首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   916篇
  免费   81篇
  997篇
  2023年   6篇
  2022年   9篇
  2021年   23篇
  2020年   15篇
  2019年   10篇
  2018年   20篇
  2017年   19篇
  2016年   25篇
  2015年   48篇
  2014年   47篇
  2013年   50篇
  2012年   60篇
  2011年   71篇
  2010年   44篇
  2009年   33篇
  2008年   44篇
  2007年   49篇
  2006年   36篇
  2005年   38篇
  2004年   25篇
  2003年   32篇
  2002年   29篇
  2001年   12篇
  2000年   19篇
  1999年   13篇
  1998年   6篇
  1997年   8篇
  1996年   5篇
  1995年   5篇
  1994年   6篇
  1993年   8篇
  1992年   15篇
  1991年   10篇
  1990年   13篇
  1989年   12篇
  1987年   9篇
  1986年   11篇
  1985年   10篇
  1984年   5篇
  1983年   5篇
  1982年   4篇
  1981年   4篇
  1980年   4篇
  1979年   5篇
  1978年   4篇
  1977年   10篇
  1976年   7篇
  1975年   9篇
  1974年   5篇
  1945年   4篇
排序方式: 共有997条查询结果,搜索用时 0 毫秒
991.
Whole blood serotonin (WBS) determinations were made in 56 pigtailed macaques (Macaca nemestrina) with approximately equal numbers in three age groups: young-adult (4–5 years), middle-aged (13–14 years), and old (over 18 years). The animals were housed in ten living groups with one female and male of each age group in each living group. Half of the groups were fed a diet high in lipid, cholesterol, simple sugars, and sodium; the other half received a restricted diet. Three determinations per animal showed WBS levels to be stable at two times of day and at a 1-week interval, and individual differences were stable over several months' time. The mean WBS concentrations in M. nemestrina were found to be considerably higher than those reported for other species. The mean levels in females were almost 25% higher than in males. No significant effects of age, diet, or dominance status were detected.  相似文献   
992.
993.
994.
The large number of waterborne illnesses in Ireland and worldwide has highlighted the need to enhance strategies that minimize human exposure to pathogens in drinking water supplies. Waterborne pathogens of public concern together with relevant national and international legislation are reviewed in this study. Cryptosporidium species and pathogenic Escherichia coli are among pathogens of primary concern. The organisms originate from the gastrointestinal tract of animals and humans. They may be associated with persistent contamination of water sources, survive for long periods in the environment, and, in particular in the case of Cryptosporidium species, may survive in chlorinated water supplies. Prevention of waterborne infection should emphasize source protection in addition to water treatment. Risk assessment models can play an important role in protecting natural water systems from contamination with these pathogens. Qualitative approaches can provide an effective means of assessing risks with minimum resources and limited data; however, they lack the precision and predictive ability of fully quantitative approaches. Thirteen quantitative simulation models that could potentially be used for modeling bacterial pollutants in agricultural watersheds have been assessed in this study. No one model suits all modeling criteria. Pathogen predictions have proved variable and no model was capable of accounting for all geological and hydrological factors in addition to modeling the physical transport of bacteria in surface runoff. This assessment summarizes commonly used models and their capacity to model water pollution while also providing a good reference point for the microbial risk assessment of waterborne pathogens.  相似文献   
995.
996.
Despite its role as a reference organism in the plant sciences, the green alga Chlamydomonas reinhardtii entirely lacks genomic resources from closely related species. We present highly contiguous and well-annotated genome assemblies for three unicellular C. reinhardtii relatives: Chlamydomonas incerta, Chlamydomonas schloesseri, and the more distantly related Edaphochlamys debaryana. The three Chlamydomonas genomes are highly syntenous with similar gene contents, although the 129.2 Mb C. incerta and 130.2 Mb C. schloesseri assemblies are more repeat-rich than the 111.1 Mb C. reinhardtii genome. We identify the major centromeric repeat in C. reinhardtii as a LINE transposable element homologous to Zepp (the centromeric repeat in Coccomyxa subellipsoidea) and infer that centromere locations and structure are likely conserved in C. incerta and C. schloesseri. We report extensive rearrangements, but limited gene turnover, between the minus mating type loci of these Chlamydomonas species. We produce an eight-species core-Reinhardtinia whole-genome alignment, which we use to identify several hundred false positive and missing genes in the C. reinhardtii annotation and >260,000 evolutionarily conserved elements in the C. reinhardtii genome. In summary, these resources will enable comparative genomics analyses for C. reinhardtii, significantly extending the analytical toolkit for this emerging model system.

High-quality genome assemblies and annotations for three of the closest relatives of Chlamydomonas reinhardtii enable comparative genomics analyses.  相似文献   
997.
In Burkina Faso, onchocerciasis was no longer a public health problem when the WHO Onchocerciasis Control Programme in West Africa closed at the end in 2002. However, epidemiological surveillance carried out from November 2010 to February of 2011, showed a recrudescence of infection in the Cascades Region. This finding was made at a time when ivermectin, a drug recommended for the treatment of both onchocerciasis and lymphatic filariasis, had been distributed in this area since 2004 for the elimination of lymphatic filariasis. It was surprising that ivermectin distributed for treating lymphatic filariasis had not prevented the recrudescence of onchocerciasis. Faced with this situation, the aim of our study was to evaluate the effectiveness of ivermectin on the onchocerciasis parasite. The percentage reduction in microfilarial load after treatment with ivermectin was used as a proxy measure for assessing possible resistance. A cohort study was carried out with 130 individuals who had tested positive for microfilariae of Onchocerca volvulus in 2010 using microscopic examination of skin-snip biopsies from five endemic villages. Subjects were followed from July 2011 to June 2012. The microfilarial load of each individual was enumerated by skin-snip biopsy in 2010, prior to the first ivermectin treatment against onchocerciasis under community guidelines. All individuals received two ivermectin treatments six months apart. In 2012, the microfilarial loads were determined again, six months after the second round of ivermectin and the reductions in parasite loads were calculated to measure the impact of the drug. The percentage reduction of the microfilarial loads ranged from 87% to 98% in the villages. In all villages, there was a statistically significant difference between the average microfilarial loads in 2010 and 2012. The level of reduction of microfilarial loads suggests that ivermectin is effective against the recrudescent population of O. volvulus in Cascades Region of Burkina Faso. Further investigations would be necessary to determine the causes of the recrudescence of onchocerciasis. (For French language abstract, see S1 Alternative Language Abstract—Translation of the Abstract into French by the authors.)  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号