全文获取类型
收费全文 | 19400篇 |
免费 | 1792篇 |
国内免费 | 1201篇 |
专业分类
电工技术 | 778篇 |
综合类 | 2594篇 |
化学工业 | 2929篇 |
金属工艺 | 978篇 |
机械仪表 | 1489篇 |
建筑科学 | 2236篇 |
矿业工程 | 784篇 |
能源动力 | 652篇 |
轻工业 | 1248篇 |
水利工程 | 890篇 |
石油天然气 | 1535篇 |
武器工业 | 350篇 |
无线电 | 1426篇 |
一般工业技术 | 1570篇 |
冶金工业 | 698篇 |
原子能技术 | 381篇 |
自动化技术 | 1855篇 |
出版年
2024年 | 79篇 |
2023年 | 203篇 |
2022年 | 362篇 |
2021年 | 496篇 |
2020年 | 571篇 |
2019年 | 475篇 |
2018年 | 465篇 |
2017年 | 673篇 |
2016年 | 759篇 |
2015年 | 862篇 |
2014年 | 1230篇 |
2013年 | 1120篇 |
2012年 | 1562篇 |
2011年 | 1698篇 |
2010年 | 1279篇 |
2009年 | 1283篇 |
2008年 | 1142篇 |
2007年 | 1410篇 |
2006年 | 1254篇 |
2005年 | 1011篇 |
2004年 | 861篇 |
2003年 | 732篇 |
2002年 | 565篇 |
2001年 | 515篇 |
2000年 | 415篇 |
1999年 | 283篇 |
1998年 | 253篇 |
1997年 | 169篇 |
1996年 | 138篇 |
1995年 | 110篇 |
1994年 | 101篇 |
1993年 | 68篇 |
1992年 | 60篇 |
1991年 | 38篇 |
1990年 | 28篇 |
1989年 | 26篇 |
1988年 | 17篇 |
1987年 | 7篇 |
1986年 | 10篇 |
1985年 | 7篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1977年 | 3篇 |
1964年 | 4篇 |
1959年 | 3篇 |
1955年 | 3篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
目的研究蛋类礼盒包装结构的缓冲性能。方法以蛋类尺寸为基础,建立可发性聚乙烯(expandable polyethylene. EPE)缓冲单元结构和组合结构,进行静态仿真分析和实验验证,比较结构在形状、叠合层数、组合形式等参数变化时的载荷与位移。结果结构层数变化相同时,单元结构的极限载荷从143N增加到236 N,组合结构的极限载荷从224 N增加到476 N,均呈近线性增长。结论蛋类礼盒包装中,组合结构的承载能力优于单元结构,通过单元结构的组合,可满足不同蛋类的包装要求。 相似文献
2.
Yasoub Eghbali Mahmoud Ferdosizade Naeiny 《International Journal of Communication Systems》2020,33(14)
In this paper, an off‐grid direction of arrival (DoA) estimation method is proposed for wideband signals. This method is based on the sparse representation (SR) of the array covariance matrix. Similar to the time domain DoA estimation methods, the correlation function of the sources was assumed to be the same and known. A new measurement vector is obtained using the lower‐left triangular elements of the covariance matrix. The DoAs are estimated by quantizing the entire range of continuous angle space into discrete grid points. However, the exact DoAs may be located between two grid points; therefore, this estimation has errors. The accuracy of DoA estimation is improved by the minimization of the difference between the new measurement vector and its estimated values. Simulation results revealed that the proposed method can enhance the DoA estimation accuracy of wideband signals. 相似文献
3.
As suggested by the uncanny valley hypothesis, robots that resemble humans likely elicit feelings of eeriness. Based on the psychological model of meaning maintenance, we expected that the uncanny valley experience could be mitigated through a fictional story, due to the meaning-generating function of narratives. A field experiment was conducted, in which 75 participants interacted with the humanlike robot Telenoid. Prior to the interaction, they either read a short story, a non-narrative leaflet about the robot, or they received no preliminary information. Eeriness ratings were significantly lower in the science fiction condition than in both other conditions. This effect was mediated by higher perceived human-likeness of the robot. Our findings suggest that science fiction may provide meaning for otherwise unsettling future technologies. 相似文献
4.
5.
针对现有海量点云可视化方法存在索引构建时间长、内存占用大等问题,研究一种八叉树索引结合OSG分页结点的快速可视化方法,可在占用较小内存的基础上快速建立点云索引并实时调度。采用八叉树索引结构对海量点云进行数据组织,建立各层级的八叉树结点并以文件映射的方式分块保存,对结点文件重组织转换为支持OSG渲染引擎的多分辨率点云数据。采用基于OSG分页结点的实时调度技术,对海量点云进行高质量可视化。与目前两款主流的点云数据处理商业软件进行实验对比分析,结果表明所提方法具有索引建立速度快、内存占用小等优点,同时可视化交互更加流畅,适用于各种配置计算机下海量点云数据的调度管理与实时可视化。 相似文献
6.
In line with findings on post-purchase food-choice regret, one can expect that pre-purchase anticipated regret with respect to forgone (non-chosen) alternatives has an impact on consumer food choices, especially when the choice is considered to be important. The traditional Random Utility Maximization (RUM) models for discrete choices may not fully capture this impact. This study investigates the usefulness and potential in the food domain of a discrete choice model that follows the regret minimization principle, the Random Regret Minimization (RRM) model, as an alternative and complement to existing RUM models. The two models are applied to consumer stated choices of cheese in a choice experiment. The study also investigates whether and to what extent a number of personality traits determine whether particular consumers rather choose according to utility-maximization, or regret-minimization principles. Results show that at the aggregate level the two models have a similar goodness of fit to the data and prediction ability. Still, each of them shows better fit for particular subgroups of consumers, based on personality traits. Hence, the present study reveals a potential for the RRM model applications in the food domain, and adds to the empirical literature supporting previous findings on the RRM model found in other contexts. Further research is needed to explore in which situations and for which consumer segments the RRM model is the most useful model. 相似文献
7.
8.
对CFG桩质量缺陷的探讨 总被引:2,自引:2,他引:0
根据具体工程的概况及水文地质条件,分析了CFG桩在地下水位出现大面积缩颈现象和复合地基载荷试验达不到设计要求的原因,并介绍了地基补强措施,以满足工程质量的要求。 相似文献
9.
阜阳地区石炭-二叠系煤系烃源岩特征 总被引:2,自引:0,他引:2
阜阳地区石炭-二叠系煤系地层发育,但由于勘探程度较低,对该区煤系地层烃源岩的生烃潜力认识不清,严重制约了该区的油气勘探。在已有资料的基础上,通过有机地球化学和有机岩石学方法并结合模拟实验,探讨了该区煤系烃源岩的生烃潜力。研究结果表明阜阳地区石炭-二叠系煤系烃源岩有机质丰度达到中等-好烃源岩标准,有机质类型以腐殖型为主,盆地模拟结果显示阜阳地区石炭-二叠系煤系地层油资源量为(30.47~152.33)×106t,气资源量为(266.7~1333.7)×108m3,展示阜阳地区石炭-二叠系煤系地层具有较好的生油气潜力。 相似文献
10.
A method and instruments based on it are proposed for the contact measurement of surface temperature when carrying out industrial experiments and when monitoring technological parameters. 相似文献