全文获取类型
收费全文 | 12536篇 |
免费 | 958篇 |
专业分类
林业 | 1253篇 |
农学 | 475篇 |
基础科学 | 63篇 |
2893篇 | |
综合类 | 808篇 |
农作物 | 517篇 |
水产渔业 | 962篇 |
畜牧兽医 | 5020篇 |
园艺 | 342篇 |
植物保护 | 1161篇 |
出版年
2023年 | 104篇 |
2022年 | 137篇 |
2021年 | 262篇 |
2020年 | 256篇 |
2019年 | 195篇 |
2018年 | 589篇 |
2017年 | 554篇 |
2016年 | 523篇 |
2015年 | 412篇 |
2014年 | 478篇 |
2013年 | 732篇 |
2012年 | 964篇 |
2011年 | 909篇 |
2010年 | 514篇 |
2009年 | 415篇 |
2008年 | 798篇 |
2007年 | 732篇 |
2006年 | 600篇 |
2005年 | 615篇 |
2004年 | 568篇 |
2003年 | 527篇 |
2002年 | 427篇 |
2001年 | 297篇 |
2000年 | 278篇 |
1999年 | 246篇 |
1998年 | 84篇 |
1997年 | 67篇 |
1996年 | 49篇 |
1995年 | 70篇 |
1994年 | 45篇 |
1993年 | 43篇 |
1992年 | 85篇 |
1991年 | 74篇 |
1990年 | 65篇 |
1989年 | 66篇 |
1988年 | 60篇 |
1987年 | 49篇 |
1986年 | 48篇 |
1985年 | 48篇 |
1984年 | 43篇 |
1983年 | 36篇 |
1979年 | 37篇 |
1974年 | 26篇 |
1973年 | 21篇 |
1972年 | 22篇 |
1971年 | 23篇 |
1970年 | 27篇 |
1969年 | 25篇 |
1968年 | 25篇 |
1967年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 453 毫秒
51.
F Marco-Jiménez S Puchades E Mocé MP Viudes-de-Cartro JS Vicente M Rodriguez 《Reproduction in domestic animals》2004,39(6):438-441
Egg yolk is a common additive to sperm cryopreservation diluents. Because of its animal origin, however, it also represents a potential risk of microbiological contamination in the diluent. This potential contamination can be avoided by using powdered egg yolk, instead of fresh egg yolk, as it is pasteurized. This study was conducted to determine ram sperm cryosurvival was affected by the type of egg yolk used (powdered egg yolk or fresh egg yolk) and by yolk concentration (10, 15 or 20%) in the diluent. Microbiological analyses were also performed to quantify the microbiological contamination in the diluents containing the two types of egg yolk. Sperm cryosurvival was determined by motility and morphology analyses after thawing. Motility parameters were assessed using a computer-assisted sperm analysis (CASA) system, and the percentage of sperm with a normal apical ridge was evaluated using a differential interference contrast microscope. No significant differences were observed between diluents in the percentage of sperm with normal apical ridge. However, higher percentages of total motile cells were observed for samples containing powdered egg yolk (69%) compared to samples containing fresh egg yolk (60%). However, sperm in diluents containing fresh egg yolk, exhibited higher values for average-path velocity, straight-line velocity and beat cross frequency and lower values for amplitude of lateral head displacement (p <0.05), compared to cells in diluents containing powdered egg yolk. Microbiological contamination was similar (<200 CFU/ml) in both diluents, and no bacterial growth was observed in either, when antibiotics were added. Therefore, powdered egg yolk can be effective used in diluents for the freezing of ram semen. However, the in vivo fertility of sperm frozen in diluents containing powdered egg yolk should be tested, as some motility parameters were different for sperm treated with powdered egg yolk compared to fresh egg yolk. 相似文献
52.
D Gavier-Widén M N?remark S Benestad M Simmons L Renstr?m B Bratberg M Elvander C H?rd af Segerstad 《Journal of veterinary diagnostic investigation》2004,16(6):562-567
Within the framework of the active surveillance for transmissible spongiform encephalopathies in sheep in Sweden, 4 cases of the atypical form of scrapie, Nor98, were identified during 2003. Nor98 is a recently recognized and poorly understood variant of scrapie, first described in Norway. The cases were positive by the rapid test (enzyme-linked immunosorbent assay). Immunohistochemical staining showed diffuse thin-granular staining of the cerebellar cortex. Western immunoblotting analysis of specimens of brain stem and cerebellum showed a light band of approximately 12 kDa. Typical scrapie was ruled out based on the confirmatory testing. The affected ewes were from 4 different flocks. They were between 7 and 9 years old. Two were of the ARQ/ARQ genotype, 1 ARR/ARQ, and 1 ARR/AHQ. Two ewes had shown ataxia, and the other 2 had no clinical signs. Whole-flock slaughter was applied, and testing of the flock mates did not reveal additional cases. Nor98 differs from typical scrapie in its epidemiology, frequency of genotypes of sheep affected, clinical signs, microscopic lesions, distribution of scrapie prion protein in the brain, and characteristics of the immunostaining and immunoblotting profiles. 相似文献
53.
Adherence of Actinobacillus pleuropneumoniae serotype 1 to swine buccal epithelial cells involves fibronectin 下载免费PDF全文
Roberto Hamer-Barrera Delfino Godínez V. Idalia Enríquez Sergio Vaca-Pacheco Rodrigo Martínez-Zú?iga Patricia Talamás-Rohana Francisco Suárez-Güemez Mireya de la Garza 《Canadian journal of veterinary research》2004,68(1):33-41
The swine pathogen Actinobacillus pleuropneumoniae serotype 1 was investigated for its ability to adhere to swine, rat, and human buccal epithelial cells (BEC). The highest number of bacteria adhered was to swine BEC. This binding ability was affected by heating, extreme pH, treatment with sodium dodecyl sulfate, ethylenediamine tetraacetate, or periodate, and proteolysis, suggesting that cell-surface glycoproteins participate in adherence and that adherence is based mostly on ionic interactions. Mannose and swine fibronectin may play a direct role in this interaction. Convalescent-phase serum from naturally infected pigs inhibited the adhesion. There was a correlation between bacterial pathogenicity as well as host specificity and the capacity for adherence to swine BEC. Adhesion to swine BEC provides a convenient method to study in vitro the adherence of A. pleuropneumoniae and other pathogens of the pig respiratory tract. 相似文献
54.
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
55.
56.
Fracture of the medial intercondylar eminence of the tibia in horses treated by arthroscopic fragment removal (21 horses) 下载免费PDF全文
57.
58.
59.
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
60.
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