全文获取类型
收费全文 | 5775篇 |
免费 | 102篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 56篇 |
综合类 | 2篇 |
化学工业 | 762篇 |
金属工艺 | 120篇 |
机械仪表 | 66篇 |
建筑科学 | 176篇 |
矿业工程 | 29篇 |
能源动力 | 52篇 |
轻工业 | 337篇 |
水利工程 | 22篇 |
石油天然气 | 8篇 |
无线电 | 299篇 |
一般工业技术 | 518篇 |
冶金工业 | 3041篇 |
原子能技术 | 39篇 |
自动化技术 | 352篇 |
出版年
2022年 | 32篇 |
2021年 | 45篇 |
2020年 | 53篇 |
2019年 | 45篇 |
2018年 | 60篇 |
2017年 | 42篇 |
2016年 | 69篇 |
2015年 | 58篇 |
2014年 | 79篇 |
2013年 | 87篇 |
2012年 | 115篇 |
2011年 | 137篇 |
2010年 | 114篇 |
2009年 | 109篇 |
2008年 | 116篇 |
2007年 | 113篇 |
2006年 | 102篇 |
2005年 | 126篇 |
2004年 | 79篇 |
2003年 | 84篇 |
2002年 | 83篇 |
2001年 | 88篇 |
2000年 | 83篇 |
1999年 | 136篇 |
1998年 | 922篇 |
1997年 | 541篇 |
1996年 | 345篇 |
1995年 | 265篇 |
1994年 | 193篇 |
1993年 | 222篇 |
1992年 | 75篇 |
1991年 | 86篇 |
1990年 | 82篇 |
1989年 | 78篇 |
1988年 | 61篇 |
1987年 | 56篇 |
1986年 | 58篇 |
1985年 | 66篇 |
1984年 | 31篇 |
1983年 | 33篇 |
1982年 | 46篇 |
1981年 | 51篇 |
1980年 | 51篇 |
1979年 | 50篇 |
1978年 | 25篇 |
1977年 | 93篇 |
1976年 | 172篇 |
1975年 | 24篇 |
1974年 | 18篇 |
1972年 | 18篇 |
排序方式: 共有5879条查询结果,搜索用时 9 毫秒
101.
Matti Schneider Felix Ospald Matthias Kabel 《International journal for numerical methods in engineering》2016,105(9):693-720
In this article, we propose to discretize the problem of linear elastic homogenization by finite differences on a staggered grid and introduce fast and robust solvers. Our method shares some properties with the FFT‐based homogenization technique of Moulinec and Suquet, which has received widespread attention recently because of its robustness and computational speed. These similarities include the use of FFT and the resulting performing solvers. The staggered grid discretization, however, offers three crucial improvements. Firstly, solutions obtained by our method are completely devoid of the spurious oscillations characterizing solutions obtained by Moulinec–Suquet's discretization. Secondly, the iteration numbers of our solvers are bounded independently of the grid size and the contrast. In particular, our solvers converge for three‐dimensional porous structures, which cannot be handled by Moulinec–Suquet's method. Thirdly, the finite difference discretization allows for algorithmic variants with lower memory consumption. More precisely, it is possible to reduce the memory consumption of the Moulinec–Suquet algorithms by 50%. We underline the effectiveness and the applicability of our methods by several numerical experiments of industrial scale. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
102.
Katie L. J. Cederberg Umaer Hanif Vicente Peris Sempere Julien Hdou Eileen B. Leary Logan D. Schneider Ling Lin Jing Zhang Anne M. Morse Adam Blackman Paula K. Schweitzer Suresh Kotagal Richard Bogan Clete A. Kushida Yo-El S. Ju Nayia Petousi Chris D. Turnbull Emmanuel Mignot The STAGES Cohort Investigator Group 《International journal of molecular sciences》2022,23(14)
Obstructive sleep apnea (OSA), a disease associated with excessive sleepiness and increased cardiovascular risk, affects an estimated 1 billion people worldwide. The present study examined proteomic biomarkers indicative of presence, severity, and treatment response in OSA. Participants (n = 1391) of the Stanford Technology Analytics and Genomics in Sleep study had blood collected and completed an overnight polysomnography for scoring the apnea–hypopnea index (AHI). A highly multiplexed aptamer-based array (SomaScan) was used to quantify 5000 proteins in all plasma samples. Two separate intervention-based cohorts with sleep apnea (n = 41) provided samples pre- and post-continuous/positive airway pressure (CPAP/PAP). Multivariate analyses identified 84 proteins (47 positively, 37 negatively) associated with AHI after correction for multiple testing. Of the top 15 features from a machine learning classifier for AHI ≥ 15 vs. AHI < 15 (Area Under the Curve (AUC) = 0.74), 8 were significant markers of both AHI and OSA from multivariate analyses. Exploration of pre- and post-intervention analysis identified 5 of the 84 proteins to be significantly decreased following CPAP/PAP treatment, with pathways involving endothelial function, blood coagulation, and inflammatory response. The present study identified PAI-1, tPA, and sE-Selectin as key biomarkers and suggests that endothelial dysfunction and increased coagulopathy are important consequences of OSA, which may explain the association with cardiovascular disease and stroke. 相似文献
103.
104.
105.
目前存在3个关键因素导致环锭纺产量无法进一步提高。介绍了一些有利于未来环锭纺技术进一步发展的基本情况。详细分析了环锭纺工序中的能耗问题,这是性能能否提高的基础。环锭纺产量的提高,不仅是技术上是否可行的问题,更重要的是能够获得良好的经济效益。 相似文献
106.
107.
108.
In this paper, we identify two cases in which the proposition for calculating time window penalties presented in Nagata, Y., Bräysy, O. and Dullaert, W. A penalty-based edge assembly memetic algorithm for the vehicle routing problem with time windows, Computers & Operations Research 2010;37(4): 724–37 yields incorrect results. We derive the corrected proposition and use numerical studies to show that a significant proportion of the evaluations performed by a Tabu Search for VRPTW falls under the two incorrect cases. Moreover, we demonstrate that the incorrect time window handling has a significant negative impact on the solution quality of the Tabu Search. 相似文献
109.
110.
James D. Hogan John G. Spray Robert J. Rogers Suporn Boonsue Gregory Vincent Markus Schneider 《International Journal of Impact Engineering》2011,38(12):931-939
The dynamic fracture of natural polyphase ceramic (granite) blocks by high-speed impact at 207 m/s, 420 m/s and 537 m/s has been investigated. An electromagnetic railgun was used as the launch system. Results reveal that the number of fragments increases substantially, and the dominant length scale in their probability distributions decreases, as the impact energy is increased. Micro-scale studies of the fracture surfaces reveals evidence of localized temperatures in excess of 2000 K brought on by frictional melting via fracturing and slip along grain boundaries in orthoclase and plagioclase, and via transgranular fracture (micro-cracking) in quartz. The formation of SiO2- and TiO2-rich spheroids on fracture surfaces indicates that temperatures in excess of 3500 K are reached during fracture. 相似文献