全文获取类型
| 收费全文 | 5875篇 |
| 免费 | 104篇 |
专业分类
| 公路运输 | 1333篇 |
| 综合类 | 1559篇 |
| 水路运输 | 1734篇 |
| 铁路运输 | 796篇 |
| 综合运输 | 557篇 |
出版年
| 2025年 | 8篇 |
| 2024年 | 4篇 |
| 2023年 | 25篇 |
| 2022年 | 97篇 |
| 2021年 | 135篇 |
| 2020年 | 97篇 |
| 2019年 | 47篇 |
| 2018年 | 388篇 |
| 2017年 | 324篇 |
| 2016年 | 315篇 |
| 2015年 | 71篇 |
| 2014年 | 122篇 |
| 2013年 | 216篇 |
| 2012年 | 321篇 |
| 2011年 | 480篇 |
| 2010年 | 508篇 |
| 2009年 | 367篇 |
| 2008年 | 464篇 |
| 2007年 | 527篇 |
| 2006年 | 388篇 |
| 2005年 | 301篇 |
| 2004年 | 121篇 |
| 2003年 | 128篇 |
| 2002年 | 85篇 |
| 2001年 | 93篇 |
| 2000年 | 75篇 |
| 1999年 | 52篇 |
| 1998年 | 39篇 |
| 1997年 | 34篇 |
| 1996年 | 37篇 |
| 1995年 | 21篇 |
| 1994年 | 13篇 |
| 1993年 | 17篇 |
| 1992年 | 17篇 |
| 1991年 | 14篇 |
| 1990年 | 7篇 |
| 1989年 | 10篇 |
| 1988年 | 2篇 |
| 1987年 | 2篇 |
| 1985年 | 3篇 |
| 1984年 | 2篇 |
| 1983年 | 2篇 |
排序方式： 共有5979条查询结果，搜索用时 15 毫秒
821.
以某款燃料电池轿车为对象,探讨了轿车碰撞时高压电安全的设计思路,阐述了其具体设计,并采用有限元法进行碰撞模拟对该车的高压电安全进行了验证.结果表明该车的高压电安全设计符合碰撞安全的要求.在此基础上对这类燃料电池轿车的碰撞高压电安全设计原则进行了总结. 相似文献
822.
通过分析船型设计与性能分析系统数据接口的现状,提出Maxsurf与Shipcad系统数据接口的技术方案。在研究数据接口开发环境的基础上,对数据接口转换软件进行详细设计、开发和验证。实例验证所设计的数据接口转换软件打通了数据流转通道,能提高设计效率,奠定了进一步实现舰船集成设计研发平台的基础。 相似文献
823.
黄民强 《现代城市轨道交通》2010,(4):11-13
结合我国土木工程建设的规模和技术特点,对岩土工程的发展及其学科分类进行了总结,并对新技术、新材料在岩土工程中的应用和促进情况进行了探讨。 相似文献
824.
通过对中国港口现状的分析,阐述了国家宏观调控与港口发展的关系。着眼于国家宏观调控对港口发展的重要影响作用,提出了中国港口未来发展的动态模式。 相似文献
825.
826.
以桥式起重机结构特点的分析为基础,结合参数化设计软件的模块化优势,划分桥式起重机主梁的结构模块,提高主要零部件的参数化效率.采用数据库技术对各参数进行管理,在模块化和参数化的设计条件下,探讨从三维参数化模型到实用工程图的自动调整技术.经实际应用验证,该项技术能大幅度提高桥式起重机主梁结构的设计效率和质量. 相似文献
827.
An adaptive sliding mode controller with a disturbance observer (ASMC-DO) is proposed for the control of a single-input and single-output (SISO) servo system which has uncertain parameters, nonlinear friction, disturbance and input saturation. It is difficult to choose the suitable value of the parameters. The newly designed adaptive method is used to reduce the effects of system time-varying parameters, such as the moment of inertia and the damp coefficient. The robustness of object is improved. A DO is selected to approximate the compound disturbance and to render the estimate error convergent in finite time. The stability and the convergence of the closed-loop system are proved by using the Lyapunov theory. Experimental results show that the proposed ASMC-DO can better satisfy the influence of variable parameters and external disturbance to the control precision of the SISO servo system than other two controllers. The effectiveness of the proposed controller is showed. The control input stability and robust performances of the input saturation system are enhanced and the chattering is reduced. 相似文献
828.
It has been a focus of debate for a large time on construction methods for large-span loess tunnel. Reasonable construction method has much effect on stability of tunnel and construction schedule. Deformation and failure of surrounding rock are quite complex. Associating with the large-span loess tunnel of Zhengzhou—Xi’an high-speed passenger rail line in China, large scale model test with geometric proportion 1:20 is applied to study on dynamic mechanical behavior of various construction methods. They include full-face excavation with support and no support, and benching method with support. It is found that pre-deformation and stress accumulation take place ahead of working face. The effects of three construction methods are further studied, particularly in terms of tunnel displacement and stress changes. It is revealed that benching method transfers load to an unexcavated area, limits horizontal deformation, reduces stress concentration effectively, lengthens the distance between location of peak for stress concentration and working face, and consequently increases stability. The model test results not only supply theoretical foundation for determination of reasonable construction method, but also can act as reference for similar tunnel and underground engineering construction. 相似文献
829.
In the field of 3D model matching and retrieval, an effective method for feature extraction is spherical harmonic or its mutations, and is acted on the spherical images. But the obtainment of spherical images from 3D models is very time-consuming, which greatly restrains the responding speed of such systems. In this paper, we propose a quantitative evaluation of the whole process and give a detailed two-sided analysis based on the comparative size between pixels and voxels. The experiments show that the resultant optimized parameters are fit for the practical application and exhibit a satisfactory performance. 相似文献
830.
The paper aims at the problem of multi-targets threat degree being hard to be evaluated accurately in complex air defense battlefield environments. Combined with multi-sensors information fusion and interval-valued intuitionistic fuzzy sets (IVIFS) theories, the target priority determination is studied. The score and accuracy functions of IVIFS are improved with thinking about the hesitating information in order to increase the rationality. Then, the influence factors of target priority and the nonlinear relationship between the influence factors and target priority are analyzed. Next, the algorithms for calculating the factor weights and sensor weights are given. Based on the theory of IVIFS and technique for order preference by similarity to an ideal solution (TOPSIS), two methods of target priority determination based on the IVIFS and TOPSIS are proposed. At last, an application example verifies the effectiveness and flexibility of the proposed algorithms. 相似文献