全文获取类型
| 收费全文 | 217839篇 |
| 免费 | 13760篇 |
| 国内免费 | 638篇 |
专业分类
| 林业 | 23027篇 |
| 农学 | 13959篇 |
| 基础科学 | 2949篇 |
| 41511篇 | |
| 综合类 | 13076篇 |
| 农作物 | 17005篇 |
| 水产渔业 | 15815篇 |
| 畜牧兽医 | 75764篇 |
| 园艺 | 6212篇 |
| 植物保护 | 22919篇 |
出版年
| 2021年 | 2406篇 |
| 2020年 | 2850篇 |
| 2019年 | 3659篇 |
| 2018年 | 3951篇 |
| 2017年 | 4321篇 |
| 2016年 | 4708篇 |
| 2015年 | 4212篇 |
| 2014年 | 5569篇 |
| 2013年 | 16181篇 |
| 2012年 | 5237篇 |
| 2011年 | 7031篇 |
| 2010年 | 7081篇 |
| 2009年 | 7733篇 |
| 2008年 | 6384篇 |
| 2007年 | 5451篇 |
| 2006年 | 6061篇 |
| 2005年 | 5250篇 |
| 2004年 | 5154篇 |
| 2003年 | 4892篇 |
| 2002年 | 4234篇 |
| 2001年 | 4437篇 |
| 2000年 | 4105篇 |
| 1999年 | 4146篇 |
| 1998年 | 3976篇 |
| 1997年 | 4037篇 |
| 1996年 | 3766篇 |
| 1995年 | 4300篇 |
| 1994年 | 3692篇 |
| 1993年 | 3389篇 |
| 1992年 | 3322篇 |
| 1991年 | 3465篇 |
| 1990年 | 3180篇 |
| 1989年 | 3148篇 |
| 1988年 | 2694篇 |
| 1987年 | 2770篇 |
| 1986年 | 2684篇 |
| 1985年 | 3052篇 |
| 1984年 | 3029篇 |
| 1983年 | 2945篇 |
| 1982年 | 2567篇 |
| 1981年 | 2521篇 |
| 1980年 | 2532篇 |
| 1979年 | 2747篇 |
| 1978年 | 2497篇 |
| 1977年 | 2378篇 |
| 1976年 | 2270篇 |
| 1975年 | 2069篇 |
| 1974年 | 2067篇 |
| 1973年 | 1996篇 |
| 1972年 | 1675篇 |
排序方式： 共有10000条查询结果，搜索用时 15 毫秒
101.
102.
Detection of a broad range of potato viruses in a single assay by mechanical inoculation of herbaceous test plants 总被引：1，自引：0，他引：1
To optimize mechanical inoculation of test plants as part of the regulated post-entry quarantine testing of stolon- and tuber-forming Solanum spp. (including potato), nine test plant species have been screened for their ability to detect 22 potato-infecting viruses. These included all the common mechanically transmissible potato viruses and most of the viruses found in potato incidentally. The symptoms observed after mechanical inoculation are shown for each combination of test plant species and virus. Under given conditions, Nicotiana occidentalis -P1 and Nicotiana hesperis -67A were found to detect reliably 20 and 18 out of 22 viruses respectively. These and former results on the seed-transmissible viruses and Andean potato mottle virus demonstrate that these Nicotiana species are very suitable for post-entry quarantine testing. Addition of either Chenopodium amaranticolor or Chenopodium quinoa to these two species may slightly extend the range of viruses. Therefore, using C. amaranticolor / C. quinoa , N. hesperis -67A and N. occidentalis -P1 for the biological screening of imported Solanum spp. will improve both the efficiency and the quality of post-entry quarantine testing. 相似文献
103.
104.
Abstract The potential utility of pelvic fin rays as ageing structures was evaluated for southern US muskellunge Esox masquinongy Mitchill populations by comparing age estimates among three readers and against cleithrum estimates, and by comparing observed length changes of tagged fish with changes predicted from growth equations based on pelvic fin ray age estimates. Mean coefficient of variation in age estimates among all readers and between the two readers with prior ageing experience was 17.8% and 5.6%, respectively. Exact and within 1-year agreement rates between pelvic fin rays and cleithra were 76% and 100%, respectively. Mean (± 2 SE) estimated absolute error between observed and predicted length changes for 13 tagged muskellunge was 30 ± 14 mm. This evaluation indicated that pelvic fin rays may prove to be a useful, non-lethal method for ageing muskellunge in southern US waters. Validation studies are still needed to ensure that growth rings form consistently throughout fish's life span. 相似文献
105.
本介绍了对棉籽粕养分含量的最新调查结果，数据包括了平均值和变异范围。本应该对考虑在日粮中应用棉籽粕的营养师具有价值。 相似文献
106.
107.
108.
109.
110.
B. Feuchter 《European Journal of Forest Research》1869,13(1):360-360
Ohne Zusammenfassung 相似文献