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   131篇
  免费   23篇
  5篇
综合类   7篇
畜牧兽医   133篇
园艺   1篇
植物保护   8篇
  2023年   1篇
  2020年   6篇
  2019年   5篇
  2018年   2篇
  2017年   7篇
  2016年   7篇
  2015年   9篇
  2014年   6篇
  2013年   7篇
  2012年   4篇
  2011年   3篇
  2010年   2篇
  2009年   6篇
  2008年   6篇
  2007年   5篇
  2006年   4篇
  2005年   4篇
  2004年   6篇
  2003年   3篇
  2002年   6篇
  2000年   4篇
  1999年   6篇
  1998年   9篇
  1997年   4篇
  1996年   5篇
  1995年   6篇
  1994年   4篇
  1993年   1篇
  1989年   3篇
  1988年   3篇
  1986年   1篇
  1980年   1篇
  1977年   1篇
  1974年   1篇
  1973年   1篇
  1971年   2篇
  1970年   1篇
  1969年   1篇
  1966年   1篇
排序方式: 共有154条查询结果,搜索用时 0 毫秒
101.
In periods of social crisis, policymakers become particularly vulnerable to interest groups mobilizing to compete for scarce funds. At this point, legislators are no longer able to address the specific needs of their primary constituency directly, but rather are forced to do so in pretext only. New, unfamiliar technologies provide ample ammunition for astute interest groups to take advantage of times of economic turmoil and maneuver for policy support through dramatic campaigns of “salesmanship.” By publicizing a crisis situation, dramatizing it effectively, and advertising an innovation as the solution to the crisis, legislators may be effectively persuaded to give priority to interest group pressures above and beyond those of the local constituency. Iowa's attempts to address the farm crisis through economic development strategies relying on biotechnology is examined in this paper. The results of extensive surveys of Iowa's legislators and farmers are examined and the consequences for Iowa's policy process of using biotechnology under the auspices of economic development are discussed.  相似文献   
102.
The dog is a definitive host of the protozoan parasite Neospora caninum, and in many parts of the world, infection is relatively common as determined by serology. Reported seroprevalences usually range from 0 to 20 per cent, however, reports of clinically affected dogs are infrequent. Affected dogs are generally less than six months old and predominantly have signs of an ascending hindleg paralysis, with the associated lesions of polyradiculoneuritis and granulomatous polymyositis. Although any organ may be affected, infections are more common in the central nervous system, muscles, lungs and skin. Ante-mortem diagnosis is difficult but serology and cytology can aid diagnosis. The diagnosis can be confirmed by histology, immunohistochemistry, the use of molecular techniques on biopsy material, or on post-mortem examination. Neospora caninum oocysts are rarely found in faeces and must be differentiated from oocysts of related coccidians such as Hammondia heydorni and Toxoplasma gondii. Hammondia heydorni can cause diarrrhoea in immunosuppressed dogs. Neosporosis should be suspected in young pups with an ascending paralysis of the hindlegs. Treatment with clindamycin and potentiated sulphonamides may be useful in cases where muscular atrophy and fibrosis are absent. Feeding of raw meat is a potential risk factor for infection of dogs and should be discouraged.  相似文献   
103.
104.
Eighty-six bald eagles found sick or dead during 1973-74 in 24 States were analyzed for organochlorine compounds. DDE was detected in all caracasses; polychlorinated biphenyls (PCB's) were found in all but two. Seventy-five carcasses contained TDE and/or dieldrin. Four eagles had possibly lethal levels of dieldrin in the brain. Bald eagles continue to retain high residue levels of organochlorine pollutants. Illegal shooting remained the most common cause of death but accounted for a smaller percentage of the mortalities than in the two previous biennial collections.  相似文献   
105.
106.
107.
Nitrate–nitrite poisoning killed four adult alpacas and induced the abortion of a full-term fetus after access to oaten hay ( Avena sativa ) containing 3.2% KNO3 equivalent in dry matter. Necropsy findings were cyanosis, dark-coloured blood, and pulmonary congestion and oedema. Aqueous humour from two adults contained 25 mg NO3/L and that from the fetus contained 10 mg NO3/L. Cyanide poisoning possibly killed two adult wether alpacas that ate a garden-cultivated variety of Osteospermum ecklonis (South African daisy, bietou) with a cyanide potential of 6800 mg HCN/kg dry matter.  相似文献   
108.
The site where the semen is deposited appears to be one of the most important factors affecting pregnancy of inseminated goats. In Murciano–Granadina (MG) goats, post-cervical insemination is achieved in a limited number of females. An effective way to increase fertility rate could be by increasing post-cervical inseminations. Effect of exogenous oxytocin application to facilitate the cervical penetration and its effect on kidding rate and prolificacy in MG goats were investigated. Oestrus was synchronized using progesterone-impregnated sponges for 11 days. Females were randomly divided into three groups (n = 190) and received either an i.v. injection of 100 or 200 IU of oxytocin or saline solution 15 min before being inseminated. Data on semen deposition depth were recorded for each animal using a catheter scaled in centimetres (up to 4 cm). Depth of semen deposition was affected by the oxytocin treatment (p < 0.05). Oxytocin enhanced cervical passage only with the dose of 200 IU compared with the control group, increasing the deposition depth (2.9 cm vs 1.9 cm). No significant effect of oxytocin treatment on kidding rate and prolificacy was detected. Depth of semen deposition affected kidding rate (p < 0.01). In conclusion, oxytocin treatment improved the depth of semen deposition in AI of MG goats, but kidding rate and prolificacy was not affected. More studies must be conducted to assess the minimal effective dose required for sufficient cervical dilation, and to determine the effects of such doses of oxytocin on uterine motility, sperm transport and fertility in goats.  相似文献   
109.
110.
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