全文获取类型
收费全文 | 289636篇 |
免费 | 16131篇 |
国内免费 | 732篇 |
专业分类
林业 | 23922篇 |
农学 | 14128篇 |
基础科学 | 2996篇 |
44588篇 | |
综合类 | 37195篇 |
农作物 | 17356篇 |
水产渔业 | 17504篇 |
畜牧兽医 | 117980篇 |
园艺 | 6416篇 |
植物保护 | 24414篇 |
出版年
2020年 | 2905篇 |
2019年 | 3690篇 |
2018年 | 4168篇 |
2017年 | 4517篇 |
2016年 | 4877篇 |
2015年 | 4388篇 |
2014年 | 5777篇 |
2013年 | 16355篇 |
2012年 | 6859篇 |
2011年 | 8951篇 |
2010年 | 7656篇 |
2009年 | 8150篇 |
2008年 | 8428篇 |
2007年 | 7560篇 |
2006年 | 8073篇 |
2005年 | 7240篇 |
2004年 | 7159篇 |
2003年 | 6977篇 |
2002年 | 6285篇 |
2001年 | 7113篇 |
2000年 | 6863篇 |
1999年 | 6227篇 |
1998年 | 4247篇 |
1997年 | 4319篇 |
1996年 | 4002篇 |
1995年 | 4607篇 |
1994年 | 4016篇 |
1993年 | 3753篇 |
1992年 | 5055篇 |
1991年 | 5341篇 |
1990年 | 5072篇 |
1989年 | 5046篇 |
1988年 | 4510篇 |
1987年 | 4617篇 |
1986年 | 4553篇 |
1985年 | 4744篇 |
1984年 | 4223篇 |
1983年 | 4005篇 |
1982年 | 3163篇 |
1981年 | 3058篇 |
1980年 | 2990篇 |
1979年 | 3885篇 |
1978年 | 3328篇 |
1977年 | 3049篇 |
1976年 | 2836篇 |
1974年 | 3284篇 |
1973年 | 3314篇 |
1972年 | 3093篇 |
1971年 | 3028篇 |
1970年 | 2858篇 |
排序方式: 共有10000条查询结果,搜索用时 953 毫秒
981.
The severity of charcoal root disease of conifer seedlings (Abies concolor, A. magnified, Pinus jeffreyi, P. lambertiana, and Pseudotsuga menziesii) was a power function of the sclerotial density of the fungus (Macrophomina phaseolina) in nursery soil. 相似文献
982.
One hundred two fecal specimens from psittacine birds submitted to Veterinary Laboratory Services of the California Department of Food and Agriculture at Petaluma were screened for Chlamydia psittaci by a direct immunofluorescence assay using a fluorescein-labeled monoclonal antibody conjugate specific for Chlamydia sp. Results were compared with those obtained by isolation of chlamydia in cultures of McCoy mouse cells. The relative specificity of the direct fluorescent antibody test on fecal smears was 98.9% and the relative sensitivity was 62.5%. The results of this study suggested that the direct fluorescent antibody test was highly specific, and it proved to be a useful same-day antemortem diagnostic test for birds with symptomatic chlamydial infection. The use of centrifugation in the cell culture assay was found to significantly enhance the level of chlamydial infection in cell culture. 相似文献
983.
Ariana M.P. Nap Yvonne W.E.A. Pollak Walter E. van den Brom Ad Rijnberk DVM PhD 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1994,8(4):302-303
Thyroidal 99m TcO4 (pertechnetate) uptake percentages were determined in unanesthetized euthyroid (n = 13) and hyperthyroid (n = 18) cats. Maximal uptakes were observed 60 minutes after IV injection of the radionuclide and ranged from 0.3 to 3.9% of the dose in euthyroid cats (median 2.23%) and from 5.2% to 23.9% of the dose in hyperthyroid cats (median 14.8%) ( P < .05). There were no overlaps in pertechnetate uptake percentages during any of the intervals evaluated. It is concluded that the optimal time for visualization of the thyroid by 99m TcO4 -scanning is 60 minutes after IV injection of the radionuclide. Calculation of the percentage uptake is of additional diagnostic value. 相似文献
984.
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
985.
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
986.
987.
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
988.
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
989.
990.