全文获取类型
收费全文 | 280979篇 |
免费 | 16432篇 |
国内免费 | 668篇 |
专业分类
林业 | 23967篇 |
农学 | 14100篇 |
基础科学 | 2958篇 |
44363篇 | |
综合类 | 33032篇 |
农作物 | 17381篇 |
水产渔业 | 17481篇 |
畜牧兽医 | 113547篇 |
园艺 | 6425篇 |
植物保护 | 24825篇 |
出版年
2020年 | 2900篇 |
2019年 | 3698篇 |
2018年 | 4183篇 |
2017年 | 4552篇 |
2016年 | 4927篇 |
2015年 | 4394篇 |
2014年 | 5770篇 |
2013年 | 16396篇 |
2012年 | 7023篇 |
2011年 | 9141篇 |
2010年 | 7632篇 |
2009年 | 8152篇 |
2008年 | 8431篇 |
2007年 | 7556篇 |
2006年 | 8068篇 |
2005年 | 7251篇 |
2004年 | 7112篇 |
2003年 | 6910篇 |
2002年 | 6226篇 |
2001年 | 7116篇 |
2000年 | 6704篇 |
1999年 | 6139篇 |
1998年 | 4270篇 |
1997年 | 4303篇 |
1996年 | 4038篇 |
1995年 | 4649篇 |
1994年 | 4032篇 |
1993年 | 3778篇 |
1992年 | 5004篇 |
1991年 | 5146篇 |
1990年 | 4857篇 |
1989年 | 4919篇 |
1988年 | 4351篇 |
1987年 | 4397篇 |
1986年 | 4405篇 |
1985年 | 4652篇 |
1984年 | 4182篇 |
1983年 | 3920篇 |
1982年 | 3122篇 |
1981年 | 3013篇 |
1980年 | 2972篇 |
1979年 | 3598篇 |
1978年 | 3198篇 |
1977年 | 2948篇 |
1976年 | 2796篇 |
1975年 | 2688篇 |
1974年 | 2973篇 |
1973年 | 2932篇 |
1972年 | 2677篇 |
1971年 | 2619篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Losses due to mortality and rejection of carcases and viscera in a population of 2,959,607 pigs admitted for slaughter in Singapore abattoirs between 1984 and 1986 were studied. Mortality losses were 2822 pigs (9.5 per 10,000 admissions) while 3039 whole carcases (10.3 per 10,000 admissions) were condemned at post-mortem examination. The main reason for rejection of carcases was pyaemia (30.3%). Kidneys and livers were the two main organs of economic value rejected. Rejection of kidneys was primarily due to nephritis (54.8%) while liver condemnation was mainly due to cirrhosis (38.6%). The financial loss from abattoir rejection was S$5.27 millions or S$1.78 per pig admitted. The value of abattoir condemnation data as a tool in preventive medicine is discussed. 相似文献
72.
Abstract. The use of an indirect enzyme-linked immunosorbent assay ( elisa ) for the detection of channel catfish antibody to Edwardsiella ictaluri is described. Changes in agglutination titre in fish immunized with Edwardsiella ictaluri heat killed whole bacterins or lipopolysaccharides were reflected by corresponding changes in elisa readings. Relatively high correlations were observed among elisa OD readings, computed elisa titres and corresponding agglutination titres. 相似文献
73.
Serum amyloid A protein (SAA) in horses: objective measurement of the acute phase response 总被引:1,自引:0,他引:1
M B Pepys M L Baltz G A Tennent J Kent J Ousey P D Rossdale 《Equine veterinary journal》1989,21(2):106-109
A sensitive and precise immunoassay for equine serum amyloid A protein (SAA) was established and used to determine, for the first time, the circulating concentration of this protein in health and disease. As in other species, equine SAA was present only at trace levels in healthy animals but behaved as an extremely sensitive and rapidly responding acute phase reactant following most forms of tissue injury, infection and inflammation, objectively reflecting the extent and activity of disease. Measurements of SAA should make a significant contribution to diagnosis and management of viral and bacterial infection in horses, and routine serial assays could provide an objective criterion for monitoring prospectively the general health of horses in training and racing. 相似文献
74.
75.
M Steinhardt S Reimer U Bünger J Kutschke 《Archiv fuer experimentelle veterinaermedizin》1989,43(2):309-314
Comprehensive studies into domestic pigs and wild boars together with literature data provided a basis for an assessment of aerobic metabolic capacity (VO2max) of swine. The values quoted, from 20 to 94 ml/min-1/kg, had been due to several factors of methodological approach, growth, training, and nutrition as well as to pathophysiological aspects. For full capacity utilisation of VO2max, untrained pigs can be challenged at belt velocities between 0.8 and 1.8 m/s-1 and trained animals at 5 m/s-1. 相似文献
76.
White leghorn hens were experimentally infested with northern fowl mites (Ornithonyssus sylviarum) and antibody responses to mite immunogens were monitored over 12 weeks. Mite burdens increased during the early phase of infestation and declined over the latter weeks of the study. Antigen was prepared from homogenized whole mites, which were then sonicated and extracted with non-ionic detergent. Antigen extract was fractionated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and antibody-reactive polypeptides were identified by immunoblotting. At the start of infestation, hens had natural, pre-existing antibodies that reacted with several mite-extract components. Individual hens had different natural antibody reactivities; however, all birds had immunoglobulins reactive with extract polypeptides of 117,000, 77,000 and 36,000 molecular weight. A variety of mite extract components reacted with hen antibodies generated in response to experimental infestation. The number of antibody-reactive mite polypeptides increased through week 8 of infestation and then decreased by week 12. Fifteen polypeptides of northern fowl mite extract were reactive with antibodies developed by the majority of infested birds. These commonly reactive polypeptides had molecular weights ranging from 40,000 to 160,000. Glycoconjugates of fractionated mite extract were identified by blotting with lectins that have different carbohydrate binding specificities. Also identified were lectins that bound extract components with the same molecular weights as those moieties complexed by immunoglobulins of infested birds. 相似文献
77.
A urinary bladder mass in a 12-year-old spayed female West Highland White Terrier was diagnosed after exploratory surgery and biopsy as a transitional cell carcinoma. Four months later the dog presented with an ulcerated plaque-like cutaneous lesion at the previous surgical incision site; concurrent inguinal lymphadenopathy and recurrence of the urinary bladder mass were identified. Transitional cell carcinoma was diagnosed at all 3 sites. Although a definitive relationship cannot be established between the initial surgery for urinary bladder mass and the resultant subcutaneous lesion, surgical implantation should be considered as a source for the neoplastic cells. 相似文献
78.
The effect of heat stress on the components of grain weight was analysed in wheat ( Triticum aestivum L.) varieties differing in grain weight stability. The wheat varieties PBW154, Sonalika and Hindi62 were raised in the field (New Delhi, India; 77°12' E, 28°40' N, 228.6 m a.s.l.) at three dates of sowing: 19 November 1992 (DOS I), 14 December 1992 (DOS II) and 18 January 1993 (DOS III). The late-sown crop (DOS III) experienced 6–8 °C warmer temperatures during grain development than the crop sown at the normal time (DOS I). The heat susceptibility index (S) revealed that grain weight was less susceptible to heat in Sonalika and PBW154 than in Hindi62. Heat stress reduced both the grain growth duration (GGD) and the grain growth rate (GGR). The grain weight reduction in PBW154 and Sonalika was mainly due to a reduction in GGR, while that of Hindi62 was due to a reduction in GGD. In vivo studies on starch and protein synthesis in excised endosperm at 15, 25 and 35 °C revealed that both processes were more thermotolerant in Hindi62 than in PBW154. The grain starch content was stable in Hindi62 while that in PBW154 was significantly reduced under heat stress. The grain nitrogen content at maturity increased in both varieties under heat stress. It was concluded that the heat susceptibility of grain weight in Hindi62 was mainly due to a reduction in GGD, although GGR, starch and protein synthesis were more thermotolerant in developing grains of Hindi62 than in those of PBW154. 相似文献
79.
80.