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   151篇
  免费   20篇
  国内免费   1篇
综合类   23篇
水产渔业   2篇
畜牧兽医   145篇
植物保护   2篇
  2020年   4篇
  2019年   4篇
  2018年   4篇
  2017年   3篇
  2016年   6篇
  2015年   3篇
  2014年   3篇
  2013年   14篇
  2012年   1篇
  2011年   5篇
  2010年   4篇
  2009年   10篇
  2008年   6篇
  2007年   5篇
  2006年   2篇
  2005年   3篇
  2003年   6篇
  2002年   4篇
  2001年   2篇
  2000年   2篇
  1999年   2篇
  1998年   5篇
  1997年   2篇
  1995年   5篇
  1992年   2篇
  1991年   3篇
  1990年   4篇
  1989年   2篇
  1988年   6篇
  1987年   3篇
  1986年   6篇
  1985年   10篇
  1984年   7篇
  1983年   1篇
  1982年   3篇
  1981年   3篇
  1980年   3篇
  1973年   1篇
  1925年   2篇
  1924年   2篇
  1921年   1篇
  1918年   1篇
  1916年   3篇
  1910年   1篇
  1902年   1篇
  1900年   1篇
  1893年   1篇
排序方式: 共有172条查询结果,搜索用时 31 毫秒
1.
2.
Plasma concentrations of PAG‐1 are used for pregnancy diagnosis and as a marker of placental/foetal well‐being, while those of PAG‐2 may be an indicator of abortion risk in Neospora caninum‐infected cows. Studies have shown that N. caninum infection modifies PAG‐1 and PAG‐2 patterns in maternal blood plasma. However, no prior work has examined the effects of N. caninum infection on concentrations of PAGs in foetal fluids. In this study, PAG‐1, PAG‐2 and pH levels were determined in the amniotic and allantoic fluids of foetuses collected at 152 days of gestation from control uninfected dams and from dams experimentally infected with N. caninum on Day 110 of gestation. Foetal fluids from infected foetuses had significantly higher PAG‐2 concentrations (p = 0.026) and pH values (p = 0.02) than fluids from non‐infected foetuses. In infected foetuses, significantly higher concentrations of PAG‐1 (p < 0.001) and PAG‐2 (p < 0.001) were detected in fluid samples showing antibodies against N. caninum than those without antibodies. Moreover, pH values were significantly higher (p = 0.011) in foetal fluid samples with antibodies than in samples from non‐infected foetuses. In conclusion, this is the first report on the effect of N. caninum infection on PAG levels in foetal fluids. Our results indicate that following the experimental infection of dams with N. caninum on Day 110 of gestation, foetal fluids collected from the infected foetuses of these dams featured higher PAG‐1 and PAG‐2 levels and pH values than fluids from non‐infected controls, provided that the samples tested showed the presence of antibodies. The clinical implications of these findings are that following infection with N. caninum, most cows will experience some level of placental damage and that this injury correlates with foetal fluid PAG levels and pH.  相似文献   
3.
Lactating dairy cows (n = 72) with a mature corpus luteum (CL) (diameter of > or = 17 mm) determined by ultrasonography and having a follicle with a diameter of > or = 10 mm were randomly assigned to four groups. Cows were treated with cloprostenol i.m. once or twice, or with dinoprost i.m. once or twice with an 8-h interval. The ovaries of each cow were scanned daily by transrectal ultrasonography to measure the changes in the areas of CL and the largest follicle and to determine the occurrence of ovulation. Oestrus was verified twice daily. In addition, blood sample was withdrawn from each cow daily for measuring progesterone (P4) concentrations. Significant decreases in the percentage changes relative to areas of CL and P4 concentrations or increases in the percentage changes in the area of the largest follicle on day 0 were detected in each group during the experiment. However, the type of the drug and the number of the treatments had no significant effect on those parameters. Cows ovulated with or without showing oestrus (group A) and cows exhibiting no oestrus and ovulation (group B) were also evaluated. In contrast to the mean area of the CL and the mean concentration of P4 on day 0, the mean area of the largest follicles between the two groups on day 0 differed significantly. Significant decreases in the percentage changes relative to the area of the CL and P4 concentration or increases in the percentage changes relative to the area of the largest follicle during the experiment were detected in both groups; however, there were no group differences. Treatment of dairy cows with two injections of prostaglandins (cloprostenol or dinoprost) at an 8-h interval resulted in more cows being observed in oestrus within 5 days after treatment and having significantly higher pregnancy rate than those treated with a single prostaglandin injection.  相似文献   
4.
Restriction endonuclease analysis was used, in conjunction with viral neutralization and growth-curve experiments, to compare a bovine herpesvirus type 1 (BHV-1) isolate, originally obtained from bovine mammary gland lesions, with a standard BHV-1 strain, infectious bovine rhinotracheitis virus. Although differences were not detected by viral neutralization or growth-curve experiments, restriction fragment patterns generated by Bam HI, Eco RI, Hind III, and Hpa I, revealed definite differences between the isolate and the prototype strain. Additionally, Eco RI, Hind III, and Hpa I patterns revealed that the mammary gland isolate had DNA-fragment patterns characteristic of infectious pustular vulvovaginitis strain of BHV-1, type 2b. Seemingly, type-2b isolates, similar to types 1 and 2a, may be capable of causing divergent types of infection of variable severity in cattle.  相似文献   
5.
A preliminary serological survey of viral antibodies in Peruvian sheep   总被引:1,自引:0,他引:1  
This study reports the sero-prevalence of viral infections in sheep in Peru. Serum samples were collected from 34 mature healthy rams located in 3 different geographic regions of the country (north, central and south). The sera were tested for antibodies to the following viruses: respiratory syncytial virus (RSV); parainfluenza 3 (PI-3) virus; bovine viral diarrhea/border disease (BVD/BD) virus; bovine herpesvirus 1 (BHV-1); bluetongue (BT) virus; ovine progressive pneumoniae (OPP) virus; bovine leukosis virus (BLV). The serological studies showed that 47% were positive for RSV; 82% for PI-3; 3% for BVD/BD virus; 49% for BT virus; 13% for OPP virus. Antibodies were not detected to bovine herpesvirus 1 or to bovine leukosis virus.  相似文献   
6.
The recent upgrade in IVP technology seen in cattle can be adapted to embryo production in small ruminants to overcome limitations exhibited by surgical procedures on preserving the reproductive potential of donors and the efficiency of embryo production. The aim of the present study was to assess the current procedures used in cattle for the production of IVP embryos in goats and sheep based on laparoscopic-aided ovum pick-up (LOPU) supplied oocytes. Sexually matured goat and sheep donors were treated during the breeding season with FSH and subjected to laparoscopic-guided follicular puncture under general anaesthesia. The collected cumulus-oocyte complexes were matured in medium 199 and fertilized by frozen-thawed spermatozoa using Talp medium supplemented with heparin and oestrus-sheep serum. Cleaved ova were either cultured in sheep in vitro fertilization medium plus amino acids or transferred to sheep oviducts. Blastocyst rate, hatching rate and development rate up to term were used as markers of embryo function. The results obtained for goat and sheep involving 30 and 35 donors respectively (10 and 9 LOPU sessions) were 81.2% and 85.2% of oocyte collection rate; 88.3% and 98.6% oocyte incubation rate; 85.6% and 76.0% fertilization rate; 82.4% and 93.4% of cleavage rate; 50.0% and 61.5% IVP blastocyst rate; 42.1% and 45.5% blastocyst rate in oviducts; 73.0% and 66.7% embryo survival up to term, respectively. The results are comparable to those obtained in small ruminants and in bovines suggesting that requirements for embryo production and development are similar.  相似文献   
7.
8.
9.
Comparative features of retroviral infections of livestock   总被引:2,自引:0,他引:2  
Retroviral infections of livestock have become of increasing importance due to their usefulness as comparative models for human retroviral infections and their effects upon animal health and marketability of animals and animal products nationally and internationally. This paper presents a perspective on the retroviruses of economic concern in veterinary medicine with emphasis on the importance of understanding the modes of virus transmission and the species specificity of the viruses. The retroviruses reviewed include the oncovirus, bovine leukosis virus, and the lentiviruses, equine infectious anemia virus; maedi/visna virus, caprine arthritis-encephalitis virus and bovine visna-like virus. The comparative features amongst these animal retroviruses and those of humans must be recognized by the veterinary and medical professions since the similarities in virus replication and spread by blood transfer can provide important clues in controlling and perhaps preventing human retroviruses infections, such as the human immunodeficiency virus.  相似文献   
10.
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