全文获取类型
收费全文 | 7907篇 |
免费 | 531篇 |
国内免费 | 357篇 |
专业分类
电工技术 | 356篇 |
综合类 | 682篇 |
化学工业 | 693篇 |
金属工艺 | 378篇 |
机械仪表 | 521篇 |
建筑科学 | 673篇 |
矿业工程 | 139篇 |
能源动力 | 308篇 |
轻工业 | 214篇 |
水利工程 | 148篇 |
石油天然气 | 268篇 |
武器工业 | 80篇 |
无线电 | 995篇 |
一般工业技术 | 771篇 |
冶金工业 | 260篇 |
原子能技术 | 99篇 |
自动化技术 | 2210篇 |
出版年
2024年 | 14篇 |
2023年 | 54篇 |
2022年 | 78篇 |
2021年 | 127篇 |
2020年 | 164篇 |
2019年 | 145篇 |
2018年 | 148篇 |
2017年 | 222篇 |
2016年 | 240篇 |
2015年 | 245篇 |
2014年 | 392篇 |
2013年 | 550篇 |
2012年 | 509篇 |
2011年 | 619篇 |
2010年 | 453篇 |
2009年 | 471篇 |
2008年 | 482篇 |
2007年 | 584篇 |
2006年 | 464篇 |
2005年 | 468篇 |
2004年 | 364篇 |
2003年 | 368篇 |
2002年 | 273篇 |
2001年 | 242篇 |
2000年 | 198篇 |
1999年 | 146篇 |
1998年 | 107篇 |
1997年 | 119篇 |
1996年 | 80篇 |
1995年 | 85篇 |
1994年 | 52篇 |
1993年 | 51篇 |
1992年 | 43篇 |
1991年 | 30篇 |
1990年 | 32篇 |
1989年 | 20篇 |
1988年 | 25篇 |
1987年 | 19篇 |
1986年 | 14篇 |
1985年 | 17篇 |
1984年 | 15篇 |
1983年 | 9篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 12篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1975年 | 4篇 |
1966年 | 4篇 |
1957年 | 2篇 |
排序方式: 共有8795条查询结果,搜索用时 40 毫秒
51.
A stochastic model is proposed for a basic mechanism in the formation of uncertainties in physical quantity measurements.
__________
Translated from Izmeritel'naya Tekhnika, No. 1, pp. 12–17, January, 2006. 相似文献
52.
阐述了硅铁生产中焦碳生产输送系统的工作原理和工艺要求,介绍了PLC在原料输送系统中的应用,给出了PLC的I/O接线图及程序框图,提出了工业原料生产输送控制系统的设计特点。 相似文献
53.
Abstract. A pth‐order random coefficient integer‐valued autoregressive [RCINAR(p)] model is proposed for count data. Stationarity and ergodicity properties are established. Maximum likelihood, conditional least squares, modified quasi‐likelihood and generalized method of moments are used to estimate the model parameters. Asymptotic properties of the estimators are derived. Simulation results on the comparison of the estimators are reported. The models are applied to two real data sets. 相似文献
54.
S. Sarkani T.A. Mazzuchi D. Lewandowski D.P. Kihl 《Engineering Fracture Mechanics》2007,74(18):2971-2980
Those individual tests in a series of experiments that are not completed or must be suspended are known as “censored points,” or “runouts”. Inclusion of runouts in data analysis can be problematic, and such ad hoc approaches as ignoring the runout observation or treating it as a failure can significantly affect estimation. The methodology offered here alleviates the handling of runouts and censored data by using the maximum likelihood estimation (MLE) method to incorporate the censored data properly. The methodology is illustrated with an example problem using actual data and the affects of ad hoc approaches are illustrated. 相似文献
55.
The judged likelihood of a focal outcome should generally decrease as the list of alternative possibilities increases. For example, the likelihood that a runner will win a race goes down when 2 new entries are added to the field. However, 6 experiments demonstrate that the presence of implausible alternatives (duds) often increases the judged likelihood of a focal outcome. This dud-alternative effect was detected for judgments involving uncertainty about trivia facts and stochastic events. Nonnumeric likelihood measures and betting measures reliably detected the effect, but numeric likelihood measures did not. Time pressure increased the magnitude of the effect. The results were consistent with a contrast-effect account: The inclusion of duds increases the perceived strength of the evidence for the focal outcome, thereby affecting its judged likelihood. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
56.
CAO Xue-hong Department of Information Engineering Nanjing University of Posts Telecommunications Nanjing P.R. China 《中国邮电高校学报(英文版)》2005,12(2)
1Introduction Orthogonal Frequency Division Multiplexing(OFDM) has become a popular technique for transmis-sion of signals over wireless channels . OFDMhas beenadoptedinseveral wireless standards such as Digital Au-dio Broadcasting ( DAB) , Digital Video Broadcasting(DVB-T) ,the IEEE 802 .11a[1]Local Area Network(LAN) standard and high performance LAN type 2(HIPERLAN/2)[2]standard. OFDMis also being pur-sued for Dedicated Short-Range Communications(DSRC) for road side to … 相似文献
57.
We propose subspace distance measures to analyze the similarity between intrapersonal face subspaces, which characterize the variations between face images of the same individual. We call the conventional intrapersonal subspace average intrapersonal subspace (AIS) because the image differences often come from a large number of persons. An intrapersonal subspace is referred to as specific intrapersonal subspace (SIS) if the image differences are from just one person. We demonstrate that SIS varies significantly from person to person, and most SISs are not similar to AIS. Based on these observations, we introduce the maximum a posteriori (MAP) adaptation to the problem of SIS estimation, and apply it to the Bayesian face recognition algorithm. Experimental results show that the adaptive Bayesian algorithm outperforms the non-adaptive Bayesian algorithm as well as Eigenface and Fisherface methods if a small number of adaptation images are available. 相似文献
58.
一类三元线性分组码的译码 总被引:1,自引:0,他引:1
Pless[1]证明了三元(12,6,6)Golay码具有一种双层结构,并据此给出了该码的快速硬判决译码算法。本文推广了Golay码的Pless结构,给出了由三元(n,k,d)线性分组码构造的三元(3,n+k,≥min(n,2d,6))线性分组码,其中包括(12,6,6)Golay码和(18,9,6)码,并以三元(18,9,6)码为例给出了这类码的最大似然软判决译码算法。 相似文献
59.
This paper addresses the problem of bandwidth allocation under the weighted maximum rate constrained link sharing policy and proves a key theory in the condition of allocation termination. We propose several algorithms with various worst-case and average-case time complexities, and evaluate their computation elapse times. 相似文献
60.
Jacobo de Uña-Álvarez 《Computational statistics & data analysis》2007,51(5):2653-2669
A new model for cross-sectional lifetime data is presented. The model is based on the length-bias assumption, and it is adapted to situations in which several types of censoring may occur. The NPMLE of the survival function is derived. An EM-algorithm to approximate the NPMLE is devised. The performance of the introduced estimator is investigated through simulations. A real set of data collected as part of a study on unemployment duration in Spain is used for illustration purposes. 相似文献