全文获取类型
收费全文 | 6499篇 |
免费 | 275篇 |
专业分类
公路运输 | 1611篇 |
综合类 | 2042篇 |
水路运输 | 1821篇 |
铁路运输 | 785篇 |
综合运输 | 515篇 |
出版年
2024年 | 24篇 |
2023年 | 29篇 |
2022年 | 161篇 |
2021年 | 235篇 |
2020年 | 148篇 |
2019年 | 87篇 |
2018年 | 393篇 |
2017年 | 355篇 |
2016年 | 309篇 |
2015年 | 158篇 |
2014年 | 229篇 |
2013年 | 274篇 |
2012年 | 436篇 |
2011年 | 552篇 |
2010年 | 577篇 |
2009年 | 422篇 |
2008年 | 483篇 |
2007年 | 543篇 |
2006年 | 389篇 |
2005年 | 365篇 |
2004年 | 126篇 |
2003年 | 126篇 |
2002年 | 87篇 |
2001年 | 91篇 |
2000年 | 63篇 |
1999年 | 21篇 |
1998年 | 14篇 |
1997年 | 8篇 |
1996年 | 14篇 |
1995年 | 13篇 |
1994年 | 17篇 |
1993年 | 7篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1990年 | 5篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1984年 | 2篇 |
排序方式: 共有6774条查询结果,搜索用时 31 毫秒
991.
This paper is a think piece on variations in the structure of stated preference studies when modelling the joint preferences
of interacting agents who have the power to influence the attribute levels on offer. The approach proposed is an extension
of standard stated choice methods, known as ‘stated endogenous attribute level’ (SEAL) analysis. It allows for interactive
agents to adjust attribute levels off a base stated choice specification that are within their control, in an effort to reach
agreement in an experimental setting. This accomplishes three goals: (1) the ability to place respondents in an environment
that more closely matches interactive settings in which some attribute levels are endogenous to a specific agent, should the
modeller wish to capture such behaviour; (2) the improved ability of the modeller to capture the behaviour in such settings,
including a greater wealth of information on the related interaction processes, rather than simply outcomes; and (3) the expansion of the set of situations that the modeller can investigate using experimental
data.
相似文献
John M. RoseEmail: |
992.
为了适应21世纪科技进步对人才知识的能力与素质的高要求。适应快速发展的高职教育实践教学的要求,培养学生动手能力,迫使现有的课程体系、教学内容、特别是实验与工程实践环节必须改革。从而构建机械基础教学新体系,建立以功能为内涵的机械基础与CAD教学实验中心迫在眉捷。 相似文献
993.
994.
针对武器装备系统战损的抢修排序问题,应用改进层次分析法(AHP)确定指标权重的同时,并提出了战损装备抢修排序的递阶层次结构模型;然后运用灰色聚类方法,构造评价函数,综合决策战损装备抢修排序。通过实例验证,将改进AHP与灰色聚类方法相结合,取得了较为满意的结果,为战场指挥员抢修决策提供帮助。 相似文献
995.
996.
An autonomous underwater vehicle (AUV) must use an algorithm to plan its path to distant, mobile offshore objects. Because
of the uneven distribution of obstacles in the real world, the efficiency of the algorithm decreases if the global environment
is represented by regular grids with all of them at the highest resolution. The framed quadtree data structure is able to
more efficiently represent the environment. When planning the path, the dynamic object is expressed instead as several static
objects which are used by the path planner to update the path. By taking account of the characteristics of the framed quadtree,
objects can be projected on the frame nodes to increase the precision of the path. Analysis and simulations showed the proposed
planner could increase efficiency while improving the ability of the AUV to follow an object. 相似文献
997.
溃坝模拟的光滑粒子流体动力学方法及其粘性特性(英文) 总被引:1,自引:0,他引:1
Smoothed particle hydrodynamics (SPH) is a Lagrangian meshless particle method. It is one of the best method for simulating
violent free surface flows in fluids and solving large fluid deformations. Dam breaking is a typical example of these problems.
The basis of SPH was reviewed, including some techniques for governing equation resolution, such as the stepping method and
the boundary handling method. Then numerical results of a dam breaking simulation were discussed, and the benefits of concepts
like artificial viscosity and position correction were analyzed in detail. When compared with dam breaking simulated by the
volume of fluid (VOF) method, the wave profile generated by SPH had good agreement, but the pressure had only reasonable agreement.
Improving pressure results is clearly an important next step for research. 相似文献
998.
二维水翼型空化流的数值计算(英文) 总被引:2,自引:0,他引:2
In order to predict the effects of cavitation on a hydrofoil, the state equations of the cavitation model were combined with
a linear viscous turbulent method for mixed fluids in the computational fluid dynamics (CFD) software FLUENT to simulate steady
cavitating flow. At a fixed attack angle, pressure distributions and volume fractions of vapor at different cavitation numbers
were simulated, and the results on foil sections agreed well with experimental data. In addition, at the various cavitation
numbers, the vapor fractions at different attack angles were also predicted. The vapor region moved towards the front of the
airfoil and the length of the cavity grew with increased attack angle. The results show that this method of applying FLUENT
to simulate cavitation is reliable. 相似文献
999.
After an aerial object enters the water, physical changes to sounds in the water caused by the accompanying bubbles are quite complex. As a result, traditional signal analyzing methods cannot identify the real physical object. In view of this situation, a novel method for analyzing the sounds caused by an aerial object’s entry into water was proposed. This method analyzes the vibrational mode of the bubbles by using empitical mode decomposition. Experimental results showed that this method can efficiently remove noise and extract the broadband pulse signal and low-frequency fluctuating signal, producing an accurate resolution of entry time and frequency. This shows the improved performance of the proposed method. 相似文献
1000.
溃坝问题的数值仿真和实验(英文) 总被引:1,自引:0,他引:1
In this paper, two novel numerical computation methods are introduced which have been recently developed at Research Institute
for Applied Mechanics ( RIAM ), Kyushu University, for strongly nonlinear wave-body interaction problems, such as ship motions
in rough seas and resulting green-water impact on deck. The first method is the CIP-based Cartesian grid method, in which
the free surface flow is treated as a multi-phase flow which is solved using a Cartesian grid. The second method is the MPS
method, which is a so-called particle method and hence no grid is used. The features and calculation procedures of these numerical
methods are described. One validation computation against a newly conducted experiment on a dam break problem, which is also
described in this paper, is presented. 相似文献