全文获取类型
收费全文 | 17797篇 |
免费 | 73篇 |
国内免费 | 1篇 |
专业分类
林业 | 3740篇 |
农学 | 1485篇 |
基础科学 | 159篇 |
3020篇 | |
综合类 | 755篇 |
农作物 | 2178篇 |
水产渔业 | 1823篇 |
畜牧兽医 | 1560篇 |
园艺 | 1177篇 |
植物保护 | 1974篇 |
出版年
2023年 | 10篇 |
2022年 | 22篇 |
2021年 | 36篇 |
2020年 | 32篇 |
2019年 | 25篇 |
2018年 | 2783篇 |
2017年 | 2744篇 |
2016年 | 1239篇 |
2015年 | 101篇 |
2014年 | 57篇 |
2013年 | 128篇 |
2012年 | 841篇 |
2011年 | 2184篇 |
2010年 | 2144篇 |
2009年 | 1293篇 |
2008年 | 1372篇 |
2007年 | 1621篇 |
2006年 | 74篇 |
2005年 | 137篇 |
2004年 | 134篇 |
2003年 | 189篇 |
2002年 | 99篇 |
2001年 | 32篇 |
2000年 | 66篇 |
1999年 | 29篇 |
1998年 | 13篇 |
1997年 | 9篇 |
1996年 | 15篇 |
1995年 | 12篇 |
1994年 | 10篇 |
1993年 | 23篇 |
1992年 | 25篇 |
1991年 | 20篇 |
1990年 | 31篇 |
1989年 | 26篇 |
1988年 | 25篇 |
1987年 | 21篇 |
1986年 | 17篇 |
1985年 | 18篇 |
1984年 | 11篇 |
1983年 | 12篇 |
1982年 | 14篇 |
1981年 | 17篇 |
1980年 | 14篇 |
1979年 | 21篇 |
1978年 | 15篇 |
1977年 | 15篇 |
1972年 | 9篇 |
1969年 | 15篇 |
1968年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Oluwole Oyetunde Oni Ademola Amubieya Owoade Christopher Adeyinka Olugbenga Adeyefa 《Tropical animal health and production》2018,50(2):267-273
The use of molecular methods for rotavirus characterisation provides increased sensitivity for typing and allows the identification of putative reassortant strains. Reagents and methods for genotyping the virus need constant modification because of the reassortant nature of the virus. This study was aimed at designing and evaluating new oligonucleotide degenerate primer pairs that provide increased sensitivity and specificity for detecting avian rotavirus. Gene-specific primer pairs were designed by analysing different rotavirus strains isolated during the last decade by downloading them from the GenBank. The alignments were generated using clustal analysis from the BioEdit program. Degenerate nucleotides were included due to the reassortant nature of rotavirus. The consensus sequences were aligned using the BioEdit program and then treated with the Fast PCR software to derive the primers. The derived primer sequences were submitted for a BLAST search to ensure alignment was exclusive to the desired target genes. The designed primers had specific bands and were efficient in detecting rotavirus in faecal samples than previously published primers. Thus, a successful surveillance of rotaviruses requires that primer pairs be updated regularly in order to detect the emergence of novel or “unusual types”, which have occurred by genetic drift causing nucleotide changes at the primer binding sites that result in typing failures. We recommend the use of the proposed primers in molecular surveillance studies for efficient detection of avian rotavirus. 相似文献
72.
Lucíola Vilarim Ferraz Adriana Guim Robson Magno Liberal Véras Francisco Fernando Ramos de Carvalho Marciela Thais Dino de Freitas 《Tropical animal health and production》2018,50(2):309-315
The effects of corn replacement by cassava dreg in diets of crossbred goat kids were evaluated. We tested the impacts of 0, 33, 66 and 100% replacement on intake, digestibility, feeding behaviour, performance and carcass characteristics. Thirty-six goat kids, aged between 4 and 5 months and with initial body weights of 17.61 ± 1.98 kg, were used in a completely randomised design. Analysis of regression revealed a negative linear effect on neutral detergent fibre (NDF) intake and a positive linear effect on non-fibrous carbohydrates (NFC) and hydrocyanic acids (HCN) intake. Cassava dreg use had a positive linear effect on organic matter digestibility and non-fibrous carbohydrates. Based on our results, cassava dreg use did not negatively impact animal performance, feeding behaviour and carcass characteristics, suggesting that it may replace corn up to 100% in the diets of confined goat kids. 相似文献
73.
ObianujuNkiruka Okoroafor Paul Chekwube Eze Wilfred Sunday Ezema Chika Nwosu Christian Okorie-Kanu P. C. Animoke Boniface Anene John Osita Arinze Okoye 《Tropical animal health and production》2018,50(2):345-351
The aim of this project is to study the clinical signs and lesion of velogenic Newcastle disease (vND) in commercial turkeys, and also to find out if La Sota vaccination offered protection against these signs and lesions. The cockerels were included as positive controls. One hundred and twenty turkey poults and cockerels were divided into eight groups as follows: unvaccinated unchallenged turkeys (UUT), unvaccinated challenged turkeys (UCT), vaccinated unchallenged turkeys (VUT), vaccinated challenged turkeys (VCT), and along the same lines, the cockerel groups were UUC, UCC, VUC and vaccinated challenged cockerels (VCC). Vaccination was at 3 weeks of age while challenge was at 6 weeks of age. The unvaccinated turkeys and cockerels (UCT and UCC) showed different degrees of depression, diarrhoea and later paralysis at challenge. Total mortality was 100% in cockerels within 6 days, but 60% in turkeys. Similar but milder clinical signs were found in the VCC with a total mortality of 13.3%. The VCT showed mild drop in feed and water consumption, and no mortality. All the challenged groups had significant (p < 0.05) loss of weight when compared with their controls. Necropsy showed that while the UCC had severe proventricular haemorrhages, intestinal and caecal tonsil ulcers, the UCT had no digestive tract lesion. There was severe atrophy of the lymphoid organs in all the challenged groups. Histopathological sections of the bursa, spleen and thymus in all the challenged groups with special emphasis on the vaccinated and unvaccinated turkeys with mortalities of 0 and 60%, respectively, had very severe necrosis and depletion of the lymphoid tissue. Virus was isolated from the cloacal swabs. The haemagglutination inhibition antibodies were significantly higher (p < 0.05) in the challenged groups than the unchallenged. The above observations in the intestinal tracts of UCT are of diagnostic significance while the gross and microscopic lesions in the UCT and VCT show that La Sota vaccination may not protect turkeys against the destruction of the lymphoid organs by vND as earlier reported in chickens. This may lead to immunosuppression and production problems in areas where vND is enzootic. 相似文献
74.
Lounis Mohamed Zhao Ge Li Yuehua Gao Yubin Kaidi Rachid Oumouna Mustapha Wang Junwei Oumouna Karine 《Tropical animal health and production》2018,50(3):547-553
Avian pathogenic E. coli (APEC) is the etiologic agent of avian colibacillosis, the most common disease responsible for chicken morbidity in the world. Although multiple virulence-associated factors were identified, their prevalence in Algeria is still poorly known. In the present research, 92 avian pathogenic E. coli (APEC) isolates were recovered from broilers with clinical signs and lesions of colibacillosis. In addition, 32 E. coli isolates collected from feces of healthy birds (AFEC) were included for comparison. All isolates were investigated by PCR for the presence of a total of 11 virulence-associated genes described for avian pathogenic (iroN, ompT, hlyF, iss, iutA, and fimC) and diarrheagenic E. coli (eae, stx, elt/est, ipaH, and aggR). The sensitivity of 39 APEC isolates to 16 antibiotics was also determined using antimicrobial pretreated microplates. Here, we report that 98% of the examined isolates host at least one of the tested virulence factors. The most prevalent genes in APEC were iutA (90.6%), ompT (86.9%), and iss (85.8%); whereas, iutA (78.1%), fimC (78.1%), and iroN (68.7%) were the highest prevalent genes in AFEC. Our data showed that none of the AFEC isolates harbor any of the tested diarrheagenic genes. Moreover, only elt/est (5.4%), stx (2.1%), and ipaH (2.1%) genes were carried by APEC isolates. We further established that ceftazodime, ceftiofur, mequindox, amoxicillin/clavulanic acid, and meropenem were the most efficient antibiotics against the analyzed APEC isolates. Overall, our findings provide more insights about APEC and AFEC virulence potential in Algeria which could participate in the fight against colibacillosis. 相似文献
75.
Daniel A. Truchado Michaël A. J. Moens Sergio Callejas Javier Pérez-Tris Laura Benítez 《Veterinary research communications》2018,42(2):111-120
Papillomaviruses are non-enveloped, DNA viruses that infect skin and mucosa of a wide variety of vertebrates, causing neoplasias or simply persisting asymptomatically. Avian papillomaviruses, with six fully sequenced genomes, are the second most studied group after mammalian papillomaviruses. In this study, we describe the first oral avian papillomavirus, detected in the tongue of a dead Yorkshire canary (Serinus canaria) and in oral swabs of the same bird and other two live canaries from an aviary in Madrid, Spain. Its genome is 8,071 bp and presents the canonical papillomavirus architecture with six early (E6, E7, E1, E9, E2, E4) and two late open reading frames (L1 and L2) and a long control region between L1 and E6. This new avian papillomavirus L1 gene shares a 64% pairwise identity with FcPV1 L1, so it has been classified as a new species (ScPV1) within the Ethapapillomavirus genus. Although the canary died after showing breathing problems, there is no evidence that the papillomavirus caused those symptoms so it could be part of the oral microbiota of the birds. Hence, future investigations are needed to evaluate the clinical relevance of the virus. 相似文献
76.
77.
Eight maize complexes and varieties representing high and low yield levels were tested for their suitability as top cross testers by comparing the performance of the crosses in relation to the combining ability of the parents estimated by diallel analysis. The discriminating ability of the testers was compared by Schumann and Bradley test. In both cases the results clearly showed that the low performing testers were better and more reliable than the high performing complexes. The utility of per se performance as an indication of general combining ability of the complexes has been discussed. 相似文献
78.
79.
Partitioning the respiratory components of soil surface CO2 efflux is important in understanding carbon turnover and in identifying the soil carbon sink/source function in response to land-use change. The sensitivities of soil respiration components on changing climate patterns are currently not fully understood. We used trench and isotopic methods to separate total soil respiration into autotrophic (R A ) and heterotrophic components (R H ). This study was undertaken on a Robinia pseudoacacia L. plantation in the southern Taihang Mountains, China. The fractionation of soil 13CO2 was analyzed by comparing the δ13C of soil CO2 extracted from buried steel tubes with results from Gas Vapor Probe Kits at a depth of 50 cm at the preliminary test (2.03‰). The results showed that the contribution of autotrophic respiration (fR A ) increased with increasing soil depth. The contribution of heterotrophic respiration (fR H ) declined with increasing soil depth. The contribution of autotrophic respiration was similar whether estimated by the trench method (fR A , 23.50%) or by the isotopic method in which a difference in value of 13C between soil and plant prevailed in the natural state (RC, 21.03%). The experimental error produced by the trench method was insignificant as compared with that produced by the isotopic method, providing a technical basis for further investigations. 相似文献
80.