全文获取类型
收费全文 | 136326篇 |
免费 | 7352篇 |
国内免费 | 126篇 |
专业分类
林业 | 5995篇 |
农学 | 4195篇 |
基础科学 | 862篇 |
15922篇 | |
综合类 | 24692篇 |
农作物 | 5312篇 |
水产渔业 | 6444篇 |
畜牧兽医 | 70344篇 |
园艺 | 1636篇 |
植物保护 | 8402篇 |
出版年
2018年 | 1919篇 |
2017年 | 2094篇 |
2016年 | 1879篇 |
2015年 | 1630篇 |
2014年 | 2089篇 |
2013年 | 4783篇 |
2012年 | 3717篇 |
2011年 | 4512篇 |
2010年 | 2951篇 |
2009年 | 3122篇 |
2008年 | 4649篇 |
2007年 | 4273篇 |
2006年 | 4138篇 |
2005年 | 3828篇 |
2004年 | 3843篇 |
2003年 | 3898篇 |
2002年 | 3601篇 |
2001年 | 4242篇 |
2000年 | 4266篇 |
1999年 | 3382篇 |
1998年 | 1495篇 |
1997年 | 1390篇 |
1996年 | 1368篇 |
1995年 | 1515篇 |
1994年 | 1405篇 |
1993年 | 1372篇 |
1992年 | 2765篇 |
1991年 | 2947篇 |
1990年 | 2959篇 |
1989年 | 2850篇 |
1988年 | 2657篇 |
1987年 | 2619篇 |
1986年 | 2693篇 |
1985年 | 2615篇 |
1984年 | 2104篇 |
1983年 | 1915篇 |
1979年 | 1962篇 |
1978年 | 1562篇 |
1977年 | 1370篇 |
1976年 | 1243篇 |
1975年 | 1390篇 |
1974年 | 1659篇 |
1973年 | 1706篇 |
1972年 | 1704篇 |
1971年 | 1616篇 |
1970年 | 1582篇 |
1969年 | 1536篇 |
1968年 | 1304篇 |
1967年 | 1373篇 |
1966年 | 1271篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
991.
D W Hird R P Ruble S G Reagor P K Cronkhite M W Johnson 《Journal of the American Veterinary Medical Association》1992,201(3):471-474
Morbidity (greater than or equal to 1 disease condition) for pups sold from 3 pet stores from January 1987 through December 1988 ranged from 54 to 68%. In 1 store, morbidity was higher for store pups, compared with pups originating from private parties, for such disease conditions as "kennel cough," diarrhea, and several species of gastrointestinal parasites. In-store mortality ranged from 5 to 9.5% of pups arriving for sale. 相似文献
992.
The ovaries of two infertile cows of high breeding value were recovered after slaughter, and a total of 222 oocytes were obtained. Of these, 156 were classified as of good or fair quality and were subjected to in vitro maturation, in vitro fertilisation (using frozen semen from three bulls of high breeding value) and in vitro culture procedures. After eight days, 27 embryos were obtained, of which 13 were transferred fresh, and 14 were frozen. Three recipients of fresh embryos became pregnant; two calved and one aborted at four months. One of eight recipients of frozen-thawed embryos became pregnant but aborted at three months. 相似文献
993.
'Simultaneous' urethral pressure profilometry: Comparisons between continent and incontinent bitches
P. E. HOLT 《The Journal of small animal practice》1988,29(12):761-769
‘Simultaneous’ urethral pressure profilometry using microtip pressure transducer catheters was evaluated as an aid to the diagnosis of urethral sphincter mechanism incompetence by means of comparisons between 50 continent and 50 incontinent anaesthetised bitches. Highly significant differences were detected and the technique was found to have considerable potential as a diagnostic aid. 相似文献
994.
995.
996.
Host range of avian influenza virus in free-living birds 总被引:17,自引:0,他引:17
Isolation of avian influenza virus (AIV) has been reported from 12 orders and 88 species of free-living birds. Most isolations are reported from species in the orders Anseriformes and Charadriiformes and it is recognized that species in Anseriformes represent important reservoirs of AIV. Morbidity and mortality among free-living birds attributable to AIV infection are rare, but differences in prevalence of AIV occur within and between avian species. Seasonal variation has been reported from free-living and sentinel ducks with peak AIV infection occurring in late summer and early fall. Prevalence of AIV is age-related, with highest isolation rates reported from juvenile birds. Differences in susceptibility to AIV infection among species have been demonstrated under experimental conditions. The dynamics and epidemiology of species-related variation in populations of free-living birds require further study. 相似文献
997.
Electron microscopy as an aid to the rapid diagnosis of virus diseases of veterinary importance 总被引:2,自引:0,他引:2
The use of electron microscopy to assist in the rapid diagnosis of virus diseases of veterinary importance is reviewed. Electron microscopy can be used to assist the laboratory diagnosis of a virus disease at two stages during the investigation; either by demonstrating virus in clinical material or by identifying isolates from tissue culture or similar systems. Direct electron microscopy and immunoelectron microscopy are particularly useful for rapid diagnosis. The advantages of electron microscopy lie in speed and flexibility, and the disadvantages in the high particle concentration needed and the presumptive nature of a diagnosis. 相似文献
998.
Di Gialleonardo L Migliaccio P Teodori L Savini G 《Research in veterinary science》2011,91(2):316-320
Four groups of BTV free Frisian and cross bred calves were used to determine the length of viraemia following infection with different doses of BTV-8 Italian isolate. The first group of five animals was infected with 10 TCID50 of BTV-8, the second group of four animals with 103 TCID50 and the third group, which also included four animals, was infected with 106 TCID50. A placebo containing uninfected tissue culture medium was given to the four animals of the fourth group. The viraemia was evaluated by real time RT-PCR and virus isolation. In all infected groups, virus isolation was able to detect infectious virus up to 39 days post infection (dpi) while RT-PCR was positive up to 151–157 dpi. Infectious dose did influence neither the length nor the pattern of BTV-8 viraemia and confirmed that real time RT-PCR remains positive although no circulating virus is detectable in the peripheral circulation. 相似文献
999.
The short-term neurologic and long-term leptomeningeal effects of repeated subarachnoid administration of metrizamide at concentrations of 170 mg I/ml and 300 mg I/ml were investigated in dogs. After two months, arachnoid fibrosis of varying degrees was present in all dogs that had received metrizamide at the higher concentration. The higher concentration of met-rizamide was more epileptogenic than the concentration of 170 mg I/ml. The presence of subarachnoid hemorrhage was not considered to play a role in the development of the arachnoid fibrosis. Veterinary Radiology Vol. 21, No. 2, 1980; pp 78–81. 相似文献
1000.
Temporomandibular dysplasia was found in six American Cocker Spaniels related to each other. Clinical signs and diagnosis are described. 相似文献