全文获取类型
收费全文 | 24739篇 |
免费 | 918篇 |
国内免费 | 33篇 |
专业分类
电工技术 | 329篇 |
综合类 | 38篇 |
化学工业 | 5655篇 |
金属工艺 | 380篇 |
机械仪表 | 477篇 |
建筑科学 | 1309篇 |
矿业工程 | 100篇 |
能源动力 | 621篇 |
轻工业 | 1888篇 |
水利工程 | 233篇 |
石油天然气 | 71篇 |
无线电 | 1818篇 |
一般工业技术 | 4504篇 |
冶金工业 | 4531篇 |
原子能技术 | 196篇 |
自动化技术 | 3540篇 |
出版年
2023年 | 214篇 |
2022年 | 359篇 |
2021年 | 567篇 |
2020年 | 338篇 |
2019年 | 431篇 |
2018年 | 535篇 |
2017年 | 463篇 |
2016年 | 633篇 |
2015年 | 558篇 |
2014年 | 749篇 |
2013年 | 1419篇 |
2012年 | 1162篇 |
2011年 | 1511篇 |
2010年 | 1075篇 |
2009年 | 1014篇 |
2008年 | 1147篇 |
2007年 | 1085篇 |
2006年 | 944篇 |
2005年 | 761篇 |
2004年 | 745篇 |
2003年 | 659篇 |
2002年 | 563篇 |
2001年 | 428篇 |
2000年 | 362篇 |
1999年 | 402篇 |
1998年 | 752篇 |
1997年 | 553篇 |
1996年 | 442篇 |
1995年 | 411篇 |
1994年 | 377篇 |
1993年 | 362篇 |
1992年 | 269篇 |
1991年 | 196篇 |
1990年 | 269篇 |
1989年 | 260篇 |
1988年 | 215篇 |
1987年 | 224篇 |
1986年 | 226篇 |
1985年 | 265篇 |
1984年 | 224篇 |
1983年 | 223篇 |
1982年 | 207篇 |
1981年 | 194篇 |
1980年 | 168篇 |
1979年 | 193篇 |
1978年 | 164篇 |
1977年 | 185篇 |
1976年 | 231篇 |
1975年 | 160篇 |
1974年 | 123篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
Amit Chourasia Steve Cutchin Yifeng Cui Reagan W Moore Kim Olsen Steven M Day J Bernard Minster Philip Maechling Thomas H Jordan 《Computer Graphics and Applications, IEEE》2007,27(5):28-34
This study focuses on the visualization of a series of large earthquake simulations collectively called TeraShake. The simulation series aims to assess the impact of San Andreas Fault earthquake scenarios in Southern California. We discuss the role of visualization in gaining scientific insight and aiding unexpected discoveries. 相似文献
22.
This paper presents the current understanding of the flame retardant mechanism of Casico?. The study includes the flame retardant effect of each individual component: ethylene–acrylate copolymer, chalk and silicone elastomer, as well as the formation of an intumescent structure during heating. The flame retardant properties were investigated by cone calorimetry and oxygen index tests. To obtain insight into the flame retardant mechanism, heat treatment under different conditions has also been performed. The results indicate that the flame retardant mechanism of Casico is complex and is related to a number of reactions, e.g. ester pyrolysis of acrylate groups, formation of carbon dioxide by reaction between carboxylic acid and chalk, ionomer formation and formation of an intumescent structure stabilized by a protecting char. Special emphasis is given to the formation of the intumescent structure and its molecular structure as evaluated from 13C MAS‐NMR and 29Si MAS‐NMR, ESCA and XRD analysis. After treatment at 500°C the intumescent structure consists mainly of silicon oxides and calcium carbonate and after treatment at 1000°C the intumescent structure consists of calcium silicate, calcium oxide and calcium hydroxide. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
23.
Choosing a standard speed for visual inspection is difficult using standard work measurement techniques. This paper uses a different approach, taking a model of human functioning in inspection and deriving an optimum speed of working so as to balance the cost of time against the cost of errors. Random search is used as the model and both self-paced and externally-paced conditions are derived for multiple fault types. Optimization using a Golden Section search is used to provide optimum inspection speed. 相似文献
24.
Adrian Thomas Christopher D. Gilson Tanveer Ahmed 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,64(1):73-79
Equipment was developed to measure the time for complete gelling of sodium alginate fibres in calcium chloride solution, taken as the time to achieve maximum tensile strength. The effects of fibre diameter, alginate concentration, alginate composition and calcium chloride concentration on gelling time were investigated. A diffusional model, developed to predict the gelling time, agreed with experimental results except for the effect of calcium ion concentration which was modelled empirically. 相似文献
25.
26.
Youngjohn James R.; Larrabee Glenn J.; Crook Thomas H. 《Canadian Metallurgical Quarterly》1992,4(1):54
The authors attempt to provide a better understanding of the differences between the normal memory decline characteristic of age-associated memory impairment (AAMI) and the pathological decline typical of mild Alzheimer's disease (AD). Batteries of traditional memory tests and computer-simulated everyday-memory tests discriminated between the 2 groups, which were matched on age, gender, and education, with reasonable degrees of accuracy (87.5% and 88.4%, respectively). False positives were the most frequent classification errors when using either battery. These results indicate that it is possible to use ecologically valid memory assessment paradigms without sacrificing discriminant validity. The clinical significance of discriminating mild AD from AAMI is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
27.
28.
A modern concept of cost-effective digital signal processing hardware for measuring and analysing data from experiments investigating turbulent two-phase flows is presented. Using an array processor together with an appropriate analog-to-digital converter, conventional turbulence characteristics such as turbulence spectra, correlation functions, turbulence intensities and — scales can be evaluated in real time. 相似文献
29.
30.
Thomas Stieglitz Martin Schuettler Klaus Peter Koch 《IEEE engineering in medicine and biology magazine》2005,24(5):58-65
In the following article, the technologies to fabricate polyimide-based thin and flexible substrates with monolithically integrated electrode arrays and printed circuit boards (PCB) for hybrid electronic assemblies as well as an assembling technique that connects bare electronic dice with flexible PCBs are presented. The concept of modular, flexible biomedical microsystems as neural prostheses is introduced in general and described in detail in three examples. A cuff electrode with integrated multiplexer circuitry and standard implantable cables represents the combination of microtechnology with precision mechanics; a sieve electrode used as an implant in peripheral nerve regeneration studies demonstrates the next level of integration density but still uses a cable connection; and last, joint effort to fabricate the demonstrator of a vision prosthesis that is completely implantable in the eye with a wireless link for energy supply and data transmission is presented. System design, hybrid assembling technology, and flexible multilayer encapsulation using parylene and silicone rubber are the key components for creating a new generation of neural prostheses for complex and challenging new applications. 相似文献