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   81篇
  免费   6篇
林业   6篇
农学   11篇
  10篇
综合类   4篇
农作物   2篇
水产渔业   4篇
畜牧兽医   44篇
园艺   1篇
植物保护   5篇
  2023年   1篇
  2022年   4篇
  2021年   11篇
  2019年   2篇
  2018年   1篇
  2017年   2篇
  2016年   5篇
  2015年   3篇
  2014年   5篇
  2013年   11篇
  2012年   7篇
  2011年   6篇
  2010年   3篇
  2009年   6篇
  2008年   5篇
  2007年   2篇
  2006年   2篇
  2005年   1篇
  2004年   2篇
  2003年   2篇
  2002年   1篇
  1997年   1篇
  1996年   1篇
  1990年   2篇
  1988年   1篇
排序方式: 共有87条查询结果,搜索用时 15 毫秒
41.
Fuller et al. (Reports, 23 May 2008, p. 1074) reported that the dorsomedial hypothalamus contains a Bmal1-based oscillator that can drive food-entrained circadian rhythms. We report that mice bearing a null mutation of Bmal1 exhibit normal food-anticipatory circadian rhythms. Lack of food anticipation in Bmal1-/- mice reported by Fuller et al. may reflect morbidity due to weight loss, thus raising questions about their conclusions.  相似文献   
42.
Early weaning induces villous atrophy in the small intestine (SI) of piglets. Oral administration of live lactic acid bacteria (LAB) can improve villous shortening. In this study, we evaluated the oral administration of a heat‐killed and dried cell preparation of Enterococcus faecalis (a LAB) strain EC‐12 against villous atrophy in early‐weaned mice (Experiment 1) and pigs (Experiments 2 and 3). Twelve 16‐days‐old mice were divided into two groups in Experiment 1: gavage of EC‐12 (10 mg/kg body weight (BW)/day), or control. On day 21, SI was collected. Eighteen 21‐day‐old pigs were divided into two groups in Experiment 2: gavage of EC‐12 (10 mg/kg BW/day), or control. After 10 days, the villous height of jejunum was measured. Six 21‐day‐old pigs were divided into two groups in Experiment 3: the basal diet supplemented with EC‐12 at 0.05%‐fed group, or the basal diet‐fed group. After 10 days, the villous height of jejunum was measured. The villous heights in SI were significantly higher by EC‐12 administration in all experiments. EC‐12 successfully improved the villous atrophy in the early‐weaned mice and pigs when EC‐12 was administered orally.  相似文献   
43.
Soil water storage in grassland is critical to regulate herbage yield while it may be threatened by continuous land use without plowing because of the progress of soil compaction associated with worsening soil hydraulic properties. This study aimed at contrasting the quantity and the availability of soil water in a meadow which had not been renovated for 13 years. We monitored matric potentials and mass soil water contents to 100 cm depth from autumn to winter in which plant transpiration was dormant. Soil water capacities were determined with soil water characteristics. The measurements were made in both a harvesting area in which agricultural vehicles had been operated, and a tree cover area which had experienced almost no vehicle loads. The soil layer in the tree cover area had a larger capacity for readily available moisture than that in the harvesting area. The matric potentials in the tree cover area varied in time between 0 and -1000 cm regardless of depth while those in the harvesting area were rather steady. These suggested better pore water continuity in the tree cover area. In the subsoil layers in both the harvesting and the tree cover areas, the soil water contents in terms of actually stored water did not reach as high a level as those expected from the soil moisture characteristics of the matric potential of -1000 cm. On the other hand, the measured matric potentials were consistently readily available for plants during the entire period of measurement. The apparent discrepancy between the matric potentials in readily available vs. actually stored water implied that the subsoil layers had become drier than observed during the study period, and that soil water hysteresis had prevented the full recovery of the water storage.  相似文献   
44.
Effect of cashew nut shell liquid (CNSL), a methane inhibitor, on bovine rumen fermentation was investigated through analysis of the metabolic hydrogen flow estimated from concentrations of short‐chain fatty acids (SCFA) and methane. Three cows were fed a concentrate and hay diet without or with a CNSL‐containing pellet. Two trials were conducted using CNSL pellets blended with only silica (trial 1) or with several other ingredients (trial 2). Methane production was measured in a respiration chamber system, and energy balance and nutrient digestibility were monitored. The estimated flow of metabolic hydrogen demonstrated that a part of metabolic hydrogen was used for hydrogen gas production, and a large amount of it flowed into production of methane and SCFA in both trial 1 and 2, when CNSL was administered to the bovine rumen. The results obtained by regression analyses showed that the effect of CNSL supply on methane reduction was coupled with a significant (P < 0.01) decrease of acetate and a significant (P < 0.01) increase of propionate and hydrogen gas. These findings reveal that CNSL is able to reduce methane and acetate production, and to increase hydrogen gas and propionate production in vivo.  相似文献   
45.
The gene pool of Aegilops tauschii, the D-genome donor of common wheat (Triticum aestivum L.), can be easily accessed in wheat breeding, but remains largely unexplored. In our previous studies, many synthetic hexaploid wheat lines were produced through interspecific crosses between the tetraploid wheat cultivar Langdon and various A. tauschii accessions. The synthetic hexaploid wheat lines showed wide variation in many characteristics. To elucidate the genetic basis of variation in flowering-related traits, we analyzed quantitative trait loci (QTL) affecting time to heading, flowering and maturity, and the grain-filling period using four different F2 populations of synthetic hexaploid wheat lines. In total, 10 QTLs located on six D-genome chromosomes (all except 4D) were detected for the analyzed traits. The QTL on 1DL controlling heading time appeared to correspond to a flowering time QTL, previously considered to be an ortholog of Eps-A m 1 which is related to the narrow-sense earliness in einkorn wheat. The 5D QTL for heading time might be a novel locus associated with wheat flowering, while the 2DS QTL appears to be an allelic variant of the photoperiod response locus Ppd-D1. Some of the identified QTLs seemed to be novel loci regulating wheat flowering and maturation, including a QTL controlling the grain filling period on chromosome 3D. The exercise demonstrates that synthetic wheat lines can be useful for the identification of new, agriculturally important loci that can be transferred to, and used for the modification of flowering and grain maturation in hexaploid wheat.  相似文献   
46.
To study the group‐dependent ecology of Fibrobacter succinogenes in the rumen, real‐time polymerase chain reaction assays for two phylogenetic groups (groups 2 and 3) of F. succinogenes were newly established and applied to rumen samples. Both the assays targeting the bacterial 16S rDNA were sensitive and accurate, showing wide quantifiable ranges (104?109 and 102?109 copies of 16S rDNA) and high recoveries of known amounts of added DNA (96.9 and 98.0%). The quantity of group 1 was confirmed to be numerable by subtracting assay values of groups 2 and 3 from that of F. succinogenes species (groups 1–3). By using the developed assays and the above subtractive calculation, the quantities of all three groups were evaluated in solid and liquid fractions of the rumen content and also on hay stems. In the solid fraction, groups 1 and 2 were abundantly present, compared with group 3 (P < 0.05). On untreated hay stems, group 1 was dominant throughout 48 h. In addition, group 1 showed growth even on the cellulase‐treated hay stems, unlike the other two groups. These results suggest that F. succinogenes group 1 greatly contributes to rumen fiber digestion, even for less degradable materials.  相似文献   
47.
GhCesA2 is a cotton (Gossypium hirsutum) homologue of the bacterial cellulose synthase gene that encodes cellulose 4--glucosyltransferase. The central catalytic region of GhCesA2 was expressed as a soluble protein in the methylotrophic yeastPichia pastoris. The molecular size of the recombinant protein was 100kDa, which decreased to 85 kDa after treatment with endoglycosidase H. The recombinant GhCesA2 catalyzed transfer of glucose from UDP-glucose into unknown products in the presence of an extract of cotton hypocotyls, but the products were not-1,4-glucan.  相似文献   
48.
Hepatitis E virus (HEV) is known as a causative agent of zoonosis and food poisoning. Pigs and some species of wild animals, including wild boar, are known to be a reservoir of HEV. In this study, we investigated the situation regarding HEV infection in wild boars in Ibaraki Prefecture, Japan. Serum, liver and feces samples from 68 animals were collected, and the presence or absence of HEV genomic RNA and HEV antibodies were analyzed. The viral genome was detected in samples from 7 (10.3%) animals, with all HEVs classified as genotype 3, subtype 3b. HEV antibodies were detected in samples from 28 (41%) animals. This report demonstrates for the first time the high prevalence of HEV infection in wild boars in Ibaraki Prefecture.  相似文献   
49.
We developed ring-width chronologies for living trees of Japanese beech at two forest sites on the northern-most part of Honshu Island, Japan. A statistical threshold (running expressed population signal) yielded these site chronologies spanning 1853–1994 (142 years) and 1867–1994 (128 years). We examined two factors, climate and masting, that could affect the variations of radial growth. The response function analysis revealed that the ring width correlated positively with July and August temperatures of the previous growth year. The optimal radial growth of Japanese beech may largely depend on a warm previous summer with above-average temperatures. The years of good masting coincided mostly with those showing abrupt growth depression, although only the short-term records of masting were available. Part of this work was presented at the 6th Pacific Regional Wood Anatomy Conference, Kyoto, December 2005, and the 7th International Conference on Dendrochronology, Beijing, June 2006  相似文献   
50.
Relationship between rumen fermentation parameters, blood biochemical profiles and milk production traits in different yielding dairy cows during early lactation was investigated. Twelve dairy cows were divided into two groups based on their milk yield, that is low‐yield (LY) and high‐yield (HY) groups. Rumen fluid and blood were collected at 3 weeks prepartum and 4, 8 and 12 weeks postpartum. Results showed that proportions of acetate, propionate to total short chain fatty acids and acetate : propionate ratio were changed (P < 0.05) in both groups during the peripartum period, whereas butyrate and acetate : butyrate ratio were only altered in the HY group. Blood cholesterol, beta‐hydroxybutyric acid (BHBA) and glutamic oxaloacetic transaminase in the HY group were higher (P < 0.01) than those in the LY group. Principal component analysis revealed that milk yield and milk compositions were differently clustered between groups. These parameters showed similar direction with dry matter intake in the HY group and adverse direction in the LY group. Linear regression analysis indicated that butyrate was positively correlated with BHBA (P < 0.05) in the HY group. This study suggests that cows in the HY group seem to accommodate appropriately to negative energy balance in early lactation through rumen fermentation.  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