to all age groups.  相似文献   
69.
70.
Chronic metabolic acidosis induces net Ca efflux from bone; this osteoclastic bone resorption is mediated by increased osteoblastic prostaglandin synthesis. Cyclooxygenase, the rate-limiting enzyme in prostaglandin synthesis, is present in both constitutive (COX-1) and inducible (COX-2) forms. We report here that acidosis increases both osteoblastic RNA and protein levels for COX-2 and that genetic deficiency or pharmacologic inhibition of COX-2 significantly reduces acid-induced Ca efflux from bone. INTRODUCTION: Incubation of neonatal mouse calvariae in medium simulating physiologic metabolic acidosis induces an increase in osteoblastic prostaglandin E2 (PGE2) release and net calcium (Ca) efflux from bone. Increased PGE2 is necessary for acid-induced bone resorption, because inhibition of cyclooxygenase activity with indomethacin significantly decreases not only PGE2 production but also Ca release. Cyclooxygenase is present in both constitutive (COX-1) and inducible (COX-2) forms. Because COX-2 activity has been implicated in several forms of pathological bone resorption, we tested the hypothesis that COX-2 is critical for acid-induced, cell-mediated bone Ca efflux. MATERIALS AND METHODS: To determine the effect of metabolic acidosis on COX-2 RNA and protein, primary cells isolated from neonatal CD-1 mouse calvariae were cultured in neutral (Ntl) or physiologically acidic medium (Met). RNA levels for COX-2 and COX-1 were measured by quantitative real-time PCR. Levels of COX-2 and COX-1 protein were measured by immunoblot analysis. To determine the effect of acidosis on bone Ca efflux in genetically deficient COX-2 mice, mice heterozygous for the COX-2 knockout (strain B6;129S7-Ptgs2(tm1Jed)/J) were used as breeders, and neonatal calvariae were cultured in Ntl or Met. To determine the effects of the specific COX-2 inhibitor, NS398, on acid-induced bone resorption, CD-1 calvariae were incubated in Ntl or Met with or without NS398 (1 microM). Medium PGE2 was assayed by ELISA. RESULTS: Incubation of mouse calvarial cells in Met significantly increased COX-2 RNA and protein levels without a change in COX-1. Increased COX-2 protein levels in response to Met were also observed in cultured calvariae. Acid-induced, cell-mediated Ca efflux from B6;129S7-Ptgs2(tm1Jed)/J calvariae was dependent on genotype. From 0 to 24 h, when physicochemical Ca efflux predominates, Met significantly increased net Ca efflux in all genotypes. After 24 h, when cell-mediated Ca efflux predominates, Met induced greater Ca efflux from (+/+) than from (+/-), and there was no increase from (-/-). In calvariae from CD-1 mice, NS398 significantly inhibited both the acid-induced increase in PGE2 and Ca release. CONCLUSIONS: The specific acid-induced increase in COX-2 RNA and protein levels and the dependency of the increased Ca efflux on COX-2 activity, as determined by both genetic deficiency and pharmacologic inhibition, show that COX-2 is critical for acid-induced, cell-mediated bone resorption.  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