全文获取类型
收费全文 | 241570篇 |
免费 | 14775篇 |
国内免费 | 1643篇 |
专业分类
林业 | 24165篇 |
农学 | 15231篇 |
基础科学 | 3853篇 |
42843篇 | |
综合类 | 22413篇 |
农作物 | 17566篇 |
水产渔业 | 16522篇 |
畜牧兽医 | 85190篇 |
园艺 | 6552篇 |
植物保护 | 23653篇 |
出版年
2021年 | 2874篇 |
2020年 | 3206篇 |
2019年 | 4022篇 |
2018年 | 4081篇 |
2017年 | 4578篇 |
2016年 | 4973篇 |
2015年 | 4678篇 |
2014年 | 6013篇 |
2013年 | 16608篇 |
2012年 | 6227篇 |
2011年 | 7946篇 |
2010年 | 7604篇 |
2009年 | 8219篇 |
2008年 | 7265篇 |
2007年 | 6320篇 |
2006年 | 7028篇 |
2005年 | 6192篇 |
2004年 | 5822篇 |
2003年 | 5587篇 |
2002年 | 4954篇 |
2001年 | 5284篇 |
2000年 | 4941篇 |
1999年 | 4855篇 |
1998年 | 4193篇 |
1997年 | 4230篇 |
1996年 | 3986篇 |
1995年 | 4524篇 |
1994年 | 3876篇 |
1993年 | 3613篇 |
1992年 | 3792篇 |
1991年 | 3901篇 |
1990年 | 3612篇 |
1989年 | 3563篇 |
1988年 | 3134篇 |
1987年 | 3248篇 |
1986年 | 3099篇 |
1985年 | 3456篇 |
1984年 | 3325篇 |
1983年 | 3149篇 |
1982年 | 2694篇 |
1981年 | 2655篇 |
1980年 | 2607篇 |
1979年 | 2791篇 |
1978年 | 2623篇 |
1977年 | 2432篇 |
1976年 | 2292篇 |
1975年 | 2104篇 |
1974年 | 2261篇 |
1973年 | 2154篇 |
1971年 | 1962篇 |
排序方式: 共有10000条查询结果,搜索用时 250 毫秒
991.
Birds Their Structure and Function, By A. S. King and J. McLelland, 1984. 2nd ed. 334 pp. illustrated. London, Baillière Tindall. £9.50. ISBN 0 7020 0872 9.
Proceedings of the 2nd European Symposium on Poultry Welfare, 1985. 360 pp. illustrated. German Branch of the World's Poultry Science Association, Celle, Institut für Kleintierzucht. 相似文献
992.
Curtis RA Viel L McGuirk SM Radostits OM Harris FW 《The Canadian veterinary journal. La revue veterinaire canadienne》1986,27(4):170-172
The purpose of this paper is to emphasize the importance of pulmonary auscultation for the clinician. It suggests a clarification and simplification of the terminology to be used which would be helpful to veterinary students and allow better communications between veterinarians. The interpretation of these sounds and the relationships to conditions and diseases of the lungs in cattle, horses, sheep and goats are discussed. 相似文献
993.
994.
Barlett PF 《Science (New York, N.Y.)》1986,234(4779):1015
995.
Oz HH Nicholson SS Al-Bagdadi FK Zeman DH 《The Canadian veterinary journal. La revue veterinaire canadienne》1986,27(1):13-16
This is the report of clinical signs and lesions of a cerebellar disorder in an adult four year old Limousin cow grazing perennial ryegrass (Lolium perenne). The most striking histopathological lesion was a marked paucity of Purkinje cells throughout the cerebellum. 相似文献
996.
997.
Kingscote BF Wilson D 《The Canadian veterinary journal. La revue veterinaire canadienne》1986,27(11):440-442
Abortions occurred in 18% of 131 beef cows and heifers during two months, on a farm in southern Saskatchewan. The losses began two weeks after acute febrile illness and agalactia in a dairy cow to which the beef herd had been exposed. A diagnosis of Leptospira interrogans serovar pomona infection was made on the basis of serology in cows and the finding of leptospires in fetal tissues by fluorescent antibody test. Tentative diagnosis of infectious bovine rhinotracheitis delayed treatment and prophylaxis until infection attained high intensity in the herd and severe losses to the farmer occurred. Abortions ceased after vaccination against pomona and oxytetracycline treatment of pregnant cows, although chronic debility followed the acute phase of the disease in some cows. Recrudescence of infection was suspected four months later, when acute agalactia occurred in one cow and debility in calves and cows was recurring. Pomona infection was not proven, but dihydrostreptomycin treatment and revaccination were applied to the whole herd. Seroconversion and IgM antibody continued to indicate a persistent source of infection and susceptibility in a minority of the population one year after onset. The source of the original infection is believed to have been a carrier beef cow, or a dairy cow which was leptospiruric at the time of contact with the beef herd. With the exception of one aborted calf, no evidence of pomona infection was found outside the farm, in cattle or wild mammals tested serologically within a radius of 30 km, during one year following the outbreak. 相似文献
998.
999.
E T Kornegay J B Meldrum G Schurig M D Lindemann F C Gwazdauskas 《Journal of animal science》1986,63(2):484-491
Three trials using 240 weanling pigs were conducted during winter months to determine the influence of nursery temperature ("comfortable" vs "cold") on the response of weanling pigs to added vitamin C (700 ppm) or E (55 IU/kg) to a corn-soybean meal diet. A "comfortable" temperature schedule (27 C initially with a weekly 2 C drop) was maintained in one nursery, with the temperature schedule in the "cold" nursery about 8 C lower. Plasma concentrations of vitamin C and vitamin E were elevated when the respective vitamins were added to the diet, but were not consistently influenced by nursery temperatures. Daily gain, daily feed intake and feed efficiency were not improved with the added C or E. Daily feed intake was increased and feed-to-gain ratios were larger for pigs housed in the "cold" nursery compared with pigs housed in the "comfortable" nursery; however, daily gains were similar in the two environments. Pigs housed in the "cold" nursery were slightly stressed, as indicated by heavier adrenal glands, but the antibody response and serum glucocorticoid concentrations were not significantly affected by either diet or temperature. 相似文献
1000.
O'Neill S Boothby JT Feldman BF 《Veterinary clinical pathology / American Society for Veterinary Clinical Pathology》1986,15(1):22-26
A competitive enzyme immunoassay has been used to detect and quantitate fibronectin in canine plasma. In this test, purified fibronectin, bound to microtiter plates, competes with plasma fibronectin for the conjugated antibody, rabbit-anticanine, fibronectin-horseradish peroxidase. The assay could detect fibronectin in purified standards from 58 ng/ml to 580 microgram/ml. The range of 1-100 microgram/ml was linear for plasma samples diluted 1:10, allowing samples with fibronectin concentrations from 10-1000 microgram/ml to be easily measured by this method. The mean normal fibronectin concentration of 132 dogs, by this method, was determined to be 320 +/- 74 microgram/ml. 相似文献