全文获取类型
收费全文 | 129613篇 |
免费 | 7438篇 |
国内免费 | 76篇 |
专业分类
林业 | 5990篇 |
农学 | 4628篇 |
基础科学 | 806篇 |
15769篇 | |
综合类 | 21889篇 |
农作物 | 4957篇 |
水产渔业 | 6751篇 |
畜牧兽医 | 66663篇 |
园艺 | 1638篇 |
植物保护 | 8036篇 |
出版年
2019年 | 1278篇 |
2018年 | 2060篇 |
2017年 | 2358篇 |
2016年 | 2147篇 |
2015年 | 1857篇 |
2014年 | 2269篇 |
2013年 | 5107篇 |
2012年 | 4004篇 |
2011年 | 4754篇 |
2010年 | 3117篇 |
2009年 | 3171篇 |
2008年 | 4595篇 |
2007年 | 4355篇 |
2006年 | 4233篇 |
2005年 | 3733篇 |
2004年 | 3585篇 |
2003年 | 3614篇 |
2002年 | 3352篇 |
2001年 | 4453篇 |
2000年 | 4360篇 |
1999年 | 3452篇 |
1998年 | 1342篇 |
1997年 | 1414篇 |
1996年 | 1243篇 |
1995年 | 1447篇 |
1994年 | 1280篇 |
1993年 | 1280篇 |
1992年 | 2578篇 |
1991年 | 2620篇 |
1990年 | 2540篇 |
1989年 | 2560篇 |
1988年 | 2274篇 |
1987年 | 2301篇 |
1986年 | 2305篇 |
1985年 | 2217篇 |
1984年 | 1803篇 |
1983年 | 1585篇 |
1979年 | 1583篇 |
1978年 | 1293篇 |
1977年 | 1060篇 |
1976年 | 1075篇 |
1975年 | 1228篇 |
1974年 | 1473篇 |
1973年 | 1381篇 |
1972年 | 1380篇 |
1971年 | 1358篇 |
1970年 | 1314篇 |
1969年 | 1294篇 |
1968年 | 1088篇 |
1967年 | 1175篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
J B Kaneene R F Taylor J G Sikarskie T J Meyer N A Richter 《Journal of the American Veterinary Medical Association》1985,187(11):1132-1133
A retrospective study was conducted to determine disease patterns in reptilian and amphibian populations at the Detroit Zoo from 1973 through 1983. In the reptilian population (mean +/- SD = 285.2 +/- 28), overall annual mortality rates were 1% to 40%. Mortality rates were highest in the fall months (20%) and lowest in the winter months (6%). The most frequently affected reptiles were iguana (Iguana iguana), reticulated python (Python reticulatus), rattlesnakes (Crotalus spp), common boa (Constrictor constrictor), and lizards (various genera of suborder Lacertilia). Of the 1,300 reptilian deaths from 1973 through 1983, 36.6% were caused by microbial agents, 12% by parasites, 11.6% by trauma, and 9.3% by nutritional deficiencies. The main microbial organisms that caused death were Aeromonas spp, Salmonella spp, Pseudomonas spp, Proteus spp, and Edwardsiella spp. The main parasites that caused death were Entamoeba spp and lungworms. Among amphibians, frogs and toads were the most frequently affected, and starvation and trauma were the most frequent causes of death. 相似文献
992.
Feeding and drinking behavior of mares and foals with free access to pasture and water 总被引:1,自引:0,他引:1
The feeding and drinking behavior of 11 mares and 15 foals living on pasture with free access to water was recorded during 2,340 15-min focal samples taken over 2 yr. Lactating mares on pasture spent about 70% of the day feeding. Foals began feeding on their first day of life. As they grew older, they spent progressively more time feeding, but still spent only 47 +/- 6% of the time feeding by 21 wk of age. Foals fed primarily during the early morning and evening. While grass formed the major proportion of the diet of both foals and mares, they also ate clay, humus, feces, bark, leaves and twigs. Almost all feeding by foals was done while their mothers were feeding. Movement to water sources was frequently, but not invariably, carried out by an entire herd. Frequency (P = .005) but not duration (P greater than .05) of drinking bouts by mares increased as the temperature increased. Frequency was greatest at 30 to 35 C, at which temperature mares drank once every 1.8 h. Frequency of drinking varied with the time of day (P less than .01), being rarest during the early morning (0500 to 0900 h eastern daylight time) and most frequent during the afternoon (1300 to 1700 h). Drinking by foals was very rare. The youngest age at which a foal was observed to drink was 3 wk, and 8 of 15 foals were never observed to drink before weaning. 相似文献
993.
Milk fever and calcium metabolism 总被引:1,自引:0,他引:1
Allen, W.M. & Sansoni, B.F. Milk lever and calcium metabolism. J. vet. Pharmacol. Therap. 8, 19–29.
W.M. Allen, Department of Functional Pathology, AFRC Institute for Research on Animal Diseases, Campion, Newbury, Berkshire RC16 ONN, England. 相似文献
W.M. Allen, Department of Functional Pathology, AFRC Institute for Research on Animal Diseases, Campion, Newbury, Berkshire RC16 ONN, England. 相似文献
994.
Induction of diplodiosis, a neuromycotoxicosis, in domestic ruminants with cultures of indigenous and exotic isolates of Diplodia maydis 总被引:1,自引:0,他引:1
T S Kellerman C J Rabie G C van der Westhuizen N P Kriek L Prozesky 《The Onderstepoort journal of veterinary research》1985,52(1):35-42
Diplodiosis, a neuromycotoxicosis, principally of cattle, which is characterized by ataxia, paresis and paralysis, was induced in 13 cattle, 16 sheep and 3 goats, by dosing them with Diplodia maydis [= D. zeae (Schw.) Lév.] cultured on sterilized maize seeds. The results of these experiments confirmed the findings of earlier workers that diplodiosis is a mycotoxicosis caused by D. maydis. The intoxication was induced with cultures of South African isolates of D. maydis obtained from local maize, one of which was associated with a suspected field outbreak, and with cultures of isolates from maize imported from the United States of America and Argentina. Other findings emerging from the experiments were, inter alia, that cultures incubated for less than 8 weeks were seemingly non-toxic, that there was little individual variation in response of cattle to cultures of the different toxic isolates or batches of the isolates, that apparent relapses of clinical signs can occur several weeks after dosing had ceased and that a small percentage of animals can show permanent locomotory disturbance. Light microscopical examination revealed no lesions in acutely affected animals, but an extensive laminar subcortical status spongiosis was evident in the cerebrum and cerebellum of a sheep that had been long paralysed and a steer that had permanent locomotory disturbance. 相似文献
995.
996.
Response of growing-finishing pigs to decreasing floor space allowance and(or) virginiamycin in diet 总被引:1,自引:0,他引:1
R L Moser S G Cornelius J E Pettigrew H E Hanke C D Hagen 《Journal of animal science》1985,61(2):337-342
Five hundred forty crossbred pigs were utilized in four trials (10 replications) at two stations to determine the separate and interacting effects of decreasing floor space allowance with or without the addition of virginiamycin to the diet on performance of growing-finishing pigs. Pigs were allowed .37, .33 or .28 m2/pig during the growing phase (23 to 55 kg) and .74, .66, .56 m2/pig during the finishing phase (55 to 100 kg) and fed either a corn-soybean meal control diet or the control diet plus 11 mg of virginiamycin/kg of diet. Floor space allowances were achieved by varying pen size, so the number of pigs and feeder space per pig were constant for all pens. During the growing phase, daily gain (P less than .01) daily feed intake (P less than .05) and feed conversion ratio (P less than .05) decreased as floor space allowance decreased. During the finishing phase and for the total test period, daily gain (P less than .01) and feed conversion ratio (P less than .05) were reduced but daily feed intake was not affected (P greater than .05) by restricted floor space allowance. The addition of virginiamycin to the diet had no effect on pig performance. The virginiamycin X floor space allowance interaction was not significant, suggesting that pigs fed a diet with or without virginiamycin responded similarly to restricted floor space allowance. The data suggest that the addition of virginiamycin to the diet was ineffective in overcoming the decrease in performance of growing-finishing pigs caused by crowded conditions. 相似文献
997.
Perinatal exposure to atmospheric carbon monoxide at sublethal concentrations affected neonatal piglets negatively. Low total hemoglobin concentration and oxyhemoglobin saturation ratio were present at birth in piglets farrowed by gilts that had been exposed to carbon monoxide at 250 ppm from gestation d 109 on, but stillbirth rate was only 4.8%. Carboxyhemoglobin saturation ratio increased from .0 to 19.8 and 22.4% as carbon monoxide concentration rose from background (less than 5 ppm) to 200 and 250 ppm. Carbon monoxide affected neonatal piglets' behavior. Piglets exposed to atmospheric carbon monoxide at 250 ppm perinatally took longer to nurse for the first time than did counterparts under background or 200-ppm concentrations. Those under carbon monoxide at 250 ppm had compromised performance in behavior tests that measured a piglet's ability to orient itself in, maneuver in and investigate its environment, respectively. 相似文献
998.
Hemorrhage from the cosmetic otoplasty of Doberman Pinschers with von Willebrand's disease 总被引:3,自引:0,他引:3
G S Johnson G T Schlink R K Fallon C P Moore 《American journal of veterinary research》1985,46(6):1335-1340
The hemorrhagic tendencies of 23 Doberman Pinscher pups were observed during cosmetic otoplasty and were ranked by a +1 to +4 grading system (+1 = least hemorrhage, and +4 = most hemorrhage). A second estimate of the hemostatic competencies of these dogs was made by counting the gauze sponges used in the otoplasties. Factor VIII-related antigen concentrations and coagglutinin cofactor concentrations were measured in plasma samples from blood drawn not more than 30 hours before the surgical procedures were done. The factor VIII-related antigen concentrations were between 9% and 147% of the concentration in a normal plasma pool, and the coagglutinin cofactor concentrations were between 1% and 165%, indicating that some of these dogs had von Willebrand's disease. The hemorrhagic tendencies of 12 pups were graded +1. This group had a mean antigen concentration of 75% (min-max, 38% to 147%) and a mean coagglutinin cofactor concentration of 89% (min-max, 42% to 165%). These were significantly greater than the antigen and cofactor concentrations of the grades +2 (n = 5), +3 (n = 3), or +4 (n = 3) dogs. Significant differences were not found when antigen concentrations of the grade +2 dogs (mean, 16%; min-max, 11% to 22%), grade +3 dogs (mean, 13%; 12% to 16%), and grade +4 dogs (mean, 11%; 9% to 12%) were compared with each other, nor were significant differences seen among the coagglutinin cofactor concentrations of the grade +2 dogs (mean, 7%; min-max, 1% to 11%), grade +3 dogs (mean, 6%, 4% to 8%), and grade +4 dogs (mean, 5%; 2% to 9%).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
999.
BCG treatment of periocular sarcoid 总被引:2,自引:0,他引:2
J D Lavach K E Sullins S M Roberts G A Severin C Wheeler D C Lueker 《Equine veterinary journal》1985,17(6):445-448
Twenty-six horses and five mules with periocular sarcoids were treated with intralesional injections of a purified bacillus of Calmette and Guerin (BCG) cell walls in oil suspension. All sarcoids were cured and the horses and mules remained free from recurrence of sarcoid during the two-year follow-up period. 相似文献
1000.
Immune response of poults following intranasal inoculation with Artvax vaccine and a formalin-inactivated Bordetella avium bacterin 总被引:1,自引:0,他引:1
Poults 3 weeks and older developed temporary tracheal resistance to intranasal challenge following inoculation of either Artvax vaccine or formalin-inactivated Bordetella avium bacterin by the intranasal and eyedrop routes. Resistance usually persisted for 3-4 weeks after B. avium challenge. However, with constant exposure to infected controls, the vaccinated birds eventually developed tracheal infection. Day-old poults did not respond to either the Artvax or the bacterin and were completely susceptible to challenge. Two-week-old poults responded to some degree, but poults 3 weeks old and older responded best. Poults inoculated with bacterin by aerosol or by drinking water did not respond as well as those inoculated by the intranasal and eyedrop routes. When poults were given a single subcutaneous injection at 3 weeks of age and challenged 2 weeks later, three of five resisted infection for 18 days. 相似文献