全文获取类型
收费全文 | 74篇 |
免费 | 4篇 |
专业分类
林业 | 4篇 |
农学 | 3篇 |
1篇 | |
综合类 | 9篇 |
水产渔业 | 1篇 |
畜牧兽医 | 50篇 |
园艺 | 1篇 |
植物保护 | 9篇 |
出版年
2021年 | 1篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 1篇 |
2016年 | 2篇 |
2015年 | 1篇 |
2014年 | 7篇 |
2013年 | 8篇 |
2012年 | 1篇 |
2011年 | 3篇 |
2010年 | 4篇 |
2009年 | 6篇 |
2007年 | 1篇 |
2006年 | 2篇 |
2005年 | 4篇 |
2004年 | 2篇 |
2003年 | 1篇 |
2001年 | 1篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1988年 | 2篇 |
1985年 | 2篇 |
1976年 | 1篇 |
排序方式: 共有78条查询结果,搜索用时 109 毫秒
51.
TH Jones LJ Thompson JH Lawton TM Bezemer RD Bardgett TM Blackburn KD Bruce PF Cannon GS Hall SE Hartley G Howson CG Jones C Kampichler E Kandeler DA Ritchie 《Science (New York, N.Y.)》1998,280(5362):441-443
In model terrestrial ecosystems maintained for three plant generations at elevated concentrations of atmospheric carbon dioxide, increases in photosynthetically fixed carbon were allocated below ground, raising concentrations of dissolved organic carbon in soil. These effects were then transmitted up the decomposer food chain. Soil microbial biomass was unaffected, but the composition of soil fungal species changed, with increases in rates of cellulose decomposition. There were also changes in the abundance and species composition of Collembola, fungal-feeding arthropods. These results have implications for long-term feedback processes in soil ecosystems that are subject to rising global atmospheric carbon dioxide concentrations. 相似文献
52.
NN Kuzma P Khandelwal SE Barrett LN Pfeiffer KW West 《Science (New York, N.Y.)》1998,281(5377):686-690
Optically pumped nuclear magnetic resonance (OPNMR) measurements were performed in two different electron-doped multiple quantum well samples near the fractional quantum Hall effect ground state nu = 13. Below 0.5 kelvin, the spectra provide evidence that spin-reversed charged excitations of the nu = 13 ground state are localized over the NMR time scale of about 40 microseconds. Furthermore, by varying NMR pulse parameters, the electron spin temperature (as measured by the Knight shift) could be driven above the lattice temperature, which shows that the value of the electron spin-lattice relaxation time tau1s is between 100 microseconds and 500 milliseconds at nu = 13. 相似文献
53.
Characterisation of apple replant disease under South African conditions and potential biological management strategies 总被引:1,自引:0,他引:1
A possible biological origin of apple replant disease (ARD) in South Africa was investigated. Elements responsible for stunted growth and root discolouration could not be reduced to a level having no negative effect on apple seedlings by dilution of the original ARD field soils, with increased proportions of fumigated soil, from 100% to 25%. Pythium, Fusarium and Cylindrocarpon spp. were consistently isolated from all replant soils forming part of this study and Rhizoctonia spp. to a lesser degree, indicating that these fungi may play a role in ARD etiology in South Africa. Further research is needed, since identifications were not made to species level and no pathogenicity tests were performed. Nematodes implicated in ARD were inconsistently associated with the ARD soils tested, indicating only a secondary role. Furthermore, studies were conducted to investigate more environmentally friendly disease control alternatives to replace methyl bromide in ARD management. Applications of compost and compost extracts were identified as promising, practical tools for managing ARD, especially under the marginal production conditions of South African apple producing regions. In pot trials, the application of compost, as well as sterilised and unsterilised compost extracts, significantly increased growth of apple seedlings in ARD soils. Although results varied with addition of a slow release fertiliser, compost and compost extracts still significantly increased seedling growth parameters for several of the ARD soils tested, suggesting that they can ameliorate the effects of ARD, in addition to supplying nutrients. Three field trials were conducted in commercial orchards to verify pot trial results and to compare the impact of organic amendments on ARD severity with the standard fumigation control methods. Compost and mulch consistently increased shoot growth to the same or greater extent as the standard chemical treatments, for the 2-year trial period. 相似文献
54.
将岩青、轮叶棘豆等3种藏药材按一定比例配成复方,采用乙醇提取法进行提取,将浓缩药液用细胞维持液配制成1g/L的药液,并根据对兔肾细睁(PRK)安全浓度的测定结果,稀释成不同梯度浓度,分别与脓疱皮炎病毒(ORFV)加入到已培养24h的单层PRK中,通过M1TI’法测定OD值,分析其对ORFV病毒增殖的影响。经回归分析,复方药液在7.81—62·5mg/mL浓度范围内,药物浓度与活细胞存在线性关系,对病毒增势有显著的抑制作用(P〈0·05)。表明藏药材复方药液具有抗脓疱皮炎病毒感染的作用。 相似文献
55.
Makoto Mitsumori Hiroki Matsui Kiyoshi Tajima Takumi Shinkai Akio Takenaka Stuart E. Denman Christopher S. McSweeney 《Animal Science Journal》2014,85(1):25-31
Effect of the methane inhibitor, bromochloromethane (BCM) and dietary substrate, fumarate, on microbial community structure of acetogen bacteria in the bovine rumen was investigated through analysis of the formyltetrahydrofolate synthetase gene (fhs). The fhs sequences obtained from BCM‐untreated, BCM‐treated, fumarate‐untreated and fumarate‐treated bovine rumen were categorized into homoacetogens and nonhomoacetogenic bacteria by homoacetogen similarity scores. Phylogenetic tree analysis indicated that most of the fhs sequences categorized into homoacetogens were divided into nine clusters, which were in close agreement with a result shown in a self‐organizing map. The diversity of the fhs sequences from the BCM‐treated rumen was significantly different from those from BCM‐non‐treated rumen. Principal component analysis also showed that addition of BCM to the rumen altered the population structure of acetogenic bacteria significantly but the effect of fumarate was comparatively minor. These results indicate that BCM affects diversity of actogens in the bovine rumen, and changes in acetogenic community structure in response to methane inhibitors may be caused by different mechanisms. 相似文献
56.
Elizabeth M Ross Ben J Hayes David Tucker Jude Bond Stuart E Denman Victor Hutton Oddy 《Journal of animal science》2020,98(10)
Methane production from rumen methanogenesis contributes approximately 71% of greenhouse gas emissions from the agricultural sector. This study has performed genomic predictions for methane production from 99 sheep across 3 yr using a residual methane phenotype that is log methane yield corrected for live weight, rumen volume, and feed intake. Using genomic relationships, the prediction accuracies (as determined by the correlation between predicted and observed residual methane production) ranged from 0.058 to 0.220 depending on the time point being predicted. The best linear unbiased prediction algorithm was then applied to relationships between animals that were built on the rumen metabolome and microbiome. Prediction accuracies for the metabolome-based relationships for the two available time points were 0.254 and 0.132; the prediction accuracy for the first microbiome time point was 0.142. The second microbiome time point could not successfully predict residual methane production. When the metabolomic relationships were added to the genomic relationships, the accuracy of predictions increased to 0.274 (from 0.201 when only the genomic relationship was used) and 0.158 (from 0.081 when only the genomic relationship was used) for the two time points, respectively. When the microbiome relationships from the first time point were added to the genomic relationships, the maximum prediction accuracy increased to 0.247 (from 0.216 when only the genomic relationship was used), which was achieved by giving the genomic relationships 10 times more weighting than the microbiome relationships. These accuracies were higher than the genomic, metabolomic, and microbiome relationship matrixes achieved alone when identical sets of animals were used. 相似文献
57.
Twentieth-Century Sea Surface Temperature Trends 总被引:4,自引:0,他引:4
MA Cane AC Clement A Kaplan Y Kushnir D Pozdnyakov R Seager SE Zebiak R Murtugudde 《Science (New York, N.Y.)》1997,275(5302):957-960
An analysis of historical sea surface temperatures provides evidence for global warming since 1900, in line with land-based analyses of global temperature trends, and also shows that over the same period, the eastern equatorial Pacific cooled and the zonal sea surface temperature gradient strengthened. Recent theoretical studies have predicted such a pattern as a response of the coupled ocean-atmosphere system to an exogenous heating of the tropical atmosphere. This pattern, however, is not reproduced by the complex ocean-atmosphere circulation models currently used to simulate the climatic response to increased greenhouse gases. Its presence is likely to lessen the mean 20th-century global temperature change in model simulations. 相似文献
58.
ABSTRACT A growing literature has accumulated that points to the stability of industrial location patterns. Can this be reconciled with spatial dynamics? This article starts with the premise that demonstrable regularities exist in the manner in which individual industries locate (and relocate) over space. For Canada, spatial distributions of employment are examined for seventy‐one industries over a thirty‐year period (1971–2001). Industry data is organized by “synthetic regions” based on urban size and distance criteria. “Typical” location patterns are identified for industry groupings. Industrial spatial concentrations are then compared over time using correlation analysis, showing a high degree of stability. Stable industrial location patterns are not, the article finds, incompatible with differential regional growth. Five spatial processes are identified, driving change. The chief driving force is the propensity of dynamic industries to start up in large metro areas, setting off a process of diffusion (for services) and crowding out (for manufacturing), offset by the centralizing impact of greater consumer mobility and falling transport costs. These changes do not, however, significantly alter the relative spatial distribution of most industries over time. 相似文献
59.
T A Miller D L Denman G C Lewis 《Journal of the American Veterinary Medical Association》1985,187(8):839-841
A 4.5-year-old, neutered male ferret with a history of recurrent adenocarcinoma in the preputial region was given 2 radiation treatment courses designed to control the rapidly growing neoplasm. The tumor regressed completely after the first 3.5-week course of therapy. The ferret remained clinically disease-free for 4 months, at which time small masses were noticed in the inguinal area and the original tumor site. A second course of therapy was administered, which again resulted in complete clinical regression of the neoplasm. However, the duration of remission was brief. Local recurrence and abdominal metastasis were observed within 2 months of the completion of therapy. 相似文献
60.