全文获取类型
收费全文 | 83725篇 |
免费 | 4668篇 |
国内免费 | 5670篇 |
专业分类
林业 | 9863篇 |
农学 | 6240篇 |
基础科学 | 4804篇 |
10959篇 | |
综合类 | 42337篇 |
农作物 | 3400篇 |
水产渔业 | 2641篇 |
畜牧兽医 | 7519篇 |
园艺 | 2083篇 |
植物保护 | 4217篇 |
出版年
2024年 | 281篇 |
2023年 | 1099篇 |
2022年 | 1728篇 |
2021年 | 1890篇 |
2020年 | 1892篇 |
2019年 | 2343篇 |
2018年 | 1273篇 |
2017年 | 2393篇 |
2016年 | 3126篇 |
2015年 | 2789篇 |
2014年 | 3944篇 |
2013年 | 3934篇 |
2012年 | 6137篇 |
2011年 | 6411篇 |
2010年 | 5226篇 |
2009年 | 5212篇 |
2008年 | 4900篇 |
2007年 | 5960篇 |
2006年 | 5316篇 |
2005年 | 4436篇 |
2004年 | 3367篇 |
2003年 | 2905篇 |
2002年 | 2270篇 |
2001年 | 1996篇 |
2000年 | 1793篇 |
1999年 | 1397篇 |
1998年 | 1207篇 |
1997年 | 1110篇 |
1996年 | 1067篇 |
1995年 | 1070篇 |
1994年 | 1029篇 |
1993年 | 871篇 |
1992年 | 805篇 |
1991年 | 664篇 |
1990年 | 594篇 |
1989年 | 535篇 |
1988年 | 418篇 |
1987年 | 291篇 |
1986年 | 144篇 |
1985年 | 49篇 |
1984年 | 24篇 |
1983年 | 25篇 |
1982年 | 21篇 |
1981年 | 20篇 |
1980年 | 23篇 |
1979年 | 19篇 |
1978年 | 15篇 |
1977年 | 9篇 |
1976年 | 11篇 |
1962年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
991.
贫困地区农业技术推广新模式:发展小区域农业技术推广户
——基于甘肃省部分贫困县的调查思考 总被引:3,自引:0,他引:3
:madc@gsau.edu.cn 《中国农学通报》2006,22(5):473-473
(1甘肃农业大学经济管理学院,兰州 730070;2兰州资源环境职业技术学院,兰州 730020) 相似文献
992.
Yang Chunwei 《保鲜与加工》1988,(4)
This paper studies the tactics choice and its improvement in the development of economy by means of Markovian Decision Programming. An optimal decision and the maximum expected revenue can be obtained. The . paper also presents the procedures and formulas of numerical evaluation. 相似文献
993.
Investment on construction projects has become an important factor in improving the development of economy in China.The non-price bottom bidding is a representation that the investment on projects is becoming standardized.During the years of trying out the non-price bottom bidding,the colluding in bidding or bidding below the cost has happened several times,which have damaged the benefits of owners.To solve theses problems,this paper firstly studies the reason of these problems-the failure in the normal relationship between principal and agent.Then,some measures have been presented as follows: building systematic and scientific system of qualification prejudication,judging behaviors of colluding in bidding and bidding below the cost with reason and providing a surety mechanism of the project.The authors hope that these measures are beneficial to non-price bottom bidding. 相似文献
994.
With the study of minbus's accelerated exterior noise control,the principle of sound intensity measurement was applied,the sound intensity of a minbus's surface noise was tested,and the surface noise distribution was presented.Several identification of noise source methods including sound power,sound intensity contour map,frequency spectrum were used together for surface noise analysis and study.Engine radiation noise and exhaust noise was identified as the major noise sources.On the contrary,car body vibration noise,tyre noise,transmission agent noise,air admission noise just occupied a little proportion of surface sound radiation energy.The research provides the reliable basis to determine main projects of minibus's accelerated exterior noise control. 相似文献
995.
WEN Jun-hao~ 《保鲜与加工》2004,(12):111-115
Wavelets have been widely applied in such research areas as image processing, computer vision, network management and data mining. Wavelets have many favorable properties, which are hierarchical and multiresolution decomposition structure, linear time and space complexity of the transformations. The paper presents wavelet application on the algorithms of data mining, in cluding as clustering, classification, distributed data mining, similarity search, approximate query processing, visualization and so on. Finally, the paper concludes by discussing the impact of wavelets on data mining research and outlining potential future research directions and applications. 相似文献
996.
Overconstraints exist widely in planar closed chain mechanisms and mechanical systems result in a series of detrimental influences on behavior of machines, and attention is given to them by machine designer. Some analysis methods of overconstraints in planar closed chain mechanisms are presented, and more study due to the faultiness of these methods. In accordance with faultiness of two common kind of methods, formulas method and loop analysis method of degrees of freedom, and by combining these two methods, an useful mechanism overconstraints analysis method which is convenient for computer aided overconstraints analysis is gained via research on the two methods thoroughly and systematically, and some new views about mechanism overconstraints analysis are presented. 相似文献
997.
Such the geological hazards as landslide, rockfall, debris-flow and so on frequently occur in the Three Gorges Reservoir Area, so it is a very practical and immediate job to explore the mechanism caused the geological hazards and how to forecast and control the geological hazards. For this reason, this paper introduces the situation of the geological hazards occurred in the Three Gorges Reservoir Area and the major type and feature of the geological hazards occurred in Chongqing, and discusses the basic principle about the modern nonlinear science applied to the geological hazards and the creep-slip, stick-slip occurred on the joints of rock mass and the monitoring technology of the geological hazards.The basic thinking is put forward which can be applied the modern nonlinear science to the geological hazards occurred in the Three Gorges Reservoir Area. 相似文献
998.
In this article we have worked out the correlation between electronegativity and high temperature superconductivity for oxide. It is suggested the equalized electronegativity, X cq , can be used as a empirical criterion for superconductivities of oxides. For determining the X cq , a new formula for the calculation of X cq values has been obtained The X cq values of 230 oxide superconductors have been calculated. The result shows that the X cq values of all the oxide superconductors concentrate in a narrow range from 5.00 to 5.63 and that the oxides with values out side this region would be non-superconductive. This criterion can be applied to almost all the oxide superconductors. It is clearly that this result is able to benefit further inquiries about the mechanism of superconductivity. 相似文献
999.
Complexity of mutual act and different sensation of different tourists are important factors influencing regional tourism resources evaluation. Fuzzy mathematic method can be used to up quantitative evaluation method on tourism resources evaluation. Taking Wushan Small Three Gorges as an example, the author carries out the evaluation of the tourism resources in the Three Gorges Reservoir. At the same time, the authors consider that five factors, such as improvement of the comunication of tourism resources, quickening the Steps of urbanization in reservior area, must be done well. 相似文献
1000.
In urban design, only by continuous and dynamic research work from design to finally putting it into practice, can we made good control on city appearance. This article analyzes nowadays defects in our urban design from two aspects as the result establishment and validated control, and tries to conceive a feasibility plan to solve the problem. 相似文献