全文获取类型
收费全文 | 1777篇 |
免费 | 155篇 |
国内免费 | 86篇 |
专业分类
林业 | 85篇 |
农学 | 98篇 |
基础科学 | 6篇 |
55篇 | |
综合类 | 563篇 |
农作物 | 83篇 |
水产渔业 | 121篇 |
畜牧兽医 | 424篇 |
园艺 | 48篇 |
植物保护 | 535篇 |
出版年
2024年 | 8篇 |
2023年 | 45篇 |
2022年 | 76篇 |
2021年 | 77篇 |
2020年 | 80篇 |
2019年 | 90篇 |
2018年 | 68篇 |
2017年 | 85篇 |
2016年 | 74篇 |
2015年 | 79篇 |
2014年 | 92篇 |
2013年 | 86篇 |
2012年 | 134篇 |
2011年 | 126篇 |
2010年 | 94篇 |
2009年 | 111篇 |
2008年 | 90篇 |
2007年 | 87篇 |
2006年 | 86篇 |
2005年 | 52篇 |
2004年 | 63篇 |
2003年 | 42篇 |
2002年 | 30篇 |
2001年 | 28篇 |
2000年 | 38篇 |
1999年 | 32篇 |
1998年 | 27篇 |
1997年 | 18篇 |
1996年 | 15篇 |
1995年 | 14篇 |
1994年 | 11篇 |
1993年 | 9篇 |
1992年 | 7篇 |
1991年 | 11篇 |
1990年 | 7篇 |
1989年 | 12篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1981年 | 1篇 |
1956年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有2018条查询结果,搜索用时 31 毫秒
91.
圆柏枯梢病病原菌的研究 总被引:1,自引:0,他引:1
圆柏枯梢病近年来呼和浩特地区一些苗圃的圆柏上发生严重。经病原菌分离培养,形态特征观察及致病性测定表明该病是由松色二孢菌Dipodia piea Kickx危害所致。其潜育期为7-10d,病原菌生长和孢子萌发最适温度为22℃,相对湿度在90%以上,在散射光下萌发最好。葡萄糖、蔗糖、麦芽糖为该菌纯培养的适宜碳源。 相似文献
92.
93.
【目的】研究引起新疆奇台窖藏马铃薯发生病害的病原种类,为新疆马铃薯窖藏病害的科学防治提供依据。【方法】2019年3月采集新疆奇台农场3个大窖病薯(大西洋品种)块茎。采用组织分离法、结合显微形态观察和柯赫氏法则、结合16S rDNA、ITS等鉴定方法,分离得到马铃薯窖藏病害的病原菌。【结果】从病薯中总计分离出12株菌株,其中致病菌有致病性尖孢镰刀菌(Fusarium oxysporum)、虱状赤霉(Gibberella pulicaris)、白地霉(Geotrichum candidum)。【结论】 致病性尖孢镰刀菌(Fusarium oxysporum)和虱状赤霉(Gibberella pulicaris)的致病性较强;由白地霉(Geotrichum candidum)引起的马铃薯病害在国内为首次报道。 相似文献
94.
95.
Estimation of milk production losses due to sub-clinical mastitis in dairy cattle in Costa Rica 总被引:1,自引:0,他引:1
Five dairy farms, situated on the slopes of the volcano Poás in the pre-mountain cloud forest ecological zone, Alajuela and Heredia Provinces, Costa Rica, provided data for estimation of the production losses due to sub-clinical mastitis. Within the same farm, cows with proven sub-clinical mastitis were matched with cows without signs of sub-clinical mastitis, according to breed, lactation number and days in lactation. A total of 529 cows were detected with sub-clinical mastitis, of which only 200 could be paired with control cows free of mastitis; each pair was used only once.
Crude milk production losses per cow with sub-clinical mastitis were estimated at 1.56 kg day−1for daily milk yield. Milk production loss per affected quarter due to sub-clinical mastitis was estimated to be 17.6% on average. The decrease in milk production in heifers with sub-clinical mastitis did not differ significantly from the decrease in production in older cows. No significant difference in milk production loss was detected when the data were stratified on parity or the number of quarters affected. 相似文献
96.
97.
病原菌孢子悬浮液经人工接种可侵染稗、高梁、玉米和大麦,但不侵染水稻、小麦和小米.病菌的培养滤液稀释液对稗、高粱、小米表现毒性,对水稻、小麦、玉米、大麦不表现毒性.用培养滤液配成的孢子悬浮液接种2叶期稗苗.10d 后最高死苗率为60.5%,病情指数为86.63. 相似文献
98.
Valérie?VasseurEmail author Patrice?Rey Estelle?Bellanger Yves?Brygoo Yves?Tirilly 《European journal of plant pathology / European Foundation for Plant Pathology》2005,112(4):301-310
Pythium group F is a ubiquitous, though minor, pathogen in several soilless and soil cultures; investigations were carried out to analyze different regions of the DNA and better understand the nature of this group. Fourty-two isolates were obtained from a variety of plants (cucumber, lettuce, tomato) grown in soil or soilless cultures collected in various countries (Canada, Denmark, France, Norway, Sweden and United Kingdom). All Pythium group F isolates displayed amplified ITS1-5,8S-ITS2 ribosomal DNA region (rDNA) of similar length, whereas polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) revealed that, among the seven enzymes used, polymorphism was only identified with Hin6I. After cloning of ITS1-5,8S-ITS2 rDNA region from Pythium group F isolates that displayed restriction polymorphism patterns with Hin6I, comparisons of sequence and restriction mapping data showed a slight variation consisting in a single base change. Inter Simple Sequence Repeat (ISSR)-PCR method was also used to obtain data related to the entire genome and not only to a single DNA region. It identified repeated motifs in the genome of Pythium group F isolates. Two primers (CAC)5 and (CCA)5 detected polymorphism, and isolates were classified among 11 molecular clusters. The genetic diversity of this group was not correlated with the geographical locations or the host plants from which the isolates originated. Polymorphism of Pythium group F isolates pointed out by ISSR is discussed 相似文献
99.
Reduced Milk Production in Udder Quarters with Subclinical Mastitis and Associated Economic Losses in Crossbred Dairy Cows in Ethiopia 总被引:2,自引:1,他引:1
Mungube EO Tenhagen BA Regassa F Kyule MN Shiferaw Y Kassa T Baumann MP 《Tropical animal health and production》2005,37(6):503-512
The objective of the study was to estimate the losses associated with subclinical mastitis (SCM) in crossbred dairy cows in
the Central Highlands of Ethiopia. A split udder investigation was performed with 30 cows to determine production losses associated
with SCM. Each quarter of the study cows was examined using the California Mastitis Test (CMT) and quarter milk production
was measured over a period of 8 days. Production losses were determined for different CMT scores by comparing production of
quarters with CMT score 0 to quarters with CMT scores trace, 1, 2 and 3, respectively. Using data from a recently published
study, economic losses were determined for different farm sizes and production subsystems by multiplying the prevalence of
the respective CMT scores with the production losses associated with these CMT scores. Mean quarter milk production was 0.82
+ 0.40 kg per milking in the split udder trial. Milk production was reduced by 1.2%, 6.3%, and 33% in quarters with CMT scores
1+, 2+, and 3+, respectively. Using data from the published study, a quarter with SCM lost an average of 17.2% of its milk
production. Production losses associated with SCM were estimated at 5.6% for the Addis Ababa Milk Shed. Stratified losses
were highest (9.3%) in urban dairy farms (UDF) and small-scale farms (6.3%). The estimates of the financial losses ranged
from US$29.1 in dairy herds in secondary towns (DHIST) to US$66.6 in UDF. A total loss of US$38 was estimated for each cow
per lactation. Reducing mastitis in UDF (highest prevalence) to the level of DHIST (lowest prevalence) could reduce the loss
by US$35. As this does not include costs associated with treatment or culling of diseased cows, this figure probably underestimates
the possible benefits of control measures. 相似文献
100.
: Dry cow antibiotic therapy is used to eliminate existing intramammary infections and to prevent new infections in the dry period. It is implemented as part of a total management system known as the 'Five-Point Plan' for mastitis control. Recent public concerns over the widespread prophylactic use of antibiotics, coupled with an increasing interest in organic farming, have lead to a re-evaluation of the treatment of cows at drying-off. As a result, attention has focussed on the use of novel alternatives to antibiotic therapy at the end of lactation. One such therapy involves the application of a non-antibiotic bismuth-based intramammary teat seal designed for use in cows with low cell counts at the end of lactation. Like the keratin plug that forms naturally in teats of cows that have been dried-off, teat seal forms a physical barrier to invading pathogens. To date, a number of independent studies have shown that teat seal is as effective as traditional dry cow antibiotic products in preventing the occurrence of new infection during the dry period in cows with somatic cell counts of ≤200,000 cells ml-1 at drying-off. This paper reviews the efficacy of teat seal in preventing dry period mastitis in both conventional and organic dairying systems. 相似文献