全文获取类型
收费全文 | 23345篇 |
免费 | 1081篇 |
国内免费 | 52篇 |
专业分类
电工技术 | 284篇 |
综合类 | 30篇 |
化学工业 | 5042篇 |
金属工艺 | 538篇 |
机械仪表 | 496篇 |
建筑科学 | 1143篇 |
矿业工程 | 122篇 |
能源动力 | 715篇 |
轻工业 | 2116篇 |
水利工程 | 204篇 |
石油天然气 | 79篇 |
无线电 | 1923篇 |
一般工业技术 | 4108篇 |
冶金工业 | 3980篇 |
原子能技术 | 161篇 |
自动化技术 | 3537篇 |
出版年
2023年 | 136篇 |
2022年 | 248篇 |
2021年 | 376篇 |
2020年 | 294篇 |
2019年 | 365篇 |
2018年 | 487篇 |
2017年 | 502篇 |
2016年 | 564篇 |
2015年 | 470篇 |
2014年 | 707篇 |
2013年 | 1519篇 |
2012年 | 1035篇 |
2011年 | 1402篇 |
2010年 | 1016篇 |
2009年 | 1035篇 |
2008年 | 1154篇 |
2007年 | 1038篇 |
2006年 | 940篇 |
2005年 | 886篇 |
2004年 | 733篇 |
2003年 | 667篇 |
2002年 | 650篇 |
2001年 | 425篇 |
2000年 | 403篇 |
1999年 | 398篇 |
1998年 | 439篇 |
1997年 | 370篇 |
1996年 | 405篇 |
1995年 | 365篇 |
1994年 | 361篇 |
1993年 | 322篇 |
1992年 | 308篇 |
1991年 | 194篇 |
1990年 | 283篇 |
1989年 | 251篇 |
1988年 | 198篇 |
1987年 | 199篇 |
1986年 | 189篇 |
1985年 | 229篇 |
1984年 | 244篇 |
1983年 | 202篇 |
1982年 | 207篇 |
1981年 | 200篇 |
1980年 | 173篇 |
1979年 | 205篇 |
1978年 | 140篇 |
1977年 | 159篇 |
1976年 | 187篇 |
1975年 | 147篇 |
1973年 | 132篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Number entry is a ubiquitous activity and is often performed in safety- and mission-critical procedures, such as healthcare, science, finance, aviation and in many other areas. We show that Monte Carlo methods can quickly and easily compare the reliability of different number entry systems. A surprising finding is that many common, widely used systems are defective, and induce unnecessary human error. We show that Monte Carlo methods enable designers to explore the implications of normal and unexpected operator behaviour, and to design systems to be more resilient to use error. We demonstrate novel designs with improved resilience, implying that the common problems identified and the errors they induce are avoidable. 相似文献
2.
Zenan Yu Julian Moore Jean Calderon Lei Zhai Jayan Thomas 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(39):5289-5295
Cable‐shaped supercapacitors (SCs) have recently aroused significant attention due to their attractive properties such as small size, lightweight, and bendability. Current cable‐shaped SCs have symmetric device configuration. However, if an asymmetric design is used in cable‐shaped supercapacitors, they would become more attractive due to broader cell operation voltages, which results in higher energy densities. Here, a novel coil‐type asymmetric supercapacitor electrical cable (CASEC) is reported with enhanced cell operation voltage and extraordinary mechanical‐electrochemical stability. The CASECs show excellent charge–discharge profiles, extraordinary rate capability (95.4%), high energy density (0.85 mWh cm−3), remarkable flexibility and bendability, and superior bending cycle stability (≈93.0% after 4000 cycles at different bending states). In addition, the CASECs not only exhibit the capability to store energy but also to transmit electricity simultaneously and independently. The integrated electrical conduction and storage capability of CASECS offer many potential applications in solar energy storage and electronic gadgets. 相似文献
3.
4.
5.
6.
7.
Evaluation of the effect of processing on cocoa polyphenols: antiradical activity,anthocyanins and procyanidins profiling from raw beans to chocolate 下载免费PDF全文
Matteo Bordiga Monica Locatelli Fabiano Travaglia Jean Daniel Coïsson Giuseppe Mazza Marco Arlorio 《International Journal of Food Science & Technology》2015,50(3):840-848
The content and composition of anthocyanins and procyanidins in fermented cocoa beans (from different geographic origins: Ecuador, Cameroon, Ivory Coast, Ghana and Nigeria), roasted nibs, cocoa mass and chocolate were determined, beside the determination of the total antiradical capacity. Concerning geographic origin, cocoa beans and processed products from Ecuador showed the highest levels of anthocyanins, followed by Nigeria and Cameroon. Generally, as cocoa beans were further processed, the levels of anthocyanins and flavan‐3‐ols decreased. The largest observed losses of phenolics occurred during roasting. A progressive decreasing trend in polyphenol concentration was observed in the other processed samples as well. Despite the original content of polyphenols in raw cocoa beans, technological processes imply a significant impact on cocoa quality, confirming the need of specific optimisation to obtain high value chocolate. 相似文献
8.
Hassan Hajjaj Gerard Goma Jean M. François 《International Journal of Food Science & Technology》2015,50(8):1731-1736
In submerged cultures performed in chemically defined fermentation medium containing glucose and glutamate, the growth and production of water‐soluble red pigments and citrinin by the filamentous fungus Monascus ruber were studied under various carbon/nitrogen (C/N) ratios. The specific production of the red pigments was optimal at a glucose/glutamate ratio of about 10 and then steadily decreased at higher C/N ratio. In contrast, the production of the mycotoxin increased with increased C/N with an optimum in the range of 30–45. In a fed‐batch mode, it was also found that the production of pigments was not favoured in fed‐batch mode by feeding the medium with glucose while keeping the C/N ratio lower than 10. This low production likely resulted from concurrent high accumulation of L‐malic acid that was reported to inhibit this production. In contrast, this mode of cultivation was rather favourable for the production of the mycotoxin. 相似文献
9.
Greg A. Breed Paul M. Severns Andrew M. Edwards 《Journal of the Royal Society Interface》2015,12(103)
Lévy flights have gained prominence for analysis of animal movement. In a Lévy flight, step-lengths are drawn from a heavy-tailed distribution such as a power law (PL), and a large number of empirical demonstrations have been published. Others, however, have suggested that animal movement is ill fit by PL distributions or contend a state-switching process better explains apparent Lévy flight movement patterns. We used a mix of direct behavioural observations and GPS tracking to understand step-length patterns in females of two related butterflies. We initially found movement in one species (Euphydryas editha taylori) was best fit by a bounded PL, evidence of a Lévy flight, while the other (Euphydryas phaeton) was best fit by an exponential distribution. Subsequent analyses introduced additional candidate models and used behavioural observations to sort steps based on intraspecific interactions (interactions were rare in E. phaeton but common in E. e. taylori). These analyses showed a mixed-exponential is favoured over the bounded PL for E. e. taylori and that when step-lengths were sorted into states based on the influence of harassing conspecific males, both states were best fit by simple exponential distributions. The direct behavioural observations allowed us to infer the underlying behavioural mechanism is a state-switching process driven by intraspecific interactions rather than a Lévy flight. 相似文献
10.