全文获取类型
收费全文 | 4663篇 |
免费 | 536篇 |
国内免费 | 366篇 |
专业分类
林业 | 27篇 |
农学 | 65篇 |
基础科学 | 36篇 |
190篇 | |
综合类 | 986篇 |
农作物 | 57篇 |
水产渔业 | 10篇 |
畜牧兽医 | 4174篇 |
园艺 | 5篇 |
植物保护 | 15篇 |
出版年
2024年 | 36篇 |
2023年 | 114篇 |
2022年 | 168篇 |
2021年 | 280篇 |
2020年 | 233篇 |
2019年 | 243篇 |
2018年 | 133篇 |
2017年 | 171篇 |
2016年 | 160篇 |
2015年 | 147篇 |
2014年 | 274篇 |
2013年 | 297篇 |
2012年 | 340篇 |
2011年 | 302篇 |
2010年 | 255篇 |
2009年 | 236篇 |
2008年 | 225篇 |
2007年 | 238篇 |
2006年 | 237篇 |
2005年 | 191篇 |
2004年 | 143篇 |
2003年 | 138篇 |
2002年 | 106篇 |
2001年 | 117篇 |
2000年 | 124篇 |
1999年 | 107篇 |
1998年 | 79篇 |
1997年 | 57篇 |
1996年 | 43篇 |
1995年 | 47篇 |
1994年 | 36篇 |
1993年 | 39篇 |
1992年 | 40篇 |
1991年 | 33篇 |
1990年 | 38篇 |
1989年 | 48篇 |
1988年 | 10篇 |
1987年 | 15篇 |
1986年 | 12篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1982年 | 7篇 |
1980年 | 6篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1976年 | 2篇 |
1975年 | 6篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1956年 | 4篇 |
排序方式: 共有5565条查询结果,搜索用时 31 毫秒
31.
Kumiko TAKEDA Masahiro SATOH Shreeram P. NEOPANE Bahadur S. KUWAR Hari D. JOSHI Nanda P. SHRESTHA Hiroshi FUJISE Mariko TASAI Takahiro TAGAMI Hirofumi HANADA 《Animal Science Journal》2004,75(2):103-110
Dwarf Lulu cattle, the only Bos Taurus type of cattle in Nepal, are raised under severe environments in the mountainous zone of that country. In the present study, the body measurement traits, cytogenetic and molecular genetic characteristics of the Lulu cattle are investigated. Blood samples were collected from 31 animals in four villages (altitudes 2590–3550 m) in the southern part of Mustang. The Lulu cattle had a normal karyotype with 2n = 60, XY or XX. Only one male examined had a large submetacentric X‐chromosome and a small submetacentric taurine type Y‐chromosome. The mitochodrial DNA (mtDNA) genotypes were analyzed by PCR mediated restriction fragment length polymorphisms, displacement (D)‐loop region PCR mediated single strand conformation polymorphisms, and D‐loop region sequences. Many base substitutions were found in the D‐loop region, suggesting that the Lulu cattle originated from at least 10 maternal lines. Three types of mtDNA from these cattle were found, the Bos taurus type (n = 23), the Bos indicus type (n = 6), and the Bos grunniens type (n = 2). In the village at the lowest altitude, four of the five cows were of the Bos indicus type. These results indicated that mtDNA types of the Lulu cattle mostly belong to Bos taurus, but have been hybridized with Bos indicus cattle in lower‐elevation regions in their maternal lineage. 相似文献
32.
33.
秦川牛是我国优良的地方黄牛品种,其肉用性能非常突出,具有诱人的发展潜力.本文就秦川牛肉用性能开发的前景、制约秦川牛肉用性能发展的因素进行了分析,并提出了秦川牛发展对策. 相似文献
34.
西安荷斯坦奶牛群5个基因座位遗传多态性的PCR-RFLP分析 总被引:6,自引:0,他引:6
应用PCR-RFLP方法对西安荷斯坦牛的κ-en、β-lg、β-lg5′侧翼区、CSN1S2、IGFBP-3共5个基因座位进行了多态性分析。结果表明,在西安荷斯坦牛群中,没有发现携带CSN1S2^P等位基因的个体,其多态信息含量为0。κ-en基因座位呈现低度多态(PIC=0.2366),β-lg、β-lg5′侧翼区、IGFBP-3基因座位的多态信息含量分别为0.3168、0.3689、0.4439,均呈现中度多态。κ-en、β-lg、β-lg5′侧翼区、IGFBP-3、CSNIS2基因座位的杂合度和DNA多态度分别为0.2742、0.3947、0.4879、0.4891、0和0.0255、0.0116、0.0333、0.0112、0。而且,在西安荷斯坦牛群中,κ-en、β-lg、β-lg5′侧翼区、IGFBP-3共4个基因座位均处于Hardy-Weinberg平衡状态,CSN1S2基因座位处于纯合状态。 相似文献
35.
36.
37.
J. Schäler R. Wellmann J. Bennewitz G. Thaller D. Hinrichs 《Acta Agriculturae Scandinavica, Section A - Animal Sciences》2018,68(2):63-72
Recovering native uniqueness has major importance for breeds with historic introgression. The aim of the study was to estimate population genetic parameters for two local red cattle breeds from Northern Germany and to study possibilities to reverse introgression. Genealogical information consisted of 90,783 individuals for German Angler and 187,255 individuals for Red Dual-Purpose cattle breed, with additional information on sex, born, breed, status, and conventional breeding values. It is concluded that the native genetic contribution could be included as an additional trait in the total merit index in order to recover a part of the native genetic background. Native contributions should be estimated in the long term from marker data in order to account for Mendelian sampling. The maintenance of a sufficient genetic diversity of native alleles can be achieved by an advanced OCS with appropriate constraints. 相似文献
38.
39.
A survey of northern Victorian dairy farmers to investigate dairy calf management: colostrum feeding and management
下载免费PDF全文
![点击此处可从《Australian veterinary journal》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Objectives
To describe colostrum management practices carried out in northern Victorian dairy herds and to identify weaknesses in these areas that may affect calf health and welfare by comparing the results with the current industry recommendationsMethods
A questionnaire to obtain information about colostrum management and calf‐rearing practices was sent to commercial dairy farming clients of Rochester Veterinary Practice between June and September 2013. The questionnaire consisted of a general herd overview and colostrum harvesting practices.Results
The response rate was 39% (58/150). Many dairy producers were not meeting the current industry recommendations in the following areas: (1) time of removal calf from the dam, (2) relying on calf suckling colostrum from the dam to achieve adequate passive transfer, (3) failing to supplement calves with colostrum, (4) feeding inadequate volumes of colostrum, (5) delayed colostrum harvesting, (6) pooling of colostrum, (7) failing to objectively assess colostrum quality or relying on visual assessment and (8) storing colostrum for a prolonged periods of time at ambient temperatures.Conclusion
The results from this survey highlight the need for greater awareness of industry standards for colostrum management and feeding hygiene.40.
Noninferiority trial investigating the efficacy of a nonantibiotic intramammary therapy in the treatment of mild‐to‐moderate clinical mastitis in dairy cows with longer lasting udder diseases
下载免费PDF全文
![点击此处可从《Journal of veterinary pharmacology and therapeutics》网站下载免费的PDF全文](/ch/ext_images/free.gif)
M. Ziesch N. Wente Y. Zhang W. Zaremba S. Engl V. Krömker 《Journal of veterinary pharmacology and therapeutics》2018,41(1):11-21
A nonblinded, positively controlled, noninferiority trial was conducted to evaluate the efficacy of an alternative, nonantibiotic therapy with Masti Veyxym® to reduce ineffective antibiotic usage in the treatment of nonsevere clinical mastitis (CM) in cows with longer lasting udder diseases. The solely intramammary treatment with Masti Veyxym® (three applications, 12 hr apart) and the combined treatment with Masti Veyxym® and antibiotics as usual on the farm according to label of the respective product were compared with the reference treatment of solely antibiotic therapy. The matched field study was conducted on eight free‐stall dairy farms located in Eastern Germany. Cases of mild‐to‐moderate CM in cows with longer lasting high somatic cell counts in preceding dairy herd improvement test days and with previous CM cases in current lactation were randomly allocated to one of the three treatment groups. A foremilk sample of the affected quarter was taken before treatment and again approximately 14 days and 21 days after the end of therapy for cyto‐bacteriological examination. Primary outcomes were clinical cure (CC) and no CM recurrence within 60 days after the end of treatment (no R60). Bacteriological cure (BC) and quarter somatic cell count (QSCC) cure were chosen as secondary outcomes although low probabilities of BC and QSCC cure for selected cows were expected. The study resulted in the following findings: the pathogens mostly cultured from pretreatment samples were Streptococcus uberis, followed by Staphylococcus aureus and coagulase‐negative staphylococci. There were no significant differences between the two test treatments in comparison with the reference treatment regarding all outcome variables. The sole therapy with Masti Veyxym® resulted in a numerically lower likelihood of BC without significant differences to the reference treatment. The combined therapy group showed a numerically higher nonrecurrence rate than the two other treatment groups and noninferiority compared to the reference treatment was proven. Having regard to the selection criteria of cows in this study, the findings indicated that sole treatment with Masti Veyxym® in nonsevere CM cases may constitute an alternative therapy to reduce antibiotics. However, noninferiority evaluations were mostly inconclusive. Further investigations with a larger sample size are required to confirm the results and to make a clear statement on noninferiority. 相似文献