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   98篇
  免费   5篇
林业   12篇
农学   4篇
基础科学   2篇
  28篇
综合类   9篇
农作物   13篇
水产渔业   1篇
畜牧兽医   19篇
园艺   5篇
植物保护   10篇
  2022年   2篇
  2021年   5篇
  2020年   1篇
  2019年   7篇
  2018年   9篇
  2017年   5篇
  2016年   7篇
  2015年   4篇
  2014年   6篇
  2013年   9篇
  2012年   5篇
  2011年   2篇
  2010年   6篇
  2009年   5篇
  2008年   11篇
  2007年   5篇
  2006年   2篇
  2005年   1篇
  2004年   2篇
  2003年   1篇
  2002年   3篇
  1999年   1篇
  1998年   1篇
  1996年   1篇
  1994年   2篇
排序方式: 共有103条查询结果,搜索用时 8 毫秒
81.
Domestication of desirable forest resources in agroforestry is expected to contribute to community based forest conservation efforts, but there may be an optimum level of domestication in this respect. Aren or sugar palm (Arenga pinnata (Wurmb) Merr.) is a multipurpose tree that provides livelihoods for local people and food for other biota in the landscape. However, its domestication is still limited in many places, such as in Batang Toru Forest Block, an area of high conservation value, including habitat for the Sumatran orangutan (Pongo abelii). Options for aren management were prioritized as part of a landscape-scale conservation study by comparing domestication levels in the area. Data on economic indicators and ecological knowledge were gathered through interviews with key farmers, focus groups and transect walks. Four representative villages were selected for the study, that is, (i) two villages with no domestication of aren; and (ii) two villages with aren cultivation in rubber-based land-use systems. Costbenefit analyses suggested that in a rich biodiversity area, such as Batang Toru, although aren was one of the sources of local livelihoods, additional investment for domestication beyond cultivation was not an option considered by farmers. Farmers still perceived wildlife as an efficient mode of aren regeneration, supported by the coexistence of people and other biota in the area. It appears the value of aren for local people’s livelihoods and conservation can be enhanced by increasing its stocking density. There is also scope for improving market access and share of end-user value received by farmers.  相似文献   
82.
Ipek DN  Saki CE  Cay M 《Veterinary parasitology》2012,187(1-2):112-118
Wohlfahrtia magnifica is the main agent of traumatic myiasis in many central and eastern European countries as well as in the Mediterranean basin and Asian countries. The present study was aimed to investigate the effect of myiasis infestation on lipid peroxidation, antioxidant levels and several hematological parameters in the sheep naturally infested with W. magnifica larvae. A total of 38 sheep, including 19 awassi sheep naturally infested with W. magnifica larvae and 19 clinically healthy awassi sheep, were studied. The infected animals were divided into three groups depending on the number of larvae (Group 1: <50 larvae; Group 2: 50-100 larvae; Group 3: >100 larvae). In blood samples, red blood cell counts, hemoglobin, hematocrit concentration and white blood cell, neutrophil, lymphocyte, eosinophil, basophil counts, plasma malondialdehyde, erythrocyte glutathione levels and erythrocyte glutathione peroxidase activity were studied. The results revealed a marked decrease in red blood cell counts and hemoglobin concentrations along with a significant increase in white blood cell and neutrophil counts. The elevation in plasma malondialdehyde levels, a function of lipid peroxidation, established a significant difference between the control group and groups 2, 3. Decreased activity of erythrocyte glutathione peroxidase was found significant in the control group and all parasitemia. We conclude that in natural infestations with W. magnifica, as in infestation with Lucilia cuprina, there is a notable increase in inflammatory activities resulting from the movements, secretions, and toxins of the larvae and form the toxins secreted by the bacteria - which leads to an impression of anemia - and that the tissue injury results in an increase in level of free radicals in the organism.  相似文献   
83.
Seed dormancy and pre-harvest sprouting are important traits in bread wheat. Bi-parental populations have permitted the identification of several genes/quantitative trait loci controlling these traits, mapping to various bread wheat chromosomes. Here, we report the use of association mapping to uncover the genetic basis of both traits in a panel of 96 diverse winter wheat cultivars to establish the presence of marker-trait associations on many chromosomes. Potential candidate genes were identified by studying the gene content of the chromosome bins into which the major marker trait associations mapped.  相似文献   
84.
Xieyou9308 is the first commercial super hybrid rice released in 1996 in China. To clarify its genetic mechanism underlying high yield potential, a recombinant inbred line (RIL) population derived from the cross between the maintainer line XieqingzaoB (XQZB) and the restorer line Zhonghui9308 (ZH9308) and two derived backcross F1 (BCF1) populations were developed for the identification of quantitative trait loci (QTLs) related to ten important agronomic traits (tiller number (TN), heading date (HD), and grain yield per plant (GYPP), etc.). The BCF1 performance was closely correlated with the performance of their parental RILs according to both the analysis of broad-sense heritability (h B 2) and phenotypic correlation coefficient (PCC) in the two BCF1 populations, but not proved by QTL analysis. A total of 21 additive-effect main QTLs (M-QTLs), 22 dominant-effect M-QTLs, and 19 dominant-effect M-QTLs were detected with the WinQTLCart 2.50 software for the ten traits in the RIL and two BCF1 populations, respectively. Of theses, three QTLs (qHD7a, qPPP3a, and qPL10) of 21 were detected repeatedly in the RIL and one BCF1 populations, ten QTLs underlying four traits were only detected repeatedly in two BCF1 populations, and nine QTLs controlling more than two traits were detected repeatedly, the additive-effect QTLs and dominant-effect QTLs play an important role in the performance of agronomic traits and no epistatic QTL of additive by additive effect and dominant by dominant-effect was detected for all traits in three populations. This research is valuable for M-QTL related to important agronomic trait in future fine mapping and positional cloning.  相似文献   
85.
The dual-purpose use of Brassica cultivars means cutting or grazing the crop as fodder and then letting it to re-grow and produce grain with little or no yield penalty. A field experiment was conducted in randomized complete block design with split plot arrangement with three replications. Three Brassica cultivars, three nitrogen application timing, and cutting treatments were included in the experiment. The findings indicated that Brassica cultivar Abasin-95 produced higher fresh and dry fodder yields, seeds pod?1, seed, biological, and oil yields. However, NIFA Raya resulted in a higher number of pods and branches plant?1. Likewise, fresh and dry fodder yields were higher with nitrogen (N) application all at sowing. Nitrogen applied in two splits resulted in a higher number of pods plant?1 and grain yield. Cutting suppressed all parameters except 1000 grain weight. Uncut plots produced significantly higher branches plant?1, pods plant?1, seeds pod?1, seed, biological, and oil yields than cut plots.  相似文献   
86.
A study was made in the net house of Plant Physiology, Department of Botany, Aligarh Muslim University, Aligarh to study the comparative effect of wastewater and groundwater along with three different rates of nitrogen (N) of 0, 30, and 60 kg ha?1 on growth, physiology and yield of two varieties of chilli cv. ‘G4’ and ‘Pusa Jawala’. Wastewater irrigation resulted significant increase in shoot and root length, fresh weight, dry weight, leaf number and area, net photosynthetic rate (PN), stomatal conductance (gs), water use efficiency (WUE), chlorophyll content, and yield. The physio-chemical parameters of wastewater met the irrigational characteristics, being well within the permissible limit as outlined by the Food and Agriculture Organization. Among the nitrogen doses 30 kg ha?1 N along with wastewater proved best for the growth and yield. Thus it may be concluded that wastewater reduced the demand of fertilizers and it may be used for the cultivation of chilli.  相似文献   
87.
Agricultural factors affecting methane oxidation in arable soil   总被引:9,自引:0,他引:9  
CH4 oxidation activity in a sandy soil (Ardoyen) and agricultural practices affecting this oxidation were studied under laboratory conditions. CH4 oxidation in the soil proved to be a biological process. The instantaneous rate of CH4 consumption was in the order of 800 mol CH4 kg–1 day–1 (13 mg CH4 kg–1 day–1) provided the soil was treated with ca. 4.0 mmol CH4 kg–1 soil. Upon repeated supplies of a higher dose of CH4, the oxidation was accelerated to a rate of at least 198 mg CH4 kg–1 day–1. Addition of the plant-growth promoting rhizopseudomonad strains Pseudomonas aeruginosa 7NSK2 and Pseudomonas fluorescens ANP15 significantly decreased the CH4 oxidation by 20 to 30% during a 5-day incubation. However, with further incubation this suppression was no longer detectable. Growing maize plants prevented the suppression of CH4 oxidation. The numbers of methanotrophic bacteria and fungi increased significantly after the addition of CH4, but there were no significant shifts in the population of total bacteria and fluorescent pseudomonads. Drying and rewetting of soil for at least 1 day significantly reduced the activity of the indigenous methanotrophs. Upon rewetting, their activity was regained after a lag phase of about 3 days. The herbicide dichlorophenoxy acetic acid (2,4-D) had a strong negative effect on CH4 oxidation. The application of 5 ppm increased the time for CH4 removal; at concentrations above 25 ppm 2,4-D CH4–oxidizing activity was completely hampered. After 3 days of delay, only the treatments with below 25 ppm 2,4-D showed recovery of CH4–oxidizing activity. This finding suggests that it can be important to include a CH4–removal bioassay in ecotoxicology studies of the side effects of pesticides. Changes in the native soil pH also affected the CH4–oxidizing capacity. Permanent inhibition occurred when the soil pH was altered by 2 pH units, and partial inhibition by 1 pH unit change. A rather narrow pH range (5.9–7.7) appeared to allow CH4 oxidation. Soils pre-incubated with NH 4 + had a lower CH4–removal capacity. Moreover, the nitrification inhibitor 2-chloro-6-trichloromethyl pyridine (nitrapyrin) strongly inhibited CH4 oxidation. Probably methanotrophs rather than nitrifying microorganisms are mainly responsible for CH4 removal in the soil studied. It appears that the causal methanotrophs are remarkably sensitive to soil environmental disturbances.  相似文献   
88.
Allium tuncelianum (Kollman) Özhatay, Matthew & ?iraneci is a native species to the Eastern Anatolia. Its plant architecture resembles garlic (Allium sativum L.) and it has mild garlic odor and flavor. Because of these similarities between two species, A. tuncelianum has been locally called “garlic”. In addition, both A. tuncelianum and garlic has 16 chromosomes in their diploid genomes. Recently, A. tuncelianum has been suggested as the wild progenitor species of garlic. In this study, amplified fragment length polymorphisms (AFLP) markers and nucleotide sequence analysis of the internal transcribed spacer region (ITS) were used to assess genetic and phylogenetic relationships among A. tuncelianum, garlic and some other Allium species. AFLP analysis demonstrated that A. tuncelianum and garlic are genetically distinct and they are likely different species. Phylogenetic analyses based on the nucleotide sequence of ITS suggested that A. tuncelianum and garlic are distinct species and placed A. tuncelianum, garlic, Allium ampeloprasum and Allium scorodoprasum into the same clade in the neighbor joining dendrogram and in the consensus tree of parsimony analysis. However, A. tuncelianum was phylogenetically less related to garlic than either A. ampeloprasum or A. scorodoprasum, suggesting that A. tuncelianum may not be the immediate wild ancestor species of garlic. Further studies to generate hybrid progeny between A. tuncelianum and garlic (if possible) could provide more information on the homology between the chromosomes of A. tuncelianum and garlic and genetic relationships between these two species.  相似文献   
89.
This study analyzed water and soil quality and environmental impacts of shrimp farming in the southwestern coastal region of Bangladesh. Shrimp farming in the region is very traditional in nature where two culture systems viz. shrimp–rice and shrimp-only are being practiced, which are characterized by lower production, repeated stocking, irregular feeding, and fertilizing. Water quality in both farming systems was found suitable for optimum growth and survival of shrimp (Penaeus spp.). The level of 5-day biological oxygen demand (BOD5) in both systems even in canal water was within the recommended level provided by the Government of Bangladesh which is less than 5 mg/l. Therefore, effluents of shrimp farms in the study area did not show any nutrient pollution on the surrounding environment. However, saltwater intrusion has caused many problems like loss of agricultural production, reduced availability of fodder for livestock, and fresh water for domestic uses in the coastal region. The findings of this study confirmed that shrimp farming using saline water have long-term effect of soil salinization. As a result, it poses a real threat toward sustainability of coastal shrimp farming as well as coastal development in Bangladesh.  相似文献   
90.
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