全文获取类型
| 收费全文 | 8087篇 |
| 免费 | 451篇 |
| 国内免费 | 745篇 |
专业分类
| 林业 | 578篇 |
| 农学 | 642篇 |
| 基础科学 | 1095篇 |
| 856篇 | |
| 综合类 | 3726篇 |
| 农作物 | 341篇 |
| 水产渔业 | 136篇 |
| 畜牧兽医 | 990篇 |
| 园艺 | 154篇 |
| 植物保护 | 765篇 |
出版年
| 2024年 | 91篇 |
| 2023年 | 291篇 |
| 2022年 | 396篇 |
| 2021年 | 394篇 |
| 2020年 | 325篇 |
| 2019年 | 368篇 |
| 2018年 | 210篇 |
| 2017年 | 344篇 |
| 2016年 | 405篇 |
| 2015年 | 351篇 |
| 2014年 | 426篇 |
| 2013年 | 379篇 |
| 2012年 | 573篇 |
| 2011年 | 598篇 |
| 2010年 | 457篇 |
| 2009年 | 470篇 |
| 2008年 | 461篇 |
| 2007年 | 539篇 |
| 2006年 | 451篇 |
| 2005年 | 347篇 |
| 2004年 | 290篇 |
| 2003年 | 212篇 |
| 2002年 | 163篇 |
| 2001年 | 135篇 |
| 2000年 | 119篇 |
| 1999年 | 94篇 |
| 1998年 | 73篇 |
| 1997年 | 44篇 |
| 1996年 | 32篇 |
| 1995年 | 47篇 |
| 1994年 | 47篇 |
| 1993年 | 43篇 |
| 1992年 | 31篇 |
| 1991年 | 21篇 |
| 1990年 | 15篇 |
| 1989年 | 6篇 |
| 1988年 | 9篇 |
| 1987年 | 12篇 |
| 1986年 | 2篇 |
| 1985年 | 1篇 |
| 1981年 | 1篇 |
| 1980年 | 1篇 |
| 1978年 | 2篇 |
| 1956年 | 3篇 |
| 1955年 | 4篇 |
排序方式： 共有9283条查询结果，搜索用时 15 毫秒
1.
为了解决马铃薯致病疫霉侵染马铃薯导致其死亡,进而造成马铃薯单位种植产量低的问题。本文从拮抗菌入手,归纳分析细菌类拮抗菌中的主要拮抗菌中芽孢杆菌、假单胞菌和粘细菌对马铃薯致病疫霉的抑制作用。同时,在总结前人研究的基础上,笔者认为在拮抗菌应用方面,可以采用多对一的新型平板对峙筛菌模式来模拟复杂条件下拮抗菌的拮抗作用,以期得到稳定的拮抗菌;并指出应从定植能力和根际微生物影响方面对拮抗菌实际应用的可行性进行研究;此外,提出未来对拮抗菌抑制马铃薯致病疫霉的探究应从表型层面的研究深入到分子层面,以期能成功从源头找寻抑制马铃薯致病疫霉的答案。 相似文献
2.
病原微生物荚膜多糖的生物学功能 总被引：2，自引：1，他引：1
荚膜多糖（capsular polysaccharide，CPS）是一种广泛存在于细菌、支原体、部分真菌等菌体表面的碳水化合物。同时，荚膜多糖有助于菌体抵抗干燥和低温等不利环境，并通过在菌体表面形成物理屏障阻碍宿主补体的杀伤与吞噬作用。在长期多种应激-压力环境下，病原菌已进化出多种免疫逃避机制并促进宿主感染；在非病原微生物中，荚膜多糖可正向调节宿主免疫作用，并拮抗机体免疫因子，保护宿主免受病原菌引起的炎症性疾病。本文将结合本团队的相关研究工作，对荚膜多糖的结构、合成调控机制、生物学功能、免疫逃避机制和致病机制，特别是荚膜多糖正向调节宿主免疫系统及其应用潜力等方面作一综述，为病原菌致病机制的研究和疫病的有效防控提供参考依据。 相似文献
3.
The determination of tree age is an important issue for urban green planning, forestry and dendrology; finding non-destructive and quasi-non-destructive methods for this purpose is of great theoretical and practical importance. The resistance drilling method is quasi-non-destructive because the average diameter of an opening that remains after drilling does not exceed 3 mm. Do electrically recording resistance drills allow precise assessment of tree age? The aim of this study is to assess the accuracy of determining the number of tree rings based on an examination of this special kind of drilling resistance profiles for three tree species, the pine Pinus sylvestris L., the oak Quercus robur L., and the birch Betula pendula ROTH. In 2015 and 2016, 15 pine trees, 15 oak trees, and 15 birch trees were randomly selected. For each studied tree, a measurement was conducted using the electrically recording resistance drill IML-Resi E400 with a flat-tipped 1.5/3 mm steel needle (research sample), and an increment core was taken (reference sample). The drill used was not a real Resistograph®. The analysis of the E400-profiles underestimated the number of tree rings; the mean bias error (MBE) values were –6.5, –2.5, and –6.0 years for pine, oak, and birch, respectively. The proportion of investigated trees with less than five years difference between the research and reference samples varied from 38.4 (birch) to 66.7 (oak) percent. The accuracy of tree age determination was lowest for birch and highest for oak. The binomial generalised linear model (GLM) revealed that the most accurate tree age assessments were obtained from tree rings wider than 2 mm. The measurements clearly showed that the electrically recording resistance drill IML-Resi E400 enables a quick, although approximate, tree age assessment. Future research should concentrate on electronically regulating and recording drills, providing a higher spatial and signal resolution, and a stronger correlation to wood density. 相似文献
4.
伴随多元化时代的来临,用户的知识需求日益多元化、专业化,对图书馆服务提出了新的挑战。对智慧图书馆微观知识生态系统运行机理的研究,能够为新型知识服务提供理论基础,保障知识资源进行有效的优化整合,实现服务升级。文章在简要分析智慧图书馆微观知识生态系统四大要素的基础上,着重从社会发展、技术进步,知识富集、优化调整和需求驱动、服务升级三方面探讨其形成动因,重点分析智慧图书馆微观知识生态系统的生命周期,最后从合作、循环和保障三方面探讨其运行机理。 相似文献
5.
6.
Zidi Jin Long Liu Cheng Xu Chunchi Yan Shuo Li Tuoyu Geng Daoqing Gong 《Animal Science Journal》2021,92(1):e13672
Goose fatty liver is a specific type of nonalcoholic fatty liver that is protected from harmful effects associated with severe steatosis. Our previous findings suggest that suppression of the complement C5 may be relevant, but the mechanism is unclear. Therefore, in this study, we first verified the expression pattern of complement genes (including C5) during goose fatty liver formation and then determined the liver fat content and fatty acid composition by high-performance liquid chromatography (HPLC), followed by selecting the differential metabolites to treat HepG2, goose and mouse primary hepatocytes, aiming to explore the mechanism of C5 and inflammation suppression in goose fatty liver. The data confirmed the suppression of complement genes (including C5) in goose fatty livers. Moreover, fat content was significantly higher in fatty liver versus normal ones, with oleic acid and palmitic acid dominantly accounting for the difference. In line with this, high concentration of palmitate led to down regulation of C5 expression in goose primary hepatocytes whereas upregulation in mouse primary hepatocytes and HepG2 cells. In conclusion, regulation on C5 expression by fatty liver related factors including high level of palmitic acid may contribute to the protection of goose liver from severe hepatic steatosis. 相似文献
7.
WANG Hong 《东北农业大学学报(英文版)》2009,16(2):83-90
This paper discussed the definition and essential factors of green agriculture, including green ecological environment, green material energy input, application and the popularization of green agricultural technology, the green behavior of worker, green policy regulations guarantee, fund support, supply and the production of green agriculture products, as well as the concept of green agriculture, structural mechanism and function. And finally existing problems in present green agriculture and five suggestions of green agricultural sustainable develonment were proposed. 相似文献
8.
9.
感染白粉病小麦叶片细胞的超微变化 总被引：2，自引：0，他引：2
兰景华 《西南大学学报(自然科学版)》1992,14(4):289-291
小麦感染白粉病菌后,叶片叶绿体肿胀,双层膜不完整或消失,基粒片层排列疏松紊乱,细胞中出现许多由单层膜围成的大小不等的空胞和类似纤维状的膜状物,细胞核膜消失,质壁分离. 相似文献
10.