全文获取类型
收费全文 | 3083篇 |
免费 | 214篇 |
国内免费 | 115篇 |
专业分类
电工技术 | 118篇 |
综合类 | 314篇 |
化学工业 | 308篇 |
金属工艺 | 185篇 |
机械仪表 | 701篇 |
建筑科学 | 197篇 |
矿业工程 | 227篇 |
能源动力 | 133篇 |
轻工业 | 37篇 |
水利工程 | 18篇 |
石油天然气 | 36篇 |
武器工业 | 42篇 |
无线电 | 211篇 |
一般工业技术 | 244篇 |
冶金工业 | 191篇 |
原子能技术 | 2篇 |
自动化技术 | 448篇 |
出版年
2024年 | 8篇 |
2023年 | 23篇 |
2022年 | 55篇 |
2021年 | 85篇 |
2020年 | 96篇 |
2019年 | 41篇 |
2018年 | 50篇 |
2017年 | 92篇 |
2016年 | 116篇 |
2015年 | 126篇 |
2014年 | 300篇 |
2013年 | 199篇 |
2012年 | 354篇 |
2011年 | 326篇 |
2010年 | 200篇 |
2009年 | 187篇 |
2008年 | 147篇 |
2007年 | 151篇 |
2006年 | 143篇 |
2005年 | 128篇 |
2004年 | 108篇 |
2003年 | 115篇 |
2002年 | 80篇 |
2001年 | 69篇 |
2000年 | 51篇 |
1999年 | 43篇 |
1998年 | 41篇 |
1997年 | 22篇 |
1996年 | 16篇 |
1995年 | 11篇 |
1994年 | 6篇 |
1993年 | 1篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1987年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1961年 | 1篇 |
1958年 | 2篇 |
1957年 | 1篇 |
排序方式: 共有3412条查询结果,搜索用时 15 毫秒
101.
介绍了适合国内焦化企业振动式压浮煤机构的研制过程,该设备不仅能够均匀压实和刮平煤饼、减轻工人劳动强度,而且提高了装煤车的工作自动化,给厂家带来一定的经济效益。 相似文献
103.
The efficient utilization of expensive rolling-stock has become imperative for all railroads. In this paper, we study the combined empty and loaded train-scheduling problem for the upcoming dedicated freight corridors in India. Existing optimization models either do not consider the simultaneous optimization of the loaded and empty flows or are not solvable for large railroads. Our model is the first of its kind to incorporate link capacity constraints in an IP formulation for this operational level problem. A simulated annealing algorithm hybridized with a constructive heuristic is proposed as the solution method. The computational experiments show that the proposed heuristic performs well both in terms of runtime and solution quality. 相似文献
104.
Evaluation of a large dish‐type concentrator solar lighting system for underground car park 下载免费PDF全文
Duofu Song Hui Lv Jun Liao Wenjuan Huang Sihao Huang Chunfu Cheng Huiliang Zhou Yuehong Su Saffa Riffat 《国际能源研究杂志》2018,42(6):2234-2245
To utilize solar energy more efficiently and reduce lighting power consumption in underground public spaces such as car park, a large dish‐type concentrator solar lighting system is put forward along with its evaluation, which is a unique design to apply a laminated layer of beam split thin‐film coating and thin‐film solar cells onto the dish reflector. The collected sunlight is split into 2 parts, one being reflected into a fiber optical bundle and transmitted for daylighting, while the rest being absorbed by solar cells for electricity generation as the other way to replenish daylighting. A set of 4 solar lighting systems using 3.28‐m diameter dish are designed to meet the lighting requirement in a 1771‐m2 underground car park. A mathematical model is adopted to calculate the output power and conversion efficiency of solar cells distributed on the parabolic dish surface. The indoor illuminance distribution is given by lighting simulation. The results indicate that the average daylight illuminance in the car park can vary between 62.7 and 284 lx on February 25, 2016 and between 62.7 and 353 lx on August 17, 2016 for 2 chosen days, respectively. For the presented design, the electricity produced by solar cells is just enough to power light‐emitting diodes for lighting meeting a criterion at night. Considering about 19% conversion efficiency of solar cells and the efficacy of 129.5 lm/W of light‐emitting diodes, the hybrid solar lighting system can have about 40% utilization ratio of solar energy, so it can be concluded that a sufficient lighting provision can be provided by the proposed large dish‐type concentrator solar lighting system for applications in underground car park. 相似文献
105.
In automotive paint shops, changes of colors between consecutive production orders cause costs for cleaning the painting robots. It is a significant task to re-sequence orders and group orders with identical color as a color batch to minimize the color changeover costs. In this paper, a Color-batching Resequencing Problem (CRP) with mix bank buffer systems is considered. We propose a Color-Histogram (CH) model to describe the CRP as a Markov decision process and a Deep Q-Network (DQN) algorithm to solve the CRP integrated with the virtual car resequencing technique. The CH model significantly reduces the number of possible actions of the DQN agent, so that the DQN algorithm can be applied to the CRP at a practical scale. A DQN agent is trained in a deep reinforcement learning environment to minimize the costs of color changeovers for the CRP. Two experiments with different assumptions on the order attribute distributions and cost metrics were conducted and evaluated. Experimental results show that the proposed approach outperformed conventional algorithms under both conditions. The proposed agent can run in real time on a regular personal computer with a GPU. Hence, the proposed approach can be readily applied in the production control of automotive paint shops to resolve order-resequencing problems. 相似文献
106.
《Ergonomics》2012,55(7):1131-1136
Thirty Canadian police officers, divided into six groups, participated in the redesign of the interior of the patrol car. Three of the groups consisted of individuals having a history of low back disease. The effect of participating in a design process on the characteristics of the final design and on the perception of the low back pain was studied in a semi-experimental setting. The participants developed a strong commitment to the participatory design process, which was reflected in their productions. The differences between participants with and without a history of a low back disease was not marked. The former tended to stress posture-related elements in their analysis and design. 相似文献
107.
Concerns about air quality and global warming have led to numerous initiatives to reduce emissions. In general, emissions are proportional to the amount of fuel consumed, and the amount of fuel consumed is a function of speed, distance, acceleration, and weight of the vehicle. In urban areas, vehicles must often travel at the speed of traffic, and congestion can impact this speed particularly at certain times of day. Further, for any given time of day, the observations of speeds on an arc can exhibit significant variability. Because of the nonlinearity of emissions curves, optimizing emissions in an urban area requires explicit consideration of the variability in the speed of traffic on arcs in the network. We introduce a shortest path algorithm that incorporates sampling to both account for variability in travel speeds and to estimate arrival time distributions at nodes on a path. We also suggest a method for transforming speed data into time-dependent emissions values thus converting the problem into a time-dependent, but deterministic shortest path problem. Our results demonstrate the effectiveness of the proposed approaches in reducing emissions relative to the use of minimum distance and time-dependent paths. In this paper, we also identify some of the challenges associated with using large data sets. 相似文献
108.
为满足客户日新月异的技术及运营需求,对车联网服务能力进行完善,发掘4G在新一代车联网应用中牵引作用,面向前装市场推出以云管端一体化为核心的和车连产品,引导车联网行业新变革. 相似文献
109.
结构整体分析时嵌固端的确定、地基基础设计中的差异沉降控制、超长地下室的防开裂措施是大底盘多塔高层设计中的关键性技术问题。本文主要探讨了大底盘多塔地下室的差异沉降协调技术。 相似文献
110.