全文获取类型
收费全文 | 9208篇 |
免费 | 1034篇 |
国内免费 | 484篇 |
专业分类
电工技术 | 1021篇 |
综合类 | 1053篇 |
化学工业 | 436篇 |
金属工艺 | 252篇 |
机械仪表 | 819篇 |
建筑科学 | 204篇 |
矿业工程 | 169篇 |
能源动力 | 107篇 |
轻工业 | 133篇 |
水利工程 | 51篇 |
石油天然气 | 297篇 |
武器工业 | 209篇 |
无线电 | 3647篇 |
一般工业技术 | 653篇 |
冶金工业 | 449篇 |
原子能技术 | 72篇 |
自动化技术 | 1154篇 |
出版年
2024年 | 42篇 |
2023年 | 145篇 |
2022年 | 222篇 |
2021年 | 274篇 |
2020年 | 265篇 |
2019年 | 222篇 |
2018年 | 237篇 |
2017年 | 325篇 |
2016年 | 374篇 |
2015年 | 379篇 |
2014年 | 579篇 |
2013年 | 560篇 |
2012年 | 727篇 |
2011年 | 720篇 |
2010年 | 554篇 |
2009年 | 577篇 |
2008年 | 528篇 |
2007年 | 675篇 |
2006年 | 506篇 |
2005年 | 477篇 |
2004年 | 379篇 |
2003年 | 377篇 |
2002年 | 294篇 |
2001年 | 251篇 |
2000年 | 210篇 |
1999年 | 160篇 |
1998年 | 116篇 |
1997年 | 90篇 |
1996年 | 97篇 |
1995年 | 84篇 |
1994年 | 59篇 |
1993年 | 32篇 |
1992年 | 47篇 |
1991年 | 28篇 |
1990年 | 25篇 |
1989年 | 22篇 |
1988年 | 12篇 |
1987年 | 5篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 9篇 |
1983年 | 5篇 |
1982年 | 3篇 |
1980年 | 4篇 |
1966年 | 2篇 |
1965年 | 3篇 |
1964年 | 3篇 |
1959年 | 2篇 |
1955年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
介绍了基于自由载流子对介质折射率调制作用,而建立的监测半导体器件内自由载流子变化情况的实验装置,该装置能实时反映自由载流子变化情况,且对原电路无任何影响。本方法适用于硅和砷化镓材料的电子和光电子器件,也显示了在测量集成电路内部有源器件特性方面的潜在应用前景。 相似文献
63.
64.
65.
震源延迟叠加技术及应用效果 总被引:2,自引:0,他引:2
延迟叠加爆炸是针对高分辨率和深层地震勘探而提出来的一种激发方式。这种激发方式能在保证地震分辨率的前提下有效提高地震波能量 ,在地震波的入射角范围内 ,有效克服非球形炸药激发引起的地震波传播的方向性。应用弹性波动力学对多级延迟爆炸进行理论研究 ,结合实际试验资料 ,研究了延迟爆炸情况下激发参数对地震波能量、主频、频宽等的影响。从几何地震学出发 ,分析了不同时间激发的地震波在地下空间中的干涉情况 ,对其能量传播的方向性进行了研究。理论分析和试验效果表明 ,延迟叠加震源与相同药量的普通震源相比 ,激发地震波的主频高 ,频带宽 ,增强了下传能量 ,降低了次生干扰 ,在高分辨率和深层地震勘探中具有明显的优势。 相似文献
66.
电磁兼容是目前电子镇流器最需要解决的问题之一。介绍了电子镇流器产生的辐射干扰、传导干扰及电流谐波畸变干扰的形成和所造成的影响,分析了产生这些干扰的原因,并分别给出了抑制这些干扰的方法,最后就电子镇流器设计制造中的难点问题作了简要说明。 相似文献
67.
Evgenia Adamopoulou Konstantinos Demestichas Panagiotis Demestichas Michael Theologou 《International Journal of Communication Systems》2008,21(3):311-330
Cognitive radio systems dynamically reconfigure the algorithms and parameters they use, in order to adapt to the changing environment conditions. However, reaching proper reconfiguration decisions presupposes a way of knowing, with high enough assurance, the capabilities of the alternate configurations, especially in terms of achievable transmission capacity and coverage. The present paper addresses this problem, firstly, by specifying a complete process for extracting estimations of the capabilities of candidate configurations, in terms of transmission capacity and coverage, and, secondly, by enhancing these estimations with the employment of a machine learning technique. The technique is based on the use of Bayesian Networks, in conjunction with an effective learning and adaptation strategy, and aims at extracting and exploiting knowledge and experience, in order to reach robust (i.e. stable and reliable) estimations of the configurations' capabilities. Comprehensive results of the proposed method are presented, in order to validate its functionality. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
68.
The modality effect in immediate recall refers to superior recall of the last few items within lists presented in spoken as opposed to printed form. The locus of this well-known effect has been unclear. N. Cowan, J. S. Saults, E. M. Elliott, and M. Moreno (2002) introduced a new method to distinguish between the effects of input serial position, output serial position, and the number of items yet to be recalled and found that large modality effects occurred only in conditions in which delay and interference at output (from items already recalled) was high. The authors replicated that finding, even when the response period included output interference acoustically similar to the spoken stimuli to be recalled. However, the authors found that output delay and interference act only by lowering the level of performance to a more sensitive range. The modality effect thus originates during encoding of the list to be recalled, not during output. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
69.
Costa Albert; Kovacic Damir; Fedorenko Evelina; Caramazza Alfonso 《Canadian Metallurgical Quarterly》2003,29(6):1270
The authors report 3 picture-word interference experiments in which they explore some properties of the agreement process in speech production. In Experiment 1, Croatian speakers were asked to produce utterances in which the noun's gender value had an impact on the selection of gender-marked freestanding morphemes (pronouns) while ignoring the presentation of same- or different-gender distractor words. In Experiments 2 and 3, Croatian speakers were asked to name the same pictures using noun phrases in which the noun's gender value surfaced as an inflectional suffix. Different-gender distractors interfered more than same-gender distractors (the gender congruency effect) in Experiment 1, but not in Experiments 2 and 3. These contrasting results show that the cause of the gender congruency effect is not at the level where lexical-grammatical information is selected but at the level of selection of freestanding morphemes. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
70.
Pictures were shown with superimposed word distractors of high and low frequency. Low-frequency distractors produced greater interference on picture naming than did high-frequency distractors. This distractor frequency effect was not affected by manipulations that facilitated or hindered distractor recognition. Interference was reduced for distractors that were read aloud several times prior to being shown in the picture-naming task. Together these findings suggest that the distractor frequency effect has its locus at some stage of lexical access for production. Other findings further constrain hypotheses about which level of speech production is involved in the effect. The distractor frequency effect has implications for models of lexical processing in speaking as well as for accounts of picture-word interference and the frequency effect. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献