全文获取类型
收费全文 | 138845篇 |
免费 | 7526篇 |
国内免费 | 160篇 |
专业分类
林业 | 6539篇 |
农学 | 4436篇 |
基础科学 | 890篇 |
18131篇 | |
综合类 | 22043篇 |
农作物 | 5590篇 |
水产渔业 | 6959篇 |
畜牧兽医 | 70598篇 |
园艺 | 1988篇 |
植物保护 | 9357篇 |
出版年
2020年 | 1293篇 |
2019年 | 1428篇 |
2018年 | 2203篇 |
2017年 | 2457篇 |
2016年 | 2259篇 |
2015年 | 1892篇 |
2014年 | 2349篇 |
2013年 | 5646篇 |
2012年 | 4409篇 |
2011年 | 5363篇 |
2010年 | 3435篇 |
2009年 | 3515篇 |
2008年 | 5210篇 |
2007年 | 4944篇 |
2006年 | 4594篇 |
2005年 | 4289篇 |
2004年 | 4043篇 |
2003年 | 4140篇 |
2002年 | 3697篇 |
2001年 | 4244篇 |
2000年 | 4349篇 |
1999年 | 3438篇 |
1998年 | 1501篇 |
1997年 | 1400篇 |
1996年 | 1315篇 |
1995年 | 1559篇 |
1994年 | 1376篇 |
1993年 | 1259篇 |
1992年 | 2657篇 |
1991年 | 2784篇 |
1990年 | 2692篇 |
1989年 | 2720篇 |
1988年 | 2467篇 |
1987年 | 2427篇 |
1986年 | 2504篇 |
1985年 | 2411篇 |
1984年 | 1957篇 |
1983年 | 1737篇 |
1982年 | 1190篇 |
1979年 | 1833篇 |
1978年 | 1456篇 |
1977年 | 1205篇 |
1976年 | 1255篇 |
1975年 | 1352篇 |
1974年 | 1567篇 |
1973年 | 1594篇 |
1972年 | 1463篇 |
1971年 | 1372篇 |
1970年 | 1316篇 |
1969年 | 1358篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
951.
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
952.
953.
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
954.
955.
956.
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
957.
M. A. Sales K. Y. Murphy S. T. Reiter A. H. Brown Jr M. A. Brown M. L. Looper C. F Rosenkrans Jr 《Journal of animal physiology and animal nutrition》2013,97(1):91-96
Single‐nucleotide polymorphisms (SNP) in the coding sequence of cytochrome p450 (CYP3A28) have been associated with milk yield and composition, and calving traits in cows. In this study, we aimed to determine whether (i) the CYP3A28 regulatory region was polymorphic and (ii) SNP genotype, forage type, body condition and their interactions affect cow productivity. Primers for CYP3A28 promoter were designed to amplify a 483‐bp segment by PCR. Amplicon sequences revealed seven SNP (T‐318C, T‐113A, C‐189T, T‐78G, A6G, G17A and T21C) in Brahman (38 cows), Brahman x Angus reciprocal crosses (47 cows) and crossbreds (98 cows). Angus cows (n = 41) appeared to be fixed at those SNP locations. Genotype and forage {endophyte‐infected tall fescue [KY+; Lolium arundinaceum (Schreb.) S. J. Darbyshire] vs. bermudagrass [Cynodon dactylon (L.) Pers.]} effects on lifetime (8‐years) calving rate, and calf weaning weights and heights were determined in Herd 1 (126 cows); genotype and BC (low vs. moderate) effects on calving date and calving percent were determined in Herd 2 (98 cows). Four SNP (T‐318C, T‐113A, A06G and T21C) appeared to be related to cattle productivity, CC cows at T‐318C having a lower (p < 0.05) lifetime calving rate than TC or TT cows (65%, 85% and 81% respectively). Cows that grazed KY+ and were TT at T‐318C produced calves that tended (p < 0.07) to weigh less than their contemporaries. Moreover, calves of TT cows were shorter (p < 0.05) at weaning than calves of CC or TC cows. In Herd 2, moderate‐BC cows that were TT or AA at T‐318C, T‐113A, T‐78G, A6G and T21C had greater (p < 0.05) calving rates (74–80%) than heterozygous cows (46–60%), and low‐BC cows that were AA at G17A calved at least 6 days earlier (p < 0.05) than heterozygous cows. Our findings suggest that SNP in the CYP3A28 regulatory region of Brahman‐influenced cows are associated with cattle productivity. 相似文献
958.
959.
960.
R.A. Robinson B.V.Sc Dip.Microbiol. 《New Zealand veterinary journal》2013,61(4):52-53
Sir;- Outbreaks of ovine abortions caused by Campylobacter fetus fetus (previously C. fetus intestinalis) occur sporadically in mimy areas of New Zealand. The devastating effects on some flocks have stimulated recent studies of the disease,(1)(3)(7) and have also led to the commercial production of a single strain vaccine (Campylovexin; Wellcome N.Z. Ltd, Auckland). However, it has been shown that single strain C. Fetus vaccines do not protect against serologically distinct strains.(2) Since at least two different serotypes of C. fetus fetus are present in New ZealandY) it is not surprising that the commercially available vaccine is only partially effective in some outbreaks.(7) 相似文献