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   199篇
  免费   11篇
  国内免费   1篇
林业   6篇
农学   13篇
基础科学   1篇
  48篇
综合类   5篇
农作物   31篇
水产渔业   24篇
畜牧兽医   58篇
园艺   2篇
植物保护   23篇
  2023年   3篇
  2022年   7篇
  2021年   17篇
  2020年   13篇
  2019年   16篇
  2018年   7篇
  2017年   7篇
  2016年   11篇
  2015年   3篇
  2014年   6篇
  2013年   11篇
  2012年   11篇
  2011年   12篇
  2010年   7篇
  2009年   7篇
  2008年   7篇
  2007年   8篇
  2006年   3篇
  2005年   2篇
  2004年   2篇
  2003年   5篇
  2002年   4篇
  2001年   1篇
  2000年   1篇
  1999年   1篇
  1998年   4篇
  1997年   5篇
  1993年   2篇
  1990年   6篇
  1989年   2篇
  1987年   2篇
  1986年   3篇
  1985年   1篇
  1984年   3篇
  1982年   1篇
  1981年   3篇
  1980年   2篇
  1976年   1篇
  1972年   1篇
  1971年   1篇
  1970年   2篇
排序方式: 共有211条查询结果,搜索用时 328 毫秒
91.
92.
93.

Coffee beverage quality is highly correlated with the degree of fruit ripeness. In this sense, monitoring fruit ripeness is of utmost importance for harvest planning and, especially for obtaining high-quality beverages. Currently, this process is carried out through manual counts of unripe fruits, which is laborious and limited to a few plants within the field. This study aimed at evaluating the potential of a low-cost multispectral camera for coffee ripeness monitoring in the Zona da Mata region of Minas Gerais State, Brazil. For that, five fields of Arabica coffee with distinct characteristics were evaluated. During the coffee ripeness period, four flights were carried using a Phantom 4 Pro quadcopter equipped with a Mapir Survey 3W camera for imagery acquisition. After that, nine vegetation indices (VIs) were obtained. For the same dates, the percentage of unripe fruits was obtained using an irregular grid in all fields. The data was split into two ripeness classes: suitable for harvest (R) with?<?30% of unripe fruits; and not suitable for harvest (U), with?>?30% of unripe fruits. Then, a principal component analysis was used to infer the importance of the VIs to discriminate plants with unripe fruits from those with ripe fruits. The first two principal components explained?>?75% of the variance in the datasets from all coffee fields. The VIs were able to discriminate the ripeness classes (U and R) in most fields; however, their performance was directly influenced by the crop yield and canopy volume.

  相似文献   
94.
Fibroblasts possess several distinct mechanisms that control cellular adhesion to extracellular matrix macromolecules. Monoclonal antibodies to a 140-kilodalton (kD) cell surface glycoprotein inhibited the adhesion of fibroblastic Chinese hamster ovary cells to fibronectin-coated substrata but did not inhibit adhesion to substrata coated with vitronectin, laminin, serum, or other adhesive macromolecules. Thus the 140-kD glycoprotein appears to be involved in the fibronectin-mediated adhesion mechanism but not in other adhesion processes.  相似文献   
95.
The protein quality of typical rice-based menu of Filipino preschool child and adult and cooked milled rice was assessed for true digestibility (TD), biological value (BV) and net protein utilization (NPU) in growing rats. Lysine and energy digestibilities were also determined. For the preschool child diet, TD was 88.8%, BV 90.0%, and NPU 79.9%. For the adult diet, TD was 87.3%, BV 86.6%, and NPU 75.5%, whereas cooked rice had 90.0% TD, 82.5% BV and 74.3% NPU. Lysine digestibility was 95.4% for preschool child diet, 95.7% for adult diet, and 100.0% for rice. Digestible energy was 91.3% for preschool child diet, 93.0% for adult diet, and 95.3% in rice. Amino acid scores were 100.0% for preschooler diet, 92.1% for adult diet, and 62.2% for rice. Protein quality based on amino acid score corrected for TD was 88.8% for preschool child diet. 80.4% for adult diet, and 56.0% for rice. If based on lysine digestibility instead of TD, protein quality would be 7.1% higher.  相似文献   
96.
The protein and energy utilization of brown, undermilled and milled rices (variety IR32) were studied in 5–6 preschool children through diets in which 2/3 of N was from rice and 1/3 from casein or milk powder at 200 or 250 mg N/kg body weight. Brown rice was not significantly inferior to milled rice in terms of nitrogen absorption and retention by the children. Its energy and fat contents were, however, less utilized than those of milled rice. Children on the control casein or milk diets showed better apparent nitrogen absorption than those on the rice-based diets but nitrogen retention of all the diets was similar in all three experiments.  相似文献   
97.
Yellow rice derived from stack-burned unthreshed grains had lower lysine content than white milled rice. Stack burning did not affect energy digestibility in growing rats but decreased true nitrogen digestibility and net protein utilization (NPU). Increasing parboiling time from 20 to 60 min had no adverse effect on energy and protein utilization of parboiled milled rice. Defatting of rice bran-polish with petroleum ether at 50°C had no effect on protein utilization but decreased energy content and utilization. Mechanical dehulling of mung bean (Vigna radiata [L.] Wilczek) reduced fiber content, increased energy and protein digestibility but decreased biological value (BV) and NPU. Toasting and winnowing the bean reduced lysine content, improved digestible energy but decreased BV and NPU. Cooking the bean preparations improved the biological value only in mechanically dehulled bean with resultant higher NPU than that of whole bean.  相似文献   
98.
99.
100.
Wild evening primrose species (Oenothera spp.) native to Argentina, have been suggested as a new crop for irrigated valleys of semi-arid Patagonia. This paper describes patterns of biomass allocation, morphological traits related to stress-tolerance and seed-yield in four species of Oenothera grown in a common garden at three plant densities. Wild and domesticated species are compared. The effect of resource availability on those traits during three phenological stages (vegetative, reproductive and maturity) is described. Native species were characterized by traits related to stress-tolerance (high root allocation and low specific leaf area) during the vegetative stage. This suite of traits resulted in low biomass accumulation and low seed-yield. The domesticated O. biennis was characterized by a combination of traits related to stress-tolerance (low specific leaf area) and high productivity (high leaf allocation and leaf area ratio and low root allocation). Domesticated species accumulated more biomass than natives. Total biomass and total non-structural carbohydrates present in roots were positively correlated to seed-yield.Oenothera biennis showed the highest seed-yield, although this species showed yield instability in response to changes in the environmental quality. No changes in seed-yield in response to plant density were recorded for either O. lamarckiana or native species. Oenothera biennis showed an optimum density of 20 plants m−2 and yielded 260 g m−2, a seed-yield similar to that reported in other countries. Low seed-yield of native species is major drawback that must be overcome. Improving seed-yield in these species could be possible by selection oriented to increase total biomass. Since no detrimental effect of density was found in O. lamarckiana and natives, a higher plant density might increase yield production per unit area.  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