全文获取类型
收费全文 | 502篇 |
免费 | 42篇 |
专业分类
544篇 |
出版年
2023年 | 5篇 |
2022年 | 5篇 |
2021年 | 15篇 |
2020年 | 6篇 |
2019年 | 8篇 |
2018年 | 5篇 |
2017年 | 7篇 |
2016年 | 16篇 |
2015年 | 27篇 |
2014年 | 38篇 |
2013年 | 17篇 |
2012年 | 42篇 |
2011年 | 35篇 |
2010年 | 31篇 |
2009年 | 26篇 |
2008年 | 24篇 |
2007年 | 37篇 |
2006年 | 37篇 |
2005年 | 25篇 |
2004年 | 22篇 |
2003年 | 34篇 |
2002年 | 22篇 |
2001年 | 6篇 |
2000年 | 3篇 |
1999年 | 7篇 |
1998年 | 3篇 |
1997年 | 5篇 |
1996年 | 7篇 |
1995年 | 6篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1978年 | 1篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1961年 | 1篇 |
1950年 | 1篇 |
1945年 | 1篇 |
1937年 | 1篇 |
排序方式: 共有544条查询结果,搜索用时 15 毫秒
81.
Joaquín A. Blaya Sonya S. Shin Martin Yagui Carmen Contreras Peter Cegielski Gloria Yale Carmen Suarez Luis Asencios Jaime Bayona Jihoon Kim Hamish S. F. Fraser 《PloS one》2014,9(4)
Background
Lost, delayed or incorrect laboratory results are associated with delays in initiating treatment. Delays in treatment for Multi-Drug Resistant Tuberculosis (MDR-TB) can worsen patient outcomes and increase transmission. The objective of this study was to evaluate the impact of a laboratory information system in reducing delays and the time for MDR-TB patients to culture convert (stop transmitting).Methods
Setting: 78 primary Health Centers (HCs) in Lima, Peru. Participants lived within the catchment area of participating HCs and had at least one MDR-TB risk factor. The study design was a cluster randomized controlled trial with baseline data. The intervention was the e-Chasqui web-based laboratory information system. Main outcome measures were: times to communicate a result; to start or change a patient''s treatment; and for that patient to culture convert.Results
1671 patients were enrolled. Intervention HCs took significantly less time to receive drug susceptibility test (DST) (median 11 vs. 17 days, Hazard Ratio 0.67 [0.62–0.72]) and culture (5 vs. 8 days, 0.68 [0.65–0.72]) results. The time to treatment was not significantly different, but patients in intervention HCs took 16 days (20%) less time to culture convert (p = 0.047).Conclusions
The eChasqui system reduced the time to communicate results between laboratories and HCs and time to culture conversion. It is now used in over 259 HCs covering 4.1 million people. This is the first randomized controlled trial of a laboratory information system in a developing country for any disease and the only study worldwide to show clinical impact of such a system.Trial Registration
ClinicalTrials.gov NCT01201941相似文献82.
83.
LaTonya D. Williams Nilesh Amatya Anju Bansal Steffanie Sabbaj Sonya L. Heath Irini Sereti Paul A. Goepfert 《Journal of virology》2014,88(17):10259-10263
Interleukin-21 (IL-21) can be produced by CD8 T cells from HIV-1-infected individuals and those with autoimmune disease, but the mechanism remains poorly understood. Here we demonstrate that IL-21-producing CD8 T cells are not associated with CD4 depletion and are absent in patients with idiopathic CD4 lymphocytopenia. Instead, IL-21 production by CD8 T cells was associated with high levels of activation, suggesting that these cells emerge as a consequence of excessive chronic immune activation rather than CD4 lymphopenia. 相似文献
84.
85.
A postmitotic role for Isl-class LIM homeodomain proteins in the assignment of visceral spinal motor neuron identity 总被引:5,自引:0,他引:5
LIM homeobox genes have a prominent role in the regulation of neuronal subtype identity and distinguish motor neuron subclasses in the embryonic spinal cord. We have investigated the role of Isl-class LIM homeodomain proteins in motor neuron diversification using mouse genetic methods. All spinal motor neuron subtypes initially express both Isl1 and Isl2, but Isl2 is rapidly downregulated by visceral motor neurons. Mouse embryos lacking Isl2 function exhibit defects in the migration and axonal projections of thoracic level motor neurons that appear to reflect a cell-autonomous switch from visceral to somatic motor neuron character. Additional genetic mutations that reduce or eliminate both Isl1 and Isl2 activity result in more pronounced defects in visceral motor neuron generation and erode somatic motor neuron character. Thus, an early phase of high Isl expression and activity in newly generated motor neurons permits the diversification of visceral and somatic motor neuron subtypes in the developing spinal cord. 相似文献
86.
A novel founder mutation in the RNASEL gene, 471delAAAG,is associated with prostate cancer in Ashkenazi Jews 总被引:7,自引:0,他引:7
Rennert H Bercovich D Hubert A Abeliovich D Rozovsky U Bar-Shira A Soloviov S Schreiber L Matzkin H Rennert G Kadouri L Peretz T Yaron Y Orr-Urtreger A 《American journal of human genetics》2002,71(4):981-984
HPC1/RNASEL was recently identified as a candidate gene for hereditary prostate cancer. We identified a novel founder frameshift mutation in RNASEL, 471delAAAG, in Ashkenazi Jews. The mutation frequency in the Ashkenazi population, estimated on the basis of the frequency in 150 healthy young women, was 4% (95% confidence interval [CI] 1.9%-8.4%). Among Ashkenazi Jews, the mutation frequency was higher in patients with prostate cancer (PRCA) than in elderly male control individuals (6.9% vs. 2.4%; odds ratio = 3.0; 95% CI 0.6-15.3; P=.17). 471delAAAG was not detected in the 134 non-Ashkenazi patients with PRCA and control individuals tested. The median age at PRCA diagnosis did not differ significantly between the Ashkenazi carriers and noncarriers included in our study. However, carriers received diagnoses at a significantly earlier age, compared with patients with PRCA who were registered in the Israeli National Cancer Registry (65 vs. 74.4 years, respectively; P<.001). When we examined two brothers with PRCA, we found a heterozygous 471delAAAG mutation in one and a homozygous mutation in the other. Loss of heterozygosity was demonstrated in the tumor of the heterozygous sib. Taken together, these data suggest that the 471delAAAG null mutation is associated with PRCA in Ashkenazi men. However, additional studies are required to determine whether this mutation confers increased risk for PRCA in this population. 相似文献
87.
88.
89.
90.
Integrating phylogenetic and ecological distances reveals new insights into parasite host specificity 下载免费PDF全文
The range of hosts a pathogen infects (host specificity) is a key element of disease risk that may be influenced by both shared phylogenetic history and shared ecological attributes of prospective hosts. Phylospecificity indices quantify host specificity in terms of host relatedness, but can fail to capture ecological attributes that increase susceptibility. For instance, similarity in habitat niche may expose phylogenetically unrelated host species to similar pathogen assemblages. Using a recently proposed method that integrates multiple distances, we assess the relative contributions of host phylogenetic and functional distances to pathogen host specificity (functional–phylogenetic host specificity). We apply this index to a data set of avian malaria parasite (Plasmodium and Haemoproteus spp.) infections from Melanesian birds to show that multihost parasites generally use hosts that are closely related, not hosts with similar habitat niches. We also show that host community phylogenetic ß‐diversity (Pßd) predicts parasite Pßd and that individual host species carry phylogenetically clustered Haemoproteus parasite assemblages. Our findings were robust to phylogenetic uncertainty, and suggest that phylogenetic ancestry of both hosts and parasites plays important roles in driving avian malaria host specificity and community assembly. However, restricting host specificity analyses to either recent or historical timescales identified notable exceptions, including a ‘habitat specialist’ parasite that infects a diversity of unrelated host species with similar habitat niches. This work highlights that integrating ecological and phylogenetic distances provides a powerful approach to better understand drivers of pathogen host specificity and community assembly. 相似文献