全文获取类型
收费全文 | 760篇 |
免费 | 50篇 |
国内免费 | 16篇 |
专业分类
电工技术 | 39篇 |
综合类 | 68篇 |
化学工业 | 51篇 |
金属工艺 | 26篇 |
机械仪表 | 82篇 |
建筑科学 | 106篇 |
矿业工程 | 45篇 |
能源动力 | 35篇 |
轻工业 | 36篇 |
水利工程 | 10篇 |
石油天然气 | 25篇 |
武器工业 | 22篇 |
无线电 | 32篇 |
一般工业技术 | 57篇 |
冶金工业 | 64篇 |
原子能技术 | 13篇 |
自动化技术 | 115篇 |
出版年
2024年 | 1篇 |
2023年 | 8篇 |
2022年 | 18篇 |
2021年 | 19篇 |
2020年 | 15篇 |
2019年 | 13篇 |
2018年 | 11篇 |
2017年 | 24篇 |
2016年 | 30篇 |
2015年 | 35篇 |
2014年 | 58篇 |
2013年 | 39篇 |
2012年 | 54篇 |
2011年 | 68篇 |
2010年 | 56篇 |
2009年 | 50篇 |
2008年 | 46篇 |
2007年 | 54篇 |
2006年 | 46篇 |
2005年 | 40篇 |
2004年 | 27篇 |
2003年 | 13篇 |
2002年 | 19篇 |
2001年 | 10篇 |
2000年 | 15篇 |
1999年 | 9篇 |
1998年 | 5篇 |
1997年 | 5篇 |
1996年 | 8篇 |
1995年 | 6篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1977年 | 1篇 |
1976年 | 3篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有826条查询结果,搜索用时 15 毫秒
21.
Explaining the Formation of Online News Startups in France and the United States: A Field Analysis
下载免费PDF全文
![点击此处可从《The Journal of communication》网站下载免费的PDF全文](/ch/ext_images/free.gif)
This article examines the differential formation of online news startups in Toulouse, France, and Seattle, United States. While Seattle is home to many startups, in Toulouse there have been just 4—and only 1 continues publishing. Drawing on Bourdieu's field theory, we argue that amount and types of capital held by journalists in the 2 cities varied as a result of differences in journalism's position in the field of power. These differences shaped the extent of startup formation in each city and structured journalists' capacities to convert their capital into the resources needed to form startups (e.g., funding, credentials, partnerships). These findings are positioned in relation to literatures on journalism innovation and comparative media. 相似文献
22.
With organisations facing significant challenges to remain competitive, Business Process Improvement (BPI) initiatives are often conducted to improve the efficiency and effectiveness of their business processes, focussing on time, cost, and quality improvements. Event logs which contain a detailed record of business operations over a certain time period, recorded by an organisation's information systems, are the first step towards initiating evidence-based BPI activities. Given an (original) event log as a starting point, an approach to explore better ways to execute a business process was developed, resulting in an improved (perturbed) event log. Identifying the differences between the original event log and the perturbed event log can provide valuable insights, helping organisations to improve their processes. However, there is a lack of automated techniques and appropriate visualisations to detect the differences between two event logs. Therefore, this research aims to develop visualisation techniques to provide targeted analysis of resource reallocation and activity rescheduling. The differences between two event logs are first identified. The changes between the two event logs are conceptualised and realised with a number of visualisations. With the proposed visualisations, analysts are able to identify resource- and time-related changes that resulted in a cost reduction, and subsequently investigate and translate them into actionable items for BPI in practice. Ultimately, analysts can make use of this comparative information to initiate evidence-based BPI activities. 相似文献
23.
《International Journal of Hydrogen Energy》2022,47(57):24107-24118
Vehicle fires in the tunnel are a great threat to the safe operation of the tunnel. Due to the rapid development of the hydrogen economy, the fire due to the hydrogen leakage could not be avoided and may bring great damage to the passengers and infrastructure. Due to the large difference between pool fires of traditional fossil-fueled and jet fires of hydrogen-powered vehicles, it is in doubt whether the existing longitudinal ventilation design could still be effective for the safety issue of hydrogen powered vehicles. To solve this problem, it is necessary to compare temperature characteristics of hydrogen-powered and traditional vehicle fires with and without longitudinal ventilations. In present work, we conducted a numerical investigation to discuss the different temperature distributions of traditional and hydrogen-fueled vehicle fires. Results indicate that the high temperature zone of the pool fire only exists above the ceiling of the vehicle. For hydrogen-powered vehicle fire, the high-speed hydrogen jet with the strong inertial force could push the hot smoke flows back to the ground. The ceiling temperature of hydrogen-powered vehicle fire is larger since hydrogen-powered vehicle has a larger heat release rate and the fire hazard of jet fires bring more danger compared with the pool fire. Although the temperature stratification is also obvious for the hydrogen-powered vehicle fire, the air temperature in the lower region could be heated and still high enough to bring a great damage to the passengers’ lives. This is quite different with the traditional pool fire. In addition, the critical ventilation velocity is also discussed. The theoretical equation could well predicted the critical ventilation velocity of traditional vehicle fires. For hydrogen-powered vehicle fires, the critical ventilation velocity could reach up to 6 m/s. The theoretical equation could not well predict the critical ventilation velocity of hydrogen-powered vehicle fires due to exist of hydrogen jet fires. 相似文献
24.
《Advanced Powder Technology》2020,31(7):2973-2990
Interaction between granular solids and confining structures is an elementary problem encountered in subsurface structural design and bulk solids storing and handling. A classic scenario is uni-axial compression of granular solids in a deformable cylindrical container. Despite being apparently simple in loading condition, the understanding of this scenario remains limited, mainly due to complex interactive deformation between the two components via frictional interfaces. This paper comparatively examines such a uni-axial compression particulate system by a laboratory experiment and two different numerical approaches, namely, continuum finite element method (FEM) and linked discrete-finite element method (linked DEM-FEM). In the continuum FEM approach, two intendedly chosen simple material models, linear elastic and porous elastic models, are attempted. The comparative study reveals that the majority of resultant characteristics show satisfactory agreement amongst the numerical predictions and the experimental measurements. The simple elastic continuum FEM models can hence be a useful alternative in modelling such problems with mild structural flexibility under a monotonic loading scenario. However, precise prediction of some characteristics, such as lateral pressure ratio, may demand more elaborated material model or parameter selection. The enhancements needed for each numerical approach in order to achieve an improved result are further discussed. 相似文献
25.
A comparative study on UV light activated porous TiO2 and ZnO film sensors for gas sensing at room temperature 总被引:2,自引:0,他引:2
Hao ChenYuan Liu Changsheng Xie Jun WuDawen Zeng Yichuan Liao 《Ceramics International》2012,38(1):503-509
In order to find a new approach for screening the photoactivated gas sensing materials with high sensitivity, a comparative study was carried out. With the simple technique of screen printing, TiO2 and ZnO were used to fabricate the UV light activated gas sensors which were applied at room temperature. To facilitate the simultaneous measurements of the current transients of the two materials, they were printed on the same alumina substrate. Compared with ZnO, TiO2 exhibited a superior performance to ethanol and formaldehyde gases. It was found that the responses of TiO2 increased with the concentration of test gas and amounted to 224 and 1700 to 100 ppm ethanol and formaldehyde gases, respectively, while the responses of ZnO to 100 ppm ethanol and formaldehyde gases were 0.14 and 1.5, respectively. The mechanism of such a huge difference between TiO2 and ZnO was discussed in detail. Furthermore, it is suggested that metal oxide semiconductor with lower photo-to-dark current ratio can achieve higher photoactivated gas sensitivity. 相似文献
26.
本文以具体工程实例深入分析了大粒径卵石地层特殊条件下明挖车站深基坑合理可行的止水方案,并详细对比分析了降水方案和止水方案的优劣,推荐降水方案,为类似工程提供了确定降、止水方案的综合分析方法,可供相关工程人员借鉴。 相似文献
27.
The roll-on-roll-off passenger ferry MV ESTONIA sank during the night of 28 September 1994 in the Baltic Sea. In October 2000, divers recovered two palm-sized test pieces from the front bulkhead of the wreck. The investigators analysed these specimens to determine whether there were any indications of deliberate blasting. Since the wreck had been submerged for almost six years, it was clear that chemical traces would not be present on the surfaces of the test pieces. Therefore, the investigators performed comparative tests on shipbuilding steel to find a microstructural criterion that exclusively characterises a blast. The shipyard Jos. L. Meyer, Germany, had built the ESTONIA and supplied shipbuilding steel plates similar to that used for building the vessel in 1979/1980. The comparative tests comprised mechanical tests, shot peening tests and blasting tests using different explosives. Testing demonstrated that blasting always formed twinned ferrite grains in the microstructure over the whole cross-section of each of the 8 mm thick comparative plates. Although one of the original test pieces of the ESTONIA showed deformation twins, this was only confined up to 0.4 mm underneath the surfaces and not spread over the whole cross-section. Comparative shot peening tests produced the very same pattern of subsurface deformation twins. Therefore, the twins detected in the microsection of the test pieces of the ESTONIA wreck traced back to the shot peening process performed by the shipyard in 1979/1980 and not to a deliberate blast. 相似文献
28.
29.
30.