全文获取类型
收费全文 | 4025篇 |
免费 | 517篇 |
国内免费 | 336篇 |
专业分类
电工技术 | 631篇 |
综合类 | 263篇 |
化学工业 | 233篇 |
金属工艺 | 142篇 |
机械仪表 | 206篇 |
建筑科学 | 99篇 |
矿业工程 | 36篇 |
能源动力 | 60篇 |
轻工业 | 70篇 |
水利工程 | 38篇 |
石油天然气 | 39篇 |
武器工业 | 38篇 |
无线电 | 1200篇 |
一般工业技术 | 348篇 |
冶金工业 | 575篇 |
原子能技术 | 64篇 |
自动化技术 | 836篇 |
出版年
2024年 | 19篇 |
2023年 | 48篇 |
2022年 | 84篇 |
2021年 | 108篇 |
2020年 | 123篇 |
2019年 | 112篇 |
2018年 | 94篇 |
2017年 | 144篇 |
2016年 | 152篇 |
2015年 | 176篇 |
2014年 | 239篇 |
2013年 | 256篇 |
2012年 | 294篇 |
2011年 | 402篇 |
2010年 | 300篇 |
2009年 | 302篇 |
2008年 | 291篇 |
2007年 | 326篇 |
2006年 | 256篇 |
2005年 | 224篇 |
2004年 | 183篇 |
2003年 | 144篇 |
2002年 | 133篇 |
2001年 | 106篇 |
2000年 | 71篇 |
1999年 | 53篇 |
1998年 | 46篇 |
1997年 | 35篇 |
1996年 | 15篇 |
1995年 | 31篇 |
1994年 | 14篇 |
1993年 | 14篇 |
1992年 | 8篇 |
1991年 | 6篇 |
1990年 | 8篇 |
1989年 | 7篇 |
1988年 | 3篇 |
1987年 | 5篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1981年 | 2篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1973年 | 2篇 |
1966年 | 3篇 |
1964年 | 4篇 |
1963年 | 3篇 |
1959年 | 2篇 |
1956年 | 2篇 |
1955年 | 2篇 |
排序方式: 共有4878条查询结果,搜索用时 93 毫秒
11.
Transmission of signals, whether on-chip or off-chip, places severe constraints on timing and extracts a large price in energy. New silicon device technologies, such as back-plane CMOS, provide a programmable and adaptable threshold voltage as an additional tool that can be used for low power design. We show that one particularly desirable use of this freedom is energy-efficient high-speed transmission across long interconnects using multi-valued encoding. Our multi-valued CMOS circuits take advantage of the threshold voltage control of the transistors, by using the signal-voltage-to-threshold-voltage span, in order to make area-efficient implementations of 4-PAM (pulse amplitude modulation) transceivers operating at high speed. In a comparison of a variety of published technologies, for signal transmission with interconnects of 10-15 mm length, we show up to 50% improvement in energy for on-chip signal transmission over binary encoding together with higher limits for operating speeds without a penalty in circuit noise margin. 相似文献
12.
对时钟电路设计中的3个主要问题:阻抗、传输延迟以及容性负载分别进行了阐述、分析与计算,得出了能够改善时钟电路电磁兼容性(EMC)的设计方法,并通过实践得以证实。 相似文献
13.
Halo effects in rating specific pieces of work, as in educational grading, have received little attention. Grades awarded by 2 independent graders to undergraduate projects were analyzed with a correlated uniqueness model. Grades showed substantial halo despite being awarded by expert assessors at the time of reading the work. There was greater halo between different grades applying to the same section of the project than between grades applying to different sections. Supervisors who had regular contact with the student whose work they were grading showed no more halo than other graders. More reliable graders showed less within-section halo than graders of lower reliability but equal between-sections halo. The halo effects observed cannot be entirely attributable to a unitary general impression. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
14.
Dunn Barnaby D.; Dalgleish Tim; Lawrence Andrew D.; Ogilvie Alan D. 《Canadian Metallurgical Quarterly》2007,116(1):1
The accuracy with which dysphoric (Study 1) and clinically depressed (Study 2) individuals make self-regulatory judgments about their own performance in the absence of external feedback and the extent to which this relates to trait self-focused attention (SFA) were examined. Relative to objective criteria, both dysphoric and depressed participants showed a positive judgment bias, overestimating the number of trials they had performed correctly. Relative to control participants, the dysphoric and depressed groups showed a reduction in the extent of this positive bias in that they judged error trials more accurately and correct trials less accurately. Although the dysphoric and depressed groups both reported elevated trait SFA, this did not correlate significantly with accuracy of self-judgment on the performance-monitoring task. Implications for self-regulation models of depression are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
15.
已往库存论中的决策模型,它是把现实过程用数学的方法进行分析,得到决策值,但不能看到决策的过程,不能反映出现实生活中的不确定性、动态性。运用Delphi 7.0和SQL server 2000对销售过程进行了动态仿真,利用Newsboy模型的推广(S,s)订购策略来监控库存并做出决策,这样就体现出此过程的不确定性、动态性;且举出了一个仿真商品销售的实例,对其中的一些关键技术,如何仿真、算法的实现等进行了阐述。 相似文献
16.
简短评述了大容量和超大容量光通信系统的WDM和OTDM技术,提出了一个在OTDM通信系统中用锁模光纤激光器做时钟提取器的新方法,给出了一个利用设置波分预标时钟脉冲方案构成的新的全光型OTDM通信实验系统结构。 相似文献
17.
Sánchez-Meca Julio; Marín-Martínez Fulgencio; Chacón-Moscoso Salvador 《Canadian Metallurgical Quarterly》2003,8(4):448
It is very common to find meta-analyses in which some of the studies compare 2 groups on continuous dependent variables and others compare groups on dichotomized variables. Integrating all of them in a meta-analysis requires an effect-size index in the same metric that can be applied to both types of outcomes. In this article, the performance in terms of bias and sampling variance of 7 different effect-size indices for estimating the population standardized mean difference from a 2 × 2 table is examined by Monte Carlo simulation, assuming normal and nonnormal distributions. The results show good performance for 2 indices, one based on the probit transformation and the other based on the logistic distribution. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
18.
Fellers Gloria; McInnis Charles; Cappelli Mario; Cragg Susan; Vaillancourt Raymond 《Canadian Metallurgical Quarterly》1987,19(1):108
The WAIS-R Information subtest was combined with 21 potential substitute Canadian content items and group-administered to 119 high school students ranging in age from 16 to 19 years. Seven acceptable substitute items were identified. Mean scores on the American items for the 16-17 and 18-19 age groups suggested that Canadians of these ages are not penalized by American content with respect to either Verbal or Full Scale IQ. Nevertheless, the research identified eight Information items, four easier and four more difficult than the standard WAIS-R implies. Similar results were noted in two previous studies of the WAIS-R, and indicate the extreme caution required for the clinical interpretation of intra test scatter. There is also evidence that item difficulty within the Information subtest may vary with the age of the subject. These results were considered indicative of the necessity for Canadian content Information items and the development of Canadian norms for an adapted WAIS-R Information subtest. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
19.
20.