全文获取类型
收费全文 | 6264篇 |
免费 | 466篇 |
国内免费 | 252篇 |
专业分类
电工技术 | 34篇 |
综合类 | 165篇 |
化学工业 | 2603篇 |
金属工艺 | 149篇 |
机械仪表 | 116篇 |
建筑科学 | 616篇 |
矿业工程 | 37篇 |
能源动力 | 12篇 |
轻工业 | 1395篇 |
水利工程 | 52篇 |
石油天然气 | 18篇 |
无线电 | 179篇 |
一般工业技术 | 621篇 |
冶金工业 | 415篇 |
原子能技术 | 76篇 |
自动化技术 | 494篇 |
出版年
2024年 | 37篇 |
2023年 | 240篇 |
2022年 | 1072篇 |
2021年 | 1046篇 |
2020年 | 299篇 |
2019年 | 268篇 |
2018年 | 180篇 |
2017年 | 213篇 |
2016年 | 206篇 |
2015年 | 221篇 |
2014年 | 339篇 |
2013年 | 315篇 |
2012年 | 264篇 |
2011年 | 291篇 |
2010年 | 275篇 |
2009年 | 274篇 |
2008年 | 239篇 |
2007年 | 245篇 |
2006年 | 169篇 |
2005年 | 140篇 |
2004年 | 126篇 |
2003年 | 103篇 |
2002年 | 96篇 |
2001年 | 45篇 |
2000年 | 52篇 |
1999年 | 24篇 |
1998年 | 37篇 |
1997年 | 28篇 |
1996年 | 17篇 |
1995年 | 19篇 |
1994年 | 16篇 |
1993年 | 15篇 |
1992年 | 7篇 |
1991年 | 7篇 |
1990年 | 7篇 |
1989年 | 7篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 9篇 |
1985年 | 7篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1977年 | 2篇 |
1968年 | 1篇 |
1962年 | 1篇 |
1961年 | 1篇 |
1960年 | 2篇 |
1959年 | 1篇 |
1958年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有6982条查询结果,搜索用时 0 毫秒
91.
92.
SUN Weibin WU Yafei DING Yi LIU Tianjia 《武汉理工大学学报(材料科学英文版)》2005,20(B12):156-158
The objective of this study is to investigate possible effects of nanometer powder of hydroxyapatite on proliferation of periodontal ligament cells. With sol-gel method, the nanometer hydroxyapatite powder were fabricated. The primary periodontal ligcament cells were caltured on dense particle hydroxyapatite and nanometer particle hydroxyapatite. The effects on proliferation of periodontal ligament cell were examined in vitro with MTT ( methyl thiazolil tetracolium) test. The intercellalar effects were observed with scanning electron microscopy and energy dispersive X-ray analyzer. In addition, the influence of two materials on osteogenetic differentiation was determined with measurement of ALP ( alkaline phosphatase ) activity. It is concluded that nanometer hydroxyapatite can promote proliferation and osteogenetic differeraiation of periodontal ligament cells and it may become absorbable agent in osseous restoration. 相似文献
93.
Stern Emily R.; Horvitz Jon C.; C?té Lucien J.; Mangels Jennifer A. 《Canadian Metallurgical Quarterly》2005,19(1):54
The authors explored the effect of Parkinson's disease (PD) on the generation and maintenance of response readiness in a simple reaction time task. They compared performance of idiopathic PD patients without dementia, age-matched controls, and younger controls over short (1-, 3-, and 6-s) and long (12- and 18-s) foreperiod intervals. After each trial, the authors probed memory for visual information that also had to be maintained during the trial interval. Patients and controls did not differ overall in their ability to maintain readiness over long delays. However, within the PD group only, errors in maintaining visual information were correlated with difficulty in maintaining readiness, suggesting that systems impaired in PD may facilitate the maintenance of processing in both motor and cognitive domains. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
94.
Ferris Patricia A.; Sinclair Christina; Kline Theresa J. 《Canadian Metallurgical Quarterly》2005,10(3):225
In a cross-sectional sample of 428 employees, the job demand-control-support and effort-reward imbalance job stress models were amalgamated and expanded to include modifiable risk factors and noncontrollable genetic factors related to cardiovascular disease (CVD) risk. With structural equation modeling, the constructs of lack of job resilience, lack of personal resilience, and job demand were used to examine how employer and employee factors related to psychosomatic strain and risk indicators of CVD. Negative perception of job demand predicted perception of lack of job resilience but not lack of personal resilience. Lack of job and personal resilience predicted strain. Women reported greater strain than men. CVD risk was predicted by strain, age, sex, and family history. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
95.
Vitaliano Peter P.; Echeverria Diana; Yi Joyce; Phillips Paul E. M.; Young Heather; Siegler Ilene C. 《Canadian Metallurgical Quarterly》2005,20(3):402
The authors examined relationships between chronic stress and cognitive decline and whether such relationships were mediated by psychophysiological factors. Ninety-six caregivers of spouses with Alzheimer's disease (AD) were compared with 95 similar noncaregiver spouses. All were free of diabetes. Although the groups started similarly, over 2 years caregivers declined by a small but significant amount (1 raw score point and 4 percentile points, each p 相似文献
96.
Tibon Shira; Weinberger Yifat; Handelzalts Jonathan E.; Porcelli Piero 《Canadian Metallurgical Quarterly》2005,22(4):508
The study applies Winnicott's conceptualization of potential space to the alexithymia construct by using a new Rorschach index, the Reality-Fantasy Scale (RFS). The scale uses variables derived from the Rorschach Comprehensive System (Exner, 2000, 2001) to detect different types of psychopathological manifestations conceptualized as forms of collapse of potential space. Following previous research, the present study further evaluates the construct validity of the RFS in a sample of 92 patients with inflammatory bowel disease, categorized on the basis of the Toronto Alexithymia Scale (TAS-20) as alexithymic, indeterminate alexithymia, and nonalexithymic groups. As hypothesized, the RFS significantly correlated with the TAS-20, discriminated among the 3 groups, and showed incremental validity in detecting alexithymia over isolated Rorschach markers. The study supports the exploration of psychoanalytic ideas by empirical, statistically based methods. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
97.
具有连续和脉冲预防接种的SIRS传染病模型 总被引:2,自引:0,他引:2
考虑了具有连续预防接种和脉冲预防接种且传染率是标准的SIRS传染病模型,在连续预防接种和脉冲预防接种下,分别给出了SIRS传染病模型基本再生数.在连续预防接种下,利用广义Dulac函数方法证明了无病平衡点和正平衡点的全局渐近稳定性.对脉冲预防接种下的SIRS传染病模型,首次证明了无病周期解的存在性和全局渐近稳定性. 相似文献
98.
99.
蒸发冷却水质问题的分析研究 总被引:2,自引:0,他引:2
蒸发冷却空调是以水作为制冷剂,通过在西北地区的实际工程应用,发现存在着蒸发冷却器表面结水垢以及细菌滋生等水质问题.本文针对这两大问题,从产生的原因、条件以及环境等方面进行了分析;阐述了导致上述两大问题的关键原因,提出从补水、流失水比例、水系统的软化以及抗菌剂的填加等几个环节加强水质管理的措施;通过全面的分析和研究,认为蒸发冷却器不会产生军团病. 相似文献
100.
刘毅博 《常州信息职业技术学院学报》2004,3(3):94-96
近年来,随着我国公路桥梁建设的快速发展,桥面铺装问题已引起重视。首先分析沥青混凝土桥面铺装的破坏形式,对钢筋混凝土桥柔性桥面铺装的早期病害,从结构、施工、防水层、铺装方面进行分析与研究,并指出了今后主要的研究方向。 相似文献