全文获取类型
收费全文 | 2341篇 |
免费 | 95篇 |
国内免费 | 17篇 |
专业分类
电工技术 | 36篇 |
综合类 | 3篇 |
化学工业 | 357篇 |
金属工艺 | 44篇 |
机械仪表 | 132篇 |
建筑科学 | 106篇 |
矿业工程 | 3篇 |
能源动力 | 56篇 |
轻工业 | 200篇 |
水利工程 | 8篇 |
石油天然气 | 4篇 |
无线电 | 311篇 |
一般工业技术 | 414篇 |
冶金工业 | 445篇 |
原子能技术 | 15篇 |
自动化技术 | 319篇 |
出版年
2023年 | 27篇 |
2022年 | 38篇 |
2021年 | 72篇 |
2020年 | 31篇 |
2019年 | 48篇 |
2018年 | 56篇 |
2017年 | 49篇 |
2016年 | 78篇 |
2015年 | 50篇 |
2014年 | 73篇 |
2013年 | 179篇 |
2012年 | 95篇 |
2011年 | 119篇 |
2010年 | 87篇 |
2009年 | 105篇 |
2008年 | 95篇 |
2007年 | 80篇 |
2006年 | 91篇 |
2005年 | 93篇 |
2004年 | 72篇 |
2003年 | 46篇 |
2002年 | 49篇 |
2001年 | 46篇 |
2000年 | 36篇 |
1999年 | 40篇 |
1998年 | 161篇 |
1997年 | 98篇 |
1996年 | 80篇 |
1995年 | 42篇 |
1994年 | 36篇 |
1993年 | 48篇 |
1992年 | 18篇 |
1991年 | 19篇 |
1990年 | 16篇 |
1989年 | 20篇 |
1988年 | 15篇 |
1987年 | 11篇 |
1986年 | 20篇 |
1985年 | 14篇 |
1984年 | 9篇 |
1983年 | 9篇 |
1981年 | 5篇 |
1980年 | 8篇 |
1979年 | 7篇 |
1978年 | 8篇 |
1977年 | 6篇 |
1976年 | 10篇 |
1974年 | 5篇 |
1973年 | 8篇 |
1971年 | 5篇 |
排序方式: 共有2453条查询结果,搜索用时 15 毫秒
71.
Low T. Ming-Fu Li Samudra G. Yee-Chia Yeo Chunxiang Zhu Chin A. Dim-Lee Kwong 《Electron Devices, IEEE Transactions on》2005,52(11):2430-2439
We outlined a simple model to account for the surface roughness (SR)-induced enhanced threshold voltage (V/sub TH/) shifts that were recently observed in ultrathin-body MOSFETs fabricated on <100> Si surface. The phenomena of enhanced V/sub TH/ shifts can be modeled by accounting for the fluctuation of quantization energy in the ultrathin body (UTB) MOSFETs due to SR up to a second-order approximation. Our model is then used to examine the enhanced V/sub TH/ shift phenomena in other novel surface orientations for Si and Ge and its impact on gate workfunction design. We also performed a calculation of the SR-limited hole mobility (/spl mu//sub H,SR/) of p-MOSFETs with an ultrathin Si and Ge active layer thickness, T/sub Body/<10 nm. Calculation of the electronic band structures is done within the effective mass framework via the Luttinger Kohn Hamiltonian, and the mobility is calculated using an isotropic approximation for the relaxation time calculation, while retaining the full anisotropy of the valence subband structure. For both Si and Ge, the dependence of /spl mu//sub H,SR/ on the surface orientation, channel orientation, and T/sub Body/ are explored. It was found that a <110> surface yields the highest /spl mu//sub H,SR/. The increasing quantization mass m/sub z/ for <110> surface renders its /spl mu//sub H,SR/ less susceptible with the decrease of T/sub Body/. In contrast, <100> surface exhibits smallest /spl mu//sub H,SR/ due to its smallest m/sub z/. The SR parameters, i.e. autocorrelation length (L) and root-mean-square (/spl Delta//sub rms/) used in this paper is obtained from the available experimental result of Si<100> UTB MOSFETs, by adjusting these SR parameters to obtain a theoretical fit with experimental data on SR-limited mobility and V/sub TH/ shifts. This set of SR parameters is then employed for all orientations of both Si and Ge devices. 相似文献
72.
Xuejiao Liu Zhixin Xu Asma Iqbal Ming Chen Nazakat Ali CheeTongJohn Low Rongrong Qi Jiantao Zai Xuefeng Qian 《纳微快报(英文)》2021,(3):197-208
Huge volume changes of Si during lithiation/delithiation lead to regeneration of solid-electrolyte interphase(SEI)and consume electrolyte.In this article,γ-glycidoxypropyl trimethoxysilane(GOPS)was incorporated in Si/PEDOT:PSS electrodes to construct a flexible and conductive artificial SEI,effectively suppressing the consumption of electrolyte.The optimized electrode can maintain 1000 mAh g^−1 for nearly 800 cycles under limited electrolyte compared with 40 cycles of the electrodes without GOPS.Also,the optimized electrode exhibits excellent rate capability.The use of GOPS greatly improves the interface compatibility between Si and PEDOT:PSS.XPS Ar+etching depth analysis proved that the addition of GOPS is conducive to forming a more stable SEI.A full battery assembled with NCM 523 cathode delivers a high energy density of 520 Wh kg^−1,offering good stability. 相似文献
73.
Moumita Mukherjee Biswanath Mukherjee Youngill Choi Kyoseung Sim Junghwan Do Seungmoon Pyo 《Synthetic Metals》2010,160(5-6):504-509
We report a copper hexadecafluorophthalocyanine (F16CuPc) based n-type organic field-effect transistor (OFET) with polymeric gate dielectrics with different physical/electrical properties. The gate dielectrics are four types of cross-linked poly(4-vinylphenol) and newly prepared poly(4-phenoxy methyl styrene) and those are characterized based on surface tension, leakage current and capacitance. The performance of F16CuPc OFETs with those gate dielectrics was compared. We found that the composition of the gate dielectrics and the interfacial interaction of F16CuPc with the gate dielectric play a decisive role in the performance of OFETs. The effect of physical/electrical properties, composition and processing condition of the gate dielectrics on the device performance was investigated. 相似文献
74.
Kazushi Yamanaka Noritaka Nakaso Takeshi Fukiura Dong Youn Sim 《Electrical Engineering in Japan》2009,168(1):41-51
A thin beam of waves usually diverges due to diffraction, which is a limitation of any device using such waves. However, a surface acoustic wave (SAW) on a sphere with an appropriate aperture does not diverge but is collimated, realizing ultra‐multiple roundtrips along an equator of the sphere. This effect is caused by the balance between diffraction and focusing on a spherical surface, and it enables realization of high‐performance ball SAW sensors. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 168(1): 41–51, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20817 相似文献
75.
The rough sets analysis focusing on the ownership, locational and internalization (OLI) advantages of Chinese construction multinational corporations (MNCs) in the international market under Dunning's Eclectic Paradigm was adopted to overcome the sample size constraint in MNC research that seeks to examine the causality patterns of the factors identified. The rough sets methodology provides a solution that conventional statistical methods do not offer to ascertain how these factors are determined and their influence in the OLI analysis of the performance of Chinese construction MNCs. The rough sets approach to handling imperfect data with uncertainty and vagueness was adopted to describe dependencies between attributes, evaluate the significance of attributes and deal with inconsistencies. Based on a questionnaire survey of 31 Chinese construction MNCs, findings from the rough sets analysis suggest, among other things, that: (1) a firm is likely to perform well in terms of its ownership advantages when it has a significant advantage on its reputation and its accessibility to resources when compared with local contractors; (2) a firm may be expected to achieve better results in terms of its locational advantages if the large number of competitors from China in the host countries becomes its most important consideration; and (3) a firm that conscientiously avoids or reduces information search and business negotiation costs would tend to perform well in terms of its internalization advantages. 相似文献
76.
77.
Nicholas Low 《Urban Policy and Research》2013,31(4):205-222
This paper reviews the contribution of regulation theory to our understanding of urban development and its regulation by the state. The theory provides a useful instrument for convergence of politics, economics and geography in which the crucial questions of territoriality of local states and the embeddedness of capital can be considered. But there remains much to be explored both in the mode of development of the global economy over time, and in the relationship between global economic structures and local political institutions. The further development of regulation theory demands a reconceptualisation of power and the absorption of ecological/environmental and feminist discourses into the debates. 相似文献
78.
Simões S. Ramos A. S. Viana F. Emadinia O. Vieira M. T. Vieira M. F. 《Journal of Materials Engineering and Performance》2016,25(10):4394-4401
Journal of Materials Engineering and Performance - Ni/Al multilayers are known to transform into NiAl in a highly exothermic and self-sustaining reaction. The fact that this reaction has a high... 相似文献
79.
Myeong Seong Sim Hye Jeong Kim Sang Hee Jo Chun Kim Il Yup Chung 《International journal of molecular sciences》2022,23(7)
Lysophosphatidylserine (LysoPS) is an amphipathic lysophospholipid that mediates a broad spectrum of inflammatory responses through a poorly characterized mechanism. Because LysoPS levels can rise in a variety of pathological conditions, we sought to investigate LysoPS’s potential role in airway epithelial cells that actively participate in lung homeostasis. Here, we report a previously unappreciated function of LysoPS in production of a mucin component, MUC5AC, in the airway epithelial cells. LysoPS stimulated lung epithelial cells to produce MUC5AC via signaling pathways involving TACE, EGFR, and ERK. Specifically, LysoPS- dependent biphasic activation of ERK resulted in TGF-α secretion and strong EGFR phosphorylation leading to MUC5AC production. Collectively, LysoPS induces the expression of MUC5AC via a feedback loop composed of proligand synthesis and its proteolysis by TACE and following autocrine EGFR activation. To our surprise, we were not able to find a role of GPCRs and TLR2, known LyoPS receptors in LysoPS-induced MUC5AC production in airway epithelial cells, suggesting a potential receptor-independent action of LysoPS during inflammation. This study provides new insight into the potential function and mechanism of LysoPS as an emerging lipid mediator in airway inflammation. 相似文献
80.
Sang-Kyu Shin Jeong-Eun Sim Hideki Kishimura Byung-Soo Chun 《Journal of Industrial and Engineering Chemistry》2012,18(1):546-550
Ethanolysis of menhaden oil was performed with 1,3-regiospecific lipase to produce diglycerides and monoglycerides containing polyunsaturated fatty acids, and fatty acid ethyl esters. Immobilized lipases like lipozyme TL-IM (Thermomuces lanuginosa immobilized on silica gel) were used for enzymatic ethanolysis. Ethanolysis was carried out in different processes (solvent free, organic solvent and supercritical fluid system) to compare the reaction rate and yield obtained by menhaden oil ethanolysis. Organic solvent (hexane) and supercritical carbon dioxide (SC-CO2) were used as reaction medium. The reaction products were analyzed by gas chromatography (GC), thin layer chromatography (TLC) and high performance liquid chromatography (HPLC). Higher amounts of ethanol as a substrate caused substrate inhibition which dramatically decreased the reaction rate of ethanolysis. To elucidate the effect of pressure, enzymatic ethanolysis was performed in SC-CO2 at pressures ranging from 75 to 121 bar. Enzymatic ethanolysis of menhaden oil in SC-CO2 decreased by substrate inhibition. Reaction rate and optimum amount of ethanol used were depended on SC-CO2 density individually. Kinetic model with substrate inhibition (dead-end inhibition) by excess ethanol was set up to measure the reaction and inhibition rates. 相似文献