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   289篇
  免费   23篇
  国内免费   3篇
林业   27篇
农学   118篇
基础科学   6篇
  34篇
综合类   75篇
农作物   14篇
水产渔业   5篇
畜牧兽医   21篇
园艺   7篇
植物保护   8篇
  2024年   4篇
  2023年   15篇
  2022年   13篇
  2021年   5篇
  2020年   4篇
  2019年   9篇
  2018年   1篇
  2017年   4篇
  2016年   9篇
  2015年   5篇
  2014年   9篇
  2013年   19篇
  2012年   21篇
  2011年   20篇
  2010年   17篇
  2009年   13篇
  2008年   18篇
  2007年   12篇
  2006年   14篇
  2005年   9篇
  2004年   6篇
  2003年   10篇
  2002年   15篇
  2001年   11篇
  2000年   8篇
  1999年   3篇
  1998年   1篇
  1997年   3篇
  1996年   3篇
  1995年   4篇
  1994年   6篇
  1993年   3篇
  1992年   1篇
  1991年   5篇
  1990年   2篇
  1989年   1篇
  1988年   1篇
  1986年   1篇
  1984年   2篇
  1983年   1篇
  1979年   1篇
  1976年   1篇
  1973年   1篇
  1970年   1篇
  1967年   1篇
  1966年   1篇
  1960年   1篇
排序方式: 共有315条查询结果,搜索用时 15 毫秒
1.
保护地蔬菜病害防治新技术──安全型防病烟剂生产和使用张弓,候竹林,韩盘铭(中国农科院蔬菜花卉所)(北京理工大学)编者按由张弓、候竹林等人发明的“防治病害用喷射式烟剂”,中国专利局已授予发明专利权,专利号:ZL88104286.2,并获第五届全国发明展...  相似文献   
2.
3.
切叶肾蕨栽培技术简介   总被引:1,自引:0,他引:1  
肾蕨(NephrolepiscordifoliaPresl.)俗称蜈蚣草。属骨碎补科,多年生常绿草本植物。株高30~50cm,叶羽状深裂,密集丛生。孢子羹群着生在叶背叶脉分歧点的上部。肾蕨叶片翠绿,姿态婆婆,四季常青。又耐阴,是室内观赏蕨类上佳花卉。又是一种很重要的切花配叶。1繁殖?..  相似文献   
4.
Aluminum (Al) is very toxic to many living organisms, including plants, animals and microorganisms. However, despite many studies on Al tolerance in plants, little has been reported concerning these mechanisms in microorganisms. In this study, a red yeast, which could tolerate Al 3+ concentrations as high as 200 mmol L-1 , was isolated from acidic soils, identified as Rhodotorula sp. and designated as RS1. As the medium compositions can greatly affect the responses of microorganisms to Al, two culture mediums, glucose medium (GM) and lysogeny broth medium containing soil extract (S-LBM), were used. During growth of RS1, the pH of medium decreased in GM but increased in S-LBM. These changes in the pH of the media were not induced by Al addition. No or little secretion of organic acids was observed in RS1 growth media. Importantly, the thickness of the cell walls and the ratio of cell wall to biomass of RS1 significantly increased in GM with high Al 3+ concentrations. In the presence of 100 mmol Al L-1 , 78.0% of the total Al of whole cells was present in the thickened cell walls. The Al in cell walls was mostly bound to OH, amide and CO groups of polysaccharides. These results suggest that thickening of the cell wall in response to the high Al 3+ concentrations may play an important role in the high tolerance of RS1 to Al and that pH increase of the medium and chelation of Al ions are not involved in Al tolerance of this organism.  相似文献   
5.
Due to a series of wonderful characteristics, submicron particles are of high value in national economy, defense modernization and high technology fields, with wide application prospects. Submicron particle sizing methods and techniques are difficult problems in particle research field. Modern methods for particle sizing are stated and analyzed. Some problems are discussed when these methods are used for submicron particles.  相似文献   
6.
For the limitations of the traditional monitoring systems under the circumstances of dispersed monitoring points, wide distribution range and the harsh environment, a distributed wireless monitoring system based on radio frequency technique is designed. The system adopts the ultra low power consumption MCU MSP430 as the main control chip and extends several processing module in the periphery. In addition, the multi channel transceiver nRF905 is used for wireless data transmission. The software and hardware design scheme of the proposed system and the communication protocol for distributed data transmission are discussed. Frequency hopping mechanisms are employed to increase the reliability of data transmission. The results show that the proposed system has the characteristics such as flexible use and excellent mobility, while can monitor multipoint data in special environment in real time.  相似文献   
7.
According to the urgent need for motorcycle parts enterprise to improve the ability of information exchange and business collaboration between the production process and other links such as the marketing, design, production planning, outsourcing, purchasing and delivering, an integration framework of the intergraded workshop production management system for motorcycle parts enterprise is presented. It can be integrated with the designing and production planning management systems upwards, the workshop equipments and workers downwards, and the subcontract production and supply chain management systems outwards. Then, some key technologies are studied, such as the realization scheme of system integration based on Service Oriented Architecture (SOA), the data integration and sharing mechanism of heterogeneous information system based on eXtensible Markup Language (XML), and the real-time interaction technology of workshop information based on the multi-functional interactive information terminals, etc. Finally, the system is developed and successfully applied in a motorcycle parts enterprise, and good results are obtained.  相似文献   
8.
9.
The importance of indoor air quality and the effect of volatile organic compounds(VOC) on human health are discussed in this paper,TVOC as a measurement for evaluation of VOC and the VOC pollution control methods and technology for indoor air are also presented.  相似文献   
10.
Compared to bi-fuel engine,it uses completely CNG(Compressed nature gas) to replace diesel which can save more oil fuel than bi-fuel engine that reffited diesel engine into CNG engine. A 4102 diesel engine is refitted into CNG engine and a mechanical ignition timing system is designed by the method of gear and belt. The principles and the construction of the system is introduced and the characteristics of the design is analyzed. The system performed well and had good liability when run in a platform. Compared with the previous one, it kept higher dynamic character and emitted lower. It is a cheap one and can be use to reform the diesel engines.  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