全文获取类型
收费全文 | 634篇 |
免费 | 47篇 |
国内免费 | 1篇 |
专业分类
林业 | 27篇 |
农学 | 23篇 |
基础科学 | 8篇 |
83篇 | |
综合类 | 86篇 |
农作物 | 54篇 |
水产渔业 | 68篇 |
畜牧兽医 | 241篇 |
园艺 | 15篇 |
植物保护 | 77篇 |
出版年
2022年 | 9篇 |
2021年 | 9篇 |
2020年 | 7篇 |
2019年 | 22篇 |
2018年 | 15篇 |
2017年 | 16篇 |
2016年 | 25篇 |
2015年 | 18篇 |
2014年 | 10篇 |
2013年 | 36篇 |
2012年 | 52篇 |
2011年 | 56篇 |
2010年 | 29篇 |
2009年 | 36篇 |
2008年 | 45篇 |
2007年 | 43篇 |
2006年 | 42篇 |
2005年 | 28篇 |
2004年 | 31篇 |
2003年 | 24篇 |
2002年 | 21篇 |
2001年 | 9篇 |
2000年 | 8篇 |
1999年 | 7篇 |
1998年 | 2篇 |
1997年 | 5篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 9篇 |
1992年 | 7篇 |
1991年 | 9篇 |
1990年 | 3篇 |
1988年 | 3篇 |
1987年 | 6篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1974年 | 1篇 |
1972年 | 2篇 |
1970年 | 1篇 |
1969年 | 2篇 |
1960年 | 1篇 |
1930年 | 1篇 |
排序方式: 共有682条查询结果,搜索用时 34 毫秒
91.
Foster AP Naylor RD Howie NM Nicholas RA Ayling RD 《Veterinary journal (London, England : 1997)》2009,179(3):455-457
Signs of severe otitis media in 20% of dairy calves on one farm were associated with Mycoplasma bovis infection, based on isolation from the external ear canal and nares. Affected calves seroconverted to M. bovis and no other significant bacteria were isolated. Infection was considered likely to have originated from cows in the milking herd based on evidence of seroconversion and detection of infection in a milk sample. M. bovis infection should be considered when investigating otitis problems in calves. 相似文献
92.
Neil R Smalheiser Vetle I Torvik Amanda Bischoff-Grethe Lauren B Burhans Michael Gabriel Ramin Homayouni Alireza Kashef Maryann E Martone Guy A Perkins Diana L Price Andrew C Talk Ruth West 《Journal of Biomedical Discovery and Collaboration》2006,1(1):8
Arrowsmith is a unique computer-assisted strategy designed to assist investigators in detecting biologically-relevant connections between two disparate sets of articles in Medline. This paper describes how an inter-institutional consortium of neuroscientists used the UIC Arrowsmith web interface http://arrowsmith.psych.uic.edu in their daily work and guided the development, refinement and expansion of the system into a suite of tools intended for use by the wider scientific community. 相似文献
93.
Ozgen M Reese RN Tulio AZ Scheerens JC Miller AR 《Journal of agricultural and food chemistry》2006,54(4):1151-1157
The measurement of antioxidant capacity in fruits differs from that of other biological samples due to their low pH and very low lipophilic antioxidant capacity. In this report, we present a modified 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) method for fruits and compare its performance with the other commonly used antioxidant methods of 2,2'-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP). The antioxidant capacity and reaction kinetics of four phenolic compounds, two antioxidant standards, and five fruits were also investigated. The modified ABTS method prepared at a pH of 4.5 with sodium acetate buffer is highly stable and easily applied to fruit samples as compared to the standard (pH 7.4) version. The measured antioxidant capacity of samples varied with the assay method used, pH, and time of reaction. Traditional antioxidant standards (trolox, ascorbic acid) displayed stable, simple reaction kinetics, which allowed end point analysis with all of assays. Of the phenolic compounds examined, chlorogenic and caffeic acids exhibited the most complex reaction kinetics and reaction rates that precluded end point analysis while gallic acid and quercetin reached stable end points. All fruit extracts exhibited complex and varied kinetics and required long reaction times to approach an end point. Because the antioxidant capacity of fruit extracts is a function of the array of individual antioxidants present, accurate comparisons among fruit samples require that reaction times be standardized and of sufficient length to reach steady state conditions and that more than one assay be used to describe the total antioxidant activity of fruit samples. 相似文献
94.
Stefan Löfgren Neil Cory Therese Zetterberg Per-Erik Larsson Veronika Kronnäs 《Forest Ecology and Management》2009
Whole catchment liming or forest liming has been proposed and implemented as a countermeasure to the effects of elevated sulphur deposition. Since the end of the 1980s the Swedish Forest Agency has undertaken experimental forest liming experiments in selected catchments in southern Sweden. These studies were with low doses (3 tonnes ha−1) of lime (CaCO3) and dolomite (CaMg(CO3)2). Data from both soil samples and stream water samples have been collected for the 16 years following treatment. The stream data has been complemented with data from untreated catchments, from the Swedish monitoring stream network. Significant differences due to treatment were seen for Ca, cation exchange capacity (CEC) and base saturation (BS) in the humus layer, none of these variables showed a statistically significant change in the mineral soil due to treatment alone. Soil samples from both the treated and untreated sites showed temporal changes in both the humus layer and the mineral soils with increases in pH, Ca and CEC and decreases in BS and Al which were independent of treatment. A combination of treatment and time, gave significant changes in BS and TA down to 10 cm in the mineral soil. In the stream water samples no statistically significant differences were observed between treated and untreated sites. Regardless of treatment, the streams exhibited a general pattern of declining concentrations of SO4, Ca, sum of base cations (BC) and increasing acid neutralizing capacity (ANC). In summary, the application of a low dose of lime (3 tonnes ha−1) did not result in significant changes in surface water chemistry in the study catchments and changes in soil chemistry were mainly restricted to the humus layer during the 16 years following treatment. The natural recovery, as a result of reductions in sulphur deposition, dominated the effects and was clearly seen in both the treated and untreated study sites. MAGIC simulations indicate that this recovery will continue in the coming decades. 相似文献
95.
BACKGROUND: Seed treatments with the chloronicotinyl insecticide imidacloprid (Gaucho 600 FS) were evaluated to determine whether differences in concentration and exposure regime influence the germination and early growth of rice. RESULTS: Continuous exposure to imidacloprid (4 days at 2000 mg AI L(-1)) significantly (P < 0.001) reduced normal germination by an average of 18% across the 15 cultivars examined. Nine days after sowing, plants showed no adverse effects from continuous imidacloprid treatment during germination, with shoot lengths and root system dry weights equalling, or occasionally exceeding (P < 0.05), those of untreated plants. Short-term imidacloprid exposure (2 h at 2000 mg L(-1)) at initial seed wetting did not affect germination (P > 0.05), and short-term (1 h) exposure of 48 h pregerminated seed to imidacloprid (2000 mg L(-1)) similarly had no significant effect on early subsequent growth. Plants arising from 48 h pregerminated seed exposed to imidacloprid (1 h) at concentrations up to 4000 mg L(-1) immediately before sowing were not significantly different from control plants at either 9 or 25 days post-sowing. CONCLUSION: Results show that imidacloprid will have no adverse effects on plant growth if applied to pregerminated rice shortly before sowing. Continuous exposure of seed during germination had more pronounced effects, and the initial response of different cultivars was highly variable. Cultivars with high levels of sensitivity (such as IR72) require further testing before continuous exposure to imidacloprid during germination can be recommended. 相似文献
96.
Segner H Sundh H Buchmann K Douxfils J Sundell KS Mathieu C Ruane N Jutfelt F Toften H Vaughan L 《Fish physiology and biochemistry》2012,38(1):85-105
This brief review focuses on health and biological function as cornerstones of fish welfare. From the function-based point
of view, good welfare is reflected in the ability of the animal to cope with infectious and non-infectious stressors, thereby
maintaining homeostasis and good health, whereas stressful husbandry conditions and protracted suffering will lead to the
loss of the coping ability and, thus, to impaired health. In the first part of the review, the physiological processes through
which stressful husbandry conditions modulate health of farmed fish are examined. If fish are subjected to unfavourable husbandry
conditions, the resulting disruption of internal homeostasis necessitates energy-demanding physiological adjustments (allostasis/acclimation).
The ensuing energy drain leads to trade-offs with other energy-demanding processes such as the functioning of the primary
epithelial barriers (gut, skin, gills) and the immune system. Understanding of the relation between husbandry conditions,
allostatic responses and fish health provides the basis for the second theme developed in this review, the potential use of
biological function and health parameters as operational welfare indicators (OWIs). Advantages of function- and health-related
parameters are that they are relatively straightforward to recognize and to measure and are routinely monitored in most aquaculture
units, thereby providing feasible tools to assess fish welfare under practical farming conditions. As the efforts to improve
fish welfare and environmental sustainability lead to increasingly diverse solutions, in particular integrated production,
it is imperative that we have objective OWIs to compare with other production forms, such as high-density aquaculture. However,
to receive the necessary acceptance for legislation, more robust scientific backing of the health- and function-related OWIs
is urgently needed. 相似文献
97.
Vanessa Schmidt Neil McEwan rea Volk John Helps Kevin Morrell Tim Nuttall 《Veterinary dermatology》2010,21(1):97-105
This double-blind randomized placebo-controlled trial indicates that Phytopica™ can be an effective glucocorticoid sparing agent in canine atopic dermatitis (AD). Twenty-two dogs with perennial AD [Canine Atopic Dermatitis with Severity Index (CADESI-03) ≥ 60] were given 200 mg/kg Phytopica™ or an identical placebo in food once daily for 56 days. All dogs were initially given 0.4 mg/kg methyl-prednisolone once daily, which was then adjusted according to the daily pruritus score (0–100 mm visual analogue scale). The cumulative dose and pruritus score were lower in the Phytopica™ than the placebo group. There were statistically significant time and treatment effects for the methyl-prednisolone dose and pruritus score, but there were no significant differences between the Phytopica™ and placebo groups in the proportion of dogs that achieved a > 50% reduction in dose or pruritus scores at day 56; the mean CADESI-03 scores at days 0, 28 and 56; the numbers achieving >50% reduction in CADESI-03 at days 28 and 56; or in the owners' global efficacy score at days 28 and 56. Adverse events included diarrhoea (three Phytopica™ and one placebo treated dog), polyuria/polydipsia (three dogs in each group), and polyphagia, intermittent anorexia and panting (one dog each in the placebo group). None of these by themselves required withdrawal of treatment. 相似文献
98.
Jennifer Fazakerley Nicola Williams Stuart Carter Neil McEwan Tim Nuttall 《Veterinary dermatology》2010,21(6):578-585
Staphylococcus pseudintermedius is part of the normal canine flora but frequently causes pyoderma in canine atopic dermatitis (AD). This study aimed to determine whether particular S. pseudintermedius strains were associated with AD and/or pyoderma. Ninety‐six S. pseudintermedius isolates from the ear, nares, perineum and lesions of 21 atopic and 16 healthy dogs were lysed with proteinase K and digested with 40 U SmaI. Restriction products were separated using pulsed‐field gel electrophoresis (PFGE) with an Oxford S. aureus control and lambda‐ladder DNA concatomer markers. A dendrogram was constructed by the unweighted pair group method. All isolates showed a ≥56% similarity coefficient. Nine distinct PFGE clusters were identified, as follows: five from both atopic and healthy dogs; three from atopic dogs only; and one from healthy dogs only. Nine clusters were isolated from the nares, eight from the perineum, five from the ears and six from pyoderma lesions. There were no significant differences in the frequency of isolation from atopic or healthy skin, body sites or infected lesions for any of the clusters. Two of six healthy dogs and 18 of 20 atopic dogs with multiple isolates had closely related isolates (less than three band differences) at more than one sampling site. Isolates from pyoderma lesions were closely related to at least one mucosal isolate in 11 of 16 dogs. Staphylococcus pseudintermedius isolates appear to be heterogeneous, and colonization or infection of atopic skin was not associated with any particular strain or cluster of strains. 相似文献
99.
Paige DA Siegler MA Zhang JA Hayne PO Foote EJ Bennett KA Vasavada AR Greenhagen BT Schofield JT McCleese DJ Foote MC DeJong E Bills BG Hartford W Murray BC Allen CC Snook K Soderblom LA Calcutt S Taylor FW Bowles NE Bandfield JL Elphic R Ghent R Glotch TD Wyatt MB Lucey PG 《Science (New York, N.Y.)》2010,330(6003):479-482
Diviner Lunar Radiometer Experiment surface-temperature maps reveal the existence of widespread surface and near-surface cryogenic regions that extend beyond the boundaries of persistent shadow. The Lunar Crater Observation and Sensing Satellite (LCROSS) struck one of the coldest of these regions, where subsurface temperatures are estimated to be 38 kelvin. Large areas of the lunar polar regions are currently cold enough to cold-trap water ice as well as a range of both more volatile and less volatile species. The diverse mixture of water and high-volatility compounds detected in the LCROSS ejecta plume is strong evidence for the impact delivery and cold-trapping of volatiles derived from primitive outer solar system bodies. 相似文献
100.
The success of tree plantings in agricultural landscapes within dry and variable rainfall regions is often below expectations.
The aims of this study were to investigate techniques for establishing a local native species (Eucalyptus pauciflora) and an exotic species (E. nitens) in the Midlands of Tasmania, a tree-denuded region that has been grazed for over 100 years in Australia. We established
trials at the Sorrel Springs and Woodland Park properties. We compared six establishment techniques: control; understorey
nurse planting; spot burn; mulch; tree-guard and; self-watering tree-guard. Three months, 1 and 6 years after planting we
measured tree height, health index and mortality. At Sorrell Springs tree-guarded treatments had greater height than other
treatments at year one, but there were no effects of treatment at year six on height, health or mortality. At Woodland Park
mulch, burn and tree-guarded treatments had greater height 1 and 6 years after planting. At year six tree-guarded treatments
had lower mortality than other treatments. At Sorrell Springs height of E. nitens was greater than E. pauciflora at year one but not at year six. At Woodland Park height of E. nitens was generally greater at year six but having almost double the incidence of mortality relative to E. pauciflora. We conclude that expensive tree-guarding is only warranted where high browse pressure is expected and that on such sites
species with tough leaves that are resistant to browsing should be considered. Further that in environments marginal for growing
trees, best practice establishment technique is generally as effective as additional treatments of understorey nurse planting,
spot burning or mulching. 相似文献