全文获取类型
收费全文 | 138312篇 |
免费 | 7867篇 |
国内免费 | 803篇 |
专业分类
林业 | 5920篇 |
农学 | 4586篇 |
基础科学 | 1077篇 |
16856篇 | |
综合类 | 25708篇 |
农作物 | 5153篇 |
水产渔业 | 6686篇 |
畜牧兽医 | 70417篇 |
园艺 | 1914篇 |
植物保护 | 8665篇 |
出版年
2019年 | 1417篇 |
2018年 | 2088篇 |
2017年 | 2362篇 |
2016年 | 2140篇 |
2015年 | 1983篇 |
2014年 | 2320篇 |
2013年 | 5047篇 |
2012年 | 4335篇 |
2011年 | 5279篇 |
2010年 | 3577篇 |
2009年 | 3488篇 |
2008年 | 5067篇 |
2007年 | 4710篇 |
2006年 | 4413篇 |
2005年 | 4176篇 |
2004年 | 3965篇 |
2003年 | 4020篇 |
2002年 | 3786篇 |
2001年 | 4279篇 |
2000年 | 4290篇 |
1999年 | 3428篇 |
1998年 | 1534篇 |
1997年 | 1387篇 |
1996年 | 1311篇 |
1995年 | 1448篇 |
1994年 | 1365篇 |
1993年 | 1293篇 |
1992年 | 2734篇 |
1991年 | 2933篇 |
1990年 | 2968篇 |
1989年 | 2802篇 |
1988年 | 2629篇 |
1987年 | 2612篇 |
1986年 | 2668篇 |
1985年 | 2489篇 |
1984年 | 2116篇 |
1983年 | 1879篇 |
1982年 | 1207篇 |
1979年 | 1882篇 |
1978年 | 1510篇 |
1977年 | 1300篇 |
1976年 | 1290篇 |
1975年 | 1360篇 |
1974年 | 1668篇 |
1973年 | 1686篇 |
1972年 | 1631篇 |
1971年 | 1521篇 |
1970年 | 1469篇 |
1969年 | 1447篇 |
1967年 | 1255篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
A W vd Giessen R Peters P A Berkers W H Jansen S H Notermans 《The Veterinary quarterly》1991,13(1):41-46
The contamination of poultry in the Netherlands with Salmonella enteritidis was tested. For this, different methods (detection of S. enteritidis in faecal samples of 25 g; detection of S. enteritidis in cloacal swabs; detection of S. enteritidis by serological testing of antibodies in serum) were compared for their efficiency to detect S. enteritidis in flocks of poultry. Testing of faecal samples clearly yielded the best results. This method was used in a transmission study, in which 14 flocks descending from a contaminated primary mother flock were screened for the presence of S. enteritidis. The method was also used for screening 49 flocks of laying hens and 52 flocks of broiler chickens throughout the Netherlands. From the transmission study it became clear that S. enteritidis, phage type 2 (Dutch phage set) was isolated both from the mother flock and from five of the descendent flocks. Screening of poultry flocks for the presence of salmonella revealed that salmonella was present in 47% of the layer flocks and in 94% of the broiler flocks. S. enteritidis was isolated from 15% of the flocks screened. 相似文献
102.
A P Davidson 《Veterinary Clinics of North America: Small Animal Practice》2001,31(2):411-420
The practice of small animal theriogenology is rewarding, but frustrations exist concerning technologic advances as compared with other species. Reproductive clinicians striving to practice good quality medicine readily identify topics of common concern: causes that are not identified or therapeutics that are not available or applicable. Improved collaboration among theriogenologists specializing in small animal practice is evidenced by growing attendance at national and international scientific meetings, increased scientific publications, and internet communications. 相似文献
103.
L.E. Young D.H. Bartram M. Diamond A. Gregg R.S. Jones 《Veterinary anaesthesia and analgesia》1991,18(Z1):171-174
104.
L A Janssens 《Veterinary surgery : VS》1991,20(4):274-278
Seven foci of pain (trigger points) were identified in the triceps brachii, infraspinatus, adductor-pectineus, peroneus longus, gluteus medius, ileocostorum lumborum, and quadriceps femoris muscles in 48 lame dogs. The dogs had been lame for 1 day to 150 weeks (mean, 24 weeks). Thirty-one dogs had been treated unsuccessfully with corticosteroids, nonsteroidal anti-inflammatory drugs, analgesics, or acupuncture. Palpating the trigger points induced severe pain. Treatment consisted of weekly stimulation of the trigger points by needling or injection of a local anesthetic. The mean treatment period was 2.8 weeks. Excellent results and complete recovery were observed in 34 dogs (60%). 相似文献
105.
An ammonium sulfate fraction of Taenia hydatigena cyst fluid (ThFAS) was further fractionated by hydrophobic interaction chromatography, using alkylagarose and omega-amino alkylagarose columns, in an effort to isolate and purify a specific diagnostic antigen in the ThFAS preparation. The less than 12 kDa antigen was found to have an affinity for immobilized alkanes with chain length of six carbons or greater. The antigen was recovered in an ethylene glycol eluate from a hexylagarose column then analyzed by Western blot; it reacted with bovine and human cysticercosis infection sera and with specific monoclonal antibodies but not with control sera or fascioliasis infection sera. When the eluate was used as coating antigen in a plate ELISA assay no false positive reactions were seen in sera from cattle infected with Fasciola hepatica; false positive reactions were observed for the unfractionated ThFAS antigen preparation. 相似文献
106.
R. Iori O. Leoni L. Lazzeri G. Mosca S. Palmieri 《Journal of Agronomy and Crop Science》1991,167(2):91-95
Samples of rapeseed from three Italian growing environments (Bologna, Perugia and Palermo) were analysed for glucose content and dry weight of 1000 seeds every three or four days starting from the end of flowering until complete ripening. In addition, the content of oil, soluble and total proteins, glucosinolates and myrosinase activity was determined in samples of mature seeds. The cultivars used were jet Neuf and Lingot (type 0) and Tandem, Jade and Santana (type 00). From the results it emerged that the point of intersection of the two branches of the linear regression plots for different glucose-consumption kinetics found during seed filling, in addition to being strongly affected by the climate of the test environment, is correlated with quantitative and qualitative production, independently of the genotype. 相似文献
107.
Thyroid scintigraphy in small animals 总被引:1,自引:0,他引:1
108.
109.
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
110.
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