全文获取类型
收费全文 | 45694篇 |
免费 | 1486篇 |
国内免费 | 3211篇 |
专业分类
林业 | 6020篇 |
农学 | 4395篇 |
基础科学 | 1925篇 |
6990篇 | |
综合类 | 12662篇 |
农作物 | 3914篇 |
水产渔业 | 2762篇 |
畜牧兽医 | 5293篇 |
园艺 | 2869篇 |
植物保护 | 3561篇 |
出版年
2024年 | 176篇 |
2023年 | 501篇 |
2022年 | 1267篇 |
2021年 | 1452篇 |
2020年 | 1292篇 |
2019年 | 1282篇 |
2018年 | 3616篇 |
2017年 | 4033篇 |
2016年 | 2303篇 |
2015年 | 1548篇 |
2014年 | 1613篇 |
2013年 | 1854篇 |
2012年 | 3117篇 |
2011年 | 4466篇 |
2010年 | 4357篇 |
2009年 | 3252篇 |
2008年 | 3093篇 |
2007年 | 3127篇 |
2006年 | 1431篇 |
2005年 | 1269篇 |
2004年 | 666篇 |
2003年 | 635篇 |
2002年 | 555篇 |
2001年 | 443篇 |
2000年 | 491篇 |
1999年 | 443篇 |
1998年 | 298篇 |
1997年 | 268篇 |
1996年 | 239篇 |
1995年 | 193篇 |
1994年 | 178篇 |
1993年 | 196篇 |
1992年 | 156篇 |
1991年 | 136篇 |
1990年 | 111篇 |
1989年 | 92篇 |
1988年 | 83篇 |
1987年 | 35篇 |
1986年 | 37篇 |
1985年 | 16篇 |
1984年 | 13篇 |
1983年 | 6篇 |
1982年 | 8篇 |
1981年 | 10篇 |
1979年 | 7篇 |
1977年 | 4篇 |
1968年 | 4篇 |
1962年 | 2篇 |
1956年 | 8篇 |
1955年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 16 毫秒
41.
Wang R Yuan LG He LM Zhu LX Luo XY Zhang CY Yu JJ Fang BH Liu YH 《Journal of veterinary pharmacology and therapeutics》2011,34(3):247-251
Wang, R., Yuan, L.G., He, L.M., Zhu, L.X., Luo, X.Y., Zhang, C.Y., Yu, J.J., Fang, B.H., Liu, Y.H. Pharmacokinetics and bioavailability of valnemulin in broiler chickens. J. vet. Pharmacol. Therap. 34 , 247–251. The objective of this study was to investigate the pharmacokinetics and bioavailability of valnemulin in broiler chickens after intravenous (i.v.), intramuscular (i.m.) and oral administrations of 10 mg/kg body weight (bw). Plasma samples were analyzed by high‐performance liquid chromatography–tandem mass spectrometry (HPLC‐MS/MS). Pharmacokinetic characterization was performed by non‐compartmental analysis using WinNonlin program. After intravenous administration, distribution was wide with the volume of distribution based on terminal phase(Vz) of 4.27 ± 0.99 L /kg. Mean valnemulin t1/2β(h), Clβ(L /h /kg), Vss (L /kg) and AUC(0–∞)(μg·h /mL) values were 2.85, 0.99, 2.72 and 10.34, respectively. After intramuscular administration, valnemulin was rapidly absorbed with a Cmax of 2.2 μg/mL achieved at 0.43 h (tmax), and the absolute bioavailability (F) was 88.81%; and for the oral route the same parameters were 0.66 ± 0.15 μg/mL, 1.54 ± 0.27 h and 74.42%. A multiple‐peak phenomenon was present after oral administration. The plasma profile of valnemulin exhibited a secondary peak during 2–6 h and a tertiary peak at 32 h. The favorable PK behavior, such as the wide distribution, slow elimination and acceptable bioavailability indicated that it is likely to be effective in chickens. 相似文献
42.
对电感耦合等离子体质谱法检测铅的检出限进行研究,通过对实验过程中所用器皿、试剂等因素进行分?析,建立超声清洗处理方式,有效降低空白值,使电感耦合等离子体质谱仪法测定乳粉中铅的检出限由0.02 mg/kg降?低到0.005 mg/kg。当铅的添加水平为0.005~0.015 mg/kg时,样品的加标回收率为86.9%~119.0%,相对标准偏差为?3.1%~12.3%,满足方法学验证要求,说明了整体方案的可行性。降低检出限后的方法适用于乳粉中铅的检测。 相似文献
43.
Yanfen Ma Ying Feng Liwen Song Muyang Li Hongyu Dai Hua Bao Guijie Zhang Lei Zhao Chunhua Zhang Jing Yi Yusheng Liang 《动物营养(英文)》2021,7(1):206
Peripartal cows often experience negative energy balance, and are therefore prone to suffering from metabolic diseases such as hyperketonemia, which causes financial losses in dairy farms. This study aimed to investigate the effect of green tea polyphenol (GTP) supplementation during the periparturient period on production performance, oxidative stress and immunometabolism in dairy cows with hyperketonemia. One hundred Holstein cows were assigned to GTP (0.2 g/kg DM; n = 50) or control (without GTP; n = 50) group based on body weight, previous milk yield, and parity on d 15 before expected parturition. Subsequently, 10 cows with hyperketonemia were selected from each group, according to blood β-hydroxybutyric acid (BHBA) concentration between 1.2 and 2.9 mmol/L from 2 to 3 d postpartum. All cows were fed a close-up diet and a lactation diet with or without GTP supply from 15 d prepartum until 30 d postpartum. Milk and blood samples were obtained from 20 cows selected with hyperketonemia on 10, 20, and 30 d postpartum. Compared with control cows, greater milk yield and lower somatic cell count were observed in GTP cows. The GTP group had lower concentrations of BHBA, free fatty acids, cholesterol, triglyceride, reactive oxygen species, malondialdehyde, and hydrogen peroxide, greater concentrations of glucose, lower activities of aspartate aminotransferase, alanine aminotransferase, and glutamyl transpeptidase, alongside greater activities of superoxide dismutase, glutathione peroxidase, and total antioxidant capacity. Additionally, GTP supplementation up-regulated concentrations of interleukin-6 and interleukin-10, but down-regulated concentrations of tumor necrosis factor-α, interleukin-1β, interleukin-2, interleukin-8, and interferon-γ in plasma. Greater concentrations of plasma immunoglobulin G were also detected in the GTP group. Overall, the data suggested that GTP supplementation from 15 d prepartum to 30 d postpartum improved the milk yield and health status in cows with hyperketonemia during early lactation. 相似文献
44.
为建立一种牛支原体(Mycoplasma bovis,MB)和牛病毒性腹泻病毒(Bovine viral diarrhea virus,BVDV)的快速鉴别诊断方法,针对MB的uvr C基因和BVDV的5'端非编码区(5'-UTR)保守基因序列,分别设计两对特异引物,并将三温式PCR扩增程序简化为二个温度梯度,建立了鉴别MB和BVDV的二重二温式PCR方法。该方法能同时扩增MB和BVDV,扩增产物大小分别为412和170 bp。特异性试验结果显示,该方法对参试的所有毒株只扩增MB和BVDV基因组,对其它牛病原体无扩增;敏感性试验结果显示,该方法最低能同时检测到104拷贝的两种目的核酸;干扰性试验结果显示,该方法能同时检测两个模板不同浓度的组合,试验结果不受模板影响。综上,本研究所建立的二重二温式PCR方法特异、敏感、快速、简便,可应用于MB和BVDV临床鉴别诊断和流行病学调查。 相似文献
45.
46.
用食盐作为助溶剂采用细胞自溶法,对解脂假丝酵母33M candida lipolytica细胞壁进行破碎后提取神经酰胺,用SPE(固相萃取法)将神经酰胺与膜中其它脂类分离,分别应用TLC(薄层色谱)方法和HPLC-ELSD(高效液相色谱-蒸发光散射器)对其进行定性和定量分析,取得了良好效果。 相似文献
47.
48.
禽流感(Avian influenza,AI)是由A型流感病毒所引起的禽类的一种传染病。能引起禽类呼吸系统到严重全身败血症等多种症状的烈性传染病。禽类感染后病死率很高,但对野生禽类多为不显性感染。自从1997年香港发生禽流感病毒H5N1亚型首次突破种属屏障感染人类并引起死亡以来,世界各国纷纷报道各种人禽流感病例的发生,人禽流感的关注程度也达到了前所未有的高度。近几年全球共有三大洲的19个国家和地区发生禽流感疫情。一些地区的疫情呈现蔓延的趋势,并且出现了人感染禽流感病毒的病例。禽流感不仅对养殖业造成重大损失,更对人类健康造成严重威胁。本文全面地介绍了禽流感的病原、流行病学、临床症状、病理变化、诊断和防制。 相似文献
49.
Monde Mapekula Michael Chimonyo Cletos Mapiye Kennedy Dzama 《Tropical animal health and production》2010,42(7):1413-1419
Understanding the utilisation patterns of milk assists in designing appropriate dairy development schemes in rural communities.
The objective of the study was to determine milk utilisation patterns in different smallholder farming systems in the Eastern
Cape Province of South Africa. Data were collected through the administration of recording sheets to 130 randomly selected
households in Alice, Fort Beaufort and Queenstown districts. Amounts of milk produced per household ranged from 9 to 21 l
per household per day. Milk consumption/household/day was similar among the three districts. Milk consumption in the early
lactation doubled the amount consumed in late lactation (P < 0.05). Milk in the communal areas was largely utilised as fresh or sour milk. Fresh milk was mostly used in tea/coffee
or to make porridge for children. Sour milk was consumed with thick boiled maize meal. Fort Beaufort (10.2 ± 1.37 l/day) had
the highest sour milk sales whilst Queenstown had the highest fresh milk sales (9.7 ± 5.57 l/day). It was concluded that quantities
of milk consumed or sold as fresh or sour were generally low and varied across smallholder farming systems. 相似文献
50.
U.S Salisu C.A Kudi J.O.O. Bale M Babashani B.Y Kaltungo S.N.A Saidu A Asambe A.Y Baba 《Tropical animal health and production》2017,49(5):1041-1046
A cross-sectional study was carried out to determine the status of Brucella infection in one-humped (Dromedary) camels in the North and Central senatorial districts of Katsina State, Nigeria. Nine hundred and eighty serum samples from live and slaughtered camels were tested. Modified Rose Bengal plate test (RBPT) and serum agglutination test (SAT) with ethylenediaminetetraacetic acid, (EDTA) were used as screening and standard tests, respectively. The prevalence of Brucella antibodies were 110 (11.2%) and 103 (10.5%) for RBPT and SAT, respectively. Of the 472 and 508 serum samples tested from the herds and abattoirs, respectively, 63 (13.3%) and 47 (9.3%) were positive by RBPT while 62 (13.1%) and 41 (8.1%) were positive by SAT, respectively. Based on the results, it was concluded that Brucella antibodies were present in camels in the study area. Poor management practices and mixing of camels with other species of livestock as well as unrestricted movement of camels were proposed to be the reasons for the prevalence of the disease in the study area. In view of the public health importance of the disease, it is recommended that there is the need to develop a strategic plan to decrease spread of brucellosis in the study area. 相似文献