全文获取类型
收费全文 | 1457篇 |
免费 | 125篇 |
国内免费 | 5篇 |
专业分类
耳鼻咽喉 | 3篇 |
儿科学 | 52篇 |
妇产科学 | 25篇 |
基础医学 | 150篇 |
口腔科学 | 47篇 |
临床医学 | 191篇 |
内科学 | 276篇 |
皮肤病学 | 15篇 |
神经病学 | 66篇 |
特种医学 | 267篇 |
外科学 | 113篇 |
综合类 | 46篇 |
一般理论 | 2篇 |
预防医学 | 179篇 |
眼科学 | 23篇 |
药学 | 57篇 |
1篇 | |
中国医学 | 8篇 |
肿瘤学 | 66篇 |
出版年
2021年 | 15篇 |
2020年 | 9篇 |
2018年 | 11篇 |
2017年 | 8篇 |
2016年 | 20篇 |
2015年 | 23篇 |
2014年 | 21篇 |
2013年 | 42篇 |
2012年 | 41篇 |
2011年 | 55篇 |
2010年 | 45篇 |
2009年 | 41篇 |
2008年 | 43篇 |
2007年 | 44篇 |
2006年 | 50篇 |
2005年 | 49篇 |
2004年 | 34篇 |
2003年 | 44篇 |
2002年 | 27篇 |
2001年 | 27篇 |
2000年 | 34篇 |
1999年 | 35篇 |
1998年 | 47篇 |
1997年 | 43篇 |
1996年 | 47篇 |
1995年 | 58篇 |
1994年 | 45篇 |
1993年 | 47篇 |
1992年 | 27篇 |
1991年 | 23篇 |
1990年 | 24篇 |
1989年 | 49篇 |
1988年 | 40篇 |
1987年 | 42篇 |
1986年 | 46篇 |
1985年 | 31篇 |
1984年 | 24篇 |
1983年 | 17篇 |
1982年 | 21篇 |
1981年 | 26篇 |
1980年 | 20篇 |
1979年 | 22篇 |
1978年 | 19篇 |
1977年 | 16篇 |
1976年 | 18篇 |
1975年 | 14篇 |
1969年 | 9篇 |
1967年 | 6篇 |
1957年 | 9篇 |
1954年 | 6篇 |
排序方式: 共有1587条查询结果,搜索用时 15 毫秒
31.
OBJECTIVES: To investigate maternal knowledge and attitudes about otitis media (OM) risk, to estimate the prevalence of risk factors in the first year of life, and to identify barriers to the reduction of risk factors (eg, formula feeding, day care attendance, and exposure to passive smoke). METHODS: Questionnaires mailed to a systematic sample of 504 Minnesota women >/=18 years old identified through 1994 birth certificates. RESULTS: Eighty percent returned a completed survey. According to maternal report, 29% of infants (age 8 to 13 months) had recurrent OM (>/=3 episodes) and 2% had tympanostomy tubes. Forty-six percent attended day care, 29% had >/=1 smoking parent, and 49% breastfed for =2 months. Women were more knowledgeable about OM signs and symptoms than about risk factors. Mean OM knowledge score (the sum of correct true-false responses) was 7.0 (standard deviation = 1.6). Using multiple linear regression, knowledge score was significantly related to marital status, education, age, area of residence, breastfeeding (months), and number of cigarettes smoked per day by the mother, but not to infant or sibling OM history or day care attendance (R = .23). Infant history of OM (odds ratio, 1.9; 95% confidence interval, 1.1 to 3.2) and white race (odds ratio, 0.3; 95% confidence interval, 0. 1 to 0.8), but not the presence of risk factors, were significantly related to having received clinicians' advice about OM prevention advice. CONCLUSION: OM education and prevention programs should target pregnant women and new mothers with OM risk factors, and those who are young, single, and less educated. 相似文献
32.
Hansen LA; Malarkey DE; Wilkinson JE; Rosenberg M; Woychik RE; Tennant RW 《Carcinogenesis》1998,19(10):1837-1845
We previously reported that papillomas can arise from the follicular
epithelium of v-Ha-ras transgenic TGxAC mice. Since the viable-yellow
mutation (A(vy)) of the mouse agouti gene which regulates coat color
pigmentation by acting within the micro-environment of the hair follicle
has been shown to function as a tumor promoter in the liver, we
hypothesized that it may also play a role in TGxAC skin tumorigenesis.
Endogenous agouti protein product was detected in the outer root sheath of
anagen hair follicles following plucking of the hair shaft, but not in the
interfollicular epithelium, in TGxAC mice on an FVB/N genetic background.
It was also detected in papillomas from these mice produced by
12-O-tetradecanoylphorbol-13-acetate (TPA) treatment or plucking.
Expression of the A(vy) allele in the v-Ha-ras transgenic TGxAC mouse line
results in an approximately 2-fold increase in papilloma development
compared with controls which did not carry the A(vy) allele following
twice-weekly treatment with 1.25, 2.5 or 5.0 microg TPA. In addition,
TPA-treated, papilloma-bearing F1 mice which carried the A(vy) allele, but
not F1 mice which did not carry the A(vy) allele, exhibited a syndrome of
humoral hypercalcemia mediated by parathyroid hormone-related protein
(PTHrP) that led to weight loss, hypercalcemia and hypophosphatemia. Thus,
we conclude that the A(vy) allele can influence the development of skin
tumors and PTHrP-mediated humoral hypercalcemia in v-Ha-ras transgenic
TGxAC mice.
相似文献
33.
34.
Octopus vulgaris, Octopus cyanea and Callistoctopus ornatus may co-occur in near-shore shallow reef habitats across the Southwestern Indian Ocean. All three species are harvested, both by small vessels and individual spearfishers and are of considerable socio-economic importance. Phenotypic-based discrimination of the three species is unreliable and at present species-specific catch data are not collected, preventing evaluation of species specific fisheries effects. In light of increasing exploitation rates the development of an unambiguous means of species discrimination is required for sustainable management and conservation of species and intraspecific stocks. In this study, a simple, cost effective, molecular technique to differentiate the three species is described. 相似文献
35.
Theophilus Boye Peter Doyle Fiona McKeown Jonathan Sandler 《Journal of cranio-maxillo-facial surgery》2012,40(3):238-242
A severe Class 2 division 1 dento-facial deformity in an adult is normally treated by a combination of orthodontics and orthognathic surgery. The surgical procedure may involve either a single or double jaw osteotomy. The sagittal split osteotomy with forward mandibular slide has been the procedure of choice for many years for correcting the antero-posterior discrepancy between the dental arches. Although the total subapical mandibular osteotomy was described over 20 years ago, reports of its use in the literature are sparse. We report two cases to demonstrate that it can be the operation of choice for surgical correction of Class 2 dento-facial deformity in carefully selected cases. When performed correctly it can have very good aesthetic and functional results. 相似文献
36.
Obesity, diabetes and metabolic disease represent an ongoing and rapidly worsening public health issue in both the developed, and much of the developing world. Although there are many factors that influence fat storage, it has been clearly demonstrated that the homeostatic cornerstone of metabolism lies within the hypothalamus. Moreover, neuronal damage to vital areas of the hypothalamus can drive reregulation or dysregulation of endocrine function, energy expenditure and appetite, thereby promoting a shift in overall metabolic function towards a state of obesity. Therefore, identification of treatments that influence the hypothalamus to improve obesity and associated metabolic diseases has long been a medical goal. Interestingly, evidence from animal studies suggests that activating the vestibular system, specifically the macular gravity receptor, influences the hypothalamus in a way that decreases body fat storage and causes a metabolic shift towards a leaner state. Given that the macular element of the vestibular system has been shown to activate with transdermal electrical stimulation applied to the mastoids, this may be a potential therapeutic approach for obesity, diabetes or related metabolic diseases, whereby repetitive stimulation of the vestibular system influences hypothalamic control of metabolic homeostasis, thereby encouraging decreased fat storage. Here, we present an up-to-date review of the current literature surrounding the vestibular influence of the hypothalamus and associated homeostatic sites in the context of current and novel therapeutic approaches for improved clinical management of obesity and diabetes. 相似文献
37.
Sociologists of childhood have stressed the importance of children??s experience in the present and children as agents who actively construct their own lives and influence relationships with family and friends. Current thinking in the field of child well-being emphasises the need to consult children as experts in their own lives. Findings from research with children have led to important insights about what contributes to well-being. Relationships with family and friends have been found to be central to well-being whilst bullying by peers deeply impacts on their well-being. Shared activities appear to be the context for children to not only master competences but also learn about and negotiate relationships. The Growing Up in Ireland interviews with 9?year old children were re-analysed with a view to exploring these crucial domains and how they impact on the children??s well-being. The children were found to have a wide circle of family connections and were particularly close to their mothers although also close to their fathers. Grandparents played a significant role in their lives and their relationships with siblings were often positive but did fluctuate. Reasons for closeness centred around trust. Lack of availability due to work was a key contributor to children feeling less close to a family member. The children were involved in a wide range of structured activities after school and at the weekend, This was usually balanced with free time although some ??hurried?? children had frenetic lifestyles. Involvement in unstructured activities such as free play was particularly associated with time with friends and choice. Friendship was characterised by sharing and trust. On the other hand, bullying by peers had been experienced by many of the children and almost all were conscious of the danger of becoming bullied. The wider issues of work-family balance and its impact on children, the predominance of bullying and children??s right to be heard are reflected upon. 相似文献
38.
有越来越多的医生选择学习在线课程来进行继续医学教育,但却很少有严格的评估方法来确定在线继续医学教育活动的效果.鉴于此,美国阿拉巴马大学医学院继续医学教育部的研究人员进行了相关研究.应用时间序列设计的方法,来比较完成了继续医学教育网站提供的任意30分钟在线继续医学教育课程的医生在教育活动前后其知识、态度和自我报告的在临床实践中诊疗行为的变化. 相似文献
39.
Rea IM McKeown PP McMaster D Young IS Patterson C Savage MJ Belton C Marchegiani F Olivieri F Bonafe M Franceschi C 《Experimental gerontology》2004,39(4):629-635
BACKGROUND: PON1, an arylesterase, associated with high density lipoprotein (HDL), protects low density lipoprotein (LDL) against oxidative modification. Common polymorphisms PON1 55 (L/M) and 192 (Q/R) in the PON1 gene associate with atherosclerosis and heart disease. Because long-lived people seem protected from premature vascular death, we conducted a pooled statistical analysis to assess any association between these polymorphisms and longevity in a large combined group of Italian centenarians and octo/nonagenarians from Northern Ireland (NI). MATERIALS AND METHODS: Separated DNA was available from 1479 subjects from Italy and Northern Ireland (NI). In Italy 308 centenarians (males 67, females 241, mean age 100.8, SD2.1 years) and 579 young controls (males 347, females 232, mean age 40.7, SD 12.7 years) were included in the study. In NI, 296 octo/nonagenarians (males 92, females 204, mean age 89.8, SD 5.7 years) and 296 young sex-matched subjects (mean age 13.0, SD 1.4 years) had available DNA. PON1 55 (L/M) and 192 (Q/R) polymorphisms were studied using a PCR-RFLP approach. RESULTS: There was a significant difference in PON1 192 genotypes in Italian centenarians compared to younger controls (X(2)= 6.8, df = 2 p= 0.03) and a similar but non significant trend between octo/nonagenarian and young subjects in NI (X(2) = 4.0, df=2, p=0.14). Using logistic regression analysis on the combined Italian and Irish datasets, there was a small survival advantage for centenarian and octo/nonagenarian subjects who were heterozygous for PON1 192 R allele, (OR 1.3, CI 1-1.6; p=0.04 with a stepwise increase for RR homozygous subjects (OR 1.7, CI 1.1-2.6; p = 0.02) compared to QQ subjects. Comparing R and Q alleles there was a survival advantage for octo/nonagenarian/centenarian subjects who carried the R allele (OR 1.3, CI 1.1-1.5; p = 0.007) but there was no sex-specific effect p =0.77) LL, LM and MM genotypes of PON 55 polymorphisms showed similar frequencies in Italy (39.9, 47.0, 13.1%) and Ireland (39.5, 48.6, 11.9%) with no age or sex-related differences. The PON1 192R/Q and PON55L/M loci were in strong linkage disequilibrium with a Lewontin's D' coefficient -0.928 (elderly) and -0.965 (young). There was a significant difference in haplotype frequency of these linked loci in older compared to younger subjects (Likelihood Ratio X(2) = 9.60, df = 3, p= 0.02). CONCLUSION: These data suggest a modest association between the 192R allele and longevity in two very elderly populations in two European countries. Being homozygous for 192 RR further enhances survival advantage but this effect was not found to be sex specific. This finding is of interest because the 192R allele has previously been associated with increased risk of coronary heart disease. On the other hand, the 192R allele shows higher enzymatic activity, using paraoxon as substrate, and we postulate that its role in the metabolism of potentially toxic chemicals or other metabolic pathways may be important in survival to very old age. 相似文献
40.
Importance of monoamine oxidase A in the bioactivation of neurotoxic analogs of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. 总被引:2,自引:1,他引:2
R E Heikkila M V Kindt P K Sonsalla A Giovanni S K Youngster K A McKeown T P Singer 《Proceedings of the National Academy of Sciences of the United States of America》1988,85(16):6172-6176
1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is a potent dopaminergic neurotoxin that causes biochemical, pharmacological, and pathological deficits in experimental animals similar to those seen in human parkinsonian patients. All of the deficits can be prevented by treating mice with selective inhibitors of monoamine oxidase B (MAO-B), including deprenyl, prior to MPTP administration. We now report that the dopaminergic neurotoxicity of two potent MPTP analogs, namely the 2'-methyl and 2'-ethyl derivatives (2'-MeMPTP and 2'-EtMPTP), cannot be prevented by deprenyl pretreatment. However, the neurotoxicity of these two analogs can be prevented by pretreatment with a combination of deprenyl and the selective MAO-A inhibitor clorgyline at doses that are sufficient to almost completely inhibit both MAO-B and MAO-A activities. Moreover, the neurotoxicity of 2'-EtMPTP (but not of 2'-MeMPTP and MPTP) can be significantly attenuated by clorgyline alone. There was a parallel between the capacity of the MAO inhibitors to decrease the brain content of the pyridinium species after administration of the tetrahydropyridines and the capacity of the MAO inhibitors to protect against the neurotoxic action of the tetrahydropyridines. The data support the conclusion that both 2'-MeMPTP and 2'-EtMPTP are bioactivated to pyridinium species to a significant extent by MAO-A. Further, it appears that the formation of the pyridinium species plays an important role in the neurotoxic process. 相似文献