全文获取类型
收费全文 | 2656篇 |
免费 | 65篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 34篇 |
综合类 | 10篇 |
化学工业 | 539篇 |
金属工艺 | 83篇 |
机械仪表 | 60篇 |
建筑科学 | 51篇 |
能源动力 | 106篇 |
轻工业 | 136篇 |
水利工程 | 4篇 |
石油天然气 | 4篇 |
无线电 | 483篇 |
一般工业技术 | 479篇 |
冶金工业 | 297篇 |
原子能技术 | 17篇 |
自动化技术 | 422篇 |
出版年
2023年 | 11篇 |
2022年 | 42篇 |
2021年 | 67篇 |
2020年 | 22篇 |
2019年 | 24篇 |
2018年 | 34篇 |
2017年 | 32篇 |
2016年 | 50篇 |
2015年 | 61篇 |
2014年 | 89篇 |
2013年 | 188篇 |
2012年 | 131篇 |
2011年 | 173篇 |
2010年 | 147篇 |
2009年 | 189篇 |
2008年 | 152篇 |
2007年 | 159篇 |
2006年 | 115篇 |
2005年 | 83篇 |
2004年 | 84篇 |
2003年 | 63篇 |
2002年 | 79篇 |
2001年 | 54篇 |
2000年 | 46篇 |
1999年 | 39篇 |
1998年 | 124篇 |
1997年 | 70篇 |
1996年 | 60篇 |
1995年 | 33篇 |
1994年 | 37篇 |
1993年 | 26篇 |
1992年 | 25篇 |
1991年 | 30篇 |
1990年 | 20篇 |
1989年 | 18篇 |
1988年 | 10篇 |
1987年 | 7篇 |
1986年 | 11篇 |
1985年 | 13篇 |
1984年 | 16篇 |
1983年 | 7篇 |
1982年 | 11篇 |
1981年 | 11篇 |
1980年 | 9篇 |
1979年 | 8篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1976年 | 7篇 |
1973年 | 5篇 |
1971年 | 4篇 |
排序方式: 共有2725条查询结果,搜索用时 99 毫秒
81.
The purpose of this study was to evaluate the effectiveness of using procedural scaffoldings in fostering students’ group discourse levels and learning outcomes in a paper-plus-smartphone collaborative learning context. All participants used built-in camera smartphones to learn new knowledge by scanning Quick Response (QR) codes, a type of two-dimensional barcode, embedded in paper-based learning materials in this study. Sixty undergraduate and graduate students enrolled at a four-year university in southern Taiwan participated in this study. Participants were randomly assigned into two different groups, using procedural scaffoldings learning and non-procedural scaffoldings learning. The learning unit about the Long Tail, an important concept used in products sales, was the learning task that participants were expected to complete. During the experiment, pretest–posttest and the completed group worksheets were used to collect data. The researchers applied content analyses, chi-square test, t-test, and ANCOVA to answer research questions. The findings indicated that participants in the experimental group using procedural scaffoldings achieved better learning outcomes than their counterparts in the control group in terms of group discourse levels, group learning, and individual learning. 相似文献
82.
Moderators play an important role within a computer supported collaborative learning environment, and thus facilitative strategies and communication technology are nowadays used to enhance students’ learning. This study proposed facilitative strategies as a guide for students’ learning, and explored the influence of these strategies on the students’ online synchronous discussion. A total of 331 senior high school students from eight computer classes in northern Taiwan were recruited to participate in this study. They were randomly assigned into an experimental condition, with the moderators’ facilitation to complete online learning tasks, and the control condition without moderators’ support. To fulfill the goal of the research, four strategies—helping students focus on the main topic, facilitating students’ making argumentation, giving students positive feedback, and helping students sustain threaded discussion—were adopted to facilitate the online synchronous discussion in the experimental condition. According to the results of the content analysis, four group discussion patterns were revealed, including collaboration, centralization, partial contribution, and non-interaction. The findings suggest that the moderator helped enhance the collaboration pattern and increase the online participation rate. In addition, it was found that the strategies of helping students focus on the main topic and giving students positive feedback were frequently employed. 相似文献
83.
Laser technique application to polycrystalline silicon thin-film solar cell fabrication on glass substrates has received appreciable attention. In this paper, a laser-doping technique is developed for plasma-deposited amorphous silicon film. A process involving recrystallization, phosphorous diffusion and antireflection coating can be achieved simultaneously using the laser annealing process. The doping precursor, a phosphorous-doped titanium dioxide (TiO2) solution, is synthesized using a sol-gel method and spin-coated onto the sample. After laser irradiation, the polycrystalline silicon grain size was about 0.5∼1.0 μm with a carrier concentration of 2 × 1019 cm− 3 and electron mobility of 92.6 cm2/V s. The average polycrystalline silicon reflectance can be reduced to a value of 4.65% at wavelengths between 400 and 700 nm, indicating the upper TiO2 film of antireflection coating. 相似文献
84.
We describe the excimer-laser-induced crystallization of microcrystalline silicon films deposited by plasma-enhanced chemical vapor deposition (PECVD). Microcrystalline silicon films containing 2 at.% hydrogen can be used as precursor films for the laser recrystallization process without a dehydrogenation step, and provide a wider laser energy fluence process window than the previous explosive recrystallization for low temperature polysilicon (poly-Si) thin-film transistor (TFT) fabrication. Ellipsometry, transmission electron microscopy (TEM), and atomic force microscopy (AFM) are used to evaluate the laser irradiated films. Specially, we describe using atomic force microscopy to obtain plane-view grain microstructure images. 相似文献
85.
Knowledge-based system for railway scheduling 总被引:8,自引:0,他引:8
Tewei Chiang HaiYen Hau Hwan Ming Chiang Su Yun Kob Chao Ho Hsieh 《Data & Knowledge Engineering》1998,27(3):2552-312
In this paper, we describe a Knowledge-Based railway scheduling system (called RSS) for Taiwan Railway Administration's (TRA) railway scheduling operations. In our approach, the scheduling process is divided into two levels: global scheduling and local scheduling. In global scheduling, an initial train diagram is established by the Global Scheduler according to the master scheduling plan without considering conflicts. In local scheduling, scheduling conflicts are repaired by Local Scheduler. An embedded knowledge base provides advice for conflict resolution. Since cycles may exist among a sequence of repairs during the repair process, we also propose a cycle detection and resolution scheme in this paper. Through a graphic user interface, the user can interact with the Automatic Scheduler to solve the large-scale complex train scheduling problem in a cooperative and flexible fashion. 相似文献
86.
Fu-Shiung Hsieh 《IEEE transactions on systems, man, and cybernetics. Part A, Systems and humans : a publication of the IEEE Systems, Man, and Cybernetics Society》2004,34(1):65-79
Unreliable resources pose challenges in design of deadlock avoidance algorithms as resources failures have negative impacts on scheduled production activities and may bring the system to dead states or deadlocks. This paper focuses on the development of a suboptimal polynomial complexity deadlock avoidance algorithm that can operate in the presence of unreliable resources for assembly processes. We formulate a fault-tolerant deadlock avoidance controller synthesis problem for assembly processes based on controlled assembly Petri net (CAPN), a class of Petri nets (PNs) that can model such characteristics as multiple resources and subassembly parts requirement in assembly production processes. The proposed fault-tolerant deadlock avoidance algorithm consists of a nominal algorithm to avoid deadlocks for nominal system state and an exception handling algorithm to deal with resources failures. We analyze the fault-tolerant property of the nominal deadlock avoidance algorithm based on resource unavailability models. Resource unavailability is modeled as loss of tokens in nominal Petri Net models to model unavailability of resources in the course of time-consuming recovery procedures. We define three types of token loss to model 1) resource failures in a single operation, 2) resource failures in multiple operations of a production process and 3) resource failures in multiple operations of multiple production processes. For each type of token loss, we establish sufficient conditions that guarantee the liveness of a CAPN after some tokens are removed. An algorithm is proposed to conduct feasibility analysis by searching for recovery control sequences and to keep as many types of production processes as possible continue production so that the impacts on existing production activities can be reduced. 相似文献
87.
Design, optimization, and performance analysis of new photodiode structures for CMOS active-pixel-sensor (APS) imager applications 总被引:5,自引:0,他引:5
Chung-Yu Wu Yu-Chuan Shih Jeng-Feng Lan Chih-Cheng Hsieh Chien-Chang Huang Jr-Houng Lu 《IEEE sensors journal》2004,4(1):135-144
The dark current in the active-pixel-sensor (APS) cell of a CMOS imager is known to be mainly generated in the regions of bird's beak after the local oxidation of silicon process as well as the surface damage caused by the implantation of high doping concentration. Furthermore, shallow and deep pn-junctions can improve the photo-sensitivity for light of short and long wavelengths, respectively. In this paper, two new photodiode structures using p-substrate and lightly-doped sensor implant SN- as pn-junction photodiode with the regions of bird's beak embraced by SN- and p-field implants, respectively, are proposed and analyzed to reduce dark current and enhance the overall spectral response. 5 /spl mu/m/spl times/5 /spl mu/m APS cells fabricated in a 0.35-/spl mu/m single-poly-triple-metal (1P3M) 3.3-V CMOS process are designed by using the proposed photodiode structures. As shown from the experimental results, the two proposed photodiode structures of 5 /spl mu/m/spl times/5 /spl mu/m APS cells have lower dark currents of 30.6 mV/s and 35.2 mV/s at the reverse-biased voltage of 2 V and higher spectral response, as compared to the conventional structure and other photodiode structures. Thus, the two proposed new photodiode structures can be applied to CMOS imager systems with small pixel size, high resolution, and high quality. 相似文献
88.
A bibliometric analysis was performed to assess the quantitative trend of Patent Ductus Arteriosus (PDA) treatment research,
including intravenous injection of indomethacin and surgery. The documents studied were retrieved from the Science Citation Index (SCI) for the period from 1991 to 2002. The publication pattern concerning authorship, collaboration, original countries,
citation frequency, document type, language of publication, distribution of journals, page count and the most frequently cited
papers were performed. The results indicated that either treatment was not the recent emphasis of PDA research. The publishing
countries of both treatments have also denoted that these researches were mostly done in Europe and North America. Both surgery
and drug treatments had few international collaboration papers. English was the dominant language, and collaboration of two
to six authors was the most popular level of co-authorship.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
89.
Seismic Retrofit of Hollow Rectangular Bridge Columns 总被引:1,自引:0,他引:1
The seismic performance of rectangular hollow bridge columns is a significant issue of the high-speed rail project in Taiwan. The flexural ductility and shear capacity of such columns with the configuration of lateral reinforcement used in Taiwan have been studied recently. This paper reports that hollow rectangular bridge columns retrofitted with fiber-reinforced polymer (FRP) sheets were tested under a constant axial load and a cyclically reversed horizontal load to investigate their seismic behavior, including flexural ductility, dissipated energy, and shear capacity. An analytical model was also developed to predict the moment-curvature curve of sections and the load-displacement relationship of columns. Based on the test results, the seismic behavior of such columns will be presented. The test results were also compared to the proposed analytical model. It was found that the ductility factors of the tested piers are in the range from 3.4 to 6.3, and the proposed analytical model can predict the load-displacement relationship of such columns with acceptable accuracy. All in all, FRP sheets can effectively improve both the ductility factor and shear capacity of hollow rectangular bridge columns. 相似文献
90.
Kawamori E Lee JY Huang YJ Syugu WJ Song SX Hsieh TY Cheng CZ 《The Review of scientific instruments》2011,82(9):093502
This paper presents a newly developed lithium plasma emitter, which can provide quiescent and low-temperature collisionless conditions for magnetized plasma experiments. This plasma emitter generates thermal emissions of lithium ions and electrons to produce a lithium plasma. Lithium type beta-eucryptite and lanthanum-hexaboride (LaB(6)) powders were mixed and directly heated with a tungsten heater to synthesize ion and electron emissions. As a result, a plasma with a diameter of ~15 cm was obtained in a magnetic mirror configuration. The typical range of electron density was 10(12)-10(13) m(-3) and that of electron temperature was 0.1-0.8 eV with the emitter operation temperature of about 1500 K. The amplitude fluctuations for the plasma density were lower than 1%. 相似文献