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151.
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为探讨不同类型日粮和粗料对奶牛泌乳性能的影响,本试验选用12头健康荷斯坦牛为试验动物,随机分为3组,试验分两期进行.在精料相同条件下,第一期分别选用精粗比为40∶60的秸秆型A日粮(粗料仅为干玉米秸秆)、40∶60的青贮型B日粮和60∶40的青贮型C日粮(B、C日粮粗料仅为玉米秸秆青贮)为不同类型试验日粮进行试验;第二期粗料分别以干玉米秸秆(a日粮)、青苜蓿干草(b日粮)、干玉米秸秆和青苜蓿干草混合(50∶50,c日粮)为不同粗料类型试验日粮,进行奶牛饲喂试验.第一期试验结果表明:青贮玉米代替玉米秸秆或适当增加日粮中精料比例可显著提高奶牛的产奶性能,但乳脂率有降低的趋势.第二期试验结果表明:精料相同条件下,苜蓿青干草代替干玉米秸秆有助于提高产奶量和乳蛋白率,但是会显著降低乳脂率.玉米秸秆与苜蓿混合饲喂和单一饲喂玉米秸秆相比,产奶量与乳蛋白率均有所提高,但乳脂率显著降低;和单一饲喂苜蓿相比,虽然乳糖率略有提高,但产奶量和乳蛋白率明显减少,乳脂率也显著降低. 相似文献
153.
精密排种器的研发现状 总被引:1,自引:0,他引:1
播种质量的优劣是农业增产的前提,而排种器直接决定播种机工作质量和性能优劣。全面阐述排种器的种类及国内外发展现状,提出今后需要解决的问题,探讨排种器的研发方向。 相似文献
154.
Viperin是一种细胞内抗病毒蛋白,可以被I型干扰素、多聚I:C、脂多糖及多种病毒诱导表达,在细胞内主要定位在内质网和脂滴,具有广谱的抗病毒功能。为研究马Viperin(eViperin)在抗病毒感染中的作用,本研究应用RT-PCR从马巨噬细胞中扩增eViperin基因,并将其克隆于真核表达载体pDC315中构建重组质粒pDC-eViperin-Flag,将重组质粒转染293T细胞,western blot检测结果表明eViperin在293T细胞中正确表达。将该重组表达质粒与表达马传染性贫血病毒(EIAV)Gag前体蛋白(Gag precursor,Pr55gag)的表达质粒共转染293T细胞,转染48 h后western blot检测,结果显示实验组细胞培养上清中的Pr55gag含量显著低于空白对照组,表明eViperin具有抑制EIAV释放的作用。此外,将该重组表达质粒与腺病毒骨架质粒pBHGlox△E1,E3Cre共转染HEK293细胞,进一步构建拯救出表达eViperin的重组腺病毒,为研究eViperin的抗病毒功能研究奠定了基础。 相似文献
155.
土壤水分对植物根-土界面相互作用特性的影响 总被引:5,自引:2,他引:3
为研究不同土壤水分下不同植物根系与土壤界面的摩阻特性,使用直剪仪对内蒙古中西部的5种典型乡土植物(柠条、沙棘、杨柴、紫花苜蓿和沙打旺)的根系在不同土壤含水率下进行根-土界面直剪摩擦试验。结果表明:当土壤含水率在4.5%~24.5%时,5种植物根-土界面摩擦系数均大于素土的土-土界面的值,且随着土壤含水率的增加,根-土界面和土-土界面摩擦系数均呈下降趋势,其中沙棘根-土界面的摩擦系数和黏聚力均大于其他4种植物的值,表明仅从根系与土壤间的相互作用特性来看,沙棘根系固土抗蚀的作用明显优于其他4种植物。根-土界面和土-土界面黏聚力均随着土壤含水率的增加呈先增后减的变化特征,且植物种不同黏聚力峰值出现时对应的土壤含水率亦不同。 相似文献
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158.
Farias JG Bustos-Obregón E Tapia PJ Gutierrez E Zepeda A Juantok C Cruz G Soto G Benites J Reyes JG 《The Journal of reproduction and development》2008,54(1):18-21
Chronic hypobaric hypoxia (CHH) induces a decrease in sperm output and spermatogenesis in male rats. The mechanisms that underlie these changes in testicular function are unknown and could involve changes in the hypophysis-gonad axis. We have tested the hypothesis that changes take place in the endocrine status (FSH, follicle stimulating hormone; LH, luteinizing hormone; testosterone) of rats subjected to CHH. Male Wistar rats were maintained under normobaric or hypobaric conditions (428 torr, 4,600 m). On days 0, 5, 15 and 30 post-exposure, 12 rats were anesthetized, their body weights were measured and blood samples were collected. The testicles were fixed in 4% formaldehyde and processed for histological analysis. In this time course, the FSH levels rose by day 5 post-exposure. On subsequent days, the FSH levels decreased in rats subjected to CHH with a tendency to remain higher than the normoxic group. The LH plasma levels decreased in rats exposed to CHH. Consistent with the decrease in LH levels, the plasma testosterone level decreased significantly after 30 days of CHH exposure. Integrated analysis of hormonal changes in rats subjected to CHH and the body dehydration that occurs in HH allows us to conclude that the effects of CHH on spermatogenesis may be partially related to changes in the hypophysis-gonad hormonal axis. 相似文献
159.
Lifschitz A Nava S Guglielmone AA Imperiale F Farias C Mangold AJ Lanusse C 《Veterinary parasitology》2008,156(3-4):284-292
The therapeutic efficacies of ivermectin (subcutaneous injection) and eprinomectin (topical treatment) given at two different dosage levels to goats naturally infested with Amblyomma parvum were assessed. Treatments included subcutaneous injection of ivermectin at 0.2 and 0.4mg/kg and extra-label pour-on administration of eprinomectin at 0.5 and 1mg/kgb.w. Ivermectin and eprinomectin failed to control Amblyomma parvum on goats. Treatment with ivermectin resulted in a low number of engorged female ticks in relation to untreated control goats and, at the highest dose rate (0.4mg/kg), the female engorgement weights were significantly lower and the pre-oviposition period significantly longer than those observed in ticks recovered from untreated control goats. The tick efficacy assessment was complemented in a separate group of tick-free goats with a pharmacokinetic characterization of eprinomectin (topically administered at 0.5, 1.0 and 1.5mg/kg) and ivermectin (subcutaneous treatment given at (0.2 and 0.4mg/kg) in goats. Heparinized blood samples were taken between 0 and 21 days post-treatment. Higher and more persistent drug plasma concentrations were recovered after the subcutaneous treatment with ivermectin compared to those obtained for eprinomectin topically administered. The understanding of the relationship among the pattern of drug absorption, the kinetic disposition and the resultant clinical efficacy is relevant to improve the poor performance observed for ivermectin and eprinomectin against A. parvum on goats. 相似文献
160.