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651.
应用质谱分析法鉴定桔梗皂甙类成分 总被引:8,自引:0,他引:8
对桔梗皂甙的化学成分进行了提取与纯化,首镒利用电喷雾质谱仪对桔梗皂甙类成分进行跟踪分析鉴定。通过对单体化合物各级激发产生碎片峰进行纵向分析及不同单体的横向对比分析,寻找桔梗皂甙类的结构规律,从而鉴定已知结构的皂甙成分,并为未知结构的成分提供信息。 相似文献
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653.
Parboiling involves soaking, steaming, and drying, and soaking is important in achieving desired parboiled rice properties. This study investigated the effects of soaking temperature and commingling on rice properties prior to steaming. Rough rice of four cultivars (Taggart, CL151, XL753, and CL XL745) and their combinations at 1:1 wt ratio were soaked at 65, 70 or 75 °C for 3 h, and dried. Both soaking temperature and difference in onset gelatinization temperature (To) of individual cultivars in commingled rice affected milling and physicochemical properties. The head brown rice yield was greater when the soaking temperature was below but close to the To for individual rice cultivars, but became difficult to predict for commingled rice. Commingled rice consisting of high To rice cultivars required higher soaking temperatures to reduce chalkiness during soaking. The color attributes of commingled rice was predominately affected by the cultivar that exhibited the most change. The gelatinization properties were governed by the low-To cultivar, whereas the pasting properties were more influenced by the high-To cultivar for the commingled rice. Therefore, using commingled rice with a wide range of gelatinization temperature as a feedstock may lead to inconsistent quality of parboiled rice. 相似文献
654.
不同土壤耕作法对作物产量及土壤硝态氮淋失的影响 总被引:30,自引:3,他引:30
针对华北平原小麦—玉米两熟区不同土壤耕法下玉米产量及玉米生育期土壤硝态氮迁移进行研究,结果表明,翻耕模式下玉米产量最高,免耕下最低。在0~180 cm土体中,收获期与苗期相比,翻耕硝态氮含量平均减少了66.6%;旋耕平均减少了21.7%;免耕则平均减少了20.9%。累积峰出现的深度与硝态氮淋失有直接关系。对比3种模式,翻耕累积峰最深,硝态氮淋失威胁最大;免耕无明显累积峰。在施肥、灌溉等影响硝态氮淋失的可控因子以外,从耕作模式上研究硝态氮淋失是今后研究的方向。 相似文献
655.
为进一步降低线损和提高供电可靠率,根据农村低压电力网的供电现状,提出配合单相小容量产品的单相二线、三线制供电方式。介绍低压单相供电的设计与实施方案,分析单相供电方式的电气性能、技术特点以及综合效益。 相似文献
656.
卷烟厂项目中大跨度厂房多采用网架结构体系,与网架结构体系对比,虽然采用大跨度钢桁架用钢量稍大,但能减少3m的层高,可以减少空调和采暖的能耗,从而达到节能的目的,获得长期效益。本文结合长春卷烟厂项目,根据反应谱法对屋盖结构在水平地震作用下的地震反应进行计算分析,并研究次应力及屋盖竖向支撑布置距离对桁架的影响。 相似文献
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658.
《Communications in Soil Science and Plant Analysis》2012,43(15-20):2171-2184
Abstract The concept of Precision farming is not new, and interest in the potential benefits gained momentum in the late eighties. The high cost of soil sampling and chemical and physical analysis by conventional laboratories has restricted the full implementation of this technique at the field level. Near infrared reflectance (NIR) could be a cost‐effective solution. Soil properties that have been calibrated include gravimetric soil water, clay content, buffer capacity, pH, electrical conductivity, titratable acidity, organic matter, mineralizable nitrogen, potential ammonia volatilization from urea, potential nitrification rate, and urease activity. A whole paradigm shift in philosophy is needed in soil testing to move away from the traditional approach of taking a perceived‐representative sample, in which all the spatial variation is lost, to using a combination of grid soil sampling at a sample intensity of 4 to 10 cores per ha and analysed separately using rapid but less accurate methods such as NIR. 相似文献
659.
Jiménez‐Segura LF, Palacio J, Leite R. River flooding and reproduction of migratory fish species in the Magdalena River basin, Colombia.Ecology of Freshwater Fish 2010: 19: 178–186. © 2010 John Wiley & Sons A/S Abstract – In most tropical rivers subject to a single‐yearly flooding, migratory fish usually spawn in the onset of the flooding and larvae drift to their nursery habitats. To define when the migratory fish species reproduce, its relationship with the water level and when nursery areas in floodplain lakes are supplied with ichthyoplankton in the Magdalena River, a two‐yearly peak flooding river, we sampled the ichthyoplankton weekly throughout 2 years. The fish species Pseudoplatystoma magdaleniatum, Prochilodus magdalenae, Leporinus muyscorum, Sorubim cuspicaudus and Curimata mivartii spawn twice a year in the main channel and its larvae input into the floodplain lakes are not always associated with flooding. Spawning in the main channel and larvae inputs into the floodplain lakes suggest that the habitat used by the migratory fishes may be consistent with some hypotheses on habitats used by these fishes. 相似文献
660.
K型杂种小麦灌浆特性研究 总被引:1,自引:0,他引:1
对4个K型杂种小麦和其对应的父本(即常规品种)的灌浆特性进行了对比研究。结果表明,杂种小麦的灌浆过程仍可用Logistic方程模拟,其灌浆速率具有明显的优势,但灌浆时间表现不足。 相似文献