全文获取类型
收费全文 | 3121篇 |
免费 | 222篇 |
国内免费 | 1篇 |
专业分类
林业 | 145篇 |
农学 | 75篇 |
基础科学 | 21篇 |
485篇 | |
综合类 | 549篇 |
农作物 | 99篇 |
水产渔业 | 151篇 |
畜牧兽医 | 1595篇 |
园艺 | 57篇 |
植物保护 | 167篇 |
出版年
2023年 | 22篇 |
2022年 | 20篇 |
2021年 | 52篇 |
2020年 | 76篇 |
2019年 | 86篇 |
2018年 | 68篇 |
2017年 | 62篇 |
2016年 | 93篇 |
2015年 | 64篇 |
2014年 | 86篇 |
2013年 | 127篇 |
2012年 | 163篇 |
2011年 | 219篇 |
2010年 | 104篇 |
2009年 | 80篇 |
2008年 | 160篇 |
2007年 | 149篇 |
2006年 | 135篇 |
2005年 | 152篇 |
2004年 | 142篇 |
2003年 | 127篇 |
2002年 | 133篇 |
2001年 | 67篇 |
2000年 | 59篇 |
1999年 | 35篇 |
1998年 | 28篇 |
1997年 | 38篇 |
1996年 | 27篇 |
1995年 | 21篇 |
1994年 | 22篇 |
1993年 | 22篇 |
1992年 | 31篇 |
1991年 | 29篇 |
1990年 | 31篇 |
1989年 | 49篇 |
1988年 | 40篇 |
1987年 | 41篇 |
1986年 | 39篇 |
1985年 | 24篇 |
1984年 | 20篇 |
1983年 | 25篇 |
1982年 | 18篇 |
1979年 | 20篇 |
1978年 | 18篇 |
1977年 | 18篇 |
1976年 | 18篇 |
1974年 | 18篇 |
1973年 | 19篇 |
1972年 | 23篇 |
1970年 | 18篇 |
排序方式: 共有3344条查询结果,搜索用时 31 毫秒
1.
2.
H M Syme J C Scott-Moncrieff N G Treadwell M F Thompson P W Snyder M R White J W Oliver 《Journal of the American Veterinary Medical Association》2001,219(12):1725-8, 1707-8
An 11-year-old spayed female Labrador Retriever and a 9-year-old castrated male miniature Poodle were evaluated because of clinical signs of hyperadrenocorticism. Cortisol testing did not support a diagnosis of hypercortisolemia in either dog; however, imaging studies revealed unilateral adrenal tumors in both dogs. Serum concentrations of 17-hydroxyprogesterone, progesterone, and estradiol were high in both dogs, and androstenedione concentrations were also high in 1 dog. It is suspected that sex hormone secretion by the adrenal tumors in these dogs resulted in clinical signs of hyperadrenocorticism. Clinical signs and hormonal abnormalities resolved in the male dog after surgical resection of the tumor. There was no improvement in clinical signs after treatment with mitotane in the female dog, which died 2 months after diagnosis. Histologic evaluation confirmed the presence of adrenocortical carcinoma in both dogs. 相似文献
3.
R. N. White 《The Journal of small animal practice》1995,36(4):151-158
The surgical repair of tracheal collapse in 25 dogs is described. The initial presenting signs included coughing, dyspnoea, gagging, retching, exercise intolerance, cyanosis and collapse. Diagnosis was based upon the clinical signs, plain radiography and tracheal endoscopy. The collapse was corrected by the application of a number of extraluminal polypropylene prosthetic rings applied to the affected trachea. Additionally, a left arytenoid lateralisation was also performed. The perioperative complication rate was approximately 4 per cent, while the success rate was 75 per cent. The technique reduces the likelihood of catastrophic postoperative complications associated with iatrogenic laryngeal paralysis which is a possible complication of placement of extraluminal tracheal support devices. 相似文献
4.
Carl D. Webster Kenneth R. Thompson Ann M. Morgan Ebony J. Grisby Siddhartha Dasgupta 《Journal of the World Aquaculture Society》2001,32(1):79-88
Abstract.— In an effort to feed sunshine bass Morone chrysops × M. saxatilis efficiently, promote optimal growth, and reduce labor costs associated with feeding, sunshine bass were grown in cages and fed one of four feeding frequencies: once/d, twice/d, once every other day (I X/EOD), and twice every other day (2X/EOD) for 21 wk. Juvenile sunshine bass were fed a commercial floating diet containing 40% protein and 11.5% lipid. One hundred fish were hand-counted and stocked into each of 12 3.5-m3 cages with three replications per treatment. At the conclusion of the study, percentage weight gain of sunshine bass fed twice/d was significantly (P < 0.05) higher (1,850%) compared to fish fed all other feeding frequencies. Specific growth rate (SGR) of fish fed twice/d was significantly higher (2.1%/d) compared to fish fed all other feeding regimes, while fish fed once/d had a higher SGR (2.0%/d) compared to fish fed I X/EOD (1.6%/d) and 2X/EOD (1.8%/d). Percentage survival was not significantly different (P > 0.05) among all treatments and averaged 70.4%r. Feed conversion ratio (FCR) of fish fed twice/d was significantly higher (2.40) compared to fish fed all other feeding regimes. Percentage fillet weight of fish fed twice/d was significantly higher (27.8%) compared to all other treatments. Percentage moisture, protein, lipid, and ash in fillet were not significantly different among all treatments and averaged 75.7%, 19.4%, 3.5%, and 1.2%n, respectively (wet-weight basis). Based upon data from the present study, it appears that producers growing juvenile sunshine bass in cages may want to feed fish twice daily. This feeding regimen allows for higher growth rates, without adverse effects on body or fillet compositions. However, economic analysis needs to be conducted to determine if feeding twice/d is profitable. 相似文献
5.
R. A. S. White 《The Journal of small animal practice》1989,30(10):543-549
Sixty-two dogs with laryngeal paralysis were presented over a three year period. Presenting clinical signs included inspiratory stridor (100 per cent), exercise intolerance or syncopal episodes (81 per cent), loss or alteration in phonation (48 per cent) and coughing or gagging when eating (29 per cent). Causes of the paralysis were determined as traumatic (two dogs), neoplastic (two dogs), iatrogenic (two dogs), congenital (one dog) and idiopathic (55 dogs). Unilateral arytenoid lateralisation was performed in all dogs. The perioperative complication rate was approximately 10 per cent, while the success rate as judged by owners one year postoperatively was greater than 90 per cent. The technique avoided many of the recorded complications of intralaryngeal surgery. Operative times were short and the requirement for postoperative monitoring was minimal. Increasing familiarity with the technique favourably influenced the incidence of complications and the success rate. 相似文献
6.
7.
The structure of the shell of the egg of Trichuris trichiura was examined using light microscopy as well as scanning and transmission electron microscopy. The results confirmed its three-layered structure and provided evidence that the cores of the polar plugs, which could be seen to be extensions of the shell's middle layer, could be lost en bloc, either mechanically or chemically, and in this way probably provided an exit for the first stage larva at hatching. 相似文献
8.
Marie Engel David W. Hird Tim E. Carpenter Martin Wierup 《Preventive veterinary medicine》1995,24(4):245-252
A cohort of 53 swine seronegative to Aujeszky's disease virus (ADV) was monitored in a 1 year study of a chronically infected commercial Swedish weaner pig producing herd. Serum samples were acquired from all 134 adult swine and analyzed by enzyme-linked immmunosorbent assay (ELISA). Animals testing negative, along with introduced replacement gilts, were followed serologically every second month. Movements of animals were recorded for 319 days and exposure to seropositive animals was calculated for each seronegative pig in the cohort. The accumulated daily pig contact between the 53 ADV-non-infected swine and 43 infected swine was 35 660 days and the median number of days in contact for the non-infected swine with infected was 222. Despite the frequent contact with seropositive pigs, no seronegative animals seroconverted during the first 11 months of observation. Forty-six of 53 pigs seroconverted after a clinical outbreak during the twelfth month of observation. 相似文献
9.
B. Ann Becker 《Veterinary research communications》1987,11(5):443-456
Stress, stressors and the stress response are terms which represent concepts rather than oeing precisely definable. No single theory of stress has been universally accepted. Selye's General Adaptation Syndrome of stress remains the primary theory for the basis of stress research in food-producing animals; however, other concepts and theories have been developed. This paper reviews current theories and suggests that the complexity of research on stress in food-producing animals can be attributed to the lack of concrete theories and concepts regarding identifiable stressors, the endocrine responses stimulated by potential stressors and the complex and integrated biological changes in the neuro-endocrine system resulting from exposure to hypothesized stressors. 相似文献
10.