全文获取类型
收费全文 | 2502篇 |
免费 | 184篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 23篇 |
综合类 | 2篇 |
化学工业 | 625篇 |
金属工艺 | 124篇 |
机械仪表 | 162篇 |
建筑科学 | 41篇 |
能源动力 | 143篇 |
轻工业 | 208篇 |
水利工程 | 21篇 |
石油天然气 | 6篇 |
武器工业 | 2篇 |
无线电 | 390篇 |
一般工业技术 | 500篇 |
冶金工业 | 112篇 |
原子能技术 | 54篇 |
自动化技术 | 279篇 |
出版年
2024年 | 3篇 |
2023年 | 33篇 |
2022年 | 63篇 |
2021年 | 97篇 |
2020年 | 61篇 |
2019年 | 62篇 |
2018年 | 86篇 |
2017年 | 81篇 |
2016年 | 85篇 |
2015年 | 80篇 |
2014年 | 121篇 |
2013年 | 167篇 |
2012年 | 222篇 |
2011年 | 255篇 |
2010年 | 160篇 |
2009年 | 185篇 |
2008年 | 131篇 |
2007年 | 91篇 |
2006年 | 99篇 |
2005年 | 89篇 |
2004年 | 72篇 |
2003年 | 60篇 |
2002年 | 55篇 |
2001年 | 58篇 |
2000年 | 55篇 |
1999年 | 44篇 |
1998年 | 68篇 |
1997年 | 26篇 |
1996年 | 17篇 |
1995年 | 12篇 |
1994年 | 15篇 |
1993年 | 11篇 |
1992年 | 3篇 |
1991年 | 6篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1978年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有2692条查询结果,搜索用时 31 毫秒
111.
A power‐efficient 600‐mVpp voltage‐mode driver with independently matched pull‐up and pull‐down impedances
下载免费PDF全文
![点击此处可从《International Journal of Circuit Theory and Applications》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Woorham Bae Deog‐Kyoon Jeong 《International Journal of Circuit Theory and Applications》2015,43(12):2057-2071
In this study, a large‐swing, low‐power voltage‐mode driver with independently matched pull‐up and pull‐down impedances is proposed. To achieve large swing and constant impedances during a transition, a P‐over‐N structure is implemented with regulators calibrating the impedances. Two regulators are dedicated to matching the pull‐up and pull‐down impedances by regulating the supply voltages of the driver and predriver, respectively. Because background impedance calibration loops are adopted to track the process, voltage, and temperature (PVT) variations, the proposed driver can operate properly without additional calibration time. To reduce the power consumption of the calibration loops, scaled replicas of the actual driver are used. Moreover, an analysis of design optimization for the proposed driver is presented. The proposed driver was fabricated in 65‐nm CMOS technology and verified at a 5‐Gb/s data rate. Measurement results show that the proposed driver has a voltage swing of 600 mVpp and a horizontal eye opening of 0.5 UI. The prototype chip consumes 6 mW at a 1.0‐V supply. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
112.
Soft X‐ray Ptychographic Imaging and Morphological Quantification of Calcium Silicate Hydrates (C–S–H)
下载免费PDF全文
![点击此处可从《Journal of the American Ceramic Society》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Sungchul Bae Rae Taylor David Shapiro Peter Denes John Joseph Rich Celestre Stefano Marchesini Howard Padmore Tolek Tyliszczak Tony Warwick David Kilcoyne Pierre Levitz Paulo J. M Monteiro 《Journal of the American Ceramic Society》2015,98(12):4090-4095
Morphological details of calcium silicate hydrate (C–S–H) stemming from the hydration process of Portland cement (PC) phases are crucial for understanding the PC‐based systems but are still only partially known. Here we introduce the first soft X‐ray ptychographic imaging of tricalcium silicate (C3S) hydration products. The results are compared using both scanning transmission X‐ray and electron transmission microscopy data. The evidence shows that ptychography is a powerful method to visualize the details of outer and inner product C–S–H of fully hydrated C3S, which have fibrillar and an interglobular structure with average void sizes of 20 nm, respectively. The high‐resolution ptychrography image enables us to perform morphological quantification of C–S–H, and, for the first time, to possibly distinguish the contributions of inner and outer product C–S–H to the small angle scattering of cement paste. The results indicate that the outer product C–S–H is mainly responsible for the q?3 regime, whereas the inner product C–S–H transitions to a q?2 regime. Various hypotheses are discussed to explain these regimes. 相似文献
113.
Xuetao Shi Serge Ostrovidov Yihua Zhao Xiaobin Liang Motohiro Kasuya Kazue Kurihara Ken Nakajima Hojae Bae Hongkai Wu Ali Khademhosseini 《Advanced functional materials》2015,25(15):2250-2259
Engineering living tissues that simulate their natural counterparts is a dynamic area of research. Among the various models of biological tissues being developed, fiber‐shaped cellular architectures, which can be used as artificial blood vessels or muscle fibers, have drawn particular attention. However, the fabrication of continuous microfiber substrates for culturing cells is still limited to a restricted number of polymers (e.g., alginate) having easy processability but poor cell–material interaction properties. Moreover, the typical smooth surface of a synthetic fiber does not replicate the micro‐ and nanofeatures observed in vivo, which guide and regulate cell behavior. In this study, a method to fabricate photocrosslinkable cell‐responsive methacrylamide‐modified gelatin (GelMA) fibers with exquisite microstructured surfaces by using a microfluidic device is developed. These hydrogel fibers with microgrooved surfaces efficiently promote cell encapsulation and adhesion. GelMA fibers significantly promote the viability of cells encapsulated in/or grown on the fibers compared with similar grooved alginate fibers used as controls. Importantly, the grooves engraved on the GelMA fibers induce cell alignment. Furthermore, the GelMA fibers exhibit excellent processability and could be wound into various shapes. These microstructured GelMA fibers have great potential as templates for the creation of fiber‐shaped tissues or tissue microstructures. 相似文献
114.
Magnificent elongation of bridge span length, especially of recently constructed cable stayed bridges and suspension bridges, can be achieved by technological as well as new material development of orthotropic steel deck systems. One such effort is to install curved bulkhead plates inside longitudinal u-ribs, which was analytically and experimentally demonstrated to reduce significant amount of concentrated stresses without sacrificing self-weight of the whole structure. In this paper, the optimal shape of more effective bulkhead plates is characterized by computational analysis. And it is verified from fatigue tests of a 3-dimensional full-scale structure that the fatigue performance can be significantly improved by installing the optimal bulkhead plates and by fabricating the structure out of recently developed high performance steel for bridges. 相似文献
115.
Joung Hyun La Ki Tae Bae Sang Yul Lee Myung Kon Song Kyung Hoon Nam Yong Hwa Jung 《Journal of Mechanical Science and Technology》2016,30(10):4417-4421
For the purpose of utilizing induction heating in the evaporation process, the effects of induction coil design and droplet size on induction heating efficiency are investigated. Electro-magnetic simulations with various induction coil designs were conducted to predict the electro-magnetic field distribution. The induction coils were fabricated in order to verify the simulation results under atmospheric evaporation test conditions. The electro-magnetic simulation results indicated that the magnetic field became widened around the Zn droplet when the size of the Zn droplet increased. This in turn attributed to the increase in induction heating energy efficiency. The energy efficiency of the induction coil with 4-windings was the highest among the 3-, 4-, and 5-windings induction coils. Energy efficiency tendencies derived by the atmospheric evaporation tests corresponded well to the simulation results, and maximum energy efficiency was measured to be 42% under the atmospheric evaporation tests. 相似文献
116.
Moon Jae-Sung Kim Choonghyun Youm Youngil Bae Joonbum 《Journal of Mechanical Science and Technology》2018,32(5):2289-2298
Journal of Mechanical Science and Technology - This paper presents the design and modeling of the UNI-Copter, a portable spherical unmanned aerial vehicle (UAV) that is powered by a single rotor.... 相似文献
117.
A thermally cured epoxy‐siloxane hybrid material that is curable at low temperature (L‐expoxy hybrimer) was investigated for use as an LED encapsulant. This new hybrimer was fabricated using thermally initiated, cationic polymerization of cycloaliphatic epoxy oligosiloxane (CAEO) resin, derived from non‐hydrolytic sol – gel, mixed with oxetane hardener in the presence of a hexafluoroantimonate‐type thermo‐cationic initiator. The L‐epoxy hybrimer was cured at a lower temperature (below 120 ° C) than previously reported for an epoxy hybrimer with anhydride hardener (above 180 ° C). The L‐epoxy hybrimer showed high thermal resistance to yellowing under long‐term high temperature condition, and maintained good optical transmittance. Also, it had a high refractive index (up to 1.57), as well as the hardness (Shore D 80), and low water‐vapor permeability, w hen the new hybrimer was used to encapsulate an LED, it showed good adhesion without cracks or delamination and maintained their initial performance after the long‐term aging tests (120 and 85 ° C at 85% humidity). © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39968. 相似文献
118.
The electric field induced microdomain orientations has been an interesting research topic. In this article, the effect of nanoparticle surface functionality on microdomain alignments in block copolymer/nanoparticle hybrid thin films was investigated with transmission electron microscopy experiments. The presence of gold nanoparticles influenced the microdomain orientation behaviors of block copolymer/nanoparticle thin films. The possibility for complete alignment normal to the substrate was illustrated by controlling electric field strength, concentration, and surface ligands of nanoparticles. This work provides basic and essential data to understand the properties and behaviors of emerging block copolymer/nanoparticle hybrid thin films. 相似文献
119.
Jae Hyeok Park Chang-Ha Lee Young Cheol Park Dowon Shun Dal-Hee Bae Jaehyeon Park 《Drying Technology》2014,32(3):268-278
This research explores the production of low-moisture, high-rank coal using a batch-type, laboratory-scale, circulating fluidized bed to dry low-rank Indonesian coal with a high moisture content of 35 wt%. The operation was performed using air as a fluidization gas in a riser (a 4-m-tall pipe with an inner diameter of 0.04 m) at a gas velocity ranging from 2.0 to 2.7 m/s and a riser temperature of 80 to 150°C. The electric heaters were installed in the upper part of a downcomer to prevent the condensation of the evaporated moist- ure. The drying rate of the coal was investigated in terms of the inlet gas temperature, the gas velocity, and the drying time in order to determine the optimum operating conditions. Changes in the moist- ure content of the coal, before and after the experiments, were char- acterized by a proximate analysis, an ultimate analysis, the higher heating value (HHV), the lower heating value (LHV), a particle size analysis, and by the equilibrium moisture content. The results show that 70 to 80 wt% (wet basis, wb) of the total moisture can be reduced when the gas velocity of the riser is 2.0 m/s and the gas temperature is 150°C. In experiments, a simple mathematical model based on the heat and mass balances and a thin-layer drying model were simul- taneously used to predict the drying behavior of coal under the given operating conditions. The results of the model are similar to those of the experiment. 相似文献
120.
Cheongwon Bae Jaedeok Lee Lehan Yao Suhyeon Park Yeonju Lee Jieun Lee Qian Chen Juyeong Kim 《Nano Research》2021,14(1):66-73
Core-shell hybrid nanomaterials have shown new properties and functions that are not attainable by their single counterparts.Nanoscale confinement effect by porous inorganic shells in the hybrid nanostructures plays an important role for chemical transformation of the core nanoparticles.However,metal-organic frameworks(MOFs)have been rarely applied for understanding mechanical insight into such nanoscale phenomena in confinement,although MOFs would provide a variety of properties for the confining environment than other inorganic shells such as silica and zeolite.Here,we examine chemical transformation of a gold nanorod core enclosed by a zeolitic imidazolate framework(ZIF)through chemical etching and regrowth,followed by quantitative analysis in the core dimension and curvature.We find the nanorod core shows template-effective behavior in its morphological transformation.In the etching event,the nanorod core is spherically carved from its tips.The regrowth on the spherically etched core inside the ZIF gives rise toformation of a raspberry-like branched nanostructure in contrast to the growth of an octahedral shape in bulk condition.We attribute the shell-directed regrowth to void space generated at the interfaces between the etched core and the ZIF shell,intercrystalline gaps in mult-domain ZIF shells,and local structural deformation from the acidic reaction conditions. 相似文献