全文获取类型
收费全文 | 76801篇 |
免费 | 3744篇 |
国内免费 | 8440篇 |
专业分类
林业 | 9114篇 |
农学 | 12348篇 |
基础科学 | 6839篇 |
12528篇 | |
综合类 | 23564篇 |
农作物 | 4004篇 |
水产渔业 | 2559篇 |
畜牧兽医 | 10170篇 |
园艺 | 2927篇 |
植物保护 | 4932篇 |
出版年
2024年 | 161篇 |
2023年 | 730篇 |
2022年 | 1948篇 |
2021年 | 2860篇 |
2020年 | 2700篇 |
2019年 | 2512篇 |
2018年 | 1809篇 |
2017年 | 2694篇 |
2016年 | 2547篇 |
2015年 | 3319篇 |
2014年 | 3296篇 |
2013年 | 4165篇 |
2012年 | 4986篇 |
2011年 | 5298篇 |
2010年 | 5095篇 |
2009年 | 4644篇 |
2008年 | 4484篇 |
2007年 | 4897篇 |
2006年 | 4412篇 |
2005年 | 3976篇 |
2004年 | 2007篇 |
2003年 | 1707篇 |
2002年 | 1603篇 |
2001年 | 1643篇 |
2000年 | 1802篇 |
1999年 | 1938篇 |
1998年 | 1755篇 |
1997年 | 1475篇 |
1996年 | 1358篇 |
1995年 | 1273篇 |
1994年 | 1130篇 |
1993年 | 1057篇 |
1992年 | 875篇 |
1991年 | 703篇 |
1990年 | 612篇 |
1989年 | 442篇 |
1988年 | 367篇 |
1987年 | 261篇 |
1986年 | 139篇 |
1985年 | 59篇 |
1984年 | 51篇 |
1983年 | 52篇 |
1982年 | 38篇 |
1981年 | 49篇 |
1980年 | 23篇 |
1979年 | 11篇 |
1965年 | 4篇 |
1964年 | 4篇 |
1962年 | 4篇 |
1955年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Li Jianping Zhang Wanping Chen Tinghuai Shu Wenzhi 《保鲜与加工》1997,(2):63-68
Based on the optimal control theory and Lagrange interpolation an optimal design model of plane cascades of 3D blade in an arbitrary surface of revolution is established. Using wavelet theory to solve the model, and lots of numerical results are obtained. The results show that the wavelet method is more effective than the conventional methods. 相似文献
992.
Zhang Hongjing Zhou Zhaoyi 《保鲜与加工》1997,(2):123-127
This paper presents a detail study of bubble coalescence in inorganic salts and organic compounds of fermented solution ,and preliminary analyses the principle of bubble coalescence.The experiments show that the relationship between the solute concentration and coalescence frequency reveals the existence of sharp transition concentration. 相似文献
993.
994.
A raseach has been done on the possibility of producing nitriochumic acid fromweathered coal of Nantong,Sichuan,oxidised by nithic acid.The optimun reacting conditions,whichare found through the way of orthogonal experiment,are suggested as follows:concentration ofHON3 35%,rate of HON3 to coal 3.5,reacting take 15 min,and reaction temperature 369 K. Thecomposition of product is Wf 2. 91 %;Ag 14.06%;HAg 78.28%;Ng 1.62%. 相似文献
995.
996.
A new quick thinning algorithm was presented in this paper,which assigneddifferent weights to different pixels near the skeleton pixels and rules out the im possible pixels in thethinning procedure. It needs neither iteration on pixel panel nor detection on every pixel such thatthe time consumed is greatly lessened. A filling algorithm is also offered for better results.Experiment on variety of binary patterns showed that it could get both a high speed and a goodskeleton shape compared with other algorithms,This new algorithm reaches perfect result. 相似文献
997.
998.
As a key resource, the knowledge management is becoming a research field interested by many researchers. In order to study the mathematics theory base of knowledge expression, in this paper, a knowledge expression model is given. In this model the knowledge system is expressed by multi-tuple, the single knowledge object is expressed by the tuple, a structural expression of knowledge is given using token as example and the application of the model in city water supply pipe network is presented in this paper. 相似文献
999.
Based on the content of enterprise culture and enterprise credit, it is pointed out that the enterprise culture related to the enterprise core competitive force.In this paper, from the viewpoint of combining theory with practice, the intension, function and mutual relations between them are described and their significance in the market competition as well.The potential things,which the enterprise staffs are seeking for, from its inherent mind and the enterprise theory are the enterprise culture which becomes the enterprise core competitive force in its actual sense.The enterprise credit, as the enterprise culture in its ideological sphere, is an essential factor, which greatly affects the enterprise core competitive force.At last the authors provide some good suggestions on how to cultivate enterprise credit and to build enterprise culture. 相似文献
1000.
In this paper the problem of energy consumption and environment in the birdhouse is introduced and the reconstructive measures aiming at energy savings are recommended. The measures include the limitation of temperature region, reconstruction of the building envelop and using the sunny board at the south side of the birdhouse roof. Finally, the energy efficiency of the reconstructive project is estimated. 相似文献