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   22987篇
  免费   1302篇
  国内免费   1102篇
林业   4821篇
农学   1155篇
基础科学   1872篇
  3010篇
综合类   9048篇
农作物   859篇
水产渔业   1158篇
畜牧兽医   1606篇
园艺   425篇
植物保护   1437篇
  2024年   128篇
  2023年   386篇
  2022年   490篇
  2021年   674篇
  2020年   746篇
  2019年   876篇
  2018年   529篇
  2017年   717篇
  2016年   913篇
  2015年   831篇
  2014年   1264篇
  2013年   1462篇
  2012年   1972篇
  2011年   1930篇
  2010年   1400篇
  2009年   1484篇
  2008年   1328篇
  2007年   1373篇
  2006年   1163篇
  2005年   1078篇
  2004年   853篇
  2003年   734篇
  2002年   510篇
  2001年   507篇
  2000年   396篇
  1999年   299篇
  1998年   236篇
  1997年   202篇
  1996年   183篇
  1995年   141篇
  1994年   119篇
  1993年   95篇
  1992年   91篇
  1991年   87篇
  1990年   58篇
  1989年   62篇
  1988年   40篇
  1987年   19篇
  1986年   9篇
  1985年   5篇
  1955年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
251.
Basing eliminating on the idea that the generator who has the most influence on the power flow of line is mostly in favor of transmission congestion, the model of congestion management with the object of minimizing adjustments of bufions varied with generation outputs is proposed. It can eliminate the congestion effectively by judging the generators who should be adjusted and the amounts of adjustment. The test on IEEE-RTS24 buses system and other practical systems show that the proposed method is effective.  相似文献   
252.
In order to help tourists choose satisfying scenic spots, content hotels, convenient lines and convenient vehicles, vehicle monitoring control and scheduling management system in a scenic area is presented, which dispatches vehicle by appointments and the statistic of tourists at a sight spot and recommends the tour line by broadcasting in vehicle. Vehicle monitoring control and scheduling management system in a scenic area, a integrative vehicle management system, is an integration of GPS, GIS, trunked radio system, a management system of booking room and a tourist statistic system at a sight spot.  相似文献   
253.
By analyzing the process of enterprise information engineering construction and intra relationship among information system requirement, business process modeling, application system constructing and project management, one of 4 meta model composed of requirement engineering, process engineering, application system engineering and support engineering is proposed for enterprise information engineering. The developments and applications of the business processes and its application systems are integrated into the same development space and application space. Basing on this, a prototype system composed of requirement modeling environment, business process modeling environment, application system modeling environment, and support engineering environment has been designed and built, which is used for supporting enterprise information engineering constructing. It is valued for the enterprise information engineering construction in our country.  相似文献   
254.
The solution of the office automation system for the universities is given. The detail steps on developing an office automation system through Lotus Notes are described.  相似文献   
255.
This article presents an implement of component using COM technology for collecting environmental monitoring data in environment monitoring system. The component makes the separation of data collection and data analysis available.Simultaneously by using the interface of connectable object in COM,itmakes the cooperation of the environment monitoring software with other parts of fault management software available,and also the seamless connection.It improves the system's performance by adding extensibility and potential cooperatibility.  相似文献   
256.
In this paper the test results of mixed mode fracture of three kinds of brittle rock under two kinds of stress paths are reported. The fracture mechanism and failure patterns of brittle lock under different stress paths are discussed. Theory analysis and test results show that the Compression- Shear fracture criterion of brittle rock can be expressed:  相似文献   
257.
Bomsster is a key load-bearing part of railway lorry bogie.Because of its inherent defects casting-steel bomsster could not meet the demands of the heavy load,acceleration and security for lorry.So forging process is proposed to form it.The forming performance of forging-steel bomsster is analyzed.A forging technology is presented which realizes two forging-steel bomsster parts formed in one die.With the plastic forming simulation software DEFORM-3D,the simulation and optimization of the forming process of forging bomsster has been taken based on 3D rigid visco-plastic FEM theory.Optimized scheme has been used to direct the pilot product.The results of product's testing and application suggest that the new forging technology is feasible and the performance of the product is credibility and stabilization.The factory has realized large scale production of a series of forging-steel bomsster.Remarkable benefits of both economy and society have been achieved.  相似文献   
258.
The listed companies have strong motivation earnings management beforerights issue (RI) in order to achieve the qualification of equity refinancing. After dealed with a positive study on earnings management of RI in 242 Chinese list companies, it is discovered that Chinese RI firms have earnings management that is much more than developed securities market and other emerged securities market before announcing year, but there is not earnings management after announcing second third year, and it is discovered credit business is a main tool of earnings management.  相似文献   
259.
This paper focuses on the key tactics and technology in customization marketing of Third Party Logistics -design modularity of logistics product, which is be researched deeply. The modularity figure of logistics product, and depth management for modularity are constructed by adopting boston Matrix in order to avoid over-customized. Personality customization is realized through making up module differently for Third Party Logistics corporations, to satisfy the demand for customizing and responding the market fast.  相似文献   
260.
With the rapid increase of the Internet user and widely application of Web,the current network technology is facing great challenge. More and more multimedia operations occupy plenty of bandwidth,and result in the network congestion. Therefore,people begin to use QoS to utilize the bandwidth effectively,and ensure the transport of the emergent operation data. The paper introduces the protocols and basic components of QoS,then expatiates the conception and the basic principles of policy control QoS, moreover,emphasizes the structure model of policy control QoS and how it runs. At last,it introduces the transport process of data packets under the control of policies in a policy control QoS system,and how to make the policies in the real world.  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