全文获取类型
收费全文 | 1054篇 |
免费 | 63篇 |
国内免费 | 53篇 |
专业分类
林业 | 75篇 |
农学 | 20篇 |
基础科学 | 7篇 |
62篇 | |
综合类 | 342篇 |
农作物 | 34篇 |
水产渔业 | 285篇 |
畜牧兽医 | 304篇 |
园艺 | 13篇 |
植物保护 | 28篇 |
出版年
2024年 | 8篇 |
2023年 | 18篇 |
2022年 | 22篇 |
2021年 | 28篇 |
2020年 | 36篇 |
2019年 | 36篇 |
2018年 | 11篇 |
2017年 | 22篇 |
2016年 | 33篇 |
2015年 | 35篇 |
2014年 | 48篇 |
2013年 | 55篇 |
2012年 | 45篇 |
2011年 | 67篇 |
2010年 | 55篇 |
2009年 | 72篇 |
2008年 | 54篇 |
2007年 | 71篇 |
2006年 | 68篇 |
2005年 | 33篇 |
2004年 | 46篇 |
2003年 | 37篇 |
2002年 | 21篇 |
2001年 | 28篇 |
2000年 | 24篇 |
1999年 | 32篇 |
1998年 | 26篇 |
1997年 | 32篇 |
1996年 | 20篇 |
1995年 | 17篇 |
1994年 | 17篇 |
1993年 | 7篇 |
1992年 | 12篇 |
1991年 | 7篇 |
1990年 | 9篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1986年 | 3篇 |
排序方式: 共有1170条查询结果,搜索用时 15 毫秒
91.
《Journal of Equine Veterinary Science》2014,34(11-12):1257-1262
Data on the feeding, management, and training schedules during the week before the competition were collected via a face-to-face survey of riders competing in dressage, show jumping, or eventing at 1* and 3* level competitions. Data were collected using a pro forma recording sheet, and measurements of horse height, weight, and body condition score (BCS) were also obtained. A total of 158 of 582 riders (and horses) were surveyed, providing a response rate of 27%. The mean height, weight, and median BCS of the horses were 162 ± 1 cm, 533 ± 5 kg, and 6 (interquartile range [IQR], 5–7), respectively. The majority of horses were at pasture, most (68%, 107 of 158) 24 hr/d and fed supplementary feed either once (42%, 67 of 158) or twice daily (54%, 86 of 158). The supplementary feed was predominately a commercial premix feed (90%, 142 of 157) with additional alfalfa chaff or ensiled chopped alfalfa. The horses were offered approximately 60 MJ digestible energy (DE)/d (33–86 MJ DE/d) from supplementary feed. The horses worked for a median of 6 d/wk (IQR, 5–6 d/wk) with one rest day. The median total time trained during the week was 200 minutes (135–265 minutes), which consisted of eight separate training activities. There was no difference in time spent on different activities between the disciplines. Individual training activities were 30–40 minutes, and the median number of competitions per month was 2 (IQR, 2–3). Training workload and pattern of work were similar to reports from other countries, with the exception that many riders regularly added a “hack out” after training. 相似文献
92.
An 8-week feeding experiment was conducted to investigate the effects of different dietary macronutrient level and feeding
frequency on the growth, feed utilization, and body composition of juvenile rockfish. Triplicate groups of fish (body weight
of 4.1 g) were fed the experimental diets containing either high levels of carbohydrate (HC, 35%), lipid (HL, 13%), or protein
(HP, 55%) at different feeding frequencies (twice daily, once daily, and once every 2 days). Weight gain was affected by feeding
frequency but not by dietary composition. Weight gain of fish fed the diets once every 2 days was significantly (P < 0.05) lower than that of other groups. Daily feed intake and energy intake were affected by both dietary composition and
feeding frequency. Daily feed intake of fish fed the HC diet was significantly (P < 0.05) higher than that of fish fed the HL and HP diets at the same feeding frequency. Feed efficiency and protein efficiency
ratio were affected by both dietary composition and feeding frequency and decreased with increasing feeding frequency in the
same dietary composition. Feed efficiency and protein efficiency ratio of fish fed the HC diet were significantly (P < 0.05) lower than those of fish fed the HL diet at the same feeding frequency. Whole-body lipid content of fish fed the
HL diet was significantly (P < 0.05) higher than that of fish fed the HC and HP diets at the same feeding frequency. These results indicate that an increase
of dietary lipid level compared with dietary carbohydrate level may have the advantage of a protein-sparing effect at same
feeding frequency, and a once-daily feeding regime is more effective than twice daily or one feeding every 2 days to improve
growth performance of juvenile rockfish grown from 4 to 21 g. 相似文献
93.
闽南-台湾浅滩渔场狗母鱼类食性的研究 总被引:2,自引:2,他引:2
本文对闽南一台湾浅滩渔场狗母鱼类(多齿蛇鲻、花斑蛇鲻和大头狗母鱼)的食料生物组成、摄食强度的季节变化以及消化器官与食性等方面进行了探讨。结果表明,这三种狗母鱼类都属于游泳动物食性的底层鱼类,而且是同种残食的中级肉食性鱼类,其食料生物组成比较简单,主要摄食鱼类和头足类,还兼食长尾类、短尾类和口足类。被捕食对象的大小,随着捕食对象(多齿蛇鲻或花斑蛇鲻)叉长的增加而增大。狗母鱼类周年均有摄食,多齿蛇鲻和花斑蛇鲻在产卵盛期(3—4月)摄食强度较高。它们的消化器官的形态结构与其肉食性相适应,多齿蛇鲻和花斑蛇鲻的消化器官和食性相近似,比大头狗母鱼的食性较凶猛。 相似文献
94.
合理调整我国人民的食物结构是提高全民族身体素质,推进社会文明进步,具有深远的战略意义的一项国策。调整国民食物结构是一个科学性,政策性很强,社会涉及面广,地区人群民食习惯差别大的极为复杂的动态系统工程。作者针对山西省情实际,从追朔我国饮食传统,膳食民习,食物资源及演变趋向探求,提出合理调整山西人民食物结构的策略与途径。 相似文献
95.
就兰科杓兰属3种、手参属1种、斑叶兰属1种野生花卉的分类地位、植物学特征、生态学习性、利用途径进行了简要记述. 相似文献
96.
97.
限制饲养对肉鸭生产性能和屠体品质的影响 总被引:2,自引:0,他引:2
选用1日龄樱桃谷肉鸭200只,随机分为两组,1个试验组,1个对照组,每组2个重复,每个重复50只。对照组1~6周自由采食,试验组1~3周自由采食,4~6周采用限制饲养(限量)。试验结果表明:6周龄时,试验组的饲料转化率比对照组提高了12.9%,差异显著(P<0.05),但日增重降低了9.13%,差异不显著(P>0.05);腹脂率降低34.2%,差异极显著(P<0.01);皮脂率降低15.1%,差异显著(P<0.05);瘦肉率提高了11.9%,差异不显著(P>0.05)。 相似文献
98.
在生产实践中采用青贮、氨化、热喷、酵母菌发酵和人工瘤胃发酵的方法处理农作物秸秆,将大大提高其饲用价值。 相似文献
99.
100.