全文获取类型
收费全文 | 86117篇 |
免费 | 5430篇 |
国内免费 | 770篇 |
专业分类
林业 | 3140篇 |
农学 | 2496篇 |
基础科学 | 675篇 |
9805篇 | |
综合类 | 16398篇 |
农作物 | 3022篇 |
水产渔业 | 3752篇 |
畜牧兽医 | 46993篇 |
园艺 | 1121篇 |
植物保护 | 4915篇 |
出版年
2021年 | 721篇 |
2020年 | 934篇 |
2019年 | 986篇 |
2018年 | 1441篇 |
2017年 | 1661篇 |
2016年 | 1446篇 |
2015年 | 1437篇 |
2014年 | 1683篇 |
2013年 | 3098篇 |
2012年 | 3014篇 |
2011年 | 3637篇 |
2010年 | 2411篇 |
2009年 | 2357篇 |
2008年 | 3207篇 |
2007年 | 3031篇 |
2006年 | 2725篇 |
2005年 | 2644篇 |
2004年 | 2421篇 |
2003年 | 2474篇 |
2002年 | 2351篇 |
2001年 | 2613篇 |
2000年 | 2630篇 |
1999年 | 2026篇 |
1998年 | 920篇 |
1997年 | 856篇 |
1996年 | 777篇 |
1995年 | 873篇 |
1994年 | 777篇 |
1993年 | 791篇 |
1992年 | 1661篇 |
1991年 | 1840篇 |
1990年 | 1790篇 |
1989年 | 1694篇 |
1988年 | 1564篇 |
1987年 | 1638篇 |
1986年 | 1619篇 |
1985年 | 1464篇 |
1984年 | 1256篇 |
1983年 | 1079篇 |
1982年 | 706篇 |
1979年 | 1061篇 |
1978年 | 831篇 |
1976年 | 712篇 |
1975年 | 746篇 |
1974年 | 1005篇 |
1973年 | 988篇 |
1972年 | 953篇 |
1971年 | 879篇 |
1970年 | 852篇 |
1969年 | 804篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Benny J. Woody DVM MS Michael J. Murphy DVM PhD AIlen C. Ray PhD Robert A. Green DVM PhD 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1992,6(1):23-28
The clinical signs and laboratory changes of brodifacoum (BDF) intoxicated dogs and their response to vitamin K1 treatment were examined. Brodifacoum, a second-generation anticoagulant rodenticide, was fed to four dogs for 3 consecutive days producing a cumulative dose of 1.1 mg BDF/kg body weight. Clinical observations of the animals were made daily throughout the study. Monitored laboratory parameters included: one-stage prothrombin time (OSPT), activated partial thromboplastin time (APTT), activated coagulation time (ACT), complete blood counts, thrombocyte counts, and serum chemistry values. Response to vitamin K1 therapy was evaluated clinically and by laboratory tests. Serum BDF concentrations were monitored. Inappetence and hemorrhagic tendencies were exhibited by day 5 postrodenticide exposure. One-stage prothrombin time, APTT, and ACT were 25% greater than time zero values at 24, 24, and 72 hours postdosing, respectively. All laboratory parameters returned to normal within 48 hours of initiating vitamin K1 therapy (0.83 mg/kg orally, TID for 5 days). Serum brodifacoum concentrations were highest (1065-1215 ng/mL) during the 3 days after BDF dosing and were detectable (3.0-7.5 ng/mL) until day 24 postexposure. A mean BDF elimination half-life of 6 +/- 4 days was observed. 相似文献
52.
Howard A. Clonts Curtis M. Jolly Syed Abdulkadir L. Alsagoff 《Journal of the World Aquaculture Society》1989,20(4):268-276
The merits of integrated aquaculture farming (IAF) as a strategy for bolstering income for the rural poor have been recognized, but the economic efficiency and sustainability are yet to be determined. The effects of one species on another and the economic benefits, net of government support, have not been critically evaluated. The concept of a foodniche for alternative species in an aquatic environment has not been properly tested in an economic setting. Thus, this report reflects the results of applying the technique of mixed integer linear programming to determine the optimum combination of species within the context of a foodniche. The objective also included maximizing revenues, with minimal external input requirements, for a representative small Malaysian wet-rice farm. It was found that the foodniche concept permitted flexibility in stocking rates, and that farmers could actually stock species at the exact rate that was optimal for profit, instead of standard fixed rates. Also, government subsidies for pond construction were essential for IAF success. The net revenues from IAF were low without interest-free loans for pond construction. 相似文献
53.
Melody L. Danley P. Brett Kenney Patricia M. Mazik Rodney Kiser Joseph A. Hankins 《Journal of the World Aquaculture Society》2005,36(3):249-261
Rainbow trout Oncorhynchus mykiss (261.6 × 24.7 g initial weight, mean × SEM) at 13.1 × 0.2 C were exposed for 94 d to one of three CO2 treatments: control (22.1 × 2.8 mg/L), medium (34.5 × 3.8 mg/L), or high (48.7 × 4.4 mg/L). Trout were checked daily for survival, and fish were sampled at 0, 28, 56, and 84 d for physiological responses, growth, and fillet quality assessments. Trout were also challenged to a 15-min crowding stress at 93 d to assess their ability to initiate a stress response during hypercapnia. Chronically exposed trout showed nearly 100% survival through 84 d exposure (1 of 1,500 fish died). Growth and physiological results showed that increasing elevated CO2 , concentrations result in corresponding decreased growth rates and CO2 specific physiological parameters: The medium and high CO2 treatments had significantly slower growth and subsequently smaller fish by 84 d. Exposed trout also showed significantly ( P < 0.05) decreased plasma chloride for medium and high CO2 treatments compared to the control from 28 through 84 d. Decreased growth and smaller fish in the medium and high CO2 treatments resulted in correspondingly smaller fresh and smoked fillet weights. Chronic CO2 exposure did not result in notable changes in ultimate muscle pH. Exposure to 15-min crowding stress at 93 d resulted in significant changes in hematocrit, plasma cortisoI, glucose, and chloride for all treatment groups. CO2 -specific changes were detected in hematocrit, plasma cortisoI, and plasma chloride responses following the 15-min crowding stress. 相似文献
54.
55.
56.
Six Friesian calves from a pedigree herd died or were killed within 1 week of birth because of progressive central nervous disease in which the only consistent lesion was cerebral oedema. The cause was citrullinaemia, resulting from an autosomally inherited dysfunction of the urea cycle enzyme arginosuccinate synthetase. Citrullinaemia was diagnosed by demonstrating markedly elevated concentrations of citrulline in the blood of one calf and in the cerebral spinal fluid of another. One of two sires used in the herd was a heterozygous carrier of the disease. Heterozygocity was demonstrated using a polymerase chain reaction/restriction endonuclease test designed to detect the genetic mutation that causes citrullinaemia in cattle. 相似文献
57.
Brezonik PL 《Science (New York, N.Y.)》1986,231(4742):1202-1203
58.
L K 《Science (New York, N.Y.)》1986,234(4783):1595
59.
60.
Harasen GL 《The Canadian veterinary journal. La revue veterinaire canadienne》1985,26(6):193-194
Two cases of noninfectious, nonerosive arthritis are presented. The diagnostic features, clinical course and treatment are reviewed. Potential etiologies are discussed in the light of relatively little current material on this subject in the veterinary literature. 相似文献