全文获取类型
收费全文 | 65025篇 |
免费 | 7543篇 |
国内免费 | 3915篇 |
专业分类
电工技术 | 11755篇 |
技术理论 | 2篇 |
综合类 | 6433篇 |
化学工业 | 4805篇 |
金属工艺 | 2302篇 |
机械仪表 | 4896篇 |
建筑科学 | 2703篇 |
矿业工程 | 1941篇 |
能源动力 | 2814篇 |
轻工业 | 1195篇 |
水利工程 | 1752篇 |
石油天然气 | 3220篇 |
武器工业 | 1171篇 |
无线电 | 15743篇 |
一般工业技术 | 5920篇 |
冶金工业 | 1835篇 |
原子能技术 | 686篇 |
自动化技术 | 7310篇 |
出版年
2024年 | 305篇 |
2023年 | 958篇 |
2022年 | 1528篇 |
2021年 | 1799篇 |
2020年 | 2037篇 |
2019年 | 1707篇 |
2018年 | 1684篇 |
2017年 | 2224篇 |
2016年 | 2564篇 |
2015年 | 2831篇 |
2014年 | 3944篇 |
2013年 | 3937篇 |
2012年 | 4821篇 |
2011年 | 5276篇 |
2010年 | 4035篇 |
2009年 | 3912篇 |
2008年 | 3951篇 |
2007年 | 4703篇 |
2006年 | 4186篇 |
2005年 | 3370篇 |
2004年 | 2753篇 |
2003年 | 2452篇 |
2002年 | 2065篇 |
2001年 | 1732篇 |
2000年 | 1409篇 |
1999年 | 1177篇 |
1998年 | 908篇 |
1997年 | 741篇 |
1996年 | 695篇 |
1995年 | 597篇 |
1994年 | 524篇 |
1993年 | 363篇 |
1992年 | 289篇 |
1991年 | 240篇 |
1990年 | 165篇 |
1989年 | 136篇 |
1988年 | 106篇 |
1987年 | 76篇 |
1986年 | 44篇 |
1985年 | 42篇 |
1984年 | 40篇 |
1983年 | 13篇 |
1982年 | 22篇 |
1981年 | 20篇 |
1980年 | 18篇 |
1979年 | 15篇 |
1977年 | 6篇 |
1975年 | 10篇 |
1959年 | 7篇 |
1951年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
21.
本文提出励磁电流可自动控制的他励式双高调速系统设计方案。系统在提升特别是在下放重物时,具有较硬的机械性;在负载10-100%的变化范围内,可实现最大偏差Δnmax/nmin100%≤10%,调速范围D≥10;在满载运行条件下,可节约电能80%以上。 相似文献
22.
采用高频脉冲电铸工艺制备出了镍钴纳米复合块体材料,利用场发射扫描电镜、能谱和X射线衍射的方法,重点研究了复合块体沉积层的表面形貌、相结构和结晶取向。结果表明.高频率和润湿剂的添加对沉积层的细化有重要影响,高频脉冲电铸能够获得微观组织致密、均匀的复合块体材料。 相似文献
23.
In various medium‐to‐large‐scale fire test equipments like the ISO room corner test (RC), and more recently, the single burning item test (SBI) the mass flow rate measurement of the combustion gases plays a key role in the determination of the heat‐release rate and smoke‐production rate. With the knowledge of the velocity profile and the temperature of the flow, the mass flow rate is obtained by measuring the velocity on the axis of the duct. This is done by means of a bi‐directional probe based on the pitot principle. However, due to the variation of the mean temperature and the temperature gradient in any cross section of the duct, introduced by ever changing combustion gas temperatures, the velocity nor the density profile are constant in time. This paper examines the resulting uncertainty on the mass flow rate. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
24.
The mirror effect for word frequency refers to the finding that low-frequency words have higher hit rates and lower false alarm rates than high-frequency words. This result is typically interpreted in terms of conventional signal detection theory (SDT), in which case it indicates that the order of the underlying old item distributions mirrors the order of the new item distributions. However, when viewed in terms of a mixture version of SDT, the order of hits and false alarms does not necessarily imply the same order in the underlying distributions because of possible effects of mixing. A reversal in underlying distributions did not appear for fits of mixture SDT models to data from 4 experiments. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
25.
多媒体业务对无线通信的带宽与品质提出了更高的要求,OFDM和MIMO由于满足了这一需求被越来越多的无线通信标准采用所为底层的调制和传输技术。频率同步问题是OFDM—MIMO物理层设计中正确解调的前提和基础,本文介绍了OFDM—MIMO的原理、特点和频率同步问题的研究现状。 相似文献
26.
David Mills 《Granular Matter》2004,6(2-3):173-177
For fine powdered materials, capable of being conveyed in dense phase, a conveying region exists in which instability in flow and pipeline blockage can occur if the pressure gradient available is insufficient to maintain a minimum value of solids loading ratio. A reduction in material flow rate can also lead to pipeline blockage in this region. Conveying trials under-taken with cement are used to illustrate the nature of the problem. 相似文献
27.
28.
29.
This study examines the ways in which therapists function as attachment figures for patients. Patients in long-term psychoanalytic therapy answered questionnaires about their feelings about their therapists and their closest personal relationships. Components of attachment prominent in the therapeutic relationships were looking up to the therapist and feeling the therapist was responsive to emotional needs. Stronger attachment to therapists was associated with greater frequency and duration of therapy, a stronger working alliance, and greater security of the patients' attachment style, as well as with the gender of the patient and therapist. Using attachment theory to understand psychoanalytic relationships emphasizes the unique importance of a therapist to a patient and can offer new perspectives on both therapeutic and attachment processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
30.