全文获取类型
收费全文 | 26830篇 |
免费 | 1805篇 |
国内免费 | 2555篇 |
专业分类
林业 | 1766篇 |
农学 | 1420篇 |
基础科学 | 1284篇 |
2640篇 | |
综合类 | 13536篇 |
农作物 | 1966篇 |
水产渔业 | 1124篇 |
畜牧兽医 | 4304篇 |
园艺 | 1972篇 |
植物保护 | 1178篇 |
出版年
2024年 | 228篇 |
2023年 | 576篇 |
2022年 | 1230篇 |
2021年 | 1281篇 |
2020年 | 1145篇 |
2019年 | 1113篇 |
2018年 | 818篇 |
2017年 | 1308篇 |
2016年 | 868篇 |
2015年 | 1292篇 |
2014年 | 1381篇 |
2013年 | 1688篇 |
2012年 | 2370篇 |
2011年 | 2377篇 |
2010年 | 2210篇 |
2009年 | 1869篇 |
2008年 | 2000篇 |
2007年 | 1813篇 |
2006年 | 1507篇 |
2005年 | 1255篇 |
2004年 | 807篇 |
2003年 | 406篇 |
2002年 | 490篇 |
2001年 | 456篇 |
2000年 | 413篇 |
1999年 | 162篇 |
1998年 | 15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 | 10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 229 毫秒
231.
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
232.
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
233.
234.
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
235.
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
236.
Housing industry is a prop industry with great potential, but it is restricted by shortage of funds. So it is necessary to probe the financing system of housing industrialization in China. This paper puts forward a financing plan for the international cooperative project in industrialized housing in Chongqing. Furthermore, it investigates the concrete financing system of the whole housing industry. 相似文献
237.
238.
The solution of polarization field strength in ellipsoid and a homogeneous dielectric in condition of a constant external field is obtained with strict derivation and ellipsoidal coordinate. The conclusion that some textbooks given: the direction of polarization field strength with the direction of external field holds strict anti-parallel must be supplemented with additive certain conditions, otherwise it will not be correct. By means of the latticework and the step change calculation, the angle value of polarization vector with the external field is calculated and the changing situation about the angle value with the change of three half axes of ellipsoid is analysied. 相似文献
239.
Many factors affect the propagation of ultra high frequency(UHF) signals caused by partial discharge(PD) on the waveforms and energy of signals in transformer.To investigate the relationshi Pof factors and UHF signals,simulation model of transformer for PD study are established.UHF signals in simulation model of transformer caused by PD are calculated using finite difference time domain method.By means of amplitude and cumulative energy plot of simulation signals,and combing the measured result,the following factors:distance between PD source and detection position,different metallic conductor position around detection position and iron core and winding are researched,which contribute to comprehend the propagation characteristic of UHF signals and detect UHF signals accurately. 相似文献
240.