首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   120篇
  免费   23篇
  国内免费   6篇
林业   1篇
农学   1篇
综合类   24篇
农作物   6篇
水产渔业   12篇
畜牧兽医   92篇
园艺   4篇
植物保护   9篇
  2022年   1篇
  2021年   3篇
  2020年   11篇
  2019年   6篇
  2018年   6篇
  2017年   8篇
  2016年   10篇
  2015年   12篇
  2014年   8篇
  2013年   7篇
  2012年   10篇
  2011年   8篇
  2010年   8篇
  2009年   6篇
  2008年   4篇
  2007年   3篇
  2006年   5篇
  2005年   4篇
  2004年   3篇
  2003年   1篇
  2002年   1篇
  2001年   3篇
  2000年   5篇
  1999年   5篇
  1997年   1篇
  1996年   1篇
  1994年   2篇
  1993年   2篇
  1986年   1篇
  1984年   1篇
  1982年   1篇
  1981年   2篇
排序方式: 共有149条查询结果,搜索用时 62 毫秒
101.
脊椎畸形综合征(Complex Vertebral Malformation,CVM)是由常染色体上SLC35A3基因单碱基突变(G→T)引起的隐性遗传疾病,该基因隐性纯合(CV/CV)时奶牛致死,但CVM携带者表现正常,所以CVM携带者公牛可以通过人工授精技术传播CVM缺陷基因。本研究利用PCR-SSCP方法对北京地区242头公牛样品和403头母牛样品进行了检测分析,研究结果表明,在所检测的样本中,荷斯坦种公牛和母牛CVM携带率分别为8.82%和5.71%,CVM基因频率分别为4.41%和2.85%。通过系谱追踪发现,CVM遗传缺陷的共同祖先是美国名牛"Penstate Ivanhoe Star"(USA.1441440,CV)。通过剔除CVM携带者公牛可以有效地控制CVM遗传缺陷的传播,但是,我国许多CVM携带者公牛冻精依然在商业化使用,所以有效地监控CVM携带者在奶牛群中的状况对CVM防控计划是有益的。  相似文献   
102.
The general skull morphology of the head of the Cavalier King Charles Spaniel (CKCS) was examined and compared with cephalometric indices of brachycephalic, mesaticephalic, and dolichocephalic heads. Measurements were taken from computed tomography images. Defined landmarks for linear measurements of were identified using three‐dimensional (3D) models. The calculated parameters of the CKCS were different from all parameters of mesaticephalic dogs but were the same as parameters from brachycephalic dogs. However, the CKCS had a wider braincase in relation to length than in other brachycephalic breeds. Studies of the etiology of the chiari‐like malformation in the CKCS should therefore focus on brachycephalic control groups. As Chari‐like malformation has only been reported in brachycephalic breeds, its etiology could be associated with a higher grade of brachycephaly, meaning a shorter longitudinal extension of the skull. This has been suggested for other breeds.  相似文献   
103.
利用微核、精子畸变和Ames试验检测了转Bt基因水稻稻米对小鼠骨髓嗜多染红细胞(polychromatic erythrocytes,PCE)微核率(micronucleus frequency,MN%)和小鼠精子畸形发生率(sperm malformation rate)及组氨酸营养缺陷型鼠伤寒沙门氏菌株回变菌落数的影响。结果表明,在本实验条件下,Bt水稻稻米对小鼠体细胞和性细胞均无诱变活性,且无剂量效应;该受试物对TA97a、TA98、TA100和TA102菌株无论在有无代谢活化系统存在的条件下,各剂量组回变菌落数均处于正常水平。  相似文献   
104.
Background: Polymicrogyria is a disorder of cerebrocortical migration resulting in increased numbers of small, disorganized gyri. This disorder occurs in Standard Poodles and in cattle.
Objectives: To describe the clinical, electroencephalographic, imaging, and histopathologic features in poodles with polymicrogyria.
Animals: Five Standard Poodles with histologically confirmed polymicrogyria.
Methods: Retrospective case series. Cases were obtained by personal communication with 1 of 2 authors (TJVW, DPO).
Results: All dogs had cortical blindness and other neurologic abnormalities including gait and behavioral changes. Magnetic resonance imaging of 3 dogs showed multiple disorganized gyri, which were especially apparent on T2-weighted dorsal plane images. Electroencephalogram (EEG) of 1 dog revealed epileptiform discharges, including both spike and spike and wave discharges with voltage maximum potentials over the parietal/occipital region. The EEG supported that the repetitive behavior displayed by the dog was a complex partial motor seizure. One dog had concurrent hydrocephalus. All dogs had occipital lobe involvement and 2 dogs had involvement of other lobes.
Clinical Importance: The cases presented here demonstrate a larger age range (7 weeks to 5 years) and a decreased frequency of associated hydrocephalus when compared with the previous report.  相似文献   
105.
根据有害生物风险评价方法,从芒果畸形病国内外分布状况、潜在危害性、受害栽培寄主的经济重要性、传入与定殖的可能性和风险管理难度等方面进行了综合分析评估,其综合风险值R为2.3,属于高度危险性有害生物,并根据风险分析的结果提出了防止其传入我国的管理措施。  相似文献   
106.
A previous study elucidated that an extreme hypoxia during somitogenesis induced the most frequent skeletal malformation centrum defects in red sea bream (RSB), Pagrus major. In this study, details of the hypoxic conditions to induce them in RSB, dissolved oxygen (DO) concentration and exposure time to hypoxia, were investigated. Fertilized eggs were exposed to seawater of six DO concentrations (0%, 10%, 25%, 50%, 75% and 100% of saturation) for seven different periods (5, 10, 30, 60, 120, 240 and 360 min) during somitogenesis. Somitic disturbances in newly hatched larvae were induced by exposure to 0% and 10% DO concentration for 10 and 120 min and longer respectively. Rearing eggs exposed to hypoxic condition of 10% DO for 240 min for 40 days post‐hatch showed that the location and the frequency of somitic disturbances in larvae and centrum defects in juveniles were significantly correlated (P<0.01). Dissolved oxygen concentration of the interstitial water in the egg high density layer formed at the water surface in a stationary state abruptly decreased to 3.7% within 7 min. Centrum defect induction by exposure of eggs to extreme low DO concentrations for a short period, which is the probable situation in the practical juvenile production, suggests that careful maintenance of DO concentration is important in the incubating water of fertilized eggs during egg sorting and transportation, where eggs are made into a pile and undergo hypoxia, for the prevention of centrum defects.  相似文献   
107.
108.
2012年10月2日,华南师范大学穿山甲人工驯养与繁育研究基地一头圈养条件下受孕的马来穿山甲产出一例畸形仔兽,产出时仔兽已没有生命体征,体重90 g,体长24.1 cm,雄性;幼仔头部多个器官畸形:隐眼,外耳发育不全,双侧唇腭裂,额顶部右侧有明显的凸起,身体其他部分发育正常;已制成标本保存于华南师范大学生命科学学院。认为此仔兽畸形可能与母兽的营养改变、疾病或药物使用等因素有关。本案例对今后妊娠期的穿山甲母兽饲养管理、疾病治疗以及保育工作有一定的启示和指导作用。  相似文献   
109.
Malformation is a destructive disease of mango, Mangifera indica . Its causal agent possesses the morphological features of Fusarium subglutinans , a species whose taxonomy and nomenclature has recently been in a state of flux. Genetic diversity was examined among 74 F. subglutinans -like isolates from malformed mango in Brazil, Egypt, Florida (USA), India, Israel and South Africa. With nitrate-nonutilizing ( nit ) auxotrophic mutants, seven vegetative compatibility groups (VCGs) were identified. Three of the VCGs were found in a single country, and VCG diversity was greatest in Egypt and the USA where, respectively, four and three different VCGs were found. RAPD profiles generated with arbitrary decamer primers were variable among isolates in different VCGs, but were generally uniform for isolates within a VCG. In PCR assays, a 20-mer primer pair that was developed previously to identify F. subglutinans from maize (mating population [MP]-E of the Gibberella fujikuroi complex) also amplified a specific 448 bp fragment for isolates of F. sacchari from sugarcane (MP-B) and what was probably F. circinatum (pine, MP-H). With the exception of three isolates from Brazil, it did not amplify the fragment from F. subglutinans -like isolates from mango. A second pair of 20-mer primers was developed from a unique fragment in the RAPD assays. It amplified a specific 608 bp fragment for 51 of 54 isolates from mango (all but the three Brazilian isolates). It also amplified a smaller, 550 bp fragment from isolates of F. nygamai (MP-G), but did not amplify DNA of isolates of any other taxon of Fusarium that was tested.  相似文献   
110.
Syringobulbia is a pathologic condition characterized by one or more fluid‐filled cavities within the brainstem. This retrospective case series describes observations in eight dogs with syringobulbia diagnosed during MRI. All dogs were adult, small‐breed dogs with concurrent syringomyelia and neurologic deficits localized to sites rostral to the spinal cord, which cannot be explained by syringomyelia (eg, six dogs had vestibular signs). On MRI, the fluid‐filled cavities had signal intensity characteristics like cerebrospinal fluid, were in the medulla oblongata, and were solitary in each dog. Initially, the shape of the cavity was a slit in five dogs and bulbous in two dogs. Magnetic resonance imaging was repeated in five dogs (6‐55 months of age). One dog had progression of syringobulbia from slit‐like to bulbous, and four dogs had unchanged slit‐like syringobulbia. One dog developed slit‐like syringobulbia after cranioplasty. A variety of medical and surgical treatments were performed with improvement of some but not all clinical signs. One dog died following surgery due to cardiopulmonary failure and the other seven dogs were alive at least 1 year after the initial diagnosis, which was the least time of follow‐up. One surviving dog developed a unilateral hypoglossal nerve deficit 2 months after the initial diagnosis and megaesophagus 14 months later. In conclusion, detecting a fluid‐filled cavity in the medulla oblongata consistent with syringobulbia is possible in dogs undergoing MRI. The cavity is likely acquired, slit‐like or bulbous, progressive, or static, and might be associated with breed size and neurologic signs localized to the medulla oblongata.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号