全文获取类型
收费全文 | 500681篇 |
免费 | 8305篇 |
国内免费 | 1874篇 |
专业分类
电工技术 | 9248篇 |
技术理论 | 1篇 |
综合类 | 1026篇 |
化学工业 | 78581篇 |
金属工艺 | 20155篇 |
机械仪表 | 14741篇 |
建筑科学 | 12883篇 |
矿业工程 | 2114篇 |
能源动力 | 11852篇 |
轻工业 | 50883篇 |
水利工程 | 4560篇 |
石油天然气 | 6904篇 |
武器工业 | 91篇 |
无线电 | 55210篇 |
一般工业技术 | 91886篇 |
冶金工业 | 99345篇 |
原子能技术 | 9336篇 |
自动化技术 | 42044篇 |
出版年
2021年 | 4665篇 |
2020年 | 3420篇 |
2019年 | 4186篇 |
2018年 | 7233篇 |
2017年 | 7098篇 |
2016年 | 7655篇 |
2015年 | 5282篇 |
2014年 | 8462篇 |
2013年 | 23174篇 |
2012年 | 13658篇 |
2011年 | 17836篇 |
2010年 | 14244篇 |
2009年 | 15357篇 |
2008年 | 16395篇 |
2007年 | 16367篇 |
2006年 | 14610篇 |
2005年 | 12986篇 |
2004年 | 12383篇 |
2003年 | 12082篇 |
2002年 | 12051篇 |
2001年 | 11704篇 |
2000年 | 11039篇 |
1999年 | 11684篇 |
1998年 | 30136篇 |
1997年 | 20940篇 |
1996年 | 16004篇 |
1995年 | 12028篇 |
1994年 | 10652篇 |
1993年 | 10331篇 |
1992年 | 7443篇 |
1991年 | 7163篇 |
1990年 | 6973篇 |
1989年 | 6751篇 |
1988年 | 6531篇 |
1987年 | 5604篇 |
1986年 | 5592篇 |
1985年 | 6569篇 |
1984年 | 6043篇 |
1983年 | 5428篇 |
1982年 | 5120篇 |
1981年 | 5205篇 |
1980年 | 4980篇 |
1979年 | 4714篇 |
1978年 | 4736篇 |
1977年 | 5615篇 |
1976年 | 7916篇 |
1975年 | 4099篇 |
1974年 | 3850篇 |
1973年 | 3969篇 |
1972年 | 3295篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
Luca Pietrobon Lorenzo Fallarino Andreas Berger Andrey Chuvilin Flix Casanova Luis E. Hueso 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(47):6295-6301
Graphene has been predicted to develop a magnetic moment by proximity effect when placed on a ferromagnetic film, a promise that could open exciting possibilities in the fields of spintronics and magnetic data recording. In this work, the interplay between the magnetoresistance of graphene and the magnetization of an underlying ferromagnetic insulating film is studied in detail. A clear correlation between both magnitudes is observed but through a careful modeling of the magnetization and the weak localization measurements, that such correspondence can be explained by the effects of the magnetic stray fields arising from the ferromagnetic insulator is found. The results emphasize the complexity arising at the interface between magnetic and 2D materials. 相似文献
62.
Valence M. K. Ndesendo Yahya E. Choonara Leith C. R. Meyer Pradeep Kumar Lomas K. Tomar Charu Tyagi 《Drug development and industrial pharmacy》2015,41(8):1274-1287
Context and objective: The aim of this study was to develop, characterize and evaluate a mucoadhesive caplet resulting from a polymeric blend (polymeric caplet) for intravaginal anti-HIV-1 delivery.Materials and methods: Poly(lactic-co-glycolic) acid, ethylcellulose, poly(vinylalcohol), polyacrylic acid and modified polyamide 6, 10 polymers were blended and compressed to a caplet-shaped device, with and without two model drugs 3′-azido-3′-deoxythymidine (AZT) and polystyrene sulfonate (PSS). Thermal analysis, infrared spectroscopy and microscopic analysis were carried out on the caplets employing temperature-modulated DSC (TMDSC), Fourier transform infra-red (FTIR) spectrometer and scanning electron microscope, respectively. In vitro and in vivo drug release analyses as well as the histopathological toxicity studies were carried out on the drug-loaded caplets. Furthermore, molecular mechanics (MM) simulations were carried out on the drug-loaded caplets to corroborate the experimental findings.Results and discussion: There was a big deviation between the Tg of the polymeric caplet from the Tg's of the constituent polymers indicating a strong interaction between constituent polymers. FTIR spectroscopy confirmed the presence of specific ionic and non-ionic interactions within the caplet. A controlled near zero-order drug release was obtained for AZT (20 d) and PSS (28 d). In vivo results, i.e. the drug concentration in plasma ranged between 0.012–0.332?mg/mL and 0.009–0.256?mg/mL for AZT and PSS over 1–28 d.Conclusion: The obtained results, which were corroborated by MM simulations, attested that the developed system has the potential for effective delivery of anti-HIV-agents. 相似文献
63.
64.
65.
Lecture capture with real‐time rearrangement of visual elements: impact on student performance 下载免费PDF全文
The primary goal of this study is to create and test a lecture‐capture system that can rearrange visual elements while recording is still taking place, in such a way that student performance can be positively influenced. The system we have devised is capable of integrating and rearranging multimedia sources, including learning content, the instructor and students' images, into lecture videos that are embedded in a website for students to review after school. The present study employed a two‐group experimental design, with 153 participants (145 females and 8 males) making up an experimental group in which lecture courses were recorded using the new lecture‐capture system, and 149 participants (140 females and 9 males) forming a control group whose lectures were recorded by traditional means. All participants were in the freshman college and studying Introduction to Computer and Information Science in one of six classes, and were randomly assigned to one of the two groups. The participants' midterm examination and final examination scores were collected as indicators of their academic performance, with their mathematics entrance scores used as a pre‐test. The findings obtained from analysis of covariance (ANCOVA) suggest that appropriate rearrangement of visual elements in lecture videos can significantly impact students' learning performance. 相似文献
66.
Buryakov A. M. Khusyainov D. I. Mishina E. D. Khabibullin R. A. Yachmenev A. E. Ponomarev D. S. 《Technical Physics Letters》2018,44(12):1115-1119
Technical Physics Letters - The influence of excitation photons energy on the relaxation times of photoexcited carriers is studied. The involved relaxation mechanisms are evaluated and the... 相似文献
67.
This study presents a back-analysis of geotechnical parameters on prefabricated vertical drain improved ground at a site in the Mekong Delta. Various time?settlement behaviors that reflected different clay thicknesses and loading patterns were observed. The total surface settlement behavior at several monitoring locations was simulated using an updated exponential method that considered staged construction. The analyzed results were validated by substituting the values into a theoretical solution for radial consolidation. The estimated theoretical behaviors were comparable with the monitored behaviors. The geotechnical parameters were back-analyzed by applying the previously analyzed results to various theoretical and empirical formulas. However, the use of extensometer data that were installed at large intervals produced different values of the geotechnical properties. Furthermore, finite element analysis supported the back-analyzed total settlement behaviors and nearly disregarded the application of the geotechnical properties that were obtained using either surface or subsurface settlement data. However, settlements and excess pore pressures in the sublayers were not successfully predicted even when the geotechnical properties were adjusted. Thus, subsurface instruments that can be installed closely in thick clay deposits are required to reliably reevaluate the variations in geotechnical properties along a certain depth. 相似文献
68.
69.
70.