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   114篇
  免费   6篇
林业   7篇
农学   1篇
  27篇
综合类   15篇
农作物   5篇
水产渔业   15篇
畜牧兽医   34篇
园艺   2篇
植物保护   14篇
  2022年   3篇
  2020年   1篇
  2019年   4篇
  2018年   3篇
  2017年   5篇
  2016年   2篇
  2015年   3篇
  2014年   6篇
  2013年   2篇
  2012年   5篇
  2011年   4篇
  2010年   7篇
  2009年   6篇
  2008年   11篇
  2007年   6篇
  2006年   5篇
  2005年   4篇
  2004年   7篇
  2003年   6篇
  2002年   8篇
  2001年   4篇
  2000年   1篇
  1999年   2篇
  1998年   1篇
  1997年   2篇
  1991年   1篇
  1988年   3篇
  1985年   1篇
  1984年   1篇
  1979年   1篇
  1971年   2篇
  1968年   2篇
  1966年   1篇
排序方式: 共有120条查询结果,搜索用时 281 毫秒
71.
Germination in the soft wheat (Triticum aestivum L.) cultivar Rosella was followed for three days after imbibition by proteomic analysis of the germ tissue. Two‐dimensional electrophoresis was performed in triplicate for proteins extracted from embryos dissected from mature grain and from grains germinated for 1, 2, and 3 days. For this period, 63 proteins (in 86 spots) in the germ were identified as decreasing in abundance, 35 proteins (in 60 spots) as increasing in abundance, and 28 proteins (in 39 spots) as exhibiting no significant abundance change. Proteins with significant abundance changes are discussed in relation to physiology; these include proteases, amylases and amylase inhibitors, enzymes in lipid metabolism, proteins related to water stress, cell wall hydrolases, oxalate oxidase, and H+‐ATPases. Functions associated with proteins synthesized during the germination period are inconsistent with the embryo of mature grain being fully primed for germination.  相似文献   
72.
The Republic of Kiribati is a small, highly infertile Pacific Island nation and is one of the most challenging locations to attempt to support dense urban populations. Kiribati, like other nations in the Pacific, faces an urban future where food insecurity, unemployment, waste management and malnutrition will become increasing issues. Homegardening is suggested as one way to address many of these problems. However, the most recent study on agriculture production in urban centres in Kiribati shows that, in general, intensive cultivation of homegardens is not a common practice. This disparity between theory and practice creates an opportunity to re‐examine homegardening in Kiribati and, more broadly, in the Pacific. This paper examines the practice of homegardening in urban centres in Kiribati and explores reasons why change has or has not occurred through interviews with homegardeners and government/donor representatives. Results show that homegardening has increased significantly in the past five years, largely because of the promotion of homegardens and organic composting systems by donor organisations. While findings further endorse homegardening as an excellent theoretical solution to many of the problems that confront urban settlements in Kiribati and the Pacific, it raises additional questions regarding the continuation of homegarden schemes beyond donor support programmes.  相似文献   
73.
74.
Six experiments were conducted to determine the true digestible valine requirement of 5- to 20-kg pigs. In Exp. 1, a valine-deficient diet for 5- to 10-kg pigs was developed and validated in terms of growth performance in response to supplemental L-valine. A different basal diet was validated for 10- to 20-kg pigs in Exp. 2. Both diets were demonstrated to be deficient in valine and to support performance equivalent to typical nursery diets when fortified with L-valine. In Exp. 3, true ileal digestibility of valine in the two basal diets was determined in eight pigs fitted with a simple T-cannula at the terminal ileum. Another four pigs received an enzymatically hydrolyzed casein-based diet to determine endogenous contributions to collected ileal digesta. The two diets were found to have true valine digestibilities of 82% (5- to 10-kg pigs) and 86% (10- to 20-kg pigs). In Exp. 4, 80 weaned pigs (5.8 kg) were offered the basal diet fortified with five incremental doses (0.08%) of L-valine. Weight gain increased quadratically (P < 0.05) with increasing levels of valine. Broken-line analysis revealed a true digestible valine requirement of 0.86 +/- 0.03%. In Exp. 5, the true digestible valine requirement of 10- to 20-kg pigs was estimated with 120 pigs (10.9 kg) using the second basal diet fortified with six incremental doses (0.05%) of L-valine. The data suggested a digestible valine requirement level of about 0.775%, which was reevaluated in Exp. 6, wherein pigs did not respond to levels of digestible valine higher than 0.775%. In conclusion, requirement estimates were 2.50 and 2.22 g of true digestible valine per megacalorie of ME for 5- to 10- and 10- to 20-kg pigs, respectively. These empirical estimates are in close agreement with recent estimates of the National Research Council Subcommittee on Swine Nutrition of 2.48 and 2.11 g of true digestible valine per megacalorie of ME, respectively.  相似文献   
75.
Mesotrione is a new callistemone herbicide that inhibits the HPPD enzyme (p-hydroxyphenylpyruvate dioxygenase) and introduces a new naturally selective tool into weed-management programmes for use in maize. Mesotrione provides control of the major broad-leaved weeds, and it can be used in integrated weed-management programmes depending on the grower's preferred weed-control strategy. At post-emergence rates of 150 g AI ha-1 or less, mesotrione provides naturally selective control of key species that may show triazine resistance (TR), e.g. Chenopodium album L, Amaranthus species, Solanum nigrum L, as well as species of weed that show resistance to acetolactase synthase (ALS) inhibitors e.g. Xanthium strumarium L, Amaranthus spp and Sonchus spp. The data presented show that resistant and susceptible biotypes of these species with resistance to triazine herbicides, such as atrazine, simazine, terbutylazine and metribuzin, or ALS-inhibitor herbicides, such as imazethepyr, remain susceptible to mesotrione. These results confirm that there is no cross-resistance in biotypes with target site resistance to triazine or ALS-inhibiting herbicides. It is important that herbicide choice and rotation becomes an integral part of planning weed management, so as to minimise the risks of crop losses from weed competition, build-up of weed seed in the soil and the further development of weed resistance across a range of herbicide modes of action.  相似文献   
76.
The pasting behavior of flour from several Australian rice (Oryza sativa L.) cultivars, differing in amylose content and grown in three different locations and three seasons, were determined using the Rapid Visco Analyser. Genotype, growth season, and growth location all affected the pasting behavior of rice flour. The amylose content of the same cultivar was significantly higher in the coolest growing season, resulting in RVA traces with lower peak viscosity and higher setback than samples with lower amylose content. When the same cultivar of rice was grown in different locations in the same season, there were no significant differences in the total starch, protein, lipid, and amylose content of the flour, but there were significant differences in the pasting behavior. This indicates that environmental as well as genetic factors influence the pasting behavior of rice flour. Flour from parboiled and quick‐cooking rice did not paste and had low viscosities compared with unprocessed rice. Results from this study showed that the pasting behavior of rice flour was related to genotype and was influenced by environmental factors that brought about subtle changes in the grains that were not picked up by chemical analyses.  相似文献   
77.
The American sand lance (Ammodytes americanus, Ammodytidae) and the Northern sand lance (A. dubius, Ammodytidae) are small forage fishes that play an important functional role in the Northwest Atlantic Ocean (NWA). The NWA is a highly dynamic ecosystem currently facing increased risks from climate change, fishing and energy development. We need a better understanding of the biology, population dynamics and ecosystem role of Ammodytes to inform relevant management, climate adaptation and conservation efforts. To meet this need, we synthesized available data on the (a) life history, behaviour and distribution; (b) trophic ecology; (c) threats and vulnerabilities; and (d) ecosystem services role of Ammodytes in the NWA. Overall, 72 regional predators including 45 species of fishes, two squids, 16 seabirds and nine marine mammals were found to consume Ammodytes. Priority research needs identified during this effort include basic information on the patterns and drivers in abundance and distribution of Ammodytes, improved assessments of reproductive biology schedules and investigations of regional sensitivity and resilience to climate change, fishing and habitat disturbance. Food web studies are also needed to evaluate trophic linkages and to assess the consequences of inconsistent zooplankton prey and predator fields on energy flow within the NWA ecosystem. Synthesis results represent the first comprehensive assessment of Ammodytes in the NWA and are intended to inform new research and support regional ecosystem‐based management approaches.  相似文献   
78.
The effectiveness of trap cropping as an integrated control strategy against western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), was explored in potted chrysanthemum, Dendranthema grandiflora (Tzvelev), greenhouse crops. The efficacy of flowering chrysanthemum trap plants, either treated with the insecticide spinosad or untreated, to regulate F. occidentalis populations was tested at different spatial scales (small cage, large cage and commercial greenhouse) and for different time periods (1 or 4 weeks). It was demonstrated that flowering chrysanthemums as trap plants lower the number of adult F. occidentalis in a vegetative chrysanthemum crop and, as a result, reduce crop damage. In the 4 week large-cage trial and the commercial trial, significant differences between the control and the trap plant treatments started to appear in the third week of the experiment. Larvae were only significantly reduced by the presence of trap plants in the 1 week small-cage trials. There were no significant differences between treatments with spinosad-treated and untreated trap plants in the number of F. occidentalis on the crop. This suggests that there was minimal movement of adult F. occidentalis back and forth between the trap plants and the crop to feed and oviposit. It is concluded that the trap plant strategy is a useful tool for integrated pest management against F. occidentalis in greenhouses.  相似文献   
79.
OBJECTIVE: The purpose of this study was to investigate the prevalence of food insecurity and factors related to it among homeless and runaway adolescents. DESIGN: Computer-assisted personal interviews were conducted with homeless and runaway adolescents directly on the streets and in shelters. SETTING: Interviews were conducted in eight Midwest cities: Des Moines, Cedar Rapids, Iowa City, Kansas City, Lincoln, Omaha, St. Louis and Wichita. SUBJECTS: The subjects were 428 (187 males; 241 females) homeless and runaway adolescents aged 16-19 years. Average age of the adolescents was 17.4 (standard deviation 1.05) years. RESULTS: About one-third of the adolescents had experienced food insecurity in the past 30 days. Factors associated with food insecurity were age of adolescent, a history of caretaker neglect and abuse, having ever spent time directly on the street, a small post-runaway social network, and engaging in deviant and non-deviant street food-acquisition strategies. CONCLUSIONS: Based on these findings, our conservative estimate is that nationally more than 165,000 homeless and runaway adolescents experienced food insecurity in the past 30 days. These adolescents are largely hidden from public notice and they are usually missed in studies that address national hunger.  相似文献   
80.
Diversity of the human intestinal microbial flora   总被引:4,自引:0,他引:4  
The human endogenous intestinal microflora is an essential "organ" in providing nourishment, regulating epithelial development, and instructing innate immunity; yet, surprisingly, basic features remain poorly described. We examined 13,355 prokaryotic ribosomal RNA gene sequences from multiple colonic mucosal sites and feces of healthy subjects to improve our understanding of gut microbial diversity. A majority of the bacterial sequences corresponded to uncultivated species and novel microorganisms. We discovered significant intersubject variability and differences between stool and mucosa community composition. Characterization of this immensely diverse ecosystem is the first step in elucidating its role in health and disease.  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