全文获取类型
收费全文 | 6600篇 |
免费 | 402篇 |
国内免费 | 802篇 |
专业分类
林业 | 944篇 |
农学 | 483篇 |
基础科学 | 695篇 |
1312篇 | |
综合类 | 3306篇 |
农作物 | 124篇 |
水产渔业 | 228篇 |
畜牧兽医 | 377篇 |
园艺 | 118篇 |
植物保护 | 217篇 |
出版年
2024年 | 67篇 |
2023年 | 161篇 |
2022年 | 270篇 |
2021年 | 271篇 |
2020年 | 249篇 |
2019年 | 307篇 |
2018年 | 186篇 |
2017年 | 302篇 |
2016年 | 328篇 |
2015年 | 271篇 |
2014年 | 393篇 |
2013年 | 367篇 |
2012年 | 495篇 |
2011年 | 501篇 |
2010年 | 412篇 |
2009年 | 348篇 |
2008年 | 313篇 |
2007年 | 383篇 |
2006年 | 360篇 |
2005年 | 285篇 |
2004年 | 230篇 |
2003年 | 205篇 |
2002年 | 128篇 |
2001年 | 122篇 |
2000年 | 105篇 |
1999年 | 84篇 |
1998年 | 97篇 |
1997年 | 74篇 |
1996年 | 56篇 |
1995年 | 71篇 |
1994年 | 64篇 |
1993年 | 56篇 |
1992年 | 44篇 |
1991年 | 40篇 |
1990年 | 47篇 |
1989年 | 44篇 |
1988年 | 22篇 |
1987年 | 17篇 |
1986年 | 7篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 5篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1956年 | 2篇 |
排序方式: 共有7804条查询结果,搜索用时 15 毫秒
71.
水资源合理配置是解决水资源分配不均,缓解水资源供需矛盾,提高水资源利用效率的有效途径。然而由于缺乏实测径流资料,区域无法合理量化乃至分配水资源,造成缺乏与浪费并存的现象。为此,以都匀市为例,利用清水江下游黔南州下司水文站的实测资料构建了SWAT分布式水文模型,通过相关系数及纳西效率系数验证了模型的精度,得到了可用作水资源配置基础资料的都匀市境内各干支流长系列流量数据。通过量化水资源系统中各部门的供需并连接相关关系,建立了基于水量平衡的WEAP水资源配置模型,并预测了现状2010年至远景2030年的区域水资源供需平衡情况。结果表明:针对径流资料缺乏地区,应用水文模型模拟径流数据进行水资源配置的方法,能够定量分析不同供需情况下的水资源分配矛盾,可以为区域水资源管理及社会可持续发展规划提供指导。 相似文献
72.
73.
74.
红酵母的性质及其应用研究 总被引:10,自引:0,他引:10
红酵母是酵母菌的一个属,腐生,分布广泛,在医学、食品、化工和农业等方面都有一定的应用,但目前并没有引起人们足够的重视。综述了红酵母的种属特性、理化特性、培养及其应用。 相似文献
75.
YANG Xue-heng CHEN An HE Guang-hong FENG Xiao-juan WANG Ying-fang ZHAN Jie TANG Zhi-liang 《保鲜与加工》2001,(3):137-141
Some ideas are given about using out-clock, CPU and anti-T-net of D/A card for getting to the intelligent control of scanning voltage ,low-filter and hign-filter of STM; logarithm amplifier for tunnelling current contraction. At last, some applications and questions when it running about STM are discussed. 相似文献
76.
Identification and adjustment on the disfigurements of original data of VISAR are probed by developing software for VISAR data reducing based on measure theory. Then the software is applied to plate impact experiment of ceramics. The disfigurements of light intensity data are identified and adjusted through Lissajou~ figures. The results indicate that VISAR data are reduced quickly and effectively by the software, and the exact free surface velocity history is obtained. 相似文献
77.
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
78.
To construct data warehouse with heterogeneous, self-governing and distributed database system is a challenge. Two problems have to be solved: one is how to collect data from heterogeneous data sources by an effective method, the other is how to clear up and change the format of the data collected from data sources. The opening and the interact-operation property of Web Services is Analyzed. A Data Collection System based on Web Services, which communicates with heterogeneous data sources with SOAP and HTTP, has been designed. A Data Collector is introduced to clear up and to transform data with composition technology. The pivotal XML technology of transforming and loading up the data are discussed. 相似文献
79.
To the question that a meter is correspond with a set of lead and a sensor,this paper presents a design of data acquisition system for vehicle based on CAN bus.In this way,the combinatorial instrument is only connected by a bus unit.Author introduces the data acquisition structure chart and the CAN interface,analyzes the software by program flow chart,and shows it's application for vehicle virtual instrument.A method of calculating vehicle speed,engine rotate speed and the course of development mileage are also given. 相似文献
80.
Considering the difficult of acquiring and transmission the signal from the moving equipment, a new fault diagnosis monitoring system is presented. The system acquires the state signal from the moving equipment by data acquisition module that based in W77E58 high-speed SCM, and transmits the data fast by wireless mode. The signal data can be use for fault diagnosis and precise analysis. The system has the ability for acquiring abundance of data with a high speed, the ability for high accuracy data conversion, and has a function of programme controlling gain and programme controlling low-pass filtering. The successful application of this system on the vibration monitor about the material-transporting bogie in an iron works of a domestic steel enterprise proves the stability and credibility about the design project, also testifies its practical value and versatility. 相似文献