全文获取类型
收费全文 | 289316篇 |
免费 | 16133篇 |
国内免费 | 722篇 |
专业分类
林业 | 23920篇 |
农学 | 14119篇 |
基础科学 | 2995篇 |
44515篇 | |
综合类 | 37196篇 |
农作物 | 17280篇 |
水产渔业 | 17489篇 |
畜牧兽医 | 117822篇 |
园艺 | 6414篇 |
植物保护 | 24421篇 |
出版年
2020年 | 2903篇 |
2019年 | 3690篇 |
2018年 | 4165篇 |
2017年 | 4515篇 |
2016年 | 4874篇 |
2015年 | 4384篇 |
2014年 | 5776篇 |
2013年 | 16343篇 |
2012年 | 6855篇 |
2011年 | 8945篇 |
2010年 | 7655篇 |
2009年 | 8146篇 |
2008年 | 8425篇 |
2007年 | 7550篇 |
2006年 | 8057篇 |
2005年 | 7229篇 |
2004年 | 7142篇 |
2003年 | 6966篇 |
2002年 | 6279篇 |
2001年 | 7104篇 |
2000年 | 6862篇 |
1999年 | 6223篇 |
1998年 | 4246篇 |
1997年 | 4318篇 |
1996年 | 4002篇 |
1995年 | 4606篇 |
1994年 | 4016篇 |
1993年 | 3752篇 |
1992年 | 5052篇 |
1991年 | 5339篇 |
1990年 | 5072篇 |
1989年 | 5043篇 |
1988年 | 4509篇 |
1987年 | 4617篇 |
1986年 | 4553篇 |
1985年 | 4745篇 |
1984年 | 4225篇 |
1983年 | 4004篇 |
1982年 | 3162篇 |
1981年 | 3057篇 |
1980年 | 2990篇 |
1979年 | 3886篇 |
1978年 | 3323篇 |
1977年 | 3047篇 |
1976年 | 2836篇 |
1974年 | 3282篇 |
1973年 | 3305篇 |
1972年 | 3092篇 |
1971年 | 3028篇 |
1970年 | 2857篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
J E Sagartz D E Swayne K A Eaton J R Hayes K D Amass R Wack L Kramer 《Avian diseases》1992,36(2):282-289
Necrotizing typhlocolitis was diagnosed in 13 juvenile common rheas (Rhea americana) from three separate of geographically isolated Ohio flocks, with mortality ranging from 25% to 80%. At postmortem examination, a diphtheritic membrane covered ulcerated cecal mucosa. Histologically, cecal sections showed necrosis and granulomatous-to-suppurative inflammation that extended into the submucosa and often surrounded large eosinophilic colonies of bacteria. Warthin-Starry staining showed these colonies to be composed of entangled spirochetes that invaded the submucosa and frequently were present transmurally. Similar organisms were identified by Warthin-Starry staining in the cecum of a juvenile rhea from a fourth flock that histologically had mild lymphocytic typhlitis. Scanning and transmission electron microscopy demonstrated the presence of a spirochete in the ceca. Anaerobic culture yielded a gram-negative, beta-hemolytic spirochete. Coccidia, histomonads, and Salmonella spp. were consistently absent. 相似文献
992.
Russell T. Greene Gregory C. Troy 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1995,9(2):86-91
Coccidioidomycosis was diagnosed in 48 cats. Forty-one cases were identified within a period of 3 years. Coccidioides immitis was revealed by cytological or histopathological examinations, or culture in 70% of cats. The remaining 30% of cases were diagnosed by appropriate clinical signs, radiographic lesions, and serological test results. The average age of affected cats was 6.2 years with a median age of 5.0 years. Fifty-four percent (n = 26) were female and 46% (n = 22) were male. Domestic shorthaired and longhaired breeds comprised 89% (n = 41) of affected cats. Sixty-seven percent of cases were diagnosed during the 6-month period of December through May. Cats infected with C immitis were presented for evaluation of dermatologic (56%), respiratory (25%), musculoskeletal (19%), and neurological or ophthalmologic signs (19%). Fever, inappetence, and weight loss were present in 44% of the cats. Duration of clinical signs before diagnosis was less than 4 weeks in 85% (n = 42) of cats, with an average of 3.8 weeks and a median of 2 weeks. Agar gel immunodiffusion tests were positive in all 39 cats tested at sometime during the course of their disease. Hyperproteinemia (greater than 7.9 g/dL) was present in 52% (10/23) of cases. The majority of cats (n = 39) were negative for feline leukemia virus. Antibodies to feline immunodeficiency virus were absent in the 19 cats tested. Ketoconazole was the most common antifungal agent used to treat cats with Coccidioidomycosis. Duration of treatment ranged from less than 1 week to 43 months. Thirty-two cats are currently asymptomatic, with or without treatment. Eleven cats died or were euthanized. Five cats were lost to follow-up. Ketoconazole likely is more suppressive than curative because relapses were common after discontinuing therapy. 相似文献
993.
994.
C. P. Daurio E. N. Cheung A. R. Jeffcoat B. J. Skelly 《Veterinary research communications》1992,16(2):125-130
The bioavailability of three formulations of ivermectin was determined following oral administration to dogs. The average peak plasma level (C
max) of ivermectin administered in the standard tablet formulation at 6 and 100 µg/kg of body weight was 2.97 and 44.31 ng/g, respectively. This suggest dose-dependent pharmacokinetics.C
max and total ivermectin bioavailability, as assessed from the area under the plasma curve (AUC), were similar between two tablet formulations of ivermectin administered at 100 µg/kg. Furthermore,C
max was similar following administration of radiolabelled ivermectin at 6 µg/kg in either a beef-based chewable formulation or in the standard tablet formulation. 相似文献
995.
M Kachani R A Oliver C G Brown H Ouhelli R L Spooner 《Veterinary immunology and immunopathology》1992,34(3-4):221-234
Western blot analysis of Theileria annulata antigens was carried out using sera collected from cattle which had been immunised and challenged with either T. annulata sporozoites or schizont-infected cells. Three antigens between 71 and 73 kDa proved to be common to the three stages of parasite studied: sporozoites, schizonts and piroplasms. An antigen was found at 32 kDa which was specific to T. annulata piroplasms. Results were reproducible using sera from Morocco and the UK. At least one of the proteins at 71-73 kDa, but not that at 32 kDa were also recognised by sera from animals infected with Babesia species. 相似文献
996.
997.
998.
S E Palmer 《Journal of the American Veterinary Medical Association》1989,195(8):1125-1127
A verrucous sarcoid was removed from the ear of a horse, using a carbon dioxide laser. The use of carbon dioxide laser excision and ablation enabled complete removal of tumor cells, with minimal damage to underlying normal cartilage. Cosmetic healing was observed with minimal disfigurement. Recurrence of the tumor was not observed after 11 months. 相似文献
999.
1000.
Pulmonary responses to intratracheal challenge exposure with Pasteurella haemolytica, with or without Escherichia coli-derived endotoxin, E coli endotoxin alone, or saline solution were compared in anesthetized, mechanically ventilated neonatal calves. Baseline values for dynamic compliance, total pulmonary resistance, functional residual capacity, arterial blood gas tensions, hemogram, leukogram, and systemic and pulmonary arterial pressures were recorded for each calf. After baseline data were obtained, calves were challenge exposed with logarithmic-growth phase P haemolytica organisms with or without E coli endotoxin, E coli endotoxin alone, or saline solution (0.9% NaCl). Physiologic data were obtained immediately after challenge exposure and at various intervals over the next 6 hours. Calves challenge exposed with P haemolytica alone developed sever hypoxemia, had increased alveolar-arterial oxygen difference and threefold increases in total pulmonary resistance, became hypercarbic, had decreased functional residual capacity, and developed systemic hypotension without change in pulmonary arterial pressure. At necropsy, these calves had extensive multifocal areas of necrohemorrhagic and purulent pneumonia. Ratio of extravascular lung water to lung dry weight was not significantly increased in lung specimens obtained from calves challenge exposed with P haemolytica, but ratio of lung wet weight to dry weight was increased, indicating that increased lung wet weight was attributable largely to increased solids and not to fluid alone. (Extravascular lung water measurement excludes fluid from the vascular compartment.) Intratracheal challenge exposure with endotoxin failed to alter lung function and caused minor changes in lung structure consisting of focal areas of hemorrhage and edema.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献