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排序方式: 共有91条查询结果,搜索用时 15 毫秒
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E. J. HALL 《The Journal of small animal practice》1991,32(7):362-362
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HALL AI 《The British veterinary journal》1947,103(11):392-394
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生物炭和堆肥提高西澳大利亚沙质平原土壤上的作物产量但这种效应是短期的 总被引:2,自引:0,他引:2
Sandplain soils on the south coast of Western Australia
have low inherent fertility, which is mainly due to poor
nutrient retention caused by insufficient clay and organic
colloidal material. Previous research has shown the
benefits in nutrient levels and retention from adding clay
to sandplain soils; however, there is almost no information
on the addition of organic amendments. A field experiment
was established at the Esperance Downs Research Station,
Western Australian, in May 2010, to assess the effects of
wheat straw (WS) and chicken manure (CM) biochars and
compost with and without phosphorus (P) addition on soil
properties and crop production over five growing seasons.
The five seasons alternated between winter and summer
crops.~The CM and WS biochar and compost treatments significantly
increased crop yields and P uptake in 3, 2 and 1 of the
five seasons, respectively. The yield increases $(P<0.05)$
were no more than 8\%. By the end of the third season, no
differences in crop yields were found that could be
attributed to the organic amendments. The addition of P
increased crop yields in each winter cropping season.
Phosphorus addition explained more than 30\% of the
variation in crop yields. Despite marginal P levels and
summer drought conditions, arbuscular mycorrhizal root
colonisation was not affected by the organic amendments.
There were no significant interactions between the organic
amendments and P addition in terms of crop yields, P uptake
or P uptake efficiency. We conclude that much of the effect
of the organic amendments was due to direct nutrient
addition which dissipated over time. 相似文献
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DANIEL C. KNUDSEN F. ROBERT JACOBS DENNIS CONWAY MEGAN K. BLAKE 《Growth and change》1994,25(2):183-205
This paper presents results of a hierarchical, fixed-question survey that sought responses about flexible machining cells, flexible labor cells, and concurrent changes in plant operations among nonelectrical machinery manufacturers in Illinois, Indiana, Michigan, Ohio, and Wisconsin. General results indicate that the majority of firms in the American Midwest do not possess flexible manufacturing capability. Of those that do possess this capability, most adopted flexible labor cells prior to adopting flexible machining cells. These cells are small, employing relatively few workers and producing a limited line of products. While the adoption process has been plagued with training, scheduling, and integration problems, most plant managers are pleased with the performance of their flexible manufacturing cells. Management has been reluctant to break out of traditional relationships with suppliers, to trim levels of management and to explore strategic alliances with competitors. Survey results are disaggregated by year, size, positon-in-organization, and by union affiliation. 相似文献
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A recording penetrometer to measure the strength of soil in relation to the stresses exerted by a walking cow 总被引:1,自引:0,他引:1
A penetrometer has been designed for field use to simulate the stresses exerted on the ground by the hoof of a walking cow, and to measure the resulting deformation of the soil. The extent of deformation produced by the penetrometer in two intact topsoils under pasture was found to be small and independent of water content, whilst significant correlations between soil strength and water content were obtained using a cone penetrometer and a hand-held shear vane. The results imply that the deep hoofprints associated with poached pasture are not produced immediately upon treading wet soil, but only after a progressive loss of soil strength due to repeated treading. Thus the rate of loss, which is deduced to be a measure of the susceptibility of pasture to poaching, cannot be estimated directly from a single measure of soil strength. 相似文献
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