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   32547篇
  免费   1615篇
  国内免费   34篇
电工技术   338篇
综合类   58篇
化学工业   6916篇
金属工艺   598篇
机械仪表   588篇
建筑科学   1915篇
矿业工程   78篇
能源动力   888篇
轻工业   2713篇
水利工程   297篇
石油天然气   166篇
武器工业   3篇
无线电   2372篇
一般工业技术   5992篇
冶金工业   5604篇
原子能技术   213篇
自动化技术   5457篇
  2023年   253篇
  2022年   348篇
  2021年   694篇
  2020年   510篇
  2019年   593篇
  2018年   728篇
  2017年   694篇
  2016年   912篇
  2015年   817篇
  2014年   1034篇
  2013年   1948篇
  2012年   1698篇
  2011年   2145篇
  2010年   1523篇
  2009年   1484篇
  2008年   1794篇
  2007年   1666篇
  2006年   1457篇
  2005年   1246篇
  2004年   1107篇
  2003年   963篇
  2002年   924篇
  2001年   561篇
  2000年   536篇
  1999年   557篇
  1998年   587篇
  1997年   493篇
  1996年   498篇
  1995年   459篇
  1994年   440篇
  1993年   455篇
  1992年   395篇
  1991年   238篇
  1990年   332篇
  1989年   331篇
  1988年   282篇
  1987年   309篇
  1986年   296篇
  1985年   321篇
  1984年   278篇
  1983年   265篇
  1982年   241篇
  1981年   220篇
  1980年   185篇
  1979年   190篇
  1978年   180篇
  1977年   142篇
  1976年   145篇
  1975年   148篇
  1974年   116篇
排序方式: 共有10000条查询结果,搜索用时 421 毫秒
131.
A new Eu-endohedral fullerene cage, namely, Eu@C72, was synthesized, separated, and a single isomer, Eu@C72-I, has been isolated by multi-step HPLC for the first time and characterized by LDI-TOF mass spectrometry, UV-Vis and EPR spectroscopy. Additionally, a second isomer, Eu@C72-II, has been separated by HPLC and identified by LDI-TOF mass spectrometry.  相似文献   
132.
133.
Longitudinal analyses on normal versus impaired functioning across 7 domains were conducted in children who had experienced profound institutional deprivation up to the age of 42 months and were adopted from Romania into U.K. families. Comparisons were made with noninstitutionalized children adopted from Romania and with nondeprived within-U.K. adoptees placed before the age of 6 months. Specifically, the validity of the assessment, the degree of continuity and change in levels of functioning from 6 to 11 years, and the factors in the pre- and postadoption environment accounting for heterogeneity in outcome were examined. Pervasive impairment was significantly raised in children experiencing institutional deprivation for ≥6 months of life, with a minority within this group showing no impairment. There was no additional significant effect of duration of deprivation beyond the 6-month cutoff, and few other predictors explained outcome. The pattern of normality/impairment was mainly established by 6 years of age, with considerable continuity at the individual level between 6 and 11 years. The findings are discussed in terms of the possibility of a sensitive period for development. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
134.
This study examined organizational family-responsive policies, perceptions of the organization as family supportive, and supervisor support as issues that may be salient to the experience of conflict between paid employment (work) and family roles. Data were collected from 355 managerial personnel in New Zealand. Although work-family conflict and psychological strain were strongly linked, the availability of organizational policies had no significant association with levels of conflict or strain, whereas policy usage was related only to work-to-family interference and not to family-to-work interference. On the other hand, perceptions of the organization as family supportive and supervisor support for work-family balance displayed significant relationships with key variables, highlighting the importance of these variables for interventions designed to ameliorate the negative impact of work-family conflict on managerial well-being. Implications for the effective implementation of family-responsive interventions are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
135.
136.
Many regulators use benchmarking as part of the incentive-based regulation of natural monopolies so as to reduce the possibilities for gaming. However, the use of benchmarking can lead firms to pursue virtual rather than true performance improvements by gaming the regulator’s benchmarking in a number of ways that are contrary to the intentions of the scheme.  相似文献   
137.
138.
The time course of spoken word recognition depends largely on the frequencies of a word and its competitors, or neighbors (similar-sounding words). However, variability in natural lexicons makes systematic analysis of frequency and neighbor similarity difficult. Artificial lexicons were used to achieve precise control over word frequency and phonological similarity. Eye tracking provided time course measures of lexical activation and competition (during spoken instructions to perform visually guided tasks) both during and after word learning, as a function of word frequency, neighbor type, and neighbor frequency. Apparent shifts from holistic to incremental competitor effects were observed in adults and neural network simulations, suggesting such shifts reflect general properties of learning rather than changes in the nature of lexical representations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
139.
Fodor and Pylyshyn (1988) have argued that the cognitive architecture is not Connectionist. Their argument takes the following form: (1) the cognitive architecture is Classical; (2) Classicalism and Connectionism are incompatible; (3) therefore the cognitive architecture is not Connectionist. In this essay I argue that Fodor and Pylyshyn's defenses of (1) and (2) are inadequate. Their argument for (1), based on their claim that Classicalism best explains the systematicity of cognitive capacities, is an invalid instance of inference to the best explanation. And their argument for (2) turns out to be question-begging. The upshot is that, while Fodor and Pylyshyn have presented Connectionists with the important empirical challenge of explaining systematicity, they have failed to provide sufficient reason for inferring that the cognitive architecture is Classical and not Connectionist.  相似文献   
140.
Modulo scheduling theory can be applied successfully to overlap Fortran DO loops on pipelined computers issuing multiple operations per cycle both with and without special loop architectural support. This paper shows that a broader class of loops—REPEAT-UNTIL, WHILE, and loops with more than one exit, in which the trip count is not known beforehand—can also be overlapped efficiently on multiple-issue pipelined machines. The approach is described with respect to a specific machine model, but it can be extended to other models. Special features in the architecture, as well as compiler representations for accelerating these loop constructs, are discussed. Performance results are presented for a few select examples.An earlier version of this paper was presented at Supercomputing '90.  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