全文获取类型
收费全文 | 516156篇 |
免费 | 5662篇 |
国内免费 | 1401篇 |
专业分类
电工技术 | 9853篇 |
综合类 | 345篇 |
化学工业 | 74520篇 |
金属工艺 | 23479篇 |
机械仪表 | 17806篇 |
建筑科学 | 11441篇 |
矿业工程 | 3036篇 |
能源动力 | 11316篇 |
轻工业 | 38686篇 |
水利工程 | 5459篇 |
石油天然气 | 10132篇 |
武器工业 | 23篇 |
无线电 | 60547篇 |
一般工业技术 | 104159篇 |
冶金工业 | 96533篇 |
原子能技术 | 11080篇 |
自动化技术 | 44804篇 |
出版年
2021年 | 3122篇 |
2019年 | 3032篇 |
2018年 | 12476篇 |
2017年 | 12844篇 |
2016年 | 9677篇 |
2015年 | 4170篇 |
2014年 | 6447篇 |
2013年 | 18896篇 |
2012年 | 12664篇 |
2011年 | 21230篇 |
2010年 | 18338篇 |
2009年 | 19028篇 |
2008年 | 19533篇 |
2007年 | 21126篇 |
2006年 | 12667篇 |
2005年 | 14675篇 |
2004年 | 12896篇 |
2003年 | 12256篇 |
2002年 | 11288篇 |
2001年 | 11074篇 |
2000年 | 10446篇 |
1999年 | 10974篇 |
1998年 | 28815篇 |
1997年 | 20186篇 |
1996年 | 15549篇 |
1995年 | 11601篇 |
1994年 | 10302篇 |
1993年 | 10241篇 |
1992年 | 7366篇 |
1991年 | 7213篇 |
1990年 | 7027篇 |
1989年 | 6833篇 |
1988年 | 6567篇 |
1987年 | 5464篇 |
1986年 | 5538篇 |
1985年 | 6338篇 |
1984年 | 5911篇 |
1983年 | 5349篇 |
1982年 | 5030篇 |
1981年 | 5277篇 |
1980年 | 4935篇 |
1979年 | 4732篇 |
1978年 | 4782篇 |
1977年 | 5656篇 |
1976年 | 7429篇 |
1975年 | 4318篇 |
1974年 | 4145篇 |
1973年 | 4082篇 |
1972年 | 3567篇 |
1971年 | 3221篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
152.
Lecture capture with real‐time rearrangement of visual elements: impact on student performance
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)
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
153.
A. M. Mirzabaev V. P. Kanonerov T. A. Makhkamov O. R. Sytdykov Sh. M. Mirzabekov 《Applied Solar Energy》2018,54(3):224-226
The data on the use of solar photovoltaic plants (PVPs) for providing a reliable and guaranteed power supply to telecommunication systems and cellular communication systems in the conditions prevalent in Uzbekistan are given. The research-based structures developed by OOO MIR SOLAR and the selection of PVP elements ensuring their reliable operation are described. The main influencing factors are discussed, and the use of effective combinations of different types of panels (from monocrystalline and polycrystalline silicon) and a specially developed controller are considered. 相似文献
154.
Chitosan microspheres containing bromocresol green, cresol red, and phenolphthalein for corrosion detection, through pH change, are synthesized in order to be used in protective coatings for aluminium alloys. Microspheres containing corrosion detection species are characterized morphologically (SEM) and physico‐chemically (FTIR, TGA). Release studies (UV–vis) are performed in corrosion‐promoting conditions (pH, NaCl), and detection studies by immersion in media associated with corrosion activity while microspheres' sensing activity is evaluated visually. Electrochemical characterization of AA2024 substrates in the presence of chitosan spheres is performed to understand material performance, and a color change is observed as a result of local pH increase in cathodic areas when corrosion takes place. These findings can be correlated with the results from release studies and seem a promising approach for corrosion sensing purposes, not only because pH increase is possible to detect due to corrosion, but also because chitosan is considered an environmentally friendly material. 相似文献
155.
Arif Karademir Cem Aydemir Semiha Yenidogan Emine Arman Kandırmaz Rukiye G. Kıter 《Color research and application》2020,45(6):1170-1178
Alkyd resins are generally used in the production of printing inks. All industries look for alternative raw materials in the production of ink with the growing inclination toward using natural products. Resins forming the vehicle of the ink to be obtained from natural resources will provide benefits for the environment, nature, and living creatures. The aim of the study was to promote the use of natural resin in the ink system. Natural Pinus pinaster resin was added into vegetable and mineral oil-based solvents in pure form with alkyd resin in different amounts and ink varnishes of different combinations were prepared. Then, printing inks were produced from these varnishes in pure and hybrid form. Following the assessment of the rheological properties of the inks prepared, printing tests were conducted to assess the printing quality parameters. Ideal mixing ratios of the natural resins in the ink were determined for printability. The environmental importance and advantages of the use of natural resins were discussed. Recommendations were given in line with the results to encourage widespread use of natural resins in near future. 相似文献
156.
D. M. Mukhammadiev F. Kh. Ibragimov T. D. Mukhammadiev 《Journal of Machinery Manufacture and Reliability》2020,49(3):256-262
The dynamic characteristics of a saw gin as a subsystem with lumped and distributed parameters are considered in the paper. On the basis of investigation of the machine assembly, graphs are drawn that allow establishing the maximum values of the angle of relative rotation and the angle of rotation of the saw cylinder shaft under torsion. 相似文献
157.
C. G. Prosgolitis S. G. Lambrakos A. D. Zervaki 《Journal of Materials Engineering and Performance》2018,27(10):5102-5113
This work presents simulation of microstructure evolution in the nugget zone (NZ) of a AZ31-Mg-alloy friction stir weld. The process parameters (tool geometrical characteristics, rotational speed, travel speed, applied load) have been correlated with the resulting microstructural features in the NZ of the weld (grain size and population) with the aid of the MICRESS software, which provides the ability to simulate both nucleation and grain growth during dynamic recrystallization phenomena evolving in the NZ during the weld thermal cycle. The input parameters of the developed model include the tool geometry, the welding conditions as well as the recrystallization energy, the grain boundary mobility and specific material properties. NZ microstructure obtained by simulation shows good agreement with experimental measurements for both grain population and size. 相似文献
158.
159.
160.