全文获取类型
收费全文 | 6429篇 |
免费 | 358篇 |
国内免费 | 842篇 |
专业分类
林业 | 556篇 |
农学 | 531篇 |
基础科学 | 1498篇 |
1220篇 | |
综合类 | 3159篇 |
农作物 | 135篇 |
水产渔业 | 152篇 |
畜牧兽医 | 213篇 |
园艺 | 47篇 |
植物保护 | 118篇 |
出版年
2024年 | 54篇 |
2023年 | 219篇 |
2022年 | 306篇 |
2021年 | 316篇 |
2020年 | 266篇 |
2019年 | 277篇 |
2018年 | 156篇 |
2017年 | 226篇 |
2016年 | 264篇 |
2015年 | 247篇 |
2014年 | 349篇 |
2013年 | 286篇 |
2012年 | 487篇 |
2011年 | 533篇 |
2010年 | 488篇 |
2009年 | 427篇 |
2008年 | 367篇 |
2007年 | 408篇 |
2006年 | 366篇 |
2005年 | 352篇 |
2004年 | 294篇 |
2003年 | 179篇 |
2002年 | 144篇 |
2001年 | 119篇 |
2000年 | 87篇 |
1999年 | 73篇 |
1998年 | 64篇 |
1997年 | 58篇 |
1996年 | 45篇 |
1995年 | 36篇 |
1994年 | 20篇 |
1993年 | 27篇 |
1992年 | 19篇 |
1991年 | 20篇 |
1990年 | 14篇 |
1989年 | 14篇 |
1988年 | 12篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1984年 | 1篇 |
1956年 | 2篇 |
排序方式: 共有7629条查询结果,搜索用时 31 毫秒
71.
为初步鉴定并挖掘出猪戊型肝炎病毒(Hepatitis E virus,HEV)ORF3蛋白影响HepG2细胞核黄素代谢信号通路的lncRNA-mRNA调控网络,本试验通过构建腺病毒过表达载体,制备高滴度过表达腺病毒,介导猪 HEV-ORF3在HepG2细胞中实现过表达。Western blotting检测ORF3蛋白过表达成功后,运用lncRNA高通量组学测序,筛选出差异表达的lncRNA并进行靶向差异基因预测,对lncRNA靶向差异基因进行GO功能和KEGG通路富集分析,初步鉴定出与核黄素代谢信号通路相关的lncRNA-mRNA调控网络。Western blotting结果显示,在约为12 ku处出现目的条带,说明成功实现腺病毒介导猪HEV-ORF3在HepG2细胞中过表达。lncRNA高通量组学测序结果显示,共发现102个显著差异表达lncRNAs表达量上调,80个显著差异表达lncRNAs表达量下调。GO功能和KEGG通路富集分析显示,初步挖掘出lncRNA(MSTRG.13995.2)和lncRNA(MSTRG.1960.1)可能是与核黄素代谢信号通路相关的显著差异表达lncRNA,分别通过顺式调控其靶向基因APC-5和FLAD1来影响核黄素代谢信号通路。本试验初步鉴定出lncRNA(MSTRG.13995.2)-APC5和lncRNA(MSTRG.1960.1)-FLAD1可能是影响HepG2细胞核黄素代谢信号通路的lncRNA-mRNA调控网络。 相似文献
72.
介绍了LM-BP神经网络模型的原理及算法和模型的优点。针对实际水质评价问题,利用随机内插方法在地表水环境质量分级标准阈值间生成训练样本和检验样本,建立了新乡市卫河地面水环境质量综合评价的LM-BP神经网络模型,将模型应用于卫河2011年3月份、9月份的水质评价,并与单因子评价法、模糊综合评价法进行了比较分析。实验结果表明该模型设计合理,泛化能力强,收敛速度快,算法稳定,推导严谨,有较充分的理论依据,应用于水质评价具有其合理性、实用性和有效性,适用于作深入的水环境质量分析。 相似文献
73.
74.
75.
76.
77.
《Journal of Cereal Science》2014,59(3):451-456
Brans of 23 traditional and 12 improved (both red and white) rice varieties in Sri Lanka were screened for anti-amylase and anti-glycation activities in vitro. Varieties which showed the highest inhibitory activities at screening were further investigated for anti-glucosidase and glycation reversing as anti-diabetic properties. The same varieties were studied for selected antioxidant properties. Significantly high anti-amylase and anti-glycation activities were observed for bran extracts of red varieties compared to white varieties at screening. Traditional red rice varieties, Masuran, Sudu Heeneti, Dik Wee and Goda Heeneti, exhibited significant and dose dependent anti-amylase, anti-glycation and glycation reversing activities. These varieties also showed marked antioxidant properties. It is concluded that brans of Sri Lankan traditional red rice varieties Masuran, Sudu Heeneti, Dik Wee and Goda Heeneti may be potential food supplements for diabetes. 相似文献
78.
An algorithm of fault section diagnosis based on topology identification for distribution networks is presented. By decomposing the topologic matrix which describing the distribution network into two parts,one part only contain the complex coupling factor ,and the other ignore the complex coupling factor. Using this method, the fault zones in distribution network can be identified and isolated efficiently, and the vertexes of the zones can also be identified automatically. This approach adapts to the changefully network structures. 相似文献
79.
Chen HuaZhou Jiaqi 《保鲜与加工》1990,(4):1-6
Based on the maximum flow principle about networks, a network flow approach to reliability evaluation in large scale netwerks ty mixing inereasing flow with decreasing flow is proposed in this paper.This approach gets the initial flow of each branch in a r.etwork associated with a state of the retwork by decreasing flows of some branches correlative to another state of the network.As a result, the number of flow compute required can be reduced enormously.The numerical example shows that the approach is powerful. The comparison of this approach with the minimal cutset one is also given in this paper. 相似文献
80.
As the important method and instrument of agile manufacture,the technology of distributed collaborative design and manufacturing has become the hotspot of manufacturing. The basic concept and key technologies of IP_VPN are introduced in this paper,and a collaborative design network model based on IP_VPN is presented. Distributed collaborative design is a multi_user,multitask involved system, which is consisted of lots of collaborative processs,so the network security is the key of distributed collaborative design. We research on the security of collaborative design network based on IP_VPN, hence get a conclusion:we can construct an economical?practical and secure collaborative design network system by the application of data encryption,user authentication and access control based on the role,etc. 相似文献