全文获取类型
收费全文 | 2088篇 |
免费 | 107篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 17篇 |
化学工业 | 458篇 |
金属工艺 | 42篇 |
机械仪表 | 27篇 |
建筑科学 | 100篇 |
矿业工程 | 4篇 |
能源动力 | 28篇 |
轻工业 | 217篇 |
水利工程 | 18篇 |
石油天然气 | 3篇 |
无线电 | 134篇 |
一般工业技术 | 336篇 |
冶金工业 | 419篇 |
原子能技术 | 24篇 |
自动化技术 | 371篇 |
出版年
2023年 | 26篇 |
2022年 | 28篇 |
2021年 | 42篇 |
2020年 | 36篇 |
2019年 | 36篇 |
2018年 | 66篇 |
2017年 | 53篇 |
2016年 | 58篇 |
2015年 | 42篇 |
2014年 | 55篇 |
2013年 | 123篇 |
2012年 | 99篇 |
2011年 | 133篇 |
2010年 | 112篇 |
2009年 | 81篇 |
2008年 | 108篇 |
2007年 | 98篇 |
2006年 | 70篇 |
2005年 | 84篇 |
2004年 | 73篇 |
2003年 | 59篇 |
2002年 | 54篇 |
2001年 | 39篇 |
2000年 | 31篇 |
1999年 | 29篇 |
1998年 | 54篇 |
1997年 | 38篇 |
1996年 | 37篇 |
1995年 | 27篇 |
1994年 | 35篇 |
1993年 | 34篇 |
1992年 | 29篇 |
1991年 | 22篇 |
1990年 | 24篇 |
1989年 | 25篇 |
1988年 | 16篇 |
1987年 | 19篇 |
1986年 | 14篇 |
1985年 | 17篇 |
1984年 | 20篇 |
1983年 | 17篇 |
1982年 | 22篇 |
1981年 | 17篇 |
1980年 | 13篇 |
1979年 | 22篇 |
1978年 | 7篇 |
1977年 | 7篇 |
1976年 | 5篇 |
1975年 | 6篇 |
1958年 | 5篇 |
排序方式: 共有2198条查询结果,搜索用时 15 毫秒
991.
The nature of design problems facing industry today often requires the use of cross-disciplinary teams in order to maximise innovation. Three case studies were used to answer the research question: What factors contribute to the success of virtual cross-disciplinary design teams in large multinational engineering corporations? Results indicate that factors that contribute to success include the context in which teams work, the method by which teams do their work, and the media by which teams communicate. In addition, this study also found that technology facilitates, but does not take the place of, well-defined and shared processes. 相似文献
992.
In this study, the parameters which influence strength of the open-cell reaction bonded silicon nitride foams were investigated. These parameters include the monomer content in the suspension, the porosity level of the foam, the nitriding atmosphere including N2 and N2–4 %H2, and the nitriding temperature ranging from 1350 to 1425 °C. The nitriding mechanisms dominating under different nitriding conditions were also studied based on the phase and microstructural analysis. It was observed that there is a minimum monomer concentration of 25 wt% required in the premix solution to obtain a defect-free and homogeneous RBSN foam. Increasing the monomer content only from 15 to 20 wt% resulted in a threefold increase in the foam strength. The high porosity level of the foam which is above 70 vol% significantly affects the nitriding mechanisms and microstructures compared to those of dense RBSN ceramics. The maximum strength was obtained for the foams nitrided under N2–H2 atmospheres, and the nitriding temperature had a negligible effect on the foam strength when H2 is present in the atmosphere. α-Si3N4 is also the dominant phase in the microstructure in the presence of H2 regardless of the nitriding temperature. It was observed that β-Si3N4 can also be present in high quantities when N2 atmospheres are used. β-Si3N4 is present in the microstructures in two different morphologies including interlocking rods and angular grains. Each morphology forms based on a specific nitriding mechanism. 相似文献
993.
Ziemek Robin Piribauer Jakob Funke Florian Jantsch Simon Baier Christel 《Innovations in Systems and Software Engineering》2022,18(3):347-367
Innovations in Systems and Software Engineering - By combining two of the central paradigms of causality, namely counterfactual reasoning and probability-raising, we introduce a probabilistic... 相似文献
994.
Attending to structural programming features predicts differences in learning and motivation
下载免费PDF全文
![点击此处可从《Journal of Computer Assisted Learning》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Eben B. Witherspoon Christian D. Schunn Ross M. Higashi Robin Shoop 《Journal of Computer Assisted Learning》2018,34(2):115-128
Educational robotics programs offer an engaging opportunity to potentially teach core computer science concepts and practices in K–12 classrooms. Here, we test the effects of units with different programming content within a virtual robotics context on both learning gains and motivational changes in middle school (6th–8th grade) robotics classrooms. Significant learning gains were found overall, particularly for groups introduced to content involving program flow, the structural logic of program execution. Relative gains for these groups were particularly high on items that require the transfer of knowledge to dissimilar contexts. Reaching units that included program flow content was also associated with greater maintenance of programming interest when compared with other units. Therefore, our results suggest that explicit instruction in the structural logic of programming may develop deeper transferrable programming knowledge and prevent declines in some motivational factors. 相似文献
995.
Robin A. Ralston Helen Truby Claire E. Palermo Karen Z. Walker 《Critical reviews in food science and nutrition》2014,54(9):1167-1179
Colorectal cancer is the second most prevalent cancer worldwide. A systematic review and meta-analysis of prospective studies was conducted to examine the association between intake of different types of dairy foods during adulthood and the development of colorectal cancer, specifically comparing nonfermented milk, solid cheese, and fermented milk. Seven databases were systematically searched and 15 cohort studies selected for inclusion, involving over 900,000 subjects and over 5200 colorectal cancer cases. Meta-analysis resulted in an overall relative risk of colon cancer of 0.74 (95% confidence interval 0.60–0.91) in men consuming nonfermented milk (highest intake category averaging 525 g/day). No association was found between consumption of nonfermented milk and rectal cancer in men or nonfermented milk and colon or rectal cancer in women. No protective association was found between consumption of solid cheese or fermented milk and colorectal cancer. Reasons for the differences in the impact of nonfermented milk, solid cheese, and fermented milk in the colon are discussed. This meta-analysis supports the inverse association between nonfermented milk consumption and risk of colon cancer in men, and provides an evidence base to assist in the formulation of dietary guidelines involving dairy foods. 相似文献
996.
997.
Robin Augustine 《国际聚合物材料杂志》2016,65(1):28-37
Even though the biodegradability of polycaprolactone (PCL) is well established, few studies have carried out on the effect of nanofillers on the in vitro degradability of electrospun PCL membranes. Thus, the authors incorporated common nanofiller zinc oxide (ZnO) nanoparticles in electrospun PCL membranes. From the study of morphological schanges as well as the changes in crystallinity, it is clear that the ZnO nanoparticles accelerated the degradation of PCL. The FTIR results ascertain that the hydrolysis of the PCL nanofibers generates free hydroxyl and carbonyl groups in the bulk of the polymer. The tensile property of the PCL/ZnO nanocomposite membranes decreased with an increase in filler loading during degradation. 相似文献
998.
Iván Zapata‐González Robin A. Hutchinson Kevin A. Payne Enrique Saldívar‐Guerra 《American Institute of Chemical Engineers》2016,62(8):2762-2777
In this work the molecular weight distribution (MWD) of several atom transfer radical polymerization (ATRP) techniques has been derived and solved using the Reduced Stiffness by Quasi Steady State Approximation (RSQSSA) methodology. The Quasi Steady State Approximation has been validated on the living radicals for normal, Simultaneous Reversible and Normal Initiation and Activators Regenerated by Electron Transfer (ARGET), and it is shown that the information lost due to its application is negligible. According to these results, RSQSSA shows the best performance in terms of wall‐clock time and required memory in comparison to implicit techniques and Predici. In the case of the ARGET technique, the model predictions show good agreement with experimental data. Finally, an analysis on the impact of the slow and fast activation of the initiator on the MWD using ARGET has been carried out, indicating that the optimal initiator to control the MWD should exhibit activation‐deactivation rates very similar to those of the polymeric equilibrium. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2762–2777, 2016 相似文献
999.
1000.