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   28489篇
  免费   1201篇
  国内免费   2358篇
林业   3122篇
农学   2147篇
基础科学   3772篇
  4134篇
综合类   13384篇
农作物   941篇
水产渔业   894篇
畜牧兽医   2070篇
园艺   721篇
植物保护   863篇
  2024年   134篇
  2023年   367篇
  2022年   571篇
  2021年   708篇
  2020年   710篇
  2019年   802篇
  2018年   516篇
  2017年   838篇
  2016年   1136篇
  2015年   1008篇
  2014年   1459篇
  2013年   1430篇
  2012年   2181篇
  2011年   2354篇
  2010年   1837篇
  2009年   1921篇
  2008年   1870篇
  2007年   2194篇
  2006年   1797篇
  2005年   1549篇
  2004年   1098篇
  2003年   944篇
  2002年   716篇
  2001年   624篇
  2000年   485篇
  1999年   412篇
  1998年   370篇
  1997年   317篇
  1996年   307篇
  1995年   264篇
  1994年   231篇
  1993年   215篇
  1992年   165篇
  1991年   108篇
  1990年   139篇
  1989年   97篇
  1988年   96篇
  1987年   44篇
  1986年   15篇
  1985年   4篇
  1984年   1篇
  1983年   1篇
  1981年   1篇
  1980年   1篇
  1979年   4篇
  1978年   3篇
  1977年   1篇
  1956年   2篇
  1955年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
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   
942.
943.
944.
This paper presents a new hierarchical and coordinative control method for reactive power optimization in large-scale interconnected power systems. It combines the interconnection forecast method for hierarchical control in large-scale steady state industrial systems with the incremental linear programming method for reactive power optimization in real time. The results of applying the method to power system examples show that the method not only solves the problem of high dimension in order, but also keeps the advantages of the incremental linear programming method. The proposed method is also suitable for the security analysis of reactive power correction in large-scale interconnected power systems.  相似文献   
945.
This paper has applied the var cost to the theory of spot price.An augmented Lagrange method is employed to develop the exact model of spot price of active power and reactive power,and the physical means of Lagrange multipliers are explained.The numerical examples are given to demonstrate the validity of the proposed model.  相似文献   
946.
947.
This poper sets up a new Neural Network Fuzzy inference Cooperation system which is based on fuzzy inference principle in Expert Systems,take advantage of the powerful learning function, the little sensitivity to input layer's samples,and the fast convergence and so on in FCBP and take advantage of the good sort property and good suit property to fuzzy value in MFART Network.  相似文献   
948.
Based on introducing fieldbus and fieldbus control system, in this paper, a distributed monitoring system for city wastewater treatment network based on LonWorks is given, the construction, function and character of this network are analyzed.  相似文献   
949.
This paper analyzes the current situation of university students' credit evaluation and set up an evaluation index system of university students' credit to compensate a loan.Based on this index system,this paper sets up a matter-element evaluation model on the individual credit of university students loan by means of extensible engineering method.The grade of individual credit and the index for evaluating the level of individual credit are made as matter-element,meanwhile,the classical field,the segment field,the weight coefficient are obtained.Dependence function is established based on the grade of individual credit and then the grade is judged by calculating the synthetic dependence degree.Finally,this paper presents the evaluation method by giving an example.This method is simple in calculation,reasonable in evaluation with high applicability.  相似文献   
950.
Application system generally refers to all kinds of computer information system. It aims at improving the sharing and application of the resource. The resource in application system usually means data resource. For computer management and maintenance, there are not only data resource, but also program resource and network resource. Effective management of this resource is key to ensure proper work of the application system. In this paper, the basic pattern and policy for resource management is put forward and a method to build and realize the resource layer that lies between database layer and application layer is to be found. This management layer, which skillfully connects the application system with resource and establishes good base for application and exploitation of system, is named as resource management system.  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