全文获取类型
收费全文 | 220529篇 |
免费 | 11848篇 |
国内免费 | 148篇 |
专业分类
林业 | 9274篇 |
农学 | 7287篇 |
基础科学 | 1387篇 |
28517篇 | |
综合类 | 34962篇 |
农作物 | 8643篇 |
水产渔业 | 11288篇 |
畜牧兽医 | 113430篇 |
园艺 | 3043篇 |
植物保护 | 14694篇 |
出版年
2020年 | 1874篇 |
2019年 | 2240篇 |
2018年 | 3261篇 |
2017年 | 3705篇 |
2016年 | 3402篇 |
2015年 | 2937篇 |
2014年 | 3690篇 |
2013年 | 8941篇 |
2012年 | 6615篇 |
2011年 | 8136篇 |
2010年 | 5401篇 |
2009年 | 5455篇 |
2008年 | 8006篇 |
2007年 | 7664篇 |
2006年 | 7172篇 |
2005年 | 6616篇 |
2004年 | 6346篇 |
2003年 | 6494篇 |
2002年 | 5959篇 |
2001年 | 7005篇 |
2000年 | 6973篇 |
1999年 | 5646篇 |
1998年 | 2388篇 |
1997年 | 2323篇 |
1996年 | 2164篇 |
1995年 | 2586篇 |
1994年 | 2241篇 |
1993年 | 2168篇 |
1992年 | 4362篇 |
1991年 | 4601篇 |
1990年 | 4551篇 |
1989年 | 4556篇 |
1988年 | 4166篇 |
1987年 | 4144篇 |
1986年 | 4195篇 |
1985年 | 3995篇 |
1984年 | 3249篇 |
1983年 | 2904篇 |
1982年 | 1986篇 |
1979年 | 2926篇 |
1978年 | 2339篇 |
1977年 | 1974篇 |
1976年 | 1983篇 |
1975年 | 2096篇 |
1974年 | 2487篇 |
1973年 | 2560篇 |
1972年 | 2441篇 |
1971年 | 2191篇 |
1970年 | 2222篇 |
1969年 | 2135篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
241.
The administration of 20 mg/kg of acetylsalicylic acid in 18 clinically healthy dogs resulted in a thrombocytopathy with lengthened capillary bleeding time and irreversible aggregation inhibition. Through the set up of individual dilution series, one could conclude the proportional percentage of aggregation functional transfused thrombocytes. The capillary bleeding time was shortened after the intravenous injection of prednisolone (5 mg/kg) without measurable influence on the thrombocytes. Compared to the singular use of cortisone or blood transfusion alone, the effect on capillary bleeding time became magnified when one combined transfusion and corticosteroids. The fresh blood conserves (12 hours) were, with respect to the haemostyptical properties, superior to blood stored for 5 days. The component of aggregation-functional thrombocytes was, due to the prophylactic cortisone application prior to transfusion, not increased. 相似文献
242.
Heat production, which accounts for 0.6 of gross energy intake, is insufficiently represented in predictions of food intake. Especially when heat production is elevated (for example by lower temperature or poor feathering) the classical predictions based on body weight, body-weight change and egg mass are inadequate. Heat production was reliably estimated as [35.5-environmental temperature (degree C)] x [Defeathering (=%IBPW) + 21]. Including this term (PHP: predicted heat production) in equations predicting food intake significantly increased accuracy of prediction, especially under suboptimal conditions. Within the range of body weights tested (from 1.6 kg in brown layers to 2.8 kg in dwarf broiler breeders), body weight as an independent variable contributed little to the prediction of food intake; especially within strains its effect was better included in the intercept. Significantly reduced absolute values of residual food consumption were obtained over a wide range of conditions by using predictions of food intake based on body-weight change, egg mass, predicted heat production (PHP) and an intercept, instead of body weight, body-weight change, egg mass and an intercept. 相似文献
243.
Calicivirus was isolated from the joint of a kitten that had pyrexia, upper respiratory tract disease, and severe shifting-limb lameness. Marked mononuclear inflammation was found in the synovial fluid. Calicivirus infection or live-virus vaccination previously had been associated with arthropathy, but virus had not been recovered from affected joints. Calicivirus infection should be considered as a diagnosis in kittens with fever and arthralgia, especially if there is a history of recent vaccination or upper respiratory tract disease. Lameness associated with calicivirus infection may be severe, but appears to be self-limiting and is associated with an excellent prognosis for recovery. 相似文献
244.
D E Granstrom R K Ridley Y Baoan L J Gershwin P M Nesbitt L A Wempe 《American journal of veterinary research》1989,50(4):571-574
Eight bovine hearts with lesions of eosinophilic myositis (EM) and 2 bovine hearts without EM lesions were collected at slaughter. Blood samples from these 10 hearts, and the heart of a newborn calf also were collected. Histologically, Sarcocystis cruzi was identified in the 8 hearts with EM lesions and the 2 hearts without EM lesions, but not in the heart of the newborn calf. Serum was harvested from the 10 blood samples and was used in homologous, modified, passive cutaneous anaphylaxis tests. Antigen was prepared from S cruzi bradyzoites isolated from the 2 hearts without EM lesions. Serum samples from the 8 cattle with EM lesions reacted positively to S cruzi antigen. When heat-inactivated IgE in serum (56 C for 4 hours) was used, all passive cutaneous anaphylaxis responses were considered negative. Using ELISA, serum IgE concentrations from the 10 cattle with and without EM lesions were 2.2 to 9 U/ml. As determined by radial immunodiffusion, IgM concentrations were 80 to 215 mg/dl. Immunoglobulin G concentrations were 420 to 2,050 mg/dl, but most were less than or equal to 1,700 mg/dl. Immunoglobulin A concentrations were 0 to 62 mg/dl; 1 steer with EM lesions had 0 mg/dl. Double-gel immunodiffusion confirmed the presence of Sarcocystis-specific precipitating antibodies. Sera from the 10 cattle with and without EM lesions formed at least 1 precipitin band. 相似文献
245.
246.
In a flock of sheep to which food with excess copper (= Cu) had been fed for some months 39 animals died of chronic copper toxicosis. In 5 sheep of this flock the plasma concentrations of the enzymes glutamate dehydrogenase (GLDH), sorbitol dehydrogenase (SDH), aspartate-amino-transferase (ASAT) and copper were measured several times over a period of 100 days. At day 23, 58 and 97 needle biopsies of the liver were taken. The biopsies were used for histological examination and Cu-analysis. After 100 days the sheep were slaughtered and chronic copper poisoning was diagnosed by raised Cu concentration and typical histological alterations in the liver. The activities of GLDH and SDH in the plasma of the 5 sheep were consistently above normal, ASAT activity and the plasma Cu level were raised only occasionally. The results of Cu determination in biopsy samples were of little predictive value compared with post mortem Cu analysis of the liver. 相似文献
247.
248.
A. Colorni 《Aquaculture (Amsterdam, Netherlands)》1985,46(3):263-266
A practical dilution method for determining the degree of susceptibility of aquatic Vibrio and Aeromonas spp. to antibacterial agents is described. The method utilizes the differential ability of these two genera to ferment glucose. Acidification produced by the bacterial metabolism is demonstrated by the color change of an indicator (bromthymol blue) from blue-green to bright yellow. Where bacteria are inhibited by a sufficient concentration of the antibacterial drug tested, no color change occurs. The accurate quantitative results obtained with this method facilitate proper therapy for diseased fish, shrimps and oysters. The same method can in principle be applied to any other glucose-fermenting bacteria, when challenged with non-acidic antibacterial agents. 相似文献
249.
Canine liposarcoma 总被引:1,自引:0,他引:1
250.