全文获取类型
收费全文 | 85820篇 |
免费 | 4630篇 |
国内免费 | 101篇 |
专业分类
林业 | 3715篇 |
农学 | 2283篇 |
基础科学 | 518篇 |
9788篇 | |
综合类 | 16504篇 |
农作物 | 3545篇 |
水产渔业 | 3984篇 |
畜牧兽医 | 44217篇 |
园艺 | 1031篇 |
植物保护 | 4966篇 |
出版年
2019年 | 861篇 |
2018年 | 1223篇 |
2017年 | 1339篇 |
2016年 | 1195篇 |
2015年 | 1023篇 |
2014年 | 1353篇 |
2013年 | 2912篇 |
2012年 | 2460篇 |
2011年 | 3060篇 |
2010年 | 1901篇 |
2009年 | 1985篇 |
2008年 | 3061篇 |
2007年 | 2826篇 |
2006年 | 2728篇 |
2005年 | 2581篇 |
2004年 | 2428篇 |
2003年 | 2531篇 |
2002年 | 2271篇 |
2001年 | 2467篇 |
2000年 | 2515篇 |
1999年 | 1959篇 |
1998年 | 797篇 |
1997年 | 772篇 |
1996年 | 768篇 |
1995年 | 879篇 |
1994年 | 756篇 |
1993年 | 799篇 |
1992年 | 1609篇 |
1991年 | 1802篇 |
1990年 | 1695篇 |
1989年 | 1682篇 |
1988年 | 1515篇 |
1987年 | 1568篇 |
1986年 | 1641篇 |
1985年 | 1597篇 |
1984年 | 1231篇 |
1983年 | 1105篇 |
1979年 | 1176篇 |
1978年 | 935篇 |
1977年 | 791篇 |
1975年 | 809篇 |
1974年 | 1048篇 |
1973年 | 1043篇 |
1972年 | 1060篇 |
1971年 | 1003篇 |
1970年 | 997篇 |
1969年 | 916篇 |
1968年 | 823篇 |
1967年 | 805篇 |
1966年 | 736篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
In faeces and ileal digesta samples of 31 intact (INT) as well as 73 surgically differently prepared pigs bacterial fractionations and 2.6-diaminopimelic acid (DAP) estimations were carried out in order to calculate the bacterial N proportion in faeces N and digesta N after feeding various diets. Because of a high individual variability and the analytical variation width of the DAP/N-ratios no distinct influences of the fed diets could be found. The average DAP/N-values in the faeces (0.224) of INT pigs ranged in the same magnitude as in the digesta (0.0272) of ileorectostomized (IRA) pigs with open colon descendens (IRAo), where a digesta backflow is possible. Distinct lower DAP/N-ratios (0.0125 resp. 0.0043), however, were found in the digesta of pigs with ileo-caecal cannulae (IZB) or IRA pigs with closed colon (IRAg). On the base of various premises (N of the "bacterial fraction" C is only bacterial N; the DAP found in fraction A originates from intestinal bacteria adhering to feed particles) conducted calculations of the bacterial N proportions (in per cent of total N) led to the following data: Faeces of INT pigs: 43.0 ... 68.2 vs. 69.6 ... 89.0; digesta of operated pigs (except protein free diet) IRAo: 22.3 ... 57.0 vs. 46.2 ... 73.8; IZB: 17.0 ... 35.7 vs. 25.2 ... 53.6; IRAg (only 3 pigs): 23.6 vs. 24.2. The proportion of bacterial N in the digesta N of protein free fed IRAo pigs was 22.0 vs. 22.6%. 相似文献
102.
103.
104.
105.
106.
107.
108.
109.
110.
A C Bratanich S I Sardi E N Smitsaart A A Schudel 《Zentralblatt für Veterin?rmedizin. Reihe B. Journal of veterinary medicine. Series B》1991,38(1):41-48
The new encephalitogenic BHV-1.3 and previously characterized BHV-1 strains were studied with reference to their immunogenic and protective potency and their antigenic relationships using "in vitro" and "in vivo" tests. The "in vitro" results obtained by neutralization kinetics showed that the Los Angeles (LA) strain (BHV-1.1) and a vaginal isolate L-114 strain (BHV-1.2) had antigenic similarities. Conversely, the behavior of the encephalitogenic strain A-663 (BHV-1.3), was significantly distinct. The "in vivo" protection test was carried out in calves using LA and A-663 strains. Post-vaccination antibodies and challenge with A-663 strain showed that the immunogenic behavior and protective capacities of both strains were similar. Neutralization kinetics differences between BHV-1.1 and BHV-1.3 did not alter the "in vivo" protection against BHV-1.3 challenge. 相似文献