全文获取类型
| 收费全文 | 8182篇 |
| 免费 | 130篇 |
| 国内免费 | 175篇 |
专业分类
| 电工技术 | 119篇 |
| 综合类 | 322篇 |
| 化学工业 | 663篇 |
| 金属工艺 | 833篇 |
| 机械仪表 | 1195篇 |
| 建筑科学 | 395篇 |
| 矿业工程 | 227篇 |
| 能源动力 | 263篇 |
| 轻工业 | 166篇 |
| 水利工程 | 61篇 |
| 石油天然气 | 313篇 |
| 武器工业 | 46篇 |
| 无线电 | 287篇 |
| 一般工业技术 | 1987篇 |
| 冶金工业 | 592篇 |
| 原子能技术 | 88篇 |
| 自动化技术 | 930篇 |
出版年
| 2025年 | 22篇 |
| 2024年 | 25篇 |
| 2023年 | 55篇 |
| 2022年 | 80篇 |
| 2021年 | 107篇 |
| 2020年 | 145篇 |
| 2019年 | 109篇 |
| 2018年 | 124篇 |
| 2017年 | 158篇 |
| 2016年 | 194篇 |
| 2015年 | 280篇 |
| 2014年 | 363篇 |
| 2013年 | 560篇 |
| 2012年 | 473篇 |
| 2011年 | 598篇 |
| 2010年 | 479篇 |
| 2009年 | 459篇 |
| 2008年 | 459篇 |
| 2007年 | 468篇 |
| 2006年 | 457篇 |
| 2005年 | 386篇 |
| 2004年 | 363篇 |
| 2003年 | 379篇 |
| 2002年 | 297篇 |
| 2001年 | 193篇 |
| 2000年 | 166篇 |
| 1999年 | 185篇 |
| 1998年 | 197篇 |
| 1997年 | 156篇 |
| 1996年 | 107篇 |
| 1995年 | 94篇 |
| 1994年 | 68篇 |
| 1993年 | 37篇 |
| 1992年 | 38篇 |
| 1991年 | 25篇 |
| 1990年 | 24篇 |
| 1989年 | 21篇 |
| 1988年 | 27篇 |
| 1987年 | 9篇 |
| 1986年 | 9篇 |
| 1984年 | 5篇 |
| 1967年 | 6篇 |
| 1966年 | 6篇 |
| 1965年 | 9篇 |
| 1964年 | 12篇 |
| 1962年 | 7篇 |
| 1958年 | 4篇 |
| 1957年 | 4篇 |
| 1956年 | 6篇 |
| 1955年 | 5篇 |
排序方式： 共有8487条查询结果，搜索用时 15 毫秒
81.
Fuller R 《Accident; analysis and prevention》2005,37(3):461-472
Taylor [Taylor, D.H., 1964. Drivers' galvanic skin response and the risk of accident. Ergonomics 7, 439-451] argued that drivers attempt to maintain a constant level of anxiety when driving which Wilde [Wilde, G.J.S., 1982. The theory of risk homeostasis: implications for safety and health. Risk Anal. 2, 209-225] interpreted to be coupled to subjective estimates of the probability of collision. This theoretical paper argues that what drivers attempt to maintain is a level of task difficulty. Naatanen and Summala [Naatanen, R., Summala, H., 1976. Road User Behaviour and Traffic Accidents. North Holland/Elsevier, Amsterdam, New York] similarly rejected the concept of statistical risk as a determinant of driver behaviour, but in so doing fell back on the learning process to generate a largely automatised selection of appropriate safety margins. However it is argued here that driver behaviour cannot be acquired and executed principally in such S-R terms. The concept of task difficulty is elaborated within the framework of the task-capability interface (TCI) model, which describes the dynamic interaction between the determinants of task demand and driver capability. It is this interaction which produces different levels of task difficulty. Implications of the model are discussed regarding variation in performance, resource allocation, hierarchical decision-making and the interdependence of demand and capability. Task difficulty homeostasis is proposed as a key sub-goal in driving and speed choice is argued to be the primary solution to the problem of keeping task difficulty within selected boundaries. The relationship between task difficulty and mental workload and calibration is clarified. Evidence is cited in support of the TCI model, which clearly distinguishes task difficulty from estimates of statistical risk. However, contrary to expectation, ratings of perceived risk depart from ratings of statistical risk but track difficulty ratings almost perfectly. It now appears that feelings of risk may inform driver decision making, as Taylor originally suggested, but not in terms of risk of collision, but rather in terms of task difficulty. Finally risk homeostasis is presented as a special case of task difficulty homeostasis. 相似文献
82.
83.
N. Winzer A. Atrens W. Dietzel G. Song K. U. Kainer 《Advanced Engineering Materials》2008,10(5):453-458
84.
本文通过慢应变速度应力腐蚀试验,研究制冷压力容器用材16MnR、Q235-C、20R三种材料焊接接头在液氨中的应力腐蚀行为,评定其在液氨中发生应力腐蚀开裂的敏感性。 相似文献
85.
王荣 《理化检验(物理分册)》2006,42(11):580-582
在检修雏护换热器汽包时发现汽包封头泄漏,在汽包封头的阀盖角焊缝处出现裂纹,裂纹平行于焊缝。采用宏观形貌分析、化学成分分析、金相检验、显微硬度测定、能谱分析以及应力分析等方法对泄漏处进行了分析。结果表明,汽包中水质含有较高浓度的碱性元素和氧、硫、氧等强腐蚀性元素,又在焊接残余应力的作用下发生应力腐蚀开裂,最后导致汽包封头产生泄漏。 相似文献
86.
About 29600 Norwegian accident-involved drivers received a questionnaire about the last accident reported to their insurance company. About 9200 drivers (31%) returned the questionnaire. The questionnaire contained questions about sleep or fatigue as contributing factors to the accident. In addition, the drivers reported whether or not they had fallen asleep some time whilst driving. and what the consequences had been. Sleep or drowsiness was a contributing factor in 3.9% of all accidents, as reported by drivers who were at fault for the accident. This factor was strongly over-represented in night-time accidents (18.6%), in running-off-the-road accidents (8.3%), accidents after driving more than 150 km on one trip (8.1%), and personal injury accidents (7.3%). A logistic regression analysis showed that the following additional factors made significant and independent contributions to increasing the odds of sleep involvement in an accident: dry road, high speed limit, driving one's own car, not driving the car daily, high education, and few years of driving experience. More male than female drivers were involved in sleep-related accidents, but this seems largely to be explained by males driving relatively more than females on roads with high speed limits. A total of 10% of male drivers and 4% of females reported to have fallen asleep while driving during the last 12 months. A total of 4% of these events resulted in an accident. The most frequent consequence of falling asleep--amounting to more than 40% of the reported incidents--was crossing of the right edge-line before awaking, whereas crossing of the centreline was reported by 16%. Drivers' lack of awareness of important precursors of falling asleep--like highway hypnosis, driving without awareness, and similar phenomena--as well as a reluctance to discontinue driving despite feeling tired are pointed out as likely contributors to sleep-related accidents. More knowledge about the drivers' experiences immediately preceding such accidents may give a better background for implementing effective driver warning systems and other countermeasures. 相似文献
87.
The deformation and distribution of stress triaxiality σ_m/σ of mixed I + II mode elastic-plastic cracks under plane strain and plane stress conditions were analysed by the large strain finite element method and were compared with the HRR field. The results show that, (1) the model of crack-tip deformation under mixed I + II mode loading is sharpening-blunting, the sharpening and blunting deformation is acted on by compressive stress (σ_m/σ > 0) and tensile stress (σ_m/σ > 0), respectively; (2) in the plane strain case, the (σ_m/σ)_max of the real crack tip decreases with an increase of mode II component, but increases with an increasing strain hardening n for every mixed ratio. For the loading of K_I/K_II > 0.5, the (σ_m/σ)_max value of the real crack tip is less than that of the (σ_m/σ)_max given by the HRR field, but the opposite holds true cases where K_I/K_II > 0.5; (3) in the plane stress case, the (σ_m/σ)_max decreases a few values with an increasing mode II component, the values of (σ_m/σ)_max of every mixed ratio are far less than these of the corresponding loading condition in the plane strain case. In the plane stress case, the (σ_m/σ)_max values of every mixed ratio for any strain hardening exponent n are almost constant. This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
88.
Piper Megan E.; Piasecki Thomas M.; Federman E. Belle; Bolt Daniel M.; Smith Stevens S.; Fiore Michael C.; Baker Timothy B. 《Canadian Metallurgical Quarterly》2004,72(2):139
The dependence construct fills an important explanatory role in motivational accounts of smoking and relapse. Frequently used measures of dependence are either atheoretical or grounded in a unidimensional model of physical dependence. This research creates a multidimensional measure of dependence that is based on theoretically grounded motives for drug use and is intended to reflect mechanisms underlying dependence. Data collected from a large sample of smokers (N = 775) indicated that all 13 subscales of the Wisconsin Inventory of Smoking Dependence Motives (WISDM-68) have acceptable internal consistency, are differentially present across levels of smoking heaviness, and have a multidimensional structure. Validity analyses indicated the WISDM-68 subscales are significantly related to dependence criteria such as smoking heaviness and to 4th edition Diagnostic and Statistical Manual of Mental Disorders symptoms of dependence and relapse. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
89.
Subcritical crack growth is one of the main causes of time-dependent behavior in rocks. Double torsion (DT) tests have often been used to study subcritical crack growth in rocks. There are three methods used for the DT test, each with different loading conditions: the constant load (CL) method, the constant displacement (CDR) method, and the load relaxation (RLX) method. The RLX method is convenient, because the wide range of data of subcritical crack growth can be obtained with a single experimental run. In this study, subcritical crack growth in andesite was investigated using RLX method of the DT test.To determine the appropriate shape for the guide groove in DT specimens, tests were performed using rectangular, semi-circular, and triangular section grooves. The level of reproducibility of the test results was highest for specimens with a rectangular groove. Hence, this is an appropriate guide groove shape for DT specimens.DT tests were also performed for different water vapor pressures to investigate the effects on subcritical crack growth. The results showed that crack growth was facilitated at higher water vapor pressures. Additionally, the activation energy for subcritical crack growth in andesite was determined from the experimental results, and the crack velocity values for various temperature, humidity, and stress conditions were calculated theoretically. The crack velocity can be predicted from theory for various environmental and stress conditions. 相似文献
90.
高层建筑现浇超长地下室应力发展分析 总被引：4，自引：0，他引：4
本文以实际工程为背景 ,采用有限元的方法 ,对工程界关心的超长地下室一次性连续浇筑后早期裂缝问题进行数值分析。着重对比应力释放带开设前后 ,地下室墙板、顶板各处应力发展情况 ,并对现浇墙板结构早期的应力发展情况进行分析。 相似文献