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   136篇
  免费   3篇
林业   27篇
农学   9篇
基础科学   1篇
  22篇
综合类   4篇
农作物   8篇
水产渔业   23篇
畜牧兽医   34篇
园艺   1篇
植物保护   10篇
  2022年   2篇
  2021年   8篇
  2020年   2篇
  2019年   7篇
  2018年   5篇
  2017年   3篇
  2016年   4篇
  2015年   2篇
  2014年   7篇
  2013年   15篇
  2012年   10篇
  2011年   7篇
  2010年   4篇
  2009年   6篇
  2008年   8篇
  2007年   10篇
  2006年   6篇
  2005年   7篇
  2004年   1篇
  2003年   6篇
  2002年   3篇
  2001年   2篇
  2000年   1篇
  1999年   2篇
  1996年   1篇
  1995年   1篇
  1994年   1篇
  1989年   1篇
  1976年   1篇
  1975年   3篇
  1974年   1篇
  1967年   1篇
  1930年   1篇
排序方式: 共有139条查询结果,搜索用时 109 毫秒
1.
This study investigated the effects of supplementary feeds with different crude protein (CP) levels on the growth and economic performances of sex-reversed Nile tilapia (Oreochromis niloticus) reared in a rain-fed rice–fish ecosystem for a period of 120 days. There were four treatments—namely, traditional feed (21% CP), formulated feed (26% CP), commercial feed (30% CP), and control (no feed was used)—with three replicates per treatment. Fish (30.04 g) were stocked in ditches at a rate of 0.5 fish m?2 considering the total area and fed one of the tested feeds twice daily at the rate of 2%–5% of body weight. Water-quality parameters of the ditches were monitored fortnightly, and these parameters were found suitable for fish farming. Organic matter, total nitrogen, and available phosphorous in soil were increased significantly (P < 0.05) in the feed treatments after fish cultivation. Highly significant weight gain and SGR were observed with fish fed the commercial feed as compared with other treatments. The highest benefit-cost ratio (2.15) was found in the control, followed by formulated feed (1.90), but in the case of numerical net return, it was the opposite. However, commercial feed showed the lowest benefit-cost ratio (1.67) due to higher feed cost than other supplementary feeds. Therefore, this study suggests that fish fed with a formulated feed (26% CP) produced significantly higher net economic return in the rice–fish farming system.  相似文献   
2.
3.
One myrsinol-type diterpene ester (1) isolated from Euphorbia decipiens was evaluated for analgesic activity in the acetic acid induced writhing test in mice. Different dose (5-20 mg/kg i.p.) of the compound showed significant antinociceptive activity, which was comparable to standard analgesic drugs, aspirin and ibuprofen (100 mg/kg i.p.).  相似文献   
4.
Oocytes retrieval, in vitro maturation (IVM) and fertilization (IVF) efficiency are inevitable steps towards in vitro production of embryos. In the present study, these parameters were investigated in the ovaries of prepubertal (n = 31) and pubertal (n = 61) black Bengal goats obtained from a slaughterhouse. Nuclear maturation was evaluated upon aspiration and following IVM in TCM-199 (Earle''s salt with L-glutamine and sodium bicarbonate) for 27 h at 39℃ under 5% CO2 in humidified air. The oocytes retrieval and efficiency (mean ± SD) per prepubertal and pubertal goats were 5.2 ± 0.6 and 6.8 ± 0.6, and 77.3 ± 0.1% and 80.5 ± 0.6%, respectively. Anaphase I - telophase I stages differed significantly (7.3 ± 0.8 vs. 2.6 ± 0.2, p < 0.05) between the two groups of goats. After IVM, the percentages of metaphase II were significantly higher (66.3 vs. 60.3, p < 0.05) in pubertal goats than in their prepubertal counterparts. The percentages of normal in vitro fertilization (IVF) in Fert-Tyrode''s albumin lactate pyruvate of pubertal goat oocytes did not differ between Percoll and swim-up sperm separation methods (36.7 ± 0.9% vs. 32.7 ± 1.3%, p > 0.05). Furthermore, sperm capacitation by heparin alone or in combination with ionomycin did not lead to a significant increase in the normal fertilization rate (34.8 ± 1.7 vs. 32.2 ± 1.5%, respectively) in the oocytes of pubertal goats. In conclusion, the ovaries of pubertal black Bengal goats obtained from the slaughterhouse could be used for in vitro embryo production. However, further optimization of the IVM and IVF techniques are necessary for satisfactory in vitro embryo production.  相似文献   
5.
Significant tomato matrix effects on the volatility of certain fresh tomato odorants were found. The concentrations of odorants such as (E,E)-2,4-decadienal, beta-damascenone, and beta-ionone, in crushed fresh tomato fruit obtained by solid-phase microextraction (SPME), resulting from a tomato matrix calibration curve were 5.5-, 2-, and 12-fold higher, respectively, than those calculated by calibration based on buffer solutions. Static headspace analyses indicated that, in most cases, the tomato matrix significantly retains the odorants relative to the buffer solution. Thus, the concentration of odorants in the headspace of tomato is lower than expected compared to a simple matrix such as buffer. CaCl(2), although needed in crushed fruit tissue to block enzymatic activity, was found to interact specifically with 2-isobutylthiazole, reducing its content in the headspace by at least 6-fold. If a matrix effect is found, analysis of the odorant molecule contents in the headspace rather than in the food is recommended in order to better evaluate their access to the olfactory receptors.  相似文献   
6.
对苗床培养的楹树、雨豆树和水黄皮袋装幼苗(6月龄)施以80kg·hm-2的磷酸盐,通过比较不同收获间隔期幼苗生长和生节情况,研究了施加磷肥对三个农林复合树种幼苗生长和生节作用。研究表明,施加磷肥显著促进雨豆树和水黄皮幼苗生长,但并未促进楹树幼苗生长。此外,施加磷肥还会显著增加楹树、雨豆树幼苗生节数和节大小,但对水黄皮幼苗作用较小,而且高收割间隔期会降低水黄皮生节表现。  相似文献   
7.
An experiment was carried out at the Agronomy Field Laboratory, Bangladesh Agricultural University (BAU), Mymensingh in Old Brahmaputra Alluvial Flood Plain (AEZ-9) during December 2005 to May 2006 to examine the root growth of different rice cultivars under various establishment methods. This experiment comprised two sets of treatment (i) three methods of planting viz., dry direct seeding, wet direct seeding and transplanting, and (ii) six rice cultivars, two inbreds viz., BRRI Dhan 28 and BRRI Dhan 29, two hybrids, viz., Aalok 6201 and Sonarbangla 1 and two local improved cultivar viz., Habigonj IV and Habigonj VIII. Cultivars had more remarkable effect on different root parameters i.e. number of roots, root length, root length density, root biomass, root weight ratio and root shoot ratio of hybrid, inbred and local improved rice cultivars than method of planting. BRRI Dhan 28 performed the best for most of the parameters. At harvest, BRRI Dhan 29 showed the best rooting behavior among the cultivars. For both stages hybrid rice cultivars showed intermediate and local improved cultivars performed lower in rooting behavior. Direct seeding method performed better than transplanting method for most of the root parameters but wet direct seeding and dry direct seeding methods were identical. Interaction effect between method of planting and cultivar in most of the root parameters were insignificant. But, BRRI Dhan 28 and BRRI Dhan 29 under wet direct seeding method and Sonarbanngla 1 under transplanting method showed the best rooting performance among the other combinations.  相似文献   
8.
The aim of this study was to investigate the load and distribution patterns of the aerobic bacterial flora associated with pond water, sediments, gills, and intestines of healthy African catfish, Clarias gariepinus, cultured in Saudi Arabia. Counts of viable bacteria ranged from 7.9 ± 4.4 103 to 4.3 ± 5.7 104 colony forming units (cfu)/mL in water; 1.3 ± 2.7 108 to 7.4 ± 4.6 109 cfu/g in sediments; 8.7 ± 1.8 106 to 6.6 ± 5.8 107 cfu/g in gill filaments; and 8.8 ± 6.2 108 to 4.3 ± 2.8 1010 cfu/g in intestines. The bacterial flora was predominantly comprised of gram-negative rods, accounting for 75% of the total isolated strains. Altogether, 11 bacterial species of 8 genera were identified: Aeromonas hydrophila, Shewanella putrefaciens, Vibrio cholerae, Staphylococcus sp., Corynebacterium urealyticum, and Vibrio vulnificus were the most common with the first three dominating (prevalence > 14%) in every population studied.  相似文献   
9.
The development of the dairy industry plays an important role in the economy of Middle Eastern countries. Judged by its growth rate, the dairy industry is viewed as one of the most progressive food industries in the Middle East. During the early 1970s, countries established executive programs to promote dairy farming; the major objective was to attain self-sufficiency in milk production. A massive investment was set up for importing top class cattle, complying with top industry operating standards, and a simultaneous introduction of the latest technology in processing, packaging, and distributing. Milk production has grown tremendously at rates of 6.6% and 4.9% in Syria and Saudi Arabia, respectively, between 2002 and 2007, which resulted in these nations being almost self-sufficient. Regarding Jordan, milk production has not yet met this target. An excessive growth in the dairy industry is quite noticeable in this region with an expanding capacity for exports. The aim of this study is to show the most recent trends and future prospects of the dairy industries in Syria, Saudi Arabia, and Jordan. It also attempts to investigate the drivers for the development of milk production, consumption, and trade in the region.  相似文献   
10.
对孟加拉吉大港地区家庭竹子手工业非农就业的潜力以及对其产生的社会经济效益进行了调查。本地区有40个竹企业,涉及到Hathazcori upazila的4个村庄。80%手工业者的年龄在30~50岁。他们的大多数是未受教育和土地贫瘠的家庭成员。50%的企业是由夫妻或3~5个工人组成的。竹产品主要是满足当地市场的需求。产品是根据季节的变化而决定的。5个产品中,竹书架提供了企业月净收入的41%,平均月净利润约2373.48塔卡,这为促进乡村经济发展起到重要的作用。作者对竹产业发展的状况进行了验证,并提出了建议。  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