全文获取类型
收费全文 | 1760篇 |
免费 | 259篇 |
国内免费 | 218篇 |
专业分类
电工技术 | 156篇 |
综合类 | 192篇 |
化学工业 | 98篇 |
金属工艺 | 6篇 |
机械仪表 | 30篇 |
建筑科学 | 32篇 |
矿业工程 | 19篇 |
能源动力 | 34篇 |
轻工业 | 27篇 |
水利工程 | 24篇 |
石油天然气 | 18篇 |
武器工业 | 13篇 |
无线电 | 184篇 |
一般工业技术 | 144篇 |
冶金工业 | 516篇 |
原子能技术 | 9篇 |
自动化技术 | 735篇 |
出版年
2024年 | 11篇 |
2023年 | 41篇 |
2022年 | 72篇 |
2021年 | 84篇 |
2020年 | 83篇 |
2019年 | 64篇 |
2018年 | 58篇 |
2017年 | 60篇 |
2016年 | 76篇 |
2015年 | 65篇 |
2014年 | 68篇 |
2013年 | 87篇 |
2012年 | 115篇 |
2011年 | 116篇 |
2010年 | 91篇 |
2009年 | 109篇 |
2008年 | 94篇 |
2007年 | 97篇 |
2006年 | 92篇 |
2005年 | 115篇 |
2004年 | 121篇 |
2003年 | 101篇 |
2002年 | 80篇 |
2001年 | 61篇 |
2000年 | 21篇 |
1999年 | 18篇 |
1998年 | 14篇 |
1997年 | 13篇 |
1996年 | 11篇 |
1995年 | 18篇 |
1994年 | 9篇 |
1993年 | 10篇 |
1992年 | 10篇 |
1991年 | 7篇 |
1990年 | 7篇 |
1989年 | 5篇 |
1988年 | 8篇 |
1984年 | 4篇 |
1975年 | 5篇 |
1966年 | 7篇 |
1965年 | 5篇 |
1964年 | 14篇 |
1963年 | 13篇 |
1962年 | 6篇 |
1960年 | 6篇 |
1959年 | 8篇 |
1958年 | 6篇 |
1957年 | 7篇 |
1956年 | 9篇 |
1955年 | 5篇 |
排序方式: 共有2237条查询结果,搜索用时 15 毫秒
1.
本文主要研究随机环境中配对依赖人口数两性 Galton-Watson 分枝过程的条件均值增长率的极限性质.利用上可加函数的性质,得到配对单元平均增长率的极限性质和该过程条件均值的上界和下界.文中给出了关于过程条件均值增长率的两个序列,利用配对单元平均增长率的性质,获得了这两个序列的极限性质.随机环境中配对依赖人口数两性分枝过程比较复杂,本文的结论推广了现有的研究成果. 相似文献
2.
数字电视的条件接收系统 总被引:1,自引:0,他引:1
数字电视的兴起使人们能够欣赏到高质量的电视节目,伴随数字电视的成熟,条件接收系统(CAS)得到很好的发展。主要介绍数字电视条件接收系统相关技术的发展、基本功能、安全机制、工作原理及其安全性要求。 相似文献
3.
4.
Rats received a single pairing of an auditory conditioned stimulus (CS) with a footshock unconditioned stimulus (US). The fear (freezing) that had accrued to the CS was then extinguished. Injection of naloxone prior to this extinction significantly impaired the development of extinction. This impairment was mediated by opioid receptors in the brain and was not observed when naloxone was injected after extinction training. Finally, an injection of naloxone on test failed to reinstate extinguished responding that had already accrued to the CS. These experiments show that opioid receptors regulate the development, but not the expression, of fear extinction and are discussed with reference to the roles of opioid receptors in US processing, memory, and appetitive motivation. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
5.
Yue Fang 《时间序列分析杂志》2005,26(4):527-541
Abstract. We analyze, by simulation, the finite‐sample properties of goodness‐of‐fit tests based on residual autocorrelation coefficients (simple and partial) obtained using different estimators frequently used in the analysis of autoregressive moving‐average time‐series models. The estimators considered are unconditional least squares, maximum likelihood and conditional least squares. The results suggest that although the tests based on these estimators are asymptotically equivalent for particular models and parameter values, their sampling properties for samples of the size commonly found in economic applications can differ substantially, because of differences in both finite‐sample estimation efficiencies and residual regeneration methods. 相似文献
6.
Evans Jonathan St. B. T.; Handley Simon J.; Over David E. 《Canadian Metallurgical Quarterly》2003,29(2):321
The authors report 3 experiments in which participants were invited to judge the probability of statements of the form if p then q given frequency information about the cases pq, p?q, ?pq, and ?p?q (where ? = not). Three hypotheses were compared: (a) that people equate the probability with that of the material conditional, 1 - P(p?q); (b) that people assign the conditional probability, P(q/p); and (c) that people assign the conjunctive probability P(pq). The experimental evidence allowed rejection of the 1st hypothesis but provided some support for the 2nd and 3rd hypotheses. Individual difference analyses showed that half of the participants used conditional probability and that most of the remaining participants used conjunctive probability as the basis of their judgments. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
7.
Berrin-Wasserman Stacy; Winnick Wilma A.; Borod Joan C. 《Canadian Metallurgical Quarterly》2003,17(3):429
Does sentence generation and/or stimulus emotionality enhance verbal memory in patients with neurological impairment? This question was addressed by testing 40 patients with unilateral stroke (20 with left-brain and 20 with right-brain damage) and 20 healthy control participants for recall and recognition of 48 target words. During encoding, emotional and nonemotional words were either presented in sentences (read condition) or used to form sentences (generate condition). Both word emotionality and generative processing improved memory performance in all groups. The authors suggest that a similar influence (i.e., cognitive activation) underlies both of these memory-enhancing effects, although the putative origins of the 2 effects are quite different. Neuropsychological underpinnings and clinical implications of these phenomena are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
8.
Drew Michael R.; Yang Cynthia; Ohyama Tatsuya; Balsam Peter D. 《Canadian Metallurgical Quarterly》2004,30(3):163
Three experiments investigated the effects of varying the conditioned stimulus (CS) duration between training and extinction. Ring doves (Streptopelia risoria) were autoshaped on a fixed CS-unconditioned stimulus (US) interval and extinguished with CS presentations that were longer, shorter, or the same as the training duration. During a subsequent test session, the training CS duration was reintroduced. Results suggest that the cessation of responding during an extinction session is controlled by generalization of excitation between the training and extinction CSs and by the number of nonreinforced CS presentations. Transfer of extinction to the training CS is controlled by the similarity between the extinction and training CSs. Extinction learning is temporally specific. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
9.
This paper proposed a novel hybrid probabilistic network, which is a good tradeoff between the model complexity and learnability
in practice. It relaxes the conditional independence assumptions of Naive Bayes while still permitting efficient inference
and learning. Experimental studies on a set of natural domains prove its clear advantages with respect to the generalization
ability. 相似文献
10.
It has been reported that it is harder to switch to a strong, well-practiced task from a weaker, less-practiced task than vice versa. Three experiments replicated this surprising asymmetry and investigated how it is affected by a reduction in interference between tasks. Experiment 1 progressively delayed the onset of the stimulus attribute associated with the stronger task. Experiments 2 and 3 separated the response sets of the tasks. Both manipulations reduced, without eliminating, interference of the stronger with the weaker task but reversed the asymmetry of switch costs, resulting in a larger cost of switching to the weaker task. The results are interpreted in terms of a model of the interactions between control input, task strength, and task priming. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献