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   53篇
  免费   2篇
林业   5篇
农学   4篇
基础科学   1篇
  11篇
综合类   5篇
农作物   4篇
水产渔业   5篇
畜牧兽医   19篇
园艺   1篇
  2021年   4篇
  2020年   5篇
  2019年   3篇
  2018年   3篇
  2017年   2篇
  2016年   1篇
  2014年   1篇
  2013年   8篇
  2012年   1篇
  2011年   5篇
  2010年   2篇
  2009年   1篇
  2008年   2篇
  2003年   2篇
  2001年   2篇
  1999年   2篇
  1997年   2篇
  1995年   1篇
  1993年   1篇
  1990年   1篇
  1981年   1篇
  1976年   1篇
  1974年   1篇
  1972年   1篇
  1967年   1篇
  1962年   1篇
排序方式: 共有55条查询结果,搜索用时 15 毫秒
21.
Thirty-six four-way cross (Chester White X Landrace X Large White X Yorkshire) growing barrows and gilts were used to investigate the effects of replacing graded levels of protein from soybean meal with equivalent levels of protein from rubber seed meal in 16% CP semipurified diets on the performance characteristics, hematocrit, plasma metabolites and N utilization of pigs. The first diet (control) was largely cornstarch-soybean meal in which the soybean meal supplied all of the CP. In other diets, rubber seed meal replaced 10%, 20% and 30%, respectively, of the protein of soybean meal in the control diet. Twenty gilts were used in a 28-d growth trial and 16 barrows were used in an 8-d digestion trial (4-d collection). There were no differences (P greater than .05) in ADG, ADF intake and in the feed:gain ratios, even though there was a trend for lower ADG and gain:feed ratio as the level of rubber seed meal increased in the diet. There were no differences in hematocrit, but plasma protein and albumin tended to be depressed when rubber seed meal provided more than 10% of the dietary protein. Apparent digestibilities of GE, DM and N were lower with rubber seed meal at 20% of the protein than with any other diet, but apparent N retained and the percent of digested N retained were not depressed significantly (P greater than .05). Although rubber seed meal protein is of poorer quality than soybean meal protein for growing pigs, at least 10% of dietary protein can be provided by rubber seed meal without adversely affecting growth and N utilization.  相似文献   
22.
The acute toxicity of paraquat (1,1-dimethyl-4,4-bipyridinium dichloride) to fingerlings of Oreochromis niloticus (Trewavas) was determined in 96 hr staticbioassays. During the assays opercular ventilation and tailfin movement rates of the fish were determined.Haemotological parameters of the blood and histopathology ofthe gills were observed.The 96 hr LC50 of paraquat to fingerlings of O. niloticus was observed to be 11.84 mg L-1.Histopathology of gills of the fish exposed to 12.00 mgL-1, and 14.20 mg L-1 showed a dose-dependentdisruption of the architecture of the lamellae, filamenthyperplasia and atrophy, leading to impairment in oxygenuptake. Other symptoms of toxicosis in exposed fish includeloss of equilibrium; agitated swimming; air gulping;haemorrhaging of the gills, pectoral and pelvic fins; periodof quiescence and finally, death.  相似文献   
23.
The objective of this study was to investigate the effects of semen volume, air contact inside semen dose tubes, daily agitation of semen doses and extender type on semen quality, thermo-resistance and bacteria growth in extended boar semen doses preserved over 7 days of liquid storage. Ejaculates from 4 proven terminal cross-bred boars were collected using the gloved-hand technique for 4 weeks and used in the 3 × 2 × 2 factorial study. The effects of treatment (CON: 80 ml doses sealed at the top of the tube; 40HIGH: 40 ml doses sealed at top of tube, and 40LOW: 40 ml doses sealed at top of the liquid), agitation (agitated versus not agitated) and extender type (long-term versus short-term) were investigated on semen quality, thermo-resistance and bacteria growth in boar semen doses. The results of the study revealed that motility (p = .031) and viability (p = .041) in 40HIGH were lower than CON. pH (p < .001) was higher in 40HIGH compared with CON and 40LOW. Agitation did not impact motility (p = .581), progressive motility (p = .870), viability (p = .509) or morphology (p = .970), while long-term extender maintained higher motility (p = .002), progressive motility (p = .036), viability (p < .001) and normal acrosome (p < .001) than a short-term extender. VAP (p = .039) of 40HIGH was lower than CON in a thermo-resistance test. Neither treatment (p > .798, .766) nor agitation (p > .396, .476) impacted bacterial growth in this study. In conclusion, air contact negatively impacts boar semen pH and consequently sperm motility. Semen doses prepared with 80 or 40 ml volumes of extended boar semen with minimal air contact in the tubes yield more desirable semen quality and agitating boar semen doses daily does not have negative or positive effects on boar semen quality.  相似文献   
24.
A combination of social survey and direct field observation was used to identify botanicals whose roots were extracted for medicinal purposes in the Ijero Kingdom of Ekiti State, Nigeria. A total of 29 botanicals belonging to 21 families were identified as being used regularly for medication in the study area. Most of these species were not cultivated and are presently endangered as they were rare on the abundance scale used in this study, thus suggesting the need for their conservation. Strategies that would ensure their conservation in the study area are proposed.  相似文献   
25.
26.
27.
This paper analyzes the institutional requirements for sustainable agricultural development in Sub-Saharan Africa. It examines the situation from the perspective of both the recipient and the donor of aid and identifies the institutional conditions under which Official Development Assistance (ODA) — a major source of funding for agricultural development in Sub-Saharan Africa — can become more effective in promoting sustainable development. Agriculture represents the major employment sector in the region (as high as 75 to 80 percent in some countries). However, this high labor force contribution has not been translated into productivity for the sector. Also, bilateral and multilateral development agencies represent a major source of capital and technology for the region's development. Today, Sub-Saharan Africa is the largest recipient of official development assistance in the world, larger on a percentage and per capita basis than any other Third World region. Yet, the region has made only modest progress socioeconomically, compared to other developing regions and is now more dependent on food aid than ever. This raises an issue as to whether conventional technology transfer schemes are adequate in meeting the development needs of the region. Consequently, this study argues the following: that the present framework informing agricultural technology transfer to the region has been ineffective because environmental sustainability, energy efficiency, agricultural self-reliance (including domestic food security), and social equity have not been the central goals of programs.  相似文献   
28.
Ellagic acid (EA), a plant-derived polyphenol, exhibits antioxidant, anti-inflammatory, and gastroprotective effects. Its gastroprotective mechanisms have not been fully elucidated nor have its effects on chronic ulcer previously been described. Toward these ends, the antiulcer activities of EA were evaluated in acute (ethanol and indomethacin) and chronic (acetic acid) ulcer models in Wistar rats. In this study, oral administration of EA significantly prevented the gastric ulceration caused by ethanol, indomethacin, and acetic acid treatments. Its gastroprotective mechanism in ethanol-induced ulcer were partly due to intensification in the endogenous production of nitric oxide, an antioxidant effect by replenishing depletion of endogenous nonprotein sulfhydryls and attenuation of tumor necrosis factor-α increase, whereas in indomethacin ulcer, it is partly due to a reduction in the plasma level of leukotriene B(4). In acetic acid ulcer, promotion of ulcer-healing effects was partly due to attenuation of the elevated levels of the inflammatory cytokines TNF-α, interferon-γ, and interleukins-4 and -6. These findings suggest that ellagic acid exerts its antiulcer activity by strengthening the defensive factors and attenuating the offensive factors.  相似文献   
29.
30.
Mortality is normal and natural in aquaculture experiments. However, it becomes a problem when measuring feed intake as a component of nutrient utilization parameters such as: feed conversion ratio, feed conversion efficiency, apparent net protein utilization, protein efficiency ratio and protein productive value. In order to accurately evaluate feed intake with due consideration of mortality encountered, a formulae was developed using empirical data obtained from an experiement that had mortality. The formulae Fwas: total feed consumed by numbers of survived fishes=DL∑_(i=1)~n(F_i/N_i)N. Where, D=Numbers of days fishes were fed within each period ibefore it was adjusted(e.g fortnight), it was constant throught period of experiment; F=Uantity of feed fed per day for a fortnight before the quantity was adjusted, it changed every fortnight; L=Numbers of living fishes at the end of experimental period; N=Numbers of fishes at each weighing period, it might change every fortnight or might be constant if no mortality occurred; while n=Numbers of times fishes were weighed and quantity of feed was adjusted but this did not include the final weighing at the termination of experiment. However, if the fishes were weighed weekly, then D=6.  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