全文获取类型
收费全文 | 1287篇 |
免费 | 48篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 28篇 |
综合类 | 3篇 |
化学工业 | 346篇 |
金属工艺 | 12篇 |
机械仪表 | 18篇 |
建筑科学 | 58篇 |
矿业工程 | 1篇 |
能源动力 | 42篇 |
轻工业 | 154篇 |
水利工程 | 13篇 |
石油天然气 | 1篇 |
无线电 | 96篇 |
一般工业技术 | 137篇 |
冶金工业 | 215篇 |
原子能技术 | 10篇 |
自动化技术 | 202篇 |
出版年
2023年 | 5篇 |
2022年 | 18篇 |
2021年 | 15篇 |
2020年 | 17篇 |
2019年 | 14篇 |
2018年 | 21篇 |
2017年 | 16篇 |
2016年 | 21篇 |
2015年 | 19篇 |
2014年 | 41篇 |
2013年 | 58篇 |
2012年 | 50篇 |
2011年 | 65篇 |
2010年 | 54篇 |
2009年 | 71篇 |
2008年 | 66篇 |
2007年 | 69篇 |
2006年 | 45篇 |
2005年 | 51篇 |
2004年 | 40篇 |
2003年 | 43篇 |
2002年 | 38篇 |
2001年 | 28篇 |
2000年 | 28篇 |
1999年 | 31篇 |
1998年 | 43篇 |
1997年 | 34篇 |
1996年 | 35篇 |
1995年 | 32篇 |
1994年 | 17篇 |
1993年 | 23篇 |
1992年 | 18篇 |
1991年 | 13篇 |
1990年 | 13篇 |
1989年 | 15篇 |
1988年 | 14篇 |
1987年 | 10篇 |
1986年 | 19篇 |
1985年 | 10篇 |
1984年 | 14篇 |
1983年 | 10篇 |
1982年 | 7篇 |
1981年 | 11篇 |
1979年 | 10篇 |
1978年 | 8篇 |
1977年 | 5篇 |
1975年 | 6篇 |
1973年 | 5篇 |
1971年 | 4篇 |
1961年 | 4篇 |
排序方式: 共有1336条查询结果,搜索用时 15 毫秒
71.
Band-gap tuning of pendant polymers for organic light-emitting devices and photovoltaic applications
Akhil Gupta Scott E. Watkins Andrew D. Scully Th. Birendra Singh Gerard J. Wilson Lynn J. Rozanski Richard A. Evans 《Synthetic Metals》2011,161(9-10):856-863
The preparation of a series of novel polymers comprising pendant electro-active “push–pull” chromophores and their performance in solution-processed organic electronic devices is described. The design of the electro-active pendant chromophores was based on the well-known motif of cyano-substituted poly(p-phenylenevinylene). Optical band-gap engineering within this series of polymers was achieved by varying the conjugation length and the electron donor/acceptor functionalities of the pendant chromophores. The introduction of a cyanoimine group into the electro-active pendant module resulted in a marked narrowing of the optical band-gap compared with the other electro-active pendant chromophores investigated in this work. Bulk heterojunction solar cell devices comprising these polymers were prepared by solution processing blends of each polymer with [6,6]-phenyl-C61-butyric acid methyl ester, and their performance was evaluated by measuring power conversion efficiencies. The best-performing solar cell in this series exhibited a power conversion efficiency of 0.29% and a maximum incident photon-to-current conversion efficiency of 22% and was produced using the polymer in which the electro-active chromophore comprised the cyanoimine group. 相似文献
72.
Gerard Cummins Ian Underwood Anthony Walton 《Journal of the Society for Information Display》2011,19(4):360-367
Abstract— Positively doped, intrinsic, negatively doped organic light‐emitting diodes (PIN‐OLEDs) have been shown to exhibit high efficiency and a long lifetime compared to conventional small‐molecule OLEDs (SM‐OLEDs). The improved performance of PIN‐OLEDs makes them attractive for use in display applications. Knowledge of the electrical load exhibited by these devices is used to develop an equivalent electrical‐circuit model. Such models are used by circuit designers to assist with the precise design of active‐matrix‐display driver circuits used in such applications. In this paper, the development of a SPICE model for a top‐emitting PIN‐OLED stack is reported. 相似文献
73.
Marta Lubary Theo W. de LoosJoop H. ter Horst Gerard W. Hofland 《The Journal of Supercritical Fluids》2011,55(3):1079-1088
The ScMM (Supercritical Melt Micronization) process was applied for the production of microparticles from anhydrous milk fat (AMF) and a diacylglycerol-based modified milk fat (D-AMF). Both fats were able to dissolve ca. 30 wt% CO2 in the studied pressure and temperature ranges, being the CO2 amount slightly higher for AMF. A melting point depression was observed in both systems in the presence of CO2. Two powder morphologies were obtained (spherical hollow particles and a mass sponge-like broken particles) depending on the ScMM process conditions. The concentration of CO2 in the fat melt was the main process variable affecting the particle morphology, followed by the temperature of the melt. The small broken particles originated from the breakage of spherical fat particles that solidified before all CO2 could escape from the atomized droplets. While the hollow spheres had a tendency to agglomerate, the broken microparticles constituted a free-flowing powder as long as they were stored at low temperatures (up to −18 °C). Both types of particles have a potential for being incorporated in refrigerated or frozen food products as a structuring agent. 相似文献
74.
Benedicta Ronchi Wim Clymans Ana Lúcia Pena Barão Floor Vandevenne Eric Struyf Okke Batelaan Alain Dassargues Gerard Govers 《SILICON》2013,5(1):115-133
This paper reviews the processes which determine the concentrations of dissolved silicon (DSi) in soil water and proposes a conceptual mechanistic model for understanding the transport of Si through soils to rivers. The net DSi present in natural waters originates from the dissolution of mineral and amorphous Si sources in the soil, as well as precipitation processes. Important controlling factors are soil composition (mineralogy and saturated porosity) and soil water chemistry (pH, concentrations of organic acids, CO2 and electrolytes). Together with production, polymerization and adsorption equations they constitute a mechanistic framework determining DSi concentrations. We discuss how key controls differ across soil horizons and how this can influence the DSi transport. A typical podzol soil profile in a temperate climate is used as an example, but the proposed model is transferrable to other soil types. Additionally, the impact of external forcing factors such as seasonal climatic variations and land use is evaluated. This blueprint for an integrated model is a first step to mechanistic modelling of Si transport processes in soils. Future implementation with numerical methods should validate the model with field measurements. 相似文献
75.
Ove Wolfgang Arne Haugstad Birger Mo Anders Gjelsvik Ivar Wangensteen Gerard Doorman 《Energy》2009,34(10):1642
The Norwegian Energy Act that came into force in 1991 deregulated the electricity market and removed the former obligation power companies had to supply electricity to the geographical area they were responsible for. Hence producers can supply electricity on the basis of profitability. In 2007 the Energy Act was evaluated by the Government. As a part of this, a study concerning hydro reservoir handling before and after deregulation was carried out by SINTEF. Public statistics show that average hydro reservoir levels measured in per cent of reservoir capacity have been reduced after 1990. We have used the power-market model EMPS1 (EFI's Multi-area Power-market Simulator) to analyze if this reduction can be explained by natural variation in climatic variables or by structural changes that have occurred after 1990. Simulation results show that the reduced reservoir levels cannot be explained by natural variation in climatic variables. Structural changes such as increased transmission capacities can, however, explain some of the reduction. Our study does not indicate that the present reservoir handling gives reservoir levels that are too low. In this paper we also describe the stochastic dynamic optimization problem for long-term hydropower scheduling, and we explain how this problem actually is solved by the EMPS model. 相似文献
76.
Touchard Gerard Benyamina M. Borzeix J.A.G. Romat H. 《Industry Applications, IEEE Transactions on》1989,25(6):1067-1072
The mechanism of static electrification of hydrocarbon liquids flowing through artificially roughed metallic pipes is analyzed. Only the case of a laminar flow is considered. The equations of motion of the liquid are computed in the case of circular pipes with periodic roughness of rectangular cross section in the axial direction. The results reveal the formation of eddies, which depend on the size and the period of the roughness and on the Reynolds number. After determining the charge convected in a smooth pipe and the velocity profile in a rough one, it is possible to predict the convected space charge in terms of the roughness characteristics. The experimental results obtained with different rough pipes and several Reynolds numbers are in good agreement with the predictions, making it possible to explain the observations made during previous experiments on static electrification in rough pipes 相似文献
77.
Gerard J. Puccio Roger L. Firestien Christina Coyle Cristina Masucci 《Creativity & Innovation Management》2006,15(1):19-33
A major focus within the field of creativity has been on the development of methodologies aimed at deliberately nurturing creative thinking. These methodologies have attempted to mirror the creative process in ways that allow individuals and groups to explicitly call on and employ their creative faculties. In an attempt to uplift employees’ creative capabilities many of these methodologies have been introduced into organizations through training programs, as well as through application to business challenges. Do these methods work? What is the empirical evidence that these deliberate creative process methods enhance employees’ creativity? Though there are a handful of creative process methods, few have married the concern for application with an interest in demonstrating the benefits of these applied efforts through systematic research. Creative Problem Solving (CPS), one of the more popular creative process models, has been one of the rare exceptions. The purpose of this paper is to synthesize the research literature that reports on the impact of CPS training carried out within organizational contexts, that is training programs that involved professionals or students working on real business challenges. Additionally, the positive benefits of CPS are further examined through reports that cite the outcomes of applying CPS to business challenges. In a field replete with methods that have been commercialized, it is imperative to strike a balance between research and practice as an imbalance towards practice may foster a field dominated by individuals who offer untested products and services. 相似文献
78.
We studied the late-stage spinodal decomposition of the polystyrene–cyclohexanol system in relation to membrane formation. Phase separation was effected by the removal of thermal energy from the homogeneous polymer solution. The ultimate morphology of the phase-separated systems has been studied using electron microscopy and has been found to be strongly affected by the quenching time. A shift from a highly interconnected open-cell structure to a closed-cell structure has been observed, indicating the transition of the spinodal decomposition from early to late stages. The cell growth in the late stage has been quantitatively analyzed and a power-law relationship between the cell size and quenching time has been found. The resulting exponent of 0.61 is consistent with literature values from light-scattering measurements, as well as from theoretical derivations. © 1995 John Wiley & Sons, Inc. 相似文献
79.
GB Karlsson M Halloran D Schenten J Lee P Racz K Tenner-Racz J Manola R Gelman B Etemad-Moghadam E Desjardins R Wyatt NP Gerard L Marcon D Margolin J Fanton MK Axthelm NL Letvin J Sodroski 《Canadian Metallurgical Quarterly》1998,188(6):1159-1171
CD4+ T lymphocyte depletion in human immunodeficiency virus type 1 (HIV-1)-infected humans underlies the development of acquired immune deficiency syndrome. Using a model in which rhesus macaques were infected with chimeric simian-human immunodeficiency viruses (SHIVs), we show that both the level of viremia and the structure of the HIV-1 envelope glycoprotein ectodomains individually contributed to the efficiency with which CD4(+) T lymphocytes were depleted. The envelope glycoproteins of recombinant SHIVs that efficiently caused loss of CD4(+) T lymphocytes exhibited increased chemokine receptor binding and membrane-fusing capacity compared with those of less pathogenic viruses. These studies identify the HIV-1 envelope glycoprotein ectodomains as determinants of CD4(+) T lymphocyte loss in vivo and provide a foundation for studying pathogenic mechanisms. 相似文献
80.
J. Gerard Wolff 《New Generation Computing》1995,13(2):187-214
This article is an overview of a programme of research based on the conjecture thatall kinds of computing and formal reasoning may usefully be understood as information compression by pattern matching, unification and metrics-guided search. The research aims to develop this idea into a theory of computing to integrate and simplify diverse concepts in the field. The research also aims to develop a ‘new generation’ computing system, based on the theory, to integrate and simplify diverse kinds of computing and to achieve more flexibility and ‘intelligence’ than conventional computers. Software simulations of the proposed new system provide a concrete expression of the developing theory and a test-bed for the ideas. The background to the research is briefly reviewed including evidence that information compression is a significant element in biological information processing systems. Concepts ofinformation andredundancy are described as a basis for describing how information compression may be achieved by the comparison ormatching of patterns, the merging orunification of patterns which are the same, together withmetrics-guided search (e.g., ‘hill climbing’, ‘beam search’) to maximise compression for a given computational effort. The main elements of the SP theory and of the proposed SP system are described with a summary of developments to date. Some of the kinds of computing which be interpreted as information compression are briefly reviewed. These include: the ‘low level’ workings of conventional computers; information retrieval, pattern recognition and de-referencing of identifiers; unsupervised inductive learning (grammatical inference, data mining, automatic organisation of software and of knowledge bases); the execution of mathematical or computing functions; deductive and probabilistic inference; parsing and natural language processing; planning and problem solving. Areas of uncertainty where further work is needed are indicated at appropriate points throughout the article. 相似文献