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   146篇
  免费   11篇
  国内免费   18篇
  2024年   1篇
  2023年   3篇
  2022年   4篇
  2021年   4篇
  2020年   8篇
  2019年   5篇
  2018年   1篇
  2017年   2篇
  2016年   5篇
  2015年   5篇
  2014年   7篇
  2013年   9篇
  2012年   8篇
  2011年   11篇
  2010年   10篇
  2009年   6篇
  2008年   6篇
  2007年   6篇
  2006年   8篇
  2005年   3篇
  2004年   9篇
  2003年   5篇
  2002年   3篇
  2001年   4篇
  2000年   2篇
  1999年   2篇
  1998年   5篇
  1997年   5篇
  1996年   2篇
  1995年   3篇
  1994年   1篇
  1993年   2篇
  1991年   2篇
  1990年   1篇
  1989年   1篇
  1988年   2篇
  1986年   1篇
  1984年   1篇
  1983年   1篇
  1982年   1篇
  1980年   1篇
  1979年   2篇
  1978年   2篇
  1977年   1篇
  1975年   1篇
  1972年   2篇
  1970年   1篇
排序方式: 共有175条查询结果,搜索用时 15 毫秒
91.
92.

Background

We propose a new approach based on genetic distances among viral strains to infer about risk exposures and location of transmission at population level.

Methods

We re-analysed 133 viral sequences obtained during a cross-sectional survey of 4020 subjects living in a hepatitis C virus (HCV) endemic area in 2002. A permutation test was used to analyze the correlation between matrices of genetic distances in the NS5b region of all pairwise combinations of the 133 viral strains and exposure status (jointly exposed or not) to several potential HCV risk factors.

Results

Compared to subjects who did not share the same characteristics or iatrogenic exposures, the median Kimura genetic distances of viral strains were significantly smaller between brothers and sisters (0.031 versus 0.102, P<0.001), mother and child (0.044 versus 0.102, P<0.001), father and child (0.045 versus 0.102, P<0.001), or subjects exposed to periodontal treatment (0.084 versus 0.102, P = 0.02). Conversely, viral strains were more divergent between subjects exposed to blood transfusions (0.216 versus 0.102, P = 0.04) or tooth filling or extraction (0.108, versus 0.097, P = 0.05), suggesting acquisition of the virus outside of the village.

Conclusion

This method provided insights on where infection took place (household, village) for several socio-demographic characteristics or iatrogenic procedures, information of great relevance for targeting prevention interventions. This method may have interesting applications for virologists and epidemiologists studying transmission networks in health-care facilities or among intravenous drug users.  相似文献   
93.
ABSTRACT This paper is intended as an investigation of the biogeographic characteristics of ant faunas of the eight islands in West Sea of South Korea, using quantitative genetic analyses. The faunal similarity is examined using the Nomura-Simpson's Coefficient (NSC). The obtained NSC value matrix was examined by a cluster analysis using UPGMA method. The MSC-values between the seven areas investigated range from 0.500 (Deokjeokdo Hongdo) to 0.909 (Wonsando-Hongdo). In these islands including Seonyudo, the NSC -values range from 0.571 (Deokjeokdo) to 0.778 (Bigeumdo). The cluster analysis using the similarity index (NSC) showed that eight islands were divided into two groups at the level of 41%. It was shown that Wonsando and Bigeumdo were closer (Similarity = 83%) than those between others. Deokjeokdo and Bigeumdo were remote (Similarity = 41%) from each conspecific population. That is, the species composition of Bigeumdo (Similarity = 70%) was similar to that of the Seonyudo, while that of Deokjeokdo (Similarity = 41%) was different from that.  相似文献   
94.
在内蒙古通辽市科尔沁左翼后旗蒙古族居住地区采用随机抽样和农户推荐选择30个农户,同时在邻近地区的汉族选择了10个农户作为对比分析。庭园样方取样为整个庭园面积,设立40个样方进行调查。结果表明,内蒙古通辽市科尔沁左翼后旗蒙古族庭园和邻近地区汉族庭园植物垂直结构主要有0~1 m、1~2 m、2~5 m、5~10 m、10 m等五类,其中不论是小规模庭园还是大规模庭园,5 m以下的阶层占优势;两个民族庭园植物种植模式研究结果阐明科尔沁左翼后旗蒙古族与邻近汉族相比,目前很少栽培观赏植物,仍停留在与日常生活相关的蔬菜植物栽培的水平上,而邻近的汉族已开始注重栽培美化环境的庭园植物。此外,本研究运用MVSP统计软件分析庭园类型表明科尔沁左翼后旗蒙古族庭园主要有4种类型,邻近的汉族庭园有3种类型,并且当地蒙古族与邻近的汉族庭园有所差异,这些差异是由两个民族间农耕文化传统以及畜牧业植物文化差异、庭园面积、庭园历史及庭园管理水平、传统植物利用知识的差异所造成。  相似文献   
95.
This review article presents and discusses the recent progress made in the stabilization, protection, improvement, and design of halide perovskite‐based photocatalysts, photoelectrodes, and devices for solar‐to‐chemical fuel conversion. With the target of water splitting, hydrogen iodide splitting, and CO2 reduction reactions, the strategies established for halide perovskites used in photocatalytic particle‐suspension systems, photoelectrode thin‐film systems, and photovoltaic‐(photo)electrocatalysis tandem systems are organized and introduced. Moreover, recent achievements in discovering new and stable halide perovskite materials, developing protective and functional shells and layers, designing proper reaction solution systems, and tandem device configurations are emphasized and discussed. Perspectives on the future design of halide perovskite materials and devices for solar‐to‐chemical fuel conversion are provided. This review may serve as a guide for researchers interested in utilizing halide perovskite materials for solar‐to‐chemical fuel conversion.  相似文献   
96.
The present work reports the isolation and characterization of new polymorphic microsatellites in mung bean (Vigna radiata L.). Of 93 designed primer pairs, seven were found to amplify polymorphic microsatellite loci, which were then characterized using 34 mung bean accessions. The number of alleles ranged from two to five alleles per locus with an average of three alleles. Observed and expected heterozygosity values ranged from 0 to 0.088 and from 0.275 to 0.683, respectively. All seven loci showed significant deviations from Hardy–Weinberg equilibrium, whereas only one pairwise combination (GBssr‐MB77 and GBssr‐MB91) exhibited significant departure from linkage disequilibrium. These newly developed markers are currently being utilized for diversity assessment within the mung bean germplasm collection of the Korean Gene Bank.  相似文献   
97.
目的比较氯胺酮、地西泮和丙泊酚复合麻醉在外科教学中对犬的麻醉效果。方法成年健康杂种犬42条,诱导麻醉相同,均肌注氯胺酮(10 mg/kg)和氟哌利多(0.5 mg/kg)混合液。静脉维持采用不用的方法,分为三组,分别是静脉滴注氯胺酮地西泮混合液(n=12)、静脉推注氯胺酮地西泮混合液(n=12)和静脉滴注丙泊酚利多卡因混合液(n=18)。结果三组麻醉效果显示,静脉滴注丙泊酚利多卡因混合液效果最好,优83.3%,良16.7%,死亡率0%。结论在外科教学中,对犬采用丙泊酚复合麻醉是一种较为理想的麻醉方法。  相似文献   
98.
纤维素在不同介质中的吸附碱的研究   总被引:1,自引:0,他引:1  
文中研究了纤维素在不同介质(水、乙醇、吡啶及N,N-二甲基乙酰胺)中吸附碱测定情况并通过对比总结出了纤维素对氢氧化钠随用碱量及介质变化规律:纤维素的吸附碱量随着介质及用碱量不同而有所变化,用水作碱化介质比用有机溶剂/水作碱化介质时的吸附碱量少;在用有机溶剂/水作碱化介质时,纤维素对碱吸附表现出大致相同的变化趋势。  相似文献   
99.
The Limulus reaction is an application of the defense mechanism of horseshoe crab for endotoxin detection. Endotoxin is a component of the cell wall in the outer membrane of gram-negative bacteria, and causes fever or shock when it enters the human blood stream. For endotoxin detection, gel formation or turbidity of the coagulation factor chromogen or fluorescence-modified peptide is used. However, these conventional methods have problems with regard to their measurement time or sensitivity. We recently obtained a mutant firefly luciferase that has a luminescence intensity over 10-fold higher than that of the wild type. Therefore, we developed a new endotoxin detection method that combines the Limulus reaction and bioluminescence using mutant luciferase. The new method detects 0.0005 EU/ml of endotoxin within 15 min.  相似文献   
100.
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