全文获取类型
收费全文 | 905篇 |
免费 | 101篇 |
专业分类
林业 | 42篇 |
农学 | 31篇 |
基础科学 | 3篇 |
131篇 | |
综合类 | 49篇 |
农作物 | 43篇 |
水产渔业 | 113篇 |
畜牧兽医 | 511篇 |
园艺 | 10篇 |
植物保护 | 73篇 |
出版年
2024年 | 1篇 |
2023年 | 9篇 |
2022年 | 26篇 |
2021年 | 36篇 |
2020年 | 54篇 |
2019年 | 52篇 |
2018年 | 53篇 |
2017年 | 54篇 |
2016年 | 53篇 |
2015年 | 30篇 |
2014年 | 48篇 |
2013年 | 58篇 |
2012年 | 53篇 |
2011年 | 62篇 |
2010年 | 43篇 |
2009年 | 44篇 |
2008年 | 43篇 |
2007年 | 41篇 |
2006年 | 22篇 |
2005年 | 21篇 |
2004年 | 23篇 |
2003年 | 25篇 |
2002年 | 16篇 |
2001年 | 10篇 |
2000年 | 18篇 |
1999年 | 13篇 |
1998年 | 19篇 |
1997年 | 11篇 |
1996年 | 16篇 |
1995年 | 6篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1992年 | 6篇 |
1991年 | 8篇 |
1990年 | 6篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 3篇 |
1971年 | 3篇 |
1969年 | 1篇 |
1966年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有1006条查询结果,搜索用时 15 毫秒
161.
Rafael Torres Neto Sandra De M.G. Bosco Renée L. Amorim Claudia V.S. Brandão Viciany E. Fabris Caroline Estanislau Eduardo Bagagli 《Veterinary dermatology》2010,21(2):202-204
This report describes a case of cutaneous pythiosis in a 6‐year‐old female mixed breed dog, from the central west region of São Paulo State, Brazil. The cytological and histopathological analyses showed an intense inflammatory infiltrate with presence of numerous hyphal elements, suggesting infection due to Pythium insidiosum. The diagnosis was confirmed by nested‐PCR, which was carried out with specific primers derived from the ribosomal DNA region. The pathogen occurs in Brazil and veterinarians should be aware of the importance of correctly diagnosing this disease and differentiating it from other fungal diseases. 相似文献
162.
<正>仔猪断奶后多系统衰竭综合症(Post-weaning Multi-systemicWasting Syndrome,PMWS)首次发现在1995年和1996年,分别在加拿大和欧洲,该病为一种全球性的猪病,也是由猪圆环病毒2型(PCV2)引起的疾病综合征(也被统称为猪圆环2型病)之一。除了PMWS外,PCV2也被视为母猪繁殖障碍的病因之一。本文的目的是简要地回顾该主题的可用数据和已经公布的从接种Circovac疫苗(一种PCV2灭活苗)的母猪中获得的数据。 相似文献
163.
Renato G Credie Francisco J Teixeira Neto Tatiana H Ferreira Antônio JA Aguiar Fabio C Restitutti José E Corrente 《Veterinary anaesthesia and analgesia》2010,37(3):240-249
ObjectiveTo investigate the effects of methadone on the minimum alveolar concentration of isoflurane (ISOMAC) in dogs.Study designProspective, randomized cross-over experimental study.AnimalsSix adult mongrel dogs, four males and two females, weighing 22.8 ± 6.6 kg.MethodsAnimals were anesthetized with isoflurane and mechanically ventilated on three separate days, at least 1 week apart. Core temperature was maintained between 37.5 and 38.5 °C during ISOMAC determinations. On each study day, ISOMAC was determined using electrical stimulation of the antebrachium (50 V, 50 Hz, 10 mseconds) at 2.5 and 5 hours after intravenous injection of physiological saline (control) or one of two doses of methadone (0.5 or 1.0 mg kg?1).ResultsMean (±SD) ISOMAC in the control treatment was 1.19 ± 0.15% and 1.18 ± 0.15% at 2.5 and 5 hours, respectively. The 1.0 mg kg?1 dose of methadone reduced ISOMAC by 48% (2.5 hours) and by 30% (5 hours), whereas the 0.5 mg kg?1 dose caused smaller reductions in ISOMAC (35% and 15% reductions at 2.5 and 5 hours, respectively). Both doses of methadone decreased heart rate (HR), but the 1.0 mg kg?1 dose was associated with greater negative chronotropic actions (HR 37% lower than control) and mild metabolic acidosis at 2.5 hours. Mean arterial pressure increased in the MET1.0 treatment (13% higher than control) at 2.5 hours.Conclusions and clinical relevanceMethadone reduces ISOMAC in a dose-related fashion and this effect is lessened over time. Although the isoflurane sparing effect of the 0.5 mg kg?1 dose of methadone was smaller in comparison to the 1.0 mg kg?1 dose, the lower dose is recommended for clinical use because it results in less evidence of cardiovascular impairment. 相似文献
164.
165.
Phosphorus,total ammonia nitrogen and chlorophyll a from fish cages in a tropical lake (Lake Palminhas,Espirito Santo,Brazil) 下载免费PDF全文
Graciele P Venturoti Alexandra C Veronez Rômulo V Salla Levy C Gomes 《Aquaculture Research》2016,47(2):409-423
Cage fish farming in natural and artificial lakes has become increasingly popular in recent years in tropical countries. The most commonly farmed tropical fish species is the Nile tilapia (Oreochromis niloticus L.). The aim of this study was to characterize the concentration of phosphorus, total ammonia nitrogen and chlorophyll a from existing fish farms (FF) in Lake Palminhas, located in Linhares/ES, Brazil. Three transects were drawn from 0 to 500 m from each of the four FF (FF1 to FF4) in the lake during six trials (three in the rainy season and three in the dry season). The lake presented a monomictic‐hot pattern, with stratification during the rainy season. Dilution of the monitored parameters did not occur sufficient over a distance of up to 500 m from the FF. The location of the FF in the lake and the input of N and P were critical to ensure optimal mixing conditions because the worst results was observed for the fish farm (FF1) located on a finger of the lake, where the highest concentrations of total phosphorus and chlorophyll a occurred. It was also noted that there was possible total phosphorus interference between FF3 and FF4. The results of this study demonstrate that Lake Palminhas had a low dilution power, and these findings may inform environmental assessments of cage fish farming in this region, providing instruments that may support environmental control of cage fish farming. 相似文献
166.
Growth performance of juvenile pacu (Piaractus mesopotamicus) and dourado (Salminus brasiliensis) fed with lyophilized bovine colostrum 下载免费PDF全文
Raul Machado‐Neto Debora Botequio Moretti Wiolene Montanari Nordi Thaline Maira Pachelli da Cruz José Eurico Possebon Cyrino 《Aquaculture Research》2016,47(11):3551-3557
Growth performance was evaluated in juvenile pacu (Piaractus mesopotamicus) and dourado (Salminus brasiliensis) fed diets containing 0%, 10% and 20% of lyophilized bovine colostrum for 60 days. The performance variables of weight gain, relative weight gain, feed intake, feed conversion ratio, specific growth rate, total protein intake and protein efficiency ratio were evaluated as well as apparent digestibility coefficients of protein and energy in the diets. Inclusion of bovine colostrum did not induce differences in the performance of pacu and dourado (P > 0.05), indicating that the diets were adequate and met the nutritional needs of the juveniles. The protein digestibility in both species was improved with the inclusion of the bovine lacteal secretion. Based on the variables studied, the diets with lyophilized bovine colostrum inclusion were nutritionally suitable for both pacu and dourado indicating the possibility to use this lacteal secretion as a partial substitute of dietary protein. 相似文献
167.
168.
Marcelo Pedrosa Gomes Daniela Moreira Duarte Pedro Luiz Silva Miranda Leilane Carvalho Barreto Miele Tallon Matheus Queila Souza Garcia 《植物养料与土壤学杂志》2012,175(3):466-473
Anadenanthera peregrina is a Brazilian savanna tree species that occurs naturally in arsenic (As)‐contaminated areas, and its As resistance has been associated with arbuscular mycorrhizal–fungi (AMF) symbiosis. A plant's ability to survive in stressful environments is correlated with its nutrition status, which can be affected by As uptake. The present study evaluated the influence of As on the concentrations and distribution of nutrients in the roots and shoots of A. peregrina grown in the absence of AMF. These plants were grown in substrates spiked with 0, 10, 50, and 100 mg As kg–1 for 25 d under greenhouse conditions, and the concentrations of essential macro‐ (P, K, Ca, Mg, N, and S) and micro‐ (Fe, Mn, Cu, Zn, B, and Mo) nutrients in the roots and shoots were then determined. Enhanced As levels increased the concentrations of P, S, and N and decreased Ca, Mg, and Fe. Although the deleterious effects of As on the plants were striking, the internal As levels were high, which indicated some tissue tolerance of A. peregrina. 相似文献
169.
Background
Determining the relative contribution of intrinsic and extrinsic factors to fluctuations in population size, trends and demographic composition is analytically complex. It is often only possible to examine the combined effects of these factors through measurements made over long periods, spanning an array of population densities or levels of food availability. Using age-structured mark-recapture models and datasets spanning five decades (1950–1999), and two periods of differing relative population density, we estimated age-specific probabilities of survival and examined the combined effects of population density and environmental conditions on juvenile survival of southern elephant seals at Macquarie Island. 相似文献170.
Serão NV Veroneze R Ribeiro AM Verardo LL Braccini Neto J Gasparino E Campos CF Lopes PS Guimarães SE 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2011,128(1):28-34
Seventy-two pigs of three genetic groups (Brazilian indigenous breed Piau, Commercial line and Crossbred) of both sexes were slaughtered at four live weights (30, 60, 90 and 120 kg). Intramuscular fat (IMF) content in Longissimus dorsi muscle of each animal was extracted and correlated with candidate gene mRNA expression (ATN1, EEF1A2, FABP3, LDLR, MGP, OBSCN, PDHB, TRDN and RYR1). Within slaughter weight of 120 kg, Piau and Crossbred pigs showed higher IMF content (p < 0.05) than commercial animals, with 2.48, 2.08 and 1.00% respectively. Barrows presented higher values of IMF (p < 0.05) than gilts (1.54 and 1.30% respectively). Gene expression of EEF1A2, FABP3, LDLR, OBSCN, PDHB, TRDN and RYR1 were correlated with IMF (p < 0.05) using the whole dataset. For Piau data only, expression of FABP3, LDLR, MGP, OBSCN, PDHB, TRDN and RYR1 showed correlation with IMF (p < 0.05). Genes that have important roles in lipid transportation inside the cell (FABP3) and tissues (LDLR) showed correlation with IMF of, respectively, 0.68 and 0.63 using the whole data set, and 0.90 and 0.91 using data from Piau animals. The highly positive correlation of the LDLR and FAPB3 expression with IMF content may confirm that these genes are important for fat deposition in the porcine L. dorsi muscle. 相似文献