全文获取类型
收费全文 | 26735篇 |
免费 | 1792篇 |
国内免费 | 2542篇 |
专业分类
林业 | 1737篇 |
农学 | 1411篇 |
基础科学 | 1269篇 |
2623篇 | |
综合类 | 13518篇 |
农作物 | 1957篇 |
水产渔业 | 1120篇 |
畜牧兽医 | 4295篇 |
园艺 | 1967篇 |
植物保护 | 1172篇 |
出版年
2024年 | 231篇 |
2023年 | 571篇 |
2022年 | 1218篇 |
2021年 | 1268篇 |
2020年 | 1140篇 |
2019年 | 1103篇 |
2018年 | 809篇 |
2017年 | 1299篇 |
2016年 | 863篇 |
2015年 | 1284篇 |
2014年 | 1378篇 |
2013年 | 1686篇 |
2012年 | 2367篇 |
2011年 | 2373篇 |
2010年 | 2207篇 |
2009年 | 1865篇 |
2008年 | 1993篇 |
2007年 | 1808篇 |
2006年 | 1503篇 |
2005年 | 1249篇 |
2004年 | 805篇 |
2003年 | 404篇 |
2002年 | 490篇 |
2001年 | 456篇 |
2000年 | 413篇 |
1999年 | 161篇 |
1998年 | 14篇 |
1997年 | 12篇 |
1996年 | 13篇 |
1995年 | 9篇 |
1994年 | 8篇 |
1993年 | 9篇 |
1992年 | 11篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 9篇 |
1986年 | 7篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1981年 | 4篇 |
1976年 | 1篇 |
1965年 | 1篇 |
1964年 | 1篇 |
1963年 | 1篇 |
1962年 | 5篇 |
1957年 | 1篇 |
1956年 | 4篇 |
1955年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
221.
With the study of minbus's accelerated exterior noise control,the principle of sound intensity measurement was applied,the sound intensity of a minbus's surface noise was tested,and the surface noise distribution was presented.Several identification of noise source methods including sound power,sound intensity contour map,frequency spectrum were used together for surface noise analysis and study.Engine radiation noise and exhaust noise was identified as the major noise sources.On the contrary,car body vibration noise,tyre noise,transmission agent noise,air admission noise just occupied a little proportion of surface sound radiation energy.The research provides the reliable basis to determine main projects of minibus's accelerated exterior noise control. 相似文献
222.
The application of lock-up clutch slip control balances the fuel economy and drivability, and greatly improves the performance of hydraulic automatic transmission. The structure of the lock-up clutch and the friction material of lock-up clutch lining are discussed, a detailed research on varying characteristic due to engaging time during the lock-up clutch engagement is developed, too. By applying the slip control, lower fuel consumption is achieved. 相似文献
223.
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
224.
Based on the theory of the K map simplification of logical function(KSLF),this article releases a ICAI Realization for KSLF.Providing three kinds of teaching style:commonness, teaching, practice.This product,wich supports for the K map simplification with random item,is not only helpful to the construction of the curriculum of digital circuit ,but also to the design for digital application system.Under the practice method, This product's guides,checks,and corrects the student's whole process forthe proceeding of KSLF automaticly under the teaching method. 相似文献
225.
Control Strategy and Simulation Study on NiMH Battery Quick Charging for Regenerative Braking of HEV
Based on the result of NiMH battery performance experiments, changing trend of maximal temperature and difference in temperature of HEV NiMH battery in different SOC and different charging current is analyzed. Considering the working situation of HEV NiMH battery and the theory of battery quick charging, a control strategy for NiMH battery quick charging is described which adapts to HEV regenerative braking system based on Mascc law. By Modeling and simulating the process of NiMH battery quick charging with this strategy, constant voltage charge method and constant current charge method, validates this control strategy. 相似文献
226.
Complexity of mutual act and different sensation of different tourists are important factors influencing regional tourism resources evaluation. Fuzzy mathematic method can be used to up quantitative evaluation method on tourism resources evaluation. Taking Wushan Small Three Gorges as an example, the author carries out the evaluation of the tourism resources in the Three Gorges Reservoir. At the same time, the authors consider that five factors, such as improvement of the comunication of tourism resources, quickening the Steps of urbanization in reservior area, must be done well. 相似文献
227.
汽车是人机协同控制的复杂系统,基于NI PXIe8108实时控制器、PXI7842R数据采集卡、模拟驾驶输入设备及相关软硬件搭建了驾驶模拟仿真系统;用LabVIEW编程语言建立了车辆动力学模型;用虚拟引擎Unity3D软件开发了视景系统;并通过数据库技术使仿真过程与视景系统相结合,实现仿真过程与三维动画实时视景系统的数据交互。结果表明:通过人在环路模拟驾驶仿真实验,使仿真过程中引入了驾驶模拟操纵,实现了人在环路的人机交互式仿真,得到汽车相关性能仿真结果,为驾驶过程中人和汽车协同控制仿真和极端工况下的仿真,提供了一种安全、可靠的人车协同控制仿真环境。 相似文献
228.
229.
To develop the public traffic and setup a city form coordinated with the development of the public traffic has become a common sense in the full achievement of the city sustainable development. Due to the particularity of the exploration procedure and some difficulties in urban development, the policy on developing public traffic has not been realized in our country. Now it is on edge to solve these problems, particularly in the new area of development. In this article, the authors intend to find a practical way of establishing a ciity development mode with adapting the public traffic development by contrasting Lujiazui new area in Shanghai and the new east area in Chongqing. 相似文献
230.
According to the needs of setting up a professional system based on motorcycle design,the CBR(case based reasoning) and RBR(rule based reasoning) methods are introduced.After discussing the difference between the two kinds of reasoning,a method of integrating them into the motorcycle design flow is put forward to realize the design reusable technology and improve the design efficiency,by using the CBR in the step of selecting the similar motorcycle and the RBR in project's modification according to correlative rules. 相似文献