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   226篇
  免费   13篇
  2022年   3篇
  2021年   5篇
  2020年   8篇
  2017年   6篇
  2016年   7篇
  2015年   7篇
  2014年   8篇
  2013年   9篇
  2012年   8篇
  2011年   11篇
  2010年   8篇
  2009年   12篇
  2008年   6篇
  2007年   3篇
  2006年   4篇
  2005年   4篇
  2004年   5篇
  2003年   4篇
  2002年   2篇
  2001年   3篇
  1997年   3篇
  1996年   2篇
  1994年   7篇
  1993年   2篇
  1992年   2篇
  1991年   2篇
  1990年   3篇
  1989年   3篇
  1988年   4篇
  1987年   3篇
  1986年   8篇
  1985年   4篇
  1984年   3篇
  1983年   2篇
  1982年   2篇
  1981年   3篇
  1980年   2篇
  1978年   6篇
  1977年   3篇
  1976年   3篇
  1975年   5篇
  1974年   5篇
  1973年   9篇
  1972年   8篇
  1971年   5篇
  1969年   3篇
  1968年   2篇
  1966年   3篇
  1953年   1篇
  1951年   2篇
排序方式: 共有239条查询结果,搜索用时 31 毫秒
41.
Two Orthotrichum species of the subgenus Orthophyllum were compared with other representatives of this genus using the internally transcribed spacer regions 1 and 2, the chloroplast trnH-psbA region and ISSR and ISJ DNA markers. The applied DNA markers revealed many bands and mutations specific only to O. gymnostomum and O. obtusifolium. A phylogenetic analysis clearly supported the previous concepts postulating that species of the subgenus Orthophyllum should be recognized as separate genus Nyholmiella.  相似文献   
42.

Background

Limited data have indicated that body mass index (BMI), waist circumference (WC), waist to hip ratio (WHR) and waist to height ratio (WHtR) of athletes and young adults provide misleading results concerning body fat content. This study was aimed at the evaluation of the relationship between different surrogate indices of fatness (BMI, WC, WHR, WHtR and body adiposity index (BAI)) with the percentage of body fat in Polish students with respect to their sex and physical activity.

Methods

A total of 272 students volunteered to participate in the study. Of these students, 177 physical education students (90 males and 87 females) were accepted as active (physical activity of 7 to 9 hours/week); and 95 students of other specializations (49 males and 46 females) were accepted as sedentary (physical activity of 1.5 hours/week). Weight, height, waist and hip circumferences were measured, and BMI, WHR, WHtR and BAI were calculated. Body fat percentage was assessed using four skinfold measurements.

Results

Classification of fatness according to the BMI and the percentage of body fat have indicated that BMI overestimates fatness in lean subjects (active men and women, sedentary men), but underestimates body fat in obese subjects (sedentary women). In all groups, BMI, WHR, WHtR and BAI were significantly correlated with the percentage of body fat (with the exception of WHR and hip circumference in active and sedentary women, respectively). However, coefficients of determination not exceeding 50% and Lin’s concordance correlation coefficients lower than 0.9 indicated no relationship between measured and calculated body fat.

Conclusion

The findings in the present study support the concept that irrespective of physical activity and sex none of the calculated indices of fatness are useful in the determination of body fat in young adults. Thus, it seems that easily calculated indices may contribute to distorted body image and unhealthy dietary habits observed in many young adults in Western countries, but also in female athletes.  相似文献   
43.
44.
45.
46.
Runs of homozygosity (ROHs) are recognized signature of recessive inheritance. Contributions of ROHs to the genetic architecture of coronary artery disease and regulation of gene expression in cells relevant to atherosclerosis are not known. Our combined analysis of 24,320 individuals from 11 populations of white European ethnicity showed an association between coronary artery disease and both the count and the size of ROHs. Individuals with coronary artery disease had approximately 0.63 (95% CI: 0.4–0.8) excess of ROHs when compared to coronary-artery-disease-free control subjects (p = 1.49 × 10−9). The average total length of ROHs was approximately 1,046.92 (95% CI: 634.4–1,459.5) kb greater in individuals with coronary artery disease than control subjects (p = 6.61 × 10−7). None of the identified individual ROHs was associated with coronary artery disease after correction for multiple testing. However, in aggregate burden analysis, ROHs favoring increased risk of coronary artery disease were much more common than those showing the opposite direction of association with coronary artery disease (p = 2.69 × 10−33). Individual ROHs showed significant associations with monocyte and macrophage expression of genes in their close proximity—subjects with several individual ROHs showed significant differences in the expression of 44 mRNAs in monocytes and 17 mRNAs in macrophages when compared to subjects without those ROHs. This study provides evidence for an excess of homozygosity in coronary artery disease in outbred populations and suggest the potential biological relevance of ROHs in cells of importance to the pathogenesis of atherosclerosis.  相似文献   
47.
Meloidogyne sp. from five pecan (Carya illinoensis) orchards in Texas were distinctive in host range and iszoyme profiles from common species of Meloidogyne but were morphologically congruent with Meloidogyne partityla Kleynhans, a species previously known only in South Africa. In addition to pecan, species of walnut (Juglans hindsii and J. regia) and hickory (C. ovata) also were hosts. No reproduction was observed on 15 other plant species from nine families, including several common hosts of other Meloidogyne spp. Three esterase phenotypes and two malate dehydrogenase phenotypes of M. partityla were identified by polyacrylamide gel electrophoresis. Each of these isozyme phenotypes was distinct from those of the more common species M. arenaria, M. hapla, M. incognita, and M. javanica.  相似文献   
48.
Forty male guinea-pigs weighing 400-600 g, 8 months old, were given metribuzin directly into the gastric lumen over a period of 30 days (20 animals) or 90 days (20 animals), 6 times a week. The intoxicated animals showed congestion and obliteration of the trabecular structure of the liver. Acidophilic and vacuolar degeneration of the liver cells with signs of necrosis were also observed. Histochemical tests revealed a poorer staining for glycogen and succinic dehydrogenase and intensification of the alkaline and acid phosphatases reaction. The above findings indicate a progressive degeneration due to metribuzin of different organelles of the liver cells including nuclei, mitochondria, lysosomes, microvilli and the cytoplasm.  相似文献   
49.
Application of thermocouples for measuring body temperature of insects is described in experiments on American cockroach (Periplaneta americana). The temperature of the head, mesothorax and abdomen was measured at rest and during flight. The overall accuracy of the measuring system was +/- 0.1 degrees C.  相似文献   
50.
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