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   150篇
  免费   4篇
林业   15篇
农学   4篇
基础科学   1篇
  40篇
综合类   12篇
农作物   5篇
水产渔业   18篇
畜牧兽医   49篇
植物保护   10篇
  2021年   3篇
  2020年   2篇
  2019年   2篇
  2018年   2篇
  2017年   2篇
  2016年   6篇
  2015年   3篇
  2014年   1篇
  2013年   18篇
  2012年   8篇
  2011年   10篇
  2010年   10篇
  2009年   3篇
  2008年   7篇
  2007年   9篇
  2006年   10篇
  2005年   10篇
  2004年   5篇
  2003年   6篇
  2002年   5篇
  2001年   11篇
  2000年   1篇
  1999年   1篇
  1998年   4篇
  1997年   1篇
  1996年   1篇
  1994年   1篇
  1993年   2篇
  1989年   2篇
  1987年   1篇
  1980年   1篇
  1979年   1篇
  1978年   1篇
  1974年   2篇
  1973年   1篇
  1971年   1篇
排序方式: 共有154条查询结果,搜索用时 265 毫秒
21.
Feeding systems such as grazing affect the fatty acid profile of bovine milk fat. In addition, milk fat is formed as the product of fatty acid metabolism in cow bodies before being secreted into milk. However, how grazing influences milk fatty acid profile through the metabolism has not been completely characterized. When fatty acid concentrations in Holstein milk were compared between grazing and non‐grazing periods, α‐linolenic acid was significantly higher in the grazing period than in the non‐grazing period. This could be explained with an increase in α‐linolenic acid feeding with grazing. α‐linolenic acid had a linear positive correlation with conjugated linoleic acid (9c,11t‐18:2) (CLA) and vaccenic acid (VA) during the grazing period, whereas CLA had higher correlation with linoleic acid rather than with α‐linolenic acid during the non‐grazing period. These data indicate that the high content of dietary α‐linolenic acid affects CLA and VA formation in milk of grazing periods via α‐linolenic acid metabolism into VA.  相似文献   
22.
Tests of compression perpendicular to the grain were carried out on laminated veneer lumber (LVL) and timber. The species tested were sugi, radiata pine, karamatsu, akamatsu, and dahurian larch; two sets of sugi specimens were tested, with the sugi LVL products being manufactured in different plants. The strength properties of the materials for different loading directions were compared for LVL and timber. At 5% compressive strain in the same materials, the average stress in the tangential direction of timber was larger than that in the radial direction for all species except for radiata pine, and the average stress in the edge-wise direction of LVL was larger than that in the flat-wise direction for all species except for radiata pine. When the stress at 5% strain was compared in the same direction, the average stress of LVL in the edge-wise direction was larger than that in timber in the tangential direction for all species, but there were no great differences between the average stress of LVL in the fl at-wise direction and that of timber in the radial direction for all species except for radiation pine. There was a close relationship between density and stress at 5% strain in LVL, especially in the edge-wise direction. For all results, radiata pine did not follow the trend of the other species; The large annual ring width of radiata pine was considered to have affected the results.  相似文献   
23.
A sensory survey was carried out using 4 different types of whole goat milk among middle‐class females to investigate consumer acceptability of goat milk and whether there is an opportunity to expand the sale of goat milk products in Japan. Four different types of whole milk powder (domestic concentrate‐fed, domestic pasture‐fed, USA commercially canned, and New Zealand commercially canned) were used. Fresh cow milk was served as a control. Thirty‐one housewives evaluated the 5 liquid milk samples for smell, taste and overall characteristics on a scale of 1 (low) to 3 (high). Chi‐square analyses were carried out to detect significant differences between the milk types in each category. The goat milk from the USA was the most preferred goat milk with respect to smell and overall evaluation. Domestic pasture‐fed milk received the lowest grade in the evaluation for its ‘grassy and goaty’ smell. This result shows us that pasture intake affects the taste and smell of powdered milk which gives the lowest evaluation by the participants. If Japanese goat milk producers want to be successful in the domestic goat milk market and compete against goat milk products from other countries, they should improve production methods and flavor of their products.  相似文献   
24.
Mycobacterium avium complex (MAC) is an opportunistic pathogen in AIDS patients and pigs, and causes dissemination through primary intestinal lesions. However, its pathogenesis is not well understood. In this article, we hypothesize that pigs can provide a suitable experimental model of disseminated MAC disease. We compared the initial route of infection, the characteristics of the pathogenic strains, the immunological status of the hosts, and the histological characteristics. The route of infection and infective strains are similar in AIDS patients and pigs. Pigs can respond to infection by the formation of systemic epithelioid granuloma with sufficient cell-mediated immunity. However, there are differences in immunological status and histological features between AIDS patients and pigs. Therefore, pigs might be used as an appropriate animal model because of their good cell mediated immunity triggered by systemic mycobacterial infection. In conclusion, MAC infections in AIDS patients and pigs show similarities in terms of the initial route of infection and the genetic characteristics of the pathogenic strains.  相似文献   
25.
The duration of maternally-derived antibodies against three arboviruses was investigated in calves, using the results of arbovirus serosurveillance performed in Kagoshima Prefecture during 2002–2016. The duration of maternally-derived antibodies against Akabane virus (AKAV), Aino virus (AINOV), and Chuzan virus (CHUV) was estimated to be 178 (sensitivity: 0.769, specificity: 0.730), 156 (sensitivity: 0.806, specificity: 0.791), and 156 days of age (sensitivity: 0.845, specificity: 0.814), by receiver operating characteristic analysis. The duration of maternally-derived antibodies against AKAV, AINOV, and CHUV differed 7–14, 22–28, and 20–31 days in the same calf types between the regions far from each other although it was similar between the adjacent regions. The dairy calves showed 6–29 days longer duration than the beef calves rearing in a similar region.  相似文献   
26.
Abstract

Nitrogen contents, nodule numbers, and nodule dry weights of 6-week-oId Sesbania rostrata plants grown in sand culture with only root nodules, only stem nodules or with both were compared and the root nodules were found to contribute to nitrogen acquisition more significantly than the stem nodules. Similar findings were obtained in 15N2-fixing experiments. An 8-week-old plant with both stem and root nodules fixed 1.50 mg nitrogen in a 12 h light period, while the fixation decreased to 1.15 mg nitrogen after the removal of the stem nodules, suggesting that root nodules played major role in nitrogen fixation. However, acetylene-reducing activities per nodule dry weight were higher in the stem nodules. Under flooding conditions, the aerenchyma tissues contributed to about 40% of N2 transport to root nodules, and 60% was supplied through stem.  相似文献   
27.
Introduction

Uronic acids are aldehydic sugar acids. In nature, they are composed mainly of d-glucuronic acid and d-galacturonic acid and scarcely of dmannuronic acid.  相似文献   
28.
29.
Interannual variations in abundance, timing of outmigration from rivers, growth rate and condition of juvenile chum salmon (Oncorhynchus keta) were studied in the Nemuro Strait (eastern Hokkaido, Japan) during 1999–2002 to establish a possible relationship to zooplankton abundance. The otolith microstructure of juveniles was examined each year in late June to determine their time and size at sea entry (i.e., outmigration), and to estimate the early marine growth rates. Salmon outmigration peaked in mid- or late May, which coincided, in three of the four study years, with the peak release of juveniles into rivers within the study area. Abundance, growth rate and condition of fish were higher in 2001, when—compared to other years—smaller fish experienced higher growth rates, coinciding with greater zooplankton abundance for that year. Our results suggest that high zooplankton abundance positively influenced juvenile chum salmon growth and the condition of the fish during their early marine life despite their small size at sea entry.  相似文献   
30.
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