全文获取类型
收费全文 | 1139篇 |
免费 | 64篇 |
国内免费 | 115篇 |
专业分类
林业 | 43篇 |
农学 | 75篇 |
基础科学 | 13篇 |
431篇 | |
综合类 | 426篇 |
农作物 | 50篇 |
水产渔业 | 31篇 |
畜牧兽医 | 177篇 |
园艺 | 24篇 |
植物保护 | 48篇 |
出版年
2024年 | 5篇 |
2023年 | 16篇 |
2022年 | 36篇 |
2021年 | 40篇 |
2020年 | 41篇 |
2019年 | 32篇 |
2018年 | 58篇 |
2017年 | 69篇 |
2016年 | 73篇 |
2015年 | 48篇 |
2014年 | 57篇 |
2013年 | 96篇 |
2012年 | 101篇 |
2011年 | 85篇 |
2010年 | 51篇 |
2009年 | 62篇 |
2008年 | 43篇 |
2007年 | 50篇 |
2006年 | 45篇 |
2005年 | 52篇 |
2004年 | 40篇 |
2003年 | 24篇 |
2002年 | 24篇 |
2001年 | 24篇 |
2000年 | 21篇 |
1999年 | 16篇 |
1998年 | 10篇 |
1997年 | 15篇 |
1996年 | 11篇 |
1995年 | 16篇 |
1994年 | 8篇 |
1993年 | 11篇 |
1992年 | 6篇 |
1991年 | 8篇 |
1990年 | 6篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有1318条查询结果,搜索用时 0 毫秒
11.
12.
13.
Young adult sheep were dosed with extracts of Narthecium ossifragum plants by the oral or parenteral routes and the resulting nephrotoxicity was assessed from the increases in the concentrations of creatinine and urea in the serum. Following single intraruminal or intraperitoneal doses of extracts derived from 30 g N. ossifragum (wet weight) per kg live weight (kg lw), serum creatinine concentrations increased from about 100 mol/L to between 260 and 510 mol/L. The serum urea concentrations increased from about 5–8 mmol/L to between 11 and 66 mmol/L in individual sheep. Daily intraruminal administration of 5–30 g/kg lw to three sheep over a 10- or 15-day period increased creatinine concentrations from 100 mol/L to 300–760 mol/L, and urea concentrations from 5–8 mmol/L to 35 mmol/L. A single intraperitoneal challenge dose of 30 g/kg lw, delivered 7 or 12 days after the final intraruminal dose, did not lead to increased serum creatinine or urea concentrations, indicating that oral treatment had apparently resulted in an increased tolerance to the nephrotoxic principle(s) in N. ossifragum. 相似文献
14.
为研究纤维素酶和乳酸菌制剂以及尿素对小麦秸黄贮饲料品质的影响,分别设不同的处理组及对照进行小麦秸黄贮饲料的发酵试验。实验Ⅰ结果表明:尿素单独添加、尿素和纤维素酶混合添加显著提高粗蛋白的含量,尿素和乳酸菌制剂、以及尿素与乳酸菌制剂和纤维素酶混合添加都不能得到品质较好的小麦秸黄贮饲料。实验Ⅱ结果表明:各添加剂处理均显著降低黄贮饲料的pH值和中性洗涤纤维含量(P<0.05),显著提高乳酸、总酸和粗蛋白含量(P<0.05);添加剂处理能够明显改善小麦秸黄贮饲料的发酵品质,提高小麦秸的饲用价值。纤维素酶和乳酸菌制剂同时添加时,小麦秸黄贮饲料品质最好。 相似文献
15.
A. Nurfeta A. Tolera L. O. Eik F. Sundstøl 《Journal of animal physiology and animal nutrition》2009,93(1):94-104
Feed intake, in vivo nutrient digestibility and nitrogen utilization were evaluated in male sheep fed different fractions (leaf, pseudostem, corm, whole plant) of enset, untreated or 2% urea‐ and 3% calcium oxide‐ (CaO or lime) treated wheat straw and Desmodium intortum hay as sole diets. All feeds, except D. intortum hay and enset leaf had low crude protein (CP) content. Non‐fiber carbohydrate contents were higher in enset fractions, especially in pseudostem and corm relative to other feeds. Enset leaf and pseudostem had high calcium, phosphorus and manganese contents. Corm, whole enset and D. intortum hay were rich sources of zinc. Daily dry matter and CP intakes were higher (p < 0.05) in sheep fed D. intortum hay (830 and 133 g, respectively) than those fed pseudostem (92 and 7.8 g, respectively). Organic matter digestibilities were highest for corm (0.780) and whole enset (0.776) and lowest for D. intortum hay (0.534) and untreated wheat straw (0.522). The CP digestibility ranged from 0.636 in D. intortum hay to 0.408 in corm. Nitrogen (N) balance was highest (p < 0.05) in D. intortum hay (10.4 g/day) and lowest in corm (?1.3 g/day). Enset leaf could be a useful protein supplement whereas the pseudostem and corm could be good sources of energy. 相似文献
16.
1前言湖南省洞口县第二例牛尿素中毒,制做了简易竹洞针,进行左赚部套洞针(竹洞针)穿刺术放气,灌入食醋,葡萄糖输液等抢救和治疗方案。牛场存栏328头,239头中毒,发病率72.9%,治疗239头,治愈216头,治愈率90.4%,较首例牛尿素中毒病例治愈率100%,降低9.6个百分点,瘤胃膨气病病牛128头,治愈105头,治愈率82.0%,较洞口县首例牛尿素中毒病例治愈率100%,下降18.0个百分点;并对牛瘤胃膨气病最佳抢救时间和尿素养牛正确用量用法进行了探索,供同行参考。 相似文献
17.
18.
Birthe M. Damgaard Christian F. Børsting Klaus L. Ingvartsen Rikke Fink 《Acta Agriculturae Scandinavica, Section A - Animal Sciences》2013,63(3):127-135
The effects of carbohydrate-free diets on body weight changes, feed consumption, and plasma concentrations of nutrients, metabolites, and hormones in lactating mink and on growth performance in kits were investigated in a total of 108 litters during the lactation period of seven weeks. The litters were distributed in three experimental groups fed different ratios of metabolisable energy (ME) derived from protein and fat (61:38; 47:52; 33:66). The females and kits were weighed at parturition and 2, 3, 4, and 7 weeks after parturition. Blood samples were collected from females in the second, fourth, and sixth week of the lactation period. Carbohydrate-free diets fed to lactating mink can in principle support normal performance, health of the females, and growth performance of the kits. However, mink need a sufficient supply of available gluconeogenic precursors in the form of amino acids. In the present experiment, the diet with 33% of ME from protein contained insufficient amounts of gluconeogenic precursors for lactating mink, and three weeks post partum this group was excluded from the experiment. The differences in dietary protein level (61% and 47% of ME) and fat level (38% and 52% of ME) influenced the plasma concentrations of free fatty acids (FFA) and urea, but had minimal influence on plasma concentrations of other nutrients, metabolites, and hormones. 相似文献
19.
Abstract Thirty-two Chinese Holstein lactating cows were used to investigate the relationship of milk urea nitrogen (MUN) and nitrogen excretion loading to the environment. Cows were fed a similar amount of forage, and concentrates according to milk production. Total collection of urine and faeces were conducted continuously for three days. The milk urea nitrogen was significantly correlated to total nitrogen excretion (R 2=0.70), urinary nitrogen excretion (R 2=0.85), and nitrogen excretion from faeces (R 2=0.22). The following equation was proposed to predict total nitrogen excretion (TNE) (g/d) based on milk urea nitrogen (MUN) (mg/dl): TNE?=?15.46(±1.83)×MUN?+?193.40(±28.79). The results obtained in this study suggested that MUN might be used to predict TNE from lactating cows. 相似文献
20.