全文获取类型
收费全文 | 2857篇 |
免费 | 93篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 18篇 |
综合类 | 7篇 |
化学工业 | 407篇 |
金属工艺 | 81篇 |
机械仪表 | 42篇 |
建筑科学 | 149篇 |
矿业工程 | 12篇 |
能源动力 | 66篇 |
轻工业 | 296篇 |
水利工程 | 17篇 |
石油天然气 | 4篇 |
无线电 | 295篇 |
一般工业技术 | 382篇 |
冶金工业 | 688篇 |
原子能技术 | 18篇 |
自动化技术 | 472篇 |
出版年
2022年 | 19篇 |
2021年 | 58篇 |
2020年 | 27篇 |
2019年 | 43篇 |
2018年 | 60篇 |
2017年 | 67篇 |
2016年 | 81篇 |
2015年 | 40篇 |
2014年 | 58篇 |
2013年 | 145篇 |
2012年 | 116篇 |
2011年 | 157篇 |
2010年 | 117篇 |
2009年 | 114篇 |
2008年 | 142篇 |
2007年 | 139篇 |
2006年 | 123篇 |
2005年 | 94篇 |
2004年 | 84篇 |
2003年 | 59篇 |
2002年 | 75篇 |
2001年 | 64篇 |
2000年 | 41篇 |
1999年 | 41篇 |
1998年 | 144篇 |
1997年 | 96篇 |
1996年 | 72篇 |
1995年 | 55篇 |
1994年 | 44篇 |
1993年 | 53篇 |
1992年 | 28篇 |
1991年 | 24篇 |
1990年 | 22篇 |
1989年 | 27篇 |
1988年 | 29篇 |
1987年 | 30篇 |
1986年 | 18篇 |
1985年 | 29篇 |
1984年 | 24篇 |
1983年 | 28篇 |
1982年 | 23篇 |
1980年 | 18篇 |
1979年 | 12篇 |
1978年 | 14篇 |
1977年 | 15篇 |
1976年 | 26篇 |
1975年 | 34篇 |
1974年 | 14篇 |
1973年 | 12篇 |
1972年 | 15篇 |
排序方式: 共有2954条查询结果,搜索用时 46 毫秒
101.
Greg Perkins Ernest du Toit Greg Cochrane Grant Bollaert 《Energy Sources, Part A: Recovery, Utilization, and Environmental Effects》2016,38(24):3639-3646
Underground coal gasification (UCG) is a process which converts deep, un-mineable or difficult to mine coal resources into syngas which can then be converted into valuable end products such as electric power, liquid fuels, synthetic natural gas and chemicals. This paper provides a summary of the UCG operations conducted at the Chinchilla Demonstration Facility in Australia, focusing on gasifiers constructed using directional drilling. A number of the experiences and key lessons learned from operating multiple underground gasifiers over several years at the facility are described. Implications for the implementation in commercial projects using UCG are also discussed. Finally, the potential of UCG as a method for producing syngas from deep coal is discussed and some of the challenges and opportunities are summarized. 相似文献
102.
Matthew A. A. Grant Bart?omiej Wac?aw Rosalind J. Allen Pietro Cicuta 《Journal of the Royal Society Interface》2014,11(97)
Mechanical forces are obviously important in the assembly of three-dimensional multicellular structures, but their detailed role is often unclear. We have used growing microcolonies of the bacterium Escherichia coli to investigate the role of mechanical forces in the transition from two-dimensional growth (on the interface between a hard surface and a soft agarose pad) to three-dimensional growth (invasion of the agarose). We measure the position within the colony where the invasion transition happens, the cell density within the colony and the colony size at the transition as functions of the concentration of the agarose. We use a phenomenological theory, combined with individual-based computer simulations, to show how mechanical forces acting between the bacterial cells, and between the bacteria and the surrounding matrix, lead to the complex phenomena observed in our experiments—in particular the observation that agarose concentration non-trivially affects the colony size at transition. Matching these approaches leads to a prediction for how the friction between the bacteria and the agarose should vary with agarose concentration. Our experimental conditions mimic numerous clinical and environmental scenarios in which bacteria invade soft matrices, as well as shedding more general light on the transition between two- and three-dimensional growth in multicellular assemblies. 相似文献
103.
104.
Joel E. Fischer Andy Crabtree James A. Colley Tom Rodden Enrico Costanza 《Computer Supported Cooperative Work (CSCW)》2017,26(4-6):597-626
We present fieldwork findings from the deployment of an interactive sensing system that supports the work of energy advisors who give face-to-face advice to low-income households in the UK. We focus on how the system and the data it produced are articulated in the interactions between professional energy advisors and their clients, and how they collaboratively anticipate, rehearse, and perform data work. In addition to documenting how the system was appropriated in advisory work, we elaborate the ‘overhead cost’ of building collaborative action into connected devices and sensing systems, and the commensurate need to support discrete workflows and accountability systems to enable the methodical incorporation of the IoT into collaborative action. We contribute an elaboration of the social, collaborative methods of data work relevant to those who seek to design and study collaborative IoT systems. 相似文献
105.
In this paper, we propose a new technique to estimate wideband source directions from the sensor snapshots without requiring to know the number of sources present in the scenario. This work is motivated by the fact that the existing model order estimation (number of sources) techniques for wideband source scenario are either inaccurate or computationally expensive. Direction-of-arrival (DOA) estimation is realized using a beamformer framework which imposes nulls in the spatial spectrum along the source directions. The null width along the frequency axis is widened by introducing a new data dependent term into the optimization problem, thus achieving wideband capability. Furthermore, the temporal processing of the data snapshots drastically reduces the number of snapshots required for wideband DOA estimation. The effectiveness of the proposed formulation is studied with simulated experiments. 相似文献
106.
Simultaneous photocatalytic hydrogen production and CO2 reduction (to form CO and CH4) from water using methanol as a hole scavenger were investigated using silver-modified TiO2 (Ag/TiO2) nanocomposite catalysts. A simple ultrasonic spray pyrolysis (SP) method was used to prepare mesoporous Ag/TiO2 composite particles using TiO2 (P25) and AgNO3 as the precursors. The material properties and photocatalytic activities were compared with those prepared by a conventional wet-impregnation (WI) method. It was found that the samples prepared by the SP method had a larger specific surface area and a better dispersion of Ag nanoparticles on TiO2 than those prepared by the WI method, and as a result, the SP samples showed much higher photocatalytic activities toward H2 production and CO2 reduction. The optimal Ag concentration on TiO2 was found to be 2 wt%. The H2 production rate of the 2% Ag/TiO2–SP sample exhibited a six-fold enhancement compared with the 2% Ag/TiO2–WI sample and a sixty-fold enhancement compared with bare TiO2. The molar ratio of H2 and CO in the final products can be tuned in the range from 2 to 10 by varying the reaction gas composition, suggesting a viable way of producing syngas (a mixture of H2 and CO) from CO2 and water using the prepared Ag/TiO2 catalysts with energy input from the sun. 相似文献
107.
Wu He Xin Tian Andy Hung Vasudeva Akula Weidong Zhang 《Information Systems and E-Business Management》2018,16(3):579-600
This paper proposes a framework of using social media analytics to help study service quality. A case study was conducted to collect and analyze a data set which included nearly half million tweets related to two of the largest supermarkets in the United States: Walmart and Kmart. The results illustrate how businesses can leverage external open data to complement the traditional survey-based approaches in order to better understand and measure their service quality metrics by studying the online opinions of their customers. 相似文献
108.
109.
Magnetotactic bacteria (MTB) naturally synthesize magnetic nanoparticles that are wrapped in lipid membranes. These membrane‐bound particles, which are known as magnetosomes, are characterized by their narrow size distribution, high colloidal stability, and homogenous magnetic properties. These characteristics of magnetosomes confer them with significant value as materials for biomedical and industrial applications. MTB are also a model system to study key biological questions relating to formation of bacterial organelles, metal homeostasis, biomineralization, and magnetoaerotaxis. The similar size scale of nano and microfluidic systems to MTB and ease of coupling to local magnetic fields make them especially useful to study and analyze MTB. In this Review, a summary of nano‐ and microtechnologies that are developed for purposes such as MTB sorting, genetic engineering, and motility assays is provided. The use of existing platforms that can be adapted for large‐scale MTB processing including microfluidic bioreactors is also described. As this is a relatively new field, future synergistic research directions coupling MTB, and nano‐ and microfluidics are also suggested. It is hoped that this Review could start to bridge scientific communities and jump‐start new ideas in MTB research that can be made possible with nano‐ and microfluidic technologies. 相似文献
110.
As outlined in compression therapy literature, the performance of a compression textile can be characterized by its stiffness and interface pressure. In this study, an indirect approach for measuring pressure from a set of compression bandages and hosiery was developed, from which rigidity (EI) values were determined, and tension–elongation curves and pressure-elongation data were calculated. The calculated pressure values were compared against PicoPress sensor readings measured on 10 participants. Results showed that the correlation between both approaches varied among bandage and hosiery samples. 相似文献