全文获取类型
收费全文 | 81375篇 |
免费 | 4610篇 |
国内免费 | 313篇 |
专业分类
林业 | 3101篇 |
农学 | 2864篇 |
基础科学 | 538篇 |
10597篇 | |
综合类 | 13061篇 |
农作物 | 2861篇 |
水产渔业 | 4220篇 |
畜牧兽医 | 42846篇 |
园艺 | 981篇 |
植物保护 | 5229篇 |
出版年
2020年 | 701篇 |
2019年 | 824篇 |
2018年 | 1409篇 |
2017年 | 1493篇 |
2016年 | 1342篇 |
2015年 | 1124篇 |
2014年 | 1406篇 |
2013年 | 3328篇 |
2012年 | 2424篇 |
2011年 | 2952篇 |
2010年 | 2041篇 |
2009年 | 2033篇 |
2008年 | 2919篇 |
2007年 | 2696篇 |
2006年 | 2561篇 |
2005年 | 2280篇 |
2004年 | 2236篇 |
2003年 | 2232篇 |
2002年 | 1958篇 |
2001年 | 2867篇 |
2000年 | 2939篇 |
1999年 | 2243篇 |
1998年 | 902篇 |
1997年 | 841篇 |
1996年 | 748篇 |
1995年 | 951篇 |
1994年 | 805篇 |
1993年 | 703篇 |
1992年 | 1682篇 |
1991年 | 1862篇 |
1990年 | 1736篇 |
1989年 | 1699篇 |
1988年 | 1600篇 |
1987年 | 1598篇 |
1986年 | 1596篇 |
1985年 | 1458篇 |
1984年 | 1195篇 |
1983年 | 1022篇 |
1979年 | 1129篇 |
1978年 | 892篇 |
1977年 | 767篇 |
1976年 | 745篇 |
1975年 | 800篇 |
1974年 | 941篇 |
1973年 | 937篇 |
1972年 | 944篇 |
1971年 | 751篇 |
1970年 | 767篇 |
1969年 | 833篇 |
1967年 | 711篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Viral and bacterial agents associated with experimental transmission of infectious proventriculitis of broiler chickens. 总被引:1,自引:0,他引:1
G R Huff Q Zheng L A Newberry W E Huff J M Balog N C Rath K S Kim E M Martin S C Goeke J K Skeeles 《Avian diseases》2001,45(4):828-843
Proventriculitis of broilers can be reproduced by oral inoculation of day-old chicks with a proventricular homogenate from affected 3-wk-old broilers. The objective of the following studies was to isolate from this homogenate viral and bacterial isolates that could produce proventriculitis. A monoclonal antibody to infectious bursal disease virus (IBDV) was used to precipitate virus from the homogenate. A primary chicken digestive tract cell culture system was also used to isolate virus from a 0.2-microm filtrate of the homogenate, and a bacterium was also isolated from the homogenate. In trial 1, day-old birds were orally inoculated with either proventriculus homogenate or monoclonal antibody immunoprecipitated IBDV (MAB-IBDV). At 4, 7, 14, and 21 days postinfection (PI), 12 birds from each treatment group were subjected to necropsy. In trial 2, day-old birds were orally inoculated with either infectious proventriculus homogenate, suspect virus isolated in cell culture and propagated in embryo livers and spleens, or a bacterial isolate. Twelve birds from each treatment were subjected to necropsy at days 7, 14, 21, and 28 PI. In trial 3, treatments were maintained in negative pressure isolation chambers, and an additional treatment included virus plus bacterial isolate. Twenty-four birds from each treatment were subjected to necropsy at day 21 PI. In trial 1, infectious homogenate decreased body weight and relative gizzard weights at 4, 7, 14, and 21 days PI. Proventriculus relative weight was increased at days 7, 14, and 21 PI, and proventriculus lesion scores were increased at days 14 and 21 PI. Bursa/spleen weight ratios were decreased at day 14, and feed conversion was increased at days 4 and 21. The MAB-IBDV treatment decreased proventriculus and gizzard relative weights at day 4 PI, increased proventriculus lesion scores and bursa/spleen weight ratios at day 14, and decreased heterophil/lymphocyte ratios at day 21. In trial 2, all infected birds had significantly higher mean relative proventriculus weights at 21 days PI and had higher 4-wk mean proventriculus scores as compared with both control groups. In trial 3, birds treated with homogenate and birds treated with both suspect virus and the bacterial isolate had significantly higher proventriculus lesion scores; higher relative weights of proventriculus, gizzard, liver, and heart; lower body weights; and lower relative bursa weights compared with the saline control group. These studies suggest that infectious proventriculitis has a complex etiology involving both viral and bacterial infection. 相似文献
22.
S T Grubbs S A Kania L N Potgieter 《Journal of veterinary diagnostic investigation》2001,13(2):128-132
Subgroup-specific peptide-based enzyme-linked immunosorbent assays from the G-protein of the ovine and bovine respiratory syncytial virus (RSV), respectively, were used to determine the prevalence of the ovine and bovine subgroup strains of RSV infections in cattle. A total of 1,102 bovine serum samples were obtained from 6 diagnostic laboratories located in the northwestern and the southeastern USA and were tested for antibody to either the bovine or ovine subgroups of RSV. Antibody to viruses from each subgroup was present in samples from each region and all states tested. The Southeast had a higher prevalence of the bovine subgroup strains (69.5%). Then did the Northwest (40.9%). The prevalence of the ovine strain was similar for the two regions (16.7% in the southeast, 14.9% in the northwest). The overall prevalence was 56.6% for the bovine strain and 15.9% for the ovine strain. These results suggest members of the ovine subgroup of RSV circulate in the cattle population but with less frequency than those viruses of the bovine subgroup. 相似文献
23.
24.
25.
G. L. RICHARDSON dvm T. R. O'BRIEN dvm PhD Diplomateacvr J. R. PASCOE bvsc D. M. MEAGHER dvm PhD Dipiomateacvs 《Veterinary surgery : VS》1986,15(2):156-160
The medical records of 38 horses with puncture wounds of the navicular bursa were reviewed. Only 12 horses had a satisfactory outcome (breeding or riding). Of the remaining 26 horses, 19 were euthanized, five were sold due to persistent severe lameness, one died, and one was lost to long-term follow-up. Different combinations of conservative management prior to surgical debridement and drainage of the navicular bursa were unsuccessful in resolving the condition. Horses that were treated surgically within 1 week of the injury and had a hind leg affected had the best chance of a satisfactory outcome. Additional wound debridement was necessary in 15 horses after initial surgical treatment. The most common complications encountered were navicular bone osteomyelitis and sepsis of the deep digital flexor tendon. Thirteen of 14 horses that had rupture of the deep digital flexor tendon and subluxation of the distal interphalangeal joint had an unsatisfactory outcome. One mare subsequently developed ankylosis of the distal interphalangeal joint and was a useful brood mare. Two horses that had biaxial palmar digital neurectomy because of persistent lameness were later euthanized because of navicular bone fracture and rupture of the deep digital flexor tendon. Results from limited numbers of bacterial cultures and antibiotic sensitivities suggest that penicillin and an aminoglycoside antibiotic should be used as initial antibiotic therapy. Immediate surgical debridement and appropriate antibiotic treatment are recommended as the minimum therapy for penetrating wounds of the navicular bursa in horses. 相似文献
26.
Thirteen mixed-breed beef bulls, 1 to 4 years old, were used to determine the effect of live and dead filarial nematodes, Setaria labiatopapillosa, placed in the vaginal cavity of the testes. When dead worms were used, granulomatous lesions developed on the tunica vaginalis parietalis in 7 of 8 testes. The lesions were similar to those seen in some clinical cases of periorchitis. Similar lesions developed in 5 of 6 testes after live worms were implanted in the vaginal cavity of the testes and tetramisole (8 mg/kg) was injected subcutaneously 6 days after implantation. When live worms were implanted and tetramisole was not given, lesions developed in 3 of 6 testes. It was concluded that the granulomatous reaction was a local response to dead or killed S labiatopapillosa. 相似文献
27.
Mid-storage hydration-dehydration treatments with medium-vigour lettuce seed very effectively reduced physiological deterioration in storage and ultimately showed better field emergence and final yield. Soaking-drying treatment of high-vigour lettuce seed was not effective. Pre-sowing treatment of medium-vigour lettuce seed, though less effective than mid-storage treatment, gave better field performance, but high-vigour seed did not benefit from the treatment. For carrot, both mid-storage and pre-sowing seed treatments proved beneficial, with the former showing better performance than the latter. Unlike lettuce, well-preserved carrot seed responded positively to the pre-sowing treatment. 相似文献
28.
29.
30.