全文获取类型
收费全文 | 4938篇 |
免费 | 241篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 56篇 |
综合类 | 9篇 |
化学工业 | 1249篇 |
金属工艺 | 85篇 |
机械仪表 | 81篇 |
建筑科学 | 242篇 |
矿业工程 | 8篇 |
能源动力 | 171篇 |
轻工业 | 374篇 |
水利工程 | 28篇 |
石油天然气 | 9篇 |
无线电 | 518篇 |
一般工业技术 | 970篇 |
冶金工业 | 353篇 |
原子能技术 | 26篇 |
自动化技术 | 1004篇 |
出版年
2023年 | 70篇 |
2022年 | 92篇 |
2021年 | 169篇 |
2020年 | 116篇 |
2019年 | 110篇 |
2018年 | 129篇 |
2017年 | 118篇 |
2016年 | 175篇 |
2015年 | 130篇 |
2014年 | 222篇 |
2013年 | 314篇 |
2012年 | 338篇 |
2011年 | 411篇 |
2010年 | 286篇 |
2009年 | 262篇 |
2008年 | 274篇 |
2007年 | 271篇 |
2006年 | 219篇 |
2005年 | 190篇 |
2004年 | 149篇 |
2003年 | 104篇 |
2002年 | 108篇 |
2001年 | 78篇 |
2000年 | 80篇 |
1999年 | 77篇 |
1998年 | 110篇 |
1997年 | 82篇 |
1996年 | 65篇 |
1995年 | 50篇 |
1994年 | 51篇 |
1993年 | 37篇 |
1992年 | 33篇 |
1991年 | 27篇 |
1990年 | 23篇 |
1989年 | 19篇 |
1988年 | 11篇 |
1987年 | 18篇 |
1986年 | 13篇 |
1985年 | 13篇 |
1984年 | 11篇 |
1983年 | 17篇 |
1982年 | 15篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 10篇 |
1978年 | 13篇 |
1977年 | 9篇 |
1976年 | 12篇 |
1975年 | 5篇 |
1973年 | 5篇 |
排序方式: 共有5183条查询结果,搜索用时 0 毫秒
991.
992.
993.
Based on different current long-term energy scenarios the paper discusses the future perspectives of hydrogen in the German energy system as a representative example for the development of sustainable energy systems. The scenario analysis offers varying outlines of the future energy system that determine the possible role of hydrogen. The paper discusses the possibilities of expanding the share of renewable energy and the resulting prospects for establishing clean hydrogen production from renewable energy sources. Emphasis is given to the questions of an ecologically efficient allocation of limited renewable energy resources that can only be assessed from a systems analysis perspective. Findings from recent studies for Germany reveal a strong competition between the direct input into the electricity system and an indirect use as fuel in the transport sector. Moreover, the analysis underlines the paramount importance of reducing energy demand as the inevitable prerequisite for any renewable energy system. 相似文献
994.
The introduction of of web services has led to web service composition being a focus of many researchers. Composing web services using workflows is seen as the most realistic method from an industrial viewpoint. Amongst other method, the use of natural computing methods has been proposed previously to automate web service composition. The need for a fast response when computing the most suitable sequence of services is addressed in this paper. In particular, we propose a novel heuristic immune algorithm with an efficient encoding and mutation method. The algorithm involves two steps: an immune selection operation, which is maintaining antibody population diversity and the clonal selection. The use of a vaccine during the evolution provides heuristic information that accelerates the convergence. Our experimental results illustrate that the proposed heuristic immune algorithm is very effective in improving the convergence speed. We also provide a schema analysis for this method. 相似文献
995.
Olivier S.N. Smith C.J.M. Benisty H. Weisbuch C. Krauss T.F. Houdre R. Oesterle U. 《Quantum Electronics, IEEE Journal of》2002,38(7):816-824
We report on the investigation of cavities coupled to channel waveguides defined in a triangular-lattice photonic crystal etched into a GaAs/AlGaAs heterostructure waveguide. We make use of the internal probe technique by selectively exciting the photoluminescence of InAs dots embedded in the planar waveguide. We collect at the nearby cleaved edge the fundamental mode transmitted through the channel waveguides. From the study of a number of basic cases, we exemplify how one may deduce the main guideline design rules for given cavity-guide interaction mechanisms and then for the implementations of functions such as bending and filtering. In particular, the role of the so-called ministopband (MSB) feature of the waveguide and the nature of the cavity modes involved are outlined 相似文献
996.
Yi Ke Stephan Lany Joseph J. Berry John D. Perkins Philip A. Parilla Andriy Zakutayev Tim Ohno Ryan O'Hayre David S. Ginley 《Advanced functional materials》2014,24(19):2875-2882
The increase of the band gap in Zn1‐xMgxO alloys with added Mg facilitates tunable control of the conduction band alignment and the Fermi‐level position in oxide‐heterostructures. However, the maximal conductivity achievable by doping decreases considerably at higher Mg compositions, which limits practical application as a wide‐gap transparent conductive oxide. In this work, first‐principles calculations and material synthesis and characterization are combined to show that the leading cause of the conductivity decrease is the increased formation of acceptor‐like compensating intrinsic defects, such as zinc vacancies (VZn), which reduce the free electron concentration and decrease the mobility through ionized impurity scattering. Following the expectation that non‐equilibrium deposition techniques should create a more random distribution of oppositely charged dopants and defects compared to the thermodynamic limit, the paring between dopant GaZn and intrinsic defects VZn is studied as a means to reduce the ionized impurity scattering. Indeed, the post‐deposition annealing of Ga‐doped Zn0.7Mg0.3O films grown by pulsed laser deposition increases the mobility by 50% resulting in a conductivity as high as σ = 475 S cm‐1. 相似文献
997.
Daniela Drescher Ingrid Zeise Heike Traub Peter Guttmann Stephan Seifert Tina Büchner Norbert Jakubowski Gerd Schneider Janina Kneipp 《Advanced functional materials》2014,24(24):3765-3775
By adding a gold core to silica nanoparticles (BrightSilica), silica‐like nanoparticles are generated that, unlike unmodified silica nanoparticles, provide three types of complementary information to investigate the silica nano‐biointeraction inside eukaryotic cells in situ. Firstly, organic molecules in proximity of and penetrating into the silica shell in live cells are monitored by surface‐enhanced Raman scattering (SERS). The SERS data show interaction of the hybrid silica particles with tyrosine, cysteine and phenylalanine side chains of adsorbed proteins. Composition of the biomolecular corona of BrightSilica nanoparticles differs in fibroblast and macrophage cells. Secondly, quantification of the BrightSilica nanoparticles using laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS) micromapping indicates a different interaction of silica nanoparticles compared to gold nanoparticles under the same experimental conditions. Thirdly, the metal cores allow the investigation of particle distribution and interaction in the cellular ultrastructure by cryo nanoscale X‐ray tomography (cryo‐XT). In 3D reconstructions the assumption is confirmed that BrightSilica nanoparticles enter cells by an endocytotic mechanism. The high SERS intensities are explained by the beneficial plasmonic properties due to agglomeration of BrightSilica. The results have implications for the development of multi‐modal qualitative and quantitative characterization in comparative nanotoxicology and bionanotechnology. 相似文献
998.
Robust Fabrication of Nonstick,Noncorrosive, Conductive Graphene‐Coated Liquid Metal Droplets for Droplet‐Based,Floating Electrodes 下载免费PDF全文
Yuzhen Chen Tingjiao Zhou Yaoyao Li Lifei Zhu Stephan Handschuh‐Wang Deyong Zhu Xiaohu Zhou Zhou Liu Tiansheng Gan Xuechang Zhou 《Advanced functional materials》2018,28(8)
Nontoxic liquid metals (conductive materials in a liquid state at room temperature) are an emerging class of materials for applications ranging from soft electronics and robotics to medical therapy and energy devices. Their sticky and corrosive properties, however, are becoming more of a critical concern for circuits and devices containing other metals as these are easily destroyed or contaminated by the liquid metals. Herein, a feasible method for fabricating highly conductive graphene‐coated liquid metal (GLM) droplets is reported and their application as nonstick, noncorrosive, movable, soft contacts for electrical circuits is demonstrated. The as‐prepared GLM droplets consist of a liquid‐phase soft core of liquid metal and a slippery outer layer of graphene sheets. These structures address the issue of simultaneous control of the wettability and conductivity of a soft electronic contact by combining extraordinary properties, i.e., nonstick, noncorrosive, yet exhibiting high electronic conductivity while in contact with metal substrates, e.g., Au, Cu, Ag, and Ni. As proof‐of‐concept, the as‐prepared GLM droplets are demonstrated as floating electrodes for movable, recyclable electronic soft contacts in electrical circuits. 相似文献
999.
Sekihara K Owen JP Trisno S Nagarajan SS 《IEEE transactions on bio-medical engineering》2011,58(11):3121-3129
Source-space coherence analysis has become a popular method to estimate functional connectivity based on MEG/EEG. Source-space analysis involves solving the inverse problem, estimating the time courses of specific brain regions, and then examining the coherence between activities at different brain regions. However, source-space coherence analysis can be confounded by spurious coherence caused due to the leakage properties of the inverse algorithm employed. Such spurious coherence is typically manifested as an artifactual large peak around the seed voxel, called seed blur, in the resulting coherence images. This seed blur often obscures important details of brain interactions. This paper proposes the use of the imaginary part of the coherence to remove the spurious coherence caused by the leakage of an imaging algorithm. We present a theoretical analysis that explains how the use of imaginary part can remove this spurious coherence. We then present results from both computer simulations and experiments using resting-state MEG data which demonstrate the validity of our analysis. 相似文献
1000.