全文获取类型
收费全文 | 207903篇 |
免费 | 13733篇 |
国内免费 | 1374篇 |
专业分类
林业 | 23241篇 |
农学 | 14462篇 |
基础科学 | 3534篇 |
40228篇 | |
综合类 | 12698篇 |
农作物 | 17395篇 |
水产渔业 | 15672篇 |
畜牧兽医 | 66851篇 |
园艺 | 6484篇 |
植物保护 | 22445篇 |
出版年
2022年 | 1556篇 |
2021年 | 2732篇 |
2020年 | 3107篇 |
2019年 | 3861篇 |
2018年 | 3758篇 |
2017年 | 4285篇 |
2016年 | 4715篇 |
2015年 | 4531篇 |
2014年 | 5877篇 |
2013年 | 16443篇 |
2012年 | 5198篇 |
2011年 | 6740篇 |
2010年 | 7213篇 |
2009年 | 7925篇 |
2008年 | 6162篇 |
2007年 | 5058篇 |
2006年 | 5941篇 |
2005年 | 5099篇 |
2004年 | 4822篇 |
2003年 | 4554篇 |
2002年 | 3917篇 |
2001年 | 3964篇 |
2000年 | 3653篇 |
1999年 | 3842篇 |
1998年 | 3969篇 |
1997年 | 4021篇 |
1996年 | 3757篇 |
1995年 | 4284篇 |
1994年 | 3658篇 |
1993年 | 3363篇 |
1992年 | 3053篇 |
1991年 | 3177篇 |
1990年 | 2861篇 |
1989年 | 2828篇 |
1988年 | 2450篇 |
1987年 | 2504篇 |
1986年 | 2371篇 |
1985年 | 2807篇 |
1984年 | 2812篇 |
1983年 | 2749篇 |
1982年 | 2475篇 |
1981年 | 2446篇 |
1980年 | 2447篇 |
1979年 | 2347篇 |
1978年 | 2253篇 |
1977年 | 2169篇 |
1976年 | 2014篇 |
1975年 | 1756篇 |
1974年 | 1755篇 |
1973年 | 1694篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
72.
邹琳娜 《农业工程技术:农产品加工》2006,(9):15-16
植物健康综合管理系统(IpHM)在保证根系健康生长方面确实起到了作用。这就对种植者提出了挑战。植物营养调节、水分管理、根/冠生长管理的成败取决于是否有健康的根系和成分配比适当的栽培基质。[编者按] 相似文献
73.
74.
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
75.
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
76.
77.
78.
79.
Juan Pablo Zoffoli Bernardo A. Latorre Paulina Naranjo 《Postharvest Biology and Technology》2009,51(2):183-192
Over 54,600 ha of table grapes (Vitis vinifera), mainly cvs. ‘Thompson Seedless’, ‘Flame Seedless’ and ‘Redglobe’, are planted in Chile. Almost the entire production is exported to the USA, Europe, Asia, or one of several Latin American countries, which typically requires 15–40 d of maritime transportation. During this period, several physical, physiological, and pathological factors cause table grape deterioration. Because berry size is the main quality factor in international markets, farmers often overuse the growth regulators, gibberellic acid (GA3) and forchlorfenuron (CPPU), in an effort to increase berry size. We examined the effect of preharvest growth regulators on seedless (‘Thompson Seedless’, and ‘Ruby Seedless’) and seeded (‘Redglobe’) table grape cultivars during cold (0 °C) storage plus a shelf life period of 3 d at 20 °C. The overuse of GA3, eight instead of two GA3 applications on Thompson Seedless, and the use of one GA3 application on Redglobe and ‘Ruby Seedless’, increased berry pedicel thickness and lowered cuticle content but induced shatter and predisposed grapes to gray mold caused by Botrytis cinerea. In contrast, CPPU increased berry pedicel thickness and cuticle content but did not increase shatter or gray mold incidence. Clusters that were subjected to overuse of combined GA3 and CPPU were highly sensitive to shatter, had the thickest pedicel, and developed a high gray mold incidence during cold storage. Hairline, a fine cracking developed during cold storage, was induced on ‘Thompson Seedless’ and ‘Ruby Seedless’ by growth regulators, but no hairline occurred on ‘Redglobe’ table grapes. Therefore, berry quality during cold storage is greatly influenced by growth regulator management in the vineyard. 相似文献
80.