全文获取类型
收费全文 | 6828篇 |
免费 | 249篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 64篇 |
综合类 | 5篇 |
化学工业 | 1313篇 |
金属工艺 | 139篇 |
机械仪表 | 147篇 |
建筑科学 | 405篇 |
矿业工程 | 14篇 |
能源动力 | 221篇 |
轻工业 | 685篇 |
水利工程 | 112篇 |
石油天然气 | 17篇 |
无线电 | 477篇 |
一般工业技术 | 1235篇 |
冶金工业 | 1167篇 |
原子能技术 | 49篇 |
自动化技术 | 1034篇 |
出版年
2023年 | 36篇 |
2022年 | 28篇 |
2021年 | 103篇 |
2020年 | 94篇 |
2019年 | 99篇 |
2018年 | 116篇 |
2017年 | 133篇 |
2016年 | 124篇 |
2015年 | 141篇 |
2014年 | 190篇 |
2013年 | 424篇 |
2012年 | 349篇 |
2011年 | 433篇 |
2010年 | 302篇 |
2009年 | 337篇 |
2008年 | 451篇 |
2007年 | 374篇 |
2006年 | 314篇 |
2005年 | 320篇 |
2004年 | 263篇 |
2003年 | 239篇 |
2002年 | 223篇 |
2001年 | 131篇 |
2000年 | 101篇 |
1999年 | 124篇 |
1998年 | 163篇 |
1997年 | 108篇 |
1996年 | 126篇 |
1995年 | 93篇 |
1994年 | 96篇 |
1993年 | 85篇 |
1992年 | 72篇 |
1991年 | 50篇 |
1990年 | 59篇 |
1989年 | 75篇 |
1988年 | 42篇 |
1987年 | 57篇 |
1986年 | 52篇 |
1985年 | 65篇 |
1984年 | 66篇 |
1983年 | 56篇 |
1982年 | 46篇 |
1981年 | 49篇 |
1980年 | 29篇 |
1979年 | 40篇 |
1978年 | 36篇 |
1977年 | 27篇 |
1976年 | 26篇 |
1975年 | 28篇 |
1974年 | 21篇 |
排序方式: 共有7084条查询结果,搜索用时 765 毫秒
41.
Xiang Lu S. Sundar Kumar Iyer Jin Lee Brian Doyle Zhineng Fan Paul K. Chu Chenming Hu Nathan W. Cheung 《Journal of Electronic Materials》1998,27(9):1059-1066
We have demonstrated feasibility to form silicon-on-insulator (SOI) substrates using plasma immersion ion implantation (PIII)
for both separation by implantation of oxygen and ion-cut. This high throughput technique can substantially lower the high
cost of SOI substrates due to the simpler implanter design as well as ease of maintenance. For separation by plasma implantation
of oxygen wafers, secondary ion mass spectrometry analysis and cross-sectional transmission electron micrographs show continuous
buried oxide formation under a single-crystal silicon overlayer with sharp Si/SiO2 interfaces after oxygen plasma implantation and high-temperature (1300°C) annealing. Ion-cut SOI wafer fabrication technique
is implemented for the first time using PIII. The hydrogen plasma can be optimized so that only one ion species is dominant
in concentration and there are minimal effects by other residual ions on the ion-cut process. The physical mechanism of hydrogen
induced silicon surface layer cleavage has been investigated. An ideal gas law model of the microcavity internal pressure
combined with a two-dimensional finite element fracture mechanics model is used to approximate the fracture driving force
which is sufficient to overcome the silicon fracture resistance. 相似文献
42.
National and regional corporate spatial structure 总被引:3,自引:0,他引:3
Much is known about the macro-impacts of business activities on national and regional economies; however, comparatively little
is known at the micro level about the impact spatial agglomeration of corporate wealth and performance has on urban systems.
This paper reports on a collaborative research project between the Australian Housing and Urban Research Institute and Dun
and Bradstreet, an international financial credit agency, to analyse the spatial implications of corporate structure in metropolitan
regions. This paper analyses spatial patterns of medium to large businesses in three Australian State capital cities at the
postcode level in order to assess the agglomeration of corporate capital, sales, and performance. The research indicates that
ratio analysis can provide a useful insight into the competitiveness of metropolitan regions and the control corporate headquarters
have over decision making and investment processes. The findings of this research are of special interest to capital markets,
business and urban researchers in the Asia Pacific Region.
Received: September 1997/Accepted: September 2001 相似文献
43.
Examines, in the context of cancer illness, S. E. Taylor and J. D. Brown's (see record 1988-16903-001) claim that mental health is to a degree predicated on illusory beliefs about the self, one's control, and the future. The Heroic Model (HM), a stance toward cancer characterized by belief that positive thoughts and feelings, a fighting spirit, and an optimistic outlook will promote cancer remission, is presented as paradigmatic of Taylor and Brown's thesis. Strong and weak formulations of the HM (the former affirming a direct influence of mental states over physical processes, and the latter affirming indirect effects only) are examined with respect to their potential adaptive value as true or false beliefs, with different consequences for well-being. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
44.
According to J. F. Dovidio and S. L. Gaertner's (1998) integrated model of racism, politically liberal European Americans tend to express racism differently than conservative European Americans, with liberals demonstrating aversive racism and conservatives, symbolic or modern racism. In support of the model, in Experiment 1 liberals showed bias in favor of a twice-prosecuted African American relative to a European American in their judgment of double jeopardy, whereas conservatives did the reverse. Experiment 2 replicated these effects while eliminating a confound in the design of Experiment 1. Experiment 3 found evidence for the intrapsychic conflict hypothesized to underlie aversive racism. Specifically, only liberals displayed greater physiological arousal to the touch of an African American versus a European American experimenter. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
45.
Seven hundred three members of the Society for Industrial and Organizational Psychology indicated agreement or disagreement with 49 propositions regarding cognitive ability tests in organizations. There was consensus that cognitive ability tests are valid and fair, that they provide good but incomplete measures, that different abilities are necessary for different jobs, and that diversity is valuable. Items dealing with the unique status of cognitive ability were most likely to generate polarized opinions. A 2-factor model, classifying items as those reflecting societal concerns over the consequences of ability testing and those reflecting an emphasis on the unique status of "g," fit the data well, and these factors proved especially important for predicting responses to the more controversial items. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
46.
47.
48.
Self-help cessation programs for smokeless tobacco users: long-term follow-up of a randomized trial.
Hebert H Severson Judy A Andrews Edward Lichtenstein Brian G Danaher Laura Akers 《Nicotine & tobacco research》2007,9(2):281-289
This paper presents long-term outcomes of the largest clinical trial of smokeless tobacco (SLT) cessation reported to date. SLT users in five northwestern states were recruited to call a toll-free number, and 1,069 users were randomized to one of two self-help conditions: either a manual-only condition or an assisted self-help condition, which included the manual, a targeted video, and two support phone calls. Significant between-group differences were not found for either the 12- or 18-month point-prevalence measure of abstinence from either SLT only or all tobacco products using outcomes based on either the responder or intention-to-treat outcomes. However, using a repeated point-prevalence measure across all three assessment points, we found that significantly more assisted self-help participants reported abstinence, compared with manual-only participants. Compared with manual-only participants, those in the assisted self-help condition were significantly more likely to use recommended cessation techniques. Results demonstrate that low-cost, minimal interventions delivered by mail and phone can help a sizable proportion of individuals quit using SLT. 相似文献
49.
Cara L Booker Jennifer B Unger Stanley P Azen Lourdes Baezconde-Garbanati Brian Lickel C Anderson Johnson 《Nicotine & tobacco research》2007,9(11):1085-1094
The associations between stressful life events and smoking have been established among adolescents in the United States. However, whether these relationships are similar in adolescents from other non-Western cultures is unknown. Understanding these relationships in adolescents may help to provide opportunities to reduce the smoking rates in those cultures by providing positive coping methods that do not include smoking. In this longitudinal study, the associations between nine stressful life events scales and smoking behaviors were examined in a sample of Chinese adolescents. Six of these scales, positive school-related, negative school-related, positive family-related, positive peer-related, negative peer-related, and negative health-related had significantly different means among females and males. Among males, positive school-related stress was a protective factor for smoking susceptibility. Among females, positive school-related stress was a protective factor and negative school-related stress was a risk factor for lifetime smoking, and negative family-related stress was a risk factor for smoking susceptibility. Findings indicate that smoking among male adolescents in China may not be the result of stress; however, in females stress may contribute to the decision to smoke. Future directions are discussed. 相似文献
50.