全文获取类型
收费全文 | 188561篇 |
免费 | 10070篇 |
国内免费 | 120篇 |
专业分类
林业 | 8456篇 |
农学 | 6191篇 |
基础科学 | 1131篇 |
22881篇 | |
综合类 | 31088篇 |
农作物 | 7235篇 |
水产渔业 | 9356篇 |
畜牧兽医 | 97854篇 |
园艺 | 2458篇 |
植物保护 | 12101篇 |
出版年
2019年 | 1689篇 |
2018年 | 2706篇 |
2017年 | 2960篇 |
2016年 | 2776篇 |
2015年 | 2423篇 |
2014年 | 2993篇 |
2013年 | 7426篇 |
2012年 | 5287篇 |
2011年 | 6364篇 |
2010年 | 4314篇 |
2009年 | 4289篇 |
2008年 | 6316篇 |
2007年 | 6211篇 |
2006年 | 5784篇 |
2005年 | 5341篇 |
2004年 | 5184篇 |
2003年 | 5249篇 |
2002年 | 4851篇 |
2001年 | 6023篇 |
2000年 | 5936篇 |
1999年 | 4846篇 |
1998年 | 1909篇 |
1997年 | 1905篇 |
1996年 | 1749篇 |
1995年 | 2148篇 |
1994年 | 1764篇 |
1993年 | 1821篇 |
1992年 | 3734篇 |
1991年 | 3909篇 |
1990年 | 3981篇 |
1989年 | 3953篇 |
1988年 | 3662篇 |
1987年 | 3613篇 |
1986年 | 3592篇 |
1985年 | 3479篇 |
1984年 | 2844篇 |
1983年 | 2546篇 |
1982年 | 1742篇 |
1979年 | 2592篇 |
1978年 | 2055篇 |
1977年 | 1789篇 |
1976年 | 1737篇 |
1975年 | 1897篇 |
1974年 | 2296篇 |
1973年 | 2404篇 |
1972年 | 2365篇 |
1971年 | 2148篇 |
1970年 | 2136篇 |
1969年 | 1947篇 |
1967年 | 1740篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
E M Poffenbarger D A Feeney 《Journal of the American Veterinary Medical Association》1986,189(1):90-95
Gray-scale ultrasonography was utilized in addition to radiography in the diagnosis of reproductive disease in 18 bitches. In 72% of the cases, ultrasonography was considered diagnostic because it revealed information on organ architecture, relationships of radiographically silhouetting soft tissue structures, and fetal viability that was unobtainable by radiography alone. In the remainder of the cases, ultrasonography was contributory to the diagnostic process by supporting the clinical and radiographic diagnoses. The benefits of ultrasonography are discussed, as is the ultrasonographic appearance of a variety of reproductive tract diseases. 相似文献
992.
T Mattila J Syv?j?rvi N E Jensen M Sandholm 《American journal of veterinary research》1986,47(1):139-142
Interrelationships between N-acetyl-beta-D-glucosaminidase (indicating cellular damage) and antitrypsin (indicating increased permeability between the blood and milk compartments) were evaluated in 1,411 quarter-milk samples collected during routine herd surveys. N-Acetyl-beta-D-glucosaminidase was antitrypsin, whereas, in more severe mastitis, antitrypsin had a more constant deflection. The sensitivity of both determinants was associated with the virulence of bacteria. Production of bacterial hemolytic toxins was associated with a significant increase in both determinants. Penicillinase production by staphylococci was associated with selective increases of antitrypsin. 相似文献
993.
A Y-maze avoid-avoid choice test was used to elucidate pregnant ewes' relative preference for electro-immobilization as opposed to restraint by a squeeze-tilt table. Choices in successive trials evaluating three commercial electro-immobilizers were: electro-immobilizer-13, 13 and 8% for respective models; squeeze-tilt table-79, 57 and 71%; and no choice-8, 30 and 21%. In all trials combined, 56% of the ewes never chose the electro-immobilizer after once experiencing it, while 94% did choose the squeeze-tilt table one or more times after being restrained by it. Most ewes became more willing to enter the table as experience with it increased, but those that had been both electro-immobilized and table-restrained became more hesitant to pass the test facility's entrance gate as these experiences increased. Ewes accepted a feed reward only reluctantly if at all after being electro-immobilized, but readily after table restraint. Electro-immobilization was clearly more aversive to the ewes than was restraint by a squeeze/tilt table. When restraint by either electro-immobilization or squeeze/tilt table is necessary, use of the table would be indicated in terms of its being less aversive. 相似文献
994.
M Jacques M E Olson A M Crichlow A D Osborne J W Costerton 《Canadian journal of veterinary research》1986,50(2):272-274
Microorganisms associated with the vagina, cervix and uterus of rabbits were isolated and identified. The predominant microorganisms isolated from the vaginas and cervices were coagulase-negative staphylococci, micrococci, and nonfermentative bacilli. Coagulase-negative staphylococci were isolated frequently, but in small numbers, from the uteri. The pH of the rabbit vagina was found to be near neutrality. Our data indicate that the genital flora of female rabbits is relatively simple, regarding the number and type of microorganisms. 相似文献
995.
996.
The effect of inhibiting the rise in cortisol concentrations that occurs at copulation upon luteinizing hormone release was studied in seven adult boars. Plasma samples were collected for assay of luteinizing hormone, testosterone and cortisol on a control day and before, during and after exposure to an estrous sow. The area under the curve was used to evaluate hormone production and treatment effects were evaluated by a paired Student's t-test. The 11 beta-hydroxylase inhibitor, metyrapone, was used to suppress glucocorticoid hormone production. Cortisol concentrations increased significantly (p less than 0.05) after breeding compared to values on the control day while treatment with metyrapone prior to breeding prevented the cortisol increase (p greater than 0.05). Although luteinizing hormone production increased significantly after copulation in both breeding experiments, metyrapone pretreatment resulted in a reduction of luteinizing hormone secretion (p less than 0.05). Testosterone production was also reduced in boars pretreated with metyrapone. The results suggest that the increased levels of cortisol occurring at copulation may enhance luteinizing hormone release in boars. 相似文献
997.
An abnormal mesocolic attachment which resulted in a stellate malformation of the left colon adjacent to the pelvic flexure was suspected to be the cause of intermittent episodes of colic in a horse. Resection and side-to-side anastomosis of the large colon at the level of the sternal and diaphragmatic flexures was performed and the horse made an uneventful recovery from surgery. Only minor serum biochemical changes were observed in the initial postoperative period. The abnormal mesocolic attachment was probably a congenital anomaly. 相似文献
998.
999.
1000.
In a series of 61 dogs examined for perineal hernia 12, (20 per cent) were found to have bladder retroflexion. Associated urinary signs were seen in only five dogs including one case with bladder rupture. Radiology was found to be the most consistently accurate means of diagnosis. Bladders were drained by catheterization, or by percutaneous or surgical cystocentesis before manipulative or surgical reduction. Conventional herniorrhaphy and castration were performed in all cases. Cystopexy was performed in only one case although recurrence of the retroflexion was not encountered in any dogs. Three dogs remained urinary incontinent after treatment. 相似文献