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41.
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要使我国的经济实现三步走的战略目标 ,必须从国家创新系统的角度提出并规划我国的经济科技体制改革和发展战略。为此 ,对国家创新系统的基本概念、特点、构成、起源进行了论述 ,并对国家创新系统中政策工具的选择进行了分析 相似文献
43.
组合机床的计算机辅助总体设计 总被引:1,自引:0,他引:1
以单面,钻孔类的组合机床为对象,提出了用于组合机床总体设计的CAD模块的设计方法,以汉化AutoCAD为绘图软件,以TuroboC2.0为设计计算语言,开发了通用微机件的选型模块及图形处理模块。依据参数化设计的基本原理,采用编制参数程序的工作模式,建立了组合机床通用件图形程序库。 相似文献
44.
J.B. Million J.T. Ritchie T.H. Yeager C.A. Larsen C.D. Warner J.P. Albano 《Scientia Horticulturae》2011
Container Crop Resource Optimization Program (CCROP) is an integrative model which simulates the growth and water and nutrient requirements of a woody ornamental shrub grown in small (2.8–11.4 L) containers in a field environment with overhead sprinkler irrigation. The model was developed for producers, producer advisers and researchers to support best management practice decision-making in container nursery production. We describe the primary processes simulated by CCROP particularly how they differ from traditional crops grown in-ground and assess the ability of CCROP to simulate measured values for a range of irrigation and fertilizer trials and transplanting dates. Results of model testing with 11 trials indicate that CCROP provided reasonable outcomes for biomass and leaf area growth as well as evapotranspiration, runoff (container drainage plus un-intercepted irrigation and rainfall) and nitrogen loss. 相似文献
45.
刀具的涂层与深冷处理都是当今世界上流行的刀具强化与处理的新,经上述处理后的刀具既具有硬度高。耐磨性好,又能保持较好韧性等特点,但两者又有诸多不同之处。本文是作者在实验研究基础上,针对这二种处理的刀具各自的特点进行了分析对比,便于在生产上能合理的推广使用。 相似文献
46.
Iron (Fe) toxicity is a major stress to rice in many lowland environments worldwide. Due to excessive uptake of Fe2+ by the roots and its acropetal translocation into the leaves, toxic oxygen radicals may form and damage cell structural components, thus impairing physiological processes. The typical visual symptom is the “bronzing” of the rice leaves, leading to substantial yield losses, particularly when toxicity occurs during early vegetative growth stages. The problem is best addressed through genotype improvement, i.e., tolerant cultivars. However, the time of occurrence and the severity of symptoms and yield responses vary widely among soil types, years, seasons, and genotypes. Cultivars resistant in one system may fail when transferred to another. Better targeting of varietal improvement requires selection tools improving our understanding of the resistance mechanisms and strategies of rice in the presence of excess iron. A phytotron study was conducted to develop a screen for seedling resistance to Fe toxicity based on individual plants subjected to varying levels of Fe (0–3000 mg L–1 Fe supplied as Fe(II)SO4), stress duration (1–5 d of exposure), vapor‐pressure deficit (VPD; 1.1 and 1.8 kPa), and seedling age (14 and 28 d). Genotypes were evaluated based on leaf‐bronzing score and tissue Fe concentrations. A clear segregation of the genotypic tolerance spectrum was obtained when scoring 28 d old seedlings after 3 d of exposure to 2000 mg L–1 Fe in a high‐VPD environment. In most cases, leaf‐bronzing scores were highly correlated with tissue Fe concentration (visual differentiation in includer and excluder types). The combination of these two parameters also identified genotypes tolerating high levels of Fe in the tissue while showing only few leaf symptoms (tolerant includers). The screen allows selecting genotypes with low leaf‐bronzing score as resistant to Fe toxicity, and additional analyses of the tissue Fe concentration of those can identify the general adaptation strategy to be utilized in breeding programs. 相似文献
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《Wood material science & engineering》2013,8(4):217-224
Abstract Considering ongoing global deforestation and the increased demand for raw materials in all wood-processing sectors it is necessary to seek and employ alternative resources. Agricultural residues are potential sources of alternative lignocellulose-based raw materials. Research on substitute materials for wood panel production mainly focused on physical and mechanical properties of boards while much remains to be learned about machining. Therefore, studies were carried out to analyse the relationship between ash and silica content and their impact on tool wear. Ash and silica contents of agricultural residues were determined following ISO 3340. Particle morphology and elemental composition of selected materials were analysed using scanning electron microscopy and energy-dispersive X-ray analysis. Tool wear tests were carried out using particleboards made from wheat straw, canola straw and spruce. Analyses of various plant materials displayed no correlation between ash and silica content. Bio-mineralised silica structures in wheat and canola were different compared to coarse silica found in wood-based particleboard. Tool wear caused by these agricultural residues was just moderately increased compared to wood, despite the fact that their silica contents were many times higher. Furthermore, the impact of abrasive substances on wear behaviour was influenced by the density of the panels. 相似文献
50.
关于多媒体课件制作的探讨 总被引:4,自引:0,他引:4
张艳慧 《河北北方学院学报(自然科学版)》2005,21(3):28-30
计算机辅助教学的推广和普及,少不了多媒体课件的支持.教师要想制作出优秀的课件,首先应该合理选择或学习一种课件制作工具,其次应该把握好课件制作的各个环节,使所制作的课件符合教学规律,从而充分发挥现代化教育教学手段的优势,使教学效果达到最优化. 相似文献