全文获取类型
收费全文 | 329283篇 |
免费 | 17845篇 |
国内免费 | 679篇 |
专业分类
林业 | 24748篇 |
农学 | 14254篇 |
基础科学 | 3012篇 |
47182篇 | |
综合类 | 47656篇 |
农作物 | 17555篇 |
水产渔业 | 18272篇 |
畜牧兽医 | 142483篇 |
园艺 | 6562篇 |
植物保护 | 26083篇 |
出版年
2019年 | 3753篇 |
2018年 | 4332篇 |
2017年 | 4765篇 |
2016年 | 5046篇 |
2015年 | 4525篇 |
2014年 | 5877篇 |
2013年 | 16614篇 |
2012年 | 8127篇 |
2011年 | 10506篇 |
2010年 | 8062篇 |
2009年 | 8432篇 |
2008年 | 9808篇 |
2007年 | 8932篇 |
2006年 | 9384篇 |
2005年 | 8630篇 |
2004年 | 8451篇 |
2003年 | 8169篇 |
2002年 | 7647篇 |
2001年 | 8851篇 |
2000年 | 8516篇 |
1999年 | 7309篇 |
1998年 | 4419篇 |
1997年 | 4475篇 |
1996年 | 4221篇 |
1995年 | 4943篇 |
1994年 | 4427篇 |
1993年 | 4094篇 |
1992年 | 6220篇 |
1991年 | 6595篇 |
1990年 | 6394篇 |
1989年 | 6313篇 |
1988年 | 5755篇 |
1987年 | 5865篇 |
1986年 | 5947篇 |
1985年 | 5953篇 |
1984年 | 5244篇 |
1983年 | 4824篇 |
1982年 | 3669篇 |
1981年 | 3470篇 |
1980年 | 3396篇 |
1979年 | 4655篇 |
1978年 | 4060篇 |
1977年 | 3547篇 |
1976年 | 3316篇 |
1975年 | 3311篇 |
1974年 | 4037篇 |
1973年 | 4074篇 |
1972年 | 3823篇 |
1971年 | 3629篇 |
1970年 | 3488篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
971.
Ohne Zusammenfassung 相似文献
972.
973.
974.
J. Jablonowski 《Journal of pest science》1925,1(2):18-19
Ohne Zusammenfassung 相似文献
975.
976.
977.
M. P. Reche P. A. Jimnez F. Alvarez J. E. García de los Ríos A. M. Rojas P. De Pedro 《Zoonoses and public health》2003,50(1):42-44
A total of 595 faecal samples from raptorial birds, either captive or free‐living, residing in GREFA Wildlife Hospital were bacteriologically examined using various selective media and an Automated Diagnostic Assay System for Salmonella detection. Serotype and phage type of the strains identified as Salmonella was determined. In the captive group, of the 285 samples examined, 21 (7.36%) were positive for Salmonella. Serotyping revealed that most of the individuals were infected by Salmonella serotype Havana. This result suggested that there could be a source of contamination in the Hospital although it could not be established. In the wild free‐living group, over 310 samples examined (4.19%) were positive for Salmonella. The Salmonella isolates showed a major variety of serotypes: Enteritidis, Adelaide, Brandenburg, Newport, Typhimurium, Hadar, Saintpaul and Virchow. Most of them are similar to those commonly described in isolates from human and domestic animals. These results indicate that wild birds could be involved in the dissemination of Salmonella in humans or domestic animals or vice versa. 相似文献
978.
979.
Guidi A. Iannone G. Castigliego L. Gianfaldoni D. 《Veterinary research communications》2004,28(1):193-196
Veterinary Research Communications - 相似文献
980.
A porcine in vitro fertilization (IVF) system and seminal quality parameters of frozen–thawed boar semen were used to assess the effectiveness of two different thawing rates of frozen boar semen, and to address the question of whether differences between fertility of ejaculates could be predicted in a limited field trial. In the first experiment, two thawing procedures were analysed (37°C, 30 s; 50°C, 12 s) and no differences in sperm quality were found. However, when the procedure was 50°C, 12 s the IVF results showed a higher number of sperm per penetrated oocyte and a near 10 points higher rate of pronuclear formation. In the second experiment, the fertility results obtained in the limited field trial show to be efficient enough for application in a commercial use, especially for three of the employed boars (fertility ≥80%). In this limited study, the conventional seminal parameters are not accurate enough to discriminate good and bad boars in relation to fertility. On the contrary, parameters of in vitro penetrability are more precise to predict subsequent fertilities. As conclusion, the IVF fertilization system seems to be a good tool to evaluate the quality of frozen–thawed boar semen previous to its commercial way, to verify the bank semen storage quality and a good way to assay new sperm freezing procedures, as it is the more precise evaluating method in estimating the potential fertilizing ability. 相似文献