全文获取类型
收费全文 | 300912篇 |
免费 | 17025篇 |
国内免费 | 1251篇 |
专业分类
林业 | 24468篇 |
农学 | 14490篇 |
基础科学 | 3223篇 |
46464篇 | |
综合类 | 40092篇 |
农作物 | 17503篇 |
水产渔业 | 17821篇 |
畜牧兽医 | 123042篇 |
园艺 | 6723篇 |
植物保护 | 25362篇 |
出版年
2020年 | 3110篇 |
2019年 | 3870篇 |
2018年 | 4419篇 |
2017年 | 4947篇 |
2016年 | 5120篇 |
2015年 | 4655篇 |
2014年 | 5976篇 |
2013年 | 16634篇 |
2012年 | 7966篇 |
2011年 | 10277篇 |
2010年 | 8283篇 |
2009年 | 8637篇 |
2008年 | 9329篇 |
2007年 | 8544篇 |
2006年 | 8828篇 |
2005年 | 8104篇 |
2004年 | 7753篇 |
2003年 | 7587篇 |
2002年 | 6848篇 |
2001年 | 7670篇 |
2000年 | 7308篇 |
1999年 | 6510篇 |
1998年 | 4331篇 |
1997年 | 4337篇 |
1996年 | 4070篇 |
1995年 | 4638篇 |
1994年 | 4097篇 |
1993年 | 3809篇 |
1992年 | 5270篇 |
1991年 | 5528篇 |
1990年 | 5230篇 |
1989年 | 5230篇 |
1988年 | 4694篇 |
1987年 | 4777篇 |
1986年 | 4825篇 |
1985年 | 4878篇 |
1984年 | 4431篇 |
1983年 | 4101篇 |
1982年 | 3239篇 |
1981年 | 3121篇 |
1980年 | 3035篇 |
1979年 | 3868篇 |
1978年 | 3392篇 |
1977年 | 3068篇 |
1976年 | 2949篇 |
1975年 | 2852篇 |
1974年 | 3286篇 |
1973年 | 3194篇 |
1972年 | 2978篇 |
1971年 | 2916篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
C. P. Daurio E. N. Cheung A. R. Jeffcoat B. J. Skelly 《Veterinary research communications》1992,16(2):125-130
The bioavailability of three formulations of ivermectin was determined following oral administration to dogs. The average peak plasma level (C
max) of ivermectin administered in the standard tablet formulation at 6 and 100 µg/kg of body weight was 2.97 and 44.31 ng/g, respectively. This suggest dose-dependent pharmacokinetics.C
max and total ivermectin bioavailability, as assessed from the area under the plasma curve (AUC), were similar between two tablet formulations of ivermectin administered at 100 µg/kg. Furthermore,C
max was similar following administration of radiolabelled ivermectin at 6 µg/kg in either a beef-based chewable formulation or in the standard tablet formulation. 相似文献
992.
M Kachani R A Oliver C G Brown H Ouhelli R L Spooner 《Veterinary immunology and immunopathology》1992,34(3-4):221-234
Western blot analysis of Theileria annulata antigens was carried out using sera collected from cattle which had been immunised and challenged with either T. annulata sporozoites or schizont-infected cells. Three antigens between 71 and 73 kDa proved to be common to the three stages of parasite studied: sporozoites, schizonts and piroplasms. An antigen was found at 32 kDa which was specific to T. annulata piroplasms. Results were reproducible using sera from Morocco and the UK. At least one of the proteins at 71-73 kDa, but not that at 32 kDa were also recognised by sera from animals infected with Babesia species. 相似文献
993.
Previous studies have documented the effectiveness of porcine somatotropin (pST) administered by daily injection in promoting lean tissue growth in lean and obese pigs and the influence of sex and genotype. The present study examined the accretive responses in pigs of different lines and sexes to a slow release formulation of pST (pST-SR). Implants that deliver 2.0 mg of pST/d were implanted in genetically lean and obese barrows and gilts at 65 +/- .7 kg BW (mean +/- SE). Pigs received no, one, or two implants (i.e., doses of 0, 2.0, and 4.0 mg of pST/d). Pigs (four per line x sex x dose) were housed individually and continuously supplied with fresh water and a 19% CP diet containing 1.08% lysine. Pigs were slaughtered on d 0 (four per line x sex) and at the end of the trial (approximately 42 d after implantation) for estimation of initial composition and calculation of accretion rates. Blood samples were collected at d 0, 7, 14, 28, and 42 to measure endocrine and metabolite responses to pST-SR. Sustained-release pST elevated (P < .05) circulating pST throughout the trial with peak concentrations at d 7. On d 7, serum pST concentrations in the pigs given 2.0 mg of pST-SR per day were 16-fold greater than those in control pigs, and in pigs given 4.0 mg of pST-SR per day pST concentrations were 33-fold greater than in controls. Elevated serum pST resulted in increased (P < .05) serum concentrations of insulin-like growth factor (IGF)-I, IGF-II, insulin, and glucose and in reduced (P < .05) concentrations of urea nitrogen and IGF binding protein (IGFBP)-2. Gain was not influenced by pST-SR dose; however, feed consumption was reduced (P < .05) and efficiency of gain was increased (P < .05). Accretion of all body components except cold carcass weight, cecum, and untrimmed Boston butt and ham were changed (P < .05) with pST-SR administration. Heart and stomach were the only components of the carcass and offal whose accretion was not affected by line or sex. Increases in accretion of carcass components (< 75%) induced by sustained-release pST were considerably less than those measured in the organs (liver, 157%; lungs, 748%). The pST-SR treatment resulted in elevated serum concentrations of pST and its mediators and improved efficiency and composition of gain.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献
994.
995.
996.
Two trials were conducted to determine the effect of induced molt on the reisolation of Mycoplasma gallisepticum (MG) from commercial leghorn hens that had been eyedrop-inoculated with MG at 10 weeks of age. Chickens were maintained in a conventional floored chicken house on dry litter through 100 weeks of age. At age 64 weeks, 4 days (Trial 1), and at 100 weeks (Trial 2), hens were swabbed and cultured for MG and then molted in biological isolation units. Swabs were again taken at the end of each molt. No difference was observed in the number of MG isolations between molted hens and controls that did not undergo molting. However, a significant decrease in MG isolations was observed in both trials from swabs obtained when hens were housed on dry litter floors as compared with swabs taken from the same hens after 18 days (Trial 1) or 21 days (Trial 2) of confinement in isolation units. 相似文献
997.
998.
999.
C. R. CLARKE † C. R. SHORT ¶ D. W. A. BOURNE‡ § E. A. USENIK 《Journal of veterinary pharmacology and therapeutics》1989,12(3):312-321
The purpose of this study was to characterize the pharmacokinetics of a subcutaneously implanted tissue-chamber model. Thermoplastic tissue chambers were implanted in the paralumbar fossae of six steers. Starting 30 days after implantation, the distribution of intravenously administered antipyrine and phenylbutazone into the tissue chambers was studied. These pharmacokinetic experiments were repeated 10 days later to determine the effect of time after implantation on tissue-chamber distribution. Fifty days after implantation, tissue chambers were drained of transudate, refilled with sterile saline and the rate of influx of endogenous urea, creatinine and albumin was measured. Delayed diffusion of antipyrine and phenylbutazone into tissue chambers was well described using a compartmental model in which tissue-chamber fluid represented the third of three compartments arranged in series. The distribution of antipyrine into tissue chambers was greater than that of phenylbutazone; an observation which is well correlated with the high degree of protein binding of phenylbutazone. There was no effect of time on the penetration of the two agents. Rapid diffusion of urea and creatinine and extremely slow influx of albumin into chambers showed that these chambers formed true interstitial compartments. 相似文献
1000.
1118 Friesian cows and 101 Friesian heifers were investigated in internal pelvic measurements and their relationships to external measurements. The mean of the pelvic vertical and the medium diagonally diameter of the pelvis are 19.8 cm and 18.3 cm. 363.9 square centimetres and 76.3 centimetres were found for the pelvic surface and pelvic circumference. The difference between the biggest and smallest pelvis was 295.0 square centimetres. Medium to high coefficiences of correlation were detected between the internal pelvic measurements but relationships between internal and external pelvic measurements were low. From determined external pelvic measurements only the hip breadth provides usefull informations of the pelvic shape. 相似文献