全文获取类型
收费全文 | 1941篇 |
免费 | 74篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 120篇 |
综合类 | 1篇 |
化学工业 | 538篇 |
金属工艺 | 40篇 |
机械仪表 | 34篇 |
建筑科学 | 26篇 |
矿业工程 | 2篇 |
能源动力 | 58篇 |
轻工业 | 217篇 |
水利工程 | 4篇 |
石油天然气 | 5篇 |
无线电 | 119篇 |
一般工业技术 | 379篇 |
冶金工业 | 265篇 |
原子能技术 | 45篇 |
自动化技术 | 167篇 |
出版年
2023年 | 13篇 |
2022年 | 27篇 |
2021年 | 56篇 |
2020年 | 19篇 |
2019年 | 29篇 |
2018年 | 34篇 |
2017年 | 27篇 |
2016年 | 48篇 |
2015年 | 51篇 |
2014年 | 56篇 |
2013年 | 107篇 |
2012年 | 89篇 |
2011年 | 116篇 |
2010年 | 85篇 |
2009年 | 89篇 |
2008年 | 104篇 |
2007年 | 83篇 |
2006年 | 84篇 |
2005年 | 65篇 |
2004年 | 55篇 |
2003年 | 62篇 |
2002年 | 65篇 |
2001年 | 45篇 |
2000年 | 43篇 |
1999年 | 50篇 |
1998年 | 111篇 |
1997年 | 71篇 |
1996年 | 46篇 |
1995年 | 51篇 |
1994年 | 40篇 |
1993年 | 25篇 |
1992年 | 17篇 |
1991年 | 18篇 |
1990年 | 7篇 |
1989年 | 6篇 |
1988年 | 11篇 |
1987年 | 9篇 |
1986年 | 6篇 |
1985年 | 11篇 |
1984年 | 14篇 |
1983年 | 7篇 |
1982年 | 11篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 7篇 |
1978年 | 9篇 |
1977年 | 10篇 |
1976年 | 10篇 |
1969年 | 3篇 |
1966年 | 2篇 |
排序方式: 共有2020条查询结果,搜索用时 187 毫秒
991.
Naoki Sasaki Hsiang‐Ting Chen Daisuke Sakamoto Takeo Igarashi 《Computer Animation and Virtual Worlds》2015,26(2):185-194
We present facetons, geometric modeling primitives designed for building architectural models especially effective for a virtual environment where six degrees of freedom input devices are available. A faceton is an oriented point floating in the air and defines a plane of infinite extent passing through the point. The polygonal mesh model is constructed by taking the intersection of the planes associated with the facetons. With the simple interaction of faceton, users can easily create 3D architecture models. The faceton primitive and its interaction reduce the overhead associated with standard polygonal mesh modeling, where users have to manually specify vertexes and edges which could be far away. The faceton representation is inspired by the research on boundary representations (B‐rep) and constructive solid geometry, but it is driven by a novel adaptive bounding algorithm and is specifically designed for 3D modeling activities in an immersive virtual environment. We describe the modeling method and our current implementation. The implementation is still experimental but shows potential as a viable alternative to traditional modeling methods. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
992.
Yoko Takada Toru Tsuji Naoki Okamoto Takeyasu Saito Kazuo Kondo Takeshi Yoshimura Norifumi Fujimura Koji Higuchi Akira Kitajima Akihiro Oshima 《Journal of Materials Science: Materials in Electronics》2014,25(5):2155-2161
Conductive aluminum-doped zinc oxide (AZO) was deposited by pulsed laser deposition as top electrodes for chemical solution deposition derived lanthanum modified lead zirconate titanate (PLZT) capacitors. Compared with PLZT capacitors with Pt top electrodes (Pt/PLZT/Pt), PLZT capacitors with AZO as top electrodes (AZO/PLZT/Pt) showed improved fatigue endurance after cycles of 200 kV/cm (10 V) were applied with a 100 μs pulse width at 1 ms intervals. By using a combination of AZO as the top electrode and as a thin buffer layer (10 nm) under PLZT thin films (AZO/PLZT/AZO/Pt), fatigue behavior was also improved compared with the case without an AZO buffer layer. The addition of either an Al2O3 or HfO2 encapsulation layer increased the remnant polarization ratio of PLZT capacitors (after annealing at 200 °C, 1 Torr, 3 % hydrogen atmosphere) to 0.80 and 0.57, respectively, comparing with 0.52 without an encapsulation layer. 相似文献
993.
Hiroyuki Shimoji Masato S. Abe Kazuki Tsuji Naoki Masuda 《Journal of the Royal Society Interface》2014,11(99)
Dominance hierarchy among animals is widespread in various species and believed to serve to regulate resource allocation within an animal group. Unlike small groups, however, detection and quantification of linear hierarchy in large groups of animals are a difficult task. Here, we analyse aggression-based dominance hierarchies formed by worker ants in Diacamma sp. as large directed networks. We show that the observed dominance networks are perfect or approximate directed acyclic graphs, which are consistent with perfect linear hierarchy. The observed networks are also sparse and random but significantly different from networks generated through thinning of the perfect linear tournament (i.e. all individuals are linearly ranked and dominance relationship exists between every pair of individuals). These results pertain to global structure of the networks, which contrasts with the previous studies inspecting frequencies of different types of triads. In addition, the distribution of the out-degree (i.e. number of workers that the focal worker attacks), not in-degree (i.e. number of workers that attack the focal worker), of each observed network is right-skewed. Those having excessively large out-degrees are located near the top, but not the top, of the hierarchy. We also discuss evolutionary implications of the discovered properties of dominance networks. 相似文献
994.
Naoki Uchiyama Takaya Nakamura Hidetomo Yanagiuchi 《International Journal of Machine Tools and Manufacture》2009,49(11):876-884
Although many researches have been conducted on contouring control for machine tool feed drive systems, to the best of authors’ knowledge, its effectiveness has been verified only through comparative experiments with industrial non-contouring (independent axial) controllers, or conventional contouring controllers such as the cross-coupling controller. Because control performance largely depends on controller gains, such comparisons involve some difficulties in demonstrating the effectiveness of contouring control. In other words, a similar control performance can be achieved if the non-contouring controller gains are appropriately assigned. This paper discusses the effectiveness of contouring controllers both analytically and experimentally. A new contouring controller design for three-dimensional machining is presented, which is extended from the authors’ biaxial design based on coordinate transformation. The contouring controller is concluded to be effective through an analysis of the proposed design, in that it provides performance comparable to non-contouring controllers with less control input variance. This property reduces the damage to machine tool systems and saves control energy. In addition, because an inherent contour error exists in the coordinate transformation approach, a method for reducing this error is presented to enhance the effectiveness of the contouring controller. Experimental results support the claims of this paper. 相似文献
995.
Tetsuya Shozui Satoshi Hayakawa Akiyoshi Osaka 《Surface & coatings technology》2009,203(16):2181-2185
Multilayer anatase films were coated by sol-gel technology on various substrates such as stainless-steel, alumina, and glass, respectively. Their in vitro apatite-forming ability was examined by immersion in Kokubo's simulated body fluid (SBF; pH 7.4, 36.5 °C). Although on anatase layer on alkali-free glass apatite was deposited within 7 d, no apatite was found on anatase deposited onto stainless steel, alumina or glass substrates within 7 d to prove they were bioinert. X-ray photoelectron spectroscopy was able to detect chromium, aluminum, or sodium on the surface of the anatase films. This indicated that these ions possibly inhibited the in vitro apatite-forming ability. 相似文献
996.
For the development of chlorine‐resistant nanofiltration membranes, a thin‐film‐composite membrane was prepared by the interfacial polymerization of N‐phenylethylenediamine and 1,3,5‐benzenetricarbonyl trichloride on a microporous polysulfone support substrate. The polymerization on the substrate surface was confirmed by Fourier transform infrared measurements, and membrane surface properties such as the roughness and ζ potential were characterized. Rejections of NaCl and isopropyl alcohol of the prepared membrane were 95 and 50%, respectively. The membrane showed much higher chlorine resistance than a commercial polyamide membrane when the membranes were immersed in an aqueous NaOCl solution. A field test was carried out with a spiral‐type membrane module. Tap water was treated by this module for more than 70 days under the condition of continuous NaOCl injection. The prepared membrane module was quite stable, and no distinguished change in the rejection and flux was recognized. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献
997.
Toshihiro Sakamoto Nhan Van Nguyen Hiroyuki Ohno Naoki Ishitsuka Masayuki Yokozawa 《Remote sensing of environment》2006,100(1):1-16
Multi-temporal Moderate Resolution Imaging Spectroradiometer (MODIS) data was used to estimate the spatial distribution of heading date and rice-cropping system employed in the Mekong Delta relative to seasonal changes in water resources in 2002 and 2003. We improved a Wavelet-based Filter for determining Crop Phenology (WFCP) and developed a Wavelet-based Filter for evaluating the spatial distribution of Cropping Systems (WFCS) to the interpretation of MODIS time-series data to determine the spatial distribution of rice phenology and various rice-cropping systems from the seasonal Enhanced Vegetation Index (EVI) data. The findings correspond well the physical characteristics of the cropping system in the Mekong Delta, which have changed over time in response to localized and seasonal changes in water resources. One such example is the double-irrigated rice-cropping system commonly employed in the upper Mekong Delta in the dry season to avoid damage due to the subsequent floods. The shortage of suitable irrigation water and intrusion of saline water in the coastal regions during the dry season has constrained the practice dry-season cropping and has meant that the double- and single-rainfed rice-cropping systems are employed in the rainy season. A triple-irrigated rice-cropping system is used in the central part of the Mekong Delta which is located midway between the flood-prone and salinity intrusion areas. Analysis of annual changes in the rice cropping systems between 2002 and 2003 showed that the triple-cropped rice expanded to the flood- and salinity-intrusion areas. This expansion indicates that the implementation of measures to limit the extent of flooding and salinity intrusion by improved farming technologies and improvements in land management. The heading dates in the upper Mekong Delta in 2003 were earlier than in 2002 by approximately 20 to 30 days. The reasons for this would be due to decreased flood runoff in 2002 compared to 2001, and implementation of government policies regarding early sowing of dry-season crops. Subsequent analysis of the MODIS data confirmed that the spatial distribution of rice-cropping systems was closely related to seasonal changes in river runoff regime in the Mekong Delta. 相似文献
998.
Factors of silicate layer dispersions in polymers have been studied with copolymers. The influence of the copolymerization ratio of copolymers and the alkyl chain lengths of organomodified reagents of organophilic clay has been examined. The dispersion of silicate layers in copolymers is dependent on the copolymerization ratios of the functional groups, that is, the polarity of the polymer matrix. The alkyl chain lengths of organomodified reagents also have an important influence on silicate layer dispersions. From a comprehensive viewpoint, the polarity matching between polymers and organophilic clay is an important factor for silicate layer dispersions in polymers. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1554–1557, 2005 相似文献
999.
Kiyoshi Okada Naoki Arimitsu Yoshikazu Kameshima Akira Nakajima Kenneth J.D. MacKenzie 《Applied Clay Science》2006,31(3-4):185-193
Various 2 : 1 type clay minerals were activated by H2SO4 treatment and their solid acidities were evaluated by NH3-temperature programmed desorption (TPD). Clay minerals with various degrees of Al substitution in the tetrahedral sheets were used as the starting materials. These included montmorillonite (ideally no tetrahedral Al), saponite (low content of tetrahedral Al), vermiculite (intermediate content of tetrahedral Al) and phlogopite (high tetrahedral Al content). All these samples showed increased solid acidity after selective leaching, the solid acidities varying in the order phlogopite < montmorillonite < vermiculite < saponite. The NH3-TPD spectra were deconvoluted into two peaks; the L-peak at < 200 °C corresponds to a weak acid site and the H-peak at > 250 °C corresponds to a strong acid site. The temperature of the H-peak was lowest in phlogopite (252 °C) and highest in saponite (305 °C). The generation of solid acidity in these samples is found to be related to the evolution of new tetrahedral Al sites showing a slightly different 27Al MAS NMR chemical shift from the original tetrahedral Al NMR resonance. 相似文献
1000.
Soichi Furukawa Taisuke Watanabe Tetsuya Koyama Junichi Hirata Naoki Narisawa Hirokazu Ogihara Makari Yamasaki 《Food Control》2009,20(1):53-58
Inactivation of the vegetative foodborne pathogens by high pressure carbon dioxide treatment (HPCT) was investigated. Pseudomonas aeruginosa IFO3445, Aeromonas hydrophila IFO13286, Salmonella enteritidis JCM3313, Salmonella typhimurium IID1000, Yersinia enterocolitica JCM1677, Escherichia coli O157:H7 ATCC35150, E. coli O157:H7 ATCC43889, Staphylococcus aureus FDA209P and Listeria monocytogenes 1/2a were used in this study. In all cases, HPCT at 35 °C, 10 MPa for 1 min reduced initial numbers by approximately 6 logs. In addition HPCT inactivation of 9 pathogenic strains of Bacillus cereus (mixture of spores and vegetative cells) was investigated. HPCT at 75 °C, 10 MPa for 120 min resulted in significant inactivation in all the strains. The effect of HPCT (30 MPa at 95 °C for up to 120 min) on the inactivation of Geobacillus stearothermophilus spores in the presence of sodium chloride (3% and 6% w/v), glucose (6% and 12% w/v) and ethanol (10% and 20% v/v) was also studied. Both sodium chloride and glucose had a protective effect and the level of inactivation was reduced. The effect was in proportion to the solute concentration. However, 10% and 20% ethanol did not significantly affect the level of inactivation. 相似文献