全文获取类型
收费全文 | 2197篇 |
免费 | 37篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 96篇 |
综合类 | 1篇 |
化学工业 | 416篇 |
金属工艺 | 79篇 |
机械仪表 | 38篇 |
建筑科学 | 35篇 |
能源动力 | 71篇 |
轻工业 | 126篇 |
水利工程 | 5篇 |
石油天然气 | 1篇 |
无线电 | 249篇 |
一般工业技术 | 423篇 |
冶金工业 | 516篇 |
原子能技术 | 63篇 |
自动化技术 | 116篇 |
出版年
2023年 | 14篇 |
2022年 | 25篇 |
2021年 | 38篇 |
2020年 | 15篇 |
2019年 | 12篇 |
2018年 | 23篇 |
2017年 | 30篇 |
2016年 | 31篇 |
2015年 | 24篇 |
2014年 | 50篇 |
2013年 | 88篇 |
2012年 | 61篇 |
2011年 | 79篇 |
2010年 | 74篇 |
2009年 | 55篇 |
2008年 | 72篇 |
2007年 | 81篇 |
2006年 | 76篇 |
2005年 | 65篇 |
2004年 | 63篇 |
2003年 | 51篇 |
2002年 | 65篇 |
2001年 | 54篇 |
2000年 | 47篇 |
1999年 | 68篇 |
1998年 | 219篇 |
1997年 | 140篇 |
1996年 | 90篇 |
1995年 | 66篇 |
1994年 | 58篇 |
1993年 | 47篇 |
1992年 | 30篇 |
1991年 | 21篇 |
1990年 | 26篇 |
1989年 | 21篇 |
1988年 | 23篇 |
1987年 | 19篇 |
1986年 | 24篇 |
1985年 | 20篇 |
1984年 | 18篇 |
1983年 | 16篇 |
1982年 | 23篇 |
1981年 | 16篇 |
1980年 | 17篇 |
1979年 | 6篇 |
1978年 | 15篇 |
1977年 | 12篇 |
1976年 | 26篇 |
1975年 | 8篇 |
1974年 | 5篇 |
排序方式: 共有2235条查询结果,搜索用时 15 毫秒
111.
Takao Tsukada Ken-ichi Sugioka Tomoya Tsutsumino Hiroyuki Fukuyama Hidekazu Kobatake 《International Journal of Heat and Mass Transfer》2009,52(21-22):5152-5157
Recently, a novel method of measuring the thermophysical properties, particularly thermal conductivity, of high-temperature molten materials using the electromagnetic levitation technique has been developed by Kobatake et al. [H. Kobatake, H. Fukuyama, I. Minato, T. Tsukada, S. Awaji, Noncontact measurement of thermal conductivity of liquid silicon in a static magnetic field, Appl. Phys. Lett. 90 (2007) 094102]; this method is based on a periodic laser-heating method, and entails the superimposing of a static magnetic field to suppress convection in an electromagnetically levitated droplet. In this work, to confirm the fact that a static magnetic field really suppresses convection in a molten silicon droplet in an electromagnetic levitator, numerical simulations of convection in the droplet and periodic laser heating in the presence of convection have been carried out. Here, the convections driven by buoyancy force, thermocapillary force due to the temperature dependence of the surface tension on the melt surface, and electromagnetic force in the droplet were considered. As a result, it was found that applying a static magnetic field of 4 T can suppress convection in a molten silicon droplet enough to measure the real thermal conductivity of molten silicon. 相似文献
112.
Masatoshi Hasegawa Mari Fujii Junichi Ishii Shinya Yamaguchi Eiichiro Takezawa Takashi Kagayama Atsushi Ishikawa 《Polymer》2014
A novel cycloaliphatic monomer for polyimides (PI), 1S,2S,4R,5R-cyclohexanetetracarboxylic dianhydride (H′-PMDA) is proposed in this work. H′-PMDA shows high polymerizability with various diamines in contrast to its isomer, i.e., conventional hydrogenated pyromellitic dianhydride (H-PMDA) and leads to highly flexible and colorless PI films with very high Tg's. In particular, the combinations with rigid structures of diamines give rise to PIs with significantly decreased coefficients of thermal expansion (CTE) owing to high extents of in-plane chain orientation induced by thermal imidization, whereas the H-PMDA-based counterparts do not. The decreased CTE reflects structural rigidity/linearity of the H′-PMDA-based diimide units as supported by liquid crystallinity observed in the corresponding model compound. Solution casting of a chemically imidized PI derived from H′-PMDA and 2,2′-bis(trifluoromethyl)benzidine (TFMB) results in a lower CTE than that of the thermally imidized counterpart, suggesting the presence of a self-orientation phenomenon during solvent evaporation. The mechanism is proposed in this work. H′-PMDA/TFMB and its copolymer systems can be useful as plastic substrates in image display devices and/or novel coating-type optical compensation films. 相似文献
113.
Hiromasa Ishikawa 《热应力杂志》2013,36(2):211-222
Abstract This paper presents a theoretical study of the stresses in an infinite circular solid cylinder subjected to rapid surface heating and cooling. A quasistatic, uncoupled, thermoelastoplastic analysis based on the incremental theory of plasticity is formulated, and a numerical procedure is developed for a method of successive elastic solutions. The material of the cylinder is assumed to have temperature-dependent properties and to be characterized by the Romberg-Osgood stress-strain relation. The transient and residual stress distributions are discussed in detail, along with variations of the equivalent stress and plastic strain with time. 相似文献
114.
Fast and Almost Complete Nitridation of Mesoporous Silica MCM-41 with Ammonia in a Plug-Flow Reactor
Fumitaka Hayashi Ken-ichi Ishizu Masakazu Iwamoto 《Journal of the American Ceramic Society》2010,93(1):104-110
The title reaction proceeded well to yield silicon (oxy)nitride at 973–1323 K using a plug-flow reactor. The degree of nitridation was studied as a function of temperature and time of nitridation, the sample weight, and the flow rate of ammonia. It was dependent on the reaction temperature and the amount of ammonia supplied per sample weight. The nitridation at 1273 K for 10–25 h yielded the oxynitride with 36–39 wt% nitrogen, which was very close to 40 wt% of Si3 N4 . Characterization with X-ray diffraction, field-emission scanning electron microscopy and transmission electron microscopy measurements, and nitrogen adsorption revealed the conversion of MCM-41 to the corresponding oxynitride without essential loss of the mesoporous structure, the decrements of the lattice constant and the pore diameter by 20–35%, and the increments of the wall thickness by ca. 45%. Solid-state 29 Si nuclear magnetic resonance spectra during the nitridation clearly showed fast decrease in SiO4 species and slow in SiO3 (OH). Various intermediate species, SiO x N y (NH2 or NH) z , were observed to be formed and finally, ca. 70% SiN4 species, ca. 20% SiN3 (NH2 or NH), and ca. 10% SiON2 (NH2 or NH) were produced, being consistent with the results of the above mentioned elemental analysis. 相似文献
115.
116.
Role of zinc compounds on the formation, morphology, and adsorption characteristics of β-FeOOH rusts
To simulate the corrosion of galvanized steel in marine zone, β-FeOOH was prepared by aging the FeCl3 solutions containing ZnCl2 and zinc rusts such as ZnO and zinc hydroxychloride (Zn5(OH)8Cl2·H2O:ZHC). Adding ZnCl2, ZnO, and ZHC inhibited the crystallization and particle growth of β-FeOOH and the inhibitory effect was in order of ZHC ≈ ZnO > ZnCl2. The adsorption of H2O and CO2 was suppressed by adding ZnCl2, ZnO, and ZHC. These results imply that the rust formed on galvanized steel in marine environment is more compact, amorphous, and hydrophobic in nature which may lead to improve the corrosion resistance. 相似文献
117.
Introduction to olfactory neuroepithelium 总被引:4,自引:0,他引:4
Nibu K 《Microscopy research and technique》2002,58(3):133-134
Among the five senses, the sense of smell (olfaction) is the most sensitive and emotional window on the outside world (Stern and Marx, 1999). The olfactory system recognizes and discriminates myriad odorants of diverse molecular structures. What makes the olfactory system so specific and sensitive? OE harboring the olfactory receptor neurons (ORNs) also has an another unusual characteristic ability that fascinates scientists. Neurogenesis in this tissue continues throughout lifetime. This unique character provides an elegant model to study neurogenesis and neuronal plasticity, since neuronal birth, differentiation, survival, axon pathfinding, target recognition, synapse formation, and cell death can be examined in the mature OE. This special issue of Microscopic Research and Technique presents the recent developments in this exciting field of neuroscience, “structure and function of olfactory neuroepithelium.” Microsc. Res. Tech. 58:133–134, 2002. © 2002 Wiley-Liss, Inc. 相似文献
118.
We applied a Mo/B4C multilayer coating to a laminar holographic grating with 2400 grooves/mm and a 1-m radius of curvature. By use of synchrotron soft x rays the multilayer-coated grating was evaluated to have diffraction efficiencies of 3.1% and 0.017% for s- and p-polarized radiation, respectively, at a 6.7-nm wavelength at a 45.35 degrees grazing angle of incidence in the +1 (inside) grating order. Thus the polarizance was estimated to be 98.9% at least. The zero-order peak was suppressed by the destructive interference caused by the groove profile. 相似文献
119.
Nakamura T. Okuda T. Kobayashi R. Muroya Y. Tsuruoka K. Ohsawa Y. Tsukuda T. Ishikawa S. 《IEEE journal of selected topics in quantum electronics》2005,11(1):141-148
We have successfully fabricated 1.3-/spl mu/m AlGaInAs strain-compensated multiple-quantum-well (MQW) buried-heterostructure (BH) lasers by narrow-stripe selective metalorganic vapor-phase epitaxy. Based on the optimization of AlGaInAs strain compensated MQW and the Al-oxidation-free BH process, we obtained a low-threshold current of 12.5 mA and a relaxation frequency of more than 10 GHz at 85/spl deg/C for Fabry-Perot lasers. For distributed feedback lasers, we demonstrated a 10-Gb/s operation and transmission of over 16 Km for a single mode fiber at 100/spl deg/C. Furthermore, a record-low 25.8-mA/sub p-p/ modulation current for a 10-Gb/s modulation at 100/spl deg/C was demonstrated with shorter cavity and high grating-coupling coefficient. A median life of more than 1/spl times/10/sup 5/ h at 85/spl deg/C was estimated after an aging test of over 5000 h for these lasers. These superior characteristics at high temperatures were achieved by the combination of the high differential gain of AlGaInAs strain compensated MQW and the BH structure. 相似文献
120.
A hybrid multi-agent system architecture for enterprise integration using computer networks 总被引:5,自引:1,他引:5
The manufacturing industries are now experiencing fierce pressure of competition from every corner on this planet. In addition, the advancement in computer networks and information technologies has been gradually reshaping the manufacturing companies by shifting from the industrial age to the information era. Due to these elevated competitiveness and advanced computer technology, a number of new manufacturing and management strategies (e.g., CE or CIM) have emerged for the innovation of manufacturing enterprises. Although they have different definitions and scopes, there are several common issues: inter-enterprise functions integration; inter-enterprise resources integration; and collaboration. This paper proposes a new multi-agent system (MAS) architecture to support the inter-enterprise functions/resources integration and collaboration over the networked environment, including the hybrid agent architecture and hybrid network architecture. In contrast to the existing agent architectures, the proposed agent architecture enables agents to exhibit the hybrid (continuous and discrete) behavior and interactions. In addition, our network architecture is more suitable for building the large-scale distributed manufacturing systems that are prone to dynamic random changes of their environment. Based on the proposed MAS architecture, a collaborative product development environment is implemented as a starting point, and a multidisciplinary team-oriented design problem is illustrated to provide the vision of the proposed MAS architecture. 相似文献