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71.
罗湾水电站引水系统过渡过程研究 总被引:1,自引:1,他引:1
为了对罗湾水电站增容前后的引水系统过渡过程和机组增容改造对引水系统建筑物的影响进行研究,应用水击计算方法中的电算法进行计算,得出了调压室最低、最高涌浪水位,蜗壳处最大压力水头和机组转速最大升高。结果表明,电站增容后引水系统完全能满足有关规范和设计的要求。 相似文献
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Leslie矩阵模型在油松毛虫种群动态分析中的应用研究 总被引:4,自引:0,他引:4
油松毛虫(Dendrolimus tabulaeformis)是我国华北地区油松林的重要害虫之一。其分布面积广、发生频繁、危害严重。有人曾对油松毛虫种群的生物学特性、防治以及种群动态的研究作过有关的报道,本文则通过对油松毛虫的数量变动进行跟踪调查,并用Leslie矩阵模型对其种群动态进行了模拟,这对害虫的测报具有重要的实践意义。一、材料与方法 (一)标准地概况 1984—1986年与1988—1989年我们分别在密云县五座楼场和石墙沟村选择了5块油松纯林作为标准地,概况列在表1中: 相似文献
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75.
重组M蛋白间接ELISA检测猪繁殖与呼吸综合征病毒抗体 总被引:2,自引:0,他引:2
用纯化的猪繁殖与呼吸综合征病毒重组M蛋白作包被抗原,建立了检测猪繁殖与呼吸综合征病毒抗体的间接ELISA方法,并确立了ELISA最佳工作条件:抗原包被浓度为3.5μg/mL,37℃1h加4℃过夜,血清(1:40)和酶标SPA(1:80)分别在37℃温育1h,加底物溶液常温显色5min。经重复性试验、交叉试验、阻断试验等试验结果表明该方法重复性好、特异性强、敏感度高;与美国IDEXX公司试剂盒相比较,特异性和敏感性分别为96.3%和93.5%,无显著性差异。用建立的方法检测临床血清样品168份,总阳性率为39.9%。 相似文献
76.
Issa Ouedraogo Jennie Barron Siza D. Tumbo Frederic C. Kahimba 《Land Degradation \u0026amp; Development》2016,27(3):682-692
Land conversion in sub‐Saharan Africa has profound biophysical, ecological, political and social consequences for human well‐being and ecosystem services. Understanding the process of land cover changes and transitions is essential for good ecosystem management policy that would lead to improved agricultural production, human well‐being and ecosystems health. This study aimed to assess land cover transitions in a typical semi‐arid degraded agro‐ecosystems environment within the Pangani river basin in northern Tanzania. Three Landsat images spanning over 30 years were used to detect random and systematic patterns of land cover transition in a landscape dominated by crop and livestock farming. Results revealed that current land cover transition is driven by a systematic process of change dominated by the following: (i) transition from degraded land to sparse bushland (10·8%); (ii) conversion from sparse bushland to dense bushland in lowland areas (6·0%); (iii) conversion from bushland to forest (4·8%); and (iv) conversion from dense bushland to cropland in the highlands (4·5%). Agricultural lands under water harvesting technology adoption show a high degree of persistence (60–80%) between time slices. This suggests that there is a trend in land‐use change towards vegetation improvement in the catchment with a continuous increase in the adoption of water harvesting technologies for crop and livestock farming. This can be interpreted as a sign of agricultural intensification and vegetation regrowth in the catchment. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
77.
通过对混流式水轮机座环过渡段进行分析,获得了过渡段的最优结构。分析结果用C语言编写了程序,应用此程序可以提高设计精度,优化结构,缩短设计周期。 相似文献
78.
论述了土地利用变化图绘制的一般过程。图例的设计和不同时期土地利用现状图的代数叠加运算是整个编制过程的关键。做图过程中应本着简单实用、形象达意和美观大方的原则进行。分别选取黄河小浪底水利枢纽库周1993和2000年TM遥感影像进行土地利用变化分析,编制出了建库前后的土地利用变化图,计算出了土地覆被变化的转移矩阵并对土地利用变化的结果进行分析。 相似文献
79.
Chris Lalas 《Biological conservation》2003,114(1):67-78
Management plans for threatened or recovering large vertebrate species that are increasing in population size and range focus on the establishment of viable populations within set temporal limits. New Zealand (Hookers) sea lions (Phocarctos hookeri) were declared a threatened species in 1997, and New Zealand legislation requires that threatened species of marine mammals must be managed to reduce human-induced mortality and achieve a non-threatened status within 20 years. The present breeding distribution of P. hookeri is highly localised, with over 95% of total annual pup production located at Auckland Islands and almost all of the remainder at Campbell Island. Breeding elsewhere has been ephemeral or restricted to <10 adult females. The only recorded sustainable breeding at a new location has been at Otago, South Island, New Zealand. This breeding population consisted of a total of four breeding females in 2002 and is derived from one immigrant female that gave birth to her first pup in the 1993/1994 breeding season. The New Zealand Department of Conservation management plan specifies that to achieve a non-threatened status P. hookeri (1) at Otago must increase in the number of breeding females to ?10, and (2) must establish ?two new breeding locations within the 20-year time frame, each with ?10 breeding females. This study 1) projects the population growth trends at a new location (Otago) to see if it will achieve ?10 breeding females within the legislated time frame, and (2) examines the likelihood that other breeding locations will establish elsewhere given the demographic information available for this species. We present 20 deterministic and three stochastic Leslie matrix model scenarios for female population growth for the initial years following the start of breeding at a new location. Our results indicate that (1) a new breeding population derived from one immigrant female is unlikely to reach 10 breeding females in 20 years; this duration is more likely to be 23-41 years (deterministic models) or 23-26 years (stochastic model), (2) the likelihood of two new sites establishing within 20 years is unquantifiable, but the probability is low, and (3) if the legislated outcome and time limit are not revised in the population management plan, the feasibility and effectiveness of re-locating young females could be investigated. 相似文献
80.
采用 Sr-Ni-Al-Mg 混合液为基体改进剂,研究了塞曼石墨炉原子吸收法直接测定硼的方法.试验表明,使用本混合基体改进剂,抗干扰能力强,大大挺高硼的吸收信号,线性范围较宽(0.2~10μg/mLB),并且在线性范围内彻底消除了硼的记忆效应.方法的特征量为100pg/0.0044A·S. 相似文献