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我国特大城市建成区土地集约利用研究 总被引:2,自引:0,他引:2
运用因子分析法对我国16个特大城市建成区的土地集约利用水平进行综合评价和排序.结果表明:我国特大城市建成区土地集约利用效率呈现总体水平偏低、地区差异明显及各大城市影响因素侧重点不同等3大特征.因此,需合理调整各大城市产业结构,以促进城市经济可持续发展;积极开展城市土地整理,以提高土地利用效率;加大城市生态环境保护力度,以优化土地利用生态效益. 相似文献
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The intensive breeding is often considered a risk of low welfare in dairy cows. Namely, the high yield has been suggested to be per se a cause of well-being reduction. Conversely, we have in many farms demonstrated that high milk yielding cows are not necessarily in a bad welfare condition, while many environmental and management problems can cause a distress situation and a reduced milk yield. To confirm these results, in an average yielding dairy farm affected by several problems, the welfare was assessed according to an Integrated Diagnostic System which considers health status, milk yield and quality, feeding strategy, blood profiles etc. The same check-up has been repeated a year later, after some attempts to correct main mistakes previously observed: dry and lactating cow diets, n° of cubicles, hygiene conditions, preparation and milking procedures etc. In one year only part of the mistakes have been fully corrected; nevertheless, the animal response was definitively improved suggesting a better welfare situation: improvement of teat and body condition (BCS) scores and reduction of open days, of legs and feet lesions and of somatic cell count (SCC : 283 vs. 456 cells/μl) as well as an increase of milk yield (25.2 vs. 20.1 kg/d).
Results confirmed that better breeding techniques can optimise the animal welfare and optimise milk yield in the intensive systems. 相似文献
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Effects of intensive fishing on the perch population in a large oligotrophic lake in eastern Finland
The perch population in Lake Höytiäinen was intensively fished to reduce the density of the population and hence also the predation pressure by perch on vendace larvae. A hypothesis suggests that this predation can prevent recovery of commercially important vendace stock from a state of low-density. In the 1990s the density of the perch population in Lake Höytiäinen has increased, while the vendace stock has been sparse. Intensive fishing was conducted by professional fishermen with a paired bottom trawl, seine net, hoop net and small fish traps and by recreational fishermen with small fish traps. The size of perch population during the intensive fishing period was studied by test fishing with multi-mesh gillnets and the Leslie method in which trawl YPUE was regressed on the cumulative yield. The results suggest that the population size clearly diminished in the area where the fishing pressure was strongest. YPUE of test fishing decreased ca. 30% whereas the Leslie method gave almost a decrease twice as large as that of the former. Mean weight of perch increased in the trawl and test fishing catches during the intensive fishing period. The most effective fishing gear was trawl (62% of the total yield), but importance of trap net fishing by recreational fishermen was also high as they caught 22% of the total yield. 相似文献
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从介绍我国草地生产的现状出发,着重讨论了发展集约化草地生产的重要性与技术对策,对集约化草地生产的内容、工艺过程及机械化技术装备的需求方向也进行了初步探讨。 相似文献
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通过烘烤试验对比,从烤房建造成本、运行参数、烘烤能耗用工、烤房控温精度、烤后烟叶外观质量、化学成分、经济效益等方面探索内置式生物质烤房、密闭式热泵烤房、光伏一体化烤房的烘烤效果,旨在为曲靖烟区筛选最适宜的烤房类型以及为烟草行业的绿色可持续发展提供理论依据。结果表明,密闭式热泵烤房烘烤能耗用工成本较低,控温精度、烤后烟叶质量、经济效益较好,是目前最适宜曲靖烟区的烤房类型;光伏一体化烤房建造成本高昂,且烘烤效果表现一般,目前推广难度较大,但可作为未来烤房的发展方向;内置式生物质烤房入门门槛较低,可在生物质颗粒供方市场成熟和电力配套设施不齐全的烟区加以应用。 相似文献
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在杉木分布北缘的苏南低山丘陵试验研究表明,利用萌芽杯幼龄速生的阶段优势,能发掘短轮伐小径材的生产潜力。影响萌芽林生长的因素主要有更新林分种源的遗传特性,立地条件,伐桩密度与更新方式。在山洼、山谷阴坡坡脚等优良立地,实施2250~2400株/桩·hmt2密度控制,小块状更新,集约肥培管抚,9年生萌芽林蓄积量达118.2~126.7m2/hm2,可产出约85%的小径材.在山坡中下部中等立地条件,实施较高密度(3000~3300株/桩·hm2)控制,窄带状(8~10m宽)更新,集约管抚,9~15年生蓄积量达111.7~139.6m3/hm2,可产出约40%的小径材和农用椽材。而在较差岗坡立地,即使采取高密度(4500株/桩·hm2:),窄带状荫芽更新与高水平集约管抚,也无生产小径材的可能。 相似文献