全文获取类型
收费全文 | 2320篇 |
免费 | 177篇 |
国内免费 | 141篇 |
专业分类
电工技术 | 201篇 |
综合类 | 272篇 |
化学工业 | 66篇 |
金属工艺 | 46篇 |
机械仪表 | 181篇 |
建筑科学 | 51篇 |
矿业工程 | 55篇 |
能源动力 | 24篇 |
轻工业 | 46篇 |
水利工程 | 33篇 |
石油天然气 | 29篇 |
武器工业 | 38篇 |
无线电 | 435篇 |
一般工业技术 | 108篇 |
冶金工业 | 71篇 |
原子能技术 | 28篇 |
自动化技术 | 954篇 |
出版年
2023年 | 8篇 |
2022年 | 25篇 |
2021年 | 33篇 |
2020年 | 31篇 |
2019年 | 23篇 |
2018年 | 25篇 |
2017年 | 22篇 |
2016年 | 49篇 |
2015年 | 54篇 |
2014年 | 72篇 |
2013年 | 85篇 |
2012年 | 114篇 |
2011年 | 131篇 |
2010年 | 128篇 |
2009年 | 161篇 |
2008年 | 216篇 |
2007年 | 309篇 |
2006年 | 247篇 |
2005年 | 197篇 |
2004年 | 177篇 |
2003年 | 147篇 |
2002年 | 89篇 |
2001年 | 85篇 |
2000年 | 49篇 |
1999年 | 20篇 |
1998年 | 12篇 |
1997年 | 19篇 |
1996年 | 16篇 |
1995年 | 11篇 |
1994年 | 11篇 |
1993年 | 14篇 |
1992年 | 7篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 6篇 |
1988年 | 2篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1963年 | 1篇 |
1962年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有2638条查询结果,搜索用时 15 毫秒
41.
42.
为了提高虚拟士兵的真实度与可信度,在分析现有研究成果的基础上,依据生物记忆原理和遗忘特性,提出了一种智能记忆模型.构造了记忆信息的编码形式,建立了基于槽式和广义树结构的记忆分层存储模型;提出了带有参数的遗忘算法,并运用宽度优先算法,实现了记忆信息的搜索和调用.借助Matlab工具对算法进行了验证,验证结果表明该算法与实际情况基本相符. 相似文献
43.
In the present study, the authors tested the effects of working-memory load on math problem solving in 3 different cultures: Flemish-speaking Belgians, English-speaking Canadians, and Chinese-speaking Chinese currently living in Canada. Participants solved complex addition problems (e.g., 58 + 76) in no-load and working-memory load conditions, in which either the central executive or the phonological loop was loaded. The authors used the choice/no-choice method to obtain unbiased measures of strategy selection and strategy efficiency. The Chinese participants were faster than the Belgians, who were faster and more accurate than the Canadians. The Chinese also required fewer working-memory resources than did the Belgians and Canadians. However, the Chinese chose less adaptively from the available strategies than did the Belgians and Canadians. These cultural differences in math problem solving are likely the result of different instructional approaches during elementary school (practice and training in Asian countries vs. exploration and flexibility in non-Asian countries), differences in the number language, and informal cultural norms and standards. The relevance of being adaptive is discussed as well as the implications of the results in regards to the strategy choice and discovery simulation model of strategy selection (J. Shrager & R. S. Siegler, 1998). (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
44.
《国际计算机数学杂志》2012,89(8):998-1016
The paper concerns with the computational algorithms for a steady-state reaction diffusion problem. A lagged diffusivity iterative algorithm is proposed for solving resulting system of quasilinear equations from a finite difference discretization. The convergence of the algorithm is discussed and the numerical results show the efficiency of this algorithm. 相似文献
45.
Irene Appolloni Sebastiano Curreli Sara Caviglia Manuela Barilari Eleonora Gambini Aldo Pagano Paolo Malatesta 《International journal of molecular sciences》2012,13(11):14667-14678
Tumor progression is a key aspect in oncology. Not even the overexpression of a powerful oncogenic stimulus such as platelet derived growth factor-B (PDGF-B) is sufficient per se to confer full malignancy to cells. In previous studies we showed that neural progenitors overexpressing PDGF-B need to undergo progression to acquire the capability to give rise to secondary tumor following transplant. By comparing the expression profile of PDGF-expressing cells before and after progression, we found that progressed tumors consistently downregulate the expression of the antiproliferative gene Btg2. We therefore tested whether the downregulation of Btg2 is sufficient and necessary for glioma progression with loss and gain of function experiments. Our results show that downregulation of Btg2 is not sufficient but is necessary for tumor progression since the re-introduction of Btg2 in fully progressed tumors dramatically impairs their gliomagenic potential. These results suggest an important role of Btg2 in glioma progression. Accordingly with this view, the analysis of public datasets of human gliomas showed that reduced level of Btg2 expression correlates with a significantly worse prognosis. 相似文献
46.
Accurate measurement of cognitive strategies is important in diverse areas of psychological research. Strategy self-reports are a common measure, but C. Thevenot, M. Fanget, and M. Fayol (2007) proposed a more objective method to distinguish different strategies in the context of mental arithmetic. In their operand recognition paradigm, speed of recognition memory for problem operands after solving a problem indexes strategy (e.g., direct memory retrieval vs. a procedural strategy). Here, in 2 experiments, operand recognition time was the same following simple addition or multiplication, but, consistent with a wide variety of previous research, strategy reports indicated much greater use of procedures (e.g., counting) for addition than multiplication. Operation, problem size (e.g., 2 + 3 vs. 8 + 9), and operand format (digits vs. words) had interactive effects on reported procedure use that were not reflected in recognition performance. Regression analyses suggested that recognition time was influenced at least as much by the relative difficulty of the preceding problem as by the strategy used. The findings indicate that the operand recognition paradigm is not a reliable substitute for strategy reports and highlight the potential impact of difficulty-related carryover effects in sequential cognitive tasks. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
47.
详细研讨使用PLC进行流量累积、显示的编程算法,重点讲解在编制程序时应该注意的问题及解决问题的方法,并给出比较详细的编程例子。 相似文献
48.
《国际设备工程与管理》2012,(1):50-57
It is an important content of equipment management to keep the engineering machine well. Based on the theory of component technology and grey related algorithm arithmetic,the requirements and procedures of engineering machine maintenance predicting process are analyzed,and a support object evaluation system is provided. The qualitative and quantitative indexes of evaluating process are fully taken into consideration to provide scientific meth- ods and ways for proper evaluation and decision. 相似文献
49.
The authors investigated the performance on simple multiplication and division problems of 8-year-old children longitudinally to determine the developmental trajectories of both operations. Twice a year, during 2 consecutive school years, children performed a multiplication and division verification task and a number-matching task. All effects that were observed in multiplication performance (problem size, 5, and tie effect and Tie × Size interaction) were also observed in division performance. The developmental trajectories of these effects are described. The authors observed strong developmental parallels between both operations. These results are in line with strongly interconnected memory networks for multiplication and division facts, at least in young children. The results of the number-matching task showed that the interference effect developed differently for multiplication and division, indicating that automatic activation spreading from division operands to division answers is not at work in children of that age. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
50.
Explanations of working memory span in children were studied in a longitudinal follow-up of J. N. Towse, G. J. Hitch, and U. Hutton (1998). Reading span and operation span were lower when within-task retention intervals were lengthened. For each task, variation in span between test waves and age cohorts was systematically related to changes in processing speed. The two spans explained substantial shared variance in both reading and arithmetic scores, with some evidence for domain specificity. Combined span scores predicted unique variance in scholastic attainment over a 1-year interval. The authors concluded that working memory span is constrained by rapid loss of active codes and is not simply a measure of capacity for resource sharing. Working memory is also implicated in scholastic development. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献