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   178篇
  免费   6篇
林业   35篇
农学   5篇
  32篇
综合类   7篇
农作物   9篇
水产渔业   9篇
畜牧兽医   65篇
园艺   7篇
植物保护   15篇
  2023年   1篇
  2022年   3篇
  2021年   4篇
  2020年   4篇
  2019年   4篇
  2018年   4篇
  2017年   2篇
  2016年   5篇
  2015年   7篇
  2014年   6篇
  2013年   10篇
  2012年   6篇
  2011年   14篇
  2010年   13篇
  2009年   8篇
  2008年   12篇
  2007年   11篇
  2006年   13篇
  2005年   15篇
  2004年   8篇
  2003年   9篇
  2002年   7篇
  2001年   7篇
  1999年   3篇
  1998年   5篇
  1996年   1篇
  1991年   1篇
  1983年   1篇
排序方式: 共有184条查询结果,搜索用时 203 毫秒
61.
Black soybean seed coat extract (BE) is a polyphenol-rich food material consisting of 9.2% cyanidin 3-glucoside, 6.2% catechins, 39.8% procyanidins, and others. This study demonstrated that BE ameliorated obesity and glucose intolerance by up-regulating uncoupling proteins (UCPs) and down-regulating inflammatory cytokines in C57BL/6 mice fed a control or high-fat diet containing BE for 14 weeks. BE suppressed fat accumulation in mesenteric adipose tissue, reduced the plasma glucose level, and enhanced insulin sensitivity in the high-fat diet-fed mice. The gene and protein expression levels of UCP-1 in brown adipose tissue and UCP-2 in white adipose tissue were up-regulated by BE. Moreover, the gene expression levels of major inflammatory cytokines, tumor necrosis factor-α and monocyte chemoattractant protein-1 were remarkably decreased by BE in white adipose tissue. BE is a beneficial food material for the prevention of obesity and diabetes by enhancing energy expenditure and suppressing inflammation.  相似文献   
62.
A hilly to mountainous watershed in Chonju in central Korea does not receive acid rain (average pH: 6.2); however, the stream water in the granite watershed is slightly acidic (6.4–6.7) and contains a low concentration of Ca compared to the stream water in sedimentary and volcanic rock watersheds (6.8–7.6). Although the concentrations of Ca and Sr and the 87Sr/86Sr ratio in the stream water change in accordance with the watershed geology, the stream 87Sr/86Sr ratios are closer to the 87Sr/86Sr ratios of rain than to those of the substrate rocks, suggesting the selective but sluggish weathering of Ca-containing minerals neutralizes acid. The concentrations of trace metals (As, Cr, Cu, Mo, Ni, Pb) in the water are lower than those in rain and less dependent on the watershed geology, indicating that they originated dominantly from the atmosphere. This result is consistent with the stream water having Pb isotope ratios close to that of rain but distinct from that of the rocks. We assume that the soil pool of exchangeable ions dominantly contains atmospherically derived heavy metals, which are subsequently discharged into streams. It is likely that the poor acid-neutralizing capacity of granite makes the aquatic systems in the granite watershed in Chonju sensitive to atmospheric acidification.  相似文献   
63.
Genetic Resources and Crop Evolution - To assess the current genetic status of a useful coastal plant Glehnia littoralis F. Schmidt ex Miq. in Japan, the genetic diversity within and among natural...  相似文献   
64.
To identify the microbial communities responsible for the decomposition of rice straw compost in soil during the rice cultivation period, phospholipid fatty acid (PLFA) composition of rice straw compost was determined by periodically sampling the compost from a Japanese rice field under flooded conditions. About 21% of the compost was decomposed within a period of 3 months. The total amount of PLFAs, as an indicator of microbial biomass, was significantly lower under drained conditions than under flooded conditions and was relatively constant during the flooding period. This indicates that the microbial biomass in the compost samples did not increase during the gradual decomposition of rice straw compost under flooded conditions. The proportion of branched-chain PLFAs (biomarker of Grampositive and anaerobic Gram-negative bacteria) slightly decreased during the early period after placement, and increased gradually afterwards. Among the branched-chain PLFAs, i15:0, ail5:0, i16:0 and i17:0 PLFAs predominated and their proportions increased gradually except for i16:0. The proportion of straight mono-unsaturated PLFAs (biomarker of Gramnegative bacteria) was almost constant throughout the period, and 18:1ω9 and 18:1ω7 PLFAs predominated. The proportion of straight poly-unsaturated PLFAs as a biomarker of eukaryotes including fungi was also constant throughout the period, except for a decrease under drained conditions. Straight poly-unsaturated PLFAs consisted mainly of 18:2ω6c PLFA. Therefore, these results suggest that the proportions of Gram-positive and anaerobic Gram-negative bacteria increased during the decomposition of rice straw compost in flooded paddy field. Statistical analyses enabled to divide PLFA patterns of microbiota in the rice straw compost into two groups, one group consisting of rice straw compost samples collected before mid-season drainage and the other of samples collected after mid-season drainage. Small squared distances among samples in cluster analysis indicated that the community structure of microbiota was similar to each other as a whole. These results suggest that the microbial communities changed gradually during the period of placement, and that mid-season drainage may have affected the community structure of microbiota. Principal component analysis of the PLFA composition suggested that the succession of microbiota along with the decomposition in flooded soil was similar between rice straw compost and rice straw and that the changes in the community structure during the decomposition in flooded soil were more conspicuous for rice straw than for rice straw compost.  相似文献   
65.
Iron (Fe) deficiency is a serious agricultural problem, especially in calcareous soils, which are distributed worldwide. Poplar trees are an important biomass plant, and overcoming Fe deficiency in poplars will increase biomass productivity worldwide. The poplar Fe-deficiency response and the genes involved in poplar Fe homeostasis remain largely unknown. To identify these genes and processes, we cultivated poplar plants under Fe-deficient conditions, both in calcareous soil and hydroponically, and analyzed their growth rates, leaf Soil and Plant Analyzer Development (SPAD) values, and metal concentrations. The data clearly showed that poplars have notable growth defects in both calcareous soil and a Fe-deficient hydroponic culture. They exhibited serious chlorosis of young leaves after 3 weeks of Fe-deficient hydroponic culture. The Fe concentrations in old leaves with high SPAD values were markedly lower in Fe-deficient poplars, suggesting that poplars may have good translocation capability from old to new leaves. The Zn concentration in new leaves increased in Fe-deficient poplars. The pH of the hydroponic solution decreased in the Fe-deficient culture compared to the Fe-sufficient culture. This finding shows that poplars may be able to adjust the pH of a culture solution to better take up Fe. We also analyzed the expression of Fe homeostasis-related genes in the roots and leaves of Fe-sufficient and Fe-deficient poplars. Our results demonstrate that PtIRT1, PtNAS2, PtFRO2, PtFRO5, and PtFIT were induced in Fe-deficient roots. PtYSL2 and PtNAS4 were induced in Fe-deficient leaves. PtYSL3 was induced in both Fe-deficient leaves and roots. These genes may be involved in the Fe uptake and/or translocation mechanisms in poplars under Fe-deficient conditions. Our results will increase a better understanding of the Fe-deficiency response of poplars and hence improve the breeding of Fe-deficiency-tolerant poplars for improved biomass production, the greening of high pH soils, and combatting global warming.  相似文献   
66.
Schoenoplectus juncoides is one of the most harmful weeds found in East Asian paddy fields. Recent emergence of biotypes that are resistant to the herbicide sulfonylurea (SU) has made weed control difficult. To examine the effect of the evolution of this herbicide resistance on genetic diversity within local populations, we investigated microsatellite variability within and among paddy field populations of S. juncoides in Kinki, Japan. In vivo assay of acetolactate synthase activity and root elongation assay in the presence of SU revealed that of 21 populations, five were sulfonylurea‐susceptible (SU‐S) and eight were completely sulfonylurea‐resistant (SU‐R). The remaining eight populations were a mixture of SU‐S and SU‐R individuals. The average gene diversity for SU‐R populations (HS = 0.168) was lower than those for SU‐S (HS = 0.256) and mixed (HS = 0.209) populations, but the difference was not significant. This indicates that positive selection for SU‐R phenotype did not cause a genome‐wide reduction in genetic diversity. Genetic differentiation among S. juncoides populations was higher than that observed for most weed species studied previously. Although populations in neighbouring paddy fields showed a high level of differentiation, Bayesian clustering analyses suggested that some level of gene flow occurs among them and that the genetic exchange or colonisation between neighbouring populations could contribute to the geographical expansion of the resistant allele.  相似文献   
67.
Self-EcoTILLING to identify single-nucleotide mutations in multigene family   总被引:1,自引:0,他引:1  
TILLING (Targeting Induced Local Lesions IN Genomes) is a low-cost, high-throughput reverse genetic technique that employs a mismatch-specific endonuclease CEL-1 to discover induced point mutations in the genes of interest. The use of the TILLING technique to survey natural variation in genes is called EcoTILLING. Here, we report a modified EcoTILLING method for the discovery of mutations in multigene family, which we coin “Self-EcoTILLING” by using an allotetraploid Monochoria vaginalis ALS multigene family as an example. The mutations could be detected by TILLING of PCR products resulting from the primers specific to both Als1 and Als3 without involving the experimental step of mixture of reference and query DNA. Either of the two co-amplified loci could serve as reference DNA to the other. We demonstrate with this example that Self-EcoTILLING is a fast, reliable and economical technique of detecting single-nucleotide mutations in polyploid plants containing multigene family.  相似文献   
68.
A model is proposed to calculate the spadix temperature of the skunk cabbage Symplocarpus foetidus which regulates its internal temperature at around 20 °C during the female stage even when the ambient air temperature drops below freezing. The model is based on energy balance of the spadix under field conditions. The input data are standard meteorological data and spadix parameters. The model output was compared with experimental data collected under different climate conditions. The agreement between observed and calculated spadix temperatures was fairly good.  相似文献   
69.
Controlled self-assembly of a trinitrofluorenone-appended gemini-shaped amphiphilic hexabenzocoronene selectively formed nanotubes or microfibers with different photochemical properties. In these nanotubes, which are 16 nanometers in diameter and several micrometers long, a molecular layer of electron-accepting trinitrofluorenone laminates an electron-donating graphitic layer of pi-stacked hexabenzocoronene. The coaxial nanotubular structure allows photochemical generation of spatially separated charge carriers and a quick photoconductive response with a large on/off ratio greater than 10(4). In sharp contrast, the microfibers consist of a charge-transfer complex between the hexabenzocoronene and trinitrofluorenone parts and exhibit almost no photocurrent generation.  相似文献   
70.
The thermoplastic flow behavior of cedar flour steamed at different temperatures in the range of 160–220°C was measured using a rheometer and compared with that of beech flour. The temperature at which the cedar flour starts to flow was approximately 70°C higher than that of beech flour, and the cedar flour exhibited low flowability. Furthermore, thermoplastic moldings were prepared from cedar and beech flours, and their physical properties were examined. Similar to the case of beech, a resin-like molding with a density of approximately 1.45?g/cm3 was obtained from the cedar flour steamed at 180°C or higher, and it was revealed by SEM observation that in these moldings wood flour particles adhere to each other. The specific bending strength was maximum for the moldings obtained from 180°C-steamed flour for both types of wood.  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