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   11974篇
  免费   1659篇
  国内免费   1156篇
电工技术   659篇
技术理论   2篇
综合类   1434篇
化学工业   341篇
金属工艺   430篇
机械仪表   1023篇
建筑科学   747篇
矿业工程   234篇
能源动力   162篇
轻工业   249篇
水利工程   184篇
石油天然气   179篇
武器工业   165篇
无线电   1503篇
一般工业技术   870篇
冶金工业   2044篇
原子能技术   41篇
自动化技术   4522篇
  2024年   57篇
  2023年   219篇
  2022年   422篇
  2021年   432篇
  2020年   462篇
  2019年   348篇
  2018年   326篇
  2017年   390篇
  2016年   429篇
  2015年   513篇
  2014年   658篇
  2013年   711篇
  2012年   879篇
  2011年   977篇
  2010年   819篇
  2009年   819篇
  2008年   768篇
  2007年   851篇
  2006年   810篇
  2005年   742篇
  2004年   561篇
  2003年   563篇
  2002年   417篇
  2001年   344篇
  2000年   199篇
  1999年   156篇
  1998年   107篇
  1997年   100篇
  1996年   104篇
  1995年   84篇
  1994年   62篇
  1993年   52篇
  1992年   36篇
  1991年   36篇
  1990年   33篇
  1989年   27篇
  1987年   12篇
  1986年   16篇
  1985年   12篇
  1984年   18篇
  1979年   12篇
  1966年   10篇
  1964年   15篇
  1963年   16篇
  1961年   16篇
  1960年   11篇
  1959年   10篇
  1958年   10篇
  1957年   14篇
  1955年   18篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
This study examined the mediating role of health behaviors in the relationship between neuroticism and depressive symptoms among spouse caregivers. Path analysis was used to test a model of the caregiver stress process among 233 caregivers of people with dementia. Results indicate that neuroticism has a significant direct effect on depressive symptoms and also indirectly influences depressive symptoms through health behaviors and perceived stress. When individual health behaviors were examined in the path model, only physical activity served a significant mediating role. These findings suggest that neuroticism may lead to depressive symptoms among caregivers partly through declines in physical activity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
22.
In asynchronous transfer mode (ATM) networks, fixed length cells of 53 bytes are transmitted. A cell may be discarded during transmission due to buffer overflow or a detection of errors. Cell discarding seriously degrades transmission quality. The quality degradation can be reduced by employing efficient forward error control (FEC) to recover discarded cells. In this paper, we present the design and implementation of decoding equipment for FEC in ATM networks based on a single parity check (SPC) product code using very‐large‐scale integration (VLSI) technology. FEC allows the destination to reconstruct missing data cells by using redundant parity cells that the source adds to each block of data cells. The functionality of the design has been tested using the Model Sim 5.7cXE Simulation Package. The design has been implemented for a 5 ° 5 matrix of data cells in a Virtex‐E XCV 3200E FG1156 device. The simulation and synthesis results show that the decoding function can be completed in 81 clock cycles with an optimum clock of 56.8 MHz. A test bench was written to study the performance of the decoder, and the results are presented.  相似文献   
23.
中国工程勘察设计咨询业产业整合的路径选择   总被引:2,自引:0,他引:2  
产业是由具有相互联系、相互制约的若干组成部分结合在一起并且有特定动能的有机体,产业分工越合理,资金、人力资源和各种自然资源与物质资料在产业内发挥的功能越大;中国工程勘察设计业的产业结构“中间大,两头小”,产业内部资源分布极不合理;结构调整的最佳选择是以工程项目总承包和分包为分工协作的垂直一体化:分化重组中间的工程咨询单位,组建顶端的EPC工程公司,发展低端的专业咨询公司、事务所。  相似文献   
24.
The authors examined predictors of teachers' ratings of academic competence of 105 kindergarten children from low-income families. Teachers rated target children's expected competence in literacy and math and completed questions about their perceptions of congruence-dissonance between themselves and the child's parents regarding education-related values. Independent examiners assessed children's literacy and math skills. Teachers' instructional styles were observed and rated along dimensions of curriculum-centered and student-centered practices. Controlling for children's skills and socioeconomic status, teachers rated children as less competent when they perceived value differences with parents. These patterns were stronger for teachers who exhibited curriculum-centered, rather than student-centered, practices. The findings suggest a mechanism by which some children from low-income families enter a path of diminished expectations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
25.
This research reports age and gender differences in cardiac reactivity and subjective responses to the induction of autobiographical memories related to anger, fear, sadness, and happiness. Heart rate (HR) and subjective state were assessed at baseline and after the induction of each emotion in 113 individuals (61 men, 52 women; 66% European American, 34% African American) ranging in age from 15 to 88 years (M = 50.0; SD = 20.2). Cardiac reactivity was lower in older individuals; however, for anger and fear, these age effects were significantly more pronounced for the women than the men. There were no gender differences in subjective responses, however, suggesting that the lower cardiac reactivity found among older people is dependent on gender and the specific emotion assessed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
26.
This study unites investigations into the linguistic relativity of color categories with research on children's category acquisition. Naming, comprehension, and memory for colors were tracked in 2 populations over a 3-year period. Children from a seminomadic equatorial African culture, whose language contains 5 color terms, were compared with a group of English children. Despite differences in visual environment, language, and education, they showed similar patterns of term acquisition. Both groups acquired color vocabulary slowly and with great individual variation. Those knowing no color terms made recognition errors based on perceptual distance, and the influence of naming on memory increased with age. An initial perceptually driven color continuum appears to be progressively organized into sets appropriate to each culture and language. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
27.
The authors report a meta-analysis of age differences in everyday problem-solving/decision-making effectiveness (EPSE). Effect sizes were calculated to reflect 3 age group comparisons: old versus young, young versus middle-aged, and middle-aged versus old. Findings from the meta-analysis of 28 separate studies with an aggregate of 4,482 participants do not support theories of preserved EPSE in late adulthood. Although significant age differences of moderate magnitude persisted across methodological and theoretical domains, rating criteria (experimenter vs. participant) emerged as a significant moderator of the effect magnitude and direction. In addition, EPSE in older adults was bolstered when problem content was interpersonal and when samples were highly educated. Finally, the current results support the conceptual integration of findings from the everyday problem-solving and everyday decision-making literatures. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
28.
Triple tangent flank milling of ruled surfaces   总被引:3,自引:0,他引:3  
This paper presents a positioning strategy for flank milling ruled surfaces. It is a modification of a positioning method developed by Bedi et al. [Comput Aided Des 35 (2003) 293]. A cylindrical cutting tool is initially positioned tangential to the two boundary curves on a ruled surface. Optimization is used to move these tangential points to different curves on the ruled surface to reduce the error. A second optimization step is used to additionally make the tool tangent to a rule line, further reducing the error and resulting in a tool position, where the tool is positioned tangential to two guiding rails and one rule line. The resulting surface has 88% less under cutting than the method of Bedi et al.  相似文献   
29.
Structural equation modeling was used to test the mediational role of social environmental selection on alcohol use in cross-sectional samples of 447 students from a rural state university and 421 students from an urban private university. Results showed that male gender, White ethnicity, and sensation seeking were uniquely associated with greater alcohol use. Mediational analyses indicated that socioenvironmental factors (i.e., Greek involvement, friends' approval of drinking/getting drunk) were positively associated with alcohol use and significantly accounted for parts of the effects of ethnicity and sensation seeking, but not gender, on alcohol use. Results suggest that White students and those high on sensation seeking may drink more heavily in college, in part because they select social environments in which alcohol use is encouraged. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
30.
The present studies demonstrated the moderation of self-construal orientation on mimicry. Recent research has indicated that an interdependent self-construal is associated with assimilation of the other to the self whereas an independent self-construal is associated with minimizing the influence of others on the self (H. R. Markus & S. Kitayama, 1991; D. Stapel & W. Koomen, 2001). Therefore, the authors hypothesized that an interdependent self-construal would be associated with more mimicry than an independent self-construal. When self-construal orientations were experimentally primed. as in Studies 1 and 2, independent self-construals produced less nonconscious mimicry than interdependent self-construals. When self-construals were examined as cultural differences with either a chronically dominant independent (Americans) or interdependent (Japanese) construal of the self, these results were replicated. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
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