全文获取类型
收费全文 | 534篇 |
免费 | 35篇 |
专业分类
林业 | 27篇 |
农学 | 6篇 |
基础科学 | 3篇 |
106篇 | |
综合类 | 77篇 |
农作物 | 20篇 |
水产渔业 | 26篇 |
畜牧兽医 | 264篇 |
园艺 | 16篇 |
植物保护 | 24篇 |
出版年
2023年 | 8篇 |
2022年 | 8篇 |
2021年 | 11篇 |
2020年 | 11篇 |
2019年 | 26篇 |
2018年 | 6篇 |
2017年 | 7篇 |
2016年 | 13篇 |
2015年 | 8篇 |
2014年 | 15篇 |
2013年 | 22篇 |
2012年 | 28篇 |
2011年 | 24篇 |
2010年 | 15篇 |
2009年 | 11篇 |
2008年 | 19篇 |
2007年 | 22篇 |
2006年 | 28篇 |
2005年 | 19篇 |
2004年 | 18篇 |
2003年 | 16篇 |
2002年 | 14篇 |
2001年 | 8篇 |
2000年 | 10篇 |
1999年 | 9篇 |
1998年 | 4篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 4篇 |
1984年 | 6篇 |
1983年 | 9篇 |
1981年 | 4篇 |
1979年 | 17篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1974年 | 7篇 |
1973年 | 6篇 |
1972年 | 7篇 |
1971年 | 6篇 |
1970年 | 5篇 |
1969年 | 8篇 |
1967年 | 4篇 |
1945年 | 3篇 |
1942年 | 3篇 |
1939年 | 4篇 |
1938年 | 3篇 |
排序方式: 共有569条查询结果,搜索用时 15 毫秒
101.
B. J. Malcolm K. C. Cameron H. J. Di G. R. Edwards J. L. Moir 《Soil Use and Management》2014,30(1):58-68
Nitrate () leaching can cause elevated concentrations of ‐N in water, which can have adverse impacts on water quality and human health. In grazed pasture systems, most of the ‐N leaching occurs beneath animal urine‐N deposits. The objective of this study was to investigate the effect of four different pasture species compositions [perennial ryegrass/white clover (P. ryegrass WC), tall fescue/white clover (T. fescue WC), Italian ryegrass/white clover (It. ryegrass WC) and perennial ryegrass/Italian ryegrass/white clover/red clover/chicory/plantain (Diverse)] on ‐N leaching losses from animal urine patches, and to examine the relative importance of root system architecture and seasonal activity to reduce ‐N leaching losses. The results show that ‐N leaching losses were 24–54% lower beneath It. ryegrass WC than other pasture species. Total dry matter (DM) yield in the season following establishment was 11–58% greater in the It. ryegrass WC pasture, while average winter daily N uptake rate of It. ryegrass WC over the two seasons was on average 58% greater than P. ryegrass WC and T. fescue WC. In the second season, the P. ryegrass WC and T. fescue WC pastures had up to 140 and 82% more roots between 0 and 40 cm depth, respectively, than the other pasture species compositions. These results suggest that in grazed pasture systems, high plant winter activity (plant growth/root metabolic activity) is more important than specific root architecture (e.g. deep roots) to reduce ‐N leaching losses. 相似文献
102.
This study considered the effects of thinning on the development of compression wood in stems of 35-year-old stand of Corsican
pine (Pinus nigra L.). Part of the stand had been thinned at 5-yearly intervals and part left unthinned. Twenty trees each from the thinned
and unthinned stands were randomly selected and felled. Measurements were made on tree height, stem diameter, stem slenderness
and canopy depth. Wood samples were removed from the central part of the main log and cross-sectional measurements made on
ring width, basic density and compression wood content. Cross-sectional area of compression wood was found to be three time
higher in stems from the unthinned trees in comparison with those from the thinned trees. No significant differences in mean
radial ring width or basic density were found between treatments. Correlations indicated that, with increasing in stem diameter,
compression wood content increased in the unthinned trees, while a decline in compression was observed in the thinned trees.
Tree height was also positively correlated with compression wood content in unthinned trees, while no equivalent relationship
was observed in thinned trees. Observations from this study, while not conclusive, suggest that phototropic stimulus may be
producing stem inclinations in the unthinned stand as trees compete for space in the canopy, whereas crown competition has
been largely eliminated in the thinned stand; and that this is responsible for compression wood levels recorded in this study. 相似文献
103.
D.P.C. Stewart K. C. Cameron I. S. Cornforth B. E. Main 《Biology and Fertility of Soils》2000,31(2):128-133
The release of SO4
2–-S, K+, Ca2+ and Mg2+ from soil amended with spent mushroom compost (SMC), a byproduct of mushroom production, was measured in leachate from field
lysimeters for 30 weeks. Rates of application were 0 and 80 t ha–1 moist SMC. The SMC contained 1.7% K, 6.5% Ca, 0.4% Mg and 1.2% S (of which 87% is SO4
2–-S), and has a C : S ratio of 26. The break-through curves of ion leaching were polymodal indicating the preservation of soil
structure in the lysimeters and its influence on leaching. SO4
2–-S release from SMC was rapid (first-order exponential) and was very similar to the release from a laboratory incubation.
The release of K+, Ca2+ and Mg2+ was described using first/zero-order models which were also used to describe their release in the laboratory. The rate and
amount of Ca2+ release was similar in the field and laboratory, but the amount of K+ (and to a lesser extent Mg2+) release was less in the field than in the laboratory. Recoveries of SMC applied nutrients in leachate were 80% of S (263 kg
ha–1), 3% of K (14 kg ha–1), 16% of Ca (284 kg ha–1) and 37% of Mg (40 kg ha–1). Little if any S was mineralised. Using SMC could provide plants with S, K, Ca and Mg but there is potential for SO4
2–-S losses via leaching.
Received: 7 April 1999 相似文献
104.
105.
Two epizootics of lymphocytic choriomeningitis virus occurring in laboratory mice despite intensive monitoring programs. 总被引:1,自引:0,他引:1 下载免费PDF全文
A L Smith F X Paturzo E P Gardner S Morgenstern G Cameron H Wadley 《Canadian journal of veterinary research》1984,48(3):335-337
Two epizootics of lymphocytic choriomeningitis virus in mice occurred within two months in one research facility consisting of several widely separated rooms. These outbreaks developed despite intensive institutional monitoring policies designed to prevent introduction and spread of lymphocytic choriomeningitis virus. Evidence derived from serological and virological assays and interviews with the concerned investigators suggested that a single transplantable tumor carried in mice may have been responsible for spread of the virus. However, the tumor was not contaminated with lymphocytic choriomeningitis virus at the time of its introduction into the mouse facility. The origin of the virus responsible for the outbreaks was not definitively established although data supported an hypothesis that the virus was introduced into the research facility by a wild or feral mouse. Virus spread from infected mice to humans did not occur, as measured by serological tests. However, a large and valuable animal facility was depopulated for safety reasons. Absorption of sera with lymphocytic choriomeningitis virus antigen proved a necessary and reliable method for confirming specificity of lymphocytic choriomeningitis virus fluorescence-positive reactions. 相似文献
106.
Acute nephropathy in young lambs 总被引:2,自引:0,他引:2
K W Angus J C Hodgson B D Hosie J C Low G B Mitchell D A Dyson A Holliman 《The Veterinary record》1989,124(1):9-14
Acute renal failure was diagnosed by clinical, necropsy and histological criteria in 39 flocks (20 low ground, 13 hill and six marginal upland) in areas served by six veterinary investigation centres. Forty-eight lambs of 12 different breeds or crosses were investigated. The mean age of affected lambs was 38 days (range seven to 84 days); 21 lambs (44 per cent) were aged seven to 28 days, while only eight (17 per cent) were older than two months. Mortality in clinically affected lambs was almost 100 per cent, with no response to various treatments. Histological examination showed that 40 lambs (83 per cent) had nephrosis, while the rest had toxic tubular necrosis, interstitial nephritis or tubular damage associated with oxalate crystal deposits. Only about half of the lambs had any evidence of enteric infections or enteropathy. Acutely ill lambs had azotaemia, haemoconcentration and proteinuria; some lambs had glycosuria or haematuria. Samples of plasma from 22 lambs with nephrosis were compared with similar samples from 82 incontact but asymptomatic lambs. The clinically affected group had significantly elevated plasma urea, creatinine, total protein, globulin, phosphorus and chloride concentrations and significantly reduced plasma calcium concentrations compared with healthy lambs. Affected lambs had a significant reduction also in the calcium:phosphorus ratio. No significant differences between groups was found in plasma concentrations of albumin, glucose, lactate, glycerol, creatine kinase, alkaline phosphatase, sodium, potassium or magnesium. 相似文献
107.
108.
109.
Prabhu Balan Yuan H. Brad Kim Adam D. Stuart Robert Kemp Maryaan Staincliffe Cameron Craigie Mustafa M. Farouk 《Animal Science Journal》2019,90(8):1060-1069
The objective of this study was to determine the effect of two different freezing rate then thaw‐aging regimens on the quality attributes of lamb loins. The loins were randomly allocated to one of five different freezing/thawing/aging regimes: fast‐(FF1A0) and slow‐(SF1A0) frozen only; fast‐(FF1A2) and slow‐(SF1A2) frozen then thaw‐aged for 14 days; aged for 14 days never frozen (A2). FF1A2 samples had a significantly higher water‐holding capacity compared to the slow frozen regardless of further aging periods. FF1A2 samples had lower (p < 0.05) shear force values than A2 and higher (p < 0.05) water‐holding capacity compared to the SF1A2. Fast freezing resulted in more intracellular cryo‐damage, whereas slow freezing resulted in extracellular cryo‐damage. FF1A0 and SF1A0 samples had lower (p < 0.05) myofibrillar proteins degradation. This study demonstrated that fast freezing then thaw‐aging can result in an improved water‐holding capacity and tenderness through the minimization of extracellular ice crystal formation, reduction in purge and drip losses, and improved proteolysis in thawed lamb. 相似文献
110.
Prabhu Balan Mustafa M. Farouk Adam D. Stuart Robert Kemp Maryaan Staincliffe Cameron Craige Yuan H. B. Kim 《Animal Science Journal》2019,90(8):1050-1059
The objective of this study was to create various pH/temp decline rates in hot‐boned bull beef M. longissimus lumborum (LL) through a combination of electrical stimulation (ES) and pre‐rigor holding temperature. The relationship between the pre‐rigor interventions, the activities of µ‐calpain and small heat shock proteins (sHSP), and the impacts on meat product quality were determined. Paired LL loins from 13 bulls were hot‐boned within 40 min of slaughter, immediately ES and subjected to various holding temperatures (5, 15, 25, and 35°C) for 3 hr. The rate of muscle pH decline, sarcomere length, shear force, and proteolysis of muscle proteins were measured. ES‐25°C had a longer sarcomere length compared to non‐electrical stimulation samples. ES‐25°C and ES‐35°C samples had lower shear force values, higher µ‐calpain activity and higher desmin, troponin‐T, and sHSP degradation. The above findings suggest that pH/temp decline rates created in hot‐boned muscle impacted muscle protein proteolysis by increasing the activity of proteases and degradation of sHSP. 相似文献