全文获取类型
收费全文 | 1197篇 |
免费 | 25篇 |
专业分类
公路运输 | 327篇 |
综合类 | 375篇 |
水路运输 | 245篇 |
铁路运输 | 230篇 |
综合运输 | 45篇 |
出版年
2023年 | 3篇 |
2022年 | 14篇 |
2021年 | 33篇 |
2020年 | 27篇 |
2019年 | 12篇 |
2018年 | 15篇 |
2017年 | 9篇 |
2016年 | 14篇 |
2015年 | 31篇 |
2014年 | 37篇 |
2013年 | 72篇 |
2012年 | 74篇 |
2011年 | 80篇 |
2010年 | 84篇 |
2009年 | 95篇 |
2008年 | 94篇 |
2007年 | 118篇 |
2006年 | 102篇 |
2005年 | 76篇 |
2004年 | 28篇 |
2003年 | 23篇 |
2002年 | 24篇 |
2001年 | 28篇 |
2000年 | 16篇 |
1999年 | 17篇 |
1998年 | 15篇 |
1997年 | 9篇 |
1996年 | 15篇 |
1995年 | 16篇 |
1994年 | 11篇 |
1993年 | 7篇 |
1992年 | 6篇 |
1991年 | 8篇 |
1990年 | 5篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1984年 | 1篇 |
排序方式: 共有1222条查询结果,搜索用时 15 毫秒
921.
922.
采用天津地区常用材料制作碎石混凝土试块,进行超声回弹试验和压力试验,采集相关数据,进行4种函数模型的拟合回归,建立了天津地区碎石混凝土的超声回弹综合法地方测强曲线并进行了验证,误差分析和验证结果表明所建曲线满足相关规程的要求,为天津地区混凝土超声回弹综合法测强提供了可靠保证。 相似文献
923.
为研究加工工艺对盾构隧道环间锚式接头受力特性的影响,基于锚式接头荷载试验,采用ABAQUS有限元软件建立锚式接头的精细化模型。首先,通过与试验结果进行比较,验证数值模型的合理性与可靠性,并分析得出锚式接头各部件间的摩擦因数参考值。其次,研究锚式接头在拼装过程中所需的压力、接头达到破坏荷载时的张开量随摩擦因数和套环壁厚与插入间隙尺寸差的变化规律。最后,数值分析结果表明: 部件间的摩擦因数参考值取0.50比较合理;为保证锚式接头正常工作,加工时部件间的摩擦因数应为0.46~0.52,套环壁厚与插入间隙尺寸差应为-0.05~0.01 mm;锚式接头在加工过程中的加工精度要求较高。 相似文献
924.
国内直线电机城轨交通系统轨道技术标准探讨 总被引:6,自引:4,他引:2
针对国内城市轨道交通系统采用直线电机技术却无相应设计规范及标准这一情况,对其轨道系统的主要特点进行分析;采用理论计算和工程类比的方法,对钢轨动态下沉控制值、轨距加宽、轨底坡、曲线超高、扣件支承间距等轨道主要技术标准进行研究和探讨。 相似文献
925.
926.
927.
ZHANG Song-tao REN Guang 《船舶与海洋工程学报》2006,5(3):5-10
1 Introduction1 Recently, adaptive control approaches based on fuzzy neural network (FNN) have been studied in a lot of papers [1–4]. FNN combines the capability of fuzzy reasoning in handling uncertain information and the capability of artificial neural… 相似文献
928.
ZHANGHai-bin RENHui-long DAIYang-shan GEFei 《船舶与海洋工程学报》2004,3(1):7-13
A wave load computation approach in direct strength analysis of semi-submersible platform structures was presented in this paper. Considering the differences in shape of pontoon, column and beam, the combination of accumulative chord length cubic parameter spline theory and analytic method was adopted for generating the wet surface mesh of platform. The hydrodynamic coefficients of platform were calculated by the three-dimensional potential flow theory of the linear hydrodynamic problem for platform with low forward speed. The equation of platform motions was established and solved in frequency domain, and the responses of wave-induced loads on the platform can be obtained. With the interpolation method being utilized, the pressure loads on shell elements for finite element analysis(FEA) were converted from those on the hydrodynamic computation mesh, which pave the basis for FEA with commercial software. A computer program based on this method has been developed ,and a calculation example of semi-submersible platform was illustrated. Analysis results show that this method is a satisfying approach of wave loads computation for this kind of platform. 相似文献
929.
好的生产线布局将为高效率的作业从根本上打下良好的基础,因此设计一个良好的生产线布局至关重要。U型布局目前被公认为是最高效率的生产线布局方法,其能够适应随着市场的变化而不断调整的生产节拍,并且在生产淡季可以节省人力资源。内饰五六分装区分装产品多、零件杂、工作区域小,产品切换时步行浪费时间多,为了消除这些浪费,提高生产效率,利用U型布局优化现场,提高了作业区域面积的利用,缩短了产品切换步行距离,降低了中间在制品。 相似文献
930.
Tie-Qiang Bi Chang-Ling Ren Prakash Chaudhary Xin-Hua Liao Xiang-Ming Che 《西安交通大学学报(英文版)》2010,22(3):208-210,F0003
Objective To compare and evaluate the efficacy of diagnosis and excision for appropriately selected breast multi-focal lesions and solitary lesion by ultrasound-guided vacuum-assisted biopsy (UGVAB). Methods Among 392 appropriately selected patients, 187 patients with multi-focal lesions and 205 patients with solitary lesion were treated by the 8-gauge UGVAB from May 2007 to June 2009. All lesions were removed as completely as possible. The patients with benign pathology underwent physical and ultrasound examinations at one week and 6 months after procedure. Results During the procedure, only three patients had vasovagal syncope and twenty others complained of other intraoperative discomfort. An accurate pathological diagnosis was obtained in all lesions. There was no apparent false-negative result among the 696 lesions with benign pathology at a follow-up of 6 months after procedure. The rates of malignant or premalignant pathology, postoperative complications and residual lesions in patients with multi-focal lesions were higher than those in patients with solitary lesion. If each lesion was considered as a subject of study, there was no significant difference between the two groups. Conclusion UGVAB is an effective method for diagnosis and excision of appropriately selected breast multi-focal lesions and can be used routinely. 相似文献