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   378篇
  免费   24篇
  国内免费   27篇
林业   20篇
农学   57篇
基础科学   1篇
  26篇
综合类   162篇
农作物   14篇
水产渔业   41篇
畜牧兽医   76篇
园艺   8篇
植物保护   24篇
  2024年   5篇
  2023年   11篇
  2022年   16篇
  2021年   18篇
  2020年   19篇
  2019年   21篇
  2018年   9篇
  2017年   13篇
  2016年   21篇
  2015年   7篇
  2014年   11篇
  2013年   21篇
  2012年   26篇
  2011年   24篇
  2010年   23篇
  2009年   22篇
  2008年   23篇
  2007年   16篇
  2006年   15篇
  2005年   21篇
  2004年   5篇
  2003年   11篇
  2002年   8篇
  2001年   12篇
  2000年   4篇
  1999年   5篇
  1998年   4篇
  1997年   3篇
  1996年   4篇
  1995年   7篇
  1994年   2篇
  1993年   11篇
  1992年   3篇
  1991年   2篇
  1990年   3篇
  1988年   1篇
  1987年   1篇
  1986年   1篇
排序方式: 共有429条查询结果,搜索用时 15 毫秒
61.
山茱萸保健果冻的研制   总被引:2,自引:0,他引:2  
秦汝兰  王俏 《安徽农业科学》2010,38(9):4816-4816,4826
[目的]从山茱萸中提取多糖,并制作出爽滑可口的保健果冻。[方法]利用水提醇沉的方法,将山茱萸中的多糖提取出来,通过正交试验确定果冻制作的最佳工艺。[结果]山茱萸果冻的最佳配方为山茱萸多糖10%、卡拉胶0.6%、CMC-Na0.1%、白砂糖8%、甜叶菊溶液1.5%、柠檬酸0.2%、柠檬酸钠0.02%、香精0.05%~0.10%。[结论]通过此配方制作出的山茱萸果冻质量指标符合要求。  相似文献   
62.
2008~2009年国内外蜂王浆研究概况   总被引:1,自引:1,他引:0  
对2008~2009年国内外蜂王浆的研究和专利公开情况进行了综述。从年度、地域和研究领域等方面对研究情况进行了统计和比较,就蜂王浆的成分测定、基因与蛋白质组分析、生理药理学功能验证和产业发展等方面的研究成果以及最新专利公开信息和新兴技术的应用情况进行了介绍,并对蜂王浆研究发展的趋势和方向进行了展望。  相似文献   
63.
废弃卡林型金矿区结皮苔藓植物蓄水作用和成土功能研究   总被引:1,自引:1,他引:0  
通过野外调查和实验室分析,对贵州省兴义市新路废弃卡林型金矿区苔藓植物进行了研究。结果显示,该矿区共计有苔藓植物4科6属7种,未发现苔类和角苔,种类组成较单调,其中丛藓科(Pottiaceae)和真藓科(Bryaceae)为优势科;生活型有2种类型:矮丛集型(85.71%)和交织型(14.29%),矮丛集型占有绝对优势;并对该矿区结皮优势苔藓植物硬叶扭口藓、卵蒴真藓、毛口藓和小青藓的生物量、成土量、饱和吸水率和饱和吸水量进行了测定分析。结果显示,该矿区生物量为3.00~52.40g/m2;成土量为217.50~3 695.80g/m2;饱和吸水量为35.10~684.30g/m2;饱和吸水率为1 170.00%~3 637.00%。研究表明,在喀斯特石漠化严重的废弃金矿区,对于在缺少土壤,水土流失严重和植被破坏大的环境区域,苔藓植物以其特有的生态功能在石漠化治理,蓄水作用和成土功能,植被恢复及生态治理等方面起到十分重要的作用。  相似文献   
64.
为了探讨中药灌喂蜜蜂对所产王浆的影响,笔者采用定群编组的方法,观察用不同中药组(1、2、3号)方,灌喂蜜蜂后,台基接受率、王浆产量、微量元素和维生素C水平的改变.结果表明中药组蜂王浆其颜色气味明显区别与普通蜂王浆;观察台基接受率、产浆量发现3号方会影响蜜蜂台基接受率、产浆量外,1、2号方对蜜蜂台基接受率、产浆量无明显影响;进一步研究发现,生物蜂王浆的微量元素、维生素含量区别于普通王浆.用中药灌喂蜜蜂,所产王浆成分有别于普通王浆.  相似文献   
65.
In the 21st century, nutrient efficient plants will play a major role in increasing crop yields compared to the 20th century, mainly due to limited land and water resources available for crop production, higher cost of inorganic fertilizer inputs, declining trends in crop yields globally, and increasing environmental concerns. Furthermore, at least 60% of the world's arable lands have mineral deficiencies or elemental toxicity problems, and on such soils fertilizers and lime amendments are essential for achieving improved crop yields. Fertilizer inputs are increasing cost of production of farmers, and there is a major concern for environmental pollution due to excess fertilizer inputs. Higher demands for food and fiber by increasing world populations further enhance the importance of nutrient efficient cultivars that are also higher producers. Nutrient efficient plants are defined as those plants, which produce higher yields per unit of nutrient, applied or absorbed than other plants (standards) under similar agroecological conditions. During the last three decades, much research has been conducted to identify and/or breed nutrient efficient plant species or genotypes/cultivars within species and to further understand the mechanisms of nutrient efficiency in crop plants. However, success in releasing nutrient efficient cultivars has been limited. The main reasons for limited success are that the genetics of plant responses to nutrients and plant interactions with environmental variables are not well understood. Complexity of genes involved in nutrient use efficiency for macro and micronutrients and limited collaborative efforts between breeders, soil scientists, physiologists, and agronomists to evaluate nutrient efficiency issues on a holistic basis have hampered progress in this area. Hence, during the 21st century agricultural scientists have tremendous challenges, as well as opportunities, to develop nutrient efficient crop plants and to develop best management practices that increase the plant efficiency for utilization of applied fertilizers. During the 20th century, breeding for nutritional traits has been proposed as a strategy to improve the efficiency of fertilizer use or to obtain higher yields in low input agricultural systems. This strategy should continue to receive top priority during the 21st century for developing nutrient efficient crop genotypes. This paper over views the importance of nutrient efficient plants in increasing crop yields in modern agriculture. Further, definitions and available methods of calculating nutrient use efficiency, mechanisms for nutrient uptake and use efficiency, role of crops in nutrient use efficiency under biotic and abiotic stresses and breeding strategies to improve nutrient use efficiency in crop plants have been discussed.  相似文献   
66.
Microbial activity in soil is known to be controlled by various factors. However, the operating mechanisms have not yet been clearly identified, particularly under climate change conditions, although they are crucial for understanding carbon dynamics in terrestrial ecosystems. In this study, a natural incubation experiment was carried out using intact soil cores transferred from high altitude(1 500 m) to low(900 m) altitude to mimic climate change scenarios in a typical cold-temperate mountainous area in Japan. Soil microbial activities, indicated by substrate-induced respiration(SIR) and metabolic quotient(q CO2), together with soil physicalchemical properties(abiotic factors) and soil functional enzyme and microbial properties(biotic factors), were investigated throughout the growing season in 2013. Results of principal component analysis(PCA) indicated that soil microbial biomass carbon(MBC) andβ-glucosidase activity were the most important factors characterizing the responses of soil microbes to global warming. Although there was a statistical difference of 2.82 ℃ between the two altitudes, such variations in soil physical-chemical properties did not show any remarkable effect on soil microbial activities, suggesting that they might indirectly impact carbon dynamics through biotic factors such as soil functional enzymes. It was also found that the biotic factors mainly controlled soil microbial activities at elevated temperature,which might trigger the inner soil dynamics to respond to the changing environment. Future studies should hence take more biotic variables into account for accurately projecting the responses of soil metabolic activities to climate change.  相似文献   
67.
利用Fenton反应,研究了仙草蜜清除羟自由基的作用;采用邻苯三酚自氧化法,研究仙草蜜清除超氧阴离子自由基的作用。结果表明,仙草蜜具有清除羟自由基和超氧阴离子自由基的作用,且在实验的范围内,其清除能力随浓度的增大而增强。  相似文献   
68.
黄原胶与卡拉胶复配在果冻中的应用研究   总被引:2,自引:0,他引:2  
采用单因素及正交试验,研究黄原胶和卡拉胶复配制作果冻的工艺和配方。结果表明:黄原胶与卡拉胶按1∶10复配在果冻中的应用较佳,最佳果冻配方为:黄原胶添加量0.1%,卡拉胶添加量1.0%、白砂糖18%、柠檬酸0.10%、青苹果汁3.0%,做出的果冻色泽均匀、半透明,组织状态良好、口感细腻。  相似文献   
69.
Fish-based methods for assessing European running waters: a synthesis   总被引:1,自引:0,他引:1  
Abstract  The European Union, Water Framework Directive (WFD) requires monitoring of riverine fish fauna. When the WFD came into force in 2000, most of the EU member states did not have fish-based assessment methods compliant to WFD requirements. Therefore, the objectives of FAME ( http://fame.boku.ac.at ), a project under the fifth R&D Framework Programme of the European Commission were to develop, evaluate and implement a standardised fish-based method for assessing the ecological status of European running waters. This paper synthesises the outputs of FAME and defines future research needs. Two different methodologies were used: the so-called spatially based modelling and the site-specific modelling, the latter leading to the European Fish Index (EFI). The advantage of the EFI is that, despite being a single index, it is applicable to a wide range of environmental conditions across Europe precluding the need for inter-calibration. The EFI will support the WFD towards harmonised/standardised assessment and management of running waters in Europe, thus enabling comparative analyses of the ecological status of running waters across Europe.  相似文献   
70.
应用底栖动物完整性指数评价水源地水库溪流健康状态   总被引:2,自引:0,他引:2  
及时了解水源地水库入库溪流的水生态健康状态对保障供水安全十分重要。依据2010-2011年对浙江省水源地汤浦水库的环境和底栖动物观测资料建立了底栖动物完整性指数(B-IBI)。根据Shannon-Wiener指数、百分比模式相似性指数(PMA)和多元统计分析结果对参照条件进行量化并确立参照点群。从60个候选参数中筛选出6个核心参数参与构建B-IBI指标体系,采用四分法进行量纲的统一,以参照点群25%分位值作为水生态系统健康与否的阈值,并对小于25%的分位值分布范围进行2等分,确立了水源地汤浦水库入库溪流健康评价标准:B-IBI>25.50,健康;B-IBI 12.75~25.50,亚健康;B-IBI<12.75,差。B-IBI分值与溶氧水平和pH显著正相关(P<0.05)。  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