全文获取类型
收费全文 | 3089篇 |
免费 | 225篇 |
国内免费 | 20篇 |
专业分类
电工技术 | 43篇 |
综合类 | 8篇 |
化学工业 | 639篇 |
金属工艺 | 48篇 |
机械仪表 | 98篇 |
建筑科学 | 102篇 |
能源动力 | 142篇 |
轻工业 | 216篇 |
水利工程 | 15篇 |
石油天然气 | 7篇 |
无线电 | 588篇 |
一般工业技术 | 625篇 |
冶金工业 | 189篇 |
原子能技术 | 9篇 |
自动化技术 | 605篇 |
出版年
2023年 | 19篇 |
2022年 | 57篇 |
2021年 | 94篇 |
2020年 | 58篇 |
2019年 | 74篇 |
2018年 | 91篇 |
2017年 | 86篇 |
2016年 | 102篇 |
2015年 | 94篇 |
2014年 | 145篇 |
2013年 | 289篇 |
2012年 | 208篇 |
2011年 | 196篇 |
2010年 | 187篇 |
2009年 | 186篇 |
2008年 | 176篇 |
2007年 | 156篇 |
2006年 | 123篇 |
2005年 | 95篇 |
2004年 | 79篇 |
2003年 | 83篇 |
2002年 | 78篇 |
2001年 | 60篇 |
2000年 | 56篇 |
1999年 | 64篇 |
1998年 | 92篇 |
1997年 | 59篇 |
1996年 | 41篇 |
1995年 | 40篇 |
1994年 | 34篇 |
1993年 | 30篇 |
1992年 | 23篇 |
1991年 | 17篇 |
1990年 | 15篇 |
1989年 | 18篇 |
1988年 | 8篇 |
1987年 | 9篇 |
1986年 | 7篇 |
1985年 | 6篇 |
1984年 | 11篇 |
1983年 | 14篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1974年 | 5篇 |
1971年 | 3篇 |
1970年 | 8篇 |
排序方式: 共有3334条查询结果,搜索用时 15 毫秒
41.
Abstract— Owing to the fast developments of computer networks and color imaging technologies, there is a tendency towards remote proofing in the printing or textile industries. More cases such as cross‐display color matching will occur in the future information society. The problems of color mismatching we usually find in cross‐display devices have been widely discussed today. In this paper, to achieve equivalent color matching between a sRGB monitor and an Adobe RGB monitor, the spatial gamut mapping algorithm (SGMA), which introduces sigmoidal tone mapping, multi‐mapping paths, and unsharp mask (USM) operation into a sRGB color‐management system, is proposed. According to the designs of USM locations, this proposed SGMA can be further developed into pre‐USM, post‐USM, and double‐USM types. Besides, two critical image characteristics, edge map and color histogram, are investigated to establish the relationship between image content and SGMA. The psychophysical experimental results show that double‐USM SGMA obtains better color matching than the other spatial types. 相似文献
42.
Why would people use Short Message Service (SMS) to say something they would not say in person? There is a trend that SMS is becoming more and more popular because it facilitates more extended modes of communications. Using technology acceptance model, we hypothesize the attitude of SMS would be influenced by its perceived effectiveness for communications, perceived ease of use, and subjective norm. Besides the special aspects of communications, conflict avoidance and privacy protection will enforce the impact of perceived effectiveness of SMS for communication. We investigated 953 SMS users and the results support most of our hypotheses. Furthermore, our analyses also show there are differences between females and males on the influence mechanism behind their attitude towards SMS. 相似文献
43.
Tran Quang Hung Sunjong Oh Jong-Ryul Jeong CheolGi Kim 《Sensors and actuators. A, Physical》2010,157(1):42-46
The planar Hall effect (PHE) sensor with a junction size of 3 μm × 3 μm for a single micro-bead detection has been fabricated successfully using a typical spin-valve thin film Ta(5)/NiFe(16)/Cu(1.2)/NiFe(2)/IrMn(15)/Ta(5) nm. The PHE sensor exhibits a sensitivity of about 7.2 μV Oe?1 in the magnetic field range of ±7 Oe approximately. We have performed an experiment to illustrated the possibility of single micro-bead detection by using a PHE sensor. A single micro-bead of 2.8 μm diameter size is secluded from 0.1% dilute solution of the Dynabeads® M-280 dropped on the sensor surface and is located on the sensor junction by using a micro magnetic needle. The comparison of the PHE voltage profiles in the field range from 0 to 20 Oe in the absence and presence of a single micro-bead identifies a single Dynabeads® M-280, the maximal signal change as large as ΔV ~ 1.1 μV can be obtained at the field ~6.6 Oe. The results are well described in terms of the reversal of a basic single domain structure. 相似文献
44.
In this paper, a new digital redesign composed of pulse width modulator (PWM) is proposed. The proposed PWM combines fuzzy logic with genetic algorithm (GA) to tune the parameter of the proposed controller such that the output response of hybrid system closely matches the one of original continuous system. Finally, an illustrated example is proposed to show the proposed method is superior to the existing one. 相似文献
45.
This paper deals with direction-of-arrival (DOA) estimation based on iterative searching technique for code-division multiple
access signals. It has been shown that the iterative searching technique is more likely to converge to a local maximum, causing
errors in DOA estimation. In conjunction with a genetic algorithm for selecting initial search angle, we present an efficient
approach to achieve the advantages of iterative DOA estimation with fast convergence and more accuracy estimate over existing
conventional spectral searching methods. Finally, several computer simulation examples are provided for illustration and comparison. 相似文献
46.
In this paper, we have demonstrated a successful electroplating process of nickel (Ni) in a sulfamate electrolyte bath at ultra low electrolytic temperatures of 273–278 K. The potentiostatic mode is essential for the electroplating process rather than galvanostatic mode. The reason is that diffusion-limited current can be easily obtained by applying a specific potential which is higher than reduction potential. On the contrary, galvanostatic mode can not identify the diffusion-limited current and the reduction will suspend while the setting current is higher than diffusion-limited current ranged in hundreds of μA. The microstructure, morphology and hardness of the Ni electrodeposits were characterized using grazing incidence x-ray diffractometer, atomic force microscopy and nano-indentation test were performed. The hardness of Ni film was much enhanced to around 6.37 GPa at 273 K to 6.18 GPa at 278 K compared with that around 4.11 GPa at 288 K to 4.01 GPa at 293 K. The normal hardness of pure nickel is about 4 GPa. The enhanced hardness of Ni at ultra low temperature is attributed to both mechanisms of reduced grain size strengthening and residual compressive stress hardening. 相似文献
47.
In this paper, we present an analytical model to evaluate the hidden station effect on the performance of the IEEE 802.11 Distributed Coordination Function (DCF) in both non-saturation and saturation condition. DCF is a random channel-access scheme based on Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) method and the exponential backoff procedure. DCF is widely used and can support both wireless network with an access point and ad hoc wireless network because of its random channel-access method. On the other hand, this method unavoidably suffers the hidden station effect that causes significant performance degradation. As shown in this paper, hidden stations occur frequently in real-world settings, and the performance impact on the 802.11 DCF is a significant concern, but it has not been adequately studied. We study this problem through a spatial–temporal analysis and a Markov chain model. Our model generalizes the existing work on the performance modeling of 802.11 DCF for both non-saturation and saturation conditions. The scenario of no hidden station can be considered as a special case in our model. The performance of our model is evaluated by comparison with ns-2 simulations. 相似文献
48.
Hung Son Nguyen 《Theoretical computer science》2011,412(42):5816-5819
49.
Shih-Jieh Hung 《Expert systems with applications》2011,38(8):9053-9062
Supply chain management allows modern enterprises to relax their own capacities and produce in a more flexible manner for diversified consumer demands. However, for an enterprise with divergent supply chain (DSC) and multiple product lines, to plan the production allocation for higher competitive advantage in the risky global market is a challenging problem. The existing literature still has not address this problem very well. This paper is aimed to treat this problem by using an integrated approach of activity based costing (ABC) and management, five forces analysis, risk and value-at-risk analysis, decision making trial and evaluation laboratory (DEMATEL), analytic network process (ANP), and fuzzy goal programming (FGP). The proposed model can effectively incorporate the key factors of precise costing, managerial constraints, competitive advantage analysis, and risk management into DSC forecasting and multi-objective production planning. A case study of a consumer-oriented cell phone DSC is also presented. The sensitivity analysis shows that identifying and relaxing crucial constraints can play an important role in DSC planning for higher competitive advantage and lower risk. 相似文献
50.
The fuzzy weighted average (FWA), which is a function of fuzzy numbers and is useful as an aggregation method in engineering or management science based on fuzzy sets theory. It provides a discrete approximate solution by α-cuts level representation of fuzzy sets and interval analysis. Since the FWA method has an exponential complexity, thus several researches have focused on reducing this complexity. This paper also presents an enhanced fuzzy weighted average approach to achieve the objective of reducing the complexity. This proposed approach is through an improved initial solution for original FWA algorithm, and a two-phase concept by extending and applying both the algorithms of Chang et al. [4] and Guu [14]. Although the complexity of the proposed FWA algorithm is O(n) the same as Guu [14] which is the best level achieved to date. But from the experimental results appear that the proposed algorithm is more efficient, which only needs a few evaluated numbers and spend much less overall CPU time than Guu [14] and other FWA algorithms. In order to demonstrate the usefulness of this study, a practical example for unmanned aerial vehicle (UAV) selecting under military requirement has illustrated. Additionally, a computer-based interface, which helps the decision maker make decisions more efficiently, has been developed. 相似文献