全文获取类型
收费全文 | 14590篇 |
免费 | 913篇 |
国内免费 | 1536篇 |
专业分类
林业 | 1041篇 |
农学 | 1303篇 |
基础科学 | 1071篇 |
1840篇 | |
综合类 | 6186篇 |
农作物 | 1001篇 |
水产渔业 | 838篇 |
畜牧兽医 | 2116篇 |
园艺 | 811篇 |
植物保护 | 832篇 |
出版年
2024年 | 122篇 |
2023年 | 299篇 |
2022年 | 699篇 |
2021年 | 743篇 |
2020年 | 684篇 |
2019年 | 694篇 |
2018年 | 561篇 |
2017年 | 735篇 |
2016年 | 535篇 |
2015年 | 763篇 |
2014年 | 741篇 |
2013年 | 913篇 |
2012年 | 1240篇 |
2011年 | 1195篇 |
2010年 | 1154篇 |
2009年 | 1114篇 |
2008年 | 1055篇 |
2007年 | 899篇 |
2006年 | 705篇 |
2005年 | 596篇 |
2004年 | 318篇 |
2003年 | 264篇 |
2002年 | 235篇 |
2001年 | 172篇 |
2000年 | 168篇 |
1999年 | 116篇 |
1998年 | 37篇 |
1997年 | 36篇 |
1996年 | 44篇 |
1995年 | 40篇 |
1994年 | 27篇 |
1993年 | 24篇 |
1992年 | 14篇 |
1991年 | 10篇 |
1990年 | 13篇 |
1989年 | 13篇 |
1988年 | 7篇 |
1987年 | 10篇 |
1986年 | 9篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1980年 | 2篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1973年 | 2篇 |
1968年 | 2篇 |
1966年 | 2篇 |
1962年 | 2篇 |
1956年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 30 毫秒
21.
家蚕预蛹粉对糖尿病模型小鼠的降血糖效果试验 总被引:1,自引:0,他引:1
利用变态发育至预蛹期的家蚕制备预蛹粉及脱脂预蛹粉,并添加至饲料中饲喂四氧嘧啶诱导糖尿病模型小鼠,观测小鼠血糖值及基本生理状况和主要脏器指数的改变。试验组糖尿病模型小鼠饲喂添加5%家蚕预蛹粉的饲料后,其"三多一少"症状有显著改善,肝脏指数、肾脏指数和血糖浓度均极显著降低,脾脏指数极显著提高,其中空腹血糖(FBG)比对照模型组小鼠下降20.38%,餐后血糖(PBG)下降39.07%;饲喂添加5%脱脂预蛹粉饲料的糖尿病模型小鼠,其控制血糖效果明显低于预蛹粉添加组。试验组糖尿病模型小鼠饲喂添加1%、5%和10%预蛹粉的饲料后的糖化血红蛋白(HbA1 c)均极显著低于对照模型组小鼠,分别降低了31.39%、45.89%和54.42%;5%和10%预蛹粉添加组模型小鼠的血清C肽极显著高于对照模型组小鼠,分别增加了18.97%和29.31%。试验结果显示,家蚕预蛹粉能有效控制糖尿病模型小鼠的血糖水平,并改善小鼠的基本生理状况和脏器指数,但总体效果略低于拜糖平添加组;脱脂后的家蚕预蛹粉的降血糖效果显著降低,提示其降血糖活性分子可能存在于脂溶性物质中。 相似文献
22.
Eva Persson Margret Wülbers-Mindermann Charlotte Berg Bo Algers 《Acta veterinaria Scandinavica》2008,50(1):24
Background
The natural feeding behaviour of the pig is searching for feed by rooting activities throughout the day; self-feeding pigs randomly space their eating and drinking periods throughout the day consuming ten to twelve meals per day. Pigs in conventional fattening pig production are normally fed 2–3 times daily with the feed consumed within 15 minutes. The aim of this study was to determine if more frequent feedings could improve the performance of conventionally kept fattening pigs.Methods
The experiment was carried out on 360 fattening pigs (27–112 kg live weight), weighed and assigned to pens stratified by weight and sex. Each treatment group consisted of 180 pigs, allocated to 20 pens with nine pigs in each pen. To evaluate how more feeding occasions affects performance and well-being the pigs were divided into two groups and fed three (control group) or nine (treatment group) times daily. The same total amount of liquid feed was fed to each group and the feed ration was correlated to the live weight of the pigs. All weight and slaughter recordings were made individually and recordings of feed consumption were made pen-wise. At slaughter the stomach of each pig was examined for lesions in the pars oesophagea and scored on a scale from 1–6.Results
Frequent feeding occasions influenced both performance and status of gastric lesions of the pigs adversely. Pigs in the treatment group grew slower compared to pigs in the control group; 697 g/day (± 6.76) versus 804 g/day (± 6.78) (P < 0.001) with no difference in within-pen variation. There was also a lower prevalence of gastric lesions within pigs in the control group (2.4 (± 0.12) compared to 3.0 (± 0.12) (P < 0.01)). There was a positive correlation between gastric lesions in the treatment group and daily weight gain (r = 0.19; P < 0.01).Conclusion
Increased daily feeding occasions among group housed pigs resulted in a poorer daily weight gain and increased mean gastric lesion score as compared with pigs fed three times daily. This may be a consequence of more frequently occurring competition for feed in the treatment group. The present study does not support increased daily feeding occasions in fattening pigs. 相似文献23.
我国新发人畜共患传染病及其防控策略 总被引:2,自引:0,他引:2
近年来,各种生物学因素、自然因素以及社会因素加剧了新发人畜共患传染病的发生、传播与流行,给人类的健康带来了很大的威胁,也造成了很大的经济损失,同时,也导致了诸多的社会问题.面对新发人畜共患传染病的挑战,人类应重新认识人畜共患传染病对人类健康的危害和影响,提高警惕,采取切实有效的应对措施,预防和控制传染病的发生和流行.本文就新发人畜共患传染病对人类健康和生存的严重威胁、影响因素和预防控制对策进行了分析和探讨. 相似文献
24.
25.
26.
21个粮饲兼用型青贮玉米在河南的品种比较试验 总被引:1,自引:0,他引:1
为选出适合河南地区种植的青贮玉米品种,采用随机法对21个玉米品种(每个玉米品种5个重复)进行分区组种植,以研究其生物学产量、籽粒产量、抗倒伏性和品质,及其各农艺性状的相关关系。结果表明:1)以京科青贮932、伟科106的生物学产量和籽粒产量最高,且具有良好的抗倒伏性能。2)伟科106、京科青贮932有较高的粗蛋白、粗脂肪和淀粉含量,而中性洗涤纤维(NDF)、酸性洗涤纤维(ADF)的含量较低,品质较优。3)生物学产量与绿叶数、绿叶重、株高、茎粗和茎重、穗重呈极显著正相关,籽粒产量与绿叶数、绿叶重、茎粗和茎重、穗重呈极显著正相关,生物学产量与籽粒产量也呈极显著正相关。因此,选用绿叶多和绿叶重、茎重和茎粗、穗部产量均优且有一定植株高度的品种有利于获得高产;粗蛋白与粗脂肪、淀粉含量呈正相关。从生物学产量、籽粒产量、品质、抗倒伏性能和农艺性状方面综合考虑,京科青贮932和伟科106表现最佳,适宜作为全株青贮玉米品种和粮饲兼用品种在河南地区推广种植。 相似文献
27.
Nan‐Xi Hu Mei Chen Yi‐Song Liu Qi Shi Bo Yang Huan‐Cheng Zhang Pi Cheng Qi Tang Zhao‐Ying Liu Jian‐Guo Zeng 《Journal of veterinary pharmacology and therapeutics》2019,42(2):197-206
Sanguinarine (SA) and chelerythrine (CHE) are the main active components of the phytogenic livestock feed additive, Sangrovit®. However, little information is available on the pharmacokinetics of Sangrovit® in poultry. The goal of this work was to study the pharmacokinetics of SA, CHE, and their metabolites, dihydrosanguinarine (DHSA) and dihydrochelerythrine (DHCHE), in 10 healthy female broiler chickens following oral (p.o.) administration of Sangrovit® and intravenous (i.v.) administration of a mixture of SA and CHE. The plasma samples were processed using two different simple protein precipitation methods because the parent drugs and metabolites are stable under different pH conditions. The absorption and metabolism of SA following p.o. administration were fast, with half‐life (t1/2) values of 1.05 ± 0.18 hr and 0.83 ± 0.10 hr for SA and DHSA, respectively. The maximum concentration (Cmax) of DHSA (2.49 ± 1.4 μg/L) was higher that of SA (1.89 ± 0.8 μg/L). The area under the concentration vs. time curve (AUC) values for SA and DHSA were 9.92 ± 5.4 and 6.08 ± 3.49 ng/ml hr, respectively. Following i.v. administration, the clearance (CL) of SA was 6.79 ± 0.63 (L·h?1·kg?1) with a t1/2 of 0.34 ± 0.13 hr. The AUC values for DHSA and DHCHE were 7.48 ± 1.05 and 0.52 ± 0.09 (ng/ml hr), respectively. These data suggested that Sangrovit® had low absorption and bioavailability in broiler chickens. The work reported here provides useful information on the pharmacokinetic behavior of Sangrovit® after p.o. and i.v. administration in broiler chickens, which is important for the evaluation of its use in poultry. 相似文献
28.
本研究旨在探讨铜和维生素A及其互作效应对内仔鸡生长性能及抗氧化功能的影响.试验选用1日龄艾维茵肉仔鸡448只,随机分为8组,每组4个重复,每个重复14只鸡.采用4×2(铜×维生素A)完全随机设计,饲粮铜的添加量分别为0、8、150、225 mg/kg,维生素A的添加量分别为1 500、5 000 IU/kg,分为2个生长阶段,前期为1~4周龄,后期为5~7周龄.结果表明:1)高铜( 150、225mg/kg)抑制了全期肉仔鸡生长性能,提高了全期血清铜蓝蛋白(Cp)和后期血清总超氧化物歧化酶(T-SOD)活性(P<0.05).2)5 000 IU/kg维生素A组获得较好的生长性能,提高了全期血清T-SOD活性,降低了前期血清Cp活性(P<0.05).3)铜和维生素A互作效应对前期体增重、血清Cp和T-SOD活性及全期料重比有显著影响(P<0.05),且二者间存在互补作用.铜(8 mg/kg)×维生素A(5 000 IU/kg)组与铜(0 mg/kg)×维生素A(5 000 IU/kg)组对前期肉仔鸡获得良好生长性能和提高血清T-SOD活性均有促进作用,但对血清Cp活性有显著降低作用(P<0.05).由此可见,在基础饲粮铜水平为16~23mg/kg时,铜的适宜添加量为前期8 mg/kg,后期0~8 mg/kg;全期维生素A的适宜添加量为5 000 IU/kg. 相似文献
29.
30.
建立了油制磺胺间甲氧嘧啶钠(SMM-Na)混悬注射液含量测定的HPLC方法。样品中加入表面活性剂使其成为微乳溶液,然后稀释进样分析。色谱柱为phenomenex synergi Hydro-RP(250 mm×4.6 mm,4μm),柱温40℃,以甲醇-乙腈-1.5%冰乙酸水溶液(10∶20∶70)为流动相,流速为1 mL/min,检测波长271 nm。同一样品经永停滴定法和HPLC两种方法进行含量测定并进行t检验分析,结果显示t0.05,P0.05,呈显著差异。HPLC测定制剂的平均含量为98.99%,RSD为0.48%。磺胺间甲氧嘧啶在20~60μg/mL的浓度范围内与峰面积呈良好的线形关系。本方法更简单、快速、准确,可用于油制磺胺间甲氧嘧啶钠混悬注射液的含量测定。 相似文献