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   36266篇
  免费   1364篇
  国内免费   63篇
电工技术   371篇
综合类   29篇
化学工业   7236篇
金属工艺   725篇
机械仪表   738篇
建筑科学   1963篇
矿业工程   114篇
能源动力   1054篇
轻工业   2883篇
水利工程   430篇
石油天然气   117篇
武器工业   5篇
无线电   2475篇
一般工业技术   6113篇
冶金工业   6598篇
原子能技术   268篇
自动化技术   6574篇
  2023年   214篇
  2022年   440篇
  2021年   683篇
  2020年   463篇
  2019年   617篇
  2018年   780篇
  2017年   694篇
  2016年   833篇
  2015年   757篇
  2014年   1040篇
  2013年   2372篇
  2012年   1680篇
  2011年   2091篇
  2010年   1651篇
  2009年   1547篇
  2008年   1800篇
  2007年   1774篇
  2006年   1591篇
  2005年   1439篇
  2004年   1174篇
  2003年   1122篇
  2002年   1051篇
  2001年   702篇
  2000年   549篇
  1999年   595篇
  1998年   583篇
  1997年   574篇
  1996年   549篇
  1995年   572篇
  1994年   525篇
  1993年   510篇
  1992年   500篇
  1991年   288篇
  1990年   418篇
  1989年   389篇
  1988年   319篇
  1987年   355篇
  1986年   310篇
  1985年   418篇
  1984年   416篇
  1983年   318篇
  1982年   295篇
  1981年   281篇
  1980年   269篇
  1979年   270篇
  1978年   247篇
  1977年   225篇
  1976年   206篇
  1975年   194篇
  1974年   173篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
Construction productivity has been on the decline in the last decade. The results are presented on a survey of the Engineering News‐Record 400 largest contractors to obtain their views on where productivity improvements would most help and to compare the trends with a similar survey carried out in 1979. Data were collected on the general company characteristics of the responding contractors, and on the contractors' opinions on potential areas for productivity improvement in the office and in the field. Findings indicate that immediate research should concentrate on improving marketing practices, planning and scheduling, labor‐management relations, site supervision, industrialized building systems, equipment policy and engineering design; and that governmental regulations have lost the immediate urgency attached to them in 1979.It is also recommended that similar surveys be conducted every 3 to 4 years to identify new trends and to steer research in the appropriate direction.  相似文献   
132.
Piaget believed that young children were egocentric and would ascribe their own knowledge to another. In contrast, Wimmer, Hogrefe, and Perner (1988) found that children did not perform egocentrically when assessing another's knowledge. The present study was carried out to determine which claim was right. A familiar object was secretly placed in a box, and a child and others either looked in the box or did not look. Two of the main findings were that (a) 6-year-olds were significantly better than 3- to 4-year-olds at assessing the other's knowledge, even though both assessed the other's perception correctly (p?p?  相似文献   
133.
134.
The view of iconic memory as a precategorical, high-capacity, quickly decaying visible memory has recently come under attack (e.g., M. Coltheart, 1980). Distinctions have been drawn between visible persistence, or the phenomenal trace of an extinguished stimulus, and informational persistence, knowledge about the visual properties of the stimulus. Two alternative conceptions of informational persistence were tested in 3 experiments with 13 university students and the present authors. One conception is that visual information persists in a visual memory that begins at stimulus offset and lasts for 150–300 msec, independently of exposure duration. The 2nd conception is that informational persistence arises from a nonvisual memory that contains spatial coordinates for displayed items along with identity codes for those items. In the experiments, 3?×?3 letter arrays were presented for durations ranging from 50 to 500 msec. A single character mask presented at varying intervals after array offset cued report of an entire row of the array. Comparison of the cued row's masked and unmasked letters revealed that spatially specific visual (i.e., maskable) information persisted after stimulus offset, regardless of exposure duration. This result favors the visual conception of informational persistence. There was also support, however, for the nonvisual conception: Accuracy increased and item intrusion errors decreased as stimulus duration increased. Implications for models of informational persistence and for transsaccadic integration during reading are discussed. (47 ref) (PsycINFO Database Record (c) 2011 APA, all rights reserved)  相似文献   
135.
136.
137.
J. E. Grusec and J. J. Goodnow (see record 1994-25033-001) provided a compelling framework for organizing parameters of disciplinary encounters found to affect moral internalization. However, their central hypothesis (that cognitions of accurate perception and acceptance of the message mediate the impact of specific tactics on internalization) remains untested. Before embarking on research programs designed to reveal the determinants of acceptance of parental messages in the hope that such research will inform our understanding of internalization, researchers would be well advised to devise conceptually sound measures of message acceptance and to show that message acceptance does indeed mediate internalization. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
138.
Using TAT data collected prior to entering management positions, sex differences in motive patterns related to leadership were examined in a 12-yr longitudinal study of 211 men and 180 women (aged 21–43 yrs at initial assessment) who entered a large utility corporation between 1977 and 1982. Ss were followed up in 1990 and recorded as to how far they had advanced in management level. While the results showed no sex differences in motivational predictors of attained management level, the content analysis revealed 2 distinct styles of power-related themes that distinguished the successful men from the successful women. The successful male managers were more likely to use reactive power themes while the successful female managers were more likely to use resourceful power themes. Differences between the sexes in the power themes were less pronounced among the managers who had remained in lower levels of management. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
139.
Evaluated the contributions of strategic and data-driven factors to skilled performance by manipulating the predictability of the class of stimuli used in a memory search task. In Exp 1, when consistent mapping (CM) and varied mapping (VM) conditions were blocked, large performance differences were observed; however, when CM and VM trials were mixed, performance differences were reduced. In Exp 2, mixed training led to a less skilled performance than blocked training. Moreover, transfer conditions revealed a critical interval for learning to adopt and deploy differential response strategies. Exp 3 demonstrated that the differential response strategies were not stimulus specific. Analysis suggests that skilled performance can be conceptualized as an interaction between enhanced evidence accumulation and strategic setting of response criteria. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
140.
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