全文获取类型
收费全文 | 14821篇 |
免费 | 889篇 |
国内免费 | 1269篇 |
专业分类
林业 | 792篇 |
农学 | 804篇 |
基础科学 | 1518篇 |
1039篇 | |
综合类 | 4851篇 |
农作物 | 371篇 |
水产渔业 | 1175篇 |
畜牧兽医 | 6056篇 |
园艺 | 134篇 |
植物保护 | 239篇 |
出版年
2024年 | 111篇 |
2023年 | 299篇 |
2022年 | 619篇 |
2021年 | 754篇 |
2020年 | 768篇 |
2019年 | 1016篇 |
2018年 | 501篇 |
2017年 | 826篇 |
2016年 | 898篇 |
2015年 | 733篇 |
2014年 | 909篇 |
2013年 | 848篇 |
2012年 | 1318篇 |
2011年 | 1157篇 |
2010年 | 896篇 |
2009年 | 823篇 |
2008年 | 738篇 |
2007年 | 758篇 |
2006年 | 604篇 |
2005年 | 481篇 |
2004年 | 327篇 |
2003年 | 283篇 |
2002年 | 182篇 |
2001年 | 162篇 |
2000年 | 150篇 |
1999年 | 125篇 |
1998年 | 104篇 |
1997年 | 110篇 |
1996年 | 89篇 |
1995年 | 64篇 |
1994年 | 64篇 |
1993年 | 52篇 |
1992年 | 41篇 |
1991年 | 41篇 |
1990年 | 25篇 |
1989年 | 30篇 |
1988年 | 23篇 |
1987年 | 23篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1956年 | 8篇 |
1955年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
为分析抗菌肽粗提物对肉鸡生长性能、粪便微生物菌群结构及经济效益的影响,试验选择体重相近的21日龄白羽肉鸡600只,随机分成4组,每组15个重复,每个重复10只,1组为空白对照组饲喂基础日粮,试验2、3、4组在基础日粮中分别添加1.0%、1.5%、2.0%的抗菌肽粗提物,试验期为21 d.结果表明:(1)试验2、3、4组... 相似文献
102.
通过蒸汽辅助重力泄油(Steam Assisted Gravity Drainage,SAGD)技术开采稠油时,采出液温度较高,对其进行热回收的节能潜力较高,油田采用热管式换热器回收采出原油的余热,将其作为工业或生活用热具有研究价值。考虑到现场空间要求和工程设备模块化的特点,利用U形管壳式换热器、螺旋板式换热器作为分离型热虹吸热管蒸发段和冷凝段,并建立复合式分离型热管模型,分析其换热性能、循环压降、充液率及换热能力。采用新疆油田油水二次换热区的分离型热管系统验证该模型,结果表明:复合式分离型热管计算模型可行;复合式热管具备U形管壳式换热器、螺旋板式换热器的优点,换热性能强,系统换热能力可以满足实际要求,有较好的环境适应性。 相似文献
103.
Yosuke SASAKI Satoshi SEKIGUCHI Ryoko UEMURA Masuo SUEYOSHI 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2016,78(2):333-335
This study compared the reproductive and growth performances of pigs before and after depopulation and
restocking after a foot-and-mouth disease outbreak in Japan. Data for the time period before and after
depopulation and restocking were obtained from three farrow-to-finish farms. As a result of depopulation and
restocking, hygiene levels were improved, and common infectious diseases, such as porcine reproductive and
respiratory syndrome and Aujeszky’s disease, remained undetected on the farms. Compared with before
depopulation, reproductive and growth performances improved after depopulation; the number of total pigs born
was higher, the postweaning mortality rate was lower, and the age at slaughter was lower
(P<0.05). In summary, depopulation and restocking improved the reproductive and growth
performances of pigs. 相似文献
104.
Effects of Medium-chain Triglyceride on Growth Performance and Serum Biochemical Indices in Broilers
HUANG Deng-gui LIAO Wen-de WEN Yuan-kun ZHUANG Yue-feng LIU Guo-qiang HUANG Xiao-liang HUANG Guan-qing 《中国畜牧兽医》2016,43(7):1761-1765
The study was conducted to investigate the effects of medium-chain triglyceride replacing the soybean oil in the basal diet on growth performance and serum biochemical indices of broilers.One hundred and forty four healthy,similar body weights AA broilers at the age of 14 days were randomly assigned to four groups with six replicates ger group and six broilers per replicate.Groups A,B,C and D were respectively fed with 0,0.6%,1.2% and 2% medium-chain triglyceride substituted the equivalent amount of soybean oil (using corn flour to balance the energy levels in each group) .The test lasted for 28 days and the indexes were measured once every two weeks.The results showed that the average daily gain and average daily feed intake of groups B,C and D were higher than that of group A,and the F/G was lower than group A.The average daily gain of groups C and D at 28 to 42 days old and group D at 14 to 42 days old were significantly higher than that of group A (P < 0.05).The serum glucose,total content of amino acid,total protein and albumin of groups B,C and D at age of 28 and 42 days old were higher than that of group A,while the serum triglyceride,total cholesterol and urea nitrogen levels were lower.The total cholesterol content at 42 days old and triglyceride concentrations at 28 days old of group C were significantly lower than those of group A (P < 0.05).The results indicated that medium-chain triglyceride could raise average daily gain and reduce the total cholesterol content and triglyceride concentrations of broilers,which were useful for improving the growth performance. 相似文献
105.
In order to study the tolerance dose of Kunming mice to montmorillonite as a mycotoxin adsorbent in diets,the experiment selected 60 healthy male Kunming mice with initial average body weight of (17±0.12)g,randomly divided them into 5 treatments with two replicates per group and 6 mice per replicate.Five experimental diets were added to 0 (control group),0.5%,1%,2% and 5% montmorillonite,respectively.After 30 days,the growth performance,nutrients apparent digestibility,serum biochemical indices and internal organization were tested to determine the tolerance dose of montmorillonite for Kunming mice.The results showed that the ADFI was significantly increased in 0.5% group (P< 0.05),while there were no significant differences in ADFI and ADG between 1% group and control group (P> 0.05),then the ADFI was significantly decreased with the increasing of montmorillonite supplemental level (P< 0.05).The ADG in 2% group had no significant difference when compared with the control group (P> 0.05),while significantly lower than that in 0.5% and 1% groups (P< 0.05).The apparent digestibility of DM,CP and EE showed no significant effect at any level of montmorillonite (P> 0.05).Serum ALT,AST activities and MDA content were gradually increased with the montmorillonite supplemental level increasing,and that in 1%,2% and 5% groups were significantly higher than that in control group (P< 0.05),but there were no significant differences between 0.5% group and control group (P> 0.05).Tissue sections showed that mice livers were damaged in varying degrees when the montmorillonite supplemental level was 5%.In conclusion,based on a comprehensive consideration of all indexes,it could be seen that the tolerance dose of the tested montmorillonite for Kunming mice was between 0.5% and 2% when mycotoxin contents in diets were in security range. 相似文献
106.
107.
108.
介绍了我国立式无筛饲料超微粉碎机的发展,简述立式无筛饲料超微粉碎机的组成、工作原理和优越性,分析质量检测及立式无筛饲料超微粉碎机技术的发展,展望制定行业标准的预期效果。 相似文献
109.
110.