四轮驱动拖拉机在松软坡地上的阻力分析

对四轮驱动拖拉机在松软坡地上的滚动阻力作了理论分析。在不同牵引负荷下，对装备不同型号、不同充气压力轮胎的拖拉机在松软坡地上的滚动阻力进行了试验研究。给出了野外试验结果并对其进行了分析讨论。     

Cloning and molecular evolution research of porcine GAD65 gene

Glutamate decarboxylase (GAD) has been found in animal and higher plant tissues as well as in yeasts and microorganisms. In animals the enzyme plays an important role in central nervous system activity because the enzyme substrate glutamic acid is a mediator of excitation process and the product, gamma-aminobutyric acid, is the most important mediator of inhibition process in the central nervous system. GAD65 is one form of the glutamate decarboxylases (GAD), GAD65 has been identified as a major autoantigen in type 1 diabetes, so the GAD65 gene of porcine was cloned by RT-PCR method to construct phylogenetic tree, the homology of 13 glutamate decarboxylases (GAD) of different origin was analyzed by multiple alignment.     

应用回交转育法选育纤维用亚麻不育系

回交转育是选育雄性不育系最快最有效的方法。本试验选用生产上大面积推广的综合性状优良的纤维用亚麻品种做轮回亲本，对油用雄性核不育系材料进行回交转育，经过三次回交和两次不育株与可育株杂交，成功培育出4个综合性状优良的纤雏用亚麻雄性核不育系。     

直刃斜装滚刀式切碎器的优化设计

切碎器是切碎机的主要工作部件，其设计与使用得好坏，对切碎机的工作性能影响极大.本文研究了直刃斜装滚刀式切碎器切碎饲草所需功率，提出了一种功耗最低的优化方法，能够选择合理的参数．以达到较好的切碎性能．     

Rolling behaviour of sows in relation to piglet crushing on sloped versus level floor pens

The study focused on the rolling behaviour of sows and the crushing of piglets by sows' rolling behaviour. The experiment examined the influence of sloped floor in loose housed farrowing pens on the rolling behaviour of sows and crushing of piglets. The experimental unit was made up of 24 pens. There were two experimental pen designs with piglet creep in the corner of the pen and piglet creep across the end of the pen, respectively. Both of the experimental pen designs had a 10% sloped floor in the sow's resting area. The two control pen designs were identical to the experimental pen designs, but with a level floor. The behaviour of 85 sows and their litters was continuously video recorded. Behavioural observations were made from birth of the first piglet and until 3 days after birth of the first piglet. Rolling behaviour of sows caused significantly more trapped piglets under the sow than lying down from standing (P = 0.04). Rolling behaviour caused 64% of the trapped piglets and lying down from standing caused 36% of the trapped piglets. Rolling from udder to side without protection trapped significantly more piglets than rolling from udder to side near slanted wall or piglet protection rails and rolling from side to udder (P < 0.001). With a certain pen design sloped floor reduced rolling from udder to side without protection (P = 0.007) and reduced the number of trapped piglets (P = 0.01), but results concerning lying behaviour showed that sloped floor pushed sows to rest on the level part of the floor. The results indicate that rolling behaviour that crushes piglets can be reduced, and sows prefer to lie on a level floor.     

甘蓝型双低油菜细胞质雄性不育系宁A7的选育研究Ⅰ.MICMS双低不育系宁A7的回交选育

以农艺性状优良、配合力高、具部分恢复基因的品系为轮回亲本 ,与MICMS双低不育系“宁A6”回交 ,定向选育具有轮回亲本优良性状和原不育系不育性的新不育系 ,经 3个轮回世代的回交、自交和测交 ,育成MICMS胞质不育系“宁A7”和保持系“宁B7”。宁A7不育系株型紧凑 ,不育性彻底 ,双低品质稳定 ,经济性状得到进一步改良。     

毛白杨杂交育种战略的研究

本文从毛白杨的特性及较难育种的背景出发,对如何开展毛白杨杂交育种的战略,进行了探讨。作者改用毛白杨杂种作母本、应用双杂交和回交的育种方式,伴以花粉和种子辐射等技术措施,获得大量杂种苗木,从中选出不少有希望的速生无性系。     

农业机械对土壤压实的试验研究

对农业机械在砂壤土上进行了碾压次数、碾压载荷与土壤主要物理机械性能参数的试验研究。结果表明:在0～10 cm处,少次碾压对土壤容重、坚实度的影响比较大,多次碾压对其影响小;含水量的损失量随碾压次数的增多而减小;容重、含水量的损失量和坚实度都随碾压载荷的增大而增大,6911拖拉机使含水量最大减小了13.7%,收割机使其最大减小了20%;载荷小的机械碾压对土壤表土层(10 cm以内)的坚实度的影响大,载荷大的对土壤深层的坚实度影响要大些。     

鲤鲫杂交(♀)×鲫(♂)回交子代的形态特征研究

利用雌性鲤鲫杂交与雄性鲫鱼回交,制备了鲤鲫杂交回交子代鱼,并对其1龄鱼的形态特征和内部器官结构进行了测定。其主要性状为：回交子代的背鳍条Ⅲ,15～18；臀鳍条Ⅲ,4～6；侧线鳞27～36；侧线上鳞和侧线下鳞同为5～6；鳃耙28～33；体长为体高的(2.35±0.11)倍,为头长的(3.33±0.13)倍,为尾柄长的(6.36±0.54)倍；头长为眼径的(4.54±0.20)倍；为眼间距的(1.74±0.07)倍；为尾柄高的(1.96±0.10)倍；尾柄长为尾柄高的(0.90±0.28)倍；体高为头高的(1.59±0.09)倍。结果表明,该回交子代鱼在可数和可量性状上都有个别性状产生变易,但大多数性状相对比较稳定。