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71.
土壤中砷的来源及迁移释放影响因素研究进展 总被引:11,自引:0,他引:11
砷是一种高致癌风险的类金属,自然环境中高砷(As)含量可对人类和生态系统构成直接的健康威胁。研究自然环境中砷的来源、存在形式及影响因素有助于进一步理解环境中砷的迁移转化规律,降低人体摄入砷的风险。对文献的分析表明,铁锰氧化物矿物的还原性溶解、黄铁矿及其他硫化物矿物的氧化溶解、铝氢氧化物表面的砷还原、有机质抑制砷吸附以及Eh降低和pH升高是造成砷向环境迁移的主要原因。本文综述了环境中砷的来源及其向环境迁移的多种影响因素,分析了这些因素与砷之间的作用机制,以期为加强砷污染治理提供科学依据。 相似文献
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Rheological methods are applied whenever flow behavior of substances needs to be investigated on a particle‐to‐particle scale executed by a parallel‐plate rheometer. Under oscillation, mechanical effects due to trafficking or vibrations caused by agricultural and forest machinery can be simulated by conducting amplitude‐sweep tests. Hooke's law of elasticity, Newton's law for ideal fluids (viscosity), Mohr‐Coulomb's equation, and, finally, Bingham's yielding are well‐known relationships and parameters in the field of rheology. This paper aims to introduce rheometry as a suitable method to determine the mechanical behavior of salt‐affected soils when subjected to external stresses. Potassium‐treated loamy sand from Halle and loamy silt from Kassel, both sites located in Germany, as well as loess from Israel, saturated with NaCl solutions in several concentrations were analyzed. From the stress‐strain–relationship parameters like the storage modulus G′ and the loss modulus G″, yield stress τy and the linear viscoelastic (LVE)–deformation range including the deformation limit γL, i.e., the transition from an elastic to a viscous state, were determined and calculated, respectively. With respect to salt effects, amplitude‐sweep tests on originally CaCO3‐rich Avdat Loess show an increasing stability if saturated with higher NaCl concentrations. Comparable tests with K+‐rich substrates from Halle and Kassel evinced similar tendencies including the phenomenon of a critical K+ content, which becomes more obvious in case of the drained (–60h Pa) loamy‐silt samples from Kassel. Nevertheless, a higher microstructural stability is given in both substrates from Halle and Kassel, affected by different water contents, in general, which influence the exchange and availability of cations. The results verify that oscillatory tests are applicable for retracing salt‐induced effects, beside those ones, which are influenced by texture, current water content, and/or further chemical parameters. 相似文献
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白垩病是意大利蜜蜂(Apis mellifera ligustica,简称意蜂)的一种常见真菌性疾病,不同蜂群间的抗白垩病能力强弱差异检测是抗病育种的基础.研究通过实验比较分析意蜂不同蜂群抗白垩病能力的差异.采用DPS软件方差分析系统分组实验统计分析和Tukey法多重比较,对4群患病蜂群和4群健康蜂群自然状态和接种蜜蜂球囊菌病原状态下的3次检测结果分别进行统计分析.结果表明:自然情况下不同蜂群间的抗病能力有差异;1号蜂群在接种蜜蜂球囊菌前、后蜂群患病个体数均显著高于其他蜂群(p<0.05);用白垩病死尸粉末拌入花粉饲喂的方法可以有效诱发蜂群发生白垩病;实验筛选出抗白垩病能力强、弱的蜂群为抗白垩病相关分子标记提供素材. 相似文献
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本文运用山西农村固定跟踪观察户的资料,对农户农地流转行为及影响因素进行研究。研究结果表明:营地户减地行为总体强于增地行为,与此对应,营地户呈现强化包出行为而弱化包入行为的趋势,但现阶段包出力度仍低于包入力度;家庭拥有耕地的规模与零碎度、家庭收入水平、家庭劳动者接受培训的比率、家庭经营非农化程度、家庭人口数量等是影响农户农地流转的主导因素;农户在农地流转中表现出了较高的经济理性,尤其表现在高收入户、高文化户、受培训户和有声望户。 相似文献
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Differences in the behavior of the crossbred steers of different sire lines of Japanese Black cattle
Katsuji UETAKE Toshie ISHIWATA Robert J. KILGOUR Toshio TANAKA 《Animal Science Journal》2012,83(2):184-186
We determined differences in the behavior of the progeny of two major sire lines of Japanese Black cattle by recording the behavior of 35 and 70 half-sib steers of sires from fast (FG) and slow (SG) growing lines, respectively. Two sire lines of steers were mixed and allocated to nine pens with 11–12 animals per pen. The proportion of steers lying was significantly (P < 0.001) higher in the SG line (43.4 ± 5.7% compared to 40.3 ± 6.0%). The proportion of time spent eating concentrate feed (FG: 12.1 ± 2.3%; SG: 11.4 ± 2.1%), drinking (FG: 0.8 ± 1.1%; SG: 0.4 ± 0.6%), licking the feed trough (FG: 0.4 ± 0.6%; SG: 0.2 ± 0.4%) and performing tongue-playing (FG: 3.1 ± 4.6%; SG: 1.0 ± 1.9%) was significantly higher in FG, whereas the proportion of time spent resting (FG: 41.5 ± 12.8%; SG: 43.7 ± 10.9%) and performing self-licking (FG: 1.7 ± 1.4%; SG: 2.1 ± 1.3%) was higher in SG (all P < 0.05). These results show progeny of the FG sire engaged in more active behaviors compared to the progeny of the SG sire line. 相似文献