全文获取类型
| 收费全文 | 84095篇 |
| 免费 | 4110篇 |
| 国内免费 | 9148篇 |
专业分类
| 林业 | 9278篇 |
| 农学 | 12189篇 |
| 基础科学 | 7089篇 |
| 13087篇 | |
| 综合类 | 27640篇 |
| 农作物 | 4613篇 |
| 水产渔业 | 2903篇 |
| 畜牧兽医 | 11655篇 |
| 园艺 | 3535篇 |
| 植物保护 | 5364篇 |
出版年
| 2024年 | 201篇 |
| 2023年 | 897篇 |
| 2022年 | 2274篇 |
| 2021年 | 3248篇 |
| 2020年 | 2839篇 |
| 2019年 | 2866篇 |
| 2018年 | 2025篇 |
| 2017年 | 2956篇 |
| 2016年 | 2732篇 |
| 2015年 | 3872篇 |
| 2014年 | 3752篇 |
| 2013年 | 4500篇 |
| 2012年 | 5579篇 |
| 2011年 | 5961篇 |
| 2010年 | 5922篇 |
| 2009年 | 5432篇 |
| 2008年 | 5002篇 |
| 2007年 | 5146篇 |
| 2006年 | 4805篇 |
| 2005年 | 4229篇 |
| 2004年 | 2055篇 |
| 2003年 | 1952篇 |
| 2002年 | 1705篇 |
| 2001年 | 1698篇 |
| 2000年 | 1749篇 |
| 1999年 | 1966篇 |
| 1998年 | 1714篇 |
| 1997年 | 1542篇 |
| 1996年 | 1407篇 |
| 1995年 | 1267篇 |
| 1994年 | 1084篇 |
| 1993年 | 1116篇 |
| 1992年 | 875篇 |
| 1991年 | 737篇 |
| 1990年 | 623篇 |
| 1989年 | 500篇 |
| 1988年 | 383篇 |
| 1987年 | 229篇 |
| 1986年 | 127篇 |
| 1985年 | 65篇 |
| 1984年 | 44篇 |
| 1983年 | 40篇 |
| 1982年 | 48篇 |
| 1981年 | 48篇 |
| 1980年 | 32篇 |
| 1979年 | 14篇 |
| 1965年 | 15篇 |
| 1964年 | 11篇 |
| 1963年 | 12篇 |
| 1956年 | 7篇 |
排序方式： 共有10000条查询结果，搜索用时 15 毫秒
991.
992.
The design of MP3 decode system based on DSP is introduced. TLV320AIC23, a high performance and stereo codec chip, is selected as a D/A converter in the system. Two McBSPs ofDSP are connected to TLV320AIC23, one of them acts as configuration interface, the other ,the audio digital interface. Configuration interfacemode is SPI. The MP3 audio bitstreamtransmissionbetween the PC and DSP isrealized through the USB1.1 interface. So it is convenientto access MP3 audio bitstream. A large capacitymemory device, Compact Flash Card , is a storage media accessing MP3 bitstream.a programmable logical device, CPLD, controls reading, writing and chip selection of USB and Compact Flash Card. Some experiments show the systemcan well accomplish MP3 decodingand playing. 相似文献
993.
994.
995.
Li Jianzhong Wang Guanjie 《保鲜与加工》1993,(2):14-18
By comparing the techniges of the production and the logic predicate for knowledge representation, this paper presents a kind of constructure of combinatorial knowledge base applied to the expert system for switch operation in electric power system . This constructure of knowledge base to be expanded and revised easily,and it is cinvenitnt to build the general shell of the expert system. 相似文献
996.
997.
Li Maoqin Duan Yurong 《保鲜与加工》1989,(4):22-29
In this paper, a kind of grey linear programming with grey interval coefficients is discussed,the definitions of the first and second whitenized linear programmlngs and the grey dual linear programmings are presented, the relationships between the solutions of the above three kinds of programming and the solution of the primal programming are explored, and some new conclusions are obtained. 相似文献
998.
Li Yourong Jin Mingcong Tang Jingwen 《保鲜与加工》1993,(6):46-50
The concept of loss rate of available energy was introduced for evaluating heat exchanger performance. At the same time, the general expression of loss rate of available energy was obtained for heat exchangers of several typical. And NL criteria was recommended for evaluation of the loss rate of available energy of heat exchanger. Then. the influences of inlet temperatures ratio, heat capacity ratio of fluids, the number of heat transfer units and flow patterns of heat exchanger on ,VL criteria were also discussed. 相似文献
999.
Based on properties of parameters and test data of dom-estic steel,this paper analyses the reliability and partial coefficient forresistance of steel frame columns of tall builings.The result may serveas a scientific basis.It is not only for domestic steel instead of importedsteel in building tall steel structures,but also for compiling concerendstandards. 相似文献
1000.
Li Runfang Li Yusheng 《保鲜与加工》1993,(1):96-101
A new finite element method is presented in this paper to analyze the thermo-
elastic contact problem with heat input on meshing tooth faces. The computational model of meshing gear has been established and the frictional heat input on meshing tooth faces is estimated. In addition, 2-D finite element analysis program for this kind of problem is listed. The test and practical examples are given to show the validity and versatility of this method. 相似文献