全文获取类型
收费全文 | 60211篇 |
免费 | 5374篇 |
国内免费 | 3076篇 |
专业分类
电工技术 | 3928篇 |
技术理论 | 4篇 |
综合类 | 4320篇 |
化学工业 | 9855篇 |
金属工艺 | 3395篇 |
机械仪表 | 3957篇 |
建筑科学 | 4532篇 |
矿业工程 | 1312篇 |
能源动力 | 1707篇 |
轻工业 | 4422篇 |
水利工程 | 1193篇 |
石油天然气 | 2640篇 |
武器工业 | 484篇 |
无线电 | 7712篇 |
一般工业技术 | 7823篇 |
冶金工业 | 2444篇 |
原子能技术 | 767篇 |
自动化技术 | 8166篇 |
出版年
2024年 | 240篇 |
2023年 | 880篇 |
2022年 | 1685篇 |
2021年 | 2376篇 |
2020年 | 1714篇 |
2019年 | 1543篇 |
2018年 | 1632篇 |
2017年 | 1840篇 |
2016年 | 1849篇 |
2015年 | 2488篇 |
2014年 | 2992篇 |
2013年 | 3659篇 |
2012年 | 3917篇 |
2011年 | 4328篇 |
2010年 | 3904篇 |
2009年 | 3571篇 |
2008年 | 3587篇 |
2007年 | 3311篇 |
2006年 | 3289篇 |
2005年 | 2838篇 |
2004年 | 2105篇 |
2003年 | 2006篇 |
2002年 | 2278篇 |
2001年 | 1901篇 |
2000年 | 1527篇 |
1999年 | 1323篇 |
1998年 | 1068篇 |
1997年 | 885篇 |
1996年 | 803篇 |
1995年 | 705篇 |
1994年 | 591篇 |
1993年 | 451篇 |
1992年 | 328篇 |
1991年 | 262篇 |
1990年 | 192篇 |
1989年 | 151篇 |
1988年 | 129篇 |
1987年 | 74篇 |
1986年 | 58篇 |
1985年 | 41篇 |
1984年 | 31篇 |
1983年 | 16篇 |
1982年 | 22篇 |
1981年 | 21篇 |
1980年 | 16篇 |
1979年 | 9篇 |
1976年 | 8篇 |
1975年 | 7篇 |
1959年 | 4篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
11.
广东省大型工程建设中天然放射性核素引起的环境问题 总被引:2,自引:0,他引:2
本文介绍了广东省境内几个大型基本建设工程项目中天然放射性核素引起的环境问题及有关治理对策,并就今后类似建设项目的辐射环境保护工作提出了建议。 相似文献
12.
Min-Seok Park Vladislav P. Vislovskiy Jong-San Chang Yong-Gun Shul Jin S. Yoo Sang-Eon Park 《Catalysis Today》2003,87(1-4):205-212
Alumina-supported vanadium oxide, VOx/Al2O3, and binary vanadium–antimony oxides, VSbOx/Al2O3, have been tested in the ethylbenzene dehydrogenation with carbon dioxide and characterized by SBET, X-ray diffraction, X-ray photoelectron spectroscopy, hydrogen temperature-programmed reduction and CO2 pulse methods. VSbOx/Al2O3 exhibited enhanced catalytic activity and especially on-stream stability compared to VOx/Al2O3 catalyst. Incorporation of antimony into VOx/Al2O3 increased dispersion of active VOx species, enhanced redox properties of the systems and formed a new mixed vanadium–antimony oxide phase in the most catalytically efficient V0.43Sb0.57Ox/Al2O3 system. 相似文献
13.
A tennis novice watching a match for the first time might be surprised that the crowd erupts with cheers when a player wins one point, then barely applauds when he wins the next. The crowd is not necessarily fickle; some points are genuinely more important than others because a tennis match is hierarchically structured. One match consists of several sets. One set consists of several games. One game consists of several points. The match-winning point is the most important one. How can we make that importance visible? Our goal is to let a fan, a player, or a coach examine tennis data visually, extract the interesting parts, and jump from one item to another quickly and easily. The visualization tool should help parse the elements of a match. We developed an interactive system called TennisViewer to visualize the dynamic, tree-structured data representing a tennis match. It provides an interface for users to quickly explore tennis match information. The visualization tool reveals the overall structure of the match as well as the fine details in a single screen. It uses a 2D display of translucent layers, a design that contains elements of Tree-Maps and of the Visual Scheduler system, which was designed to help faculty and students identify mutually available (transparent) time slots when arranging group meetings. TennisViewer provides MagicLens filters to explore specialized views of the information and a time-varying display to animate all or part of a match 相似文献
14.
文中简要地介绍了一个具有分散采集信号,集中报警的安全报警器的设计,作者利用单片机的优点和功能,成功地设计了复盖地域大,既简单又灵活的报警器。 相似文献
15.
The humidity response characteristics of La doped BaTiO3 with different sintered densities and room temperature electrical conductivities were investigated using complex impedance measurement. The samples with low density and high resistivity showed the large and nearly linear sensitivity to the change of humidity. The impedance spectra of samples, when exposed to high humidity, can exhibit microstructure-related features, even though they do not give rise to a noticeable characteristic change when exposed to low humidity. The observed impedance patterns were dependent upon the density, and hence the oxidation kinetics of BaTiO3. 相似文献
16.
The modulation characteristics of first-order backscatter-induced crosstalk noise in a 2-D frequency-division-multiplexed fiber gyro system are analyzed and experimental results presented. The noise can be reduced from 5°/h to 0.2°/h (0.25 NEB) by proper choice of modulation depth and/or frequency 相似文献
17.
Jin B. Ong Osama K. Eyada PhD PE Abu S. Masud PhD PE 《Computers & Industrial Engineering》1989,17(1-4):85-89
This paper presents a Knowledge-based system (KBS) developed to allow users, who may not be knowledgeable about sensors, to select sensors suitable for their specific needs. The KBS runs on a micro-computer. The selection criteria are user specified and are based on the desired measurement parameters. The system output includes all of the operational and dimensional parameters of the recommended sensor, price, and vendor information. 相似文献
18.
19.
为使北京谱仪端盖族射计数器更好地工作在自猝灭流光SQS模式下,提高其能量分辨以及线性等指标,用Ar,CO2,Lsobutane三元工作气体对探测器的工作性能进行了仔细研究,找出了一适合于主雇地数器的工作气体,此外,还研究了异丁的纯度对探测器性能的影响。 相似文献
20.
The fabric and faces of threat, and the expediency and efficiency in the communication of threat, are examined with a threat appraisal model. This model is empirically tested on an ongoing communication challenge, the issuance of terror alerts by the United States' Department of Homeland Security (DHS), focusing on how threat is appraised by both the conservative and liberal audiences. Findings showed a shared view by the DHS and conservative audiences on the levels and nature of threats; liberal audiences thought otherwise. Though there appeared to be a consensus between the conservative and liberal audiences on the efficacy of threat communication, more internal consistency within DHS is needed to optimise its effectiveness. 相似文献