全文获取类型
收费全文 | 1543篇 |
免费 | 118篇 |
国内免费 | 159篇 |
专业分类
林业 | 140篇 |
农学 | 168篇 |
基础科学 | 91篇 |
200篇 | |
综合类 | 772篇 |
农作物 | 62篇 |
水产渔业 | 41篇 |
畜牧兽医 | 215篇 |
园艺 | 58篇 |
植物保护 | 73篇 |
出版年
2024年 | 5篇 |
2023年 | 22篇 |
2022年 | 44篇 |
2021年 | 62篇 |
2020年 | 55篇 |
2019年 | 61篇 |
2018年 | 44篇 |
2017年 | 77篇 |
2016年 | 94篇 |
2015年 | 85篇 |
2014年 | 119篇 |
2013年 | 109篇 |
2012年 | 144篇 |
2011年 | 114篇 |
2010年 | 127篇 |
2009年 | 102篇 |
2008年 | 62篇 |
2007年 | 107篇 |
2006年 | 85篇 |
2005年 | 44篇 |
2004年 | 43篇 |
2003年 | 35篇 |
2002年 | 26篇 |
2001年 | 33篇 |
2000年 | 19篇 |
1999年 | 15篇 |
1998年 | 10篇 |
1997年 | 13篇 |
1996年 | 5篇 |
1995年 | 14篇 |
1994年 | 9篇 |
1993年 | 4篇 |
1992年 | 7篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1981年 | 1篇 |
1976年 | 1篇 |
1956年 | 2篇 |
排序方式: 共有1820条查询结果,搜索用时 31 毫秒
21.
22.
In the nonlinear analysis, stress state and stress history are in respect to stress-strain law. It is needed to store its stress history in calculation and analysis. Based on stress state of material, Object-Oriented Programming method used has the advantage in storing stress history intelligently. It overcomes the shortcoming of Process-Oriented Programming method, saves space and reduces difficulty of programming. Based on the three-dimension solid element, how to design for Object-Oriented nonlinear FEM Program. 相似文献
23.
Summary During experiments, which are being carried out to study the factors which control the process of adventitious bud formation in vivo on detached leaves of Chrysanthemum morifolium
Ram, adventitious shoots were produced from leaves, irradiated with 500 rad of X-rays. The most important but disadvantageous result was that the majority of the adventitious shoots proved to be of a chimeral nature and obviously developed from more than one cell.An in vitro adventitious bud technique was developed using different types of explants. Pedicel segments regenerated the highest number of adventitious shoots and, moreover, they developed faster as compared to explants of young flower heads or leaves. The mutants produced by irradiating the various explants were almost exclusively of a solid (non-chimeral) nature. In addition, histological observations suggest that single epidermal cells are involved in the initiation of the adventitious shoot apices.The optimum dose for mutant production is approximately 800 rad X-rays. Rather often, more than one phenotypically identical mutant was found, which was always derived from the same explant. They could for instance originate from a multi-apical meristem formed by a single mutated cell. 相似文献
24.
The method to determine the crystallinity of solid slag film is established by analyzing the DSC curve of solid slag film and corresponding quenched slag. The accuracy of the method is investigated by measurements of prepared samples whose crystallinity is given. In addition, the solid slag films of mold slags used to cast medium carbon steel and low carbon steel are obtained by heat flux simulator in laboratory, and the crystallinity of the two kinds of slag film are also measured by DSC method. Experimental results indicates that the crystallinity of solid slag film can be determined by comparing the crystallization enthalpy of solid slag film and corresponding quenched slag during heating process, and the relative error is within 5.03%. For medium carbon steel, the crystalline fraction of solid slag film is 88.6%, while the crystalline fraction of solid slag film corresponding to low carbon steel is 55.0%. The results are consistent with actual structure of solid slag films. 相似文献
25.
26.
27.
28.
29.
30.
喻云水 《林业机械与木工设备》2001,29(11):26-29
针对山毛榉实木地板生产中因表面材质缺陷导致地板优等品率及出材率低的问题,采用山毛榉刨切单板对山毛榉实木地板进行贴面,并对改善实木地板表面质量的工艺技术进行了探讨。 相似文献