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981.
拟定和建立土壤侵蚀的雨量标准,旨在区分发生和不发生土壤侵蚀的降雨事件,从而可以减少计算降雨侵蚀力的工作量,进而在此环节上,为提高土壤侵蚀预报精度提供可能和条件。选取位于皖南山区的歙县华源河流域内所设置的3个径流小区的实测资料为分析样本,以此推求出其侵蚀性降雨雨量标准依次为13.6、14.6和14.77mm。按此标准,可剔除降雨场次50%以上,而漏选的土壤流失量占总侵蚀量的比例在3%以内。 相似文献
982.
西气东输工程沿线陕西段区域生态安全格局设计研究 总被引:9,自引:2,他引:9
区域生态安全格局是一个新近提出的概念,其理论尚在发展之中。研究以西气东输工程陕西段为例,从保证管道安全和解决工程中的生态问题入手,提出了管道工程沿线区域生态安全格局的设计框架,对生态安全格局理论进行了初步的应用。制图分析得出陕西段主要生态系统有丘陵黄绵土农田生态系统、丘陵黄绵土丛生禾草草原生态系统、平原黄绵土农田生态系统、沙地生态系统等。水土流失敏感性分析显示3个标段均有超过80%区域属敏感区,水土流失很严重。生态系统中关键生态单元主要有6处,包括丘陵沟壑区梁峁穿越,腰岘穿越,中小冲沟穿越,河流凹岸(陡崖)穿越,大开挖河流,固定、半固定沙丘穿越。在生态系统功能分析的基础上进行了区域基本生态安全格局设计,并针对关键生态单元进行了关键生态安全格局设计。 相似文献
983.
Mao Li Xuejuan Zi Hanlin Zhou Renlong Lv Jun Tang Yimin Cai 《Animal Science Journal》2021,92(1):e13635
This study investigated the effects of LAB inoculants (L) and molasses (M) on the microbial community and fermentation quality of cassava foliage (CF). The small segments (about 2–3 cm) CF were ensiled in plastic bags and incubated at normal temperature (25°C). Four treatments were carried out as follows: control (no additives, CK), LAB inoculants (Lactobacillus plantarum, L), molasses (M), and LAB in combination with molasses (LM). The LAB and molasses obviously altered the bacterial community structure of the CF silage and enhanced the fermentation quality. The combination addition could increase the abundance of Lactobacillus and reduce the Pseudomonas. The LAB and molasses also significantly elevated the lactic acid concentration (P < 0.001) and decreased the pH (P < 0.001), as well as the concentrations of acetic acid, propionic acid, butyric acid, and ammonia-N (P < 0.05). In addition, the combination treatment displayed more effective results on silage fermentation. The LAB and molasses improved the fermentation quality of the CF silage by altering the bacterial community structure. Furthermore, the bacterial community was significantly correlated with fermentation indexes. 相似文献
984.
Xiaobo Yang Donghai Li Kim McGrouther Wenxing Long Yuelie Li Yukai Chen Xiaobo Lv Nabeel Khan Niazi Zhaoliang Song Hailong Wang 《Journal of Soils and Sediments》2017,17(9):2383-2389
Purpose
Eucalyptus forest plantations are normally devoid of understory vegetation that is often assumed to be associated with Eucalyptus allelopathic effects. The objective of this study was to determine the influence of high soil compaction and low soil moisture content on inhibition of the germination of understory seeds in Eucalyptus forests and thus would result in the scarcity of understory vegetation.Materials and methods
The soil water content above the depth of 1 m of six major understory vegetation types was analyzed to determine if there was a correlation between soil water content and understory vegetation. The effects of soil treatment (soil-loosening vs. no soil-loosening) and water supply amount (2500, 2000, 1500, 1000, 500, 250, or 0 ml of water per day) on the seed germination rate of Stylosanthes sp. were explored using an artificial climate chamber experiment. Influence of soil source (five Eucalyptus forest soils vs. two non-Eucalyptus forest soils) and water supply (0, 50, 150, 200, or 400 ml of water every day) on the germination rate of five types of seed were assessed using a three-factor analysis of variance (ANOVA).Results and discussion
Soil-loosening and water supply significantly (P?<?0.05) increased seed germination rate with the contribution rates of 26.14 and 42.93 %, respectively. Analysis of variance for three-factor experiments revealed a significant (P?<?0.05) effect of water supply and vegetation seed type on the germination rate of plant seeds. No significant effect of soil type was observed on germination rate, indicating that germination rate was not affected by soils in Eucalyptus forest.Conclusions
The conservation of soil characteristics, such as water content and compaction, during the development of a Eucalyptus forest plantation may be an effective strategy for encouraging the growth of understory vegetation. This study highlights the importance that in dry areas or areas prone to long-term drought, it would be preferable to retain native vegetation.985.
986.
为快速、准确地检测土壤中氯离子的含量,采用以水作为提取剂,水土比1:10(v/w),超声处理30min提取的方法,结合以氢氧化钾溶液为淋洗液,阴离子交换柱分离,电导检测器检测的离子色谱检测手段。结果表明,该方法能够达到快速、准确地检测土壤中氯离子含量的目的,该方法精密度及准确度实验结果表明其适用于各类型土壤中氯离子含量的测定。 相似文献
987.
化学是一门以实验为基础的学科。针对目前中职化学实验教学的状况,结合新课改提出了化学实验教学的新措施,从课堂演示实验、实验室动手实验及课后家庭实验3方面,阐述了提高化学实验的教学水平的途径和方法。 相似文献
988.
建立了一种操作简单、快速定性检测粒状口香糖和巧克力豆中的巴西棕榈蜡高温气相色谱分析法,标样溶液直接用三甲基硅烷(BSTFA)衍生,样品经超声加热充分提取后用BSTFA衍生,用氢火焰离子检测器(FID)直接检测,在检测的3种口香糖样品和2种巧克力豆样品中,均检测出巴西棕榈蜡相关成分,并对样品中的巴西棕榈蜡含量进行了粗略估算。 相似文献
989.
基于多种混合振动信号传递中各组成信号的频率保持特性,建立了风轮典型振型动态频率的间接测试和识别方法,并利用试验测试与数值仿真相结合的方法佐证了该方法的可靠性。具体方法是在电机前端部靠近风轮处布置加速度传感器捕获沿风轮轴向的加速度时域信号,通过快速傅里叶变换(fast fourier transformation,FFT)获得被测信号的频域特征,进而结合风轮模态振型及频谱特征识别其典型振型动态频率值。经与数值仿真结果比较,测试相对误差控制在5%以内,精度较好。同时,由于该方法无需在叶片表面大量布装传感器,故具有在不破坏叶片表面原有形态,完整保留风轮流场和结构场特征的前提下简捷获取风轮典型振型动频值的测试优势,有效解决了现今风轮典型振型在运行工况时动态频率值监测难、识别难的技术困境,同时可为风轮健康监测提供参考。 相似文献
990.