全文获取类型
收费全文 | 27853篇 |
免费 | 3593篇 |
国内免费 | 1982篇 |
专业分类
电工技术 | 2279篇 |
技术理论 | 1篇 |
综合类 | 2750篇 |
化学工业 | 3508篇 |
金属工艺 | 1865篇 |
机械仪表 | 2056篇 |
建筑科学 | 2137篇 |
矿业工程 | 1045篇 |
能源动力 | 851篇 |
轻工业 | 2775篇 |
水利工程 | 799篇 |
石油天然气 | 1208篇 |
武器工业 | 341篇 |
无线电 | 3343篇 |
一般工业技术 | 2727篇 |
冶金工业 | 1085篇 |
原子能技术 | 419篇 |
自动化技术 | 4239篇 |
出版年
2024年 | 99篇 |
2023年 | 528篇 |
2022年 | 1142篇 |
2021年 | 1714篇 |
2020年 | 1164篇 |
2019年 | 850篇 |
2018年 | 973篇 |
2017年 | 1060篇 |
2016年 | 917篇 |
2015年 | 1397篇 |
2014年 | 1854篇 |
2013年 | 1935篇 |
2012年 | 2321篇 |
2011年 | 2427篇 |
2010年 | 2101篇 |
2009年 | 1961篇 |
2008年 | 2111篇 |
2007年 | 1969篇 |
2006年 | 1699篇 |
2005年 | 1336篇 |
2004年 | 911篇 |
2003年 | 599篇 |
2002年 | 533篇 |
2001年 | 502篇 |
2000年 | 378篇 |
1999年 | 207篇 |
1998年 | 136篇 |
1997年 | 98篇 |
1996年 | 80篇 |
1995年 | 85篇 |
1994年 | 86篇 |
1993年 | 64篇 |
1992年 | 38篇 |
1991年 | 23篇 |
1990年 | 16篇 |
1989年 | 12篇 |
1988年 | 8篇 |
1987年 | 22篇 |
1986年 | 8篇 |
1985年 | 5篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 17篇 |
1979年 | 3篇 |
1974年 | 3篇 |
1970年 | 2篇 |
1969年 | 1篇 |
1959年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
11.
13.
目的以压路机操纵手柄为对象,探讨交互品质研究方法,改进用户体验。方法对交互品质进行解析,由用户体验与交互品质的关联性,提出基于用户体验的交互品质研究方法;面向压路机操纵手柄典型任务进行用户体验研究,梳理压路机手柄的操作流程,并对交互行为进行聚类分析,结合语义分析构建用户体验词库,运用半结构式访谈与问卷调查,以定量与定性方法相结合对驾驶员的操纵体验进行调研;以专家研讨的形式进行驾驶员的操纵体验向交互特征的映射,构建交互特征集,进而对操纵手柄的交互品质进行分析与阐释。结果得出了压路机操纵手柄的交互特征与交互品质。结论通过用户体验可以映射交互特征,得到了交互品质,对于从交互品质的角度指导交互设计提供了借鉴。 相似文献
14.
15.
Through a combined computational fluid dynamics and discrete element method approach, the effect of the operating parameters on the hydrodynamics and heat‐transfer properties of gas‐solid two‐phase flows in a spouted bed are extensively investigated. Considering the high velocity in the fountain region, gas turbulence is resolved by employing the large‐eddy simulation. The rolling friction model is adopted for more precise predictions of solid behavior near the wall. Subsequently, the gas‐solid flow patterns, gas‐solid velocities, and temperature evolution are investigated. Moreover, different operating conditions and geometry configurations are evaluated with respect to heat‐transfer performance. The results provide a fundamental understanding of heat‐transfer mechanisms in spouted beds. 相似文献
16.
Kun Luan Jianjun Liu Baozhong Sun Wei Zhang Jianbao Hu Xiaomeng Fang Chen Ming Erhong Song 《Ceramics International》2019,45(6):6812-6818
Carbon fiber reinforced ceramic owns the properties of lightweight, high fracture toughness, excellent shock resistance, and thus overcomes ceramic's brittleness. The researches on the advanced structure of astronautics, marine have exclusively evaluated the quasi-static mechanical response of carbon fiber reinforced ceramics, while few investigations are available in the open literature regarding elastodynamics. This paper reports the dynamic compressive responses of a carbon fiber reinforced silicon carbide (Cf/SiC) composite (CFCMC) tested by the material test system 801 machine (MTS) and the split Hopkinson pressure bar (SHPB). These tests were to determine the rate dependent compression response and high strain rate failure mechanism of the Cf/SiC composite in in-plane and out-plane directions. The in-plane compressive strain rates are from 0.001 to 2200?s?1, and that of the out-plane direction are from 0.001 to 2400?s?1. The compressive stress-strain curves show the Cf/SiC composite has a property of strain rate sensitivity in both directions while under high strain rate loadings. Its compressive stiffness, compressive stress, and corresponding strain are also strain rate sensitive. The compressive damage morphologies after high strain rate impacting show different failure modes for each loading direction. This study provides knowledge about elastodynamics of fiber-reinforced ceramics and extends their design criterion with a reliable evaluation while applying in the scenario of loading high strain rate. 相似文献
17.
In this study, 30 subjects were exposed to different combinations of air temperature (Ta: 24, 27, and 30°C) and CO2 level (8000, 10 000, and 12 000 ppm) in a high-humidity (RH: 85%) underground climate chamber. Subjective assessments, physiological responses, and cognitive performance were investigated. The results showed that as compared with exposure to Ta = 24°C, exposure to 30°C at all CO2 levels caused subjects to feel uncomfortably warm and experience stronger odor intensity, while increased mental effort and greater intensity of acute health symptoms were reported. However, no significant effects of Ta on task performance or physiological responses were found. This indicated that subjects had to exert more effort to maintain their performance in an uncomfortably warm environment. Increasing CO2 from 8000 to 12 000 ppm at all Ta caused subjects to report higher rates of headache, fatigue, agitation, and feeling depressed, although the results were statistically significant only at 24 and 27°C. The text typing performance and systolic blood pressure (SBP) decreased significantly at this exposure, whereas diastolic blood pressure (DBP) and thermal discomfort increased significantly. These effects suggest higher arousal/stress. No significant interaction effect of Ta and CO2 concentration on human responses was identified. 相似文献
18.
19.
面对当前严峻的全球性空气污染问题,如何改善住区空气质量成为住区规划与设计的重要内容之一.本文以寒冷地区郑州市分散式、片状集中式和带状集中式3类典型绿地布局的住区为研究对象,借助微气候观测,描述住区内PM25时空变化特征.进而采用相关性分析、中介效应分析和回归分析,逐步剖析空间形态参数与住区内PM2.5的关联,探究建筑和绿地布局对PM2.5浓度的综合影响,为住区冬季室外环境空气质量评价与优化提供依据.研究表明:1)建筑视图因子(BVF)、天空开阔度(SVF)与植物视图因子(TVF)对PM2.5浓度影响权重排序:TVF >BVF >SVF.TVF每增加10%,PM2.5浓度上升约20 μg/m3;2)BVF对PM2.5浓度的直接效应最强;SVF主要以相对湿度间接影响PM2.5浓度;3)分散式绿地布局空气环境均质稳定性最好,带状集中式次之,片状集中式最差. 相似文献
20.