全文获取类型
收费全文 | 16846篇 |
免费 | 815篇 |
国内免费 | 1022篇 |
专业分类
林业 | 1436篇 |
农学 | 1141篇 |
基础科学 | 679篇 |
1953篇 | |
综合类 | 7015篇 |
农作物 | 1267篇 |
水产渔业 | 574篇 |
畜牧兽医 | 2922篇 |
园艺 | 957篇 |
植物保护 | 739篇 |
出版年
2024年 | 121篇 |
2023年 | 277篇 |
2022年 | 517篇 |
2021年 | 616篇 |
2020年 | 740篇 |
2019年 | 746篇 |
2018年 | 389篇 |
2017年 | 520篇 |
2016年 | 786篇 |
2015年 | 631篇 |
2014年 | 990篇 |
2013年 | 1123篇 |
2012年 | 1273篇 |
2011年 | 1302篇 |
2010年 | 965篇 |
2009年 | 1012篇 |
2008年 | 857篇 |
2007年 | 894篇 |
2006年 | 783篇 |
2005年 | 657篇 |
2004年 | 491篇 |
2003年 | 409篇 |
2002年 | 338篇 |
2001年 | 285篇 |
2000年 | 293篇 |
1999年 | 246篇 |
1998年 | 195篇 |
1997年 | 182篇 |
1996年 | 163篇 |
1995年 | 158篇 |
1994年 | 111篇 |
1993年 | 144篇 |
1992年 | 87篇 |
1991年 | 95篇 |
1990年 | 77篇 |
1989年 | 54篇 |
1988年 | 45篇 |
1987年 | 45篇 |
1986年 | 16篇 |
1985年 | 13篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1976年 | 2篇 |
1956年 | 4篇 |
1955年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
171.
A 3 × 2 factorial design with growing dairy-breed bulls was used to study the effects on animal performance of (1) proportion of concentrate (rolled barley) in the diet, and (2) inclusion of rapeseed meal (RSM) in the barley-based concentrate in a total mixed ration (TMR). The interactions between concentrate proportion and RSM supplement were also examined.Three feeding experiments comprised in total of 84 Finnish Ayrshire bulls and 6 Friesian bulls. The bulls were fed TMR ad libitum. The three concentrate proportions were 300 (L), 500 (M) and 700 (H) g/kg dry matter (DM), fed without RSM (RSM−) or with RSM (RSM+). Rapeseed meal was given so that the crude protein (CP) content of the concentrate was raised to 160 g/kg DM in the RSM+ diets. In the RSM− diets the CP content of the concentrate was 128 g/kg DM, so the CP content increased 25% with RSM supplementation. Increasing the proportion of concentrate led to a linear improvement in daily live weight gain (LWG) (P < 0.05), but there were no significant treatment differences in the DM intake (kg/d). Increasing the proportion of concentrate also led to significantly higher CP (P < 0.001) and phosphorus (P) (P < 0.001) supply and significantly improved DM and organic matter (OM) digestibility (P < 0.001). However, the digestibility of neutral detergent fibre (NDF) decreased (P < 0.001) as the proportion of concentrate increased. The feed conversion rate (kg DM/kg LWG) decreased significantly with increasing concentrate proportion (P < 0.001). Rapeseed meal supplement had no effect on animal performance, but the supply of CP (P < 0.01) and P (P < 0.001) was higher when RSM was included in the diet. The CP (P < 0.001) and NDF (P < 0.05) digestibilities were also higher for the RSM+ diets than for the RSM− diets. Because RSM at the concentration used did not affect animal performance, there is no reason to use RSM supplementation for finishing dairy bulls when there is good quality grass silage and barley-based concentrate in the TMR ration. This study also shows that there is a need to update the Finnish feeding recommendations for dairy-breed growing bulls, and extra calculations are needed for the energy and protein supply of growing dairy bulls. 相似文献
172.
用压力传感器产气技术评定玉米秸秆添补苜蓿的组合效应 总被引:3,自引:0,他引:3
采用压力传感器体外产气技术,研究了玉米秸秆添补不同比例0(AH0)、20%(AH20)、40%(AH40)、60%(AH60)、80%(AH80)与100%(AH100)苜蓿(AH)在产气量上的组合效应。各组的组合效应均在24h达到最大值,24h后则随培养时间的延长而下降,但只有AH40组,亦即当苜蓿添加比例占"玉米秸秆-苜蓿"组合的40%时达到显著水准(P<0.05),且以AH40组下降较慢,在48h仍达到显著水准(P<0.05)。就单一的产气指标而言,玉米秸秆添补苜蓿的比例以占整个日粮总量的40%为宜。 相似文献
173.
《The Journal of Applied Poultry Research》2007,16(4):529-536
The objective of this study was to evaluate the effects of different molting methods on postmolt production, plasma corticosterone levels, and antibody production to SRBC for the welfare of laying hens. This experiment was conducted with 120 IGH-type Brown laying hens (70 wk of age), randomly divided into 3 experimental groups. The hens in one group were fed a whole-grain barley diet during the first 10 d (WB diet). On d 11, hens consumed 100 g of layer diet/d until d 28. In the second group, hens were fed a Zn diet containing 10,000 mg/kg of Zn as ZnO for 10 d (Zn diet). Hens were then provided 100 g of a layer diet from d 11 to 28. In the third group, feed was withdrawn for 10 d, and on d 11 hens were fed a cracked corn diet ad libitum until d 28 (California method; CAL diet). Hens in all groups were returned to the layer diet ad libitum on d 29. Egg weight was lower in the Zn treatment than in the other treatments. Feed intake and plasma corticosterone levels were higher and antibody production was lower in the CAL treatment than in the WB and Zn groups. The FCR was better in the WB than in the Zn group. Mortality, egg production, and egg quality were not significantly different among the molting methods. As a result, the WB molting program was the best method for postmolt production among the programs examined. 相似文献
174.
175.
中草药、益生素和抗生素对猪生长性能和免疫功能的影响比较试验 总被引:1,自引:0,他引:1
本试验旨在比较中草药、益生素和抗生素对生长猪生产性能和免疫功能的影响。试验选取15kg左右的杜×长×大三元杂交猪90头,随机分为抗生素组、0.2%益生素组和0.2%中草药组,每组3个重复,每个重复10头猪,试验时间28d。结果表明:(1)与抗生素组相比,益生素及中草药组的日增重提高、料重比降低(P>0.05);(2)中草药组的IgG、IgM、IgA、C3、C4含量和益生素组的IgG含量均显著提高(P<0.05)。结论:在生长猪日粮中添加0.2%益生素或中草药能够促进动物生长,提高免疫功能,效果优于抗生素。 相似文献
176.
Grimaud P Mpairwe D Chalimbaud J Messad S Faye B 《Tropical animal health and production》2007,39(3):217-227
A survey was carried out on milk production and reproductive performance of dairy cattle: 24 farms, with a total of 900 animals
and distributed in four agro-ecological zones, were visited every 15 days over 18 months. Cows were fed on natural pastures
as the only source of feed, and animal performance was dependent on the season and exhibited a dramatic drop in dry spells.
Numeric productivity indices integrating productive performance for settler’s, multipurpose, crop–livestock integrated and
modern farms were 0.56, 0.74, 0.69 and 0.63, respectively. Milk productivity was higher on modern farms (6.7 L/cow per day)
than in the other systems, and higher with Holstein-Friesian cows (7.7 L/cow per day) than with indigenous cattle (1.8 L/cow
per day) or crossbred animals (3.7 L/cow per day). This paper speculates on the opportunity to improve the genetic potential
of indigenous cattle, concomitantly with the efforts to adapt exotic cattle to a mountainous equatorial environment. 相似文献
177.
不同储存年限老芒麦种子种带真菌检测及致病性测定 总被引:2,自引:0,他引:2
对来自青海的5个不同收获年份的老芒麦种样进行了系统的种带真菌研究;测定了12种分离率大于1%的种带真菌对老芒麦种子萌发和幼苗生长的影响。结果表明,种样发芽率为56%~80%,S2发芽率最高,达到80%,显著高于S1和S5(P<0.05);种样带菌率为24%~38%,随储藏时间延长呈下降趋势,S5带菌率最高,达到38%,显著高于其他种样(P<0.05);共鉴定出老芒麦种带真菌15属17种,真菌分离率为0.25%~8.75%,其中青霉和曲霉是老芒麦最常见的种带真菌,在5个种样上均被分离得到;燕麦镰孢、串珠镰孢、镰孢菌1、离蠕孢和德氏霉5种真菌是老芒麦最主要的致病真菌,均显著地降低了老芒麦种子的萌发、抑制了幼苗的生长、降低了幼苗的生物量(P<0.05);细交链孢对种子的萌发没有显著抑制作用(P>0.05),但是显著地降低了幼苗的长度和干物质产量(P<0.05)。皮思霉、离蠕孢、曲霉3种真菌显著延长了老芒麦种子平均萌发时间,而燕麦镰孢则显著地缩短了种子平均发芽时间(P<0.05)。 相似文献
179.
Chemical composition, in vitro digestibility and gas production of straw from four different varieties of Kabuli chickpea (Cicer arietinum) were studied. Kinetics of fermentation of straws from 19 different accessions of chickpea was also evaluated using gas production technique. Significant difference (p < 0.05) was observed in the yield of straw [from 1041 to 1174 kg dry matter (DM)/ha] from different varieties. The proportion of seed/straw from different varieties varied from 0.61 to 0.93. Crude protein, neutral detergent fibre and acid detergent fibre content of straw ranged from 28.1 to 35.8, 598.6 to 645.4 and 459.2 to 473.4 g/kg DM respectively. Organic matter digestibility was different (p < 0.05) among varieties and varied from 471.4 to 535.5 g/kg DM. Potential gas production (A), the rate constants (c and d) and lag times of straws from different chickpea varieties were not different (p > 0.05). However, the rate constants (c and d) and lag times were different (p < 0.05) among accessions. Potential gas production (A) differed (p < 0.05) approximately twofold among different accessions. The results emphasized that in any evaluation of chickpea varieties or accessions, where straw of this legume seed is used as an animal feed, not only seed yield but also yield and quality of straw should be taken into consideration. 相似文献
180.