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   8773篇
  免费   575篇
  国内免费   1209篇
林业   721篇
农学   677篇
基础科学   2060篇
  2295篇
综合类   3277篇
农作物   125篇
水产渔业   419篇
畜牧兽医   544篇
园艺   106篇
植物保护   333篇
  2024年   96篇
  2023年   223篇
  2022年   388篇
  2021年   377篇
  2020年   357篇
  2019年   436篇
  2018年   273篇
  2017年   453篇
  2016年   536篇
  2015年   397篇
  2014年   517篇
  2013年   497篇
  2012年   637篇
  2011年   639篇
  2010年   549篇
  2009年   472篇
  2008年   435篇
  2007年   480篇
  2006年   463篇
  2005年   355篇
  2004年   321篇
  2003年   263篇
  2002年   198篇
  2001年   188篇
  2000年   166篇
  1999年   122篇
  1998年   97篇
  1997年   101篇
  1996年   79篇
  1995年   88篇
  1994年   85篇
  1993年   64篇
  1992年   48篇
  1991年   55篇
  1990年   30篇
  1989年   29篇
  1988年   22篇
  1987年   9篇
  1986年   1篇
  1985年   1篇
  1984年   2篇
  1983年   1篇
  1982年   1篇
  1978年   2篇
  1974年   1篇
  1956年   1篇
  1955年   2篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Intrusion detection system is an essential component of network security protection mechanisms. Most intrusion detection system can not adapt the variation of network environment. Aiming at this problem, an adaptive strategy that composed of condition space and strategy space is proposed. The condition space describes the network environment and the strategy space describes the strategy. There is an exclusive strategy corresponds to a certain environment state in condition space. On the base of the adaptive strategy, an adaptive intrusion detection system based on agent and data mining is designed. The simulation experiments indicate that the adaptive strategy is effective.  相似文献   
92.
Larger quantities of data about flight performance and flight condition are recorded by flight data recorder (FDR) during the aircraft's flying. It is an importance task to make 3D flying animation from the data on the process of flight data. The design ideas and realizing methods about the software of flying animation system driven by the data from relation database are presented.  相似文献   
93.
The flowfield and temperature field are numerically Simulated by the mathematical model of the fluid flow and heat transfer in circular combustion chamber widened suddenly. The distributions and influence factors of the flow field and temperature field are studied in it. The results have the guiding significance for the design of combustion chamber. The mathematical models can serve as the quantitative analysis methods for design.  相似文献   
94.
Data warehouse is not the simply data accumulation of operational database. For exerting the function of data warehouse, the construction of data warehouse should be convenient for the data mining and business intelligent work, supply information access, analyze, and share for decision maker. The key to constructing a successful data warehouse is to fully understand the demand of end users from beginning to the end, search and storage data surround users motive closely. This paper first analyzes the data warehouse characteristic and the sort of data component, emphasizes in effective data loading methods and strategies from operational database to data warehouse, gives five sorts data loading methods.  相似文献   
95.
96.
97.
98.
Flowing dynamic characteristics and its temperature dynamic characteristics of a three-level sewage pipe network in Chongqing were analyzed. A mall's building whole year load was simulated. In the adverse condition of wastewater flow, the market construction peak discharge heat was compared with the sewage heat load, the balance between the most adverse flow and the building demand was found. Explored supply and demand matching method between urban sewage and city building load in flow adverse condition to take full advantage of the urban sewage cold and hot resources. the composite system was adeptcd to make up the most unfavorable flow time of sewage average heat load and the construction load difference; it also puts forward principle of load sharing and control strategy aimed at compound system.  相似文献   
99.
This article puts forward a 3 Layers Model for the communication between embedded system and PC. It is based on the speciality of them and the TCP/IP model. The model defines the communicate process of embedded system to be three layers: Transport Layer, Control Layer and Application Layer. Each layer serves for its higher-up. It can keep the efficiency and credibility of the communicate process and the authors prove and analyse that in the article. the concept of the model is also suitable for Bluetooth, IrDA and other kinds of communication about embedded system.  相似文献   
100.
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