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   268篇
  免费   18篇
  2024年   1篇
  2023年   4篇
  2022年   2篇
  2021年   3篇
  2020年   4篇
  2019年   3篇
  2018年   6篇
  2017年   3篇
  2016年   7篇
  2015年   7篇
  2014年   16篇
  2013年   28篇
  2012年   17篇
  2011年   16篇
  2010年   13篇
  2009年   17篇
  2008年   18篇
  2007年   10篇
  2006年   9篇
  2005年   12篇
  2004年   8篇
  2003年   11篇
  2002年   12篇
  2001年   3篇
  2000年   5篇
  1999年   7篇
  1998年   3篇
  1997年   1篇
  1996年   1篇
  1995年   4篇
  1994年   2篇
  1992年   5篇
  1991年   1篇
  1990年   1篇
  1989年   3篇
  1988年   3篇
  1985年   4篇
  1984年   1篇
  1980年   1篇
  1979年   1篇
  1976年   1篇
  1974年   2篇
  1973年   2篇
  1972年   1篇
  1971年   3篇
  1969年   1篇
  1968年   1篇
  1966年   1篇
  1953年   1篇
排序方式: 共有286条查询结果,搜索用时 15 毫秒
281.
The effects of cropping pea or barley and the decomposition of their residues on Phymatotrichum root rot of cotton were studied for five years. Little or no changes occurred in pH, content of carbon or moisture in the soil, but there were significant increases in populations of competitive microflora. Best control was obtained in infested soil which was cropped to either pea or barley in winter or in soil which received the higher tonnage of Papago pea plants. Reduction in incidence of root rot may be attributed to premature germination of overwintering propagules making hyphae vulnerable to the chemicals of decomposition and to competition of microflora in the soil.Former Graduate Assistant in Research, Associate Professor, Professor, and Former Professor of Plant Pathology  相似文献   
282.
To improve our understanding of genetic mechanisms underlying complex traits in plants, a comprehensive analysis of gene variants is required. Eucalyptus is an important forest plantation genus that is highly outbred. Trait dissection and molecular breeding in eucalypts currently relies on biallelic single-nucleotide polymorphism (SNP) markers. These markers fail to capture the large amount of haplotype diversity in these species, and thus multi-allelic markers are required. We aimed to develop a gene-based haplotype mining panel for Eucalyptus species. We generated 17 999 oligonucleotide probe sets for targeted sequencing of selected regions of 6293 genes implicated in growth and wood properties, pest and disease resistance, and abiotic stress responses. We identified and phased 195 834 SNPs using a read-based phasing approach to reveal SNP-based haplotypes. A total of 8915 target regions (at 4637 gene loci) passed tests for Mendelian inheritance. We evaluated the haplotype panel in four Eucalyptus species (E. grandis, E. urophylla, E. dunnii and E. nitens) to determine its ability to capture diversity across eucalypt species. This revealed an average of 3.13–4.52 haplotypes per target region in each species, and 33.36% of the identified haplotypes were shared by at least two species. This haplotype mining panel will enable the analysis of haplotype diversity within and between species, and provide multi-allelic markers that can be used for genome-wide association studies and gene-based breeding approaches.  相似文献   
283.
284.
Every year, 2 million women reach menopause in the United States, and they may spend 40% or more of their life in a postmenopausal state. In the years immediately preceding menopause—known as the menopause transition (or perimenopause)—changes in hormones and body composition increase a woman’s overall cardiometabolic risk. In this narrative review, we summarize the changes in weight, body composition, and body fat distribution, as well as the changes in energy intake, energy expenditure, and other cardiometabolic risk factors (lipid profile, glucose metabolism, sleep health, and vascular function), that occur during the menopause transition. We also discuss the benefits of lifestyle interventions in women in the earlier stages of menopause before these detrimental changes occur. Finally, we discuss how to include perimenopausal women in research studies so that women across the life-span are adequately represented.  相似文献   
285.
Treatment of Cymbidium (Orchidaceae) flowers with 10/μl/liter ethylene for up to 78 hr induces anthocyanin formation in both gynostemia (columns) and labella (lips). After that, pigment levels decrease. During 24-hr exposures, ethylene concentrations of 0.1, 1, and 10μl/ liter cause increased anthocyanin levels in both lips and columns. Ethylene also brings about color changes in the calli and wilting of the perianth, but it does not cause straightening of gynostemia and stigmatic closure. Emasculation effects are similar to those of ethylene, whereas pollination and NAA induce anthocyanin formation and closing of stigmas, as well as swelling and loss of curvature in gynostemia. The effects of ethylene are correlated with its action in other systems.  相似文献   
286.
Insects including parasitoid wasps use acoustic and vibratory signals in the context of sexual communication, mate recognition, courtship and mating. Males of the parasitoid wasp Pimpla disparis Viereck (Hymenoptera: Ichneumonidae) detect insect host pupae parasitized by a conspecific female, learn their location, visit them repeatedly and remain on or near them when the prospective mate nears emergence. In the present study, the acoustic and vibratory cues that males exploit to detect the presence and track the developmental progress of a future mate inside a host pupal case are investigated. Responses are acquired from developing parasitoids (DePa) by airborne sound and laser Doppler vibrometer recordings, after gently stimulating each of 20 wax moth host pupae with a paintbrush on days 1–23 post parasitism. Sound and vibratory cues produced by DePa are detectable from day 7 onward and relate mostly to spinning movements. Parameters of sound and vibratory cues (amplitude, dominant frequency, upper limit of frequency band) change significantly over time and thus could ‘inform’ a visiting adult male about the stage of development of DePa. Adult males antennating a parasitized pupa and flying around it also induce vibrations, which in turn may inform DePa about the presence of a male. There is no experimental evidence for true signalling and rapid information exchange between DePa and adult males. Delaying reply signals may help DePa avoid attacks by illicit receivers of such signals, including female (hyper)parasitoids and invertebrate predators.  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