首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   11331篇
  免费   458篇
  国内免费   1403篇
林业   726篇
农学   1189篇
基础科学   618篇
  1422篇
综合类   5106篇
农作物   761篇
水产渔业   517篇
畜牧兽医   1529篇
园艺   734篇
植物保护   590篇
  2024年   51篇
  2023年   136篇
  2022年   271篇
  2021年   324篇
  2020年   380篇
  2019年   508篇
  2018年   426篇
  2017年   501篇
  2016年   622篇
  2015年   498篇
  2014年   561篇
  2013年   625篇
  2012年   720篇
  2011年   702篇
  2010年   660篇
  2009年   615篇
  2008年   562篇
  2007年   540篇
  2006年   483篇
  2005年   364篇
  2004年   296篇
  2003年   260篇
  2002年   218篇
  2001年   194篇
  2000年   200篇
  1999年   176篇
  1998年   165篇
  1997年   243篇
  1996年   227篇
  1995年   202篇
  1994年   228篇
  1993年   232篇
  1992年   273篇
  1991年   267篇
  1990年   226篇
  1989年   97篇
  1988年   40篇
  1987年   28篇
  1986年   16篇
  1985年   7篇
  1984年   8篇
  1983年   2篇
  1982年   4篇
  1981年   6篇
  1980年   2篇
  1979年   5篇
  1978年   4篇
  1977年   4篇
  1956年   5篇
  1955年   5篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
151.
A video Monitor &Control system of tunnel based on DSP/BIOS is proposed,which is different from traditional video Monitor & Control system.It uses DSP to process image,and uses enhanced video input processor to qcquire image.This system satisfies all requirements of video supervision,and is a low cost system.It has a good application foreground.The system has been confirmed as a good veracity and practicability system through testing in the Zhongliang Mountain tunnel of Chongqing.  相似文献   
152.
The predictive intelligent control scheme is proposed, which is based on approximation theory and numerical method of Chcbyshev orthogonal polynomial. It has the practical value to the cold storge using widely electromagnetic valve and can be also applied similar systems in orther area.  相似文献   
153.
The phase transformation in the diffusion layer after slow cooling and aging of pure iron ion -nitrided was investigated with TEM. Refering to principle of Moire method measuring macroscopical strain, the values of coherent strain at interfaces between a" and aN phases were determined by means of TEM analyses.  相似文献   
154.
155.
156.
This paper expatiates on the bus structure and develop the bus mode Multi-Channel Analyzer (MCA). The nucleus of this MCA is the PC/104 embedded computer, and it introduces the bus communication to realize system and data communication. It may realize data collecting and showing in the field, because the bus mode is rapid. At first, on the hardware we introduce CMOS components, this reduces power, volume and weight. These make it adapts to use in the field; besides, on the software we adopt C and assembly language to program in order to improve conversion speed. At the same time, single-task DOS operating system is infroduced, which makes the software run more steadily, operate more simply. By means of testing on the spot it can normally work, so it suitable to work in the field.  相似文献   
157.
Rectangular Cover System of Manifold Method and Its Auto Mesh Algorithm   总被引:2,自引:0,他引:2  
In contrast to the finite element method, another form of numerical method which is based on the using of rectangular math covers in manifold method is proposed. In this method, the element data is not a necessary in the input data files and it can be incorporated with the CAD technology conveniently. The theory and application of the method are discussed and the auto mesh algorithm of the cover system is also given in this paper. The numerical examples indicate that the method and the algorithm are accurate and effective.  相似文献   
158.
The basic principle of using chromium leach residue as melting flux of blast furnace is introduced in this paper.The reduction thermodynamics of Na 2CrO 4 and chromium oxides in the process of sintering and ironmaking is studied,and the simulating experiments in the laboratory and industrial experiments in 600 m 3 blase furnace are carried out.The results of thermodynamical study and experimental study show that hexavalent chromium ion in the burden can be well eliminated in the process of sintering and ironmaking.  相似文献   
159.
160.
The idea for an expert system approach to the computer aided design of intelligent controllers (ESCAD1C) is discussed and the idea of two step modelling of an intelligent controller is presented on the basis of emulating human control behaviours to solve complex problems. The structure, functions and characteristics of ESCADTC system , and the design procedures of intelligent controllers are gived. The knowledge base and simulating functions for designing intelligent controllers are also described.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号