全文获取类型
收费全文 | 12698篇 |
免费 | 815篇 |
国内免费 | 1253篇 |
专业分类
林业 | 901篇 |
农学 | 1009篇 |
基础科学 | 612篇 |
1334篇 | |
综合类 | 5825篇 |
农作物 | 1074篇 |
水产渔业 | 642篇 |
畜牧兽医 | 2085篇 |
园艺 | 760篇 |
植物保护 | 524篇 |
出版年
2024年 | 81篇 |
2023年 | 229篇 |
2022年 | 507篇 |
2021年 | 501篇 |
2020年 | 465篇 |
2019年 | 504篇 |
2018年 | 344篇 |
2017年 | 586篇 |
2016年 | 401篇 |
2015年 | 550篇 |
2014年 | 647篇 |
2013年 | 711篇 |
2012年 | 929篇 |
2011年 | 954篇 |
2010年 | 959篇 |
2009年 | 777篇 |
2008年 | 793篇 |
2007年 | 752篇 |
2006年 | 682篇 |
2005年 | 601篇 |
2004年 | 393篇 |
2003年 | 455篇 |
2002年 | 704篇 |
2001年 | 509篇 |
2000年 | 348篇 |
1999年 | 158篇 |
1998年 | 33篇 |
1997年 | 22篇 |
1996年 | 25篇 |
1995年 | 20篇 |
1994年 | 22篇 |
1993年 | 17篇 |
1992年 | 16篇 |
1991年 | 14篇 |
1990年 | 8篇 |
1989年 | 18篇 |
1988年 | 10篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1962年 | 2篇 |
1956年 | 5篇 |
1955年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
141.
In system controlled,Sampling these parameters and with parameters for controller in time, it is an object to adaptive control. The article presents a scheme that the structure parameters on it's model and model parameters is robust identified by on line, while to optimal of algorithm on adaptive control is fulfilled. In control scheme, method of intelligent identifying to the structure parameters(levels of model) and algorithm of robust pole placement are introduced also It is advancer for already mentioned scheme. Whole scheme presents new model on adaptive control. 相似文献
142.
Discussion about Saving Energy in Refrigeratory 总被引:1,自引:0,他引:1
Food refrigeration is regarded as a high energy consuming trade. Under the long period system of state operated enterprise,there are many phenomenons of ignoring energy management and wasting energy. Energy consuming is not very clear for production.Consuming in our country is far more than the international standard and there is a distance between the middle_westland and the eastland. As a enterprise that faces the international market,it is important for it to strength the management so that the cost can be reduced. Considering those phenomenons of ignoring energy management and wasting energy in refrigeratory at present, some measures such as improved the unreasonable operation process, strengthening the energy management and automation to realize automatizing operation are improved to reduce the cost for refrigeratory trades. 相似文献
143.
In order to settle some problems involved in applying ANSYS into nonlinear Finite Element Analysis of RC structure,this paper discusses the nonlinear FEM method for staggered joint,incorporating its experimental result.The main solved problems are as follows:(1) The fundamental process of nonlinear FEM analysis;(2) How to model the behaviors of reinforcement and concrete respectively;(3) How to model the bond-slip relationship between reinforcement and concrete. 相似文献
144.
Fingerprint classification can provide an important indexing mechanism in a fingerprint database. An accurate and consistent classification can greatly reduce fingerprint matching time for large database. In the paper, by combining genetic algorithm and neural network is presented a fingerprint classification algorithm which is able to achieve an accurate classification. By inputting the global feature represented by directional image to three layer neural network trained by genetic algorithm, the fingerprints were classified into six categories: whorl, right loop, left loop, arch, double loop and undiscerning type successfully. 相似文献
145.
Based upon the conception of the least loop,the most loop and direction factor presented by the author firstly,the algorithm of searching out the least and most loops has been designed.By building the adjoining matrix, confirming the start-point of searching,vectorizing the searching sides,calculating the direction factor of adjoining sides,we can search out the next side of the least loop or the most loop rapidly.With a valid searching side being confirmed at every searching and the searching scope being reduced by forming degenerate graph,the time compexity of the algorithm is much less. In the research of the automatic calculating system of construction quantities, the problem of houses partition and out-wall partition had been solved succesfully by utilizing this searching algorithm. 相似文献
146.
147.
148.
折流式水解反应器处理印染前道废水进水pH的影响 总被引:1,自引:0,他引:1
印染前处理阶段的前道水在印染废水中占有相当的比重,且难降解.运用折流式反应器(HRT=12 h)对其进行了水解预处理研究,考察了在不同的进水pH时,反应器内各格室的COD值及其去除率随进水pH值的变化规律以及反应器出水BODs/CODcr的变化.试验结果表明,进水pH值适宜范围为7.6~8.8,COD去除率在29%~40%之间,出水BODs/CODcr由进水的0.35左右提高到0.45左右,为印染废水的达标排放处理的水解pH条件提供参考. 相似文献
149.
150.
生物质资源高压连续输送的研究 总被引:1,自引:0,他引:1
建立了近中试规模的生物质资源高压连续输送装置,通过将生物质资源与水混成浆料的方法实现了生物质资源的高压连续输送、浆料的固含量可达10%(wt)以上,压力可达40MPa,最大浆料供应量为2.4L/h。 相似文献