全文获取类型
收费全文 | 10295篇 |
免费 | 303篇 |
国内免费 | 14篇 |
专业分类
电工技术 | 142篇 |
综合类 | 8篇 |
化学工业 | 2350篇 |
金属工艺 | 243篇 |
机械仪表 | 190篇 |
建筑科学 | 449篇 |
矿业工程 | 54篇 |
能源动力 | 302篇 |
轻工业 | 679篇 |
水利工程 | 105篇 |
石油天然气 | 106篇 |
无线电 | 652篇 |
一般工业技术 | 1778篇 |
冶金工业 | 1844篇 |
原子能技术 | 102篇 |
自动化技术 | 1608篇 |
出版年
2022年 | 109篇 |
2021年 | 150篇 |
2020年 | 121篇 |
2019年 | 115篇 |
2018年 | 160篇 |
2017年 | 159篇 |
2016年 | 201篇 |
2015年 | 173篇 |
2014年 | 255篇 |
2013年 | 715篇 |
2012年 | 391篇 |
2011年 | 495篇 |
2010年 | 367篇 |
2009年 | 402篇 |
2008年 | 449篇 |
2007年 | 394篇 |
2006年 | 387篇 |
2005年 | 329篇 |
2004年 | 301篇 |
2003年 | 255篇 |
2002年 | 257篇 |
2001年 | 178篇 |
2000年 | 171篇 |
1999年 | 168篇 |
1998年 | 230篇 |
1997年 | 191篇 |
1996年 | 175篇 |
1995年 | 145篇 |
1994年 | 154篇 |
1993年 | 143篇 |
1992年 | 130篇 |
1991年 | 111篇 |
1990年 | 111篇 |
1989年 | 144篇 |
1988年 | 101篇 |
1987年 | 119篇 |
1986年 | 122篇 |
1985年 | 135篇 |
1984年 | 158篇 |
1983年 | 116篇 |
1982年 | 117篇 |
1981年 | 95篇 |
1980年 | 90篇 |
1979年 | 99篇 |
1978年 | 82篇 |
1977年 | 102篇 |
1976年 | 98篇 |
1975年 | 87篇 |
1974年 | 92篇 |
1973年 | 75篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Data collection, both automatic and manual, lies at the heart of all empirical studies. The quality of data collected from
software informs decisions on maintenance, testing and wider issues such as the need for system re-engineering. While of the
two types stated, automatic data collection is preferable, there are numerous occasions when manual data collection is unavoidable.
Yet, very little evidence exists to assess the error-proneness of the latter. Herein, we investigate the extent to which manual
data collection for Java software compared with its automatic counterpart for the same data. We investigate three hypotheses
relating to the difference between automated and manual data collection. Five Java systems were used to support our investigation.
Results showed that, as expected, manual data collection was error-prone, but nowhere near the extent we had initially envisaged.
Key indicators of mistakes in manual data collection were found to be poor developer coding style, poor adherence to sound
OO coding principles, and the existence of relatively large classes in some systems. Some interesting results were found relating
to the collection of public class features and the types of error made during manual data collection. The study thus offers
an insight into some of the typical problems associated with collecting data manually; more significantly, it highlights the
problems that poorly written systems have on the quality of visually extracted data. 相似文献
72.
Abstract. This article proposes an extension to scalar component methodology for the identification and estimation of VARMA models. The complete methodology determines the exact positions of all free parameters in any VARMA model with a predetermined embedded scalar component structure. This leads to an exactly identified system of equations that is estimated using full information maximum likelihood. 相似文献
73.
74.
George M. Prince 《Creativity & Innovation Management》2003,12(4):240-246
Independently of the creativity movement, others have demonstrated the benefits of creating positive fields. I have reviewed a number of cases involving field below and added some from my own creativity experiences. I then explore the psychological explanation of why such fields are effective and go on to the findings of recent brain research, which not only reinforce the benefits of positive fields but also throw light on the difficulty of creating them. Finally, I offer some suggestions from my own experience of what can be done to create positive fields. I believe that this should now be the focus of our efforts: to the extent that we are successful, we should get the creativity and innovation we need as a by‐product. 相似文献
75.
Lowe Rob; Bennett Paul; Walker Ian; Milne Sarah; Bozionelos George 《Canadian Metallurgical Quarterly》2003,22(5):464
The theory of planned behavior suggests attitudes are a product of salient beliefs. This study examined whether aggregating salient beliefs was plausible within a more biologically centered information-processing environment. A neural network was used to examine associations among beliefs relating to exercise intention. Data on intentions and behavioral, normative, and control beliefs from 114 respondents were used to train (by error backpropagation) a neural network to associate beliefs with intention. The R2 between the network's estimated and self-reported intention was .66. The network's representation comprised 6 belief profiles associated with high, moderate, or low behavioral intention. The neural network accommodated complex relationships among beliefs and belief-intention associations and indicated how high-level constructs such as attitudes may be viewed as the best fit (compromise state) between aroused beliefs. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
76.
77.
78.
Catalytic chlorination of methane was studied over SO
4
2–
/ZrO2, Pt/SO
4
2–
/ZrO2, and Fe/Mn/SO
4
2–
/ZrO2 solid superacid catalysts. The reactions were carried out in a continuous flow reactor under atmospheric pressure, at temperatures below 240°C, with a gaseous hourly space velocity of 1000 ml/g h and a methane to chlorine ratio of 4 to 1. At 200°C with 30% chlorine converted the selectivity in methyl chloride exceeds 90%. At more elevated temperatures, the selectivity decreases but stays above 80% in methyl chloride at 225°C using the sulfated zirconia catalysts. The selectivity can be enhanced by adding platinum to sulfated zirconia catalysts. An iron and manganese-doped catalyst exhibited excellent selectivities at somewhat lower conversions. Methyl chloride is obtained at 235°C in selectivities greater than 85%. No chloroform or carbon tetrachloride is formed. The electrophilic insertion involves electron-deficient metal-coordinated chlorine into the methane C-H bond.Catalysis by solid superacids, 29. For part 28 see ref. [14]. 相似文献
79.
Addresses the problem of incongruity between beliefs and behaviors. The theories of attribution and cognitive dissonance are briefly discussed, and their implications for behavior are noted. Issues that arise from obtaining behavioral effects in the absence of effects on beliefs and evaluations are delineated, and previous theories to account for these results are reviewed. Studies cited by R. E. Nisbett and T. D. Wilson (see record 1978-00295-001), by Wilson (1983), and by D. J. Bem (1972) are scrutinized with respect to the present author's critical and theoretical objectives, and a similar analysis is applied to more recent experiments on overjustification. It is concluded that (a) self-report effects are significant and congruent with behavior more frequently than previous reviewers have indicated, (b) behavior may interfere with inferential processes and thereby erase or prevent from occurring internal state changes that would otherwise be found, and (c) incongruity and other problems are symptomatic of there being no sophisticated theoretical account of how internal states mediate behavior. Basic facts about studies reviewed by Nisbett and Wilson are appended. (109 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
80.