全文获取类型
收费全文 | 7606篇 |
免费 | 408篇 |
国内免费 | 14篇 |
专业分类
电工技术 | 83篇 |
综合类 | 2篇 |
化学工业 | 1873篇 |
金属工艺 | 174篇 |
机械仪表 | 146篇 |
建筑科学 | 280篇 |
矿业工程 | 13篇 |
能源动力 | 245篇 |
轻工业 | 707篇 |
水利工程 | 75篇 |
石油天然气 | 28篇 |
武器工业 | 6篇 |
无线电 | 563篇 |
一般工业技术 | 1573篇 |
冶金工业 | 841篇 |
原子能技术 | 43篇 |
自动化技术 | 1376篇 |
出版年
2023年 | 56篇 |
2022年 | 121篇 |
2021年 | 167篇 |
2020年 | 160篇 |
2019年 | 134篇 |
2018年 | 180篇 |
2017年 | 198篇 |
2016年 | 252篇 |
2015年 | 167篇 |
2014年 | 270篇 |
2013年 | 604篇 |
2012年 | 450篇 |
2011年 | 545篇 |
2010年 | 368篇 |
2009年 | 370篇 |
2008年 | 502篇 |
2007年 | 425篇 |
2006年 | 369篇 |
2005年 | 304篇 |
2004年 | 281篇 |
2003年 | 245篇 |
2002年 | 201篇 |
2001年 | 123篇 |
2000年 | 101篇 |
1999年 | 115篇 |
1998年 | 120篇 |
1997年 | 103篇 |
1996年 | 102篇 |
1995年 | 92篇 |
1994年 | 108篇 |
1993年 | 78篇 |
1992年 | 63篇 |
1991年 | 51篇 |
1990年 | 46篇 |
1989年 | 63篇 |
1988年 | 47篇 |
1987年 | 24篇 |
1986年 | 31篇 |
1985年 | 40篇 |
1984年 | 40篇 |
1983年 | 26篇 |
1982年 | 26篇 |
1981年 | 41篇 |
1980年 | 24篇 |
1979年 | 22篇 |
1978年 | 24篇 |
1977年 | 14篇 |
1975年 | 11篇 |
1974年 | 22篇 |
1973年 | 14篇 |
排序方式: 共有8028条查询结果,搜索用时 15 毫秒
21.
Arun Chandrasekhar Steven Brebels Serguei Stoukatch Eric Beyne Walter De Raedt Bart Nauwelaers 《Microelectronics Reliability》2003,43(3):351-357
At frequencies beyond 1 GHz, every component of the IC package contributes to the RF performance, whether required or not. In this work, we study the effects of packaging materials namely, the substrate and the globtop/underfill material on RF performance. We have measured interconnects on two area-array CSPs, the ball grid array and the polymer stud grid array using IMEC’s MCM-D technology. The measurements on the package interconnect show that the losses in the package substrate material account for about 50% of the total losses at 1.8 GHz and this drops to less than 20% at 5.2 GHz. The losses due to impedance mismatch dominate the losses especially below 10 GHz and considerable improvement in performance cannot be obtained by using an improved/expensive substrate. The other study is about the influence of globtop/underfill materials on wirebonds (through 3D EM simulations) as well as on standard 50 Ω MCM-D transmission lines (through experiments). While a higher value of dielectric constant of the globtop/underfill material is better on wirebonds, the influence of loss tangent is felt only above values of 0.1. The influence of seven different globtop/undefill materials on 50 Ω transmission lines has been used to extract their dielectric constant and loss tangent values at 30 GHz. These results are very valuable since one can hardly find the properties of globtop/underfill materials beyond 1 GHz. 相似文献
22.
23.
24.
This paper presents a new massively parallel MIMD architecture, halfway between the Connection Machine and hypercubes based on 32-bit processors. It is built from specific 8-bit processors arranged in a 2-D grid and communicating by message transfers. We discuss the communication problems, the instruction set of the basic processing unit, the programmation of the whole array and the use of a high level data-flow language. 相似文献
25.
26.
27.
According to D. E. Broadbent's (1958) selective filter theory, people do not process unattended stimuli beyond the analysis of basic physical properties. This theory was later rejected on the basis of numerous findings that people identify irrelevant (and supposedly unattended) stimuli. A careful review of this evidence, however, reveals strong reasons to doubt that these irrelevant stimuli were in fact unattended. This review exposed a clear need for new experiments with tight control over the locus of attention. The authors present 5 such experiments using a priming paradigm. When steps were taken to ensure that irrelevant stimuli were not attended, these stimuli produced no priming effects. Hence, the authors found no evidence that unattended stimuli can be identified. The results support a modern version of Broadbent's selective theory, updated to reflect recent research advances. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
28.
The purpose of this study was to examine predictors and consequences of spouses' involvement in each others' strategies for pursuing important personal goals called life tasks. Husbands and wives within 39 short- and long-term marriages described five life tasks and provided appraisals of whether each was shared with their spouse. Participants later completed 14 consecutive diary entries recording daily life task pursuit strategies, the extent of spouse involvement in each, and measures of positive and negative affect. Results indicated that interdependence in life task appraisals prospectively predicted greater spouse involvement, and greater spouse involvement was associated with more positive affect for that day. Life task appraisals may provide avenues for understanding couples' strategies for dealing with goals or stressors and how those strategies affect mood. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
29.
Christophe Lombard Stephane Le Doze Eric Marencak Paul-Marie Marquaire David Le Noc Grégory Bertrand François Lapicque 《International Journal of Hydrogen Energy》2006
The paper reports the results of on-site regeneration catalytic bed of the natural gas reformer in a 5 kW PEM fuel cell system. The Ni catalyst previously poisoned by sulphur from the available natural gas, could be re-activated by injection of pure water steam, following the method developed for industrial reformers using the same metal catalyst: this method was shown to be perfectly efficient, provided no natural gas was fed during the operation. Results of the tests conducted are presented and discussed in relation to published data on S-sorption on Ni surfaces. 相似文献
30.
Outlines an approach to epidemiologic-type life-stress studies that involves the intensive study of smaller groups of well-defined disordered individuals across the course of the response. On the basis of their previous research, the authors suggest that cyclothymia may be characterized by poor regulation of biologic and behavioral variation and that this condition may be exaggerated by stress. To extend the evidence on poor regulation generated in laboratory studies of cortisol functioning, 31 cyclothyme patients and 24 normal controls (median age 19.3 yrs) were asked to provide daily ratings of moods and events over 28 consecutive days. Data show that Ss with cyclothymia showed prolonged duration of recovery of behavioral levels compared to controls. Findings support a notion of weak inhibitory modulation in certain CNS systems that control biologic and behavioral variables related to affective disorder. It is suggested that the prolonged duration of behavioral change in cyclothymia is unlikely to be the consequence of concurrent depression and that the nature of prolonged recovery to stress in cyclothymia reflects the operation of an endogenous regulatory process, as opposed to a cognitive appraisal bias. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献