全文获取类型
收费全文 | 271161篇 |
免费 | 2527篇 |
国内免费 | 685篇 |
专业分类
电工技术 | 5785篇 |
综合类 | 205篇 |
化学工业 | 35788篇 |
金属工艺 | 13969篇 |
机械仪表 | 11225篇 |
建筑科学 | 5327篇 |
矿业工程 | 1488篇 |
能源动力 | 5274篇 |
轻工业 | 15507篇 |
水利工程 | 2783篇 |
石油天然气 | 4194篇 |
武器工业 | 7篇 |
无线电 | 34192篇 |
一般工业技术 | 56704篇 |
冶金工业 | 51099篇 |
原子能技术 | 4617篇 |
自动化技术 | 26209篇 |
出版年
2021年 | 1244篇 |
2019年 | 1281篇 |
2018年 | 10650篇 |
2017年 | 11208篇 |
2016年 | 6924篇 |
2015年 | 2033篇 |
2014年 | 2706篇 |
2013年 | 8002篇 |
2012年 | 7056篇 |
2011年 | 14428篇 |
2010年 | 12982篇 |
2009年 | 12553篇 |
2008年 | 12752篇 |
2007年 | 14798篇 |
2006年 | 5705篇 |
2005年 | 8925篇 |
2004年 | 7247篇 |
2003年 | 6718篇 |
2002年 | 5528篇 |
2001年 | 5372篇 |
2000年 | 5044篇 |
1999年 | 5454篇 |
1998年 | 15621篇 |
1997年 | 10313篇 |
1996年 | 7943篇 |
1995年 | 5792篇 |
1994年 | 5040篇 |
1993年 | 5043篇 |
1992年 | 3400篇 |
1991年 | 3282篇 |
1990年 | 3216篇 |
1989年 | 3039篇 |
1988年 | 2789篇 |
1987年 | 2234篇 |
1986年 | 2301篇 |
1985年 | 2606篇 |
1984年 | 2312篇 |
1983年 | 2063篇 |
1982年 | 1901篇 |
1981年 | 2043篇 |
1980年 | 1790篇 |
1979年 | 1659篇 |
1978年 | 1656篇 |
1977年 | 2021篇 |
1976年 | 2702篇 |
1975年 | 1422篇 |
1974年 | 1369篇 |
1973年 | 1316篇 |
1972年 | 1124篇 |
1971年 | 956篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
P. Carrasqueira H. Rocha J. M. Dias T. Ventura B. C. Ferreira M. C. Lopes 《International Transactions in Operational Research》2023,30(1):206-223
Radiation therapy is a technology-driven cancer treatment modality that has experienced significant advances over the last decades, due to multidisciplinary contributions that include engineering and computing. Recent technological developments allow the use of noncoplanar volumetric modulated arc therapy (VMAT), one of the most recent photon treatment techniques, in clinical practice. In this work, an automated noncoplanar arc trajectory optimization framework designed in two modular phases is presented. First, a noncoplanar beam angle optimization algorithm is used to obtain a set of noncoplanar irradiation directions. Then, anchored in these directions, an optimization strategy is proposed to compute an optimal arc trajectory. The computational experiments considered a pool of twelve difficult head-and-neck tumor cases. It was possible to observe that, for some of these cases, the optimized noncoplanar arc trajectories led to significant treatment planning quality improvements, when compared with coplanar VMAT treatment plans. Although these experiments were done in a research environment treatment planning software (matRad), the conclusions can be of interest for a clinical setting: automated procedures can simplify the current treatment workflow, produce high-quality treatment plans, making better use of human resources and allowing for unbiased comparisons between different treatment techniques. 相似文献
62.
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
63.
64.
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
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.
A. A. Babenko V. I. Zhuchkov L. A. Smirnov A. V. Sychev A. A. Akberdin A. S. Kim M. F. Vitushchenko A. A. Dobromilov 《Steel in Translation》2015,45(11):883-886
A technology for slag formation in the ladle–furnace unit is considered; the slag is based on the CaO–SiO2–MgO–Al2O3–B2O3 system. This technology permits both microalloying of the steel with boron (reduced from the oxide phase) and desulfurization of the steel. The resulting boron content in the steel is 0.001–0.008%; the sulfur content in low-alloy steel and pipe steel is low (0.004–0.010%); and the consumption of manganese ferroalloys is reduced to 0.5 kg/t for 08кп steel and 1.4 kg/t for 09Г2C steel. In addition, the proposed technology increases the strength of the rolled steel, without loss in its plasticity; and reduces the environmental impact thanks to the replacement of fluorspar by colemanite. 相似文献
68.
69.
70.
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