全文获取类型
收费全文 | 50282篇 |
免费 | 5566篇 |
国内免费 | 3734篇 |
专业分类
电工技术 | 1682篇 |
综合类 | 5376篇 |
化学工业 | 6562篇 |
金属工艺 | 5786篇 |
机械仪表 | 3834篇 |
建筑科学 | 8209篇 |
矿业工程 | 3180篇 |
能源动力 | 1285篇 |
轻工业 | 2751篇 |
水利工程 | 2357篇 |
石油天然气 | 3227篇 |
武器工业 | 450篇 |
无线电 | 1867篇 |
一般工业技术 | 7505篇 |
冶金工业 | 3144篇 |
原子能技术 | 446篇 |
自动化技术 | 1921篇 |
出版年
2024年 | 253篇 |
2023年 | 798篇 |
2022年 | 2303篇 |
2021年 | 2329篇 |
2020年 | 1813篇 |
2019年 | 1599篇 |
2018年 | 1499篇 |
2017年 | 1885篇 |
2016年 | 2057篇 |
2015年 | 2092篇 |
2014年 | 2921篇 |
2013年 | 3085篇 |
2012年 | 3455篇 |
2011年 | 3654篇 |
2010年 | 2732篇 |
2009年 | 2838篇 |
2008年 | 2612篇 |
2007年 | 3172篇 |
2006年 | 2793篇 |
2005年 | 2385篇 |
2004年 | 2030篇 |
2003年 | 1728篇 |
2002年 | 1521篇 |
2001年 | 1269篇 |
2000年 | 1151篇 |
1999年 | 949篇 |
1998年 | 772篇 |
1997年 | 703篇 |
1996年 | 594篇 |
1995年 | 492篇 |
1994年 | 414篇 |
1993年 | 308篇 |
1992年 | 299篇 |
1991年 | 205篇 |
1990年 | 186篇 |
1989年 | 171篇 |
1988年 | 109篇 |
1987年 | 81篇 |
1986年 | 49篇 |
1985年 | 42篇 |
1984年 | 46篇 |
1983年 | 22篇 |
1982年 | 33篇 |
1981年 | 12篇 |
1980年 | 25篇 |
1979年 | 26篇 |
1964年 | 10篇 |
1961年 | 6篇 |
1959年 | 10篇 |
1955年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
钢纤维聚合物混凝土抗压本构关系 总被引:2,自引:0,他引:2
钢纤维聚合物混凝土是由聚合物混凝土基体和钢纤维共同组成的纤维增强复合材料,它的力学行为不仅依赖于聚合物混凝土基体的行为,而且与钢纤维的掺量、分散特征以及钢纤维的几何尺寸有关,本文将基于损伤力学原理研究在不同纤维掺量下的钢纤维聚合物混凝土的全程压力-应变曲线及其本构模型。 相似文献
102.
Microhardness measurements have been performed on untreated (virgin) and electrically stressed, solvent‐cast laboratory‐prepared samples of pure poly(phenylene oxide) (PPO), pure polystyrene (PS), and PPO : PS polyblends with different weight proportions. Results of such measurement on untreated polyblend sample show that microhardness (Hv) increases with increase in the content of PS up to 10 wt %, which attributed to the existence of homogeneous phase morphology. However, this feature is not observable in samples containing higher content of PS. Electrical stress is found to modify considerably the mechanical property of polymer. The effect of electric field on the microhardness of such samples (PPO : PS :: 90 : 10) has been characterized by the existence of a peak. Trapping of charge carriers in electrically stressed samples imparts hardening to the polyblend up to an applied step field of 190 kV/cm. However, the excessive charging beyond this step field value destroys this characteristic. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
103.
Recent experiments have shown that metallic materials display significant size effects when the characteristic length scale of non-uniform plastic deformation is close to a micron. Couple stress plasticity has been developed to explain such phenomena by Fleck and Hutchinson. The mechanical behaviors of ultra-thin nickel beams in different boundary conditions were studied with the hybrid element developed for couple stress plasticity before. Strong scale effects are found when the beam's thickness is close to the material characteristic length scale. Such phenomena will disappear if the beam' s thickness is greatly larger than the material characteristic length scale. The scale effect is the beams inherent property and it does not change with the change of support conditions. 相似文献
104.
105.
Alpass Fiona; Flett Ross; Humphries Steve; Massey Claire; Morriss Stuart; Long Nigel 《Canadian Metallurgical Quarterly》2004,11(3):270
Previous studies have identified a number of different farm stressors and have reported gender and age differences in levels of stress. This study aimed to determine stress experienced by New Zealand dairy farmers, particularly in relation to adoption of new technology and its relationship to age and gender. Measures of farm stress and adoption of technology were completed by 985 dairy farmers. The highest levels of stress were reported for time pressures, machinery breakdown, weather, and government policies. Stress related to new technologies occurred rarely. Women reported more stress and higher levels of stress for understanding new technologies. There was also an increase in severity of stress with age related to new technologies. Overall, stress levels were moderate and may reflect favorable economic conditions. The findings suggest a need to tailor stress interventions to meet specific needs. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
106.
107.
108.
109.
200m3液氨球罐裂纹成因分析 总被引:1,自引:0,他引:1
通过检验,从球罐的应力状态、球罐的金属材料和腐蚀介质等方面对200m3液氨球罐表面裂纹的形貌及产生裂纹的原因进行了分析,确定了球罐的裂纹是应力腐蚀裂纹,并对球罐进行了强度计算及安全评估。 相似文献
110.
Schnurr Paula P.; Hayes Andrew F.; Lunney Carole A.; McFall Miles; Uddo Madeline 《Canadian Metallurgical Quarterly》2006,74(4):707
This study examined how change in posttraumatic stress disorder (PTSD) symptoms relates to change in quality of life. The sample consisted of 325 male Vietnam veterans with chronic PTSD who participated in a randomized trial of group psychotherapy. Latent growth modeling was used to test for synchronous effects of PTSD symptom change on psychosocial and physical health-related quality of life within the same time period and lagged effects of initial PTSD symptom change on later change in quality of life. PTSD symptoms were associated with reduced quality of life before treatment. There were synchronous effects of symptom change on change in quality of life but no significant lagged effects. Results indicate the importance of measuring quality of life in future investigations of PTSD treatment. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献