全文获取类型
收费全文 | 54041篇 |
免费 | 6273篇 |
国内免费 | 3697篇 |
专业分类
电工技术 | 5323篇 |
技术理论 | 1篇 |
综合类 | 5483篇 |
化学工业 | 4891篇 |
金属工艺 | 2247篇 |
机械仪表 | 3751篇 |
建筑科学 | 4240篇 |
矿业工程 | 1241篇 |
能源动力 | 1674篇 |
轻工业 | 3654篇 |
水利工程 | 1046篇 |
石油天然气 | 2100篇 |
武器工业 | 875篇 |
无线电 | 5917篇 |
一般工业技术 | 5776篇 |
冶金工业 | 3012篇 |
原子能技术 | 836篇 |
自动化技术 | 11944篇 |
出版年
2024年 | 297篇 |
2023年 | 766篇 |
2022年 | 1381篇 |
2021年 | 1584篇 |
2020年 | 1939篇 |
2019年 | 1744篇 |
2018年 | 1611篇 |
2017年 | 2028篇 |
2016年 | 2280篇 |
2015年 | 2366篇 |
2014年 | 3322篇 |
2013年 | 3750篇 |
2012年 | 3618篇 |
2011年 | 4011篇 |
2010年 | 2975篇 |
2009年 | 3142篇 |
2008年 | 2955篇 |
2007年 | 3470篇 |
2006年 | 3265篇 |
2005年 | 2732篇 |
2004年 | 2279篇 |
2003年 | 2095篇 |
2002年 | 1829篇 |
2001年 | 1597篇 |
2000年 | 1324篇 |
1999年 | 1035篇 |
1998年 | 804篇 |
1997年 | 718篇 |
1996年 | 574篇 |
1995年 | 464篇 |
1994年 | 381篇 |
1993年 | 307篇 |
1992年 | 206篇 |
1991年 | 190篇 |
1990年 | 150篇 |
1989年 | 119篇 |
1988年 | 89篇 |
1987年 | 87篇 |
1986年 | 63篇 |
1985年 | 67篇 |
1984年 | 51篇 |
1983年 | 43篇 |
1982年 | 41篇 |
1981年 | 34篇 |
1980年 | 32篇 |
1979年 | 26篇 |
1977年 | 13篇 |
1964年 | 17篇 |
1959年 | 12篇 |
1956年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Wilcox Sara; Evenson Kelly R.; Aragaki Aaron; Wassertheil-Smoller Sylvia; Mouton Charles P.; Loevinger Barbara Lee 《Canadian Metallurgical Quarterly》2003,22(5):513
This study examined whether widowhood was associated with physical and mental health, health behaviors, and health outcomes using a cross-sectional (N=72,247) and prospective (N=55,724) design in women aged 50-79 years participating in the Women's Health Initiative observational study (85.4% White). At baseline, married women reported better physical and mental health and generally better health behaviors than widowed women. Whereas women who remained married over the 3-year period showed stability in mental health, recent widows experienced marked impairments and longer term widows showed stability or slight improvements. Both groups of widows reported more unintentional weight loss over the 3-year period. Changes in physical health and health behaviors were inconsistent, with generally small effect sizes. Findings underscore the resilience of older women and their capacity to reestablish connections, but point to the need for services that strengthen social support among women who have difficulty during this transition. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
32.
33.
L. T. MO M. HUURMAN S. P. WU A. A. A. MOLENAAR 《Fatigue & Fracture of Engineering Materials & Structures》2007,30(9):823-831
Tensile fatigue behaviours of bitumen–stone adhesion were investigated using a dynamic mechanics analyser under stress‐controlled mode at two temperatures of 5 and 25°C and various controlled‐stress levels. Failure characteristics including interfacial failure and cohesive failure were examined using image analysis of fracture surfaces. Finite‐element analysis on stress distributions was conducted under different temperatures, film thickness and interfacial bonding conditions. A Coulomb–Mohr like criterion in combination with shear and normal stresses is proposed to deal with the extreme thin adhesive layer, which can be further simplified into an adhesive zone without significant loss of accuracy for stress analysis. 相似文献
34.
Nusslock Robin; Abramson Lyn Y.; Harmon-Jones Eddie; Alloy Lauren B.; Hogan Michael E. 《Canadian Metallurgical Quarterly》2007,116(1):105
On the basis of the behavioral approach system (BAS) dysregulation theory of bipolar disorder, this study examined the relation between occurrence of a BAS activation-relevant life event--goal striving--and onset of hypomanic and depressive episodes and symptoms. In particular, the authors examined the relation between preparing for and completing final exams (a goal-striving event) and onset of bipolar spectrum episodes and symptoms in college students with bipolar II disorder or cyclothymia (i.e., "soft" bipolar spectrum conditions). One hundred fifty-nine individuals with either a bipolar spectrum disorder (n=68) or no major affective psychopathology (controls; n=91) were further classified on the basis of whether they were college students (i.e., completed final exams). Consistent with the BAS dysregulation theory, preparing for and completing final exams was associated with an increase in hypomanic but not depressive episodes and symptoms in individuals with a soft bipolar spectrum diagnosis. Furthermore, self-reported BAS sensitivity moderated the presence of certain hypomanic symptoms during final exams. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
35.
Comments on the original article "A New Big Five: Fundamental Principles for an Integrative Science of Personality," by Dan P. McAdams and Jennifer L. Pals (see record 2006-03947-002). McAdams and Pals (April 2006) presented a new model to integrate the field of personality psychology. Cultural and evolutionary factors interact with an individual's basic traits, characteristic adaptations, and life narratives, which in turn are linked to roles, demands, and behaviors. The current authors welcome McAdams and Pals's (2006) model for providing a way to integrate much of the previously disparate empirical findings in personality psychology. However, the current authors also think that McAdams and Pals (2006) overstated the inclusiveness of the model, and more generally, the current authors dispute their assertion that the grand theories of personality can be integrated within a single model. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
36.
RT-AGVS是物流管理中十分重要的课题,车辆位置监测网是其重要的组成部分。本文详细介绍了一个基于单片机系统的车辆位置实时监测网,本监测网设计先进,性能价格比高,它的设计方法和技术对其他许多领域有借鉴作用。 相似文献
37.
中针对变井储试井分析问题,给出了确定变井储系数及计算续流量的方法,并用反褶积分析积分析方法解释了未出现径向流的早期测压数据,给出了解决早期试井资料分析问题的有效方法。 相似文献
38.
During the day, there are considerable variations in the climatic factors prevailing in these regions. This is especially so during the 24-hour daily cycle of the long, hot and dry summer (mid-May to midOctober). Such climatic conditions have had a considerable impact on the daily living pattern of family life in the same season, particularly in the urban areas. During the same 24-hour cycle, they have compelled the inhabitants to shift their living activities both vertically in section and horizontally in plan; they do this in pursuit of more acceptable, if not, desirable internal thermal environmental ambience. 相似文献
39.
钻杆接头螺纹退刀尺寸是指外螺纹接头的台肩面到螺纹消失前第一个完整螺纹之间的距离。GB9253.1-88规定退刀尺寸应小于或等于12.7mm内螺纹,钻杆接头内螺纹的锤孔尺寸为16±2mm,以保证内、外螺纹啮合良好。经检测发现,从日本NKK公司进口的所有φ127mm钻杆接头外螺纹退刀尺寸都大于12.7mm,镗孔尺寸为16~18mm。而APISpec7K规定钻杆接头内螺纹最小镗孔尺寸为15.9mm。鉴于此,建议对我国的有关标准作相应修改,与API标准保持一致。 相似文献
40.