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   17961篇
  免费   431篇
  国内免费   279篇
耳鼻咽喉   325篇
儿科学   571篇
妇产科学   289篇
基础医学   2331篇
口腔科学   280篇
临床医学   1129篇
内科学   4717篇
皮肤病学   246篇
神经病学   1419篇
特种医学   505篇
外国民族医学   1篇
外科学   2314篇
综合类   297篇
现状与发展   1篇
一般理论   12篇
预防医学   1653篇
眼科学   380篇
药学   1202篇
中国医学   96篇
肿瘤学   903篇
  2024年   5篇
  2023年   33篇
  2022年   22篇
  2021年   13篇
  2020年   17篇
  2019年   16篇
  2018年   24篇
  2017年   9篇
  2016年   12篇
  2015年   9篇
  2014年   58篇
  2013年   43篇
  2012年   1831篇
  2011年   1927篇
  2010年   347篇
  2009年   182篇
  2008年   1562篇
  2007年   1621篇
  2006年   1658篇
  2005年   1714篇
  2004年   1532篇
  2003年   1554篇
  2002年   1377篇
  2001年   918篇
  2000年   1361篇
  1999年   588篇
  1998年   55篇
  1997年   21篇
  1996年   15篇
  1995年   10篇
  1994年   17篇
  1993年   13篇
  1992年   9篇
  1991年   11篇
  1990年   5篇
  1989年   17篇
  1988年   8篇
  1987年   5篇
  1986年   5篇
  1985年   6篇
  1984年   8篇
  1983年   7篇
  1982年   6篇
  1981年   2篇
  1980年   4篇
  1979年   4篇
  1939年   1篇
  1935年   1篇
  1931年   2篇
  1912年   1篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
992.
993.
994.
Syncopal episodes are frequent in adolescence. Syncope is usually a benign, self-limiting condition but it may be a warning sign of serious disease that must be diagnosed and appropriately treated. The present article provides a review of the basic principles of the differential diagnosis of syncope in the adolescent patient and treatment recommendations.  相似文献   
995.
996.
997.
OBJECTIVE. To study the perinatal results in our population, following the prenatal ultrasound diagnosis of a single umbilical artery (SUA), as this alteration is associated with fetal malformations, chromosomal abnormality, and poor perinatal results. MATERIALS AND METHODS. A retrospective review of all obstetric ultrasounds carried out between October 2000 and December 2003 in our service, obtaining the postnatal results of the fetuses diagnosed with an SUA. RESULTS. From a total of 5,987 pregnant patients examined by ultrasound scan at 20th week, an SUA was found in 40 cases, representing an incidence of 0.7%. Of these, 84.6% were normal pregnancies at birth and 15.4% presented other malformations and/or chromosomal abnormalities. No aneuploidy was found in pregnancies where there were no other associated findings in the ultrasound scan at 20 weeks. All cases with serious congenital malformations accompanying the SUA were diagnosed prenatally. There was a 5% of perinatal mortality rate among our fetuses with SUA, which represents a mortality rate 10 times greater than the overall rate among our patients. CONCLUSIONS. The ultrasound discovery of an SUA implies the meticulous search for other associated malformations, and in the absence of these, the risk of a chromosomal abnormality is very low, unless it is a high-risk patient. However, the growth and wellbeing of the fetus must be carefully monitored in the last 3 months, although the ultrasound scan does not show any other associated alterations.  相似文献   
998.
In insects, the molecular basis of ecdysteroid action has been analysed in great detail in flies and moths, but rarely in primitive orders. Using the primitive hemimetabolous insect Blattella germanica, the German cockroach, as a model, we isolated two cDNAs of RXR/USP, a component of the heterodimeric ecdysone receptor. These two cDNAs correspond to two isoforms, named BgRXR-S (short form) and BgRXR-L (long form). Both are identical except for a 23-amino acid deletion/insertion located in the loop between helices H1 and H3 of the ligand-binding domain. Pattern expression studies show that the two isoforms are differentially expressed throughout the life cycle of B. germanica. During embryogenesis, BgRXR-L occurs in early embryos, whereas BgRXR-S is highly expressed in middle and late embryogenesis. In the penultimate and last larval instars, BgRXR-S mRNA is the predominant form in the fat body and in the prothoracic gland. In the adult female, BgRXR-S mRNA predominates in the fat body, whereas BgRXR-L mRNA predominates in the ovary. Experiments performed with fat body and embryo cells incubated in vitro showed that the expression of BgRXR-S and BgRXR-L is not affected by 20-hydroxyecdysone or by juvenile hormone III.  相似文献   
999.
OBJECTIVE: To assess the prevalence of rheumatoid arthritis (RA) in a representative study of the South Transdanubian region of Hungary. METHODS: Ten thousand individuals aged between 14-65 years were interviewed. The stratified sample was representative for age, sex and urban/rural residence structure of the regional population of the South-West Hungarian region. As a second step, all individuals with possible RA were asked to undergo a clinical investigation to confirm the diagnosis of RA according to the American Rheumatism Association (ARA) 1987 criteria. Of 10,000 interviewed individuals, 632 reported having RA or symptoms including digital pain, stiffness, and/or swelling. Two hundred and twenty-four individuals were investigated clinically. Individuals fulfilling the 1987 ARA criteria were considered as having definite RA, and their clinical data were evaluated. RESULTS: RA was confirmed in 13 cases. The male/female ratio was 3/10. The prevalence of RA among individuals aged 14-65 years was 0.37% (95% confidence interval, CI: 0.26-0.51), 0.23% (95% CI: 0.15-0.35) in men and 0.48% (95% CI: 0.35-0.64) in women. CONCLUSION: The prevalence of RA in the South Transdanubian region of Hungary is similar to those of other recent studies from other regions around the world.  相似文献   
1000.
PURPOSE: The purpose of this study was to examine the association of body mass index (BMI) and aerobic fitness on cardiovascular disease (CVD) risk factors in adolescents. METHODS: The sample included 416 boys and 345 girls 9-18 y of age from the Québec Family Study. Participants were cross-tabulated into four groups using a median split of age-adjusted physical working capacity (PWC) and body mass index (BMI). Group differences in age-adjusted CVD risk factors (blood pressures, fasting total cholesterol (CHOL), LDL -C, HDL-C, HDL/CHOL, triglycerides, glucose, and a composite risk factor score) were examined by two-way ANOVA. RESULTS: Several CVD risk factors showed significant main effects for PWC, BMI and/or the PWC by BMI interaction. In general, low fit males and females had higher blood lipids and glucose compared to their high fit counterparts within BMI categories although none of the differences reached statistical significance. The high fit/low BMI group showed the best CVD risk factor profile while the low fit/high BMI showed a poorer profile as evidenced by several significant differences between these two groups. Other significant differences occurred for various risk factors between groups. CONCLUSION: Both aerobic fitness and BMI show an independent association with CVD risk factors in adolescents.  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