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71.
折旧是一定时期内(日、年)固定资产磨损价值转移到产品成本中去,以补偿固定资产所损耗的价值。随着社会经济的全球化发展,机械设备余额递减加速折旧的方法得到越来越广泛的使用。在此建立广义的余额递减法通用模型,提出了既适合于高倍余额递减法,又包含曾经已用的余额递减法和双倍余额递减法的模型,为农业机械费用的合理计算提供理论基础。 相似文献
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农机服务体系建设中的资源整合 总被引:1,自引:1,他引:1
在农机化的快速发展过程中,农机资源本身也需要以更多的实现形式进行平衡的资源优化配置和整合,以更好的投入产出水平发挥它在农业生产、加工中的作用,适应未来农机服务市场的变化. 相似文献
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沉湖湿地具有丰富的生物多样性,被誉为"湿地水禽遗传基因库",是大城市周边少有的淡水湖泊。加强保护、开发利用,促进生态平衡和观光旅游有着十分重要的意义。 相似文献
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以北京市1996~2014年郊区露地菜田1184份调研报告和161个土壤样本数据为基础,分析了京郊露地菜田施肥种类、施肥量、养分平衡、土壤有效养分的年际变化。结果表明:与20世纪90年代相比,现阶段露地菜田施用的有机肥由以厩肥、鸭粪和牛粪为主转为以鸡粪为主,化肥投入品种单一,偏施大量元素肥,缺少中微量元素补充;与20世纪90年代相比,尽管现阶段年施肥量明显减少,年养分盈余程度明显减轻,但养分投入量仍与作物吸收规律不符,N、P、K三大元素投入比例不合理,氮磷养分盈余的现象仍存在。经评价现阶段露地菜田土壤碱解氮缺乏,速效磷含量过高,有效钾适宜。 相似文献
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Adesola Odunayo DVM MS DACVECC Marie E. Kerl DVM MPH DACVIM DACVECC 《Journal of Veterinary Emergency and Critical Care》2011,21(3):236-241
Objective – To determine the difference between colloid osmotic pressure (COP) values determined from plasma versus those determined from whole blood. Design – Prospective observational study. Settings – University veterinary teaching hospital. Animals – Fifty‐three healthy dogs. Interventions – None. Measurements and Main Results – Whole blood and plasma COP, CBC, plasma biochemistry. In all dogs, plasma COP values were significantly lower (P=0.02) than whole blood COP, with a mean of difference of 0.5 mm Hg. The mean and median whole blood COP was 21.75 and 21.4 mm Hg, respectively, with a range of 17.9–27.1 mm Hg. The mean and median plasma COP was 21.2 and 20.9 mm Hg with a range of 16.7–28.9 mm Hg. Conclusions – While significant difference exists between plasma and whole blood COP, the individual values are within expected reference intervals for dogs (21–25 mm Hg). Using either sample appears to provide the same information in clinically healthy dog; however, it is recommended that clinicians utilize the same sample type for comparison in an individual patient. 相似文献
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选用4头年龄3.5岁,体况良好,体重(500±20)kg的中国西门塔尔牛阉牛。采用4×4拉丁方设计,研究日粮添加丙酸镁(100 g/d)、丙酸(87 g/d)和氧化镁(24 g/d)对西门塔尔牛氮平衡和能量平衡的影响。结果表明:日粮中添加丙酸镁、丙酸和氧化镁后,各组采食氮、采食总能、粪能、尿能、气体能、产热量、消化能/采食能差异均不显著(P>0.05);丙酸镁组粪氮较对照和氧化镁组显著降低(P<0.05);处理组尿氮较对照组显著降低(P<0.05),处理组间差异不显著(P>0.05);丙酸镁和丙酸组可消化氮和沉积氮、代谢能和沉积能较对照和氧化镁组显著提高(P<0.05),氧化镁组沉积氮较对照组显著提高(P<0.05)。丙酸镁组消化能、沉积能/消化能和沉积能/采食能较对照和氧化镁组显著提高(P<0.05)。丙酸镁降低了粪氮和尿氮,提高了可消化氮、沉积氮、消化能、代谢能、沉积能、沉积能/消化能、沉积能/采食能,改善了氮平衡和能量平衡。 相似文献
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Fyodor A. Tatarinov Emil CiencialaPetr Vopenka Vitaliy Avilov 《Forest Ecology and Management》2011,262(10):1919-1927
The simulation of forest production until 2100 under different environmental scenarios and current management practices was performed using a process-based model BIOME-BGC previously parameterized for the main Central-European tree species: spruce, pine, beech and oak and adapted to include forest management practices. Climatic scenario HadCM3 used in the simulations was taken from the IPCC database created within the 3rd Assessment Report. It was combined with a scenario of CO2 concentration development and a scenario of N deposition. The control scenario considered no changes of climatic characteristics, CO2 concentration and N deposition. Simulation experiment was performed for the test region - South Bohemia - using a 1 km × 1 km grid. The actual data on the regional forest cover were aggregated for each grid cell in such a way that each cell represented an even-aged single-dominant species stand or non-forested area, and a standard management scenario depending on the stand age and species was applied to each cell. The effect of environmental variables was estimated as the difference of simulated carbon pools and fluxes in 2050 under environmental changes and under control scenario.The model simulation for the period to 2050 with only climate change under constant CO2 concentration and N deposition indicated a small decrease of NPP (median values by species reached −0.9 to −1.7% for different species), NBP (−0.3 to −1.7%) and vegetation carbon (−0.3 to −0.7%), whereas soil C slightly increased. Separate increase of N deposition gave small positive effect on carbon pools (0.8-2.9% for wood C and about 0.5% for soil C) and more expressed effect on carbon fluxes (1.8-4.3% for NPP and 1.0-9.7% for NBP). Separate increase of CO2 concentration lead to 0.6-2.4% increase of wood C pool and 0.1-0.5% increase of soil C. The positive effects of CO2 concentration and N deposition were more pronounced for coniferous than for deciduous stands.Replacement of 0.5% of coniferous plantations every year by natural broadleaved stands evoked 10.5% of increase of wood carbon pool due to higher wood density of beech and oak compared to spruce and pine, but slightly decreased soil and litter carbon pools. 相似文献