全文获取类型
收费全文 | 1743篇 |
免费 | 186篇 |
专业分类
林业 | 119篇 |
农学 | 87篇 |
基础科学 | 5篇 |
329篇 | |
综合类 | 68篇 |
农作物 | 114篇 |
水产渔业 | 215篇 |
畜牧兽医 | 830篇 |
园艺 | 40篇 |
植物保护 | 122篇 |
出版年
2024年 | 2篇 |
2023年 | 26篇 |
2022年 | 42篇 |
2021年 | 91篇 |
2020年 | 99篇 |
2019年 | 106篇 |
2018年 | 115篇 |
2017年 | 112篇 |
2016年 | 112篇 |
2015年 | 73篇 |
2014年 | 111篇 |
2013年 | 114篇 |
2012年 | 129篇 |
2011年 | 137篇 |
2010年 | 75篇 |
2009年 | 74篇 |
2008年 | 66篇 |
2007年 | 77篇 |
2006年 | 48篇 |
2005年 | 56篇 |
2004年 | 45篇 |
2003年 | 39篇 |
2002年 | 34篇 |
2001年 | 21篇 |
2000年 | 24篇 |
1999年 | 18篇 |
1998年 | 8篇 |
1997年 | 6篇 |
1996年 | 3篇 |
1995年 | 5篇 |
1994年 | 3篇 |
1992年 | 4篇 |
1991年 | 11篇 |
1990年 | 5篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1971年 | 4篇 |
1970年 | 2篇 |
1969年 | 2篇 |
1967年 | 1篇 |
排序方式: 共有1929条查询结果,搜索用时 171 毫秒
51.
Gellasch KL Dá Costa Gómez T McAnulty JF Bjorling DE 《Journal of the American Veterinary Medical Association》2002,221(12):1719-23, 1714
Tracheal collapse is a common problem that is typically observed in middle-aged and older small-breed dogs. It is a structural, obstructive airway disease with a dynamic component that can affect the intra- and extrathoracic portions of the trachea and mainstem bronchi. Many methods of treatment have been suggested, including medical management and provision of extraluminal and intraluminal support. All techniques used to treat intrathoracic and mainstem bronchial collapse have been associated with major complications or limitations. This report describes the implantation of intraluminal nitinol stents to successfully treat intrathoracic as well as extrathoracic tracheal collapse in a dog. The stents are composed of material that has characteristics similar to those of the trachea; nitinol stents may provide a method of supporting intrathoracic tracheal and mainstem bronchial collapse in dogs. 相似文献
52.
Canada N Meireles CS Rocha A Sousa S Thompson G Dubey JP Romand S Thulliez P Correia da Costa JM 《Veterinary parasitology》2002,110(1-2):11-15
Neospora caninum was isolated from the brain of an aborted 4-month-old fetus from a dairy cow herd with endemic neosporosis in Porto, Portugal. The fetal brain homogenate was inoculated interperitoneally first into outbred Swiss Webster mice given dexamethasone and then the peritoneal exudates from these mice was co-inoculated with mouse sarcoma cells in the peritoneal cavity of mice given dexamethasone. N. caninum tachyzoites were seen in peritoneal exudate of the second passage. Tachyzoites from the peritoneal exudate reacted positively with anti-N. caninum antibodies and not with anti-Toxoplasma gondii antibodies and contained N. caninum specific DNA. This Portuguese isolate of N. caninum has been successfully maintained in cell culture. The dam of the aborted fetus had an antibody titer of 1:10240 in the Neospora agglutination test (NAT). Antibodies to N. caninum were found in 76 of 106 cows from this herd in titers of 1:40 in 31, 1:80 in 22, > or =1:160 or more in 23 in the Neospora agglutination test. This is the first isolation of a viable N. caninum-like parasite from any host in Portugal. 相似文献
53.
Costa CA Vieira LD Berne ME Silva MU Guidoni AL Figueiredo EA 《Veterinary parasitology》2000,88(1-2):153-158
The variability between and within breeds with respect to nematode egg counts (EPG), packed cell volume (PCV) and hemoglobin (Hb) was studied in 36 yearling female goats of the Caninde (15), Bhuj (6) and Anglo-Nubian (15) breeds, exposed to Haemonchus contortus. Nematode-free goats were turned to a contaminated paddock in late February. From then on, fecal egg per gram counts (EPG), packed cell volume (PCV) and hemoglobin (Hb) were determined at 2-week intervals up to Week 18. The EPG, transformed as [log(EPG + 75)], varied (P < 0.01) between goats within breeds and between weeks of exposure, but not between goat breeds (P > 0.05). PCV and Hb were affected by goat breeds (P < 0.05), by goats within breeds (P < 0.01) and by weeks of exposure (P < 0.01). Anglo-Nubians had higher (P < 0.01) PCV and Hb than Caninde; Bhuj had intermediate values. There were two EPG rises; one between Weeks 6 and 10 and the other between Weeks 14 and 16. The within breed variability was marked during the EPG rise on Week 6, when individual egg counts ranged from 130 to 2500. The EPG rises coincided with drops in Hb. PCV presented a similar trend, though not as marked. Haemonchus was responsible for more than 95% of nematode eggs counted. Considering the goat as experimental unit, the correlation coefficients (r) were: -0.45, P = 0.0064, between log(EPG + 75) and PCV; and -0.53, P = 0.0009, between log(EPG + 75) and Hb. The negative correlation between egg counts and blood values suggested breed differences in PCV and Hb were related to resistance to H. contortus infection and/or to its effects. 相似文献
54.
Carvalho R Passos LM Martins AS 《Journal of veterinary medicine. B, Infectious diseases and veterinary public health》2000,47(5):351-359
In this study, a multiplex polymerase chain reaction (PCR) procedure was developed for differentiation of strains and field isolates of equine herpesvirus type 1 (EHV-1) and type 4 (EHV-4). Specific oli-gonucleotide primers were combined to amplify the thymidine kinase (TK) gene region of EHV-1 and EHV-4, which would yield fragments of different lengths for each virus in the same amplification reaction. The specificity of the largest PCR amplicon for EHV-4 was confirmed by restriction digestion with HindIII. The multiplex PCR proved to be a fast and sensitive method for typing EHV-1 and EHV-4 isolates and for detection and differentiation of both viruses in field samples in which infectious virus is no longer available. The sensitivity was improved by combining cycling optimization and visualization of PCR products in ethidium bromide and silver-stained acrylamide gels. 相似文献
55.
Milene Miranda Praa Carlos Roberto Carvalho Wellington Ronildo Clarindo 《Scientia Horticulturae》2009,122(3):501-505
A relatively rapid, practical and reliable procedure for in vitro production of tetraploid tomato using colchicine is described. Using this procedure 11.11% generation of tetraploids was obtained after exposure of seedling shoot meristem explants with 8 mM colchicine for 96 h. Confirmation of tetraploid production (2n = 48), was determined by flow cytometry and verified by cytogenetic analysis of root tip preparations. The results indicate that the procedure is adequate for induction and screening of tetraploid tomato plantlets. 相似文献
56.
Density and Organic Matter Influence on Egg‐laying and Hatching of Branchiura sowerbyi (Oligochaeta)
Karine Cristiane Rech Renata Maria Guereschi Alex Pires de Oliveira Nuñer Sarah Carvalho Sticca 《Journal of the World Aquaculture Society》2013,44(2):267-272
This study aimed to assess the combined effects of density of adults of Branchiura sowerbyi and the source of organic matter on the production of eggs and young species. The experimental units used were 250‐mL beakers with 100 mL of fine sand (0.074–0.210 mm) and 150 mL of chlorine‐free water with constant aeration at the temperature 25 C. The experiment was conducted based on a two‐factor model with six treatments and three repetitions, applied in a completely random design. The densities 5 individuals/38.5cm2 (D5; 1298/m2) and 8 individuals/38.5cm2 (D8; 2078/m2) were assessed with commercial fish feed (FF), commercial poultry feed (PF), and turkey manure (TM) as sources of organic matter. A total of 1223 cocoons and 2138 eggs were produced, with average hatching of 40.0 ± 15.1%. The highest number of cocoons and eggs was found with the use of PF, D8 having produced the highest number of cocoons and eggs. The hatching rate was not influenced by the source of organic matter or density and no influence was registered from the density of adults on the survival. The PF provided the highest growth of adults, and generally the use of TM provided the worst performance. 相似文献
57.
58.
Costa JZ Adams A Bron JE Thompson KD Starkey WG Richards RH 《Journal of fish diseases》2007,30(7):419-426
The pepscan procedure was used to identify betanodavirus B-cell epitopes recognized by neutralizing mouse monoclonal antibodies (MAbs) and serum samples obtained from sea bass, Dicentrarchus labrax, naturally infected with betanodavirus. Pepscan was performed with a panel of thirty-four 12-mer synthetic peptides that mimicked the entire betanodavirus capsid protein. Sea bass serum samples reacted strongly with three regions of the capsid protein comprising amino acid residues 1-32, 91-162 and 181-212. The latter region was also recognized by neutralizing MAbs and coincided with a region of high antigenic propensity identified by an antigen prediction algorithm. These data suggest that a region of the betanodavirus capsid protein spanning amino acid residues 181-212 may represent a neutralization domain that could potentially be used to inform the development of nodavirus vaccines and immunodiagnostic reagents. 相似文献
59.
ent-Pimara-8(14),15-dien-19-oic acid (PA) isolated from Viguiera arenaria (Asteraceae; Heliantheae) inhibited rat carotid rings contraction induced by phenylephrine (10(-8) mol/l) or potassium chloride (45 mmol/l) at concentration ranging from 5 to 20 microg/ml. This inhibitory effect was not reversible after the removal of this compound from the medium bath. 相似文献
60.
Modelling cork oak production in Portugal 总被引:1,自引:0,他引:1
The layout of 32 permanent plots in the most important cork production regions of Portugal and the measurement of the most
representative tree parameters were performed for statistically sound cork weight modelling. The establishment of cork weight
equations is presented for the different cork oak study areas considered alone or grouped according to the most representative
tree parameters. For the presented cork weight models was chosen independent variable the total stripping surface (artmax). For the selection criteria five statistic were used, including PRESS, APRESS and Mallows's statistic. The crossvalidation
of the best classified models was performed and to discuss the importance of the “study area” factor, a regression analysis
with “dummy” variables was performed. 相似文献