全文获取类型
收费全文 | 144865篇 |
免费 | 7980篇 |
国内免费 | 150篇 |
专业分类
林业 | 5697篇 |
农学 | 3946篇 |
基础科学 | 920篇 |
16102篇 | |
综合类 | 27386篇 |
农作物 | 5537篇 |
水产渔业 | 6680篇 |
畜牧兽医 | 76574篇 |
园艺 | 1599篇 |
植物保护 | 8554篇 |
出版年
2018年 | 1876篇 |
2017年 | 2104篇 |
2016年 | 1905篇 |
2015年 | 1637篇 |
2014年 | 2098篇 |
2013年 | 5146篇 |
2012年 | 3734篇 |
2011年 | 4688篇 |
2010年 | 2916篇 |
2009年 | 3082篇 |
2008年 | 4575篇 |
2007年 | 4287篇 |
2006年 | 4148篇 |
2005年 | 3766篇 |
2004年 | 3698篇 |
2003年 | 3753篇 |
2002年 | 3466篇 |
2001年 | 4486篇 |
2000年 | 4562篇 |
1999年 | 3474篇 |
1998年 | 1357篇 |
1997年 | 1374篇 |
1996年 | 1362篇 |
1995年 | 1618篇 |
1994年 | 1412篇 |
1993年 | 1413篇 |
1992年 | 3017篇 |
1991年 | 3340篇 |
1990年 | 3109篇 |
1989年 | 3142篇 |
1988年 | 2941篇 |
1987年 | 3040篇 |
1986年 | 3140篇 |
1985年 | 3008篇 |
1984年 | 2370篇 |
1983年 | 2093篇 |
1982年 | 1417篇 |
1979年 | 2241篇 |
1978年 | 1808篇 |
1977年 | 1547篇 |
1976年 | 1425篇 |
1975年 | 1562篇 |
1974年 | 2055篇 |
1973年 | 2054篇 |
1972年 | 2025篇 |
1971年 | 1893篇 |
1970年 | 1844篇 |
1969年 | 1695篇 |
1968年 | 1480篇 |
1967年 | 1509篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
J P Dubey A N Hamir C A Hanlon C E Rupprecht 《Journal of the American Veterinary Medical Association》1992,200(4):534-536
Serum samples from 427 raccoons (93 from Pennsylvania, 45 from New Jersey, 72 from South Carolina, 68 from Virginia, 30 from Iowa, and 119 from Ohio) were evaluated for Toxoplasma gondii antibodies in dilutions of 1:25, 1:50, and 1:500. The distribution of T gondii antibody titers was less than 1:25 for 212 raccoons (49.6%), 1:25 for 34 raccoons (7.9%), 1:50 for 117 raccoons (27.4%), and greater than or equal to 1:500 for 64 raccoons (14.9%). Tissue cysts were seen in the liver, and tachyzoites were in the brain of a raccoon with abnormal neurologic signs and concurrent infection with canine distemper virus. Organisms in the liver were stained with anti-T gondii serum, and the raccoon had a T gondii titer of 1:160 in the agglutination test. 相似文献
103.
When susceptibility to virulent Pasteurella multocida was compared, there was no significant (P greater than 0.05) difference between caponized and uncaponized tom turkeys. Neither was there any significant (P greater than 0.05) difference between the surviving caponized and uncaponized toms in the development of serum anti-P. multocida antibody. However, at 28 weeks of age, the average live body weight of the caponized toms was significantly (P less than 0.05) lower than that of the uncaponized toms. Turkeys were caponized when 9 weeks old, and different groups were exposed to P. multocida when 13, 18, 23, and 28 weeks old. 相似文献
104.
K G Braund H S Steinberg A Shores J E Steiss J R Mehta M Toivio-Kinnucan K A Amling 《Journal of the American Veterinary Medical Association》1989,194(12):1735-1740
Six dogs with laryngeal paralysis had clinical, electrophysiologic, and pathologic evidence of a more generalized polyneuropathy. Three of the dogs were young Dalmatians, one was a young Bouvier des Flandres, and two were older, large-breed dogs. The results of this study suggest that laryngeal paralysis in dogs may frequently be one clinical sign of an underlying, more generalized polyneuropathy. Two forms of this generalized polyneuropathy may exist: an early form, as seen in young dogs with congenital or hereditary disease, and a delayed-onset form that is usually found in older dogs with so-called idiopathic laryngeal paralysis, some of which may have hypothyroidism. 相似文献
105.
DV COUSINS SN WILLIAMS R. REUTER† D. FORSHAW† B. CHADWICK§ D. COUGHRAN¶ P. COLLINS# N. GALES 《Australian veterinary journal》1993,70(3):92-97
SUMMARY Tuberculosis was diagnosed in 3 otariid seals found dead on beaches at 3 locations on the south coast of Western Australian between May 1990 and March 1991. This confirms that tuberculosis is present in the 2 native seals (Neophoca cinerea and Arctocephalus forsteri) in Western Australian waters. Mycobacterium sp isolated from the lungs of 2 of the seals were studied to determine the similarity of the strains to each other, to the strains isolated during 1986 from Australian sea lions and New Zealand fur seals kept in captivity at a marine park near Perth, Western Australia, and to a strain isolated in 1988 from a seal trainer who worked with the infected captive seals for 3 years. After restriction endonuclease analysis (REA) with the endonucleases Bst Ell, Bcl I and Pvu II, one of the wild seal strains appeared to have identical DNA fragment patterns to the strains from the captive seals and the seal trainer. The other wild seal isolate had identical REA profiles using Bst EII and Bcl I, but a minor difference was detected using Pvu II. Differences in these isolates were more clearly seen in restriction fragment length polymorphisms after hybridisation with two DNA probes. The secretory protein MPB70, present in M bovis, was not detected in wild seal isolates using sodium dodecyl sulphate polyacrylamide gel electrophoresis and Western blotting techniques. Analysis of protein and DNA fragment profiles indicated that seal tuberculosis isolates form a unique cluster within the M tuberculosis complex. 相似文献
106.
107.
Melissa trogdon Hines DVM PhD Jerry R. Heidel DVM PhD David D. Barbee DVM MS 《Veterinary radiology & ultrasound》1993,34(1):47-51
A 2.5 year old Appaloosa stallion with progressive weight loss and a heart murmur was diagnosed as having vegetative endocarditis of the right atrioventricular valves with a mass in the right atrium. The ultrasonographic appearance of the lesion was characterized by extreme reverberation. On postmortem examination, a 9 cm diameter thrombus was found within the right atrium and auricle, occupying approximately 80% of the chamber volume. Additionally, a lenticular abscess extended throughout the parietal cusp of the right atrioventricular valve. Histologic examination revealed that the lesions were septic with numerous gram positive cocci in short chains, suggestive of Streptococcus equi , and gram negative rods. 相似文献
108.
S. Dänicke I. Halle E. Strobel E. Franke & H. Jeroch 《Journal of animal physiology and animal nutrition》2001,85(9-10):301-313
109.
Six bullmastiffs with congenital heart disease were evaluated over a three-year period. In all the cases the problem was shown to be dysplasia of the pulmonary valve. Five cases were male, one was female. All dogs available to follow-up developed signs of cardiac decompensation. Bullmastiffs must be added to the list of breeds in which valvular pulmonic stenosis is encountered frequently. 相似文献
110.
L. Papazoglou D. Raptopoulos M. Kritsepi A. Galatos 《Veterinary anaesthesia and analgesia》1993,20(1):30-31
Xylazine (0.2 mg/kg, iv) alone or preceded by atipame-zole (0.125 μg/kg, iv) or by aspirin (10 μg/kg, iv) was administered to 18 sheep. Medetomidine (60 μg/kg, iv) was also administered to 12 sheep. Xylazine, but not medetomidine, significantly reduced the number of platelets. Both atipamezole and aspirin prevented this reduction. It was concluded that α2-agonists would seem to produce platelet aggregation that may contribute to the development of the respiratory changes that follow the administration of α2-agonists in sheep, but probably not always to a degree that could result in a significant decrease in the number of circulating platelets. 相似文献