全文获取类型
收费全文 | 90420篇 |
免费 | 5554篇 |
国内免费 | 47篇 |
专业分类
林业 | 3755篇 |
农学 | 3473篇 |
基础科学 | 637篇 |
11325篇 | |
综合类 | 13706篇 |
农作物 | 3406篇 |
水产渔业 | 4951篇 |
畜牧兽医 | 47927篇 |
园艺 | 1182篇 |
植物保护 | 5659篇 |
出版年
2020年 | 735篇 |
2019年 | 954篇 |
2018年 | 1587篇 |
2017年 | 1852篇 |
2016年 | 1668篇 |
2015年 | 1412篇 |
2014年 | 1726篇 |
2013年 | 3748篇 |
2012年 | 2948篇 |
2011年 | 3604篇 |
2010年 | 2361篇 |
2009年 | 2336篇 |
2008年 | 3502篇 |
2007年 | 3222篇 |
2006年 | 3159篇 |
2005年 | 2698篇 |
2004年 | 2608篇 |
2003年 | 2622篇 |
2002年 | 2411篇 |
2001年 | 3400篇 |
2000年 | 3312篇 |
1999年 | 2565篇 |
1998年 | 991篇 |
1997年 | 1053篇 |
1996年 | 885篇 |
1995年 | 1027篇 |
1994年 | 896篇 |
1993年 | 900篇 |
1992年 | 1856篇 |
1991年 | 1934篇 |
1990年 | 1863篇 |
1989年 | 1873篇 |
1988年 | 1614篇 |
1987年 | 1607篇 |
1986年 | 1637篇 |
1985年 | 1534篇 |
1984年 | 1232篇 |
1983年 | 1042篇 |
1982年 | 721篇 |
1979年 | 1067篇 |
1978年 | 821篇 |
1975年 | 823篇 |
1974年 | 904篇 |
1973年 | 877篇 |
1972年 | 811篇 |
1971年 | 803篇 |
1970年 | 807篇 |
1969年 | 789篇 |
1968年 | 714篇 |
1967年 | 742篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
K. J. EASLEY DVM MS T. S. STASHAK DVM MS DiplomateACVS F. W. SMITH PhD G. VAN SLYKE BVSC 《Veterinary surgery : VS》1990,19(2):102-106
Thirty-six superficial digital flexor tendons from nine fresh equine cadavers were transected and sutured with size 2 monofilament nylon. Nine tendons were repaired with each of four suture patterns: single-locking loop, double-locking loop, triple-locking loop, or three-loop pulley. The times required for application, tensile strengths, resistance to distraction (gap), and modes of failure were analyzed. The mean times required were: single-locking loop, 3 mins, 15 secs; double-locking loop, 4 mins, 15 secs; triple-locking loop, 10 mins, 50 secs; and three-loop pulley, 4 mins. The double-locking loop, triple-locking loop, and three-loop pulley suture patterns were stronger than the single-locking loop. The triple-locking loop and three-loop pulley patterns were close in strength and only the triple-locking loop was stronger than the double-locking loop. The three-loop pulley had the greatest resistance to gap formation and its mode of failure was different from the others. The three-locking loop suture patterns failed by suture breakage but the three-loop pulley failed first by suture pull-out and then by suture breakage. 相似文献
992.
A grading system for lymphocytic plasmacytic colitis in dogs 总被引:1,自引:0,他引:1
L Roth A M Walton M S Leib C F Burrows 《Journal of veterinary diagnostic investigation》1990,2(4):257-262
Colonic mucosal samples were obtained every 4 weeks for 13 months from 6 clinically normal dogs and from 47 dogs with a clinical diagnosis of chronic inflammatory bowel disease. All samples were graded on a scale of 0-5, based upon the quantity of lymphocytes and plasma cells in the lamina propria, epithelial changes, and the presence of ulcers and erosions. A grade of less than or equal to 2.0 was considered normal and was assigned to 77 of 78 samples from clinically normal dogs and 28 of 48 samples from dogs with diarrhea. A transient increase in cellularity was noted in 1 sample from 1 control dog. Nineteen dogs with clinical disease had obvious histologic abnormalities. The grading scheme described provides the pathologist with an objective criterion for the microscopic evaluation of colonic mucosal samples obtained by endoscopic techniques and offers clinicians a method of assessing the dog's progress and response to therapy. 相似文献
993.
994.
J W Tyler J S Cullor M C Thurmond V L Douglas K M Parker 《American journal of veterinary research》1990,51(9):1400-1406
Logistic regression was used to develop models predicting preweaning survival in 334 neonatal swine. Measured risk factors included birth weight, litter size (live born), dam parity, serum IgG concentration, serum ELISA titers recognizing common gram-negative core antigens, and serum concentrations of the third component of complement. Larger birth weights were associated with increased probability of preweaning survival. The highest mortality was observed in litters with more than 12 pigs. Pigs with serum concentration of the third component of complement (C3) in the lowest stratum, less than 20% adult pooled C3 standard (APC3), had reduced mortality, compared with high (greater than 38% APC3) and middle (20 to 38% APC3) groups. Associations between all other variables, including total serum IgG concentration and preweaning survival were not significant. Few pigs had hypogammaglobulinemia, less than 3% of the study population had serum IgG concentrations less than 1 g/dl. Of all measured variables, only birth weight and dam parity were significant predictors of preweaning gain. Larger pigs and pigs born to third or greater parity dams had more preweaning gain than other pigs. 相似文献
995.
To determine whether prolactin has luteolytic properties during the first part of the luteal period, hysterectomy was performed in four dogs, in which prolactin had been chronically suppressed by bromocriptine administration. The concentration of progesterone in the peripheral blood decreased upon hysterectomy during the first part of the luteal phase and regained normal values after about seven days. The progesterone patterns during the perisurgical period in these dogs were similar to those patterns observed in dogs hysterectomised without bromocriptine treatment. It is concluded therefore that, in the dog, luteolytic properties can not be attributed to prolactin. 相似文献
996.
The effects of feeding milk to diarrheic calves supplemented with oral electrolytes. 总被引:1,自引:3,他引:1 下载免费PDF全文
S E Heath J M Naylor B L Guedo L Petrie C G Rousseaux O M Radostits 《Canadian journal of veterinary research》1989,53(4):477-485
The effects of feeding different levels of milk to diarrheic calves (n = 19) supplemented with oral electrolytes were investigated. In the early stages of the disease the calves were fed either enough milk to maintain normal growth in a healthy calf, one half that volume or no milk. The three groups were further subdivided according to whether or not the electrolyte solution contained bicarbonate. A full milk ration allowed uninterrupted weight gains of 1% body weight/day (p = 0.003), but caused greater inappetence (p = 0.003 to 0.037) at the beginning of the trial than lower levels of milk intake. Electrolyte solutions with bicarbonate reduced growth rates in milk fed calves (p = 0.014). The density of fat stores increased with the level of milk feeding (p = 0.04 to 0.053). The mitotic index of the duodenal mucosa increased with milk feeding (p = 0.08), indicating a superior mucosal regeneration potential. Thymic atrophy was pronounced in those calves fed no milk (p = 0.001). It was concluded that the continued feeding of milk to diarrheic calves was beneficial. Electrolyte solutions containing bicarbonate should be avoided when milk is fed to diarrheic calves. 相似文献
997.
998.
Ko JC Payton ME White AG Galloway DS Inoue T 《Journal of the American Animal Hospital Association》2006,42(1):18-27
This crossover study tested the hypothesis that both diazepam and microdose medetomidine would comparably reduce the amount of propofol required to induce sedation. Four different medications, namely high-dose diazepam (0.4 mg/kg intravenously [IV]), low-dose diazepam (0.2 mg/kg IV), medetomidine (1 mug/kg IV), and placebo (0.5 mL physiological saline IV) were followed by propofol (8 mg/kg IV) titrated to a point where intubation could be performed. The effects of medetomidine were comparable to the effects of high-dose diazepam and significantly better than the effects of low-dose diazepam or placebo. Dogs in all treatment groups had transient hypoxemia, and induction and recovery qualities were similar. 相似文献
999.
Watery mouth was diagnosed as the cause of illness and subsequent death in a 3-day-old Romney lamb which had not received early colostrum. The history, clinical signs and post-mortem findings were typical of the disease as seen in other countries, including Great Britain. The diagnosis was based on the clinical signs and was supported by an absence of post-mortem findings of other specific neonatal diseases. The potential importance of watery mouth under conditions of intensive husbandry in New Zealand is discussed. 相似文献
1000.