全文获取类型
收费全文 | 2387篇 |
免费 | 185篇 |
国内免费 | 9篇 |
专业分类
耳鼻咽喉 | 4篇 |
儿科学 | 64篇 |
妇产科学 | 111篇 |
基础医学 | 290篇 |
口腔科学 | 28篇 |
临床医学 | 188篇 |
内科学 | 667篇 |
皮肤病学 | 34篇 |
神经病学 | 160篇 |
特种医学 | 130篇 |
外科学 | 201篇 |
综合类 | 29篇 |
一般理论 | 3篇 |
预防医学 | 243篇 |
眼科学 | 21篇 |
药学 | 114篇 |
肿瘤学 | 294篇 |
出版年
2021年 | 32篇 |
2020年 | 16篇 |
2019年 | 38篇 |
2018年 | 40篇 |
2017年 | 27篇 |
2016年 | 30篇 |
2015年 | 35篇 |
2014年 | 54篇 |
2013年 | 61篇 |
2012年 | 122篇 |
2011年 | 153篇 |
2010年 | 58篇 |
2009年 | 51篇 |
2008年 | 132篇 |
2007年 | 137篇 |
2006年 | 108篇 |
2005年 | 94篇 |
2004年 | 103篇 |
2003年 | 90篇 |
2002年 | 81篇 |
2001年 | 70篇 |
2000年 | 64篇 |
1999年 | 64篇 |
1998年 | 30篇 |
1997年 | 28篇 |
1996年 | 18篇 |
1995年 | 13篇 |
1994年 | 14篇 |
1993年 | 13篇 |
1992年 | 57篇 |
1991年 | 55篇 |
1990年 | 54篇 |
1989年 | 49篇 |
1988年 | 42篇 |
1987年 | 56篇 |
1986年 | 52篇 |
1985年 | 40篇 |
1984年 | 43篇 |
1983年 | 36篇 |
1982年 | 23篇 |
1981年 | 15篇 |
1980年 | 13篇 |
1979年 | 21篇 |
1978年 | 15篇 |
1977年 | 16篇 |
1976年 | 17篇 |
1974年 | 27篇 |
1973年 | 21篇 |
1972年 | 15篇 |
1971年 | 11篇 |
排序方式: 共有2581条查询结果,搜索用时 15 毫秒
991.
H.-M. A. Schmidt S. Andres C. Nilsson Z. Kovach N. O. Kaakoush L. Engstrand K.-L. Goh K. M. Fock D. Forman H. Mitchell 《European journal of clinical microbiology & infectious diseases》2010,29(4):439-451
Helicobacter pylori-related disease is at least partially attributable to the genotype of the infecting strain, particularly the presence of
specific virulence factors. We investigated the prevalence of a novel combination of H. pylori virulence factors, including the cag pathogenicity island (PAI), and their association with severe disease in isolates from the three major ethnicities in Malaysia
and Singapore, and evaluated whether the cag PAI was intact and functional in vitro. Polymerase chain reaction (PCR) was used to detect dupA, cagA, cagE, cagT, cagL and babA, and to type vacA, the EPIYA motifs, HP0521 alleles and oipA ON status in 159 H. pylori clinical isolates. Twenty-two strains were investigated for IL-8 induction and CagA translocation in vitro. The prevalence
of cagA, cagE, cagL, cagT, babA, oipA ON and vacA s1 and i1 was >85%, irrespective of the disease state or ethnicity. The prevalence of dupA and the predominant HP0521 allele and EPIYA motif varied significantly with ethnicity (p < 0.05). A high prevalence of an intact cag PAI was found in all ethnic groups; however, no association was observed between any virulence factor and disease state.
The novel association between the HP0521 alleles, EPIYA motifs and host ethnicity indicates that further studies to determine
the function of this gene are important. 相似文献
992.
993.
994.
Jennifer A. Wagman Jeffrey H. Samet Debbie M. Cheng Natalia Gnatienko Anita Raj Elena Blokhina Olga Toussova Leah S. Forman Dmitry Lioznov Judith I. Tsui 《AIDS and behavior》2018,22(9):2830-2839
Among persons who inject drugs, women have a higher HIV prevalence (than men) in many settings. Understanding how gender affects risk for infection among HIV-negative, and transmission among HIV-positive people who currently or previously injected drugs is key to designing effective prevention and treatment programs. We analyzed data from 291 persons living with HIV who had ever injected drugs. Participants were drawn from the Russia Alcohol Research Collaboration on HIV/AIDS cohort (2012–2015) to examine associations between female gender and HIV transmission risk. Primary outcomes were sharing drug injecting equipment (e.g., needle/syringes) and condomless sex. Secondary outcomes were alcohol use before sharing drug injecting equipment; before condomless sex; and both sharing drug injecting equipment and condomless sex. Logistic regression models assessed associations between gender and outcomes, controlling for demographics, partner HIV status and use of antiretroviral treatment. Female gender was not significantly associated with sharing drug injecting equipment [aOR?=?1.45, 95% confidence interval (CI) 0.85–2.46, p value?=?0.18] but was associated with condomless sex (aOR?=?1.91, 95% CI 1.12–3.23, p?=?0.02) in adjusted models. Female gender was not significantly associated with any secondary outcomes. Better understanding of risky sex and drug use behaviors among people who currently or previously injected drugs can support the design of effective gender-tailored HIV prevention interventions. 相似文献
995.
Similar clinical benefits from below‐target and target dose enalapril in patients with heart failure in the SOLVD Treatment trial
下载免费PDF全文
![点击此处可从《European journal of heart failure》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Gregg C. Fonarow Javed Butler Deepak L. Bhatt Gerasimos S. Filippatos Prakash Deedwania Daniel E. Forman Michel White Ross D. Fletcher Cherinne Arundel Marc R. Blackman Chris Adamopoulos Ioannis E. Kanonidis Inmaculada B. Aban Kanan Patel Wilbert S. Aronow Richard M. Allman Stefan D. Anker Bertram Pitt Ali Ahmed 《European journal of heart failure》2018,20(2):359-369
996.
997.
998.
The Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the third human-emerged virus of the 21st century from the Coronaviridae family, causing the ongoing coronavirus disease 2019 (COVID-19) pandemic. Due to the high zoonotic potential of coronaviruses, it is critical to unravel their evolutionary history of host species breadth, host-switch potential, adaptation and emergence, to identify viruses posing a pandemic risk in humans. We present here a comprehensive analysis of the composition and codon usage bias of the 82 Orthocoronavirinae members, infecting 47 different avian and mammalian hosts. Our results clearly establish that synonymous codon usage varies widely among viruses, is only weakly dependent on their primary host, and is dominated by mutational bias towards AU-enrichment and by CpG avoidance. Indeed, variation in GC3 explains around 34%, while variation in CpG frequency explains around 14% of total variation in codon usage bias. Further insight on the mutational equilibrium within Orthocoronavirinae revealed that most coronavirus genomes are close to their neutral equilibrium, the exception being the three recently infecting human coronaviruses, which lie further away from the mutational equilibrium than their endemic human coronavirus counterparts. Finally, our results suggest that, while replicating in humans, SARS-CoV-2 is slowly becoming AU-richer, likely until attaining a new mutational equilibrium. 相似文献
999.
1000.
Lisa H. Glassman Anootnara T. Kuster Jena A. Shaw Evan M. Forman Meltem Izzetoglu Alyssa Matteucci James D. Herbert 《Brain imaging and behavior》2017,11(3):797-807
Functional near-infrared (fNIR) spectroscopy is a promising new technology that has demonstrated utility in the study of normal human cognition. We utilized fNIR spectroscopy to examine the effect of social anxiety and performance on hemodynamic activity in the dorsolateral prefrontal cortex (DLPFC). Socially phobic participants and non-clinical participants with varying levels of social anxiety completed a public speaking task in front of a small virtual audience while the DLPFC was being monitored by the fNIR device. The relationship between anxiety and both blood volume (BV) and deoxygenated hemoglobin (Hb) varied significantly as a function of speech performance, such that individuals with low social anxiety who performed well showed an increase in DLPFC activation relative to those who did not perform well. This result suggests that effortful thinking and/or efficient top-down inhibitory control may have been required to complete an impromptu speech task with good performance. In contrast, good performers who were highly socially anxious showed lower DLPFC activation relative to good performers who were low in social anxiety, suggesting autopilot thinking or less-effortful thinking. In poor performers, slight increases in DLPFC activation were observed from low to highly anxious individuals, which may reflect a shift from effortless thinking to heightened self-focused attention. Heightened self-focused attention, poor inhibitory control resulting in excessive fear or anxiety, or low motivation may lower performance. These results suggest that there can be different underlying mechanisms in the brain that affect the level of speech performance in individuals with varying degrees of social anxiety. This study highlights the utility of the fNIR device in the assessment of changes in DLPFC in response to exposure to realistic phobic stimuli, and further supports the potential utility of this technology in the study of the neurophysiology of anxiety disorders. 相似文献