全文获取类型
| 收费全文 | 114444篇 |
| 免费 | 5745篇 |
| 国内免费 | 80篇 |
专业分类
| 林业 | 5388篇 |
| 农学 | 3760篇 |
| 基础科学 | 740篇 |
| 13047篇 | |
| 综合类 | 20300篇 |
| 农作物 | 4529篇 |
| 水产渔业 | 5285篇 |
| 畜牧兽医 | 59458篇 |
| 园艺 | 1334篇 |
| 植物保护 | 6428篇 |
出版年
| 2018年 | 1424篇 |
| 2017年 | 1527篇 |
| 2016年 | 1487篇 |
| 2015年 | 1286篇 |
| 2014年 | 1533篇 |
| 2013年 | 4061篇 |
| 2012年 | 2902篇 |
| 2011年 | 3504篇 |
| 2010年 | 2298篇 |
| 2009年 | 2183篇 |
| 2008年 | 3293篇 |
| 2007年 | 3275篇 |
| 2006年 | 3180篇 |
| 2005年 | 2993篇 |
| 2004年 | 2830篇 |
| 2003年 | 2869篇 |
| 2002年 | 2730篇 |
| 2001年 | 3486篇 |
| 2000年 | 3364篇 |
| 1999年 | 2693篇 |
| 1998年 | 1134篇 |
| 1997年 | 1072篇 |
| 1995年 | 1200篇 |
| 1994年 | 1068篇 |
| 1992年 | 2358篇 |
| 1991年 | 2554篇 |
| 1990年 | 2672篇 |
| 1989年 | 2586篇 |
| 1988年 | 2442篇 |
| 1987年 | 2388篇 |
| 1986年 | 2345篇 |
| 1985年 | 2298篇 |
| 1984年 | 1912篇 |
| 1983年 | 1598篇 |
| 1982年 | 1170篇 |
| 1981年 | 1062篇 |
| 1979年 | 1802篇 |
| 1978年 | 1429篇 |
| 1977年 | 1205篇 |
| 1976年 | 1201篇 |
| 1975年 | 1272篇 |
| 1974年 | 1638篇 |
| 1973年 | 1588篇 |
| 1972年 | 1653篇 |
| 1971年 | 1567篇 |
| 1970年 | 1530篇 |
| 1969年 | 1311篇 |
| 1968年 | 1101篇 |
| 1967年 | 1259篇 |
| 1966年 | 1096篇 |
排序方式： 共有10000条查询结果，搜索用时 15 毫秒
41.
H E Kennedy S J McCullough D Graham J Cassidy F E Malone W A Ellis 《Journal of veterinary diagnostic investigation》2001,13(1):30-35
Two serological tests (indirect immunofluorescence and enzyme-linked immunosorbent assay) were developed for the detection of fetal antibody to Chlamydia psittaci. Fetal blood and thoracic fluid from 126 field cases of suspected ovine chlamydial abortion were examined using both tests. Placenta and fetal tissues (lung, liver, and kidney) from the same animals were also examined by the following conventional diagnostic methods: isolation in McCoy cells, detection of chlamydial lipopolysaccharide (LPS), modified Ziehl-Nielsen staining, and direct fluorescent antibody staining of chlamydia in frozen cryostat sections. Seventy cases were positive by fetal serology, and of these, 68 were also positive by isolation and/or LPS detection. The remaining 56 cases had negative fetal serology, and of these, 39 were positive by isolation and/or LPS detection. Results indicate that fetal serology, although less sensitive than either isolation in McCoy cells or detection of chlamydial LPS antigen, may be of particular use when placenta is not available. 相似文献
42.
43.
44.
Various combinations of reoviruses and coccidia were studied to see if interactions would occur. Two reoviruses were used: virus 2035, a moderate to low pathogen, and virus 2177, a nonpathogen. Coccidia used were Eimeria acervulina, E. mitis, and E. maxima at dosages of 10(3) or 10(4) sporulated oocysts/chick and E. brunetti at 10(4) sporulated oocysts/chick. In Hubbard-Hubbard cockerels, a combination of virus 2035 and E. acervulina (10(4) oocysts/chick) or E. maxima (10(3) oocysts/chick) significantly (P less than or equal to 0.05) increased the frequency of stunting (% of chicks with body weight less than 80% of controls) and further depressed weight gain over that seen with either virus or coccidia alone. Conversely, virus 2177 ameliorated the same effects in Shaver-Arbor Acre cockerels given 10(4) oocysts/chick of E. mitis or E. maxima. The interaction could not be attributed to changes in the degree of coccidial infection based on oocyst production. Reovirus did not generally change the effect of coccidia on levels of plasma pigment and plasma protein. In Hubbard-Hubbard cockerels, coccidia-induced effects were not ameliorated by virus 2177, suggesting that breed difference in interaction can be expected. 相似文献
45.
Praveen C. Verma Debasis Chakrabarty Satya Narayan Jena Devesh K. Mishra Pradhyumna K. Singh Samir V. Sawant Rakesh Tuli 《Industrial Crops and Products》2009,29(2-3):581-589
Vanilla is a large genus of about 110 species in the orchid family (Orchidaceae), including the species Vanilla planifolia from which commercial vanilla flavoring is derived. Since most species of vanilla are considered rare and endangered there is an urgent need to conserve them through genetic analysis and propagation/conservation studies on this crop.The present study investigated the genetic diversity among nine leafy- and leaf-less Vanilla species employing 30 decamer RAPD primers and 10 ISSR primers. The species under study were diverse and displayed a range of variability (0–66% and 0–81% for RAPD and ISSR, respectively). A total of 154 RAPD polymorphic markers (83.24%, h = 0.378) and 93 ISSR polymorphic markers (86.11%, h = 0.363) were used to generate a genetic similarity matrix followed by the cluster analysis. Specific groupings were revealed by each cluster analysis with slight variation between two different markers. Among the nine species studied, V. planifolia, Vanilla aphylla and Vanilla tahitensis revealed very low level of variation within their collections, thus indicating a narrow genetic base. The large genetic distance of Vanilla andamanica from other species suggests its different origin. A close genetic affinity was observed between the pairs V. planifolia, V. tahitensis and Vanilla albida, V. aphylla. These are the first comparative results for RAPD and ISSR reporting inter-relationship among nine cultivated, wild and hybrid Vanilla species. 相似文献
46.
47.
48.
49.
50.