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121.
In order to quantitatively analyse the spatial pattern of cacao swollen shoot disease, particularly in cases of re‐emergence, three experimental plots were installed in a diseased area of cacao cv. Amelonado in Togo. After thorough cleaning and grubbing, the three plots were planted with less susceptible, hybrid plant material. Twenty years after replanting, a survey of healthy, diseased and dead trees was carried out during 2 consecutive years. Data were analysed using Ripley’s functions and join counts analysis. The re‐emergence of the disease occurred in patches or foci: following analyses with the two statistical methods, diseased trees and dead trees were found to be clearly aggregated on the three observed plots for the 2 years. The observed progress of the disease was not the same on the three plots and seemed dependent on the disease state of the first year: the higher the attack rate of the first year, the faster the disease progression. The use of less susceptible plants helped keep the land productive for 15 years. In conclusion, uprooting of the first infection focus can extend the life of cacao plots.  相似文献   
122.
采用贝恩的市场结构分类法,对宁德地区养殖产地的市场结构类型、产业市场集中度和产业进入壁垒进行了分析,确定了宁德地区大黄鱼养殖产业的市场结构。研究结果表明:宁德农户养殖的市场集中度指标CR4约为0.87%,市场集中程度很低,处于Ⅵ原子型——不存在集中现象;20余家较大规模养殖企业的CR4约为12.55%,也为Ⅵ原子型;市场竞争性强,接近完全竞争市场;产业进入壁垒较低。得出的基本结论是:产地市场的养殖产业内部集中度较低(Ⅵ原子型),应提高产业内部的集中度;竞争性强,接近完全竞争市场,应控制过度竞争以提高环境资源的配置效率;进入壁垒弱是导致集中度低和完全竞争市场结构的主要原因。  相似文献   
123.
从绿色贸易壁垒的概念和特征入手,从出口总规模、市场结构和农产品种类3个方面介绍了绿色贸易壁垒下安徽省农产品出口现状,分析了安徽省农产品出口遭受绿色贸易壁垒的内、外部原因及对农产品出口的积极和消极影响,最后分别从政府和企业角度提出了应对绿色贸易壁垒的政策措施。  相似文献   
124.
Neighborhood satisfaction and use patterns in public outdoor spaces are generally viewed as single entities, ignoring their multidimensionality as well as detailed associations between them. Such a general assessment raises questions of the kinds of neighborhood characteristics that accrue to satisfaction, and the variety of environmental affordances perceived by residents with respect to nearby outdoor settings. Given the significant role of these factors in people’s life satisfaction and wellbeing, a nuanced approach is needed to help us better understand people-environment relationships and examine practical solutions for creating more livable neighborhoods. This study investigated two-way associations between four aspects of neighborhood satisfaction and three forms of use, as well as the role played by perceived barriers to neighborhood use in these associations. A random sample of 434 Chicago residents participated in a survey (mailed and on-site) with a five-point rating scale. The three major findings through generalized linear modeling include; 1) multidimensionality of both neighborhood satisfaction and use patterns as important to consider in people-environment studies, 2) the significant roles as predictors and as outcomes played by both neighborhood satisfaction and use patterns, with only one factor from each set showing a two-way relationship, and 3) the main effect of perceived barriers on three of the neighborhood satisfactions, and their interactive effect with several of the use pattern and satisfaction factors. These findings contribute to our understanding of people-environment relationships in urban public spaces and provide insights for improving neighborhood satisfaction and frequency of use of public outdoor spaces.  相似文献   
125.
β‐carotene is a robust modulator of mucosal barriers, and it can amplify the immunoglobulin A (IgA) response via the retinoic acid (RA)–mediated pathway. We investigated the influence of β‐carotene on intestinal barriers in layer‐type cockerels. In this study, β‐carotene has a positive influence on growth performance and intestinal morphology. β‐carotene remarkably enhanced serum secretory immunoglobulin A (sIgA) levels, jejunal mucosal sIgA, and IgA concentrations. β‐Carotene significantly enhanced mRNA expression levels of IgA, CC chemokine receptor‐9 (CCR9), polymeric immunoglobulin receptor (pIgR), and retinoic acid receptor α (RARα) in the ileal tissues and pIgR in the jejunal tissues. β‐Carotene improves mRNA expression of intestinal barrier‐related proteins including: mucin‐2 (MUC‐2), zonula occludens‐2 (ZO‐2), occludins (OCLN), and zonula occludens‐1 (ZO‐1) in the ileal tissues. Moreover, β‐carotene decreased the levels of Escherichia coli and elevates the levels of Lactobacillus. The results indicate that β‐carotene can promote growth performance and contribute to the gradual development of intestinal barriers in Hyline Brown chicks. This study enriches our knowledge about the effects of β‐carotene on intestinal barrier and highlights a theoretical basis of β‐carotene application in the poultry industry.  相似文献   
126.
In previous studies, it has been demonstrated that, similar to general practitioners, veterinarians find it difficult to discuss overweight in dogs. This study aimed to provide insight in the barriers and motivators for veterinarians to discuss overweight in dogs and to compare the results with findings from human medicine. Sub-hypotheses were postulated based on existing literature to investigate if lack of time, fear of offending clients, or lack of skills were potential barriers, and if feeling responsible and feeling compassion were potential motivators for veterinarians to discuss overweight in dogs. To this end, an online survey (n = 59) was conducted. Furthermore, 15 small animal clinicians working in general practice were interviewed by semi-structured face-to-face interviews. Results from the online survey indicated that veterinarians find it sometimes difficult to discuss overweight in dogs. Veterinarians who responded to the online survey did not experience strong barriers but did make use of motivators (e.g. feeling responsible and feeling compassion) when discussing overweight in dogs. Interestingly, results from the semi-structured face-to-face interviews showed that the responding veterinarians did experience strong barriers, as well as motivators, when discussing overweight in dogs with their clients. The most prominent barrier was customer dissatisfaction, whereas lack of time and lack of skills were also experienced. The most prominent motivator was feeling responsible for animal health and preventive veterinary medicine. These findings were strikingly similar to previous research on discussing childhood overweight by general practitioners. To improve treatment and prevention of overweight in dogs, veterinarians need more communication skills and should be more aware of the motivators that drive their self-motivation. Improving awareness on overweight and its comorbidities should be a One Health issue.  相似文献   
127.
沙柳是干旱、半干旱地区重要的防风固沙和工业用材树种。以库布齐沙漠采用水冲法植柳造林地低立式沙障、草方格沙障以及混合沙障为对象,研究了3种沙障铺设方式对沙柳保存率及生长指标的影响。试验结果表明,3种沙障均可显著促进沙柳生长(p<0.05),促进作用的顺序依次为:混合沙障 >草方格沙障 >低立式沙障。  相似文献   
128.
The effects of vegetation barriers and tillage on runoff and soil loss were evaluated in an alley crop system at a research station in central Burkina Faso. On a 2% slope of a sandy loam various local species (grasses, woody species and a succulent) were planted as conservation barriers in order to examine their influence on sediment transport. After each erosive storm, runoff and sediment yield was determined. The dense effective barriers (Andropogon gayanus and dense natural vegetation) slow down flow velocity, build up backwater and promote sedimentation uphill. The through flow in the less effective barriers with woody species and succulents (Ziziphus mauritania and Agave sisalana) was slightly hampered and flow velocity was not reduced enough, resulting in a higher soil transport. Under degraded conditions soil loss diminished 50% with less effective and 70–90% with effective barriers. During the initial cropping phase (light tillage; sowing) erosion was reduced 40–60% with effective barriers and showed an increase of 45% with less effective barriers. In the full tillage (weeding) period erosion decreased by 80–90% for effective and 70% for less effective barriers, aided by the development of the barrier and the crop on the alley. Barriers of natural vegetation and A. gayanus are preferred for diminishing soil loss.

Sediment yield could best be predicted by the erosivity index (AIm), second best by runoff amount (mm), closely followed by maximum peak intensity. All these parameters are related to the volume of overland flow needed to transport soil particles. Correlation of soil loss with small rain showers was poor and correlation with big showers was good. Sediment transport with no barrier had the highest correlation, closely followed by less effective barriers. Due to the heterogeneity in development of the effective barrier, correlations were much lower. The bulk of soil loss was only dependent on a few extreme events during the observation period.  相似文献   

129.
畜禽粪肥替代部分化肥还田施用可有效降低作物生产成本和环境成本,促进农业绿色发展.然而,在实际农业生产中存在很多社会经济因素阻碍农户施用粪肥.因此,理解粪肥施用的关键驱动和障碍因素,对化肥减量和提高粪肥还田利用率具有十分重要的意义.本研究以计划行为理论为框架进行问卷设计,以河北省曲周县为研究区域,通过农户调研探究农户粪肥施用的认知和意愿.结果 表明,粮食种植体系粪肥用户占比仅为25%,蔬菜和果树种植体系粪肥用户则分别高达95%和87%.粪肥施用的关键障碍因素包括高昂的粪肥施用成本和负面的农学及环境效应.与经济作物(蔬菜和水果)种植户相比,粮食种植户认知到的粪肥施用障碍因素更多.粪肥施用的主要驱动因素包括提高作物产量、提高土壤肥力、增加农业收入.社会参与方对农户粪肥施用具有积极作用.研究表明,为促进农户粪肥施用,需要利益相关者共同参与,政府应提供政策激励措施,并加强指导,以提高农户对粪肥施用的认知水平.  相似文献   
130.
Abstract Immigration of catadromous anguillid eels into fresh water can be impeded by barriers such as barrages, weirs and dams. The uses of passes and trap-and-transport systems to enhance recruitment are reviewed. Pre-construction studies of the needs for passes and traps are discussed in relation to key biological and hydraulic management criteria. Recommendations for pass and trap designs and placement are made in the context of site-specific biotic and abiotic factors. Reference is made to experience gained from eel passes and trapping systems in use throughout the world, and to experimental and pre-and post-construction monitoring studies. Practical recommendations are made for the design and use of eel passes and traps for monitoring studies and for trap-and-transport stocking.  相似文献   
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