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   4421篇
  免费   327篇
  国内免费   7篇
电工技术   22篇
综合类   6篇
化学工业   1431篇
金属工艺   29篇
机械仪表   75篇
建筑科学   184篇
矿业工程   5篇
能源动力   92篇
轻工业   857篇
水利工程   43篇
石油天然气   16篇
无线电   218篇
一般工业技术   555篇
冶金工业   720篇
原子能技术   30篇
自动化技术   472篇
  2024年   8篇
  2023年   50篇
  2022年   208篇
  2021年   342篇
  2020年   158篇
  2019年   152篇
  2018年   151篇
  2017年   145篇
  2016年   151篇
  2015年   157篇
  2014年   191篇
  2013年   291篇
  2012年   259篇
  2011年   332篇
  2010年   243篇
  2009年   240篇
  2008年   240篇
  2007年   221篇
  2006年   159篇
  2005年   128篇
  2004年   131篇
  2003年   113篇
  2002年   98篇
  2001年   38篇
  2000年   52篇
  1999年   47篇
  1998年   48篇
  1997年   34篇
  1996年   38篇
  1995年   32篇
  1994年   35篇
  1993年   29篇
  1992年   20篇
  1991年   9篇
  1990年   19篇
  1989年   20篇
  1988年   24篇
  1987年   22篇
  1986年   18篇
  1985年   15篇
  1984年   7篇
  1983年   9篇
  1982年   14篇
  1981年   11篇
  1979年   11篇
  1978年   8篇
  1977年   3篇
  1973年   4篇
  1965年   2篇
  1955年   2篇
排序方式: 共有4755条查询结果,搜索用时 15 毫秒
991.
This study was designed to assess one of the major assumptions of current language learning theories: Adults ignore children's speech errors. We observed both parents (n?=?16) and nonparent adults (n?=?13) conversing with children and examined the conversations for evidence of adults' differential responding to the children's syntactic, phonological, and semantic errors. Results indicated that adults were more likely to repeat verbatim a well-formed sentence than an ill-formed sentence. In contrast, adults were more likely to repeat with changes, or request clarification of, a sentence containing syntactic or phonological errors than well-formed sentences. Adults also more frequently used the correct syntactic or phonological form in the immediately subsequent sentence if the child's preceding sentence contained only one syntactic or phonological error rather than multiple errors. Overall, the results indicate that all adults tend to respond differentially to children's language mistakes, with parents showing greater sensitivity than adults who are not parents. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
992.
In 3 studies, male and female brown lemmings were either isolated at weaning (18 days) or then housed with siblings for another 10 days before being isolated. Before testing for sexual behavior at the age of 75–103 days, half of each group of males received a series of exposures to estrous females and half of each group of females was housed with a stud male. The results of mating tests indicate that whereas prior sexual experience facilitated subsequent copulatory behavior in both sexes, prepubertal interactions subsequently facilitated contact social and sexual behavior in males but did not increase the behavioral scores of females, who engaged in high levels of sexual behavior regardless of prepubertal experience. The effect of prior copulatory activity on male sexual performance could not be attributed to increasing age (i.e., maturational processes) because the behavior of males tested once but at different ages did not differ appreciably. Prepubertal social interaction appeared to predispose males to benefit from sexual experience later in life. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
993.
Investigated the interaction between postural regulation and spatial processing by having 24 college students perform L. R. Brooks's (see record 1968-04936-001) spatial and nonspatial memory tasks either while sitting or while maintaining a difficult standing balance position. The balance task disrupted spatial but not nonspatial memory performance. Balance steadiness during spatial and nonspatial memory conditions did not differ. Results suggest that cognitive spatial processing may rely on neural mechanisms that are also required for the regulation of posture. Findings support the idea that spatial processing may rely on phylogenetically older systems. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
994.
In bakeries, it is important that successive batches of dough (‘doughs’) for the same product have the same temperature. Dough temperature can be controlled by adjusting the temperature of the water to be used. An automatic calculator for the required water temperature was designed on the basis of the assumption that the final dough temperature is a linear function of flour, water and bakery temperatures.This paper describes a physical model which predicts the values of the coefficients and of the constant term in this linear relationship. The decrease in dough viscosity with increasing temperature is an essential part of the model.It is argued that this effect of temperature on dough viscosity reduces the effects of flour and water temperatures on the final dough temperature. Heat transfer between the dough and the air in the bakery also reduces their effects, but is, under normal mixing conditions, less important than the effect of temperature on dough viscosity; only with small doughs and with slow and long mixing is it more important.  相似文献   
995.
The products obtained from the roomtemperature reaction of ammonium bifluoride and zirconium fluoride monohydrate are ammonium heptafluorozirconate ((NH4)3ZrF2), liquid water, and hydrogen fluoride. Ammonium bifluoride and zirconium fluoride monohydrate were reacted prior to glass batching, producing dry ammonium heptafluorozirconate which was used to prepare a high-quality ZBLAN fluoride glass.  相似文献   
996.
997.
Recent reviews of the training literature have advocated directly manipulating self-efficacy in an attempt to improve the motivation of trainees. However, self-regulation theories conceive of motivation as a function of various goal processes, and assert that the effect of self-efficacy should depend on the process involved. Training contexts may evoke planning processes in which self-efficacy might negatively relate to motivation. Yet the typical between-persons studies in the current literature may obscure the effect. To examine this issue, 63 undergraduate students completed a series of questionnaires measuring self-efficacy and motivation before 5 class exams. Self-efficacy was negatively related to motivation and exam performance at the within-person level of analysis, despite a significant positive relation with performance at the between-persons level. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
998.
The Campagna Romana, a landscape of unrivalled historical and cultural importance, can be subdivided into three main sectors, characterised by different plant communities, climate, geology and impact of man; these are the west sector, the river Tiber and the east sector. This landscape typology is a striking example of man-environment interaction: its primary source is in different climatic and geological conditions of these three sectors , but it was strongly reinforced by different land use. The western sector has been conserved in a semi-natural state until recent times while the eastern sector, characterised by communities influenced by man and ruins, has been almost completely devoid of woody vegetation probably since the Roman Empire.  相似文献   
999.
This study estimates the economic benefits of remediation in the Sheboygan River, WI Area of Concern (AOC) using two distinct empirical methods. The methodology parallels that described by Braden et al. (2008). The results are mixed. Using hedonic analysis of property sales, for owner-occupied homes within a 5-mile radius of the Sheboygan River AOC, the overall estimated loss of value is $158 million (8% of market value). Of this total, only $49 million in losses for homes closest to the upper river segment has strong statistical support. The impacts are greatest proportionally for properties closest to the AOC. A survey-based method yields a mean estimate of $218 million (10% of property value) in willingness to pay for full cleanup of the AOC. If remediation were to induce recovery of property values, then the local communities could benefit through increased property tax revenues.  相似文献   
1000.
The Wechsler Intelligence Scale for Children—Revised (WISC—R) was factor analyzed on a sample of 368 hard-of-hearing and deaf children (aged 6–16 yrs). Two factors emerged and were labeled Language Comprehension and Visual-Spatial Organization. The factor structure for the hard-of-hearing (n?=?77) and deaf (n?=?291) groups was identical. Deaf children of deaf parents earned significantly higher Verbal IQ and Performance IQ scores than did deaf children of hearing parents. There were no differences in IQ or subtest scores in interpreted vs signed administrations. Implications for assessing the cognitive abilities of hearing-impaired children are discussed. (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