全文获取类型
收费全文 | 563篇 |
免费 | 48篇 |
国内免费 | 2篇 |
出版年
2022年 | 9篇 |
2021年 | 6篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 6篇 |
2017年 | 6篇 |
2016年 | 10篇 |
2015年 | 14篇 |
2014年 | 32篇 |
2013年 | 27篇 |
2012年 | 41篇 |
2011年 | 42篇 |
2010年 | 20篇 |
2009年 | 16篇 |
2008年 | 31篇 |
2007年 | 27篇 |
2006年 | 29篇 |
2005年 | 33篇 |
2004年 | 36篇 |
2003年 | 37篇 |
2002年 | 22篇 |
2001年 | 6篇 |
2000年 | 5篇 |
1998年 | 8篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1994年 | 4篇 |
1993年 | 8篇 |
1992年 | 4篇 |
1991年 | 9篇 |
1989年 | 3篇 |
1988年 | 8篇 |
1987年 | 6篇 |
1986年 | 7篇 |
1985年 | 6篇 |
1984年 | 8篇 |
1983年 | 9篇 |
1982年 | 10篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1970年 | 4篇 |
1969年 | 3篇 |
1968年 | 4篇 |
1967年 | 2篇 |
排序方式: 共有613条查询结果,搜索用时 31 毫秒
81.
Prior to the completion of the Human Genome Project, bioethicists and other academics debated the impact of this new genetic information on medicine, health care, group identification, and peoples’ lives. A major issue is the potential for unintended and intended adverse consequences to groups and individuals. When conducting research in, for instance, American Indian and Alaskan native (AI/AN) populations, political, cultural, religious and historical issues must be considered. Among African Americans, the Tuskegee Syphilis Experiment is a reminder of racism and discrimination in this country. The goal of the current study is to understand reasons for participating, or not, in genetic research such as the HapMap project and other genetic/medical research from the perspective of the Indian American community in Houston, Texas. In this article, we report on a topic central to this discussion among Indian Americans: karma and reincarnation. Both concepts are important beliefs when considering the body and what should happen to it. Karma and reincarnation are also important considerations in participation in medical and genetic research because, according to karma, what is done to the body can affect future existences and the health of future descendants. Such views of genetic and medical research are culturally mediated. Spiritual beliefs about the body, tissue, and fluids and what happens to them when separated from the body can influence ideas about the utility and acceptability of genetic research and thereby affect the recruitment process. Within this community it is understood that genetic and environmental factors contribute to complex diseases such as diabetes, hypertension, and cancer; and acknowledgment of the significance of environmental stressors in the production of disease. A commitment to service, i.e. “betterment of humanity,” karmic beliefs, and targeting environmental stressors could be prominent avenues for public health campaigns in this population. This study suggests that minority status does not automatically indicate unwillingness to participate in genetic or medical research. Indian Americans were not skeptical about the potential benefits of biomedical research in comparison to other ethnic minority communities in the United States. 相似文献
82.
The purpose of a drinking water distribution system is to deliver drinking water to the consumer, preferably with the same quality as when it left the treatment plant. In this context, the maintenance of good microbiological quality is often referred to as biological stability, and the addition of sufficient chlorine residuals is regarded as one way to achieve this. The full-scale drinking water distribution system of Riga (Latvia) was investigated with respect to biological stability in chlorinated drinking water. Flow cytometric (FCM) intact cell concentrations, intracellular adenosine tri-phosphate (ATP), heterotrophic plate counts and residual chlorine measurements were performed to evaluate the drinking water quality and stability at 49 sampling points throughout the distribution network. Cell viability methods were compared and the importance of extracellular ATP measurements was examined as well. FCM intact cell concentrations varied from 5×103 cells mL−1 to 4.66×105 cells mL−1 in the network. While this parameter did not exceed 2.1×104 cells mL−1 in the effluent from any water treatment plant, 50% of all the network samples contained more than 1.06×105 cells mL−1. This indisputably demonstrates biological instability in this particular drinking water distribution system, which was ascribed to a loss of disinfectant residuals and concomitant bacterial growth. The study highlights the potential of using cultivation-independent methods for the assessment of chlorinated water samples. In addition, it underlines the complexity of full-scale drinking water distribution systems, and the resulting challenges to establish the causes of biological instability. 相似文献
83.
Robert B. Lochhead James F. Zachary Luciana Dalla Rosa Ying Ma John H. Weis Ryan M. O’Connell Janis J. Weis 《PloS one》2015,10(8)
MicroRNA-155 has been shown to play a role in immune activation and inflammation, and is suppressed by IL-10, an important anti-inflammatory cytokine. The established involvement of IL-10 in the murine model of Borrelia burgdorferi-induced Lyme arthritis and carditis allowed us to assess the interplay between IL-10 and miR-155 in vivo. As reported previously, Mir155 was highly upregulated in joints from infected severely arthritic B6 Il10-/- mice, but not in mildly arthritic B6 mice. In infected hearts, Mir155 was upregulated in both strains, suggesting a role of miR-155 in Lyme carditis. Using B. burgdorferi-infected B6, Mir155-/-, Il10-/-, and Mir155-/- Il10-/- double-knockout (DKO) mice, we found that anti-inflammatory IL-10 and pro-inflammatory miR-155 have opposite and somewhat compensatory effects on myeloid cell activity, cytokine production, and antibody response. Both IL-10 and miR-155 were required for suppression of Lyme carditis. Infected Mir155-/- mice developed moderate/severe carditis, had higher B. burgdorferi numbers, and had reduced Th1 cytokine expression in hearts. In contrast, while Il10-/- and DKO mice also developed severe carditis, hearts had reduced bacterial numbers and elevated Th1 and innate cytokine expression. Surprisingly, miR-155 had little effect on Lyme arthritis. These results show that antagonistic interplay between IL-10 and miR-155 is required to balance host defense and immune activation in vivo, and this balance is particularly important for suppression of Lyme carditis. These results also highlight tissue-specific differences in Lyme arthritis and carditis pathogenesis, and reveal the importance of IL-10-mediated regulation of miR-155 in maintaining healthy immunity. 相似文献
84.
Johanna Schmitt Janis Antonovics 《Evolution; international journal of organic evolution》1986,40(4):817-829
To determine whether genetic differences in fitness components exist among seeds and seedlings in a natural population, weighed propagules of six parents of Anthoxanthum odoratum from a reciprocal diallel cross were planted into the parental source population, a mown field. Seed families of maternal genotypes differed in germination success, while paternal families showed no detectable differences. Differential germination success could not be attributed to propagule weight. Seed families ranked differently in germination percentage in different blocks. No survivorship differences among parental seed families could be detected. There were significant cross × block × germination and cross × block × survivorship interactions; different crosses performed better or worse in different blocks. In some cases, crosses sired by different fathers within a maternal seed family differed in germination or survivorship, suggesting that natural selection may be capable of discriminating among juvenile genotypes within a maternal family despite the presence of large overall maternal effects. These results indicate that seedling establishment may differ according to genotype and that microsite heterogeneity may maintain genetic variation in juvenile traits in natural plant populations. 相似文献
85.
Johanna Schmitt Janis Antonovics 《Evolution; international journal of organic evolution》1986,40(4):830-836
To investigate the effect of neighbor relatedness in seedling populations, propagules of six Anthoxanthum odoratum parents, produced from a reciprocal diallel cross, were planted into the parental source population, a mown field. The propagules were either surrounded by four unrelated neighbors in a 1 cm square, four sibling neighbors, or no neighbors. About 45% of the emerging seedlings were attacked by aphids (Schizaphis graminum). Aphid infestation significantly reduced seedling survivorship and did not differ with parental genotype or neighbor relatedness; plants without neighbors had a slightly higher infestation risk. Plants without neighbors had lower survivorship than those surrounded by unrelated neighbors although this difference was only significant for plants infested by aphids. When infested by aphids, plants surrounded by siblings had lower survivorship than plants surrounded by non-relatives, suggesting the operation of minority advantage. These results are consistent with the frequency-dependent selection hypothesis for the evolution and maintenance of sexual reproduction. 相似文献
86.
Keith Clay Janis Antonovics 《Evolution; international journal of organic evolution》1985,39(2):335-348
Progeny from chasmogamous (CH) and cleistogamous (CL) flowers of the grass Danthonia spicata were raised in their native habitat and in the greenhouse in order to determine how genetic variation was distributed among families and between CH and CL progeny within families. Twelve quantitative characters were measured on clones from individuals known to have arisen from either CH or CL flowers on a particular plant. Significant genetic variation existed for all characters measured. Most genetic variation was between families and two morphologically similar groups of families were identified. Relatively little genetic variation was found within families (approximately 5% of the total phenotypic variance). In field-raised plants, variance component analysis suggested that CL progeny were genetically more similar to each other than were CH progeny from the same plant. Levene's test of the average deviation of CH and CL progenies from their group means was nonsignificant but suggested there was a trend (0.05 < P < 0.10) for CH progeny to be more variable than CL progeny in the field but less variable in the greenhouse. The amount and distribution of genetic variation in the study population indicates that selective differentials would be larger among families than within families. 相似文献
87.
88.
In Vitro Radioisotopic Labeling of Proteins Associated with Purified Polyoma Virions 总被引:14,自引:11,他引:3
下载免费PDF全文
![点击此处可从《Journal of virology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
An in vitro procedure using [(14)C]formaldehyde and sodium borohydride was used to label the proteins of purified polyoma virions. This method, which labeled the three capsid proteins and the four internal histones of polyoma virus, did not alter the biological and biophysical characteristics of the virus. In addition to the seven viral proteins, five additional radioactive peaks were resolved on polyacrylamide gels. Four of these peaks could be attributed to growing the virus in the presence of serum. The fifth peak appears to be a nonhistone host-contributed protein made before infection. 相似文献
89.
Effect of the anther‐smut fungus Microbotryum on the juvenile growth of its host Silene latifolia
下载免费PDF全文
![点击此处可从《American journal of botany》网站下载免费的PDF全文](/ch/ext_images/free.gif)
90.
Christina Vogel Sarah Crozier Daniel Penn-Newman Kylie Ball Graham Moon Joanne Lord Cyrus Cooper Janis Baird 《PLoS medicine》2021,18(9)
BackgroundPrevious product placement trials in supermarkets are limited in scope and outcome data collected. This study assessed the effects on store-level sales, household-level purchasing, and dietary behaviours of a healthier supermarket layout.Methods and findingsThis is a prospective matched controlled cluster trial with 2 intervention components: (i) new fresh fruit and vegetable sections near store entrances (replacing smaller displays at the back) and frozen vegetables repositioned to the entrance aisle, plus (ii) the removal of confectionery from checkouts and aisle ends opposite. In this pilot study, the intervention was implemented for 6 months in 3 discount supermarkets in England. Three control stores were matched on store sales and customer profiles and neighbourhood deprivation. Women customers aged 18 to 45 years, with loyalty cards, were assigned to the intervention (n = 62) or control group (n = 88) of their primary store. The trial registration number is . Interrupted time series analysis showed that increases in store-level sales of fruits and vegetables were greater in intervention stores than predicted at 3 (1.71 standard deviations (SDs) (95% CI 0.45, 2.96), P = 0.01) and 6 months follow-up (2.42 SDs (0.22, 4.62), P = 0.03), equivalent to approximately 6,170 and approximately 9,820 extra portions per store, per week, respectively. The proportion of purchasing fruits and vegetables per week rose among intervention participants at 3 and 6 months compared to control participants (0.2% versus −3.0%, P = 0.22; 1.7% versus −3.5%, P = 0.05, respectively). Store sales of confectionery were lower in intervention stores than predicted at 3 (−1.05 SDs (−1.98, −0.12), P = 0.03) and 6 months (−1.37 SDs (−2.95, 0.22), P = 0.09), equivalent to approximately 1,359 and approximately 1,575 fewer portions per store, per week, respectively; no differences were observed for confectionery purchasing. Changes in dietary variables were predominantly in the expected direction for health benefit. Intervention implementation was not within control of the research team, and stores could not be randomised. It is a pilot study, and, therefore, not powered to detect an effect.ConclusionsHealthier supermarket layouts can improve the nutrition profile of store sales and likely improve household purchasing and dietary quality. Placing fruits and vegetables near store entrances should be considered alongside policies to limit prominent placement of unhealthy foods.Trial registrationClinicalTrials.gov NCT03518151 (pre-results)Christina Vogel and colleagues assess the effects of creating a healthier layout in supermarkets in England on store-level sales, household-level purchasing, and dietary behaviors of women customers. NCT03518151相似文献