收费全文 | 71403篇 |
免费 | 4130篇 |
国内免费 | 35篇 |
林业 | 3270篇 |
农学 | 2560篇 |
基础科学 | 487篇 |
8793篇 | |
综合类 | 11462篇 |
农作物 | 2611篇 |
水产渔业 | 3715篇 |
畜牧兽医 | 36963篇 |
园艺 | 915篇 |
植物保护 | 4792篇 |
2018年 | 1087篇 |
2017年 | 1155篇 |
2016年 | 1076篇 |
2015年 | 930篇 |
2014年 | 1170篇 |
2013年 | 2672篇 |
2012年 | 2090篇 |
2011年 | 2498篇 |
2010年 | 1711篇 |
2009年 | 1774篇 |
2008年 | 2624篇 |
2007年 | 2381篇 |
2006年 | 2351篇 |
2005年 | 2149篇 |
2004年 | 2210篇 |
2003年 | 2178篇 |
2002年 | 2052篇 |
2001年 | 2380篇 |
2000年 | 2391篇 |
1999年 | 1940篇 |
1998年 | 920篇 |
1997年 | 827篇 |
1996年 | 788篇 |
1995年 | 869篇 |
1994年 | 849篇 |
1993年 | 769篇 |
1992年 | 1531篇 |
1991年 | 1548篇 |
1990年 | 1666篇 |
1989年 | 1514篇 |
1988年 | 1454篇 |
1987年 | 1350篇 |
1986年 | 1392篇 |
1985年 | 1346篇 |
1984年 | 1131篇 |
1983年 | 1028篇 |
1982年 | 630篇 |
1979年 | 1011篇 |
1978年 | 797篇 |
1977年 | 720篇 |
1976年 | 677篇 |
1975年 | 727篇 |
1974年 | 774篇 |
1973年 | 834篇 |
1972年 | 804篇 |
1971年 | 749篇 |
1970年 | 731篇 |
1969年 | 745篇 |
1967年 | 659篇 |
1966年 | 631篇 |
Three experiments with a 2 × 2 × 2 factorial arrangement were conducted to evaluate maize-based diets for broilers containing different lipid sources [soybean oil (S) or beef tallow (T)] supplemented with or without lysophospholipids and organic acids on nutrient balance (Experiment I, evaluation period of 10–14 d), on liver concentration of fat-soluble vitamins, on jejunal microbiota (Experiment II, sampling at d 14) and on performance (Experiment III, accumulated periods of 1–14, 1–21 and 1–42 d).
A total of 1344 male chicks were used. In each experiment, the birds were allotted in a completely randomised design with 8 replications. The lysophospholipids were mainly composed of lysolecithins and the organic acids blend was constituted by lactic (40%), acetic (7%) and butyric acids (1%).
An interaction between lipid sources and lysophospholipids was observed on faecal apparent digestibility of lipid (ADL), which improved with lysophospholipids addition in T diets. Broilers fed on S had higher ADL and faecal apparent digestibility of nitrogen-corrected gross energy (ADGEN).
It was not possible to demonstrate a significant treatment effect on the liver concentration of vitamins A and E, even with the differences in fatty acid profile between S and T.
Enterobacteria values were below the detection threshold. Lysophospholipid supplementation reduced gram-positive cocci in T-fed birds. S diets promoted lower total anaerobe counts compared with T diets, independent of additives.
S diets increased BW gain and feed:gain ratio in all evaluation periods. Lysophospholipids and organic acids improved feed:gain ratio at 1–21 d in T diets. Furthermore, main effects were observed for lysophospholipids and organic acids at 1–42 d, which increased BW gain and improved feed:gain ratio, respectively.
No positive interactions between additives were found.
The aim of this study, comprising two experiments, was (1) to determine in Experiment 1 the relationship of incremental dietary P (phosphorus) content on precaecal digestible P in male broilers and (2) to determine in Experiment 2 the precaecal P digestibility of various inorganic P sources at marginal levels of P supply.
In Experiment 1, a total of 260 male Ross 308 broilers were divided into groups of 10 birds per pen resulting in 8 replicates for treatment 1 and 6 replicates for treatments 2–4. Experimental diets were formulated to contain 4 incremental concentrations of digestible P by means of increasing concentrations of monocalcium phosphate (MCP). In the second experiment, 480-d-old male Ross 308 broilers were divided in groups of 12 birds per pen resulting in 16 replicates for the basal diet and 6 replicates for each test diet. A total of 4 inorganic P sources, MCP, monodicalcium phosphate (MDCP), dicalcium phosphate (DCP) and defluorinated phosphate (DFP) were added to the basal diet to determine the precaecal P digestibility. Three of the 4 inorganic P sources (MCP, MDCP and DCP) represented a mix of batches from different producers. At the end of both experiments, the chyme of the posterior part of the small intestine was collected. Digestibility of P and Ca was determined using titanium dioxide as indigestible marker.
In Experiment 1, a reduction in precaecal digestibility of P was observed above an estimated precaecal digestible dietary P concentration of 4.8 g/kg.
The precaecal P digestibility of the tested inorganic P sources in Experiment 2 was 78.3% for MCP, 59.0% for DCP, 70.7% for MDCP and 31.5% for DFP.