全文获取类型
收费全文 | 504篇 |
免费 | 30篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 14篇 |
综合类 | 1篇 |
化学工业 | 84篇 |
金属工艺 | 7篇 |
机械仪表 | 4篇 |
建筑科学 | 21篇 |
能源动力 | 15篇 |
轻工业 | 57篇 |
水利工程 | 2篇 |
石油天然气 | 6篇 |
无线电 | 93篇 |
一般工业技术 | 84篇 |
冶金工业 | 78篇 |
原子能技术 | 2篇 |
自动化技术 | 68篇 |
出版年
2022年 | 6篇 |
2021年 | 12篇 |
2020年 | 10篇 |
2019年 | 13篇 |
2018年 | 17篇 |
2017年 | 9篇 |
2016年 | 12篇 |
2015年 | 12篇 |
2014年 | 17篇 |
2013年 | 47篇 |
2012年 | 24篇 |
2011年 | 30篇 |
2010年 | 35篇 |
2009年 | 29篇 |
2008年 | 28篇 |
2007年 | 24篇 |
2006年 | 24篇 |
2005年 | 18篇 |
2004年 | 19篇 |
2003年 | 9篇 |
2002年 | 13篇 |
2001年 | 2篇 |
2000年 | 4篇 |
1999年 | 13篇 |
1998年 | 24篇 |
1997年 | 15篇 |
1996年 | 7篇 |
1995年 | 6篇 |
1994年 | 9篇 |
1993年 | 10篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1977年 | 2篇 |
1976年 | 7篇 |
1975年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有536条查询结果,搜索用时 31 毫秒
41.
Numerical simulation of shock diffraction on unstructured meshes 总被引:1,自引:0,他引:1
Shock diffraction over geometric obstacles is performed on two-dimensional unstructured triangular meshes using the AUSM+ flux-vector splitting scheme. Numerical simulations of shock diffraction using structured grids are reviewed in the literature, as are experimental results corresponding to the flow conditions studied. Present unstructured grid results for popular and challenging two-dimensional shock diffraction problems are presented and compared to experimental data and photographs. Benchmark and example test cases were chosen to cover a wide variety of Mach numbers for weak and strong shock waves, and for square and circular geometries. Both single and multiple obstacles are considered, as are obstacles located in the free field and confined in a channel. 相似文献
42.
In this paper, the robust delay‐dependent H∞ control for a class of uncertain systems with time‐varying delay is considered. An improved state feedback H∞ control is proposed to minimize the H∞‐norm bound via the LMI optimization approach. Based on the proposed result, delay‐dependent criteria are obtained without using the model transformation technique or bounded inequalities on cross product terms. The linear matrix inequality (LMI) optimization approach is used to design the robust H∞ state feedback control. Some numerical examples are given to illustrate the effectiveness of the approach. 相似文献
43.
A knowledge engineering approach to knowledge management 总被引:4,自引:0,他引:4
Lien F. Lai 《Information Sciences》2007,177(19):4072-4094
Knowledge management facilitates the capture, storage, and dissemination of knowledge using information technology. Methods for managing knowledge have become an important issue in the past few decades, and the KM community has developed a wide range of technologies and applications for both academic research and practical applications. In this paper, we propose a knowledge engineering approach (KMKE) to knowledge management. First, a knowledge modeling approach is used to organize and express various types of knowledge in a unified knowledge representation. Second, a verification mechanism is used to verify knowledge models based on the formal semantics of the knowledge representation. Third, knowledge models are classified and stored in a hierarchical ontology system. Fourth, a knowledge query language is designed to enhance the dissemination of knowledge. Finally, a knowledge update process is applied to modify the knowledge storage with respect to users’ needs. A knowledge management system for computer repair is used as an illustrative example. 相似文献
44.
The purpose of this study is to investigate the mixture performance and the sound absorption characteristic of porous asphalt mixture with different percentages of basic oxygen furnace (BOF) slag. Mixtures made with 0%, 25%, 50%, 75% and 100% BOF slag by volume as a coarse aggregate substitution were considered. The packing grading mixture design method (PGMDM) was applied in the design of porous asphalt. The test results show that BOF slag has high specific gravity, high absorption, high angularity, low L.A. abrasion, and low soundness compared with crushed stone (CS). The mixtures with BOF slag enhance skid resistance, moisture susceptibility, rutting resistance and sound absorption. Scanning electron microscope (SEM) used for micrograph demonstration shows that the rough surface pores and surface texture of BOF slag have a strong bond characteristic and an excellent interfacial zone for asphalt binder. The Duncan’s multiple range test results indicate that the BOF slag substitution percentage is significantly different in terms of mixture performance. The CS completely replaced by the BOF slag for porous asphalt mixture is recommended to obtain the optimum performance. 相似文献
45.
Shu‐Ping Lee Shyh‐Chyun Yang Yen‐Shih Cheng Wan‐Jung Lien Lean‐Teik Ng 《European Journal of Lipid Science and Technology》2010,112(7):712-719
Tocotrienols, a group of important phytonutrients of palm oil, have been shown to possess antioxidant, anticancer, neuroprotectory, and anti‐inflammatory activities. In this study, our objective was to examine the protective effects of tocotrienol‐rich fraction (TRF) from palm oil on chronic carbon tetrachloride (CCl4)‐induced hepatotoxicity in rats. Animals were subjected to vehicle only (control), CCl4 only, CCl4 + 100 mg/kg silymarin (silymarin), CCl4 + 25 mg/kg TRF (TRF‐25) and CCl4 + 50 mg/kg TRF (TRF‐50) treatments for a period of 8 wks. Results showed that daily oral administration of TRF‐25, TRF‐50, and silymarin prevented the elevation of serum glutamate oxalate transaminase (sGOT) and glutamate pyruvate transaminase (sGPT), liver thiobarbituric acid reactive substances (TBARS), triglycerides and total cholesterol levels, as well as enhancing the liver catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) levels in rats with hepatotoxicity. At 50 mg/kg, the hepatoprotection of TRF was as good as or better than silymarin (100 mg/kg) in normalization of oxidative stress parameters in liver injury rats. These results suggest that TRF exerts effective protection against chronic CCl4‐induced hepatic injury in rats, and its mechanism of action could be related to reducing oxidative stress in the liver tissue. 相似文献
46.
Simon Dan; Pham Lien B.; Le Quang A.; Holyoak Keith J. 《Canadian Metallurgical Quarterly》2001,27(5):1250
Previous research has indicated that decision making is accompanied by an increase in the coherence of assessments of the factors related to the decision alternatives. In the present study, the authors investigated whether this coherence shift is obtained before people commit to a decision, and whether it is obtained in the course of a number of other processing tasks. College students were presented with a complex legal case involving multiple conflicting arguments. Participants rated agreement with the individual arguments in isolation before seeing the case and after processing it under various initial sets, including playing the role of a judge assigned to decide the case. Coherence shifts were observed when participants were instructed to delay making the decision (Experiment 1), to memorize the case (Experiment 2), and to comprehend the case (Experiment 3). The findings support the hypothesis that a coherence-generating mechanism operates in a variety of processing tasks, including decision making. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
47.
Chen-Min Li I.-Cheng Yeh Shin-Feng Chen Tusang-Yuan Chiang Li-Chuan Lien 《Canadian Metallurgical Quarterly》2008,134(4):335-345
This research builds a virtual reality learning system for the digital terrain model surveying practice based on the triangular irregular network (TIN). The proposed system offers students an interactive, individual, three-dimensional, measurable, immediate feedback learning process. The system operating procedure is divided into five operations: (1) selecting topographical control points; (2) TIN editing; (3) evaluating errors; (4) analyzing errors; and (5) demonstrating performance. Students are able to carry out selecting the topographical control points and editing TIN under the virtual reality environment as if they implemented these surveying operations in the field. In addition, the magnitude and distribution of elevation errors can be recognized immediately after these operations are completed. Therefore, students have immediate feedback. After using the system in real practice courses, significant effects were found between the experimental set and contrast set. 相似文献
48.
Artificially reared infant rats were used to determine the effects of long-chain polyunsaturated fatty acid (LCP-UFA) supplementation
on blood and tissue concentrations of arachidonic acid (AA) and docosahexaenoic acid (DHA). Beginning at 7 d of age, infant
rats were fed for 10 d with rat milk formulas supplemented with AA at 0,0.5 and 1.0%, or supplemented with DHA at 0,0.5 and
1.0% of total fatty acid. The supplementation of AA increased accretion of the fatty acid in tissue and blood phospholipids
with a maximum increase of 9% in brain, 15% in liver, 25% in erythrocytes, and 43% in plasma above the values of unsupplemented
infant rats. Rat milk formula containing 1.0% of AA had no added benefits over that containing 0.5% of AA. The supplementation
of DHA increased phospholipid DHA by a maximum of 24% in brain, 87% in liver, 54% in erythrocytes, and 360% in plasma above
the unsupplemented control. The increase in tissue and blood DHA was concentration-dependent on formula fatty acid. Brain
phosphatidylcholine and phosphatidylethanolamine were similarly enriched with AA and DHA by supplementation of the corresponding
fatty acids. In general the observed increase of AA was accompanied by a decrease in 16:0, 18:1n−9, and/or 18:2n−6, whereas
the increased DHA was associated with a reduction of 18:1n−9, 18:2n−6, and/or 20:4n−6. Clearly, infant rats were more responsive
to DHA than AA supplementation, suggesting a great potential of dietary manipulation to alter tissue DHA concentrations. However,
the supplementation of DHA significantly decreased tissue and blood AA/DHA ratios (wt%/wt%), whereas there was little or no
change in the ratio by AA supplementation. Although the physiological implications of the levels of AA and DHA, and AA/DHA
ratios achieved under the present experimental conditions are not readily known, the findings suggest that artificial rearing
could provide a suitable model to investigate LCPUFA requirements using various sources of AA and DHA in rats. 相似文献
49.
Limp materials like textiles, leather, porous tissues, meat and fish fillets do represent challenges in automation. A universal gripping principle that is usable for all these materials is not known. This paper describes a new gripping principle based on a novel Coanda effect ejector meeting these challenges. This ejector allows the construction of a slim, plate-shaped vacuum gripper with multiple independent suction heads. Each suction head is powered by a newly patented lateral Coanda ejector that ensures gripping power on all soft or porous materials. The paper presents results of investigations on important parameters of the Coanda effect gripper. 相似文献
50.
James McGregor Zhenyu Huang Edward P.J. Parrott J. Axel Zeitler K. Lien Nguyen Jeremy M. Rawson Albert Carley Thomas W. Hansen Jean-Philippe Tessonnier Dang Sheng Su Detre Teschner Elaine M. Vass Axel Knop-Gericke R. Schlögl Lynn F. Gladden 《Journal of Catalysis》2010,269(2):329-339
The catalytic dehydrogenation (DH) and oxidative dehydrogenation (ODH) of light alkanes are of significant industrial importance. In this work both carbonaceous material deposited on VOx/Al2O3 catalysts during reaction and unsupported carbon nanofibres (CNFs) are shown to be active for the dehydrogenation of butane in the absence of gas-phase oxygen. Their activity in these reactions is shown to be dependent upon their structure, with different reaction temperatures yielding structurally different coke deposits. Terahertz time-domain spectroscopy (THz-TDS), among other techniques, has been applied to the characterisation of these deposits – the first time this technique has been employed in coke studies. TEM and other techniques show that coke encapsulates the catalyst, preventing access to VOx sites, without a loss of activity. Studies on CNFs confirm that carbonaceous materials act as catalysts in this reaction. Carbon-based catalysts represent an important new class of potential catalysts for DH and ODH reactions. 相似文献