全文获取类型
收费全文 | 6980篇 |
免费 | 446篇 |
国内免费 | 146篇 |
专业分类
林业 | 373篇 |
农学 | 394篇 |
基础科学 | 145篇 |
1134篇 | |
综合类 | 993篇 |
农作物 | 345篇 |
水产渔业 | 457篇 |
畜牧兽医 | 2918篇 |
园艺 | 209篇 |
植物保护 | 604篇 |
出版年
2023年 | 53篇 |
2022年 | 121篇 |
2021年 | 142篇 |
2020年 | 195篇 |
2019年 | 164篇 |
2018年 | 194篇 |
2017年 | 237篇 |
2016年 | 169篇 |
2015年 | 155篇 |
2014年 | 224篇 |
2013年 | 357篇 |
2012年 | 361篇 |
2011年 | 395篇 |
2010年 | 309篇 |
2009年 | 277篇 |
2008年 | 358篇 |
2007年 | 300篇 |
2006年 | 273篇 |
2005年 | 253篇 |
2004年 | 211篇 |
2003年 | 196篇 |
2002年 | 234篇 |
2001年 | 195篇 |
2000年 | 171篇 |
1999年 | 148篇 |
1998年 | 61篇 |
1997年 | 52篇 |
1996年 | 51篇 |
1995年 | 57篇 |
1994年 | 52篇 |
1993年 | 70篇 |
1992年 | 89篇 |
1991年 | 88篇 |
1990年 | 90篇 |
1989年 | 84篇 |
1988年 | 54篇 |
1987年 | 68篇 |
1986年 | 57篇 |
1985年 | 60篇 |
1984年 | 66篇 |
1983年 | 56篇 |
1982年 | 59篇 |
1980年 | 37篇 |
1979年 | 45篇 |
1978年 | 49篇 |
1977年 | 47篇 |
1976年 | 50篇 |
1974年 | 43篇 |
1972年 | 37篇 |
1969年 | 46篇 |
排序方式: 共有7572条查询结果,搜索用时 15 毫秒
41.
1. Differences were found among eight populations of White Plymouth Rock pullets in the frequency of broken eggs.
2. The shells of such eggs were thinner than those of intact eggs in seven of the populations.
3. The number of defective eggs, the specific gravity of the eggs, and the percentage hen‐day egg production of normal eggs were significantly correlated within populations with the incidence of broken eggs.
4. No significant correlations were found within populations between the incidence of egg breakage and either egg weight, body weight, or shank length. 相似文献
42.
43.
44.
A CELO-type adenovirus (AV) isolated from fowls with respiratory disease was inoculated experimentally into the tracheas of young birds. No symptoms referable to respiratory infection were evident. Post mortem examination between days 2 and 5 after inoculation revealed pneumonia involving up to 30 per cent of the surface of the lungs. Histologically, a focal to diffuse interstitial lymphocytic infiltration and bronchiolar degeneration were present. Concurrent infections with a mild strain of infectious laryngotracheitis virus (ILT) failed to enhance the pathogenicity of either the AV or ILT infections. 相似文献
45.
Nicolas Rose Alain Abhervé-Guéguen Gérald Le Diguerher Eric Eveno Jean-Pierre Jolly Philippe Blanchard Aurélie Oger André Jestin François Madec 《Livestock Production Science》2005,95(3):177-186
The aim of this study was to determine the potential risk factors for PMWS at the individual pig level and assess the effect of the Pietrain paternal genetic background of the animals in a cohort study. The survey was set up in four PMWS-affected farms with 2 repetitions (batches) per farm. A representative sample of 60 pigs per batch, stratified according to the paternal genetic background (Pietrain: yes vs. no), was randomly selected after farrowing. The representative cohort was divided into 8 batches and the pigs were individually monitored from birth to slaughter. Survival analysis was used to determine the factors related to the time to PMWS. The litter-cluster effect was taken into account using the marginal Cox model (robust estimation of the covariance matrix) and the gamma shared frailty model which were compared.No protective effect of the Pietrain breed on the time to PMWS and the proportion of affected pigs in the offspring was found in this study. Piglets showing low circovirus type 2 (PCV2) titres at 7 weeks-old with no subsequent seroconversion and piglets from PCV2 negative sows were most likely to be affected by PMWS (HR=7.0 and 2.8, respectively). Active infection of the pregnant dams with parvovirus was related to an increased risk of PMWS in the offspring (HR=2.3). Neck injuries due to poorly performed injections in the dams were associated with an increased risk of PMWS with the marginal model (HR=2.1). Oxytocin injection (dams) during farrowing was protective against PMWS in the offspring (HR=0.6). 相似文献
46.
47.
48.
菜豆萎蔫病菌的血清检测鉴定技术研究 总被引:2,自引:0,他引:2
本研究对我国一类检疫性有害生物菜豆萎蔫病菌(Curtobacteriumflacumfa-cienspv.flacumfaciens,Cf)进行血清检测鉴定技术的研究。试验中制备了抗Cf的血清,应用抗0020,0237,0238菌株的抗血清及其FITC标记的抗体进行间接和直接免疫荧光染色试验(IF/IF)。通过对19个Cf菌株和其它6个属14个种的植物病原细菌20个菌株的测定,结果发现约50%的Cf菌株为强阳性反应,且与Cf种下致病变种也有强阳性交叉反应。由于单个血清检测易产生假阴性反应,故将三种血清1∶1∶1混合后进行IF试验,结果表明与所有的Cf菌株反应,且与Rfa和Cmt有弱阳性反应。对含104~107cfu/ml细菌及30g种子含1粒人工接种种子的种子抽提液均能检测到典型的阳性细胞,血清检测的灵敏度为4.5×104cfu/ml,可用于种子的检测。本研究还进行了初步的免疫荧光菌落染色(IFC)试验 相似文献
49.
Increasing interest in a longer preservation of diluted boar sperm raises questions in the field concerning the choice of the extender. The aim of this study was to evaluate the longevity of boar sperm extended in currently used commercial semen extenders. Three long-term extenders and two short-term extenders were compared for different semen quality parameters that can be assessed under routine laboratory conditions. Sperm morphology, motility, pH and bacteriological contamination were investigated during a 7-day period. The number of dead spermatozoa did not differ significantly among the extenders (p > 0.05). Sperm motility was not only related with storage period but most of all with pH, especially in long-term extenders. Differences between the different extenders were prominent (p < 0.05); the sperm preserved in only one long-term extender showed good motility during the whole test period. In all cases, the pH of the extended semen increased by 0.3-0.5 in the first days of storage and was significantly correlated with a decrease in motility. Bacteriological quality had no significant influence on motility or pH of the semen. In conclusion, we can state that in both short-term extenders and in only one long-term extender, sperm longevity, as evaluated by the parameters used in this study, was sufficient during the preservation period. To preserve the quality of diluted boar semen during long-term storage, the choice of the long-term extender is important. In addition, the monitoring of the pH of extended boar semen in our study emphasizes the importance of the buffering capacity of semen extenders. 相似文献
50.
An improved vitrification protocol for equine immature oocytes,resulting in a first live foal
下载免费PDF全文
![点击此处可从《Equine veterinary journal》网站下载免费的PDF全文](/ch/ext_images/free.gif)