全文获取类型
收费全文 | 31856篇 |
免费 | 1590篇 |
国内免费 | 35篇 |
专业分类
电工技术 | 336篇 |
综合类 | 56篇 |
化学工业 | 6968篇 |
金属工艺 | 597篇 |
机械仪表 | 576篇 |
建筑科学 | 1883篇 |
矿业工程 | 77篇 |
能源动力 | 873篇 |
轻工业 | 2686篇 |
水利工程 | 295篇 |
石油天然气 | 166篇 |
武器工业 | 3篇 |
无线电 | 2286篇 |
一般工业技术 | 5915篇 |
冶金工业 | 5204篇 |
原子能技术 | 205篇 |
自动化技术 | 5355篇 |
出版年
2023年 | 277篇 |
2022年 | 447篇 |
2021年 | 696篇 |
2020年 | 504篇 |
2019年 | 591篇 |
2018年 | 721篇 |
2017年 | 690篇 |
2016年 | 907篇 |
2015年 | 813篇 |
2014年 | 1027篇 |
2013年 | 1919篇 |
2012年 | 1669篇 |
2011年 | 2122篇 |
2010年 | 1509篇 |
2009年 | 1463篇 |
2008年 | 1762篇 |
2007年 | 1646篇 |
2006年 | 1441篇 |
2005年 | 1228篇 |
2004年 | 1093篇 |
2003年 | 945篇 |
2002年 | 912篇 |
2001年 | 542篇 |
2000年 | 523篇 |
1999年 | 532篇 |
1998年 | 488篇 |
1997年 | 447篇 |
1996年 | 459篇 |
1995年 | 438篇 |
1994年 | 425篇 |
1993年 | 428篇 |
1992年 | 384篇 |
1991年 | 229篇 |
1990年 | 319篇 |
1989年 | 321篇 |
1988年 | 272篇 |
1987年 | 296篇 |
1986年 | 286篇 |
1985年 | 306篇 |
1984年 | 267篇 |
1983年 | 256篇 |
1982年 | 239篇 |
1981年 | 209篇 |
1980年 | 175篇 |
1979年 | 182篇 |
1978年 | 166篇 |
1977年 | 135篇 |
1976年 | 123篇 |
1975年 | 134篇 |
1974年 | 109篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Two experiments involving 99 undergraduate participants sought to examine the influence of mood states on encoding speed within lexical decision and pronunciation tasks. Mood states were measured naturalistically in Experiment 1 and manipulated in Experiment 2. Stimuli consisted of nouns representing useful (e.g., food) and nonuseful (e.g., lint) objects. Mood states had no implications for initial encoding speed. However, when the same words were presented a 2nd time (i.e., repeated), happy individuals displayed a tendency to encode useful words faster than nonuseful ones. Thus, mood states influenced repetition priming on the basis of stimulus valence. The authors propose that happiness sensitizes individuals to useful or rewarding objects, which in turn creates a stronger memory trace for such stimuli in the future. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
102.
Michael Fox Richard Hastings Scott Lovald Juan Heinrich 《Journal of Failure Analysis and Prevention》2007,7(3):165-174
A failure analysis case study is presented for a two-piece aerosol containing tetrafluoroethane, commonly referred to as Refrigerant
134a. A gentleman was preparing to recharge the air conditioning system of an automobile when the bottom exploded off the
aerosol container, propelling the body of the aerosol container like a rocket, which hit the man in the eye and blinded him
in that eye. The aerosol was never connected to the air conditioner, therefore backpressure from the air conditioner (AC)
compressor was ruled out as a cause for the explosion. The objective of the study was to determine why the aerosol exploded.
Several recently developed test methods were used, including two types of heat-to-burst tests and a puncture chamber to measure
the pressure-versus-temperature behavior of aerosols. More common test methods were also used, such as water bath pressure
tests, hydro pressure burst tests, pneumatic pressure burst tests, hardness measurements, weight measurements, metallography,
scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and an accident scenario recreation. A semi-empirical
correlation between the hardness and weights of the container bottoms was used to determine the explosion temperature and/or
pressure. This semi-empirical correlation agrees in principle with an analysis of the explosion pressures using finite-element
analysis (FEA). The root cause for the explosion was determined to be a lack of strength of the bottom of the two-piece aerosol
coupled with heating the aerosol to temperatures significantly above room temperature. 相似文献
103.
104.
Karin Bucher Jens Mende Michael Mehring Martin Jansen 《Fullerenes, Nanotubes and Carbon Nanostructures》2007,15(1):29-42
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
105.
106.
Kreppner Jana M.; Rutter Michael; Beckett Celia; Castle Jenny; Colvert Emma; Groothues Christine; Hawkins Amanda; O'Connor Thomas G.; Stevens Suzanne; Sonuga-Barke Edmund J. S. 《Canadian Metallurgical Quarterly》2007,43(4):931
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
107.
O'Driscoll Michael P.; Poelmans Steven; Spector Paul E.; Kalliath Thomas; Allen Tammy D.; Cooper Cary L.; Sanchez Juan I. 《Canadian Metallurgical Quarterly》2003,10(4):326
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
108.
109.
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