全文获取类型
收费全文 | 223000篇 |
免费 | 14140篇 |
国内免费 | 907篇 |
专业分类
林业 | 23058篇 |
农学 | 13939篇 |
基础科学 | 2992篇 |
41281篇 | |
综合类 | 14746篇 |
农作物 | 17195篇 |
水产渔业 | 15963篇 |
畜牧兽医 | 79783篇 |
园艺 | 6183篇 |
植物保护 | 22907篇 |
出版年
2021年 | 2496篇 |
2020年 | 2882篇 |
2019年 | 3683篇 |
2018年 | 3920篇 |
2017年 | 4280篇 |
2016年 | 4712篇 |
2015年 | 4265篇 |
2014年 | 5626篇 |
2013年 | 16149篇 |
2012年 | 5473篇 |
2011年 | 7174篇 |
2010年 | 7101篇 |
2009年 | 7743篇 |
2008年 | 6645篇 |
2007年 | 5513篇 |
2006年 | 6251篇 |
2005年 | 5449篇 |
2004年 | 5337篇 |
2003年 | 5105篇 |
2002年 | 4413篇 |
2001年 | 4824篇 |
2000年 | 4471篇 |
1999年 | 4424篇 |
1998年 | 4006篇 |
1997年 | 4071篇 |
1996年 | 3810篇 |
1995年 | 4334篇 |
1994年 | 3714篇 |
1993年 | 3398篇 |
1992年 | 3495篇 |
1991年 | 3706篇 |
1990年 | 3346篇 |
1989年 | 3339篇 |
1988年 | 2936篇 |
1987年 | 2955篇 |
1986年 | 2863篇 |
1985年 | 3186篇 |
1984年 | 3089篇 |
1983年 | 2992篇 |
1982年 | 2594篇 |
1981年 | 2587篇 |
1980年 | 2560篇 |
1979年 | 2753篇 |
1978年 | 2544篇 |
1977年 | 2393篇 |
1976年 | 2265篇 |
1975年 | 2055篇 |
1974年 | 2126篇 |
1973年 | 2041篇 |
1972年 | 1773篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
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
93.
B. CAVALCASELLE 《EPPO Bulletin》1986,16(2):293-297
Des informations sur la biologie et la diffusion des principaux insectes nuisibles aux eucalyptus en Italie sont données, ainsi que sur l'importance de leurs dégats et sur les méthodes de lutte les plus couramment employées. En plus des quelques espèces polyphages, qui peuvent causer des dégats sporadiques, les phytophages vivant exclusivement aux dépens d'Eucalyptus spp. en Italie sont Phoracantha semipunctata, Gonipterus scutellatus et Ctenarytaina eucalypti. La première espèce est nuisible aux eucalyptus cultivès pour la production du bois et est répandue en Italie centrale et méridionale, en Sicile et en Sardaigne, alors que les deux autres espèces endommagent surtout les eucalyptus destinés aux marchés de fleurs (fleurs et rameaux) et ne sont prèsentes qu'en Ligurie occidentale. La lutte contre P. semipunctata est conduite par des interventions d'ordre sylvicultural, consistant essentiellement è recéper des peuplements sérieusement attaqués; le parasite oophage Patasson nitens, importé d'Afrique du Sud, permet de controler G. scutellatus alors que les larves de plusieurs syrphes prédatrices agissent efficacement contre C. eucalypti. 相似文献
94.
Twenty stifles (10 dogs) were studied for a period of 1 year after various lesions of the cranial cruciate ligament and medial meniscus were produced surgicaoy. Through serial arthroscopic evaluations, degenerative processes In stifles with a "torn" cranial cruciate ligament were documented. Intra-articular changes were minimal after partial meniscectomy and were severe after total meniscectomy. Multiple arthroscopies caused no demonstrable changes. 相似文献
95.
96.
A steam-dryer, designed and manufactured in Sweden, was evaluated for destroying Bursaphelenchus xylophilus in pine chips from southern USA. In a trial, pine chips were treated at different temperature and pressure regimes for 5 or 10min. The lowest time/temperature/pressure combination was to increase the vessel temperature from 85 to 104°C in 5 min at low pressure. Samples of pine chips were assayed for nematodes in laboratories in USA, Sweden, and Finland. No nematodes of any species were recovered from any of the treated pine-chip samples. Large and heterogeneous pieces of wood in the treated samples were also nematode-free. The apparatus was a prototype capable of handling about 400 kg h-1 . The final version would have to be able to process 100-200 th-1 . 相似文献
97.
Antiserum to a partially purified neuraminidase fromPasteurella multocida, type A:3, was adsorbed with protease-digestedP. multocida type 3 lipopolysaccharide (LPS) to remove LPS immunoreactivity. The LPS-adsorbed antineuraminidase caused a 77% reduction in the neuraminidase activity of homologousP. multocida in anin vitro enzyme neutralization test. All 14 mice passively immunized with the adsorbed antineuraminidase were protected against challenge infection with homologousP. multocida in a mouse protection test. Ten out of 14 mice in one group that received antisera containing antibodies to both neuraminidase and LPS were protected. In contrast, only 1 out of 14 mice that were immunized with pre-immune serum survived the challenge. These results suggest that antiserum toP. multocida neuraminidase was, at least partly, responsible for the protection observed in this study. Neuraminidase may be one of the immunogenic protective proteins present in aqueous extracts ofPasteurella multocida. 相似文献
98.
99.
T. D. G. Watson † D. Gaffhey C. T. Mooney† H. Thompson‡ C. J. Packard J. Shepherd 《The Journal of small animal practice》1992,33(5):207-212
Hyperchylomicronaemia was identified in a four-week-old Siamese kitten with lethargy, in-appetence, hindlimb ataxia and profound anaemia. The kitten was euthanased and at necropsy a thrombus was found occluding the caudal aorta. Two littermates later presented with lethargy, inappetence and hypertriglyceri-daemia which resolved after being weaned on to a low fat diet. A similar condition was subsequently diagnosed in a kitten born to the same sire but a different queen. The expression of hyperchylomicronaemia in two related litters was suggestive of an inherited, familial defect in the function of lipoprotein lipase (LPL). The activity of this enzyme was reduced in all three parents, the two recovered cases and two related, but apparently unaffected kittens, compared with a control group of unrelated cats belonging to the breeder. This reduction in activity was not attributable to defective activation of LPL by its serum cofactor apolipoprotein C-II or the presence in plasma of a factor that inhibited LPL. The gene that codes for LPL was examined by restriction fragment length polymorphism analysis using a human LPL cDNA probe. The results showed that the cat has a similar, but not identical, LPL gene to man. However, there were no differences in the restriction fragment patterns obtained from affected, unaffected and control animals. 相似文献
100.