全文获取类型
收费全文 | 322444篇 |
免费 | 17821篇 |
国内免费 | 1268篇 |
专业分类
林业 | 24798篇 |
农学 | 14558篇 |
基础科学 | 3247篇 |
47663篇 | |
综合类 | 45283篇 |
农作物 | 17528篇 |
水产渔业 | 18181篇 |
畜牧兽医 | 137314篇 |
园艺 | 6804篇 |
植物保护 | 26157篇 |
出版年
2019年 | 3898篇 |
2018年 | 4454篇 |
2017年 | 4963篇 |
2016年 | 5170篇 |
2015年 | 4706篇 |
2014年 | 6015篇 |
2013年 | 16775篇 |
2012年 | 8452篇 |
2011年 | 10905篇 |
2010年 | 8419篇 |
2009年 | 8706篇 |
2008年 | 9975篇 |
2007年 | 9165篇 |
2006年 | 9539篇 |
2005年 | 8777篇 |
2004年 | 8463篇 |
2003年 | 8190篇 |
2002年 | 7619篇 |
2001年 | 8452篇 |
2000年 | 8176篇 |
1999年 | 7153篇 |
1998年 | 4402篇 |
1997年 | 4425篇 |
1996年 | 4172篇 |
1995年 | 4791篇 |
1994年 | 4275篇 |
1993年 | 3950篇 |
1992年 | 5840篇 |
1991年 | 6193篇 |
1990年 | 6022篇 |
1989年 | 5933篇 |
1988年 | 5375篇 |
1987年 | 5484篇 |
1986年 | 5537篇 |
1985年 | 5521篇 |
1984年 | 4989篇 |
1983年 | 4547篇 |
1982年 | 3531篇 |
1981年 | 3349篇 |
1980年 | 3283篇 |
1979年 | 4417篇 |
1978年 | 3838篇 |
1977年 | 3415篇 |
1976年 | 3202篇 |
1975年 | 3138篇 |
1974年 | 3797篇 |
1973年 | 3760篇 |
1972年 | 3507篇 |
1971年 | 3355篇 |
1970年 | 3196篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
871.
David Lipsitz DVM Robin E. Levitski DVM Wayne L. Berry BVSc MMedVet 《Veterinary radiology & ultrasound》2001,42(1):14-19
Three dogs with multilobular osteochondrosarcoma of the skull were evaluated using magnetic resonance (MR) imaging. Spin echo T1, T2, proton weighted and post contrast T1W images were obtained with a 1.5 Tesla magnet. The MR imaging findings were similar in all three dogs with mixed signal intensities in the T1W, T2W and proton weighted images and fairly large areas of contrast enhancement in the post contrast T1W images. The extent of brain and soft tissue involvement were well delineated and provided useful information concerning surgical planning. MR imaging provided a useful method of evaluating dogs with skull tumors. 相似文献
872.
Immunohistochemical detection of scrapie prion proteins in clinically normal sheep in Pennsylvania. 总被引:2,自引:0,他引:2
H Kim K I O'Rourke M Walter H G Purchase J Enck T K Shin 《Journal of veterinary diagnostic investigation》2001,13(1):89-91
Following diagnosis of scrapie in a clinically suspect Suffolk sheep, 7 clinically normal flockmates were purchased by the Pennsylvania Department of Agriculture to determine their scrapie status using an immunohistochemical procedure. Two of the 7 euthanized healthy sheep had positive immunohistochemical staining of the prion protein of scrapie (PrP-Sc) in their brains, nictitating membranes, and tonsils. The PrP-Sc was localized in the areas of the brain where, histopathologically, there was neurodegeneration and astrocytosis. The PrP-Sc occurred within germinal centers of the affected nictitating membranes and tonsils and was located in the cytoplasm of the dendrite-like cells, lymphoid cells, and macrophages. These results confirm that immunohistochemical examination of the nictitating membrane can be used as a screen for the presence of scrapie infection in clinically normal sheep at a capable veterinary diagnostic laboratory. In sheep with a PrP-Sc-positive nictitating membrane, the diagnosis of scrapie should be confirmed by histopathology and immunohistochemical examination of the brain following necropsy. Following full validation, immunohistochemistry assays for detection of PrP-Sc in nictitating membrane lymphoid tissues can improve the effectiveness of the scrapie control and eradication program by allowing diagnosis of the disease in sheep before the appearance of clinical signs. 相似文献
873.
J Sherrill T Schock J L Dunn D J St Aubin V V Burnley S E Poet 《Journal of zoo and wildlife medicine》2001,32(1):17-24
Humoral immune responses of black-footed penguins (Spheniscus demersus) to DNA-mediated immunization with a beta-galactosidase reporter gene expression plasmid were evaluated. Six male and 6 female adult penguins received either test plasmid, pCMV-beta, containing the beta-galactosidase gene or control plasmid, pCI, lacking a gene for expression. Three birds from each group were used previously in a diluent control group and given one injection of sterile saline. All samples were screened for anti-beta-galactosidase antibodies by indirect enzyme-linked immunosorbent assay with anti-chicken immunoglobulin G as secondary antibody. Antibodies to beta-galactosidase were detected in the sera of pCMV-beta-inoculated penguins, with a peak response on day 21. Antibody titers of the test plasmid group versus both control groups on days 21, 28, and 42 differed significantly. These results demonstrate that black-footed penguins can be safely transfected with the gene encoding beta-galactosidase and will mount a humoral response against the in vivo-expressed protein. Knowledge from this initial study can be applied to the development of DNA-mediated vaccines against specific infectious diseases of penguins. 相似文献
874.
D. Sharifi J. Singh P.K. Peshin A.P. Singh 《Veterinary anaesthesia and analgesia》1991,18(Z1):309-314
Cardio pulmonary embarrassment was induced with thiopentone sodium in 35 healthy adult donkeys divided in to seven groups of five animals. “To effect” anaesthetic dose was (12.72 ± 0.69 mg/kg) which caused transient hypotension, tachycardia and hypoxemia. A stable fall in MAP 1. 6.77 ± 0.287 Kpa (50.78 ± 2.15 mmHg) and a flat EEG were considered to indicate acute circulatory insufficiency due to thiopentone overdose. 相似文献
875.
876.
877.
A.E. Wanger DVM MS W.W. Muir III DVM Phd R.M. Bednaraki DVM MS 《Journal of Veterinary Emergency and Critical Care》1991,1(1):14-18
The purpose of this study was to determine whether lingual vanous blood gas samples reflect arterial acid-base gas status in anethetized dogs. Heparinized blood samples were drawn simultaneously from the lingual vein and a peripheral artery in 50 anestheized dogs that were clinical surgical patients, as well as from four experimental dogs in which hemorrahaic shock was being studied. Blood pH, oxygen tension (PO2 ), and bicarbonate (HCO3- )) from the two sources in clinical patients showed significant liner correlation, although arterial PO2 )(PaO2 )) tended to be approximately 110mm Hg higher than lingual venous PO2 ). During hemorrahgic shock, however, PaO2 ) and PaCO2 ) were significantly different from lingual venous PO2 ) and PCO2 ), Lingula venous blood gas analysis may be useful in assessing acid-base and blood gas status in routline cases, but should not be relied upon in dogs with low cardiac output or poor perfusion. 相似文献
878.
C. P. Verschueren P. J. Selman J. J. M. de Vijlder J. A. Mol 《Domestic animal endocrinology》1991,8(4):509-519
Canine thyroglobulin (cTg) has been isolated and purified. It has similar electrophoretic patterns as Tg from other mammalian species. The main fraction had a MW of 660,000, whereas also fractions of a MW of approximately 1,300,000 (dimer) and 330,000 (subunit) were present. The iodine content was 0.8 to 1.0 % (w/w). cTg did not cross-react with antibodies against human Tg to a degree that would allow the use of a radioimmunoassay for human Tg for the determination of cTg in serum or plasma. Therefore a polyclonal antiserum was raised against cTg and a homologous radioimmunoassay was developed, which was sensitive (0.4 μg/l) and specific (cross-reactivity in cTg assay of human Tg, goat Tg, T4, T3, and DIT < 0.01 %).
Plasma Tg levels in normal dogs of both sexes and aged 3–15 years amounted to 192 ± 73 μg/l (mean ± SD, n=30). There was no relation between plasma Tg and T4 levels. 相似文献
879.
880.
Ⅱ型猪环状病毒 (PCV2 )现已被证明是断奶后全身消耗性综合征 (PMWS)的致病因子 ,这一综合征是一种可造成世界各地严重经济损失的猪病。最近的研究还证实此病毒与加拿大和欧洲猪群的繁殖障碍有关。但是 ,绝大多数PCV2感染都是亚临床性的。刺激仔猪免疫系统是感染此病毒后产生临床疾病的重要因子吗 ? 相似文献