全文获取类型
收费全文 | 2878篇 |
免费 | 105篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 15篇 |
综合类 | 9篇 |
化学工业 | 576篇 |
金属工艺 | 45篇 |
机械仪表 | 44篇 |
建筑科学 | 196篇 |
矿业工程 | 24篇 |
能源动力 | 72篇 |
轻工业 | 338篇 |
水利工程 | 38篇 |
石油天然气 | 8篇 |
无线电 | 148篇 |
一般工业技术 | 479篇 |
冶金工业 | 486篇 |
原子能技术 | 13篇 |
自动化技术 | 498篇 |
出版年
2023年 | 17篇 |
2022年 | 27篇 |
2021年 | 68篇 |
2020年 | 52篇 |
2019年 | 41篇 |
2018年 | 55篇 |
2017年 | 44篇 |
2016年 | 55篇 |
2015年 | 65篇 |
2014年 | 90篇 |
2013年 | 197篇 |
2012年 | 111篇 |
2011年 | 190篇 |
2010年 | 109篇 |
2009年 | 126篇 |
2008年 | 153篇 |
2007年 | 151篇 |
2006年 | 112篇 |
2005年 | 102篇 |
2004年 | 76篇 |
2003年 | 82篇 |
2002年 | 64篇 |
2001年 | 52篇 |
2000年 | 56篇 |
1999年 | 48篇 |
1998年 | 89篇 |
1997年 | 68篇 |
1996年 | 48篇 |
1995年 | 49篇 |
1994年 | 51篇 |
1993年 | 45篇 |
1992年 | 35篇 |
1991年 | 21篇 |
1990年 | 27篇 |
1989年 | 23篇 |
1988年 | 27篇 |
1987年 | 22篇 |
1986年 | 23篇 |
1985年 | 41篇 |
1984年 | 24篇 |
1983年 | 23篇 |
1982年 | 22篇 |
1981年 | 16篇 |
1980年 | 18篇 |
1979年 | 26篇 |
1978年 | 18篇 |
1977年 | 25篇 |
1976年 | 29篇 |
1975年 | 18篇 |
1974年 | 13篇 |
排序方式: 共有2989条查询结果,搜索用时 46 毫秒
1.
Abhendra K. Singh Kaitlyn Kahle Hannah James Allison L. Horner Daniel Villaflor Zach Benedict 《Ceramics International》2021,47(12):17268-17275
In this study the effects of high temperature and moisture on the impact damage resistance and mechanical strength of Nextel 610/alumina silicate ceramic matrix composites were experimentally evaluated. Composite laminates were exposed to either a 1050°C isothermal furnace-based environment for 30 consecutive days at 6 h a day, or 95% relative humidity environment for 13 consecutive days at 67°C. Low velocity impact, tensile and short beam strength tests were performed on both ambient and environmentally conditioned laminates and damage was characterized using a combination of non-destructive and destructive techniques. High temperature and humidity environmental exposure adversely affected the impact resistance of the composite laminates. For all the environments, planar internal damage area was greater than the back side dent area, which in turn was greater than the impactor side dent area. Evidence of environmental embrittlement through a stiffer tensile response was noted for the high temperature exposed laminates while the short beam strength tests showed greater propensity for interlaminar shear failure in the moisture exposed laminates. Destructive evaluations exposed larger, more pronounced delaminations in the environmentally conditioned laminates in comparison to the ambient ones. External damage metrics of the impactor side dent depth and area directly influenced the post-impact tensile strength of the laminates while no such trend between internal damage area and residual strength could be ascertained. 相似文献
2.
To overcome the drawbacks of solid microporous materials for CO2 capture, this proof‐of‐concept study demonstrates a low‐cost and rapid method for producing composites consisting of hypercrosslinked polymers (HCP) with a polyethyleneimine (PEI) binder. The resulting materials capture CO2 through physical and chemical absorption simultaneously. Compared with HCP, the composites exhibit higher CO2 uptake, higher volumetric density, and improved tolerance to water which is attributed to the PEI binder. 相似文献
3.
Quality of service has become today a major concern for operators of mobile communication networks. The massive development of networks and strong competition between operators has lead to the necessary and daily follow-up of network quality of service, a key factor for its subscriber’s fidelity. This article aims at presenting the optimization methodology and proposes its illustration with a case of RNO (Radio Network Optimisation) software usage, one of the Alcatel optimization toolchain component. After a short presentation of cellular network, the optimization basic principles are described. RNO software and its main functionnalities are then detailed before a last part dedicated to a real case of optimization done with RNO software. 相似文献
4.
5.
Colin Palmer 《International Journal of Project Management》1985,3(4):208-216
There are many ways in which quantitative decision models can be applied in project management. The introduction of a project evaluation review technique network model to the development of a school education service in the city of Delhi, India, is described. The reasons for choosing this method, its advantages and limitations are discussed. Examples of the information obtained from the model are presented and explained. 相似文献
6.
Across 2 experiments, a new experimental procedure was used to investigate attentional capture by animal fear-relevant stimuli. In Experiment 1 (N = 34), unselected participants were slower to detect a neutral target animal in the presence of a spider than a cockroach distractor and in the presence of a snake than a large lizard distractor. This result confirms that phylogenetically fear-relevant animals capture attention specifically and to a larger extent than do non-fear-relevant animals. In Experiment 2 (N = 86), detection of a neutral target animal was slowed more in the presence of a feared fear-relevant distractor (e.g., a snake for snake-fearful participants) than in presence of a not-feared fear-relevant distractor (e.g., a spider for snake-fearful participants). These results indicate preferential attentional capture that is specific to phylogenetically fear-relevant stimuli and is selectively enhanced in individuals who fear these animals. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
7.
Solidification time and heat treatment are known to have a large effect on the microstructure of cast aluminum alloys. This
study was conducted to quantify how the fatigue properties of a 319-type aluminum alloy are affected by solidification time
and heat treatment. Both porosity-containing (non-hot isostatically pressed (HIP)) and porosity-free (HIP) samples in the
T6 (“peak aged”) or T7 (“overaged”) heattreated conditions were tested. As the solidification time increased, the average
initiating pore diameter increased and stress-controlled fatigue life decreased. Heat treatment was observed to have a large
effect on fatigue properties of the HIP samples. However, in the non-HIP fatigue samples, heat treatment did not significantly
change the fatigue life or fatigue strength of the cast 319-type alloy. The absence of an influence of heat treatment on fatigue
response is attributed to the predominance of the microporosity in fatigue crack initiation in cast aluminum. 相似文献
8.
Learning Organizations in Construction 总被引:1,自引:0,他引:1
The transformation of organizations from production-oriented entities to proactive learning entities that continuously leverage the knowledge of the workforce is a primary objective of management researchers. This focus has significant relevance to the construction industry where production-related research has predominantly overshadowed organizational development research. As one effort to change this emphasis, the writers present a research effort designed to study current organization learning techniques and technologies fielded by organizations both inside and outside of the construction industry. Through a series of exploratory case studies, the writers developed a maturity model together with the Construction Industry Institute that provides construction organizations with a framework for developing a learning organization culture. The maturity model focuses on learning organization characteristics of leadership, processes and infrastructure, communication/collaboration, education, and culture at the organization, community, and individual levels. This paper introduces the results of that effort including a presentation of the learning organization maturity model, framework application, and the overall characteristics of a learning organization. 相似文献
9.
10.
Froggatt M.E. Allison S.G. Moore J.P. 《IEEE transactions on instrumentation and measurement》1996,45(1):123-126
This paper presents a method of correcting for unwanted phase shifts introduced by interchanging ultrasonic transducers and other measurement system components when using the pulsed phase-locked loop (PPLL) ultrasonic system. Theory is derived mathematically separating phase errors into their constituents. The relationship to a previously derived method of determining the number of periods into the tone-burst, at which the system samples, is established, and a method of adjusting this number to be an integer is presented. Implementation of the technology on a computer is demonstrated through experimental results on transducers of differing frequencies and diameters. Sensitivity to path-length is tested. This work has resulted in a straightforward means of calibrating transducers in conjunction with PPLL measurements using a single, fixed reference block 相似文献