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   151篇
  免费   10篇
林业   17篇
农学   15篇
  20篇
综合类   3篇
农作物   4篇
水产渔业   22篇
畜牧兽医   53篇
园艺   2篇
植物保护   25篇
  2023年   1篇
  2022年   6篇
  2021年   7篇
  2020年   4篇
  2019年   3篇
  2018年   12篇
  2017年   6篇
  2016年   9篇
  2015年   12篇
  2014年   10篇
  2013年   12篇
  2012年   6篇
  2011年   11篇
  2010年   7篇
  2009年   9篇
  2008年   8篇
  2007年   12篇
  2006年   4篇
  2005年   4篇
  2004年   8篇
  2002年   6篇
  1999年   1篇
  1998年   1篇
  1997年   2篇
排序方式: 共有161条查询结果,搜索用时 0 毫秒
101.
Although the role of primates in seed dispersal is generally well recognized, this is not the case for colobines, which are widely distributed in Asian and African tropical forests. Colobines consume leaves, seeds and fruits, usually unripe. A group of proboscis monkeys (Colobinae, Nasalis larvatus) consisting of 1 alpha‐male, 6 adult females and several immatures, was observed from May 2005 to May 2006. A total of 400 fecal samples from focal group members covering 13 months were examined, with over 3500 h of focal observation data on the group members in a forest along the Menanggul River, Sabah, Malaysia. Intact small seeds were only found in 23 of 71 samples in Nov 2005, 15 of 38 in Dec 2005 and 5 of 21 in Mar 2006. Seeds of Ficus (all <1.5 mm in length) were found in all 3 months and seeds from Antidesma thwaitesianum (all <3 mm) and Nauclea subdita (all <2 mm) only in Nov and Dec, which was consistent with members of the study group consuming fruits of these species mostly at these times. To our knowledge, these are the first records of seeds in the fecal samples of colobines. Even if colobines pass relatively few seeds intact, their high abundance and biomass could make them quantitatively significant in seed dispersal. The potential role of colobines as seed dispersers should be considered by colobine researchers.  相似文献   
102.
Penetration rates of laser pulses transmitted from a small-footprint airborne light detection and ranging (LiDAR) system in closed-canopy, middle-aged (40–50 years old) hinoki cypress (Chamaecyparis obtusa Sieb. et Zucc.) and sugi (Cryptomeria japonica D. Don) plantations that had similar levels of canopy openness were studied. The number of transmitted pulses was 107 427 points/ha for the hinoki cypress stand and 122 883 points/ha for the sugi stand. The penetration rates of the first (Pf) and second pulses (Ps) that reached the ground were 0.1% and 1.0% in the hinoki cypress stand, and 2.6% and 5.5% in the sugi stand, respectively. Penetration rates for the total number of pulses (Pf+s) that reached the ground within each stand were 1.1% and 8.1%, respectively, and values for Pf+s, Pf, and Ps for sugi and hinoki cypress stands were significantly different (P < 0.001). The results of this study indicated that the generation of accurate digital terrain models in dense hinoki cypress stands with complex topographies using only the data from laser pulses with poor laser penetration rates is likely to be difficult.  相似文献   
103.
Chromosomes and cytoplasms were analyzed in two lines of a somatic hybrid between onion (Allium cepa L.) and garlic (A. sativum L.). One line of the somatic hybrid had 40 chromosomes and the other 41chromosomes. Genomic in situhybridization successfully revealed the chromosome constitution of the two lines. One line had 20 chromosomes from onion and17 chromosomes from garlic, and the other had 21 chromosomes from onion and 17chromosomes from garlic. Interestingly, both lines had three chimeric chromosomes. PCR-RFLP analyses of chloroplast and mitochondrial DNAs of both lines showed that these were identical to the onion parent. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   
104.
The induction of haploid plants from F1 hybrids between CMS shallot with Allium galanthum cytoplasm and common onion was examined. Starting with 535 unpollinated flowers cultured in B5 medium 25 seedlings from part henogenetic embryos were obtained of which 13 seedlings survived. Eleven seedlings were determined as haploid plants (2n = x = 8) and 2 seedlings were doubled haploid plants (2n = 2x = 16). All haploid and doubled haploid plants preserved chloroplast DNA (cpDNA) and mitochondrial DNA (mtDNA) from A. galanthum. Segregation in different characters was observed among the haploid plants. The haploid and doubled haploid plants exhibited the different combinations of genes from shallot and common onion. Crossing of the doubled haploid plants with other shallot strains, common onion cultivars or related species may produce excellent F1 hybrids for bulb production. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   
105.
106.
Oxidation of low-density lipoprotein (LDL) has been implicated in atherogenesis. Antioxidants that prevent LDL from oxidizing may reduce atherosclerosis. This study investigated LDL antioxidant activity in edible plant products for development of dietary supplementation to prevent atherosclerosis. Fifty-two kinds of edible plants were extracted using 70% aqueous ethanol solution, and the antioxidant activity of the extracts, which inhibit human LDL oxidation induced by copper ion, was determined on the basis of the oxidation lag time and represented as epigallocatechin 3-gallate equivalent. 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity and total phenolic content were also measured for comparisons with antioxidant activity in LDL. Plant products showing the greatest activity in LDL oxidation assay were akamegashiwa (Mallotus japonicus) leaf, Japanese privet (Ligustrum japonicum) leaf, green tea [Camellia sinensis (L.) O. Kuntze], and astringent persimmon (Diospyros kaki). The present study revealed high levels of LDL antioxidant activity in plant products for which such activity levels are underestimated in the DPPH radical scavenging assay and Folin-Ciocalteu assay.  相似文献   
107.
Electrospun atactic polypropylene (PP) fibers are thicker than those obtained from isotactic PP, although the viscosity of molten PPs is almost same. Thus we focused on the effect of tacticity of PP on fiber diameters. The PP samples with various tacticity were prepared by changing the blend ratio of isotactic PP and atactic PP. Melt-electrospinning is performed by using blended samples, and then electrospun fibers were observed by scanning electron microscope to evaluate fiber diameter of obtained fibers. It is clear that the diameter of electrospun PP fibers decreases as high tacticity content of PP increases. This result suggests that tacticity of samples is an important factor to control the electrospun fiber diameter.  相似文献   
108.
Structures of two condensation products obtained by the reaction of cinnamaldehyde with (+)-catechin were determined by spectroscopic methods. One had two phenylpropanoid units at the C-6 and C-8 positions of the catechin skeleton. The other product had a dimeric structure with two catechin and two phenylpropanoid units. Matrix-assisted laser desorption time-of-flight mass spectrometric analysis of the reaction products of cinnamaldehyde with procyanidin B1 suggested that procyanidins were oligomerized in a manner similar to the reaction with catechin. Furthermore, (13)C NMR spectral comparison of the condensation products with the polymeric procyanidins obtained from commercial cinnamon bark strongly suggested that the procyanidins in the cinnamon bark also were polymerized by reaction with cinnamaldehyde.  相似文献   
109.
A digital image correlation (DIC) method was applied to measure strain which arose and remained beneath the finished surface in slow-speed orthogonal cutting of hinoki (Chamaecyparis obtusa), to evaluate the damage in the subsurface cell layers. While the quarter-sawn surface was cut parallel to the grain, the side surface, flat-sawn surface, was captured by a high-speed camera. The images were analyzed to calculate strain in a region of 0.67 × 0.22 mm allocated beneath the finished surface. Almost no strain normal to the cutting direction was detected for the depth of cut and cutting angles, 0.05 mm and smaller than 60°, respectively. For the depths of cut and cutting angles, larger than 0.1 mm and smaller than 60°, respectively, the fore-split induced tensile strain normal to the cutting direction, although it hardly remained after the cutting. The compression strain normal to the cutting direction clearly remained for the cutting angles larger than 70°, regardless of the depths of cut employed in this study. The subsurface damage assumed from the residual strain distribution corresponded to the appearance of the subsurface layer in the X-ray computed tomography (CT) images. It was also revealed, and the DIC program could not always measure excessively large strain correctly.  相似文献   
110.
Tropical Animal Health and Production - The purpose of this study was to investigate the ovarian condition at weaning and subsequent reproductive performance of Berkshire sows following an outbreak...  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