全文获取类型
收费全文 | 21608篇 |
免费 | 2054篇 |
国内免费 | 1186篇 |
专业分类
电工技术 | 558篇 |
技术理论 | 3篇 |
综合类 | 1785篇 |
化学工业 | 4861篇 |
金属工艺 | 1802篇 |
机械仪表 | 998篇 |
建筑科学 | 2149篇 |
矿业工程 | 1024篇 |
能源动力 | 563篇 |
轻工业 | 1721篇 |
水利工程 | 528篇 |
石油天然气 | 673篇 |
武器工业 | 207篇 |
无线电 | 1048篇 |
一般工业技术 | 3109篇 |
冶金工业 | 1835篇 |
原子能技术 | 224篇 |
自动化技术 | 1760篇 |
出版年
2024年 | 78篇 |
2023年 | 315篇 |
2022年 | 579篇 |
2021年 | 677篇 |
2020年 | 728篇 |
2019年 | 648篇 |
2018年 | 614篇 |
2017年 | 813篇 |
2016年 | 790篇 |
2015年 | 756篇 |
2014年 | 1226篇 |
2013年 | 1462篇 |
2012年 | 1442篇 |
2011年 | 1533篇 |
2010年 | 1143篇 |
2009年 | 1258篇 |
2008年 | 1126篇 |
2007年 | 1368篇 |
2006年 | 1310篇 |
2005年 | 1101篇 |
2004年 | 911篇 |
2003年 | 823篇 |
2002年 | 719篇 |
2001年 | 559篇 |
2000年 | 473篇 |
1999年 | 466篇 |
1998年 | 322篇 |
1997年 | 289篇 |
1996年 | 178篇 |
1995年 | 164篇 |
1994年 | 160篇 |
1993年 | 119篇 |
1992年 | 97篇 |
1991年 | 83篇 |
1990年 | 82篇 |
1989年 | 73篇 |
1988年 | 53篇 |
1987年 | 37篇 |
1986年 | 28篇 |
1985年 | 28篇 |
1984年 | 26篇 |
1983年 | 24篇 |
1982年 | 15篇 |
1981年 | 15篇 |
1980年 | 10篇 |
1964年 | 11篇 |
1959年 | 10篇 |
1956年 | 8篇 |
1955年 | 11篇 |
1951年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Hemanshu Bhatt Kimberly Y. Donaldson D. P. H. Hasselman Kenneth Chyung Mark P. Taylor 《Journal of the American Ceramic Society》1991,74(6):1463-1465
A study concerning the effect of fiber orientation on the thermal conductivity of a uniaxial carbon-fiber-reinforced borosilicate glass was conducted. For thin specimens, and thick specimens with specimen sides cut parallel to the fiber direction, the dependence of thermal conductivity on fiber orientation showed excellent agreement with theoretical behavior predicted for a composite infinite in extent. In contrast, the thermal conductivity data for rectangular thick specimens fell well below the data for the thin and angled specimens. For fiber orientation of 45° and higher, at which the heat was directed toward the side of the specimen rather than across, the thermal conductivity values showed excellent agreement with theoretical behavior predicted for a finite composite strip with insulated sides. 相似文献
62.
Sarrazin Jean-Christophe; Giraudo Marie-Dominique; Pailhous Jean; Bootsma Reinoud J. 《Canadian Metallurgical Quarterly》2004,30(3):411
In 3 experiments, the authors studied the organization of spatiotemporal information in memory. Stimuli consisted of configurations of dots, presented sequentially. The stimuli were either proportional, with interdot distances corresponding to interdot durations, or not proportional, with interdol distances not corresponding to interdot durations. After a learning phase, participants reproduced the spatial (Experiment 1), temporal (Experiment 2), or spatial and temporal (Experiment 3) characteristics of the target 60 times in succession. In the nonproportional conditions, effects of variable interdot durations or distances on the reproduction of, respectively, constant distances (tau effect) or durations (kappa effect) were observed, whereas no such effects were observed when variable distances or durations were to be produced. Tau and kappa effects influenced the accuracy but not the variability of responses. The results are discussed in light of the distinction between properties of the stabilized mental image and the process of stabilization. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
63.
A study on the critical success factors for corporations embarking on knowledge community-based e-learning 总被引:1,自引:0,他引:1
Corporations have felt the pressure for fast-paced innovations and knowledge transfer as major driving forces in raising their sustainable competitive advantage and organizational total productivity. Thus, the development of the knowledge community through e-learning is an important strategy in implementing knowledge management policy. This paper illustrates an empirical study with which to conduct qualitative research of learning organization. From the case company’s real progress and practical experience, some core principles were extracted from four managerial aspects, such as: strategy, technology, process, and personnel. These aspects were analyzed in order to understand the value chain framework and the major concerns of knowledge community development. Further, the main benefits are addressed and certain critical factors are proposed and shown in this paper to ensure the success of corporations embarking on knowledge community-based e-learning. 相似文献
64.
文章从如何提高对工程量清单编制工作重要性的认识入手,分析了实现计价理念、计价侧重点和造价控制观念转变的必要性,重点阐述了提高工程量清单编制质量应给予足够重视的几个关键环节。 相似文献
65.
埕岛油田东部斜坡带下第三系油藏以三角洲、浊积扇砂体隐蔽油气藏为主,储层埋藏深、厚度变化大,油气成藏复杂。通过对该带的沉积特征、沉积体系和沉积物源的研究,指出其东下段砂体的分布主要受物源和沉积相带两方面控制,砂体只有在有效圈闭情况下才能成藏,并且从构造上总结了三种油藏类型。最后指出该带下一步勘探重点是沿主物源方向展布的、成藏条件良好的各种砂体。 相似文献
66.
In their comments on the authors' article (see record 2003-10163-009), R. C. Serlin, B. E. Wampold, and J. R. Levin (see record 2003-10163-011) and P. Crits-Christoph, X. Tu, and R. Gallop (see record 2003-10163-010) took issue with the authors' suggestion to evaluate therapy studies with nested providers with a fixed model approach. In this rejoinder, the authors' comment on Serlin et al's critique by showing that their arguments do not apply, are based on misconceptions about the purpose and nature of statistical inference, or are based on flawed reasoning. The authors also comment on Crits-Christoph et al's critique by showing that the proposed approach is very similar to, but less inclusive than, their own suggestion. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
67.
Electrostatic destabilization of water-in-crude oil emulsions: Application to a real case and evaluation of the Aibel VIEC technology 总被引:1,自引:0,他引:1
In the current study, the Aibel Vessel Internal Electrostatic Coalescer (VIEC) technology was tested for a real case scenario encountered in the production train of a UK oil field. Depressurized samples were collected both upstream and downstream of the first stage separator. The separation performance was discussed with respect to water cut and droplet size distribution of the emulsions, and the effect of chemical treatment. Issues with respect to representative sampling and testing have been discussed. The application of an external AC electrical field has been shown to significantly enhance the separation of the aqueous phase from tight emulsions, both when it was used alone and in combination with a commercial demulsifier. By using the VIEC technology, the time for separation could be reduced from 8 min to 2 min and the overall BS&W in the emulsions was improved from 45% or 60% to a residual water content of 5-20%. Destabilization of a 45% water-in-oil emulsion by electrical and chemical treatment (20/40 ppm) produced oil in the 2-7% BS&W range whereas the corresponding tests without applying an electrostatic field led to a BS&W greater than 25%. The achieved results strongly suggest that the VIEC technology can resolve the stable emulsion bands encountered in the Schiehallion train and add flexibility or increased production rate to the process. The results also suggest the importance of further studies on the destabilization performances achieved by electrostatic means. 相似文献
68.
Hsu‐Wei Fang Hsien‐Chieh Wang Teh‐Hua Tsai Wei‐Bor Tsai Shao‐Yi Hou Hsuan‐Liang Liu Wun‐Hsing Lee Yung‐Chang Lu Chun‐Hsiung Huang 《应用聚合物科学杂志》2008,108(4):2428-2437
Wear of ultrahigh‐molecular‐weight polyethylene (UHMWPE) and wear‐particle‐induced osteolysis and bone resorption are the major factors causing the failure of total joint replacements. It is feasible to improve the lubrication and reduce the wear of artificial joints. We need further understanding of the lubrication mechanism of the synovial fluid. The objective of this study is to evaluate the lubricating ability of three major components in the synovial fluid: albumin, globulin, and phospholipids. An accelerated wear testing procedure in which UHMWPE is rubbed against a microfabricated surface with controlled asperities has been developed to evaluate the lubrication behavior. An analysis of the wear particle dimensions and wear amount of the tests has provided insights for comparing their lubrication performance. It is concluded that the presence of biomolecules at the articulating interface may reduce friction. A higher concentration of a biological lubricant leads to a decrease in the wear particle width. In addition, in combination with the wear results and mechanical analysis, the roles of individual biomolecules contributing to friction and wear at the articulating interface are discussed. These results can help us to identify the role of the biomolecules in the boundary lubrication of artificial joints, and further development of lubricating additives for artificial joints may be feasible. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
69.
Yu. S. Yakovlev 《Cybernetics and Systems Analysis》2003,39(5):765-776
Distinctive features of architectural-structural organization and use of memory networks are considered with the aim of choosing an optimal configuration in designing distributed computer systems. 相似文献
70.
ABSTRACT: Popcorn was oiled and coated in a tumble drum nonelectrostatically and electrostatically with sugar, cornstarch, salt, cellulose, maltodextrin, all-purpose flour, whole-wheat flour, or soy flour. Particle size, density, flowability, and chargeability were correlated to transfer efficiency using regression analysis. Of the various methods to measure chargeability, charge-to-mass and adhesion improvement were the most significant. For nonelectrostatic coating, small, dense, free-flowing powders were most efficient. Small, free-flowing highly charging powders were most efficient for electrostatic coating. Percent improvement was the highest for the least efficient powders. The greatest benefit with electrostatic coating was for low density, highly charging powders with no effect of size. 相似文献