全文获取类型
收费全文 | 41664篇 |
免费 | 2253篇 |
国内免费 | 4540篇 |
专业分类
林业 | 3241篇 |
农学 | 3329篇 |
基础科学 | 2142篇 |
4502篇 | |
综合类 | 18580篇 |
农作物 | 3139篇 |
水产渔业 | 1736篇 |
畜牧兽医 | 6925篇 |
园艺 | 2725篇 |
植物保护 | 2138篇 |
出版年
2024年 | 326篇 |
2023年 | 885篇 |
2022年 | 1951篇 |
2021年 | 1940篇 |
2020年 | 1864篇 |
2019年 | 1855篇 |
2018年 | 1282篇 |
2017年 | 1849篇 |
2016年 | 1432篇 |
2015年 | 2075篇 |
2014年 | 2197篇 |
2013年 | 2505篇 |
2012年 | 3347篇 |
2011年 | 3431篇 |
2010年 | 3234篇 |
2009年 | 2895篇 |
2008年 | 2774篇 |
2007年 | 2467篇 |
2006年 | 2032篇 |
2005年 | 1692篇 |
2004年 | 1072篇 |
2003年 | 840篇 |
2002年 | 1171篇 |
2001年 | 979篇 |
2000年 | 792篇 |
1999年 | 392篇 |
1998年 | 186篇 |
1997年 | 143篇 |
1996年 | 125篇 |
1995年 | 110篇 |
1994年 | 84篇 |
1993年 | 89篇 |
1992年 | 110篇 |
1991年 | 82篇 |
1990年 | 66篇 |
1989年 | 50篇 |
1988年 | 32篇 |
1987年 | 26篇 |
1986年 | 12篇 |
1985年 | 5篇 |
1984年 | 8篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 7篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1965年 | 1篇 |
1962年 | 11篇 |
1956年 | 12篇 |
1955年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
为今后奶牛改良工作成果的巩固和推广提供依据,对国家奶牛良种补贴项目在泾阳实施的效果与措施进行总结.结果表明:累计使用良种冷冻精液细管23.7万支,生产改良奶牛3.15万头,且已有1.1万头的优质母牛已正式进入产奶阶段.良种补贴后代奶牛的头胎日产奶量达到27 kg左右,比同期母亲日产奶量高2 kg~3 kg;生奶平均乳... 相似文献
982.
当今,养殖业面对的环保要求越来越高,且人类社会对畜禽产品的质量也是高度关注。本文从畜牧业污染产生的危害、治理思路、控污的具体措施以及健康的养殖模式展开分析,并做出一些对未来养殖业发展的预测,旨在为环保养殖提供参考与借鉴。 相似文献
983.
本试验旨在研究硬脂酰乳酸钠(SSL)对断奶仔猪生长性能、血清生化指标及养分表观消化率的影响。试验选择25日龄的断奶仔猪336头,按体重随机分为6组,每组7个重复,每个重复8头猪。各组仔猪饲粮中SSL添加水平分别为0(对照)、250、500、750、1 000和2 000 mg/kg,试验分2个阶段,每阶段21 d。试验测定仔猪生长性能,谷丙转氨酶、谷草转氨酶、总胆固醇等血清生化指标及能量、干物质、氮和粗脂肪表观消化率。结果表明:与对照组相比,1)饲粮中添加500、750和1 000 mg/kg SSL能显著降低仔猪第2阶段料重比(P0.05),添加1000 mg/kg SSL显著降低全期料重比(P0.05);2)饲粮中添加SSL有降低试验第42天仔猪血清谷草转氨酶、谷丙转氨酶活性,增加血清高密度蛋白胆固醇含量及高密度蛋白胆固醇/低密度蛋白胆固醇值的趋势,且当添加水平为2 000 mg/kg时差异达到显著水平(P0.05);3)饲粮中添加SSL能显著提高粗脂肪表观消化率(P0.05),并且有提高氮及能量表观消化率的趋势,当添加水平为2 000 mg/kg时差异达到显著水平(P0.05)。结果提示,饲粮添加SSL能降低仔猪料重比,提高饲料养分尤其是粗脂肪的表观消化率。 相似文献
984.
985.
青贮微生物及其对青贮饲料发酵品质影响的研究进展 总被引:1,自引:0,他引:1
青贮微生物在饲料发酵过程中起关键作用。无论是牧草表面附着的微生物还是外源添加的微生物菌剂在青贮发酵过程中对青贮微生物的群落结构及其演替过程都起着重要的作用,而青贮发酵过程中微生物的群落结构及其演替过程与代谢产物很大程度上影响着青贮饲料的发酵品质。本文阐述了青贮微生物群落结构,微生物在青贮过程中的演替及其对青贮饲料品质的影响。从目前研究结果来看,不同牧草及同种牧草生长在不同环境中其表面附着微生物存在很大差异。添加乳酸菌对提高青贮品质效果不稳定,还需了解牧草附着微生物特性决定是否需要接种乳酸菌以得到优质青贮饲料。 相似文献
986.
The objective of this study was to evaluate of the growth performance, serum biochemical indices, liver antioxidant parameters and ability of anti-infection with Aeromonas hydrophila by adding the fermented Chinese medicine by Bacillus Subtilis to the carp fish feed, and to find out the appropriate supplemental level of fermented Chinese medicine in diets. Carp fingerling with an initial body weight of (35±0.5) g were set up to 6 experimental diets supplemented with 0 (control group), 0.1‰, 0.5‰, 1‰, 2‰ and 3‰ fermented Chinese medicine for 56 days, respectively. Each group had 30 fish and set up 3 repetitions. After the feeding trail,the fish were challenged with Aeromonas hydrophila to calculate the relative percentage survival (RPS).The results showed as follows:Supplementing fermented traditional Chinese medicine by Bacillus subtilis, the weight gain rate (WGR), specific growth rate (SGR), condition factor (CF), the activities of lysozyme (LSZ), complement 3 (C3),total protein (TP),total anti-oxidation capacity (T-AOC),total superoxide dismutase (T-SOD) and catalase (CAT) in serum of common carp were enhanced at different degrees, while the feed coefficient (FCR)and malondialdehyde (MDA) in serum were declined at different degrees.When the fermented Chinese medicine supplemental levels were 2‰ and 3‰,the effects were significant (P<0.05)(except for C3, ALP and Cr).The experimental results of the virulence of common carp infected with pathogen Aeromonas hydrophila showed that,the fermented herbal could obviously improve the ability of anti-infection, the immune protective rate of the group with 2‰, 3‰ doses of the fermented Chinese medicine could reach 77.23% and 74.63%, respectively. From what had been discussed above, the group with 2‰ and 3‰ doses of the fermented Chinese medicine had significant effect on the growth performance, serum biochemical indices, liver antioxidant parameters and Aeromonas hydrophila anti-infection ability. Considering the cost of adding fermented Chinese medicine, the recommendations for the best additive quantity was 2‰. 相似文献
987.
WANG Jun LIU Xiao-fei JIA Ya-xiong GUO Jiang-peng LU Yong-qiang QI Zhi-guo CHANG Liang YANG Jian-jun XU Meng 《中国畜牧兽医》2017,44(7):2071-2078
This study was aimed to determine the effects of different crossbred combinations on fatting performance in beef cattle. Using single factor randomized block design, 30 bulls (health, similar weight and age) were chosen, Simmental cattle×Kerqin beef cattle (group A), Charolais cattle×Kerqin crossbred beef cattle (group B) and Kerqin beef cattle (group C) were divided into three groups with 10 bulls per group. After 95 d, the body weight, slaughter performance, meat quality and the economic benefits of fattening were measured. The results showed that there were no significant influence on dry matter intake among trials (P>0.05). The F/G, ethanolic extract (EE) of muscle in crossbred groups (groups A and B) were significant lower than group C (P<0.05). The weight of carcass, weight of meat, rate of carcass, and the weight of shank, plate, chine and rump in crossbred groups were significant higher than group C (P<0.05). There were no significant difference in content of amino acids among groups (P>0.05),and it had difference in the content of palmitoleic acid (PAA),stearic acid(SA) and linoleic acid (LA). In this trial, it had better fattening performance and the economic benefits in crossbred cattle groups than Kerqin beef group cattle, but the ethanolic extract and unsaturated fatty acids of muscle in Kerqin beef cattle were higher than the crossbred groups, and it had better fattening performance by crossbred. 相似文献
988.
The experiment was conducted to study the effects of yeast culture on growth performance, meat quality and intestinal microflora of broilers. A total of 432 1-day-old AA commercial broiler chicks with initial body weight of (41.73±0.15)g were randomly divided into 4 groups with 6 replicates per group and 18 broilers per replicate,receiving diets supplemented with 0,0.1%,0.2% and 0.3% yeast culture, respectively. The trial lasted for 42 days which was divided into two periods with 1 to 21 d and 22 to 42 d,respectively.The feed intake,body weight,death and culling rate were recorded in each period. At the end of the experiment,1 chickens in each replicate with the weight close to the average value were slaughtered after fasting for 12 h. The slaughter performance and intestinal microflora counts were determined.The results showed that compared with control group,the supplementation of 0.2% and 0.3% yeast culture significantly increased the body weight at 42 d and the average daily gain (ADG) during the whole trial (P< 0.05).The diet supplemented with 0.2% yeast culture significantly improved the ADG,decreased the F/G of broilers during 22 to 42 d (P< 0.05),and it also significantly increased the average daily feed intake (ADFI) and ADG (P< 0.05),decreased the F/G of the whole period (P< 0.05).Moreover,the supplementation of 0.2% yeast culture significantly decreased the drip loss of meat and the count of Escherichia coli (P< 0.05),and significantly increased the count of Bifidobacterium(P< 0.05). In summary, the supplementation of 0.2% yeast culture could significantly improve the growth performance and the muscle quality of broilers.The intestinal microflora in broiler cecum were effectively optimized after inclusion of yeast culture in the study. 相似文献
989.
990.
通过在三黄雏鸡日粮中添加高硒、高硒钴、高硒钴锌以及高硒钴锌铁4种紫花苜蓿草粉的试验,研究其对雏鸡生长和代谢的影响.结果表明在鸡饲料中添加5%~15%的4种高微牧草均可提高饲料报酬,提高雏鸡对饲料的利用和转化.其中,在鸡饲料中添加10%的高硒钴锌的苜蓿草粉,应用效果最好,添加后雏鸡的体重增加了150%,比对照提高了93.... 相似文献