全文获取类型
收费全文 | 29820篇 |
免费 | 1396篇 |
专业分类
公路运输 | 8365篇 |
综合类 | 7698篇 |
水路运输 | 7243篇 |
铁路运输 | 6688篇 |
综合运输 | 1222篇 |
出版年
2024年 | 117篇 |
2023年 | 187篇 |
2022年 | 547篇 |
2021年 | 1029篇 |
2020年 | 1028篇 |
2019年 | 595篇 |
2018年 | 388篇 |
2017年 | 590篇 |
2016年 | 700篇 |
2015年 | 1055篇 |
2014年 | 2295篇 |
2013年 | 1534篇 |
2012年 | 2704篇 |
2011年 | 2813篇 |
2010年 | 2019篇 |
2009年 | 1894篇 |
2008年 | 1845篇 |
2007年 | 2637篇 |
2006年 | 2251篇 |
2005年 | 1413篇 |
2004年 | 966篇 |
2003年 | 636篇 |
2002年 | 416篇 |
2001年 | 406篇 |
2000年 | 242篇 |
1999年 | 142篇 |
1998年 | 115篇 |
1997年 | 116篇 |
1996年 | 113篇 |
1995年 | 79篇 |
1994年 | 72篇 |
1993年 | 59篇 |
1992年 | 48篇 |
1991年 | 46篇 |
1990年 | 37篇 |
1989年 | 26篇 |
1988年 | 17篇 |
1987年 | 8篇 |
1986年 | 9篇 |
1985年 | 11篇 |
1984年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
691.
A cybernetics model of manufacturing execution system(MES CM) was proposed and studied from the viewpoint of cybernetics.Combining with the features of manufacturing system, the MES CM was modeled by"generalized modeling"method that is discussed in large-scale system theory.The mathematical model of MES CM was constructed by the generalized operator model, and the main characteristics of MES CM were analyzed. 相似文献
692.
Multi-stand roll forming is a process that has very complicated deformation behaviour and shows significant nonlinearity.In this paper, the sensitivity analysis of parameters for multi-stand roll forming was performed via a new booting finite element method(FEM) model.Compared with the most of simulation, the new model is more consistent with production process and can account for the effects of roll rotating speed.Based on the model, the process of an open section channel formed with 10 passes was simulated and the sensitivity analysis was conducted with orthogonal experiment design combined FEM model.The multi-stand roll forming process can be efficiently analyzed by the new booting model.And sensitivity analysis shows the hardening exponent plays an important role in controlling the quality of the products. 相似文献
693.
The parameter values which actually change with the circumstances, weather and load level etc.produce great effect to the result of state estimation. A new parameter estimation method based on data mining technology was proposed. The clustering method was used to classify the historical data in supervisory control and data acquisition (SCADA) database as several types. The data processing technology was impliedto treat the isolated point, missing data and yawp data in samples for classified groups. The measurement data which belong to each classification were introduced to the linear regression equation in order to gain the regression coefficient and actual parameters by the least square method. A practical system demonstrates the high correctness, reliability and strong practicability of the proposed method. 相似文献
694.
695.
路面评价体系需要考虑到诸多因素,而且实现方法不一而足。从统计学角度出发,将投影追踪模型应用到该领域,以投影寻踪模型作为理论方法,通过遗传算法来实现模型求解。实例描述了该方法应用的关键步骤,并指出对于数据量充分、影响因素明确的准真系统,采用投影寻踪模型进行方案决策更具有客观性。 相似文献
696.
短时交通流预测是实现交通流诱导的关键技术之一。短时交通流因为其不确定性等特点而使其预测很复杂。通过实地调查获取的交通流量数据,分别采用移动平均法、指数平滑法、AR模型法3种交通流预测方法进行短时交通流量预测,并通过不同的评价指标对上述3种方法的预测效果进行评价,得出AR模型方法的预测效果优于其他2种方法。 相似文献
697.
公路工程项目成本控制现状分析 总被引:1,自引:1,他引:0
结合工程实践,通过对公路施工企业成本管理客观及主观现状分析,论述了成本管理的具体内容,抓住成本管理的关键环节并采取相应的措施,实施有效的公路工程项目成本管理,以指导公路施工企业项目成本管理并提高企业竞争能力。 相似文献
698.
699.
To improve the braking safety of automobiles, the author studied the effect of differential brake on the stabilities. To analyze the mechanical characteristics of differential brake, automotive subsystem models were built by applying ADAMS/CAR, and automotive mechanics simulation model was built by setting the main subsystems such as body, engine and brake. The simulation model studied the distribution mode of three kinds of differential brake, and beeline braking stability and turning braking stability were simulated. It shows that differential brake can amend turning shortage of automobile brake and improve its braking stability, but the effect of automobile mass on its braking stability is great. So the distribution mode of braking force and the effect of mass change should be considered while differential brake is applied. 相似文献
700.
行政法与行政诉讼法教学法探析 总被引:1,自引:0,他引:1
“行政法与行政诉讼法学”是一门复杂的有较强理论性但又必须和社会实际相结合的课程。要提高该课程的教学质量,改善教学效果,文中提出了案例教学法、多媒体技术与模拟法庭教学法。 相似文献