全文获取类型
收费全文 | 518篇 |
免费 | 47篇 |
专业分类
林业 | 41篇 |
农学 | 14篇 |
基础科学 | 1篇 |
51篇 | |
综合类 | 65篇 |
农作物 | 13篇 |
水产渔业 | 32篇 |
畜牧兽医 | 317篇 |
园艺 | 6篇 |
植物保护 | 25篇 |
出版年
2024年 | 3篇 |
2023年 | 5篇 |
2022年 | 6篇 |
2021年 | 8篇 |
2020年 | 11篇 |
2019年 | 23篇 |
2018年 | 17篇 |
2017年 | 22篇 |
2016年 | 12篇 |
2015年 | 9篇 |
2014年 | 20篇 |
2013年 | 20篇 |
2012年 | 43篇 |
2011年 | 48篇 |
2010年 | 19篇 |
2009年 | 16篇 |
2008年 | 37篇 |
2007年 | 41篇 |
2006年 | 29篇 |
2005年 | 25篇 |
2004年 | 24篇 |
2003年 | 23篇 |
2002年 | 25篇 |
2001年 | 3篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1987年 | 3篇 |
1985年 | 4篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1978年 | 2篇 |
1975年 | 3篇 |
1973年 | 2篇 |
1972年 | 4篇 |
1971年 | 3篇 |
1965年 | 2篇 |
1964年 | 3篇 |
1902年 | 3篇 |
1900年 | 1篇 |
1898年 | 1篇 |
1881年 | 1篇 |
排序方式: 共有565条查询结果,搜索用时 15 毫秒
561.
Schlaggar BL Brown TT Lugar HM Visscher KM Miezin FM Petersen SE 《Science (New York, N.Y.)》2002,296(5572):1476-1479
A critical issue in developmental cognitive neuroscience is the extent to which the functional neuroanatomy underlying task performance differs in adults and children. Direct comparisons of brain activation in the left frontal and extrastriate cortex were made in adults and children (aged 7 to 10 years) performing single-word processing tasks with visual presentation; differences were found in circumscribed frontal and extrastriate regions. Conceivably, these differences could be attributable exclusively to performance discrepancies; alternatively, maturational differences in functional neuroanatomy could exist despite similar performance. Some of the brain regions examined showed differences attributable to age independent of performance, suggesting that maturation of the pattern of regional activations for these tasks is incomplete at age 10. 相似文献
562.
Yu IM Zhang W Holdaway HA Li L Kostyuchenko VA Chipman PR Kuhn RJ Rossmann MG Chen J 《Science (New York, N.Y.)》2008,319(5871):1834-1837
Intracellular cleavage of immature flaviviruses is a critical step in assembly that generates the membrane fusion potential of the E glycoprotein. With cryo-electron microscopy we show that the immature dengue particles undergo a reversible conformational change at low pH that renders them accessible to furin cleavage. At a pH of 6.0, the E proteins are arranged in a herringbone pattern with the pr peptides docked onto the fusion loops, a configuration similar to that of the mature virion. After cleavage, the dissociation of pr is pH-dependent, suggesting that in the acidic environment of the trans-Golgi network pr is retained on the virion to prevent membrane fusion. These results suggest a mechanism by which flaviviruses are processed and stabilized in the host cell secretory pathway. 相似文献
563.
Rodrigo C. Bicalho Heather M. Mayers Soon Hon Cheong Brielle V. Rosa Charles L. Guard 《The Canadian veterinary journal. La revue veterinaire canadienne》2009,50(4):393-396
Cases of omasal dilation and displacement in 4 dairy cows are described. The disease was initially diagnosed by a combination of history and clinical signs that included right-sided abdominal distension, rectal palpation, and decreased milk production. The condition was confirmed by laparotomy or necropsy. 相似文献
564.
Brady H Lamb MM Sokol RJ Ross CA Seifert JA Rewers MJ Norris JM 《Public health nutrition》2007,10(7):712-718
BACKGROUND: While adult populations have been well described in terms of nutritional status, such as the concentration of nutrient biomarkers, little work has been done in healthy paediatric populations. OBJECTIVE: The primary objective of this analysis was to explore the determinants of plasma micronutrients in a group of healthy infants and children. DESIGN: The Diabetes Autoimmunity Study in the Young (DAISY) has enrolled 1433 newborns at increased risk for type 1 diabetes in Denver, Colorado. A representative random sample of 257 children from the DAISY cohort between the ages of 9 months and 8 years with a total of 815 clinic visits over time was used in this analysis. Annual dietary intake was assessed over time with Willett food-frequency questionnaires that were validated in this population. Environmental tobacco smoke (ETS) was assessed using a validated survey. Plasma samples were tested for vitamins, carotenoids and total lipids. Predictors of plasma micronutrients were evaluated using mixed models for longitudinal data, while adjusting for age, human leukocyte antigen genotype, type 1 diabetes family history and other potential confounders and covariates. RESULTS: Increased micronutrient intake was associated with increased levels of their respective plasma nutrient, with the exception of gamma-tocopherol. Independent of dietary intake, levels of alpha- and beta-carotene and beta-cryptoxanthin were significantly lower, and gamma-tocopherol was significantly higher, in children who were exposed to ETS. CONCLUSION: Dietary intake predicts plasma micronutrient levels. Exposure to ETS potentially could have negative health effects in this young population. 相似文献
565.