全文获取类型
收费全文 | 467篇 |
免费 | 53篇 |
专业分类
520篇 |
出版年
2021年 | 7篇 |
2020年 | 5篇 |
2018年 | 4篇 |
2016年 | 9篇 |
2015年 | 22篇 |
2014年 | 26篇 |
2013年 | 23篇 |
2012年 | 19篇 |
2011年 | 27篇 |
2010年 | 22篇 |
2009年 | 11篇 |
2008年 | 18篇 |
2007年 | 21篇 |
2006年 | 21篇 |
2005年 | 20篇 |
2004年 | 14篇 |
2003年 | 19篇 |
2002年 | 18篇 |
2001年 | 10篇 |
2000年 | 16篇 |
1999年 | 12篇 |
1998年 | 6篇 |
1997年 | 8篇 |
1996年 | 6篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 7篇 |
1992年 | 10篇 |
1991年 | 7篇 |
1990年 | 6篇 |
1989年 | 10篇 |
1988年 | 6篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1984年 | 4篇 |
1981年 | 3篇 |
1980年 | 6篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 5篇 |
1973年 | 4篇 |
1970年 | 3篇 |
1969年 | 3篇 |
1968年 | 4篇 |
1965年 | 4篇 |
1962年 | 3篇 |
1956年 | 4篇 |
1947年 | 3篇 |
排序方式: 共有520条查询结果,搜索用时 15 毫秒
11.
Signal transduction and cellular radiation responses 总被引:13,自引:0,他引:13
12.
13.
Francesco Barone-Adesi Jennifer E. Dent David Dajnak Sean Beevers H Ross Anderson Frank J. Kelly Derek G. Cook Peter H. Whincup 《PloS one》2015,10(11)
Background
There is widespread concern about the possible health effects of traffic-related air pollution. Nitrogen dioxide (NO2) is a convenient marker of primary pollution. We investigated the associations between lung function and current residential exposure to a range of air pollutants (particularly NO2, NO, NOx and particulate matter) in London children. Moreover, we placed the results for NO2 in context with a meta-analysis of published estimates of the association.Methods and Findings
Associations between primary traffic pollutants and lung function were investigated in 4884 children aged 9–10 years who participated in the Child Heart and Health Study in England (CHASE). A systematic literature search identified 13 studies eligible for inclusion in a meta-analysis. We combined results from the meta-analysis with the distribution of the values of FEV1 in CHASE to estimate the prevalence of children with abnormal lung function (FEV1<80% of predicted value) expected under different scenarios of NO2 exposure. In CHASE, there were non-significant inverse associations between all pollutants except ozone and both FEV1 and FVC. In the meta-analysis, a 10 μg/m3 increase in NO2 was associated with an 8 ml lower FEV1 (95% CI: -14 to -1 ml; p: 0.016). The observed effect was not modified by a reported asthma diagnosis. On the basis of these results, a 10 μg/m3 increase in NO2 level would translate into a 7% (95% CI: 4% to 12%) increase of the prevalence of children with abnormal lung function.Conclusions
Exposure to traffic pollution may cause a small overall reduction in lung function and increase the prevalence of children with clinically relevant declines in lung function. 相似文献14.
Clones of human ribosomal DNA containing the complete 18 S-rRNA and 28 S-rRNA genes. Characterization, a detailed map of the human ribosomal transcription unit and diversity among clones. 总被引:12,自引:1,他引:12 下载免费PDF全文
B E Maden C L Dent T E Farrell J Garde F S McCallum J A Wakeman 《The Biochemical journal》1987,246(2):519-527
15.
Dent AE Bergmann-Leitner ES Wilson DW Tisch DJ Kimmel R Vulule J Sumba PO Beeson JG Angov E Moormann AM Kazura JW 《PloS one》2008,3(10):e3557
Background
Antibodies that impair Plasmodium falciparum merozoite invasion and intraerythrocytic development are one of several mechanisms that mediate naturally acquired immunity to malaria. Attempts to correlate anti-malaria antibodies with risk of infection and morbidity have yielded inconsistent results. Growth inhibition assays (GIA) offer a convenient method to quantify functional antibody activity against blood stage malaria.Methods
A treatment-time-to-infection study was conducted over 12-weeks in a malaria holoendemic area of Kenya. Plasma collected from healthy individuals (98 children and 99 adults) before artemether-lumefantrine treatment was tested by GIA in three separate laboratories.Results
Median GIA levels varied with P. falciparum line (D10, 8.8%; 3D7, 34.9%; FVO, 51.4% inhibition). The magnitude of growth inhibition decreased with age in all P. falciparum lines tested with the highest median levels among children <4 years compared to adults (e.g. 3D7, 45.4% vs. 30.0% respectively, p = 0.0003). Time-to-infection measured by weekly blood smears was significantly associated with level of GIA controlling for age. Upper quartile inhibition activity was associated with less risk of infection compared to individuals with lower levels (e.g. 3D7, hazard ratio = 1.535, 95% CI = 1.012–2.329; p = 0.0438). Various GIA methodologies had little effect on measured parasite growth inhibition.Conclusion
Plasma antibody-mediated growth inhibition of blood stage P. falciparum decreases with age in residents of a malaria holoendemic area. Growth inhibition assay may be a useful surrogate of protection against infection when outcome is controlled for age. 相似文献16.
Melissa R. Dent Paramjit S. Tappia Naranjan S. Dhalla 《Journal of cellular physiology》2011,226(1):181-186
This study was undertaken to determine alterations in the β‐adrenoceptor (β‐AR) signaling system in male and female rats at 4 weeks after the induction of arteriovenous (AV) fistula or shunt. AV shunt produced a greater degree of cardiac hypertrophy and larger increase in cardiac output in male than in female animals. Increases in plasma levels of norepinephrine and epinephrine (EPI) due to AV shunt were also higher in male than females. While no difference in the β1‐AR affinity was seen in males and females, AV shunt induced increase in β1‐AR density in female rats was higher than that in males. Furthermore, no changes in basal adenylyl cyclase (AC) V/VI mRNA levels were seen; however, the increase in EPI‐stimulated AC activities was greater in AV shunt females than in males. AV shunt decreased myocardial β1‐AR mRNA level in male rats and increased β2‐AR mRNA level in female hearts; an increase in Gi‐protein mRNA was detected only in male hearts. Although GRK2 gene expression was increased in both sexes, an increase in GRK3 mRNA was seen only in AV shunt female rats. β‐arrestin1 mRNA was elevated in females whereas β‐arrestin 2 gene expression was increased in both male and female AV shunt rats. While these data demonstrate gender associated differences in various components of the β‐AR system in cardiac hypertrophy due to AV shunt, only higher levels of plasma catecholamines may account for the greater increase in cardiac output and higher degree of cardiac hypertrophy in males. J. Cell. Physiol. 226: 181–186, 2010. © 2010 Wiley‐Liss, Inc. 相似文献
17.
18.
Urszula Polak Calley Hirsch Sherman Ku Joel Gottesfeld Sharon Y.R. Dent Marek Napierala 《Journal of visualized experiments : JoVE》2012,(60)
Herein we present a protocol of reprogramming human adult fibroblasts into human induced pluripotent stem cells (hiPSC) using retroviral vectors encoding Oct3/4, Sox2, Klf4 and c-myc (OSKM) in the presence of sodium butyrate 1-3. We used this method to reprogram late passage (>p10) human adult fibroblasts derived from Friedreich''s ataxia patient (GM03665, Coriell Repository). The reprogramming approach includes highly efficient transduction protocol using repetitive centrifugation of fibroblasts in the presence of virus-containing media. The reprogrammed hiPSC colonies were identified using live immunostaining for Tra-1-81, a surface marker of pluripotent cells, separated from non-reprogrammed fibroblasts and manually passaged 4,5. These hiPSC were then transferred to Matrigel plates and grown in feeder-free conditions, directly from the reprogramming plate. Starting from the first passage, hiPSC colonies demonstrate characteristic hES-like morphology. Using this protocol more than 70% of selected colonies can be successfully expanded and established into cell lines. The established hiPSC lines displayed characteristic pluripotency markers including surface markers TRA-1-60 and SSEA-4, as well as nuclear markers Oct3/4, Sox2 and Nanog.
The protocol presented here has been established and tested using adult fibroblasts obtained from Friedreich''s ataxia patients and control individuals 6, human newborn fibroblasts, as well as human keratinocytes. 相似文献
19.
20.
Huck BR Llamas L Robarge MJ Dent TC Song J Hodnick WF Crumrine C Stricker-Krongrad A Harrington J Brunden KR Bennani YL 《Bioorganic & medicinal chemistry letters》2006,16(15):4130-4134
5-HT2C agonists have shown efficacy in limiting food consumption and thus may serve as an important drug class in combating obesity. We describe the design and synthesis of a novel tricyclic single-nitrogen scaffold that was used to produce 5-HT2C agonists. SAR was developed around this chemotype and compounds were identified that were potent (Ki<15 nM) and selective relative to other 5-HT2 receptors. The most promising compound displayed a good pharmacokinetic profile in multiple animal species, and was efficacious in an acute feeding study in rats. 相似文献