全文获取类型
收费全文 | 603篇 |
免费 | 56篇 |
专业分类
林业 | 36篇 |
农学 | 8篇 |
基础科学 | 1篇 |
105篇 | |
综合类 | 53篇 |
农作物 | 26篇 |
水产渔业 | 34篇 |
畜牧兽医 | 340篇 |
园艺 | 4篇 |
植物保护 | 52篇 |
出版年
2024年 | 3篇 |
2023年 | 10篇 |
2022年 | 11篇 |
2021年 | 25篇 |
2020年 | 31篇 |
2019年 | 26篇 |
2018年 | 24篇 |
2017年 | 18篇 |
2016年 | 21篇 |
2015年 | 16篇 |
2014年 | 24篇 |
2013年 | 29篇 |
2012年 | 43篇 |
2011年 | 49篇 |
2010年 | 19篇 |
2009年 | 27篇 |
2008年 | 44篇 |
2007年 | 39篇 |
2006年 | 35篇 |
2005年 | 35篇 |
2004年 | 28篇 |
2003年 | 25篇 |
2002年 | 19篇 |
2001年 | 7篇 |
2000年 | 5篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 5篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1969年 | 1篇 |
1967年 | 1篇 |
1948年 | 1篇 |
1947年 | 2篇 |
1946年 | 1篇 |
1944年 | 1篇 |
1940年 | 1篇 |
排序方式: 共有659条查询结果,搜索用时 0 毫秒
11.
12.
13.
Myrthe Joosten Caroline Blaecher Bram Flahou Richard Ducatelle Freddy Haesebrouck Annemieke Smet 《Veterinary research》2013,44(1):65
Helicobacter (H.) heilmannii sensu stricto (s.s.) is a zoonotic bacterium that naturally colonizes the stomach of dogs and cats. In humans, this microorganism has been associated with gastritis, peptic ulcer disease and mucosa associated lymphoid tissue (MALT) lymphoma. Little information is available about the pathogenesis of H. heilmannii s.s. infections in humans and it is unknown whether differences in virulence exist within this species. Therefore, a Mongolian gerbil model was used to study bacterium-host interactions of 9 H. heilmannii s.s. strains. The colonization ability of the strains, the intensity of gastritis and gene expression of various inflammatory cytokines in the stomach were determined at 9 weeks after experimental infection. The induction of an antrum-dominant chronic active gastritis with formation of lymphocytic aggregates was shown for 7 strains. High-level antral colonization was seen for 4 strains, while colonization of 4 other strains was more restricted and one strain was not detected in the stomach at 9 weeks post infection. All strains inducing a chronic active gastritis caused an up-regulation of the pro-inflammatory cytokine IL-1β in the antrum. A reduced antral expression of H+/K+ ATPase was seen in the stomach after infection with 3 highly colonizing strains and 2 highly colonizing strains caused an increased gastrin expression in the fundus. In none of the H. heilmannii s.s.-infected groups, IFN-γ expression was up-regulated. This study demonstrates diversity in bacterium-host interactions within the species H. heilmannii s.s. and that the pathogenesis of gastric infections with this microorganism is not identical to that of an H. pylori infection. 相似文献
14.
The effect of pyrimethanil on the levels of cell wall degrading enzymes secreted by Botrytis cinerea Pers. was investigated in diseased plant tissues and in liquid B. cinerea cultures. Total proteinase activity isolated from infected carrot slices which were treated with 5.0 μM pyrimethanil was decreased by 76%, 3 d after inoculation. Polygalacturonase, cellulase, proteinase and laccase activities were all decreased in the medium of three day-old cultures grown in the presence of pyrimethanil. The pyrimethanil concentrations resulting in 50% reduction in total enzyme activities (IC50) were approximately 0.25 μM for polygalacturonase, cellulase and proteinase, and approximately 1.0 μM for laccase. No significant growth inhibition was observed at these pyrimethanil concentrations. Pyrimethanil did not inhibit the enzymes directly, nor did it inhibit the synthesis of cytosolic proteins. Therefore, it was proposed that the fungicide inhibits protein secretion at a post-translational stage in the secretory pathway. Large differences were found in the effects of pyrimethanil on the growth of B. cinerea in liquid cultures and on agar plates, depending on the composition of the medium. In liquid media containing cellulose and protein as carbon and nitrogen sources, growth inhibition occurred at 5.0 μM pyrimethanil, whilst no growth inhibition was observed with 50 μM pyrimethanil in malt extract. Similarly, growth occurred on potato/dextrose agar (PDA) at 0.5 μM pyrimethanil, but no growth was seen at this concentration on agars containing cellulose and protein. Thus it appears that pyrimethanil is most active in media where the fungus has to utilise extracellular enzymes to mobilise the nutrients it requires for growth. 相似文献
15.
16.
17.
Denise C. Lambkin Kerry H. Gwilliam Caroline Layton Matt G. Canti Trevor G. Piearce Mark E. Hodson 《Pedobiologia》2011
Earthworms secrete granules of calcium carbonate. These are potentially important in soil biogeochemical cycles and are routinely recorded in archaeological studies of Quaternary soils. Production rates of calcium carbonate granules by the earthworm Lumbricus terrestris L. were determined over 27 days in a range of soils with differing chemical properties (pH, organic matter content, water holding capacity, bulk composition, cation exchange capacity and exchangeable cations). Production rate varied between soils, lay in the range (0–4.3 mg) earthworm?1 d?1 with an average rate of (0.8 mg) earthworm?1 d?1 and was significantly correlated (r = 0.68, P ≤ 0.01) with soil pH. In a second experiment lasting 315 days earthworms repeatedly (over periods of 39–57 days) produced comparable masses of granules. Converting individual earthworm granule production rates into fluxes expressed on a per hectare of land per year basis depends heavily on estimates of earthworm numbers. Using values of 10–20 L. terrestris m?2 suggests a rate of . Data obtained from flow-through dissolution experiments suggest that at near neutral pH, granule geometric surface area-normalised dissolution rates are similar to those for other biogenic and inorganic calcites. Fits of the data to the dissolution relationship r = k(1 ? Ω)n where r = dissolution rate, k = a rate constant, Ω = relative saturation and n = the reaction order gave values of k = 1.72 × 10?10 mol cm?2 s?1 and n = 1.8 for the geometric surface area-normalised rates and k = 3.51 × 10?13 mol cm?2 s?1 and n = 1.8 for the BET surface area-normalised rates. In 196 day leaching column experiments trends in granule dissolution rate referenced to soil chemistry corresponded to predictions made by the SLIM model for dissolution of limestone in soil. If soil solution approaches saturation with respect to calcium carbonate, granule dissolution will slow or even stop and granules be preserved indefinitely. Granules have the potential to be a small but significant component of the biogeochemical cycling of C and Ca in soil. 相似文献
18.
Ilyas Siddique Caroline Gutjahr Gamini Seneviratne Broder Breckling Sudheera W. Ranwala Ian J. Alexander 《Biology and Fertility of Soils》2007,44(1):163-170
Topsoil properties were determined in forest gardens established about 20 years ago on eroded grassland soils (abandoned tea
lands) in the wet zone of the Sri Lankan highlands. They were compared with adjacent, eroded grasslands (abandoned tea lands)
on strongly weathered soils vs soils at earlier stages of pedogenic development in a two-way analysis of variance. Soil pH
in forest gardens was, on average, 6.1, nearly one unit higher than in the adjacent grasslands. In the garden soils, the cation
exchange capacity (CEC measured at pH 4.8) was nearly double, exchangeable calcium concentrations five times and exchangeable
magnesium three times as high as in the grasslands soils. Total soil N content was found to be nearly 40% higher in the gardens.
Topsoil gravel contents in the gardens were less than half as high as in the grasslands. The increases in exchangeable bases
and N in gardens, relative to grasslands, were attributed to increased nutrient retention and acquisition. Higher retention
was partly due to the higher CECpH4.8, and probably to reduced erosion and increased, continuous fine root density in the garden topsoils. Higher field CEC in
gardens was likely to result from generally higher C contents and from the reversal of acidification, presumably caused by
base accumulation and decomposition processes. Our results suggest that forest garden establishment on degraded grasslands
can lead to accumulation of mobile nutrients in the topsoil, probably due to increased nutrient retention, subsoil uptake
and litter input exceeding nutrient uptake by the standing biomass. 相似文献
19.
20.
Audrey G. Quentin Elizabeth A. Pinkard Christopher L. Beadle Timothy J. Wardlaw Anthony P. O’Grady Stephen Paterson Caroline L. Mohammed 《Annals of Forest Science》2010,67(2):203-203