全文获取类型
收费全文 | 12165篇 |
免费 | 929篇 |
国内免费 | 3篇 |
专业分类
林业 | 1234篇 |
农学 | 449篇 |
基础科学 | 53篇 |
2764篇 | |
综合类 | 811篇 |
农作物 | 515篇 |
水产渔业 | 812篇 |
畜牧兽医 | 5037篇 |
园艺 | 289篇 |
植物保护 | 1133篇 |
出版年
2023年 | 104篇 |
2022年 | 134篇 |
2021年 | 245篇 |
2020年 | 240篇 |
2019年 | 166篇 |
2018年 | 571篇 |
2017年 | 533篇 |
2016年 | 488篇 |
2015年 | 403篇 |
2014年 | 465篇 |
2013年 | 693篇 |
2012年 | 948篇 |
2011年 | 893篇 |
2010年 | 480篇 |
2009年 | 373篇 |
2008年 | 753篇 |
2007年 | 717篇 |
2006年 | 582篇 |
2005年 | 606篇 |
2004年 | 559篇 |
2003年 | 511篇 |
2002年 | 431篇 |
2001年 | 289篇 |
2000年 | 253篇 |
1999年 | 226篇 |
1998年 | 76篇 |
1997年 | 65篇 |
1996年 | 46篇 |
1995年 | 63篇 |
1994年 | 44篇 |
1993年 | 40篇 |
1992年 | 89篇 |
1991年 | 73篇 |
1990年 | 67篇 |
1989年 | 72篇 |
1988年 | 56篇 |
1987年 | 52篇 |
1986年 | 54篇 |
1985年 | 49篇 |
1984年 | 48篇 |
1983年 | 37篇 |
1979年 | 40篇 |
1978年 | 22篇 |
1974年 | 27篇 |
1973年 | 24篇 |
1972年 | 25篇 |
1971年 | 30篇 |
1970年 | 35篇 |
1969年 | 28篇 |
1968年 | 30篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
I. Jiménez-Hidalgo G. Virgen-Calleros O. Martínez-de la Vega G. Vandemark V. Olalde-Portugal 《European journal of plant pathology / European Foundation for Plant Pathology》2004,110(3):317-331
Agave tequilana is the raw material for the production of the alcoholic beverage tequila. A bacterial disease has affected the A. tequilana crop in recent years. Previous reports based on colony and cell morphology, Gram stain and potato rot indicated that Erwinia sp. is the main pathogen. We isolated a several bacterial isolates capable of producing soft-rot symptoms in greenhouse pathogenicity assays. An extensive characterisation involving pathogenicity tests, fatty acid profile, metabolic and physiological properties, ribosomal DNA sequence and intergenic transcribed spacer amplification (ITS-PCR) and restriction banding pattern (ITS-RFLP) was made of each isolate. Three different species: Erwinia cacticida, Pantoea agglomerans and Pseudomonas sp. were identified. Fatty acid and metabolic profiles gave low similarity values of identification but 16S rDNA sequence, ITS-PCR and ITS-RFLP confirmed the identification of E. cacticida. In the phylogenetic tree, E. cacticida from blue agave was grouped neither with E. cacticida type strains nor with Erwinia carotovora. This is the first report that associates E. cacticida with A. tequilana soft-rot symptoms. 相似文献
42.
43.
44.
45.
A. Lecoindre D. Saade P. Barthez J. L. Cadoré P. Lecoindre 《The Journal of small animal practice》2018,59(5):311-314
A one‐year‐old female cocker spaniel presented with a 6‐month history of persistent diarrhoea. Abdominal ultrasonographic examination revealed mild diffuse thickening of the intestinal wall coupled with mesenteric lymphadenopathy. A connection between the duodenum and the colon was observed during an endoscopic procedure and confirmed by computed tomography. Surgical resection of the communication allowed remission of the diarrhoea. Histology showed a normal duodenal epithelium and muscular layer. A duodenocolic fistula is an abnormal connection within the digestive tract, which in humans is usually considered a complication of a local pathological condition. Due to the absence of a predisposing cause and, in view of the dog's age and histological results, a congenital origin was suspected. 相似文献
46.
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
47.
48.
A. T. Piñeiro-Vázquez G. Jiménez-Ferrer J. A. Alayon-Gamboa A. J. Chay-Canul A. J. Ayala-Burgos C. F. Aguilar-Pérez J. C. Ku-Vera 《Tropical animal health and production》2018,50(1):29-36
The aim of this work was to evaluate the effect of quebracho tannins extract (QTE) on feed intake, dry matter (DM) digestibility, and methane (CH4) emissions in cattle fed low-quality Pennisetum purpureum grass. Five heifers (Bos taurus × Bos indicus) with an average live weight (LW) of 295 ± 19 kg were allotted to five treatments (0, 1, 2, 3, and 4% QTE/kg DM) in a 5 × 5 Latin square design. Intake, digestibility, and total methane emissions (L/day) were recorded for periods of 23 h when cattle were housed in open-circuit respiration chambers. Dry matter intake (DMI), organic matter intake (OMI), dry matter digestibility (DMD), and organic matter digestibility (OMD) were different between treatments with 0 and 4% of QTE/kg DM (P < 0.05). Total volatile fatty acid and the molar proportion of acetate in the rumen was not affected (P < 0.05); however, the molar proportion of propionate increased linearly (P < 0.01) for treatments with 3 and 4% QTE. Total CH4 production decreased linearly (P < 0.01) as QTE increased in the diet, particularly with 3 and 4% concentration. When expressed as DMI and OMI by CH4, production (L/kg) was different between treatments with 0 vs 3 and 4% QTE (P < 0.05). It is concluded that the addition of QTE at 2 or 3% of dry matter ration can decrease methane production up to 29 and 41%, respectively, without significantly compromising feed intake and nutrients digestibility. 相似文献
49.
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
50.
Alejandro Alavez Ramírez Victor Manuel Meza Villalvazo Emmanuel Sosa Arredondo Hugo Alonso Ramírez Ramírez Héctor Magaña Sevilla 《Tropical animal health and production》2018,50(5):991-996
To compare the effects of PGF2α (dinoprost tromethamine) and d-cloprostenol in a two-dose protocol for estrus synchronization in hair sheep during breeding season in Yucatán, México, two experiments were conducted. In experiment 1, 61 cyclic hair sheep were divided into two groups: G1 (control n?=?30), two doses of 50 μg of dinoprost tromethamine IM with 12 days between applications, and G2 (n?=?31), two doses of 50 μg of d-cloprostenol IM at the same time interval. For determination of progesterone levels, 16 ewes from each group were randomly selected. In experiment 2, 70 cyclic hair sheep were assigned at the same treatments (G1 and G2, n?=?35) and 48 h after the second application, the ewes in estrus were detected by two vasectomized rams. Sheep with detected estrus were inseminated, and 45 days after, pregnant animals were identified by ultrasonography. An exact Fisher’s test was performed for the analysis of ewes in estrus (experiments 1 and 2) and number of pregnant ewes (experiment 2); for the comparison of time between end of treatment-estrus presentation, a survival analysis was used. Duration of estrus in hours was analyzed using a generalized mixed model (GLM) ANOVA whereas plasma progesterone concentrations were analyzed by non-linear regression. There were significant differences (P?<?0.05) in the proportion of ewes in estrus upon treatments (G1, 57% vs G2, 87% and G1, 37.1% vs G2, 65.7% in experiments 1 and 2, respectively), and between the end of treatment-onset estrus interval (P?<?0.01), survival curves showed the highest number of sheep in estrus between 40 and 48 h (G1, 43.7?+?8.05 h vs G2, 42.9?+?6.7 h, experiment 1). There were no significant differences (P?>?0.05) in duration of estrus (G1, 42?+?6.1 h, vs G2, 41.1?+?11.2 h, experiment 1) and pregnancy in the ewes that presented estrus, and were inseminated (G1, 38.4% vs 52.1%, experiment 2). With regard to concentrations of progesterone, significant differences (P?<?0.01) were found between treatments, and progesterone levels before the second application of d-cloprostenol were higher. In consideration of the results, it can be concluded that in a two-dose protocol of a luteolytic agent, more ewes presented estrus in response to d-cloprostenol compared to dinoprost tromethamine with similar pregnancy rates. 相似文献