全文获取类型
收费全文 | 3575篇 |
免费 | 130篇 |
专业分类
电工技术 | 27篇 |
综合类 | 1篇 |
化学工业 | 709篇 |
金属工艺 | 50篇 |
机械仪表 | 33篇 |
建筑科学 | 172篇 |
矿业工程 | 4篇 |
能源动力 | 60篇 |
轻工业 | 510篇 |
水利工程 | 43篇 |
石油天然气 | 12篇 |
无线电 | 151篇 |
一般工业技术 | 442篇 |
冶金工业 | 1152篇 |
原子能技术 | 8篇 |
自动化技术 | 331篇 |
出版年
2023年 | 26篇 |
2022年 | 72篇 |
2021年 | 114篇 |
2020年 | 60篇 |
2019年 | 69篇 |
2018年 | 90篇 |
2017年 | 75篇 |
2016年 | 99篇 |
2015年 | 55篇 |
2014年 | 97篇 |
2013年 | 208篇 |
2012年 | 165篇 |
2011年 | 231篇 |
2010年 | 173篇 |
2009年 | 177篇 |
2008年 | 184篇 |
2007年 | 181篇 |
2006年 | 149篇 |
2005年 | 146篇 |
2004年 | 95篇 |
2003年 | 93篇 |
2002年 | 104篇 |
2001年 | 68篇 |
2000年 | 68篇 |
1999年 | 66篇 |
1998年 | 54篇 |
1997年 | 51篇 |
1996年 | 68篇 |
1995年 | 47篇 |
1994年 | 54篇 |
1993年 | 49篇 |
1992年 | 43篇 |
1991年 | 17篇 |
1990年 | 37篇 |
1989年 | 38篇 |
1988年 | 36篇 |
1987年 | 28篇 |
1986年 | 30篇 |
1985年 | 28篇 |
1984年 | 30篇 |
1983年 | 22篇 |
1982年 | 22篇 |
1981年 | 23篇 |
1980年 | 14篇 |
1979年 | 17篇 |
1978年 | 17篇 |
1977年 | 10篇 |
1976年 | 11篇 |
1975年 | 14篇 |
1974年 | 14篇 |
排序方式: 共有3705条查询结果,搜索用时 0 毫秒
11.
Self-efficacy expectations predict survival for patients with chronic obstructive pulmonary disease.
Kaplan Robert M.; Ries Andrew L.; Prewitt Lela M.; Eakin Elizabeth 《Canadian Metallurgical Quarterly》1994,13(4):366
Evaluated the validity of self-efficacy expectations as predictors of mortality for 119 patients with chronic obstructive pulmonary disease. Ss completed 4 physiological measures that represent common clinical indicators of disease severity: forced expiratory volume in 1 s(FEV1.0), arterial blood gas measurement of resting partial pressure of oxygen (PaO?), single-breath diffusing capacity (DLCO), and maximum oxygen uptake (V02max) during exercise. In addition, self-reported self-efficacy expectation for walking on a treadmill was measured. Self-efficacy was a significant univariate predictor of 5-yr survival. However, when controlling for FEV1.0 in multivariate survival analysis, self-efficacy had only a marginal effect. Simple self-report scales may provide significant information about health status. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
12.
Twenty-one 15- to 17-year-olds attempted to purchase cigarettes in 232 stores in the manner that confederates typically do in access studies, as well as in the manipulative ways (e.g., lying about their ages) that youth smokers do, thereby modeling youth access to tobacco within versus outside of studies, respectively. Youth typical-research versus manipulative behavior was contrasted with clerk behavior (requests for youth ID cards) to examine the relative contributions of both to youth access to tobacco for the 1st time. Results revealed that clerk behavior was the strongest predictor of cigarette sales to youth and hence underscore the need for interventions with merchants. Sales nonetheless were higher under youth-manipulative conditions and thereby highlight the low ecological validity of access research. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
13.
Elizabeth J. Opila Nathan S. Jacobson Dwight L. Myers Evan H. Copland 《JOM Journal of the Minerals, Metals and Materials Society》2006,58(1):22-28
The importance of understanding and predicting the interactions of oxides with water vapor at high temperatures is demonstrated
in this article. Methods for observing volatilization phenomena and identifying the chemical formulae for volatile metal hydroxides
are discussed. In addition, techniques for obtaining accurate thermodynamic data for gaseous metal hydroxide species are described.
Detailed examples of the stability of the principle structural and/or protective oxides chromia (Cr2O3), silica (SiO2), and alumina (Al2O3) in high-temperature water vapor are included. 相似文献
14.
In long-term memory, negative information is better remembered than neutral information. Differences in processes important to working memory may contribute to this emotional memory enhancement. To examine the effect that the emotional content of stimuli has on working memory performance, the authors asked participants to perform working memory tasks with negative and neutral stimuli. Task accuracy was unaffected by the emotional content of the stimuli. Reaction times also did not differ for negative relative to neutral words, but on an n-back task using faces, participants were slower to respond to fearful faces than to neutral faces. These results suggest that although emotional content does not have a robust effect on working memory, in some instances emotional salience can impede working memory performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
15.
Schulz Laura E.; Bonawitz Elizabeth Baraff; Griffiths Thomas L. 《Canadian Metallurgical Quarterly》2007,43(5):1124
Causal learning requires integrating constraints provided by domain-specific theories with domain-general statistical learning. In order to investigate the interaction between these factors, the authors presented preschoolers with stories pitting their existing theories against statistical evidence. Each child heard 2 stories in which 2 candidate causes co-occurred with an effect. Evidence was presented in the form: AB→E; CA→E; AD→E; and so forth. In 1 story, all variables came from the same domain; in the other, the recurring candidate cause, A, came from a different domain (A was a psychological cause of a biological effect). After receiving this statistical evidence, children were asked to identify the cause of the effect on a new trial. Consistent with the predictions of a Bayesian model, all children were more likely to identify A as the cause within domains than across domains. Whereas 3.5-year-olds learned only from the within-domain evidence, 4- and 5-year-olds learned from the cross-domain evidence and were able to transfer their new expectations about psychosomatic causality to a novel task. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
16.
Ss (aged 52–83 yrs) named 30 famous people 4 times over the course of an hour and responded to 2 targets (a beard and a pipe) by marking the trial number on the response sheet. Initial performance in the prospective memory task was related only to a measure of incidental learning. Subsequent forgetting (i.e., success followed by failure) occurred more often for older Ss than for younger Ss, but there was no difference between the age groups in recovery (i.e., failure followed by success). Forgetting was predicted by age, even after a composite measure of general ability was included in the regression. Recovery was related to general ability alone. Results both replicate and extend those from a reanalysis of a previous study (E. A. Maylor, 1990). They provide a striking contrast with the effect of age on retrospective memory, namely, age-related impairment on initial performance but no effect of age on subsequent forgetting. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
17.
18.
Repression is one of the most haunting concepts in psychology. Something shocking happens, and the mind pushes it into some inaccessible corner of the unconscious. Later, the memory may emerge into consciousness. Repression is one of the foundation stones on which the structure of psychoanalysis rests. Recently there has been a rise in reported memories of childhood sexual abuse that were allegedly repressed for many years. With recent changes in legislation, people with recently unearthed memories are suing alleged perpetrators for events that happened 20, 30, even 40 or more years earlier. These new developments give rise to a number of questions: (1) How common is it for memories of child abuse to be repressed? (2) How are jurors and judges likely to react to these repressed memory claims? (3) When the memories surface, what are they like? and (4) How authentic are the memories? (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
19.
Elizabeth Van Couvering 《Journal of Computer-Mediated Communication》2007,12(3):866-887
In the face of rising controversy about search engine results—that they are too restrictive, too comprehensive, lacking in certain areas, over-represented in others—this article presents the results of in-depth interviews with search engine producers, examining their conceptions of search engine quality and the implications of those conceptions. Structuration theory suggests that the cultural schemas that frame these discourses of quality will be central in mobilizing resources for technological development. The evidence presented here suggests that resources in search engine development are overwhelmingly allocated on the basis of market factors or scientific/technological concerns. Fairness and representativeness, core elements of the journalists' definition of quality media content, are not key determiners of search engine quality in the minds of search engine producers. Rather, alternative standards of quality, such as customer satisfaction and relevance, mean that tactics to silence or promote certain websites or site owners (such as blacklisting, whitelisting, and index "cleaning") are seen as unproblematic. 相似文献
20.