全文获取类型
收费全文 | 1419篇 |
免费 | 90篇 |
专业分类
林业 | 31篇 |
农学 | 19篇 |
基础科学 | 4篇 |
97篇 | |
综合类 | 491篇 |
农作物 | 37篇 |
水产渔业 | 110篇 |
畜牧兽医 | 659篇 |
园艺 | 24篇 |
植物保护 | 37篇 |
出版年
2021年 | 13篇 |
2020年 | 14篇 |
2019年 | 14篇 |
2017年 | 19篇 |
2016年 | 22篇 |
2015年 | 20篇 |
2014年 | 21篇 |
2013年 | 56篇 |
2012年 | 23篇 |
2011年 | 44篇 |
2010年 | 26篇 |
2009年 | 37篇 |
2008年 | 39篇 |
2007年 | 44篇 |
2006年 | 41篇 |
2005年 | 39篇 |
2004年 | 28篇 |
2003年 | 26篇 |
2002年 | 29篇 |
2001年 | 27篇 |
2000年 | 38篇 |
1999年 | 26篇 |
1998年 | 13篇 |
1995年 | 12篇 |
1994年 | 11篇 |
1992年 | 26篇 |
1991年 | 23篇 |
1990年 | 21篇 |
1989年 | 19篇 |
1988年 | 14篇 |
1987年 | 40篇 |
1986年 | 56篇 |
1985年 | 51篇 |
1984年 | 38篇 |
1983年 | 41篇 |
1982年 | 35篇 |
1981年 | 33篇 |
1980年 | 35篇 |
1979年 | 35篇 |
1978年 | 33篇 |
1977年 | 25篇 |
1976年 | 24篇 |
1975年 | 26篇 |
1974年 | 31篇 |
1973年 | 17篇 |
1972年 | 16篇 |
1971年 | 16篇 |
1970年 | 15篇 |
1969年 | 16篇 |
1966年 | 13篇 |
排序方式: 共有1509条查询结果,搜索用时 15 毫秒
91.
Robinson TL Sutherland IA Sutherland J 《Veterinary immunology and immunopathology》2007,115(1-2):160-165
Accurate quantification with real-time PCR requires the use of stable endogenous controls. Recently, there has been much debate concerning the stability of commonly used reference or housekeeping genes. To address this concern, a number of statistical approaches have been designed to analyse data and assist in determining the most appropriate reference genes for experimental comparisons. In this study, three programs, BestKeeper, Norm Finder, and geNorm were used to assess four candidate reference genes: 18S rRNA, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), acidic ribosomal protein large (RPLP0) and beta-actin, for use in expression profiling of individuals from divergent cattle genotypes subject to parasitic challenge with the cattle tick Boophilus microplus. Results demonstrated beta-actin and GAPDH were the most suitable reference genes in blood and could be used either individually or combined as an index to normalise data. RPLP0 was identified as the least stable gene, while 18S rRNA was omitted as being too highly expressed. As the recommendations on the most suitable reference genes varied between the programs, it is recommended that more than one should be utilised, to ensure the most robust experimental tools are selected. 相似文献
92.
93.
Summary Seedlings of a differential barley (Hordeum vulgare L.) series (21 genotypes) and of six check genotypes were used in the greenhouse to assess variation in virulence among 20 single-spore isolates of the net blotch pathogen. Pyrenophora teres Drechs. f.teres Smedeg., collected from various sites in Finland. The experiment was run twice and symptom expression was recorded on the first three leaves. Analysis of second leaf symptom scores from Run 1 indicated differences in virulence between isolates, all of which were pathogenic, and differential resistance among the barleys. The virulence of P. teres isolates appeared to be conditioned by the host barley from which the isolate derived; the average virulence of isolates collected from a susceptible host was greater than that of isolates collected from a less susceptible host. Results from Run 2 were similar regarding resistance within the barleys, but variation in virulence among the P. teres isolates was not consistent with that from Run 1. CI 9819 caries duplicate genes for resistance to P. teres (Rpt1b and Rpt1c), and CI 7548 possesses Rpt3d. Both genotypes were highly resistant to all isolates. The Rpt1a gene of Tifang (CI4407) conferred resistance to all isolates in Run 2, but only to about half of the isolates in Run 1. The checks, including two of the symptomatically most resistant Nordic barley genotypes, were universally susceptible during these stringent tests. No selective pressure has been placed on Finnish isolates of P. teres through previous deployment of major resistance genes, and it is speculated that any variation in virulence among isolates is likely to be due to a combination of evolutionary forces including, natural selection, random genetic drift and gene flow. 相似文献
94.
95.
Freshwater suspensions of pulp fiber in concentrations exceeding 1000 ppm at 15°C are acutely lethal to sockeye salmon fingerlings. Limited adaptation of such fish to fiber is possible but injury, at least in the short term, is irreversible. The acute lethality of various toxicants associated with industrial pulps is synergistically enhanced by the presence of fiber, and pulp storage up to 158 days at 15°C had no significant effect on the acute lethality. Highly purified fibers are less toxic in fresh than in sea water. The sensitivity to fiber of fish from two sources did not differ significantly. 相似文献
96.
A stability-indicating liquid chromatographic method is presented for determining sulfamethoxazole in tablets. The method uses a 10 micron silica column, an isooctane-methylene chloride-2-propanol-acetonitrile-glacial acetic acid (70 + 25 + 5 + 5 + 0.5) mobile phase, and photometric detection at 254 nm. Seven laboratories collaboratively studied this method on powdered composite samples prepared from commercial 500 and 1000 mg tablets and on an authentic tablet mixture containing 83.32% added sulfamethoxazole. Mean assay results for the 500 and 1000 mg tablets were 102.2 and 97.9% of declared, respectively (n = 4). The mean recovery value for the synthetic sample was 99.4% (n = 4). The pooled reproducibility standard deviation (SD) (coefficient of variation (CV)) and pooled repeatability SD (CV) were +/- 1.01 (1.01%) and +/- 0.96 (0.96%), respectively. These results were in good agreement with those obtained by the Associate Referee for the titration method of USP XX. The proposed method can also be used for monitoring the presence of sulfanilamide in sulfamethoxazole by increasing the proportions of both acetonitrile and 2-propanol in the mobile phase. The method has been adopted official first action. 相似文献
97.
98.
99.
Robinson AL 《Science (New York, N.Y.)》1976,191(4224):275-276
100.