全文获取类型
收费全文 | 1711篇 |
免费 | 93篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 6篇 |
综合类 | 16篇 |
化学工业 | 425篇 |
金属工艺 | 18篇 |
机械仪表 | 26篇 |
建筑科学 | 133篇 |
矿业工程 | 22篇 |
能源动力 | 21篇 |
轻工业 | 330篇 |
水利工程 | 7篇 |
石油天然气 | 3篇 |
武器工业 | 1篇 |
无线电 | 66篇 |
一般工业技术 | 230篇 |
冶金工业 | 301篇 |
自动化技术 | 202篇 |
出版年
2023年 | 12篇 |
2022年 | 37篇 |
2021年 | 37篇 |
2020年 | 36篇 |
2019年 | 50篇 |
2018年 | 40篇 |
2017年 | 43篇 |
2016年 | 44篇 |
2015年 | 42篇 |
2014年 | 58篇 |
2013年 | 137篇 |
2012年 | 78篇 |
2011年 | 127篇 |
2010年 | 65篇 |
2009年 | 68篇 |
2008年 | 69篇 |
2007年 | 78篇 |
2006年 | 67篇 |
2005年 | 64篇 |
2004年 | 68篇 |
2003年 | 46篇 |
2002年 | 52篇 |
2001年 | 23篇 |
2000年 | 28篇 |
1999年 | 43篇 |
1998年 | 24篇 |
1997年 | 21篇 |
1996年 | 32篇 |
1995年 | 28篇 |
1994年 | 18篇 |
1993年 | 19篇 |
1992年 | 17篇 |
1991年 | 9篇 |
1990年 | 21篇 |
1989年 | 15篇 |
1988年 | 8篇 |
1987年 | 10篇 |
1986年 | 13篇 |
1985年 | 7篇 |
1984年 | 11篇 |
1983年 | 10篇 |
1982年 | 9篇 |
1981年 | 8篇 |
1979年 | 9篇 |
1978年 | 8篇 |
1975年 | 9篇 |
1974年 | 9篇 |
1972年 | 6篇 |
1970年 | 6篇 |
1967年 | 6篇 |
排序方式: 共有1807条查询结果,搜索用时 15 毫秒
41.
McKay James R.; Lynch Kevin G.; Shepard Donald S.; Ratichek Sara; Morrison Rebecca; Koppenhaver Janelle; Pettinati Helen M. 《Canadian Metallurgical Quarterly》2004,72(6):967
This study of continuing care for substance dependent patients compared a telephone-based monitoring and brief counseling intervention (TEL) with 2 face-to-face interventions, relapse prevention (RP) and standard 12-step group counseling (STND). The participants were graduates of intensive outpatient programs who had current dependence on alcohol and/or cocaine. Self-report, collateral, and biological measures of alcohol and cocaine use were obtained over a 12-month follow-up. The treatment groups did not differ on abstinence-related outcomes in the complete sample (N = 359) or on cocaine use outcomes in participants with cocaine dependence (n = 268). However, in participants with alcohol dependence only (n = 91), TEL produced better alcohol use outcomes than STND on all measures examined and better outcomes than RP on some of the measures. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
42.
This paper presents the application of a multi-scale paradigm to Chinese spoken document retrieval (SDR) for improving retrieval performance. Multi-scale refers to the use of both words and subwords for retrieval. Words are basic units in a language that carry lexical meaning, and subword units (such as phonemes, syllables or characters) are building components for words. Retrieval using subword indexing units is better than retrieval using words because of the robustness of subword units to out-of-vocabulary (OOV) words during speech recognition and ambiguities in word segmentation. Experimental results have demonstrated that subword bigrams can bring improvement in retrieval performance over words (~9.56%). Application of multi-scale fusion to SDR aims at combining the lexical information of words and the robustness of subwords. This work presents the first detailed investigation for a Cantonese broadcast news retrieval task using two different multi-scale fusion approaches: pre-retrieval fusion and post-retrieval fusion. Multi-scale retrieval using both words and syllable bigrams achieves improvement in retrieval performance (~1.90%) over retrieval on the composite scales. 相似文献
43.
Guo M Jiang XP Lam KH Wang S Sun CL Chan HL Zhao XZ 《The Review of scientific instruments》2007,78(1):016105
In this article, a multilayer piezoelectric transformer based on lead-free Mn-doped 0.94(Bi(12)Na(12))TiO(3)-0.06BaTiO(3) ceramics is presented. This piezoelectric transformer, with a multilayered construction in the thickness direction, is 8.3 mm long, 8.3 mm wide, and 2.3 mm thick. It operates in the second thickness extensional vibration mode. For a temperature rise of 20 degrees C, the transformer has an output power of >0.3 W. With a matching load resistance of 10 Omega, its maximum efficiency approaches 81.5%, and the maximum voltage gain is 0.14. It has potential to be used in low voltage power supply units such as low power adapter and other electronic circuits. 相似文献
44.
Helen M. Snaith Corresponding author Martin Gade Gordon W. Jolly Antoine Mangin Vittorio Barale Ove Rud 《International journal of remote sensing》2013,34(7-8):1341-1347
The Clean Seas project focused on the role that existing Earth observing satellites might play in monitoring marine pollution. Results are presented here from August 1997, for the North Sea test site, using sea surface temperature (SST), colour and synthetic aperture radar (SAR) images in conjunction with a hydrodynamic model. There was good correlation between data sources, e.g. between SST and ERS-2 SAR images. Both datasets showed the development of fine plume structures close to the Rhine outflow, apparently associated with the outflow, and possibly caused by tidal pulsing of the Rhine Plume. The model reproduced general temperature and sediment distributions well, but fine structures were not reproduced. Model sediment distribution patterns were verified using ‘chlorophyll concentration’ data from colour sensors, representative of sediment concentration in turbid water. In conjunction with the visible channels of the Advanced Very High Resolution Radiometer and Along-Track Scanning Radiometer, they give an uncalibrated measure of the sediment load. The model gives a more complete picture of the temporal dispersion of the Rhine Plume over time than is evident from the remotely sensed data alone. 相似文献
45.
Designers and manufacturers often see consumption as the primary objective of a product–with implications such as discarded products,obsolete wastes,and ecological degradation.The paper aims to find the answer to the question,how emotional design can adapt the discarded and undesirable products into something valuable in a long term?This paper presents a framework combining Chapman’s theory and Norman’s theory on three levels of emotional design to highlight what long lasting connection with products entails.A design approach is presented combing the Wabi Sabi philosophy that promotes the celebration of decay and damage.This is used as one of the design principles for the experiments conducted on discarded products.Through constant user interaction before,during and after the experiments the evaluation of design as an agent of transformation is done.The user conducted the evaluation based on the Kansei elements of looks,sound,smell,and feel of the product.The experiments confirmed that a long-term value is only achieved through redesigning and reconstructing the perception of people towards products on a reflective level,rather than the visceral and behavioural elements of the product.The research found attachment to the visceral and behavioural elements of a product instead of an emotional one was causing users to discard products faster than required.The research indicated that many people,including designers and manufacturers,are unconsciously focusing on usability(behavioural level)and physical look(visceral level)of a product that are easily replaced,than on a meaningful way (reflective level)to create and maintain long-lasting emotions.The research concluded with a proposition towards digitization of products which could perhaps be an all round solution to make products more appropriate to human emotions.Digitization could give products the ability to capture,store and then communicate the stories,journey and memories back,in order to empower people to understand the value of longer-term use of products. 相似文献
46.
Hemant J. Desai Daniel O. Acheampong Robert Hudson Richard Lacey Claire Stanley Helen Turner 《Journal of Energetic Materials》2017,35(1):109-124
The synthesis of a novel heterocyclic–telechelic polymer, α,ω-oxetanyl-telechelic poly(3-nitratomethyl-3-methyl oxetane), is described. Infrared spectroscopy (IR), gel permeation chromatography (GPC), and nuclear magnetic resonance (NMR) spectroscopy have been used to confirm the successful synthesis, demonstrating the presence of the telechelic-oxetanyl moieties. Synthesis of the terminal functionalities has been achieved via displacement of nitrato groups, in a manner similar to that employed with other leaving groups such as azido, bromo, and nitro, initiated by nucleophiles. In the present case, displacement occurs on the ends of a nitrato-functionalized polymer driven by the formation of sodium nitrate, which is supported by the polar aprotic solvent N,N-dimethyl formamide. The formation of an alkoxide at the polymer chain ends is favored and allows internal back-biting to the nearest carbon bearing the nitrato group, intrinsically in an SN2(i) reaction, leading to α,ω-oxetanyl functionalization. The telechelic-oxetanyl moieties have the potential to be cross-linked by chemical (e.g., acidic) or radiative (e.g., ultraviolet) curing methods without the use of high temperatures, usually below 100°C. This type of material was designed for future use as a contraband simulant, whereby it would form the predominant constituent of elastomeric composites comprising rubbery polymer with small quantities of solids, typically crystals of contraband substances, such as explosives or narcotics. This method also provides an alternative approach to ring closure and synthesis of heterocycles. 相似文献
47.
The electricity industry is rapidly changing: costs are increasingly dominated by capital and technology is turning loads into resources. This is similar to the early days of the Internet. Building on rate-structures used in the communications industry, utilities of the future should offer customers a portfolio of service contract options that provide a signal to the utility regarding the type and amount of infrastructure that should be deployed. 相似文献
48.
49.
Lisa J. White Giles T.S. Kirby Helen C. Cox Roozbeh Qodratnama Omar Qutachi Felicity R.A.J. Rose Kevin M. Shakesheff 《Materials science & engineering. C, Materials for biological applications》2013,33(5):2578-2583
There is a need to control the spatio-temporal release kinetics of growth factors in order to mitigate current usage of high doses. A novel delivery system, capable of providing both structural support and controlled release kinetics, has been developed from PLGA microparticles. The inclusion of a hydrophilic PLGA–PEG–PLGA triblock copolymer altered release kinetics such that they were decoupled from polymer degradation. A quasi zero order release profile over four weeks was produced using 10% w/w PLGA–PEG–PLGA with 50:50 PLGA whereas complete and sustained release was achieved over ten days using 30% w/w PLGA–PEG–PLGA with 85:15 PLGA and over four days using 30% w/w PLGA–PEG–PLGA with 50:50 PLGA. These three formulations are promising candidates for delivery of growth factors such as BMP-2, PDGF and VEGF. Release profiles were also modified by mixing microparticles of two different formulations providing another route, not previously reported, for controlling release kinetics. This system provides customisable, localised and controlled delivery with adjustable release profiles, which will improve the efficacy and safety of recombinant growth factor delivery. 相似文献
50.