全文获取类型
收费全文 | 1257篇 |
免费 | 74篇 |
专业分类
林业 | 50篇 |
农学 | 24篇 |
基础科学 | 7篇 |
118篇 | |
综合类 | 264篇 |
农作物 | 46篇 |
水产渔业 | 43篇 |
畜牧兽医 | 672篇 |
园艺 | 22篇 |
植物保护 | 85篇 |
出版年
2019年 | 22篇 |
2018年 | 12篇 |
2017年 | 19篇 |
2016年 | 18篇 |
2015年 | 19篇 |
2014年 | 22篇 |
2013年 | 32篇 |
2012年 | 39篇 |
2011年 | 46篇 |
2010年 | 25篇 |
2009年 | 19篇 |
2008年 | 41篇 |
2007年 | 29篇 |
2006年 | 48篇 |
2005年 | 43篇 |
2004年 | 33篇 |
2003年 | 37篇 |
2002年 | 29篇 |
2001年 | 29篇 |
2000年 | 26篇 |
1999年 | 27篇 |
1998年 | 14篇 |
1997年 | 15篇 |
1996年 | 14篇 |
1995年 | 20篇 |
1994年 | 18篇 |
1993年 | 11篇 |
1992年 | 27篇 |
1991年 | 30篇 |
1990年 | 26篇 |
1989年 | 30篇 |
1988年 | 22篇 |
1987年 | 14篇 |
1986年 | 17篇 |
1985年 | 26篇 |
1984年 | 24篇 |
1983年 | 16篇 |
1979年 | 16篇 |
1978年 | 16篇 |
1977年 | 15篇 |
1975年 | 15篇 |
1974年 | 16篇 |
1973年 | 12篇 |
1972年 | 18篇 |
1971年 | 10篇 |
1970年 | 14篇 |
1969年 | 12篇 |
1968年 | 10篇 |
1967年 | 11篇 |
1966年 | 10篇 |
排序方式: 共有1331条查询结果,搜索用时 15 毫秒
61.
62.
63.
Dysentery lasting 4-8 days was produced in five 4-day-old colostrum-fed calves, after inoculation with an atypical strain of Escherichia coli S102-9; peak excretion of S102-9 occurred during the period of dysentery. Two calves were killed when clinical signs were most severe and bacteria were seen attached to the surfaces of enterocytes in the large intestine; microscopic lesions were seen in these areas. The lesions were identical to those previously reported in a natural outbreak of dysentery in calves, from which E. coli S102-9 was isolated, and to those seen in gnotobiotic calves experimentally infected with S102-9. Reinfection of the three surviving calves 16-20 days later with S102-9 and primary infection of two calves aged 24 and 51 days did not cause dysentery. Four of 659 coliforms isolated from field outbreaks of calf diarrhoea resembled the atypical strain S102-9. These four isolates and S102-9 did not produce heat-stable enterotoxin, but all produced a toxin cytopathic for Vero and HeLa cells. Two of the four isolates were inoculated alone into 4-day-old gnotobiotic calves deprived of colostrum; neither calf developed dysentery but microscopic lesions identical to those produced by S102-9 were detected in the large intestines of both animals. 相似文献
64.
65.
E.A. Pinkard C. Mohammed C.L. Beadle M.F. Hall D. Worledge A. Mollon 《Forest Ecology and Management》2004,200(1-3):263-277
Detailed studies have been undertaken to define pruning regimes for Eucalyptus nitens, but little is known of E. globulus responses to pruning although this is a more commonly planted species. This paper describes experiments that aimed to identify (a) levels of pruning that reduce E. globulus growth, (b) physiological processes contributing to those growth responses, (c) the incidence of decay and factors influencing decay incidence following pruning of E. globulus, and (d) comparative responses of E. nitens and E. globulus to live branch pruning. Results of a field experiment indicated that removal of between 30 and 50% of the crown length was appropriate for E. globulus plantations verging on canopy closure. The significant reduction in height growth associated with removal of 50 or 70% of crown length suggested pruning should remain below 50% of crown length if reduced stem growth of pruned trees was to be avoided. Stem volume was only significantly reduced over the period of the experiment by 70% pruning, but it was estimated that standing volume following removal of 50% of crown length would be reduced by 82 m3 ha−1 over a 20-year rotation if there were no other silvicultural interventions. The growth responses observed were probably related to large reductions in leaf area following 50 or 70% removal of crown length. Trees responded to pruning by changing patterns of biomass partitioning to favour stem growth at the expense of branch growth. A glasshouse study determined that light-saturated net CO2 uptake (Amax) increased following pruning. E. nitens seedlings had both a higher baseline Amax and higher Amax following pruning than did E. globulus, which could partially explain the greater effect of pruning on E. globulus growth than has been observed for E. nitens in other studies. This result, as well as apparently different patterns of foliage distribution through the crowns of E. globulus and E. nitens, suggested that models of pruning responses need to be parameterised for both species. In addition, a more conservative pruning regime may be appropriate for E. globulus than E. nitens. Pruning increased the frequency of branch traces with decay infection, and there was a trend towards increasing decay outbreaks with increasing pruning severity. Decay outbreaks were more likely to occur following pruning of high angle or larger diameter branches. 相似文献
66.
Factors affecting urine reagent strip blood results in dogs and nonhuman primates and interpretation of urinalysis in preclinical toxicology studies: a Multi‐Institution Contract Research Organization and BioPharmaceutical Company Perspective
下载免费PDF全文
![点击此处可从《Veterinary clinical pathology / American Society for Veterinary Clinical Pathology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
67.
J.A. Hall M. Yerramilli E. Obare M. Yerramilli D.E. Jewell 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2014,28(6):1676-1683
Background
Symmetric dimethylarginine (SDMA) has been shown to be an accurate and precise biomarker for calculating estimated glomerular filtration rate (GFR) in humans, as well as a more sensitive biomarker than serum creatinine concentration (sCr) for assessing renal dysfunction.Objectives
The purpose of this retrospective study was to report on the utility of measuring serum SDMA concentrations in cats for detection of chronic kidney disease (CKD) before diagnosis by conventional measurement of sCr.Animals
Chronic kidney disease cats (n = 21) included those persistently azotemic for ≥3 months (n = 15), nonazotemic cats with GFR >30% decreased from median GFR of normal cats (n = 4), and nonazotemic cats with calcium oxalate kidney stones (n = 2). Healthy geriatric cats (n = 21) were selected from the same colony.Methods
Symmetric dimethylarginine concentrations (liquid chromatography‐mass spectroscopy) and sCr (enzymatic colorimetry) were determined retrospectively from historical data or banked serum samples in azotemic cats or at the time GFR (iohexol clearance) was measured in nonazotemic cats.Results
Serum SDMA (r = −0.79) and sCr (r = −0.77) concentrations were significantly correlated to GFR (both P < .0001). Symmetric dimethylarginine became increased before sCr in 17/21 cats (mean, 17.0 months; range, 1.5–48 months). Serum SDMA had higher sensitivity (100%) compared with sCr (17%), but lower specificity (91% versus 100%) and positive predictive value (86% versus 100%).Conclusion and Clinical Importance
Using serum SDMA as a biomarker for CKD allows earlier detection of CKD in cats compared with sCr, which may be desirable for initiating renoprotective interventions that slow progression of CKD. 相似文献68.
Helle Bielefeldt-Ohmann Natalie A Prow Wenqi Wang Cindy SE Tan Mitchell Coyle Alysha Douma Jody Hobson-Peters Lisa Kidd Roy A Hall Nikolai Petrovsky 《Veterinary research》2014,45(1)
In 2011, following severe flooding in Eastern Australia, an unprecedented epidemic of equine encephalitis occurred in South-Eastern Australia, caused by Murray Valley encephalitis virus (MVEV) and a new variant strain of Kunjin virus, a subtype of West Nile virus (WNVKUN). This prompted us to assess whether a delta inulin-adjuvanted, inactivated cell culture-derived Japanese encephalitis virus (JEV) vaccine (JE-ADVAX™) could be used in horses, including pregnant mares and foals, to not only induce immunity to JEV, but also elicit cross-protective antibodies against MVEV and WNVKUN. Foals, 74–152 days old, received two injections of JE-ADVAX™. The vaccine was safe and well-tolerated and induced a strong JEV-neutralizing antibody response in all foals. MVEV and WNVKUN antibody cross-reactivity was seen in 33% and 42% of the immunized foals, respectively. JE-ADVAX™ was also safe and well-tolerated in pregnant mares and induced high JEV-neutralizing titers. The neutralizing activity was passively transferred to their foals via colostrum. Foals that acquired passive immunity to JEV via maternal antibodies then were immunized with JE-ADVAX™ at 36–83 days of age, showed evidence of maternal antibody interference with low peak antibody titers post-immunization when compared to immunized foals of JEV-naïve dams. Nevertheless, when given a single JE-ADVAX™ booster immunization as yearlings, these animals developed a rapid and robust JEV-neutralizing antibody response, indicating that they were successfully primed to JEV when immunized as foals, despite the presence of maternal antibodies. Overall, JE-ADVAX™ appears safe and well-tolerated in pregnant mares and young foals and induces protective levels of JEV neutralizing antibodies with partial cross-neutralization of MVEV and WNVKUN. 相似文献
69.
T.C. Bray S.J.G. Hall M.W. Bruford 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2014,131(1):19-26
Investigation of historic population processes using molecular data has been facilitated by the use of approximate Bayesian computation (ABC), which enables the consideration of multiple alternative demographic scenarios. The Lincoln Red cattle breed provides a relatively simple example of two well‐documented admixture events. Using molecular data for this breed, we found that structure did not resolve very low (<5% levels) of introgression, possibly due to sampling limitations. We evaluated the performance of two ABC approaches (2BAD and DIYABC) against those of two earlier methodologies, ADMIX and LEADMIX, by comparing their interpretations with the conclusions drawn from herdbook analysis. The ABC methods gave credible values for the proportions of the Lincoln Red genotype that are attributable to Aberdeen Angus and Limousin, although estimates of effective population size and event timing were not realistic. We suggest ABC methods are a valuable supplement to pedigree‐based studies but that the accuracy of admixture determination is likely to diminish with increasing complexity of the admixture scenario. 相似文献
70.