首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   5338篇
  免费   170篇
  国内免费   5篇
电工技术   39篇
综合类   6篇
化学工业   1152篇
金属工艺   82篇
机械仪表   79篇
建筑科学   216篇
矿业工程   20篇
能源动力   166篇
轻工业   366篇
水利工程   35篇
石油天然气   36篇
武器工业   2篇
无线电   430篇
一般工业技术   804篇
冶金工业   1368篇
原子能技术   14篇
自动化技术   698篇
  2023年   32篇
  2022年   72篇
  2021年   91篇
  2020年   59篇
  2019年   73篇
  2018年   88篇
  2017年   92篇
  2016年   89篇
  2015年   88篇
  2014年   129篇
  2013年   363篇
  2012年   221篇
  2011年   298篇
  2010年   190篇
  2009年   221篇
  2008年   220篇
  2007年   237篇
  2006年   197篇
  2005年   157篇
  2004年   123篇
  2003年   120篇
  2002年   127篇
  2001年   97篇
  2000年   80篇
  1999年   99篇
  1998年   241篇
  1997年   183篇
  1996年   129篇
  1995年   121篇
  1994年   88篇
  1993年   89篇
  1992年   50篇
  1991年   59篇
  1990年   75篇
  1989年   53篇
  1988年   55篇
  1987年   46篇
  1986年   47篇
  1985年   62篇
  1984年   59篇
  1983年   44篇
  1982年   47篇
  1981年   42篇
  1980年   49篇
  1979年   46篇
  1978年   50篇
  1977年   58篇
  1976年   76篇
  1975年   37篇
  1973年   35篇
排序方式: 共有5513条查询结果,搜索用时 15 毫秒
991.
The current study considered the influence of the 2008 presidential election on the racial identity of African American college students (Mage = 19.3 years; 26.3% male). The design of the study consisted of 2 components: longitudinal and daily. The longitudinal component assessed 3 dimensions of racial identity (centrality, private regard, and public regard) 2 weeks before and 5 months after the election, and the daily diary component assessed racial identity and identity exploration on the days immediately before and after the election. Daily items measuring identity exploration focused on how much individuals thought about issues relating to their race. Analyses considered the immediate effects of the election on identity exploration and the extent to which changes in exploration were shaped by racial identity measured prior to the election. We also considered immediate and longer term changes in racial identity following the election and the extent to which longer term changes were conditioned by identity exploration. Findings suggest that the election served as an “encounter” experience (Cross, 1991, 1995, pp. 60–61), which led to increases in identity exploration. Moreover, analyses confirmed that changes in identity exploration were most pronounced among those with higher levels of racial centrality. Results also suggest that the election had both an immediate and a longer term influence on racial identity, which in some instances was conditioned by identity exploration. (PsycINFO Database Record (c) 2011 APA, all rights reserved)  相似文献   
992.
The Hypomanic Attitudes and Positive Predictions Inventory (HAPPI; W. Mansell, 2006) was developed to assess multiple, extreme, self-relevant appraisals of internal states. The present study aimed to validate the HAPPI in a clinical sample. Participants (N = 50) with a diagnosis of bipolar disorder (confirmed by a structured clinical interview) completed a series of questionnaires pertaining to clinical factors, reward motivation, cognitive style, symptoms, and functioning at baseline, in addition to the HAPPI. Over the following 4 weeks, participants were asked to complete self-report measures of symptoms (activation, perceived conflict, depression, and well-being), as well as work and social functioning, twice weekly. The authors hypothesized that the HAPPI would be associated with prospective bipolar symptoms and functioning, when controlling for baseline symptoms and potentially confounding measures. The HAPPI was positively, independently associated with activation and conflict after 4 weeks. Furthermore, individual HAPPI factors were associated with activation, conflict, and depression. The results provided preliminary support for the predictive validity of the HAPPI in a clinical sample. The HAPPI could be used in the future as a tool in cognitive behavioral therapy for bipolar disorder to identify problematic beliefs and guide formulation. (PsycINFO Database Record (c) 2011 APA, all rights reserved)  相似文献   
993.
Clinical group practice is commonly guided by the assumption that 11 distinct therapeutic factors operate in psychotherapy groups. This assumption should be closely examined due to the emerging evidence of fewer, more global therapeutic factors. The present study was conducted to continue the development of the Therapeutic Factors Inventory–Short Form (TFI–S) and focused on confirming its factor structure and evaluating aspects of its concurrent, discriminant, and predictive validity. A sample comprising a total of 435 clients from 52 distinct therapy groups at eight different clinical sites in the U.S. and Canada was obtained. Structural equation modeling analyses indicated that a four-factor model had a reasonably good fit to the TFI–S rating data, and it provided indications for further refinement of the constituent items. The analyses resulted in a revised, 19-item measure, the Therapeutic Factors Inventory–19 (TFI–19). Three-level HLM analyses demonstrated that the four factors were sensitive to change in member perceptions over time. Significant and meaningful relationships between the TFI–19 factors and subscales of the Group Climate Questionnaire-Short Form provided support for the concurrent validity of the TFI–19. Two-level HLM analyses identified significant relationships between the TFI–19 factors and posttreatment status on symptomatic and interpersonal distress, thereby supporting the predictive validity of the TFI–19. The findings suggest that the TFI–19 may be a useful instrument to assess group members' perceptions of more global therapeutic factors. (PsycINFO Database Record (c) 2011 APA, all rights reserved)  相似文献   
994.
Friction stir welding generates periodic features within the weld. These ??onion ring?? features are associated with variations in both texture and the orientation of that texture along the length of the weld. Analysis of an AA2195 friction stir weld reveals the presence of periodic oscillations between the dominant B and $ \overline{\text{B}} $ components of the ideal shear texture, suggesting a periodic reversal in the predominant shear orientation during welding that is inconsistent with current understandings of the friction stir welding process. Microstructural features present in the weld and machine force variations during welding indicate that these textures may arise from the oscillation of an off-centered tool. Such a tool oscillation can generate a periodic extrusion of material around the tool, giving rise to the observed flow features, machine force variations, and reversals of the local shear texture orientations. A new model of material flow during friction stir welding is proposed to explain the observed features.  相似文献   
995.
The purpose of this report is to provide an overview of the public health implications of exposure via breast milk to cadmium, lead, and mercury for nursing infants and to provide health-based guidance. Daily intakes were calculated and compared with guidance values used for public health assessments at hazardous waste sites. Cadmium, lead, and mercury under normal conditions are found in breast milk at concentration ranges of < 1 microgram/L, 2-5 micrograms/L, and 1.4-1.7 micrograms/L, respectively. Women exposed environmentally or occupationally can have higher levels in their breast milk. Concentrations of about 5 micrograms/L (cadmium), 20 micrograms/L (lead), and 3.5 micrograms/L (mercury) appear to be adequate screening levels. Many factors affect both the distribution of cadmium, lead, and mercury in breast milk and the health consequences to an infant. It is not clear what additional impact low-level exposure via breast milk may have on an infant born with a body burden to one of these metals. There is sufficient evidence to make the case that contaminated breast milk is a source of potential risk to infants in certain populations. Prevention strategies that include behavior modification and proper nutrition should be communicated to women at risk. Identification and elimination of exposure pathways and a critical analysis of the benefits of breast feeding versus heavy metal exposure are needed on a site-specific or individual basis. Research is required to better understand the impact of low-level exposure to heavy metals via breast milk. Breastfeeding should be encouraged under most circumstances.  相似文献   
996.
A retrospective case reference study examining the use of alcohol and tobacco in 303 women aged 40 or over suffering from oral or oropharyngeal cancer was conducted in the south-west Netherlands. Both alcohol and tobacco consumption are important in the development of oral and oropharyngeal cancer with increased consumption of both markedly increasing the risks of cancer, but alcohol having the greater effect.  相似文献   
997.
Previous assessments of verbal cross-modal priming have typically been conducted with the visual and auditory modalities. Within-modal priming is always found to be substantially larger than cross-modal priming, a finding that could reflect modality modularity, or alternatively, differences between the coding of visual and auditory verbal information (i.e., geometric vs phonological). The present experiments assessed implicit and explicit memory within and between vision and haptics, where verbal information could be coded in geometric terms. Because haptic perception of words is sequential or letter-by-letter, experiments were also conducted to isolate the effects of simultaneous versus sequential processing from the manipulation of modality. Together, the results reveal no effects of modality change on implicit or explicit tests. The authors discuss representational similarities between vision and haptics as well as image mediation as possible explanations for the results. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
998.
Dual-process theories of recognition posit that a perceptual familiarity process contributes to both explicit recognition and implicit perceptual memory. This putative single familiarity process has been indexed by inclusion–exclusion, remember–know, and repetition priming measures. The present studies examined whether these measures identify a common familiarity process. Familiarity-based explicit recognition (as indexed by the inclusion–exclusion and the independence remember–know procedures) increased with conceptual processing. In contrast, implicit word-identification priming and familiarity-based word-stem completion (as indexed by inclusion–exclusion) increased with study–test perceptual similarity. These dissociations indicate that familiarity-based explicit recognition may be more sensitive to conceptual than to perceptual processing and is functionally distinct from the perceptual familiarity process mediating implicit perceptual memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
999.
This study evaluated body-image distortion and ideal body-size preferences in 423 nonbulimic women and 108 bulimics. Analyses of covariance were utilized to compare the bulimic and nonbulimic groups on measures of current and ideal body size. Weight was used as a covariate to evaluate the influence of actual body size on perception of current body size and selection of ideal body size. Bulimics chose current body sizes that were significantly larger than those picked by nonbulimics regardless of actual body size. Bulimics also chose thinner ideal body sizes than did nonbulimics, regardless of actual body size. These results suggest that body-image distortion and extreme preference for thinness are a fundamental characteristic of bulimia nervosa. These results were discussed in terms of how perception of a large body size and preference for a very thin body size might interact to produce a high degree of dissatisfaction and overconcern with body size in bulimia nervosa. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
1000.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号