全文获取类型
收费全文 | 40070篇 |
免费 | 1383篇 |
国内免费 | 65篇 |
专业分类
电工技术 | 421篇 |
综合类 | 29篇 |
化学工业 | 7704篇 |
金属工艺 | 792篇 |
机械仪表 | 801篇 |
建筑科学 | 2081篇 |
矿业工程 | 118篇 |
能源动力 | 1139篇 |
轻工业 | 3148篇 |
水利工程 | 449篇 |
石油天然气 | 120篇 |
武器工业 | 5篇 |
无线电 | 2822篇 |
一般工业技术 | 6680篇 |
冶金工业 | 7752篇 |
原子能技术 | 311篇 |
自动化技术 | 7146篇 |
出版年
2023年 | 222篇 |
2022年 | 461篇 |
2021年 | 703篇 |
2020年 | 482篇 |
2019年 | 646篇 |
2018年 | 820篇 |
2017年 | 738篇 |
2016年 | 863篇 |
2015年 | 793篇 |
2014年 | 1105篇 |
2013年 | 2536篇 |
2012年 | 1747篇 |
2011年 | 2199篇 |
2010年 | 1736篇 |
2009年 | 1641篇 |
2008年 | 1902篇 |
2007年 | 1886篇 |
2006年 | 1680篇 |
2005年 | 1516篇 |
2004年 | 1254篇 |
2003年 | 1212篇 |
2002年 | 1132篇 |
2001年 | 791篇 |
2000年 | 630篇 |
1999年 | 686篇 |
1998年 | 909篇 |
1997年 | 767篇 |
1996年 | 703篇 |
1995年 | 677篇 |
1994年 | 624篇 |
1993年 | 604篇 |
1992年 | 549篇 |
1991年 | 340篇 |
1990年 | 466篇 |
1989年 | 440篇 |
1988年 | 370篇 |
1987年 | 406篇 |
1986年 | 345篇 |
1985年 | 458篇 |
1984年 | 475篇 |
1983年 | 370篇 |
1982年 | 336篇 |
1981年 | 329篇 |
1980年 | 317篇 |
1979年 | 322篇 |
1978年 | 289篇 |
1977年 | 281篇 |
1976年 | 299篇 |
1975年 | 234篇 |
1974年 | 205篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
As if life isn't already crowded enough with obligations, “Tamagotchis” (virtual pets) would seem to be at odds with the Information Age, but cars, phones and TV-like appliances will become more like Tamagotchis as the friction-free economy once again expresses itself in tribalism. My premise is simple: the friction-free economy rewards retro-cultures that yearn to return to agrarian tribalism. Selling hi-tech products in this new economy becomes ritual, and the greater the ritual, the greater the financial rewards. Some may use different names-database marketing, targeting or niche marketing-but the key to expanding the computer industry will be to build a tribe around your brand and flaunt it. Successful product design and sales will increasingly require targeting products, services and ideas to various tribes. An idea long understood in the entertainment and services industry, this is only now becoming a computer industry mantra. The question is, how will this impact the design of future computer products? Study the Tamagotchi and other Christmas season best-sellers to find out 相似文献
102.
Rothenberg B.C. Brown J.E.C. Hurst P.J. Lewis S.H. 《Solid-State Circuits, IEEE Journal of》1997,32(5):713-721
A mixed-signal RAM decision-feedback equalizer (DFE) that operates at 90 Mb/s is described. In the analog domain, the DFE subtracts intersymbol interference caused by the past four outputs. The equalized signal is fed into a nonuniform flash analog-to-digital converter (ADC) to produce the decision output and error signal used to adapt the RAM contents in the digital domain. With a 5 V supply voltage, the power dissipation is 260 mW during steady-state operation. The active area is 4.5 mm2 in a 1 μm CMOS process 相似文献
103.
Duane J. Lewis 《Journal of the American Ceramic Society》1991,74(10):2410-2413
Mixed-oxide systems are of interest in a variety of technical ceramic applications. The key in many systems is to achieve a high degree of homogeneity, approaching the molecular level. A technique for producing mixed oxides via direct oxidation of mixtures of organometallic compounds is discussed as a potential route. Preliminary work performed on producing mullite is discussed. 相似文献
104.
There is ample evidence that people cannot generate random series when instructed to do so. Rather, they produce sequences with too few symmetries and long runs and too many alternations among events. The authors propose a psychological theory to account for these findings, which assumes that subjects generate nonrandom sequences that locally represent theoretical random series subject to a constraint on their short-term memory. Closed-form expressions are then derived for the major statistics that have been used to test for deviations from randomness. Results from 3 experiments with 2 and 3 equiprobable alternatives support the model on both the individual and group levels. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
105.
106.
Jue Donald; Meador Kimford J.; Zamrini Edward Y.; Allen Martha E.; Feldman Daniel S.; Loring David W. 《Canadian Metallurgical Quarterly》1992,6(4):331
Studied memory for visuospatial arrays in 28 male and 34 female healthy dextral adults (aged 20–90 yrs). 10 abstract figures were presented in each hemispace over a series of learning trials, and then delayed free recall of figure placement was obtained. Figures were misplaced significantly downward and leftward in both hemispaces. Both vertical and horizontal absolute error increased significanty with age, but no age effects on directional errors were observed. The increase in absolute error over age is consistent with decreased anterograde memory and visuospatial skills in the elderly. The directional errors are believed to result from an attentional shift toward proximal peripersonal space, in combination with attentional shifts from differential left vs right cerebral activation. Gender effects were also observed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
107.
David Sanborn Scott 《International Journal of Hydrogen Energy》2003,28(12):1303-1306
108.
Fault-accommodation with intelligent sensors 总被引:1,自引:0,他引:1
Giacomo Tortora Author Vitae Author Vitae David Clarke Author Vitae 《Automatica》2003,39(7):1227-1233
Optimal sensor fault-accommodation is considered for faults modelled by an increase in measurement noise. This noise is taken to be bounded and its probabilistic properties unknown. It is assumed that intelligent (e.g. self-validating) instrumentation is in use and estimates of the noise bounds are available. The fault-tolerant controller is designed to optimize a noise rejection and a nominal reference tracking index and leads to a mixed norm minimization problem (l1/l2). We exploit known results and a particular feedback configuration to show that it is possible to optimize simultaneously without a trade-off the two performance indices. The results are applied to systems where the presence of auxiliary measurements allows for an optimal fault-accommodation strategy. Using properties of the optimal solution, we define a factorization for the optimal controller alternative to the Youla parametrization, leading to an algorithm which is optimal, transparent and efficient. 相似文献
109.
David Duke 《Network Security》2003,2003(2):4-8
Anti-virus (AV) products and other fingerprint-based systems are typical of the applications used to enforce security. AV products are probably the first step that most organizations take to protect their systems and enhance security. Many small to medium organizations rely almost entirely on AV products. 相似文献
110.
Memorializes John Bissell (Jack) Carroll, an early leader in the development of psycholinguistics and a dominant contributor to psychometrics and the study of individual differences in cognitive abilities. His seminal work in evaluating foreign language proficiencies across multiple cultures combined his expertise in psycholinguistics with that in psychometrics and defined fundamental issues in the study of language acquisition. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献