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排序方式: 共有199条查询结果,搜索用时 15 毫秒
191.
A Wolfe S Hogan D Maguire C Fitzpatrick L Vaughan D Wall T J Hayden G Mulcahy 《The Veterinary record》2001,149(25):759-763
Intestinal washes, faecal flotations and serological examinations for antibodies to Toxoplasma gondii and Neospora caninum were used to assess the prevalence of parasites in carcases of foxes killed on roads or shot in the Dublin area and surrounding counties. The ascarids Uncinaria stenocephala and Toxocara canis were prevalent, as was the trematode Alaria alata. Taenia species, eggs of Capillaria species and sporocysts of Sarcocystis species were also found. Only one fox out of 70 examined was seropositive for N. caninum, whereas 24 of 51 were seropositive for T. gondii. 相似文献
192.
As a soilless system, hydroponics eliminates competing weeds and soil-born pests while conserving water and providing conditions that can be quickly altered to suit specific crops. However, stress-induced physiological conditions may arise within the system from factors such as mechanical injury, pests, or inconsistent nutrient flow rates that result in some plants receiving too much or too little water. Most abiotic stress conditions result in increased production of the plant hormone ethylene. High levels of ethylene inhibit growth, cause premature ripening, and induce the onset of senescence, potentially reducing the productivity of hydroponically-grown crops. In this study, we demonstrate that assessing ethylene levels from leaves of hydroponically-grown strawberry plants can be used as an early indicator of stress conditions. Our results demonstrate that there is no significant correlation between ethylene production and temperatures ranging from 15 to 37 °C or with light intensities ranging from 63 to 1500 μmol m−2 s−1. However, an increase in ethylene production tended to be positively correlated with sampling time; levels were higher during midday compared to early morning or later afternoon. The daily ethylene fluctuations under greenhouse conditions due to sampling time, light intensity, or temperature changes were not significantly high enough to indicate stress conditions. Overall, three system analyses showed altered ethylene production in plants farthest from the pump supplying the nutrient solution. This effect was interpreted to be caused by excess accumulation of nutrient solution around the plant roots, causing increased ethylene production in the leaves. Our results indicate that different watering patterns, manifested as pump pressure or drainage control, was the more difficult component to control in the design of these hydroponic systems. For example, in one system, an increase in ethylene production was measured for the position farthest from the pump, and resulted in those plants having a lower number of flowers and significantly reduced overall plant radii relative to the system average. In a separate experiment, plants from trays that had been flooded for 24 h showed a significant decrease in the plant radii and number of leaves and flowers 1 month after the flooding treatment. We conclude that system-wide ethylene measurements can be used to identify stressed plants within hydroponic systems. This type of analysis would be especially useful as an indicator of general stress conditions no matter the cause, identifying locations that may result in lower plant productivity. 相似文献
193.
Microencapsulating properties of sodium caseinate 总被引:5,自引:0,他引:5
Hogan SA McNamee BF O'Riordan ED O'Sullivan M 《Journal of agricultural and food chemistry》2001,49(4):1934-1938
Emulsions were prepared with 5% (w/v) solutions of sodium caseinate (Na Cas) and soy oil at oil/protein ratios of 0.25-3.0 by homogenization at 10--50 MPa. Emulsions were spray-dried to yield powders with 20--75% oil (w/w). Emulsion oil droplet size and interfacial protein load were determined. Microencapsulation efficiency (ME), redispersion properties, and structure of the powders were analyzed. The size of emulsion oil droplets decreased with increasing homogenization pressure but was not influenced by oil/protein ratio. Emulsion protein load values were highest at low oil/protein ratios. ME of the dried emulsions was not affected by homogenization pressure but decreased from 89.2 to 18.8% when the oil/protein ratio was increased from 0.25 to 3.0, respectively. Mean particle sizes of reconstituted dried emulsions were greater than those of the original emulsions, particularly at high oil/protein ratios (>1.0), suggesting destabilization of high-oil emulsions during the spray-drying process. 相似文献
194.
195.
John F. Burka Heather A. Briand Lisa M. Purcell Gregory A. Mitton Jeffrey G. Hogan William P. Ireland 《Fish physiology and biochemistry》1993,12(4):347-355
The effects of altered water temperature in vivo on in vitro smooth muscle contractility of rainbow trout intestine were investigated. Temperature has a significant effect on receptor-mediated
intestinal smooth muscle contractility in the rainbow trout. The efficacy of 5-HT, carbachol, and transmural stimulation increased
with temperatures above 10°C, with an optimal increase at 15°C. There was also a modest increase in the potency of 5-HT and
carbachol within 2 days of establishing trout at 20°C. By day 8, most of these changes had either stabilized or were returning
to control values, suggesting that acclimation changes in membranes and enzyme activities were taking effect. However, the
contractile responses to carbachol and transmural stimulation were still increasing at this time. This may imply that the
muscarinic receptors are more resistant to membrane acclimation changes and may take longer to adapt. Because these experiments
were controlled for handling stress and seasonal changes that affect contractility, we have been able to demonstrate some
early changes in smooth muscle contractility that occur during acclimation to altered temperature. 相似文献
196.
197.
Ruth H. True John M. Hogan Jorg Augustin S. R. Johnson C. Teitzel Ramses B. Toma Paul Orr 《American Journal of Potato Research》1979,56(7):339-350
The effect of several cooking methods on the mineral content of three major U.S. potato varieties was assessed. Significant losses of minerals in potato flesh were minimal and were unaccountably associated with the Norchip variety grown in the Red River Valley. The Irish potato was found to contribute significantly to the U.S. Recommended Dietary Allowance for copper, iron, magnesium, and phosphorus in the diet of man. 相似文献
198.
Slopes that have been disturbed through roadway, ski slope or other construction often produce more sediment than less disturbed sites. Reduction or elimination of sediment loading from such disturbed slopes to adjacent streams is critical in the Lake Tahoe basin. Here, use of a portable rainfall simulator (RS), described in the first paper of this series, is used to evaluate slope effects on erosion from bare volcanic and granitic soils (road cut and ski run sites) common in the basin in order to establish a basis upon which revegetation treatment comparisons can be made. Rainfall simulations (60 mm h−1, approximating a 100‐year, 15‐minute storm) at each site included multiple replications of bare soil plots as well as some adjacent ‘native’, or relatively undisturbed soils below trees where available. Field measurements of time to runoff, infiltration, runoff, sediment discharge rates, and average sediment concentration were obtained. Laboratory measurements of particle‐size distributions using sieve and laser counting methods indicated that the granitic soils had larger grain sizes than the volcanic soils and that road cut soils of either type also had larger grain sizes than their ski run counterparts. Particle‐size‐distribution‐based estimates of saturated hydraulic conductivity were 5–10 times greater than RS‐determined steady infiltration rates. RS‐measured infiltration rates were similar, ranging from 33–50 mm h−1 for disturbed volcanic soils and 33–60 mm h−1 for disturbed granitic soils. RS‐measured runoff rates and sediment yields from the bare soils were significantly correlated with plot slope with the exception of volcanic road cuts due to the narrow range of road cut slopes encountered. Sediment yields from bare granitic soils at slopes of 28 to 78 per cent ranged from ∼1 to 12 g m−2 mm−1, respectively, while from bare volcanic soils at slopes of 22 to 61 per cent they ranged from ∼3 to 31 g m−2 mm−1, respectively. Surface roughness did not correlate with runoff or erosion parameters, perhaps also as a result of a relatively narrow range of roughness values. The volcanic ski run soils and both types of road cut soils exhibited nearly an order of magnitude greater sediment yield than that from the corresponding native, relatively undisturbed, sites. Similarly, the granitic ski run soils produced nearly four‐times greater sediment concentration than the undisturbed areas. A possible goal of restoration/erosion control efforts could be recreation of ‘native’‐like soil conditions. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
199.
Revegetation of road cuts and fills is intended to stabilize those drastically disturbed areas so that sediment is not transported to adjacent waterways. Sediment has resulted in water quality degradation, an extremely critical issue in the Lake Tahoe Basin. Many revegetation efforts in this semiarid, subalpine environment have resulted in low levels of plant cover, thus failing to meet project goals. Further, no adequate physical method of assessing project effectiveness has been developed, relative to runoff or sediment movement. This paper describes the use of a portable rainfall simulator (RS) to conduct a preliminary assessment of the effectiveness of a variety of erosion‐control treatments and treatment effects on hydrologic parameters and erosion. The particular goal of this paper is to determine whether the RS method can measure revegetation treatment effects on infiltration and erosion. The RS‐plot studies were used to determine slope, cover (mulch and vegetation) and surface roughness effects on infiltration, runoff and erosion rates at several roadcuts across the basin. A rainfall rate of ≈60 mm h−1, approximating the 100‐yr, 15‐min design storm, was applied over replicated 0·64 m2 plots in each treatment type and over bare‐soil plots for comparison. Simulated rainfall had a mean drop size of ≈2·1 mm and approximately 70% of ‘natural’ kinetic energy. Measured parameters included time to runoff, infiltration, runoff/infiltration rate, sediment discharge rate and average sediment concentration as well as analysis of total Kjeldahl nitrogen (TKN) and dissolved phosphorus (TDP) from filtered (0·45 μm) runoff samples. Runoff rates, sediment concentrations and yields were greater from volcanic soils as compared to that from granitic soils for nearly all cover conditions. For example, bare soil sediment yields from volcanic soils ranged from 2–12 as compared to 0·3–3 g m−2 mm−1 for granitic soils. Pine‐needle mulch cover treatments substantially reduced sediment yields from all plots. Plot microtopography or roughness and cross‐slope had no effect on sediment concentrations in runoff or sediment yield. RS measurements showed discernible differences in runoff, infiltration, and sediment yields between treatments. Runoff nutrient concentrations were not distinguishable from that in the rainwater used. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献