全文获取类型
收费全文 | 14582篇 |
免费 | 1114篇 |
国内免费 | 52篇 |
专业分类
耳鼻咽喉 | 108篇 |
儿科学 | 355篇 |
妇产科学 | 359篇 |
基础医学 | 1835篇 |
口腔科学 | 372篇 |
临床医学 | 1534篇 |
内科学 | 3241篇 |
皮肤病学 | 250篇 |
神经病学 | 1398篇 |
特种医学 | 647篇 |
外科学 | 2098篇 |
综合类 | 318篇 |
一般理论 | 11篇 |
预防医学 | 1062篇 |
眼科学 | 307篇 |
药学 | 940篇 |
中国医学 | 10篇 |
肿瘤学 | 903篇 |
出版年
2023年 | 66篇 |
2022年 | 90篇 |
2021年 | 243篇 |
2020年 | 140篇 |
2019年 | 205篇 |
2018年 | 293篇 |
2017年 | 184篇 |
2016年 | 201篇 |
2015年 | 229篇 |
2014年 | 363篇 |
2013年 | 754篇 |
2012年 | 845篇 |
2011年 | 972篇 |
2010年 | 522篇 |
2009年 | 483篇 |
2008年 | 866篇 |
2007年 | 953篇 |
2006年 | 933篇 |
2005年 | 911篇 |
2004年 | 804篇 |
2003年 | 798篇 |
2002年 | 783篇 |
2001年 | 174篇 |
2000年 | 161篇 |
1999年 | 177篇 |
1998年 | 199篇 |
1997年 | 176篇 |
1996年 | 166篇 |
1995年 | 152篇 |
1994年 | 135篇 |
1993年 | 134篇 |
1992年 | 151篇 |
1991年 | 135篇 |
1990年 | 99篇 |
1989年 | 133篇 |
1988年 | 144篇 |
1987年 | 113篇 |
1986年 | 132篇 |
1985年 | 149篇 |
1984年 | 168篇 |
1983年 | 151篇 |
1982年 | 136篇 |
1981年 | 127篇 |
1980年 | 134篇 |
1979年 | 66篇 |
1978年 | 72篇 |
1977年 | 70篇 |
1976年 | 79篇 |
1974年 | 66篇 |
1973年 | 48篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Bartholdy C Stryhn A Hansen NJ Buus S Thomsen AR 《European journal of immunology》2003,33(7):1941-1948
DNA vaccination is an efficient way to induce CD8+ T cell memory, but it is still unclear to what extent such memory responses afford protection in vivo. To study this, we induced CD8+ memory responses directed towards defined viral epitopes, using DNA vaccines encoding immunodominant MHC class I-restricted epitopes of lymphocytic choriomeningitis virus covalently linked to beta2-microglobulin. This vaccine construct primed for a stronger recall response than did a more conventional minigene construct. Despite this, vaccinated mice were only protected against systemic infection whereas protection against the consequences of peripheral challenge was limited. Phenotypic analysis revealed that DNA vaccine-primed CD8+ T cells in uninfected mice differed from virus-primed CD8+ T cells particularly regarding expression of very-late antigen (VLA)-4, an adhesion molecule important for targeting T cells to inflammatory sites. Thus, our DNA vaccine induces a long-lived memory CD8+ T cell population that provides efficient protection against high-dose systemic infection. However, viral replication in solid non-lymphoid organs is not curtailed sufficiently fast to prevent significant virus-induced inflammation. Our results suggest that this is due to qualitative limitations of the primed CD8+ T cells. 相似文献
72.
Oxidative stress is extensive in Alzheimer disease (AD) brain. Amyloid beta-peptide (1-42) has been shown to induce oxidative stress and neurotoxicity in vitro and in vivo. Genetic mutations that result in increased production of Abeta1-42 from amyloid precursor protein are associated with an early onset and accelerated pathology of AD. Consequently, Abeta1-42 has been proposed to play a central role in the pathogenesis of AD as a mediator of oxidative stress. In this review, we discuss the role of Abeta1-42 in the lipid peroxidation and protein oxidation evident in AD brain and the implications of such oxidative stress for the function of various proteins that we have identified as specifically oxidized in AD brain compared to control, using proteomics methods. Additionally, we discuss the critical role of methionine 35 in the oxidative stress and neurotoxic properties exhibited by Abeta1-42. 相似文献
73.
Allan L Wolfsohn Derek Y F So Kwan Chan Ian Burwash Paul Hendry John P Veinot Marino Labinaz 《Cardiovascular pathology》2005,14(4):214-218
We present two cases of a thrombus in the ascending aorta causing an acute myocardial infarction (AMI) and review the 10 other cases previously reported in the literature. This life-threatening condition appears to be more common in female smokers in their fifth decade. Suspicion should be raised in individuals at low risk for atherosclerotic disease with coronary angiographic findings not in keeping with the clinical presentation. The diagnosis may be obtained by transesophageal echocardiography, and we generally recommend surgical thrombectomy. 相似文献
74.
Fein AJ Plotnikoff RC Wild TC Spence JC 《International journal of behavioral medicine》2004,11(3):135-142
The examination of physical environments to explain and promote physical activity is an important yet under-investigated area
of research inquiry. This study explored relationships between the perceived availability of physical environmental resources
and the perceived importance of these resources in relation to physical activity levels amongst youth. A self-report questionnaire
was completed by 610 students (mean age = 15.5 years old; 62% female participants) from four high schools (grades 9-12) in
rural Alberta, Canada. Perceived physical environment constructs explained 5% of the variance in physical activity, with home,
neighborhood, and school as significant domains. Perceived importance constructs explained 8% of the variance in physical
activity with school context showing the only significant relationship with physical activity. A hierarchical regression analysis
entered sex, grade, self-efficacy, peer, family and physical education teacher relationships, as the first block and eight
environmental constructs as the second block. The first block variables accounted for 22% of the variance and environmental
constructs accounted for an added 4% of the variance in physical activity. Perceived importance of the school environment
was the only environment variable significantly associated with physical activity (β = .14; p < .05) after taking into account
the impact of these traditional predictors. These findings reinforce the need to provide and support school physical environments
related to physical activity. 相似文献
75.
A 72-year-old male painter, who complained of his "lungs burning" for 2 weeks, died suddenly. Autopsy examination revealed severe coronary atherosclerosis with plaque rupture as the cause of death. Examination of the lungs revealed emphysema, interstitial fibrosis, and multinucleated giant cells with intra- and extracellular brown-black, crystalline, polarizable foreign material. Energy-dispersive X-ray microanalysis showed the material to contain titanium, aluminum, silicon, and iron. An increased incidence of respiratory disease has been reported in professional painters. Titanium is widely used as a pigment in the manufacturing of commercial paints. Cases of pneumoconiosis and alveolar proteinosis have been described in painters in which analysis of lung tissue revealed increased levels of titanium. This case is presented as an example of a rarely reported phenomenon, which may have clinical implications for evaluation and management of lung disease in painters. 相似文献
76.
77.
Disruption of the gene homologous to mammalian Nramp1 in Mycobacterium tuberculosis does not affect virulence in mice 下载免费PDF全文
Boechat N Lagier-Roger B Petit S Bordat Y Rauzier J Hance AJ Gicquel B Reyrat JM 《Infection and immunity》2002,70(8):4124-4131
Natural-resistance-associated macrophage protein 1 (Nramp1) is a divalent cation transporter belonging to a family of transporter proteins highly conserved in eukaryotes and prokaryotes. Mammalian and bacterial transporters may compete for essential metal ions during mycobacterial infections. The mycobacterial Nramp homolog may therefore be involved in Mycobacterium tuberculosis virulence. Here, we investigated this possibility by inactivating the M. tuberculosis Nramp1 gene (Mramp) by allelic exchange mutagenesis. Disruption of Mramp did not affect the extracellular growth of bacteria under standard conditions. However, the Mramp mutation was associated with growth impairment under conditions of limited iron availability. The Mramp mutant displayed no impairment of growth or survival in macrophages derived from mouse bone marrow or in Nramp1(+/+) and Nramp1(-/-) congenic murine macrophage cell lines. Following intravenous challenge in BALB/c mice, counts of parental and Mramp mutant strains were similar in the lungs and spleens of the animals at all time points studied. These results indicate that Mramp does not contribute to the virulence of M. tuberculosis in mice. 相似文献
78.
Atsuko Fujimoto Joseph W. Towner Allan J. Ebbin Emily J. Kahlstrom Miriam G. Wilson 《Journal of medical genetics》1974,11(3):287-291
A boy with unusual facial appearance and mental retardation was found to have duplication for the distal half of the long arm of chromosome No. 15 and possibly deficiency for the distal end of the long arm of No. 21. The chromosome abnormality was inherited from his mother, who had a translocation involving chromosomes Nos. 15 and 21. Giemsa-banding localized the break point in chromosome No. 15 just distal to the intense band at the midportion of the long arm. The break point in chromosome No. 21 appeared to be at the distal end of the long arm. The difficulty encountered in cytogenetic analysis of the propositus with conventional staining, the importance of chromosome analysis of the parents, and the application of differential staining techniques are also presented. 相似文献
79.
In vitro studies with recombinant Plasmodium falciparum apical membrane antigen 1 (AMA1): production and activity of an AMA1 vaccine and generation of a multiallelic response 总被引:5,自引:0,他引:5 下载免费PDF全文
Kennedy MC Wang J Zhang Y Miles AP Chitsaz F Saul A Long CA Miller LH Stowers AW 《Infection and immunity》2002,70(12):6948-6960
Apical membrane antigen 1 (AMA1) is regarded as a leading malaria blood-stage vaccine candidate. While the overall structure of AMA1 is conserved in Plasmodium spp., numerous AMA1 allelic variants of P. falciparum have been described. The effect of AMA1 allelic diversity on the ability of a recombinant AMA1 vaccine to protect against human infection by different P. falciparum strains is unknown. We characterize two allelic forms of AMA1 that were both produced in Pichia pastoris at a sufficient economy of scale to be usable for clinical vaccine studies. Both proteins were used to immunize rabbits, singly and in combination, in order to evaluate their immunogenicity and the ability of elicited antibodies to block the growth of different P. falciparum clones. Both antigens, when used alone, elicited high homologous anti-AMA1 titers, with reduced strain cross-reactivity. Similarly, sera from rabbits immunized with a single antigen were capable of blocking the growth of homologous parasite strains at levels theoretically sufficient to clear parasite infections. However, heterologous inhibition was significantly reduced, providing experimental evidence that AMA1 allelic diversity is a result of immune pressure. Encouragingly, rabbits immunized with a combination of both antigens exhibited titers and levels of parasite inhibition as good as those of the single-antigen-immunized rabbits for each of the homologous parasite lines, and consequently exhibited a broadening of allelic diversity coverage. 相似文献
80.
Experimental infection of cattle of different ages with infectious bovine rhinotracheitis virus (Strichen strain) 总被引:1,自引:0,他引:1
The clinical signs and pathological lesions which developed in various ages of cattle experimentally infected intranasally with the "Strichen" strain of IBR virus were similar to, but generally milder than, those of the field disease. The clinical signs were most severe 4 days after infection and had almost wholly regressed after 12 days. Serum neutralizing antibodies were detected in every animal. Virus was isolated from nasal and ocular swabs for up to 13 days and 10 days, respectively, after infection. The clinical signs and the pathological lesions were more severe in the younger animals. 相似文献