全文获取类型
收费全文 | 5979篇 |
免费 | 398篇 |
国内免费 | 205篇 |
专业分类
林业 | 314篇 |
农学 | 427篇 |
基础科学 | 68篇 |
1009篇 | |
综合类 | 875篇 |
农作物 | 377篇 |
水产渔业 | 399篇 |
畜牧兽医 | 2440篇 |
园艺 | 140篇 |
植物保护 | 533篇 |
出版年
2023年 | 38篇 |
2022年 | 55篇 |
2021年 | 100篇 |
2020年 | 90篇 |
2019年 | 115篇 |
2018年 | 136篇 |
2017年 | 162篇 |
2016年 | 168篇 |
2015年 | 133篇 |
2014年 | 173篇 |
2013年 | 256篇 |
2012年 | 295篇 |
2011年 | 321篇 |
2010年 | 261篇 |
2009年 | 234篇 |
2008年 | 309篇 |
2007年 | 304篇 |
2006年 | 260篇 |
2005年 | 246篇 |
2004年 | 224篇 |
2003年 | 282篇 |
2002年 | 344篇 |
2001年 | 334篇 |
2000年 | 198篇 |
1999年 | 155篇 |
1998年 | 46篇 |
1997年 | 47篇 |
1996年 | 39篇 |
1995年 | 54篇 |
1994年 | 49篇 |
1993年 | 40篇 |
1992年 | 58篇 |
1991年 | 53篇 |
1990年 | 64篇 |
1989年 | 70篇 |
1988年 | 45篇 |
1987年 | 46篇 |
1986年 | 39篇 |
1985年 | 41篇 |
1984年 | 58篇 |
1983年 | 35篇 |
1982年 | 30篇 |
1981年 | 30篇 |
1979年 | 36篇 |
1978年 | 34篇 |
1977年 | 34篇 |
1975年 | 31篇 |
1974年 | 41篇 |
1972年 | 34篇 |
1971年 | 38篇 |
排序方式: 共有6582条查询结果,搜索用时 15 毫秒
1.
G W De Lisle D M Collins H F Huchzermeyer 《The Onderstepoort journal of veterinary research》1992,59(2):163-165
Restriction endonuclease analysis and DNA hybridization revealed five ovine strains of Mycobacterium paratuberculosis from South Africa had identical DNA patterns to an ovine strain from Canada. Genetically this strain type has features in common with the two major groups of M. paratuberculosis. 相似文献
2.
Luc Van Ham Marc Vandevelde Miek Desmidt Mulenda Tshamala Luc De Schaepdrijver Daniel Mattheeuws 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1994,8(4):290-292
A central axonopathy in 2 male and 1 female Scottish Terrier puppies from 3 different but related litters is reported. Clinical signs consisting of severe whole-body tremors and ataxia were first detected at the age of 10 to 12 weeks. They worsened with activity and excitement and diminished during rest or sleep. Two dogs also had paraparesis. In 1 dog the neurological deficits progressed over several months. Neuropathological examination revealed widespread axonal changes, vacuolation, and gliosis in the white matter of the central nervous system. 相似文献
3.
4.
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
5.
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
6.
1. Treatment of rapeseed meal with calcium hydroxide suspension decreased the sinapine content by up to 90%. Smaller decreases were obtained by autolysis, steaming and treatment with ammonia.
2. When this treated meal was fed to susceptible ("tainting") hens the concentration of trimethylamine in the eggs was decreased to much less than that required to cause taint. 相似文献
7.
8.
Young pigs were exposed to an aerosol of a nonpathogenic strain of Escherichia coli and then were retained in air-pollutant exposure chambers for a 2-hour clearance period. In series 1 (n = 80 pigs), 40 exposed young pigs (principals; 15.5 days of age) were placed in an atmosphere of filtered room air + 50 ppm of atmospheric NH3 during the clearance period; control pigs were exposed to filtered room air without added NH3. In series 2 (n = 24 pigs), 12 exposed young pigs (principals; 6.2 days of age) were similarly maintained, but at a lower concentration of atmospheric NH3 (75 ppm). At the end of the clearance period pigs were killed and pulmonary bacterial clearance was determined. Pigs kept in the NH3-contaminated atmospheres (either concentration) harbored more bacteria, on the average, in their lungs than did the controls. If series 1 and 2 data were combined, pigs kept in the NH3-contaminated atmospheres had 51% more bacteria in their lungs than did the controls. Pulmonic weight and ratio of pulmonic weight to body weight of pigs kept in the NH3-contaminated atmosphere were greater than those of the controls in series 1, but not in series 2. Gross and histopathologic examinations of lung tissue generally revealed no differences between controls and principals in either series 1 or 2. 相似文献
9.
A. Hobson‐Frohock R. G. Fenwick D. G. Land R. F. Curtis A. L. Gulliver 《British poultry science》1975,16(2):219-222
1. Certain rapeseed meals in the diet of hens laying brown eggs result in the production, from some birds, of eggs which have a “ fishy ” or “ crabby ” odour because of the presence of trimethylamine.
2. Such susceptible birds have been used to demonstrate that the activity can be extracted from rapeseed meal with appropriate solvents. 相似文献
10.
A 3‐year‐old Arabian mare presented with diarrhoea and depression. During hospitalisation, the mare developed septic thrombophlebitis associated with a jugular catheter. One week later, she developed secondary bilateral tarsocrural joint septic arthritis. Following surgical intervention and intensive medical therapy, the mare recovered successfully. The case highlights an unusual and previously unreported complication of septic thrombophlebitis. 相似文献