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   3805篇
  免费   239篇
  国内免费   2篇
电工技术   17篇
综合类   6篇
化学工业   983篇
金属工艺   46篇
机械仪表   29篇
建筑科学   165篇
矿业工程   4篇
能源动力   91篇
轻工业   585篇
水利工程   37篇
石油天然气   22篇
武器工业   1篇
无线电   207篇
一般工业技术   678篇
冶金工业   707篇
原子能技术   30篇
自动化技术   438篇
  2023年   16篇
  2022年   74篇
  2021年   141篇
  2020年   66篇
  2019年   67篇
  2018年   96篇
  2017年   116篇
  2016年   116篇
  2015年   107篇
  2014年   157篇
  2013年   219篇
  2012年   224篇
  2011年   259篇
  2010年   197篇
  2009年   186篇
  2008年   199篇
  2007年   194篇
  2006年   181篇
  2005年   129篇
  2004年   111篇
  2003年   109篇
  2002年   97篇
  2001年   82篇
  2000年   53篇
  1999年   69篇
  1998年   133篇
  1997年   83篇
  1996年   60篇
  1995年   40篇
  1994年   52篇
  1993年   51篇
  1992年   33篇
  1991年   29篇
  1990年   36篇
  1989年   31篇
  1988年   25篇
  1987年   25篇
  1986年   18篇
  1985年   26篇
  1984年   9篇
  1983年   22篇
  1982年   12篇
  1981年   7篇
  1980年   17篇
  1978年   6篇
  1977年   13篇
  1976年   9篇
  1975年   6篇
  1974年   7篇
  1973年   8篇
排序方式: 共有4046条查询结果,搜索用时 312 毫秒
1.
2.
The present concurrent study combined developmental and ecological considerations to examine the unique contribution of multiple preschool competencies to an indicator of early academic success. Participants included 195 Head Start children from 32 classrooms representative of a large, urban Head Start program. Dimensional (variable-centered) analyses revealed 3 distinct classroom competency dimensions (i.e., General Classroom Competencies, Specific Approaches to Learning, and Interpersonal Classroom Behavioral Problems). The first 2 of these dimensions were found to be uniquely associated with early academic success. Findings from typological (person-centered) analyses supported the dimensional findings. Typological analyses revealed 7 profiles of classroom competency distinguished by high scores on the dimensions of General Competencies and Approaches to Learning, and these profiles were found to relate differentially to the indicator of early academic success. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
3.
Carcinoma of the prostate, that is adenocarcinoma, is one of the most common malignancies in the male with an estimated incidence for 1991 of 122,000 new cases. On the other hand, squamous cell carcinoma of the prostate, with a median incidence of .5%-1% of all prostatic malignancies, has a similar clinical presentation but differs in treatment response and prognosis. We herein present one case of this histological pattern and review the literature pertaining to it.  相似文献   
4.
For many companies, productivity improvements are the watchwords of the 1990s. IS organizations are having to demonstrate increased productivity on an annual basis. For the end-user computing (EUC) department, this requirement often comes in addition to the request to quantify the services it provides, presenting the EUC manager with the proverbial nightmare of juggling two number-one priorities. Which should receive the highest attention? The savvy manager recognizes that the correct answer is both.  相似文献   
5.
The thermal evolution of defects produced by ion irradiation is studied by kinetic Monte Carlo and Rate Theory approaches. An isochronal annealing is simulated to evidence the different thermally activated mechanisms that govern defect evolution. KMC simulations show that in the case of ion irradiation, additional recovery peaks should be expected, in comparison to electron irradiation conditions. A comparison between kMC and RT results indicates that some of these peaks are due to spatially – correlated recombinations that occur at low temperature. Therefore kMC and RT approaches differ at low temperature. However, at higher temperature results obtained by both models are in near perfect agreement. In addition, we studied the influence of vacancy cluster mobility on the evolution of damage. KMC simulations show that the mobility of V2, V3 and V4 clusters does not significantly affect the evolution of defects and can be neglected in these conditions.  相似文献   
6.
A population from a Central Spanish region (Tormes-Alberche Valley) has been investigated for the presence of red-green colour vision defects. A sample of 998 subjects (469 male and 529 female) was analyzed. To identify colour vision defects, Ishihara test plates were used. The red-green colour blindness percentage obtained was 4.69 +/- 0.976% for males (2.13% protan and 2.56% deutan types) and none of the females tested were found to be colour blind. These results are within the variation range of Mediterranean populations and lower than the usual frequencies among non-Mediterranean European samples.  相似文献   
7.
In a conceptual replication of A. Biglan et al (see record 1989-39898-001), 288 Ss rated their emotional and behavioral responses to aggressive, distressed, and neutral behaviors. The stimulus behaviors occurred in the context of casual relationships and were portrayed by male and female actors. Consistent with Biglan et al, it was found that aggressive behaviors evoked angry emotions and negative behavioral responses; distressed behaviors evoked both angry and concerned emotions and supportive behavioral responses. However, in contrast to the original results, evidence was also found of negative (primarily avoidant) behavioral responses to distressed behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
8.
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   
9.
This article reports research intended to assess and extend a recent theory of peer responses to low-performing team members (J. A. LePine & L. Van Dyne, 2001a). An instrument that assesses 4 types of peer responses to low performers (compensating for, training, motivating, and rejecting) was developed and then cross-validated in a subsequent study. Results of the study supported the validity of the peer responses measure and were generally consistent with the attributional theory of peer responses. Low-performer characteristics influenced the peer responses. These effects were mediated in part by peer attributions, affect, and cognitions, which explained variance in the peer responses over and above the variance explained by respondents' personality characteristics (i.e., The Big Five). (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
10.
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