全文获取类型
收费全文 | 1068篇 |
免费 | 112篇 |
国内免费 | 73篇 |
专业分类
电工技术 | 24篇 |
综合类 | 155篇 |
化学工业 | 68篇 |
金属工艺 | 9篇 |
机械仪表 | 30篇 |
建筑科学 | 63篇 |
矿业工程 | 19篇 |
能源动力 | 15篇 |
轻工业 | 20篇 |
水利工程 | 31篇 |
石油天然气 | 10篇 |
武器工业 | 25篇 |
无线电 | 102篇 |
一般工业技术 | 124篇 |
冶金工业 | 253篇 |
原子能技术 | 6篇 |
自动化技术 | 299篇 |
出版年
2023年 | 11篇 |
2022年 | 18篇 |
2021年 | 31篇 |
2020年 | 23篇 |
2019年 | 34篇 |
2018年 | 24篇 |
2017年 | 31篇 |
2016年 | 40篇 |
2015年 | 39篇 |
2014年 | 72篇 |
2013年 | 71篇 |
2012年 | 66篇 |
2011年 | 77篇 |
2010年 | 65篇 |
2009年 | 56篇 |
2008年 | 50篇 |
2007年 | 69篇 |
2006年 | 60篇 |
2005年 | 57篇 |
2004年 | 66篇 |
2003年 | 55篇 |
2002年 | 36篇 |
2001年 | 31篇 |
2000年 | 18篇 |
1999年 | 19篇 |
1998年 | 11篇 |
1997年 | 6篇 |
1996年 | 9篇 |
1995年 | 12篇 |
1994年 | 9篇 |
1993年 | 9篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1986年 | 2篇 |
1982年 | 6篇 |
1967年 | 2篇 |
1966年 | 4篇 |
1965年 | 4篇 |
1964年 | 5篇 |
1963年 | 5篇 |
1962年 | 3篇 |
1961年 | 4篇 |
1960年 | 4篇 |
1959年 | 3篇 |
1958年 | 3篇 |
1957年 | 2篇 |
1955年 | 4篇 |
排序方式: 共有1253条查询结果,搜索用时 31 毫秒
41.
Often quantitative data in the social sciences have only ordinal justification. Problems of interpretation can arise when least squares multiple regression (LSMR) is used with ordinal data. Two ordinal alternatives are discussed, dominance-based ordinal multiple regression (DOMR) and proportional odds multiple regression. The Q2 statistic is introduced for testing the omnibus null hypothesis in DOMR. A simulation study is discussed that examines the actual Type I error rate and power of Q2 in comparison to the LSMR omnibus F test under normality and non-normality. Results suggest that Q2 has favorable sampling properties as long as the sample size-to-predictors ratio is not too small, and Q2 can be a good alternative to the omnibus F test when the response variable is non-normal. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
42.
Urushihara Kouji; Wheeler Daniel S.; Pine?o Oskar; Miller Ralph R. 《Canadian Metallurgical Quarterly》2005,31(2):184
Three conditioned taste aversion experiments with rats investigated superconditioning. In each experiment, alternate exposures of 2 flavor compounds with a common element (i.e., AB/AS) were administered to establish an inhibitory relationship between the 2 unique elements, B and S, and prior to testing, S was paired with lithium chloride (LiCl). In Experiment 1, pairings of a neutral cue (X) with S in compound with B after the AB/AS exposures resulted in superconditioning between X and S. Extinction of the common element (A) just before the S-LiCl pairing attenuated both the inhibitory relationship between B and S (Experiment 2) and superconditioning between X and S (Experiment 3). These observations suggest that superconditioning consists of enhanced performance rather than enhanced associative acquisition. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
43.
Estimation and hypothesis testing based on normal samples censored in the middle are developed and shown to be remarkably
efficient and robust to symmetric shorttailed distributions and to inliers in a sample. This negates the perception that sample
mean and variance are the best robust estimators in such situations (Tiku, 1980; Dunnett, 1982).
Professor Emeritus, Department of Mathematics and Statistics, McMaster University,
Professor Emeritus, Department of Mathematics and Statistics, McMaster University, 相似文献
44.
本文讨论逆绎推理的形式化问题,指出这一问题的认知基础,然后证明逆绎推理可通过建立必要性假设来完成;NH构成了对已有知识订的扩充,必须构造必要性假设理论来捕捉逆绎推理的逻辑特征,本文选择缺席逻辑作为形式化NL的理论框架,并指出NL的基本性质。 相似文献
45.
Process capability index Cpk has been widely used in the manufacturing industry as a process performance measure. In this paper, we investigate the natural estimator of the index Cpk, and show that under the assumption of normality its distribution can be expressed as a mixture of the chi-square and the normal distributions. We also implement the theory of hypothesis testing using the natural estimator of Cpk, and provide efficient Maple programs to calculate the p-values as well as the critical values for various values of -risk, capability requirements, and sample sizes. The behavior of the p-values and critical values as functions of the distribution parameters are investigated to obtain tight critical values for reliable testing. Based on the test, we develop a simple and practical procedure for in-plant applications. The practitioners can use the proposed procedure to determine whether their process meets the preset capability requirement, and make reliable decisions. 相似文献
46.
The octave illusion (D. Deutsch, 1974) occurs when 2 tones separated by an octave are alternated repeatedly, such that when the right ear receives the high tone, the left ear receives the low tone, and vice versa. Most subjects in the original study reported hearing a single tone that alternated from ear to ear, whose pitch also alternated from octave to octave, and D. Deutsch (1975a) proposed an explanation in terms of separate what and where auditory pathways. C. D. Chambers, J. B. Mattingley, and S. A. Moss (2002) argued that the perceived pitch difference generally corresponds more to a semitone and proposed an alternative explanation in terms of diplacusis. This article argues that Chambers et al. used problematic procedures and reports a new experiment on the octave illusion. The findings confirm that an octave difference is generally perceived, and they agree with the model of Deutsch (1975a) but are at variance with the diplacusis hypothesis. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
47.
Processing capacity-defined as the relative ability to perform mental work in a unit of time-is a critical construct in cognitive psychology and is central to theories of visual attention. The unambiguous use of the construct, experimentally and theoretically, has been hindered by both conceptual confusions and the use of measures that are at best only coarsely mapped to the construct. However, more than 25 years ago, J. T. Townsend and F. G. Ashby (1978) suggested that the hazard function on the response time (RT) distribution offered a number of conceptual advantages as a measure of capacity. The present study suggests that a set of statistical techniques, well-known outside the cognitive and perceptual literatures, offers the ability to perform hypothesis tests on RT-distribution hazard functions. These techniques are introduced, and their use is illustrated in application to data from the contingent attentional capture paradigm. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
48.
James D. Johnston Ashlin E. Cowger Robert J. Graul Ryan Nash Josie A. Tueller Nathan R. Hendrickson Daniel R. Robinson John D. Beard K. Scott Weber 《Indoor air》2019,29(6):1005-1017
Recent work suggests that evaporative coolers increase the level and diversity of bioaerosols, but this association remains understudied in low‐income homes. We conducted a cross‐sectional study of metropolitan, low‐income homes in Utah with evaporative coolers (n = 20) and central air conditioners (n = 28). Dust samples (N = 147) were collected from four locations in each home and analyzed for dust‐mite allergens Der p1 and Der f1, endotoxins, and β‐(1 → 3)‐d ‐glucans. In all sample locations combined, Der p1 or Der f1 was significantly higher in evaporative cooler versus central air conditioning homes (OR = 2.29, 95% CI = 1.05‐4.98). Endotoxin concentration was significantly higher in evaporative cooler versus central air conditioning homes in furniture (geometric mean (GM) = 8.05 vs 2.85 EU/mg, P < .01) and all samples combined (GM = 3.60 vs 1.29 EU/mg, P = .03). β‐(1 → 3)‐d ‐glucan concentration and surface loads were significantly higher in evaporative cooler versus central air conditioning homes in all four sample locations and all samples combined (P < .01). Our study suggests that low‐income, evaporative cooled homes have higher levels of immunologically important bioaerosols than central air‐conditioned homes in dry climates, warranting studies on health implications and other exposed populations. 相似文献
49.
鉴于假设检验在统计推断中的重要地位和学习它的困难度,通过讨论两类错误的产生与控制,结合概率论中的"小概率原理"和逻辑方法中的"反证法",给出了一种清晰简便的假设检验推导和推理方法。该方法适用于一个总体下总体均值、总体比例、总体方差的检验,也适用于两个个总体下总体均值、总体比例、总体方差的检验。检验结果表明,该推理方法简便、自然、适宜推广。 相似文献
50.
Research has shown inconsistent relationships between social anxiety and time spent on Facebook, possibly because Facebook’s many activities vary in degree of social interactivity. We examined the relationships between social anxiety, anxiety on Facebook, and social Facebook use. A multiple regression predicting social Facebook use revealed an interaction. Participants with high anxiety on Facebook and high social anxiety reported more frequent social Facebook use than those with high anxiety on Facebook and low social anxiety. A second multiple regression predicting social anxiety showed a suppression effect, indicating that social Facebook use predicts social anxiety only once anxiety on Facebook has been accounted for. These findings suggest that anxiety on Facebook clarifies the relationship between social anxiety and social Facebook use. 相似文献