全文获取类型
收费全文 | 117773篇 |
免费 | 1975篇 |
国内免费 | 35篇 |
专业分类
林业 | 4639篇 |
农学 | 3263篇 |
基础科学 | 782篇 |
12049篇 | |
综合类 | 23288篇 |
农作物 | 4210篇 |
水产渔业 | 4908篇 |
畜牧兽医 | 58601篇 |
园艺 | 1295篇 |
植物保护 | 6748篇 |
出版年
2018年 | 1319篇 |
2017年 | 1374篇 |
2016年 | 1272篇 |
2015年 | 1141篇 |
2014年 | 1297篇 |
2013年 | 4085篇 |
2012年 | 2668篇 |
2011年 | 3182篇 |
2010年 | 2033篇 |
2009年 | 1975篇 |
2008年 | 3038篇 |
2007年 | 2999篇 |
2006年 | 2885篇 |
2005年 | 2715篇 |
2004年 | 2595篇 |
2003年 | 2736篇 |
2002年 | 2613篇 |
2001年 | 3018篇 |
2000年 | 2953篇 |
1999年 | 2464篇 |
1998年 | 1066篇 |
1995年 | 1143篇 |
1994年 | 1089篇 |
1992年 | 2243篇 |
1991年 | 2477篇 |
1990年 | 2469篇 |
1989年 | 2488篇 |
1988年 | 2354篇 |
1987年 | 2282篇 |
1986年 | 2357篇 |
1985年 | 2350篇 |
1984年 | 1924篇 |
1983年 | 1745篇 |
1982年 | 1195篇 |
1981年 | 1124篇 |
1980年 | 1063篇 |
1979年 | 1846篇 |
1978年 | 1521篇 |
1977年 | 1389篇 |
1976年 | 1354篇 |
1975年 | 1463篇 |
1974年 | 1848篇 |
1973年 | 1763篇 |
1972年 | 1802篇 |
1971年 | 1676篇 |
1970年 | 1663篇 |
1969年 | 1499篇 |
1968年 | 1262篇 |
1967年 | 1391篇 |
1966年 | 1146篇 |
排序方式: 共有10000条查询结果,搜索用时 302 毫秒
991.
A 3-year-old Texas Longhorn steer had a long history of progressive swelling of the soft tissues of the jaw and neck. At necropsy, multifocal to coalescing dermal and subcutaneous pyogranulomas were surrounded by fibrous tissue. Microscopically, the pyogranulomas contained aggregates of gram-negative coccobacilli surrounded by Splendore-Hoeppli material and were separated by bands of fibrovascular tissue (botryomycosis). Phylogenetic analysis of multilocus sequence-typing data revealed that the bacteria recovered in pure culture from swabs of submandibular tissue were most closely related to Bibersteinia [Pasteurella] trehalosi. The bacterial colonies were immunohistochemically reactive with a rabbit polyclonal anti-Pasteurella class C acid phosphatase antibody. Botryomycosis is a pyogranulomatous inflammation caused by a variety of nonbranching, nonfilamentous bacteria that elicit the formation of Splendore-Hoeppli material. This case of botryomycosis is unique for its association with Bibersteinia trehalosi. 相似文献
992.
993.
994.
D J McNaught R J Chappel G S Allan J A Bourke B A Rogerson 《Research in veterinary science》1977,22(2):194-197
Addition of Brucella-specific IgG2 to solutions of Brucella-specific IgG1 initially induced prozoning and at higher concentrations prevented all reaction in the complement fixation test (CFT) for bovine brucellosis. Some infected cattle may be diagnosed as brucellosis-free due to a high ratio of specific IgG2 to IgG1. Increasing the concentration of antigen in the CFT reduced the tendency to prozone. 相似文献
995.
Ryll M Christensen H Bisgaard M Christensen JP Hinz KH Köhler B 《Journal of veterinary medicine. B, Infectious diseases and veterinary public health》2001,48(7):537-546
A total of 44 bacterial strains obtained from 49 clinically healthy ducklings of different ages originating from four different farms were identified as members of the species Riemerella anatipestifer (RA) using conventional biochemical test methods. Numerical analysis of the whole-cell fatty acid patterns of these isolates resulted in two different clusters, one of which showed a similar pattern to that of the type strain of RA. Strains having a different fatty acid methyl esters (FAME)-profile (cluster II) were designated R. anatipestifer-like (RA-like). Sequencing of 16S rRNA genes of RA-like field isolates revealed 99% identity to RA. The significance of these observations are discussed. The present findings document for the first time that RA seems to represent a normal part of the pharyngeal flora of healthy Pekin ducks. 相似文献
996.
Polikepahad S Paulsen DB Moore RM Costa LR Venugopal CS 《American journal of veterinary research》2006,67(2):348-357
OBJECTIVE: To immunohistochemically determine the expression of endothelin (ET) receptors in bronchial smooth muscle and epithelium of healthy horses and horses affected by summer pasture-associated obstructive pulmonary disease (SPAOPD). SAMPLE POPULATION: Tissue specimens obtained from 8 healthy and 8 SPAOPD-affected horses. PROCEDURE: Horses were examined and assigned to healthy and SPAOPD groups. Horses were then euthanatized, and tissue specimens containing bronchi of approximately 4 to 8 mm in diameter were immediately collected from all lung lobes, fixed in zinc-formalin solution for 12 hours, and embedded in paraffin. Polyclonal primary antibodies against ET-A or ET-B receptors at a dilution of 1:200 and biotinylated IgG secondary antibodies were applied to tissue sections, followed by the addition of an avidin-biotin immunoperoxidase complex. Photographs of the stained slides were digitally recorded and analyzed by use of image analysis software to determine the intensity of staining. Two-way ANOVA was used for statistical analysis. RESULTS: The left diaphragmatic lung lobe of SPAOPD-affected horses had a significantly greater area of bronchial smooth muscle that immunostained for ET-A, compared with that for healthy horses. All lung lobes of SPAOPD-affected horses, except for the right diaphragmatic lobe, had significantly greater staining for ET-B receptors in bronchial smooth muscle, compared with results for healthy horses. CONCLUSIONS AND CLINICAL RELEVANCE: This study revealed overexpression of ET-A and, in particular, ETB receptors in the bronchial smooth muscle of SPAOPD-affected horses, which suggested upregulation of these receptors. These findings improve our understanding of the role of ET-1 in the pathogenesis of SPAOPD. 相似文献
997.
Brand TS Johnson Q Franck F Veith W Conradie R Hough FS 《Journal of the South African Veterinary Association》1999,70(1):9-13
Increased dietary protein consumption is thought to cause calciuresis, a negative calcium balance and increased bone loss that may result in skeletal deformities and fracture. To explore this hypothesis, 40 approximately 100-day-old meat-type Merino ram lambs were fed, for 6 months, diets with an increasing crude protein (CP) content (114, 142, 171 and 190 g/kg DM) but approximately on an iso-nutrient basis with regard to metabolisable energy, calcium and phosphorus. Increased protein consumption modestly (NS) enhanced calciuresis and resulted in significant (P < or = 0.01) limb skewness. This could not, however, be ascribed to osteopaenic bones, and compared with animals consuming lower protein rations, the bone mineral density (BMD) and vertebral trabecular bone volume of animals fed high protein diets were significantly increased: the BMD of thoracic vertebrae was positively related to the CP intake (r = 0.62; P < or = 0.001). In animals consuming higher protein diets, skeletal radiology and quantitative bone histology revealed no evidence of increased bone turnover as would be expected in animals that are in negative calcium balance. No relationship existed between limb skewness and the growth rate of lambs. However, the ratio of Ca:P in the forelimb (r = -0.98), vertebrae (r = -0.72) and rib (r = -0.42) was found to be inversely correlated with increased protein intake and resulted from an increase in the phosphorus content of bone, while the amount of bone calcium was unaffected. We conclude that qualitative micro-architectural abnormalities, and not mere bone loss, may underlie the skeletal deformities induced by increased protein consumption in sheep. 相似文献
998.
Irausquin RA Scavelli TD Corti L Stefanacci JD DeMarco J Flood S Rohrbach BW 《The Canadian veterinary journal. La revue veterinaire canadienne》2008,49(1):46-52
Evaluation of dogs with splenic masses to better educate owners as to the extent of the disease is a goal of many research studies. We compared the use of ultrasonography (US) and contrast-enhanced computed tomography (CT) to evaluate the accuracy of detecting hepatic neoplasia in dogs with splenic masses, independently, in series, or in parallel. No significant difference was found between US and CT. If the presence or absence of ascites, as detected with US, was used as a pretest probability of disease in our population, the positive predictive value increased to 94% if the tests were run in series, and the negative predictive value increased to 95% if the tests were run in parallel. The study showed that CT combined with US could be a valuable tool in evaluation of dogs with splenic masses. 相似文献
999.
Zhao G. R. Fan Z. W. An T. X. Kai L. Zhou F. Wu K. X. Wu B. Z. Fullen M. A. 《Eurasian Soil Science》2022,55(8):1116-1125
Eurasian Soil Science - Despite the general consensus that fertilizer is the most important driver of the evolution of soil microbial communities, the specific effects of long-term fertilizer use... 相似文献
1000.