全文获取类型
收费全文 | 199067篇 |
免费 | 2448篇 |
国内免费 | 636篇 |
专业分类
电工技术 | 4072篇 |
综合类 | 126篇 |
化学工业 | 27020篇 |
金属工艺 | 7541篇 |
机械仪表 | 5482篇 |
建筑科学 | 4084篇 |
矿业工程 | 749篇 |
能源动力 | 4715篇 |
轻工业 | 14546篇 |
水利工程 | 1699篇 |
石油天然气 | 2850篇 |
武器工业 | 7篇 |
无线电 | 27533篇 |
一般工业技术 | 37658篇 |
冶金工业 | 45549篇 |
原子能技术 | 3570篇 |
自动化技术 | 14950篇 |
出版年
2021年 | 1334篇 |
2020年 | 997篇 |
2019年 | 1359篇 |
2018年 | 2186篇 |
2017年 | 2172篇 |
2016年 | 2273篇 |
2015年 | 1538篇 |
2014年 | 2689篇 |
2013年 | 8047篇 |
2012年 | 4546篇 |
2011年 | 6195篇 |
2010年 | 5005篇 |
2009年 | 5827篇 |
2008年 | 6209篇 |
2007年 | 6238篇 |
2006年 | 5666篇 |
2005年 | 5341篇 |
2004年 | 5270篇 |
2003年 | 5103篇 |
2002年 | 4923篇 |
2001年 | 5321篇 |
2000年 | 4931篇 |
1999年 | 5448篇 |
1998年 | 15673篇 |
1997年 | 10349篇 |
1996年 | 7943篇 |
1995年 | 5799篇 |
1994年 | 5024篇 |
1993年 | 5034篇 |
1992年 | 3397篇 |
1991年 | 3266篇 |
1990年 | 3227篇 |
1989年 | 3043篇 |
1988年 | 2789篇 |
1987年 | 2241篇 |
1986年 | 2306篇 |
1985年 | 2611篇 |
1984年 | 2317篇 |
1983年 | 2071篇 |
1982年 | 1913篇 |
1981年 | 2048篇 |
1980年 | 1790篇 |
1979年 | 1666篇 |
1978年 | 1661篇 |
1977年 | 2026篇 |
1976年 | 2705篇 |
1975年 | 1423篇 |
1974年 | 1370篇 |
1973年 | 1318篇 |
1972年 | 1126篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
Tolmachev A. M. Kuznetsova T. A. Fomenkov P. E. 《Protection of Metals and Physical Chemistry of Surfaces》2021,57(3):433-436
Protection of Metals and Physical Chemistry of Surfaces - The conditions for carrying out molecular dynamics calculations of adsorption isotherms of gases and vapors in micropores of active carbons... 相似文献
62.
63.
Kozhitov L. V. Kiselev B. G. Raykova T. B. Popkova A. V. Kostishin V. G. Muratov D. G. Yakushko E. V. Kosushkin V. G. Bebenin V. G. 《Russian Microelectronics》2019,48(8):599-612
Russian Microelectronics - The recently developed nanomaterials and their production technologies as intellectual property objects (IPOs) are considered. The role of the informational-analytical... 相似文献
64.
Anh Tuan Thanh Pham Oanh Kieu Truong Le Dung Van Hoang Truong Huu Nguyen Trang Huyen Cao Pham Phuong Thanh Ngoc Vo Thang Bach Phan Vinh Cao Tran 《Journal of the European Ceramic Society》2021,41(6):3493-3500
Structure modification has been found to tune significantly the transparent-conducting performance, especially mobility and conductivity of hydrogenated Ga-doped ZnO (HGZO) films. The strong correlation between film thickness and mobility of the films is revealed. The mobility increases quickly with increasing the thickness from 350 to 900 nm, and then tends to be saturated at further thicknesses. A higher mobility than 50 cm2/Vs can be achieved, which is an extra-high value for polycrystalline ZnO films deposited by using the sputtering technique. The thickness-dependent mobility originates from scatterings on grain boundaries and dislocation-induced defects controlled by thin-film growth. Based on the Volmer-Weber model, an expansion model is built up to describe the thickness-dependent crystal growth of the HGZO films, especially at the thick films. As a result, the 800 nm-thick HGZO film obtains the highest performance with high mobility of 51.5 cm2/Vs, low resistivity of 5.3 × 10?4 Ωcm, and good transmittance of 83.3 %. 相似文献
65.
Geetha R. Madhusudhan V. Padmavathy T. Lallithasree A. 《Wireless Personal Communications》2019,108(3):1957-1976
Wireless Personal Communications - The majority of security systems for wireless sensor networks are based on symmetric encryption. The main open issue for these approaches concerns the... 相似文献
66.
67.
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
68.
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
69.
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
70.