全文获取类型
收费全文 | 152篇 |
免费 | 15篇 |
专业分类
林业 | 3篇 |
农学 | 8篇 |
10篇 | |
综合类 | 17篇 |
农作物 | 8篇 |
水产渔业 | 14篇 |
畜牧兽医 | 99篇 |
园艺 | 1篇 |
植物保护 | 7篇 |
出版年
2023年 | 3篇 |
2020年 | 3篇 |
2019年 | 2篇 |
2018年 | 5篇 |
2017年 | 3篇 |
2016年 | 7篇 |
2015年 | 5篇 |
2014年 | 3篇 |
2013年 | 9篇 |
2012年 | 3篇 |
2011年 | 4篇 |
2010年 | 3篇 |
2009年 | 4篇 |
2008年 | 2篇 |
2006年 | 3篇 |
2005年 | 3篇 |
2004年 | 1篇 |
2003年 | 2篇 |
2002年 | 3篇 |
2001年 | 7篇 |
2000年 | 2篇 |
1999年 | 5篇 |
1998年 | 11篇 |
1997年 | 6篇 |
1996年 | 5篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1988年 | 2篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 4篇 |
1971年 | 1篇 |
1968年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有167条查询结果,搜索用时 46 毫秒
51.
52.
Gas chromatographic analysis of amino acids as the N-heptafluorobutyryl isobutyl esters 总被引:3,自引:0,他引:3
S L MacKenzie 《Journal of the Association of Official Analytical Chemists》1987,70(1):151-160
The N-heptafluorobutyryl isobutyl derivatives of proteic amino acids are well resolved by gas chromatography and form the basis of a convenient, rapid assay. The derivatives are prepared by acid-catalyzed esterification at 120 degrees C for 20 min in 3N HCl-isobutanol followed by acylation with heptafluorobutyric anhydride at 150 degrees C for 10 min. The reaction sequence is performed without any transfers or extractions and thus is compatible with microscale analysis. A complete proteic amino acid profile can be completed in less than 20 min by using a packed column or less than 10 min by using a capillary column in combination with an elevated oven temperature program rate. Physiological sample matrixes, which frequently contain a complex mixture of components, and thus require maximum resolution, can be assayed in less than 1 h using a program rate of 4 degrees C/min. A capillary column is recommended for this application. Capillary column chromatography, in combination with a nitrogen-specific detector, is useful for identifying and assaying nonproteic amino acids in physiological sample matrixes. Frequently, a prior cleanup of the sample can be avoided. 相似文献
53.
54.
Surface Deformation and Lower Crustal Flow in Eastern Tibet 总被引:99,自引:0,他引:99
LH Royden BC Burchfiel RW King E Wang Z Chen F Shen Y Liu 《Science (New York, N.Y.)》1997,276(5313):788-790
Field observations and satellite geodesy indicate that little crustal shortening has occurred along the central to southern margin of the eastern Tibetan plateau since about 4 million years ago. Instead, central eastern Tibet has been nearly stationary relative to southeastern China, southeastern Tibet has rotated clockwise without major crustal shortening, and the crust along portions of the eastern plateau margin has been extended. Modeling suggests that these phenomena are the result of continental convergence where the lower crust is so weak that upper crustal deformation is decoupled from the motion of the underlying mantle. This model also predicts east-west extension on the high plateau without convective removal of Tibetan lithosphere and without eastward movement of the crust east of the plateau. 相似文献
55.
Estimating the mass of asteroid 253 mathilde from tracking data during the NEAR flyby 总被引:1,自引:0,他引:1
DK Yeomans J Barriot DW Dunham RW Farquhar JD Giorgini CE Helfrich AS Konopliv JV McAdams JK Miller WM Owen DJ Scheeres SP Synnott BG Williams 《Science (New York, N.Y.)》1997,278(5346):2106-2109
The terminal navigation of the Near Earth Asteroid Rendezvous (NEAR) spacecraft during its close flyby of asteroid 253 Mathilde involved coordinated efforts to determine the heliocentric orbits of the spacecraft and Mathilde and then to determine the relative trajectory of the spacecraft with respect to Mathilde. The gravitational perturbation of Mathilde on the passing spacecraft was apparent in the spacecraft tracking data. As a result of the accurate targeting achieved, these data could be used to determine Mathilde's mass as 1.033 (+/- 0.044) x 10(20) grams. Coupled with a volume estimate provided by the NEAR imaging team, this mass suggests a low bulk density for Mathilde of 1.3 grams per cubic centimeter. 相似文献
56.
Miles CO Wilkins AL Stirling DJ MacKenzie AL 《Journal of agricultural and food chemistry》2003,51(16):4838-4840
Gymnodimine C (1), an oxidized analogue of the spiro-imine algal toxin gymnodimine (3), was isolated from extracts of the cells of Karenia selliformis. The structure of gymnodimine C, determined by one- and two-dimensional 1H NMR spectroscopy and mass spectrometry, was found to be isomeric with gymnodimine B (2) at C-18. 相似文献
57.
58.
D Aberdein JS Munday KE Dittmer RW Heathcott LA Lyons 《New Zealand veterinary journal》2013,61(6):327-331
Abstract
AIMS
To determine the frequency of the FAS-ligand gene (FASLG) variant associated with feline autoimmune lymphoproliferative syndrome (FALPS) and the proportion of carriers of the variant in three British shorthair (BSH) breeding catteries in New Zealand. 相似文献59.
Z S Browning A A Wilkes D S MacKenzie R M Patterson M W Lenox 《Journal of fish diseases》2013,36(11):911-919
Fish are becoming an increasingly important research species as investigators seek alternatives to mammalian models. Combined positron emission tomography/computed tomography with 18 F‐fluorodeoxyglucose (FDG‐PET/CT) is a powerful new technology that has been extensively applied for high‐resolution imaging in mammals but not fish. CT scanning provides detailed anatomical three‐dimensional imaging. PET scanning detects areas of cellular activity using radio‐labelled molecular probes with specific uptake rates appropriate to the tissue involved. FDG‐PET is used in oncology because tissues with high glucose uptake, such as neoplasms, are intensely radio‐labelled. PET/CT combines the two technologies, so that images acquired from both devices are merged into one superimposed image, thus more precisely correlating metabolic activity with anatomical three‐dimensional imaging. Our objective was to determine if fish can be viable replacement animals in cancer studies using this technique by analysing the similarities between fish and humans in glucose uptake in select organs across multiple fish species. Rapid, quantifiable glucose uptake was demonstrated, particularly in brain, kidneys and liver in all imaged fish species. Standard uptake values for glucose uptake in the major organ systems of fish were more similar to those of humans than mice or dogs, indicating that fish may serve as effective alternative animal models using this technology. Applications for this technique in fish may include oncogenesis and metabolism studies as well as screening for environmental carcinogenesis. 相似文献
60.
Earthworms are the major component of the soil fauna in temperate agro-ecosystems. Land use and soil management are widely reported to influence earthworm populations. We report simple laboratory experiments in which earthworm survival was tested against uniaxial loads for a range of soil conditions. Across all the experimental conditions 86% of earthworms survived. While greater loads (up to 800 kPa) over longer exposure times (up to 60 s) decreased survival; even under the most severe test conditions 33% of earthworms survived. Our results suggest that decreased earthworm populations in compacted soil are not due to uniaxial loading alone, but may be the result of shearing the soil during loading or from changes to the soil properties. 相似文献