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   196篇
  免费   6篇
  国内免费   1篇
林业   24篇
农学   26篇
基础科学   7篇
  56篇
综合类   7篇
农作物   24篇
水产渔业   13篇
畜牧兽医   25篇
园艺   7篇
植物保护   14篇
  2023年   3篇
  2022年   10篇
  2021年   5篇
  2020年   5篇
  2019年   8篇
  2018年   13篇
  2017年   11篇
  2016年   10篇
  2015年   3篇
  2014年   5篇
  2013年   19篇
  2012年   11篇
  2011年   13篇
  2010年   17篇
  2009年   9篇
  2008年   13篇
  2007年   4篇
  2006年   5篇
  2005年   4篇
  2004年   1篇
  2003年   2篇
  2002年   3篇
  2001年   3篇
  1999年   1篇
  1998年   2篇
  1996年   5篇
  1995年   1篇
  1994年   4篇
  1993年   2篇
  1992年   2篇
  1991年   1篇
  1988年   1篇
  1987年   1篇
  1986年   1篇
  1985年   1篇
  1984年   1篇
  1982年   1篇
  1981年   1篇
  1965年   1篇
排序方式: 共有203条查询结果,搜索用时 15 毫秒
1.
2.
Jamun (Syzygium cumini) is a tropical, underutilized fruit which is highly perishable in nature. It is a good source of vitamin C, tannins, gallic acid and anthocyanins and its beneficial effects are mostly due to the presence of bioactive compounds (pigments and phenolic compounds) in it. Due to astringent and fibrous nature, preparation of jam from jamun pulp is quite difficult, but other fruits (apple and kiwifruit) can be incorporated in it to improve its quality. This study aims to develop jam from blends of jamun with other fruits and analyse various physico-chemical, nutritional, textural and sensory properties. It was found that physico-chemical properties of jams were not found to vary greatly, but the jamun–kiwifruit jam was found to have fairly high amount of antioxidants(46.75 ± 0.67%), tartaric acid (26.24 ± 0.02 mg/100g sample), ascorbic acid (0.08 ± 0.01 mg/100 g sample) and lactic acid (23.95 ± 0.01 mg/100g sample) and lowest amount of 5-hydroxymethyl-2-furaldehyde (0.38 ± 0.04 mg/100 g sample). Jamun jam and jamun–kiwifruit jam possessed the texture required for jam while jamun–apple jam was found to be a relatively harder gel. Jam made with jamun and kiwifruit pulp was found to have highest acceptability on the basis of sensory evaluation.  相似文献   
3.
针对山地果园光线变化和枝叶遮挡干扰果实距离检测的问题,该研究提出一种利用目标区域像素数量变化预测成像距离的算法。根据单目测距原理和柚果成像特性,以具备尺寸和形状代表性的离树柚果样本为研究对象,在采摘作业距离范围内利用单一相机以固定间隔步距对果实某一侧面连续获取图像数据,用以建立并验证目标区域像素数量变化与成像距离变化之间的多元回归关系。随后将该算法应用于果园中树上柚果样本以检验其适用性,并讨论初始成像距离和步距取值对测距精度的影响。研究结果表明,在125 cm以内,6个树上柚果样本的测距相对误差均低于5%,满足采摘机械手目标定位的精度要求;初始成像距离对该算法测距精度具有显著影响。该研究单目测距算法满足果园环境中柚果目标与相机间距离检测需求,为相关采摘机械手的柚果目标识别提供了一种可行方案。  相似文献   
4.
Kamath JV  Rana AC 《Fitoterapia》2002,73(2):111-115
The effect of ethanolic extract of the roots of Calotropis procera has been studied in albino rats to explore its antifertility and hormonal activities. A strong antiimplantation (inhibition 100%) and uterotropic activity was observed at the dose level of 250 mg/kg (1/4 of LD(50)). No antiestrogenic activity could be detected.  相似文献   
5.
The yield and chemical composition of the seed oil of Celastrus paniculatus were determined by solvent extraction and gas chromatography-mass spectrometry. The yield of crude fatty oil was found to be 45.5% in the mature seeds on dry weight basis. Fourteen compounds, constituting 97.57% of the oil, were identified. The oil was rich in unsaturated fatty acids (70.11%) followed by saturated fatty acids (25.2%). Oleic acid (54.42%), palmitic acid (20.0%), linoleic acid (15.51%), and stearic acid (4.18%) were the main fatty acids in the oil together with four other minor fatty acids. The current study identifies the novel compounds not previously reported in C. paniculatus oil, including 1,4-benzenediol (0.46%), cinnamic acid (0.15%), 2,6-di-tert-butyl-p-benzoquinone (0.03%), butylated hydroxytoluene (0.4%), and eudalene (0.16).  相似文献   
6.
7.
Summary The measurement of water consumption in the field is normally restricted to research purposes, although the development of practical field criteria for timing water application is required to improve crop productivity. To develop such criteria irrigation experiments on Soybean were conducted from flowering to grain filling at four locations which differed in their soil properties and the convective contribution of their climates to potential evapotranspiration. The energy balance, predawn leaf water potential (PLWP), soil moisture depletion, and a crop water stress index (CWSI) based on foliage temperature were measured. The range of soil, atmospheric, phenological and irrigation conditions, produced a common, linear relation between relative evapotranspiration (rET) and the logarithm of -PLWP. Correlation with the temperature based CWSI was weak. A similar relation with PLWP for other C3 plants was also derived from data in the literature. This relation could be helpful for irrigation scheduling once the critical values of rET for crop productivity are known.  相似文献   
8.
Growth response and survival of catfish, Heteropneustes fossilis, fed compounded pelleted diet have been studied. It was observed that the fish accepts and thrives well on pelleted feed, with 100% survival. The conversion factor of the feed over a 6-week feeding trial was found to be 1.8, corresponding to gross growth efficiency of 0.56. The study suggests that cost-effective raw materials could be used for compounding nutritive feed for this species.  相似文献   
9.
Ultrastructural changes in Rhabdosargus sarba larva in early life history were investigated. At hatching, the digestive system was histologically undifferentiated. The digestive tract was a straight tube attached to the dorsal end of the yolk‐sac and was not connected to either the mouth or the anus. The layer of gut epithelium at some regions of the luminal surface was straight and microvilli were not present. These straight borders were not observed at 1 day post hatching (DPH) onwards as microvilli increased in number on the luminal surface and became more regular. At 2 DPH, the digestive system was well differentiated and the separation of the mid‐ and hindgut by the intestino‐rectal valve became more advanced. At 0 DPH, the eye was spherical and the retina had a zonation with undifferentiated cells. The eye also lacked differentiated photoreceptors (PR). The retinal PRs increased in length and in number as the yolk‐sac was absorbed. By 2 DPH, the eye was fully pigmented, suggesting that the larval vision system was functional. The larvae had a pure cone retina at the onset of exogenous feeding. Morphological and functional differentiation of the digestive tract and the eye of the larvae preceded the completion of yolk and oil globule absorption. The oil globule was exhausted at 4 DPH and at 2 DPH, the yolk‐sac was completely absorbed. Food particles were observed at 3 DPH. Food particle ingestion and absorption of the yolk‐sac were observed as vision became fully functional.  相似文献   
10.
Tillage modifies soil structure and has been suggested as a practice to improve physical, hydrological and chemical properties of compacted soils. But little is known about effect of long‐term tillage on physicochemical soil properties and crop yield on sodic soils in India. Our objective was to investigate the effect of different tillage regimes on crop yield (wheat and paddy rice) and physicochemical properties of sodic soils. Two sodic sites under conventional tillage for 5 (5‐YT; 5‐year tillage) and 9 (9‐YT; 9‐year tillage) years were selected for this study. Changes in crop yield and physicochemical soil properties were compared with a control, sodic land without any till history, that is, 0‐year tillage/untilled (0‐YT). Five replicated samples at 0‐ to 10‐cm and 10‐ to 20‐cm soils depths were analysed from each site. In the top, 0‐ to 10‐cm soil depth 5‐YT and 9‐YT sites had higher particle density (Pd), porosity, water holding capacity, hydraulic conductivity, organic carbon, total nitrogen (Nt), available nitrogen (Navail), phosphorus (Pavail) and exchangeable calcium (Exch. Ca++) than 0‐YT, whereas bulk density (Bd), C : N ratio and CaCO3 were significantly lower. Bd, pH, EC and CaCO3 increased significantly with depth in all the lands, whereas Pd, porosity, water holding capacity, hydraulic conductivity, organic carbon, Nt, Navail, Pavail and Exch. Ca++ decreased. We conclude that continuous tillage and cropping can be useful for physical and chemical restoration of sodic soils. Copyright © 2014 John Wiley & Sons, Ltd.  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