全文获取类型
收费全文 | 145571篇 |
免费 | 8126篇 |
国内免费 | 85篇 |
专业分类
林业 | 5380篇 |
农学 | 4353篇 |
基础科学 | 1029篇 |
16816篇 | |
综合类 | 25419篇 |
农作物 | 5402篇 |
水产渔业 | 7307篇 |
畜牧兽医 | 75981篇 |
园艺 | 1768篇 |
植物保护 | 10327篇 |
出版年
2018年 | 1791篇 |
2017年 | 1977篇 |
2016年 | 1857篇 |
2015年 | 1624篇 |
2014年 | 1982篇 |
2013年 | 5397篇 |
2012年 | 3799篇 |
2011年 | 4773篇 |
2010年 | 2949篇 |
2009年 | 2988篇 |
2008年 | 4702篇 |
2007年 | 4484篇 |
2006年 | 4352篇 |
2005年 | 4051篇 |
2004年 | 3949篇 |
2003年 | 3947篇 |
2002年 | 3874篇 |
2001年 | 4690篇 |
2000年 | 4538篇 |
1999年 | 3691篇 |
1998年 | 1463篇 |
1997年 | 1488篇 |
1996年 | 1393篇 |
1995年 | 1744篇 |
1994年 | 1577篇 |
1993年 | 1503篇 |
1992年 | 3150篇 |
1991年 | 3279篇 |
1990年 | 3323篇 |
1989年 | 3321篇 |
1988年 | 3050篇 |
1987年 | 3132篇 |
1986年 | 3222篇 |
1985年 | 3087篇 |
1984年 | 2606篇 |
1983年 | 2309篇 |
1982年 | 1574篇 |
1981年 | 1471篇 |
1980年 | 1427篇 |
1979年 | 2316篇 |
1978年 | 1909篇 |
1977年 | 1623篇 |
1976年 | 1441篇 |
1975年 | 1540篇 |
1974年 | 2074篇 |
1973年 | 2086篇 |
1972年 | 2053篇 |
1971年 | 1816篇 |
1970年 | 1712篇 |
1969年 | 1571篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
A. A. Roess A. M. McCollum K. Gruszynski H. Zhao W. Davidson N. Lafon T. Engelmeyer B. Moyer C. Godfrey H. Kilpatrick A. Labonte J. Murphy D. S. Carroll Y. Li I. K. Damon 《Zoonoses and public health》2013,60(8):543-548
In 2008, two deer hunters in Virginia and Connecticut were infected with a unique strain of pseudocowpox virus, a parapoxvirus. To estimate the prevalence of this virus, and in an attempt to define the reservoir, Parapoxvirus surveillance was undertaken between November 2009 and January 2010. 125 samples from four ruminant species (cows, goat, sheep and white‐tailed deer) were collected in Virginia, and nine samples from white‐tailed deer were collected in Connecticut. We found no evidence that the parapoxvirus species that infected the deer hunters is circulating among domesticated ruminants or white‐tailed deer. However, parapoxvirus DNA of a different parapoxvirus species, bovine papular stomatitis virus (BPSV), was detected in 31 samples obtained from asymptomatic cattle in Virginia. Parapoxvirus DNA–positive cattle originated from the same counties indicating probable transmission among animals. Molecular analysis identified BPSV as the parapoxvirus affecting animals. Asymptomatic parapoxvirus infections in livestock, particularly young animals, may be common, and further investigation will inform our knowledge of virus transmission. 相似文献
992.
C. Drake B.Sc. A.B. Grant B.Sc. Ph.D. W.J. Hartley M.R.C.V.S. 《New Zealand veterinary journal》2013,61(1):4-5
Extract At the Annual General Meeting of the New Zealand Veterinary Association in 1951 a motion was carried “that this meeting recommend that a journal be started, and ask Council to investigate the matter from all aspects, and to report to the next Annual General Meeting.” To implement the wishes of the meeting, Council appointed a subcommittee which reported to the Annual General Meeting of 1952. The report, after dealing with costs and publishable material, recommended as follows:— 相似文献
993.
Abigail L. Fowden Juanita K. JellymanOrlando A. Valenzuela DVM MSc Alison J. Forhead PhD 《Journal of Equine Veterinary Science》2013
Human epidemiological observations and studies of experimental animals have shown that low birth weight is associated with adult phenotypes characterized by abnormalities in cardiovascular, metabolic, and endocrine function. In human populations, these changes can lead to overt degenerative diseases such as hypertension and type 2 diabetes. Because fetal growth depends primarily on the nutrient supply, the associations between birth weight and adult phenotype have been linked to poor nutrition in utero. The fetal supply of nutrients and oxygen depends on both the availability of these substances in the mother and the functional capacity of the placenta to supply them to the fetus. This review takes a comparative approach to examining the nutritional programming of adult physiological phenotype in mammals with emphasis on the horse where possible. It considers the role of maternal nutritional state and placental function in these processes and discusses the cellular and molecular mechanisms operating in utero that are responsible for the epigenetic regulation of phenotypical diversity. 相似文献
994.
995.
996.
R.M.P. Rocha L.F. Lima A.M.C.V. Alves J.J.H. Celestino M.H.T. Matos I.B. Lima-Verde M.P. Bernuci C.A.P. Lopes S.N. Báo C.C. Campello A.P.R. Rodrigues J.R. Figueiredo 《Domestic animal endocrinology》2013
The aim of this study was to investigate the effects of melatonin and follicle-stimulating hormone (FSH) on the in vitro culture of goat preantral follicles. Ovarian fragments were cultured for 7 d in α-minimum essential medium (α-MEM+) containing melatonin (100, 250, 500, or 1,000 pM), FSH (50 ng/mL), or a combination of the 2 hormones and further analyzed by histology and transmission electron and fluorescent microscopy. The results showed that after 7 d of culture, tissues cultured in α-MEM+ alone or supplemented with FSH alone, melatonin (500 and 1,000 pM), or the combination of FSH and melatonin (1,000 pM) maintained percentages of normal preantral follicles similar to the fresh control. In contrast to the noncultured tissues, the percentage of developing follicles was increased under all culture conditions after 7 d (P < 0.05). The addition of 1,000 pM melatonin associated with FSH to the culture medium increased follicular and oocyte diameters compared with α-MEM+ alone after 7 d of culture (P < 0.05). Ultrastructural and fluorescent analyses confirmed the integrity of follicles cultured with 1,000 pM of melatonin plus FSH for 7 d. In conclusion, this study demonstrated that the interaction between melatonin and FSH maintains ultrastructural integrity and stimulates further growth of cultured caprine preantral follicles. 相似文献
997.
T.J. McClure B.V.Sc. 《New Zealand veterinary journal》2013,61(5):107-112
Abstract Extract Sir.—I refer to the paper by Day(1) on induction of parturition in a dairy herd. This report was read with a considerable degree of interest as it included results which are significantly different from those which we would have expected from extensive field experience in New Zealand and overseas. 相似文献
998.
999.
In a field experiment, moderate to heavy natural concomitant infections with immature and mature Fasciola hepatica were treated with triclabendazole at a dose rate of 10 mg/kg and an efficiency of 99.8% was achieved. Subsequent treatments of all susceptible farm animals at the same dose rate at intervals of eight to eleven weeks were carried out for 14 months; no patent infections could be detected in sheep and cattle during the whole period. Evidence is presented that pasture contamination with liver fluke was reduced to a negligible level for a further 12 months after the final treatment. It is suggested that, if regular treatments with triclabendazole are given within the pre-patent period of Fasciola hepatica infection for the whole season, the infection can be eradicated or reduced to such a low level that control of the disease could be maintained with less frequent strategic drenching for a considerable period. 相似文献
1000.
Abstract Extract Madam:—I read with interest the letter Fu et al.(3in which they state that “Preliminary investigations on this stud have indicated that equine herpesvirus type 1 (EHV1) and type 2 (EHV2) were frequently isolated and might be the initiators of the respiratory disease observed”. Additional evidence that links EHV2 (equine cytomegalovirus or slowly growing equine herpesvirus) to equine respiratory disease will be important. There is some evidence and a very high level of suspicion that recurrent respiratory disease, malaise and poor performance are associated with EHV2 but providing definite evidence has been elusive and tends to be confounded by the fact that EHV2 can be isolated from more than 70% of horses, in some populations at least, but unassociated with recognisable disease. 相似文献