全文获取类型
收费全文 | 59386篇 |
免费 | 6380篇 |
国内免费 | 4082篇 |
专业分类
电工技术 | 6220篇 |
技术理论 | 1篇 |
综合类 | 5478篇 |
化学工业 | 7706篇 |
金属工艺 | 3966篇 |
机械仪表 | 2800篇 |
建筑科学 | 3783篇 |
矿业工程 | 2391篇 |
能源动力 | 2721篇 |
轻工业 | 4119篇 |
水利工程 | 1841篇 |
石油天然气 | 3363篇 |
武器工业 | 685篇 |
无线电 | 7179篇 |
一般工业技术 | 5912篇 |
冶金工业 | 3632篇 |
原子能技术 | 1434篇 |
自动化技术 | 6617篇 |
出版年
2024年 | 279篇 |
2023年 | 867篇 |
2022年 | 1737篇 |
2021年 | 2037篇 |
2020年 | 2174篇 |
2019年 | 1781篇 |
2018年 | 1741篇 |
2017年 | 2288篇 |
2016年 | 2446篇 |
2015年 | 2496篇 |
2014年 | 3791篇 |
2013年 | 4158篇 |
2012年 | 4448篇 |
2011年 | 4683篇 |
2010年 | 3559篇 |
2009年 | 3477篇 |
2008年 | 3156篇 |
2007年 | 3842篇 |
2006年 | 3275篇 |
2005年 | 2867篇 |
2004年 | 2405篇 |
2003年 | 2030篇 |
2002年 | 1802篇 |
2001年 | 1511篇 |
2000年 | 1240篇 |
1999年 | 990篇 |
1998年 | 801篇 |
1997年 | 710篇 |
1996年 | 656篇 |
1995年 | 547篇 |
1994年 | 429篇 |
1993年 | 316篇 |
1992年 | 276篇 |
1991年 | 222篇 |
1990年 | 183篇 |
1989年 | 146篇 |
1988年 | 100篇 |
1987年 | 63篇 |
1986年 | 65篇 |
1985年 | 50篇 |
1984年 | 44篇 |
1983年 | 26篇 |
1982年 | 32篇 |
1981年 | 15篇 |
1980年 | 20篇 |
1979年 | 6篇 |
1978年 | 9篇 |
1975年 | 9篇 |
1964年 | 4篇 |
1959年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
ZHANG Xiao-hong 《通讯和计算机》2008,5(12):39-43
An online face recognition system is presented in the paper. To online face recognition system, we should consider the recognition rate, the image compression and image size. In the paper we researched the innovation technologies for face recognition system, including Kernel Principal Component Analysis (Kernel PCA), Delta low-pass wavelet filter, and face recognition algorithm using multiple images. Kernel PCA is derived to classify the characteristics of training images in the database. Delta low-pass wavelet filter is used to reduce the image size. A face recognition algorithm using multiple images is presented to improve the recognition rate. Simulation experiment shows that in the case of packet loss recognition rate is improved highly. 相似文献
92.
Andrey V. Kikhtenko Vladimir B. Goncharov Kirill I. Zamaraev 《Catalysis Letters》1993,21(3-4):353-360
Gas phase reactions of Mo+ and W+ ions with the molecules of various oxidants (NO, O2, N2O, CH2O, C2H4O) were studied using ion cyclotron resonance. In oxidation with N2O the mono-, di- and trioxide metal cations are formed consecutively. The trioxide MO3
+ ions of both metals react with CO to form CO2 and MO2
+ ions. In this way, catalytic reaction N2O + CO N2 + CO2 occurs in the gas phase with MoO3
+ /MoO2
+ and WO3
+/WO2
+ couples as catalysts. The rate constants have been measured for both stages of the catalytic cycle as well as for the stages of the catalyst preparation. Metal-oxygen bond energies were estimated for MoOx
+ and WOx
+ species with various x. The mechanism of CO oxidation with MoOx
+ and WOx
+ cations as catalysts in the gas phase is discussed in comparison with that for the oxidation over classical solid oxide catalysts. 相似文献
93.
Comments on J. J. Christensen-Szalanski and L. R. Beach's (see record 1984-21471-001) conclusion that the attention given to commentaries and replies to articles did not justify the extra space and argues that citation indexes do not measure the major usefulness of these commentaries. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
94.
开发了一种新的特性粘数分析方法 ,该方法采用熔体流动时间计算特性粘数 ,与经典特性粘数分析方法有很好的相关性且具有分析时间短、费用低、无污染等优点。 相似文献
95.
Ivan Bozovic 《Journal of Superconductivity》1991,4(2):193-197
A novel optical method for accurate monitoring of the carrier densityN in layered conductors is introduced. It is applied to several cuprate superconductors, and it is found thatT
c
doesnot scale withN. However, if the closely spaced pairs or triplets of CuO2 planes were coupled together to act as distinct metallic slabs, the relevant variable could ben, theslab carrier density. Indeed, we found thatT
c
does scale nicely withn. This suggests that high-T
c
superconductivity is effectively a two-dimensional phenomenon; it can occur in a cuprate slab which is only one unit cell thick. Finally, estimates are obtained for the length scales of localization of charge carriers:d 8 Å andd
2 Å in all the cuprates under study. 相似文献
96.
97.
98.
《Ergonomics》2012,55(6):1012-1021
For decades, research to quantify the effects of firefighting activities and personal protective equipment on physiology and biomechanics has been conducted in a variety of testing environments. It is unknown if these different environments provide similar information and comparable responses. A novel Firefighting Activities Station, which simulates four common fireground tasks, is presented for use with an environmental chamber in a controlled laboratory setting. Nineteen firefighters completed three different exercise protocols following common research practices. Simulated firefighting activities conducted in an environmental chamber or live-fire structures elicited similar physiological responses (max heart rate: 190.1 vs 188.0 bpm, core temperature response: 0.047°C/min vs 0.043°C/min) and accelerometry counts. However, the response to a treadmill protocol commonly used in laboratory settings resulted in significantly lower heart rate (178.4 vs 188.0 bpm), core temperature response (0.037°C/min vs 0.043°C/min) and physical activity counts compared with firefighting activities in the burn building.Practitioner Summary: We introduce a new approach for simulating realistic firefighting activities in a controlled laboratory environment for ergonomics assessment of fire service equipment and personnel. Physiological responses to this proposed protocol more closely replicate those from live-fire activities than a traditional treadmill protocol and are simple to replicate and standardise. 相似文献
99.
The present study compared the physiological responses and the subsequent cognitive performance when riding an electrically assisted (EB) versus a classical (CB) bicycle. Oxygen uptake, heart rate and leg extensor muscles electromyographic (EMG) activity were recorded in 10 subjects during a 30-min intermittent cycling exercise performed with EB versus CB. Cognitive performance was evaluated by a mail sorting test, performed at rest and after each cycling session. Averaged oxygen uptake and heat rate were significantly (P < 0.05) lower during EB cycling than during CB cycling. The EMG activities of the vastus lateralis, rectus femoris and gastrocnemius medialis muscles were significantly (P < 0.001) greater during CB cycling than during EB cycling. The time to complete the mail sorting test was significantly (P < 0.05) shorter after EB cycling than after CB cycling. Because EB cycling reduced muscle strains and physiological stress, it might offer benefits for those using bicycles in their work, such as postal workers and police officers. STATEMENT OF RELEVANCE: This study compared physiological and cognitive responses when riding an electrically assisted versus a classical bicycle. The results showed that the electrically assisted bicycle led to reduced muscle strains and physiological stress and, therefore, might offer benefits for those using bicycles in their work, such as postal workers and police officers. 相似文献
100.
《Ergonomics》2012,55(10):1503-1514
The primary objective of this paper was to compare in-shoe loading for different models of running shoe using measurements of force distribution. It was hypothesised that a shoe designed with minimal focus on cushioning would demonstrate significantly higher peak forces and rates of loading than running shoes designed with cushioning midsoles. Loading was compared using in-shoe peak forces for six footwear conditions. It was found that peak rate of loading at the heel provided clear distinctions between shoes. In support of the study hypothesis, the shoe with minimal focus on cushioning had a significantly higher rate of loading than all but one of the other test shoes. Data collected for midfoot and forefoot areas of the foot highlighted the importance of considering loading across the foot surface. The results of the present study demonstrate that pressure insoles provide a useful tool for the assessment of loading across the foot plantar surface for different footwear conditions. There are numerous models of running shoe for individuals to select from, with limited information available regarding the performance of the shoes during running. The current study demonstrates differences in loads across the foot plantar surface during running, indicating differences in performance for different footwear models. 相似文献