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   574篇
  免费   34篇
  国内免费   1篇
林业   28篇
农学   52篇
基础科学   8篇
  142篇
综合类   50篇
农作物   20篇
水产渔业   44篇
畜牧兽医   230篇
园艺   11篇
植物保护   24篇
  2022年   7篇
  2021年   4篇
  2020年   7篇
  2019年   5篇
  2018年   11篇
  2017年   7篇
  2016年   11篇
  2015年   13篇
  2014年   11篇
  2013年   24篇
  2012年   22篇
  2011年   18篇
  2010年   15篇
  2009年   12篇
  2008年   20篇
  2007年   37篇
  2006年   40篇
  2005年   32篇
  2004年   43篇
  2003年   29篇
  2002年   25篇
  2001年   21篇
  2000年   10篇
  1999年   16篇
  1998年   9篇
  1997年   9篇
  1996年   3篇
  1995年   13篇
  1994年   7篇
  1993年   5篇
  1992年   10篇
  1991年   7篇
  1990年   9篇
  1989年   4篇
  1988年   5篇
  1987年   5篇
  1985年   5篇
  1983年   3篇
  1982年   6篇
  1979年   2篇
  1978年   8篇
  1977年   6篇
  1976年   5篇
  1975年   10篇
  1974年   3篇
  1973年   9篇
  1971年   2篇
  1970年   3篇
  1968年   2篇
  1966年   2篇
排序方式: 共有609条查询结果,搜索用时 15 毫秒
81.
82.
83.
Two groups of blue fox pups about 1½— 2 and 2½—3 months old, respectively, suffering from experimental encephalitozoonosis, were examined clinically and serologically. Antibodies to Encephalitozoon cuniouli were detected in all pups, the titres varying within the range 10–12,800. In addition to unspecific signs of disease the pups showed various neurological disturbances including ataxia, posterior weakness, lameness and circling behaviour, terminaiting in recumbency, paralysis or convulsions. Reduced sight or blindness was observed occasionally. Some of the pups appeared thirsty. Haematological examinations revealed pronounced leukocytosis without any conspicuous shift within the various groups of leukocytes. Biochemical examinations of serum showed significant elevated values of urea nitrogen, creatinine, and magnesium concentrations, reflecting renal dysfunction. Alanine aminotransferase was found significantly depressed in both groups. Raised levels of total protein were demonstrated due to pronounced hyperglobulinaemia. This finding, together with the common occurrence of generalized polyarteritis nodosa and proliferations of plasma cells in clinically affected pups, is probably a result of autoimmune disturbances initiated directly or indirectly by the protozoan infection.  相似文献   
84.
A Working Party of the European Association for Animal Production surveyed the breed comparison and crossbreeding trials which were being carried out in Europe. The survey summarizes the experimental work in the different countries and gives details on 86 separate projects concerned with breed and strain evaluation in pure and crossbreeding situations. The paper gives a general summary of the survey and recommendations on the methodology for future experiments. More detailed abstracts of the individual trials included in the survey are obtainable on request.  相似文献   
85.
Enzymoserological comparison of a selection of leptospira strains tested with sera from rabbits immunized with unpurified DNase of Leptospira interrogans, serotype canicola, indicates the production of DNase of serologically very similar properties by the serotypes canicola, autumnalis, icterohemorrhagiae and pomona. The DNase produced by serotype hyos was serologically different from the others, while the serotypes grippotyphosa and bataviae did not produce DNases at all. The method used made it possible to differentiate between leptospiral DNase and normally occurring DNases in the serum samples. Neither leptospira DNase nor specific leptospira-DNase-antibodies could be detected in dog sera with high agglutinationlysis titres after natural infection.  相似文献   
86.
A recently observed lethal congenital defect of purebred Holstein calves is reported. Eighteen genetically related calves were necropsied. One calf had been aborted on gestation day 159, and the others were delivered between day 250 and day 285. Birth weights were reduced. The defect was characterized by shortening of the cervical and thoracic parts of the vertebral column due to multiple hemivertebrae, fused and misshaped vertebrae, and scoliosis. Symmetrical flexures of the carpal joints and the metacarpophalangeal joint in combination with a slight lateral rotation of the phalanges also were present. Similar low-grade arthrogryposis was present in the posterior limbs. Fifty percent of the calves had heart malformation. Other malformations occurred in a few calves. Complex vertebral malformation (CVM) is proposed as the designation for this defect. A genetic etiology is indicated because cases occurred following breeding between genetically related individuals. Two common ancestors were found; both were former elite sires of US Holstein origin. Because of the widespread international use of semen from sires occurring in the pedigrees of affected calves, CVM is expected to occur in several countries.  相似文献   
87.
Endotoxin-induced synthesis of thromboxane A2 (TXA2), prostacyclin (PGI2) and prostaglandin E2 (PGE2) was studied in 3 cows after intravenous E. coli endotoxin (055:B5-0.025 mg/kg b.w.) administration. Blood sampling and monitoring of clinical signs were performed from 2 h prior to until 6 h after endotoxin challenge. Blood samples were analyzed for stable hydrolysis products of TXA2 (TXB2), PGI2 (6-keto PGF) and PGE2 (bicyclic PGE2), biochemical and haematological parameters. In a similar experimental design the efficacy of the non-steroidal anti-inflammatory drugs (NSAID) flunixin meglumine (FM) and phenylbutazone (PB) in suppressing eicosanoid synthesis and clinical signs in response to endotoxin challenge was investigated. Two groups of cows, each comprising 2 animals, were treated with FM and PB prior to endotoxin challenge. It was observed that plasma concentrations of TXB2, 6-keto PGF and bicyclic PGE2 increased rapidly after endotoxin challenge. Concentrations were significantly elevated for hours and were correlated to the severity of clinical signs of endotoxicosis. Pretreatment with NSAID suppressed mediator production and alleviated clinical signs. The experiments suggest a certain pathophysiological role of TXA2, PGI2 and PGE2 for the early systemic ill-effects of bovine endotoxicosis.  相似文献   
88.
Age-prevalence and age-intensity data of Echinococcus granulosus hydatid cysts in sheep populations were collected in an abattoir in the Xinjiang Uygur Autonomous Region, People's Republic of China. The frequency distribution of the larval cysts per sheep was empirically described by the negative binomial model, with parameter k being 0.5273. A mathematical model for the life cycle of E. granulosus was applied to the collected data and the results show that the infection pressure on sheep was 0.4362 (female) or 0.4119 (male) infections per year, the mean number of cysts increased linearly by 0.8824 (female) or 0.9971 (male) cysts every year and acquired immunity was too low to depress this rate of increase. According to certain definitions of steady states for taeniid populations, it was concluded that at least in some parts of Xinjiang, the life cycle of E. granulosus was and may still be in an endemic steady state. Consequently, the regular dog-dosing program would readily drive the infection from an endemic state towards extinction.  相似文献   
89.
Residual energy intake, defined as actual minus predicted energy intake during a production period, was estimated for each of 650 bull calves of 31 Holstein Friesian or Brown Swiss sires. Residual energy intake, measured under ad libitum feeding, had heritabilities similar to those of growth rate and energy conversion ratio with an estimate of approximately .3. Residual energy intake was related to average daily energy intake both phenotypically and genetically such that selection for decreased residual energy intake would lead to a decrease in daily feed intake. Such selection would also tend to increase carcass fatness (i.e., genetically fat animals are the most efficient). Residual energy intake estimated with and without correction for carcass composition were closely correlated. Thus, residual energy intake may be estimated without the knowledge of carcass composition in growing bulls of dual-purpose breeds.  相似文献   
90.
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