全文获取类型
收费全文 | 15838篇 |
免费 | 1184篇 |
国内免费 | 418篇 |
专业分类
电工技术 | 601篇 |
综合类 | 597篇 |
化学工业 | 3217篇 |
金属工艺 | 515篇 |
机械仪表 | 568篇 |
建筑科学 | 923篇 |
矿业工程 | 231篇 |
能源动力 | 520篇 |
轻工业 | 1588篇 |
水利工程 | 217篇 |
石油天然气 | 309篇 |
武器工业 | 41篇 |
无线电 | 1504篇 |
一般工业技术 | 2303篇 |
冶金工业 | 1676篇 |
原子能技术 | 176篇 |
自动化技术 | 2454篇 |
出版年
2023年 | 165篇 |
2022年 | 313篇 |
2021年 | 541篇 |
2020年 | 409篇 |
2019年 | 418篇 |
2018年 | 471篇 |
2017年 | 464篇 |
2016年 | 493篇 |
2015年 | 520篇 |
2014年 | 602篇 |
2013年 | 983篇 |
2012年 | 923篇 |
2011年 | 1026篇 |
2010年 | 882篇 |
2009年 | 815篇 |
2008年 | 846篇 |
2007年 | 826篇 |
2006年 | 643篇 |
2005年 | 531篇 |
2004年 | 512篇 |
2003年 | 636篇 |
2002年 | 716篇 |
2001年 | 614篇 |
2000年 | 343篇 |
1999年 | 273篇 |
1998年 | 327篇 |
1997年 | 296篇 |
1996年 | 197篇 |
1995年 | 193篇 |
1994年 | 153篇 |
1993年 | 140篇 |
1992年 | 100篇 |
1991年 | 60篇 |
1990年 | 86篇 |
1989年 | 104篇 |
1988年 | 61篇 |
1987年 | 57篇 |
1986年 | 71篇 |
1985年 | 76篇 |
1984年 | 60篇 |
1983年 | 75篇 |
1982年 | 47篇 |
1981年 | 43篇 |
1980年 | 50篇 |
1979年 | 32篇 |
1978年 | 29篇 |
1977年 | 31篇 |
1976年 | 47篇 |
1975年 | 34篇 |
1974年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
Dr. Laurent David Dr. Mark Wenlock Dr. Patrick Barton Dr. Andreas Ritzén 《ChemMedChem》2021,16(17):2669-2685
Chameleonic properties, i. e., the capacity of a molecule to hide polarity in non-polar environments and expose it in water, help achieving sufficient permeability and solubility for drug molecules with high MW. We present models of experimental measures of polarity for a set of 24 FDA approved drugs (MW 405-1113) and one PROTAC (MW 1034). Conformational ensembles in aqueous and non-polar environments were generated using molecular dynamics. A linear regression model that predicts chromatographic apparent polarity (EPSA) with a mean unsigned error of 10 Å2 was derived based on separate terms for donor, acceptor, and total molecular SASA. A good correlation (R2=0.92) with an experimental measure of hydrogen bond donor potential, Δlog Poct-tol, was found for the mean hydrogen bond donor SASA of the conformational ensemble scaled with Abraham's A hydrogen bond acidity. Two quantitative measures of chameleonic behaviour, the chameleonic efficiency indices, are introduced. We envision that the methods presented herein will be useful to triage designed molecules and prioritize those with the best chance of achieving acceptable permeability and solubility. 相似文献
3.
Isabel Fernandes Cecília Melo-Alvim Raquel Lopes-Brs Miguel Esperana-Martins Luís Costa 《International journal of molecular sciences》2021,22(2)
Osteosarcoma (OS) is a rare condition with very poor prognosis in a metastatic setting. Basic research has enabled a better understanding of OS pathogenesis and the discovery of new potential therapeutic targets. Phase I and II clinical trials are already ongoing, with some promising results for these patients. This article reviews OS pathogenesis and new potential therapeutic targets. 相似文献
4.
5.
6.
Gomes A. C. S. A. Costa L. C. Brito D. C. Frana R. J. Marques Mnica R. C. 《Polymer Bulletin》2020,77(4):1969-1981
Polymer Bulletin - In this study, we synthesized a new ion-imprinted polymer (IIP) based on introduction of amidoxime groups in acrylonitrile, complexation with Cd2+ ions and polymerization with... 相似文献
7.
Bianka Rocha Saraiva Lucas Henrique Maldonado da Silva Fernando Antônio Anjo Ana Carolina Pelaes Vital Jéssica Bassi Da Silva Marcos Luciano Bruschi Paula Toshimi Matumoto Pintro 《International Journal of Food Science & Technology》2020,55(5):1962-1970
Debittered trub (brewing waste) is an important source of protein source (70.26%). Trub and whey protein were used for 5% protein enrichment of ice cream frozen by liquid nitrogen. Three formulations were elaborated: ice cream standard (ICS), ice cream with whey protein (ICW) and ice cream with trub (ICT). Chemical composition, rheological properties, texture, overrun, melting rate, scanning electron microscopy and a sensorial test were performed. Results showed that ICT presented a higher viscosity, obtained on the upward curve up to 6.76 Pa s−1, consistency index (22.96 (Pa s−1)n), hysteresis area (140.40 mPa s−1) and hardness (31113.33 g) but a lower melting rate (0.38 g min−1), overrun (13.92%) and sensorial acceptability than the other formulations. The addition of trub debittered for protein enrichment improved ice cream properties and demonstrated that it could be used as a food ingredient. 相似文献
8.
Number entry is a ubiquitous activity and is often performed in safety- and mission-critical procedures, such as healthcare, science, finance, aviation and in many other areas. We show that Monte Carlo methods can quickly and easily compare the reliability of different number entry systems. A surprising finding is that many common, widely used systems are defective, and induce unnecessary human error. We show that Monte Carlo methods enable designers to explore the implications of normal and unexpected operator behaviour, and to design systems to be more resilient to use error. We demonstrate novel designs with improved resilience, implying that the common problems identified and the errors they induce are avoidable. 相似文献
9.
Adaptive backstepping repetitive learning control design for nonlinear discrete‐time systems with periodic uncertainties 下载免费PDF全文
Qiao Zhu Jian‐Xin Xu Shiping Yang Guang‐Da Hu 《International Journal of Adaptive Control and Signal Processing》2015,29(4):524-535
This paper addresses a tracking problem for uncertain nonlinear discrete‐time systems in which the uncertainties, including parametric uncertainty and external disturbance, are periodic with known periodicity. Repetitive learning control (RLC) is an effective tool to deal with periodic unknown components. By using the backstepping procedures, an adaptive RLC law with periodic parameter estimation is designed. The overparameterization problem is overcome by postponing the parameter estimation to the last backstepping step, which could not be easily solved in robust adaptive control. It is shown that the proposed adaptive RLC law without overparameterization can guarantee the perfect tracking and boundedness of the states of the whole closed‐loop systems in presence of periodic uncertainties. In addition, the effectiveness of the developed controller is demonstrated by an implementation example on a single‐link flexible‐joint robot. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
10.
ABSTRACT The concept of digital game-based learning (DGBL) evolves rapidly together with technological enhancements of virtual reality (VR) and smart phones. However, the mental workload (MWL) that VR-training applications demand and motivational qualities originating from user experience (UX) should be identified in order to create effective and enjoyable training/learning challenges that fit with individual users’ capabilities. This study examined the effects of reality-based interaction (RBI) and VR on measures of student motivation and MWL, in a mental arithmetic game for secondary school pupils. In a randomised controlled trial with sixty school children, a mental arithmetic game was tested with three different interaction and two different presentation methods – VR RBI, VR head-mounted-display tapping and tablet flick-gesture. Results found a significant effect of RBI on MWL but no differences in enjoyment of training were found between VR-experience and tablet training-experience. In fact, adding the gaming-context to the mental arithmetic task created an enjoyable, motivating experience regardless of presentation or interaction-style. 相似文献