全文获取类型
收费全文 | 153885篇 |
免费 | 16614篇 |
国内免费 | 10488篇 |
专业分类
电工技术 | 13292篇 |
技术理论 | 3篇 |
综合类 | 14532篇 |
化学工业 | 19394篇 |
金属工艺 | 9502篇 |
机械仪表 | 9859篇 |
建筑科学 | 11275篇 |
矿业工程 | 5447篇 |
能源动力 | 4230篇 |
轻工业 | 15339篇 |
水利工程 | 4460篇 |
石油天然气 | 5656篇 |
武器工业 | 2248篇 |
无线电 | 15594篇 |
一般工业技术 | 13705篇 |
冶金工业 | 13173篇 |
原子能技术 | 2206篇 |
自动化技术 | 21072篇 |
出版年
2024年 | 980篇 |
2023年 | 2631篇 |
2022年 | 5679篇 |
2021年 | 7460篇 |
2020年 | 5464篇 |
2019年 | 3909篇 |
2018年 | 4141篇 |
2017年 | 4753篇 |
2016年 | 4379篇 |
2015年 | 6624篇 |
2014年 | 8151篇 |
2013年 | 9634篇 |
2012年 | 11868篇 |
2011年 | 12261篇 |
2010年 | 11485篇 |
2009年 | 10816篇 |
2008年 | 10965篇 |
2007年 | 10340篇 |
2006年 | 9212篇 |
2005年 | 7230篇 |
2004年 | 5291篇 |
2003年 | 3999篇 |
2002年 | 4032篇 |
2001年 | 3629篇 |
2000年 | 2825篇 |
1999年 | 1747篇 |
1998年 | 3363篇 |
1997年 | 2096篇 |
1996年 | 1440篇 |
1995年 | 933篇 |
1994年 | 756篇 |
1993年 | 735篇 |
1992年 | 282篇 |
1991年 | 240篇 |
1990年 | 203篇 |
1989年 | 193篇 |
1988年 | 149篇 |
1987年 | 124篇 |
1986年 | 97篇 |
1985年 | 76篇 |
1984年 | 22篇 |
1983年 | 25篇 |
1982年 | 54篇 |
1981年 | 51篇 |
1980年 | 85篇 |
1979年 | 23篇 |
1977年 | 158篇 |
1976年 | 284篇 |
1959年 | 39篇 |
1951年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
The objective of this study was to investigate the effects of mineralized bone nodules, formed in vitro by bone marrow stromal cells(BMSCs), on the new bone formation in bone defect and on implant surface. The mineralized bone nodules were generated by culture of Lewis rats BMSCs on titanium disks in osteogenic induction medium. The gap-healing animal model was used to create the bone defect facing the disk. The titanium disks in the presence of B group or in the absence of NB group bone nodules were randomly placed into one of the rat distal femurs. This self-control design was used to compare the bone formation in defects and on titanium surface, by Micro-CT, fluorescence staining, histological and histomorphometric analysis. The new bone formation parameters in bone defect area of B group were significantly higher than those of NB group at 2 weeks, including bone volume fraction, trabecular thickness and bone area ratio. The bone nodules pre-stained with Alizarin red disappeared mostly at 2 weeks, while the red fluorescence reappeared in the newly formed bone away from the disk surface. For the bone-implant contact, B group showed lower values than NB group at 2 weeks, but no significant difference was found at 4 weeks. Our results indicate that the mineralized bone nodules can be resorbed in vivo and promote the early osteogenesis in the bone defects, and bone nodules may be applicable for new bone generation in bone defect or modification of tissue engineering scaffold. 相似文献
82.
柴油机各个气缸的进气量、喷油量、燃烧等存在差异,导致气缸间存在做功差异,直接影响柴油机转速的平稳性以及排放性能等。针对位置式电控柴油机,采用PI闭环控制,通过瞬时转速信号识别并计算各缸的工作差异,利用分缸均衡控制算法对油量进行补偿修正。试验结果显示低转速稳态工况转速波动由7 r/min降至3 r/min,各缸工作不均匀度由±5 r/min降至±2 r/min,在瞬态过程和高转速3 400 r/min时该算法仍然适用有效。 相似文献
83.
马瑶 《吉林化工学院学报》2015,32(5):37-39
从女性主义的角度对简·奥斯丁的作品《傲慢与偏见》的两个中文译本——孙致礼和张玲、张扬的译本进行比较。分析女性主义意识对翻译过程以及最终译本的影响。 相似文献
84.
A robust lane detection and tracking system based on monocular vision is presented in this paper.First,the lane detection algorithm can transform raw images into top view images by inverse perspective mapping(IPM),and detect both inner sides of the lane accurately from the top view images.Then the system will turn to lane tracking procedures to extract the lane according to the information of last frame.If it fails to track the lane,lane detection will be triggered again until the true lane is found.In this system,θ-oriented Hough transform is applied to extract candidate lane markers,and a geometrical analysis of the lane candidates is proposed to remove the outliers.Additionally,vanishing point and region of interest(ROI)dynamically planning are used to enhance the accuracy and efficiency.The system was tested under various road conditions,and the result turned out to be robust and reliable. 相似文献
85.
MENG Fan-Jun XU Bin-Shi ZHU Sheng MA Shi-Ming ZHANG Wei ZHU Zi-Xin National Key Laboratory for Remanufacturing Beijng China 《材料热处理学报》2004,(5)
Fe-Al intermetallics with remarkable high-temperatureintensity and excellent erosion,high-temperatureoxidation and sulfuration resistance are potential lowcost high-temperature structural material.ProducingFe-Al/WC composite coating by high velocity arcspraying(HVAS)on structural materials would notonly obviate the problems faced in fabrication of thesealloys into useful shapes,but also allow the effectiveuse of their outstanding high-temperature performance,which might thus promisingly mak… 相似文献
86.
对于不锈钢的焊接,在NDT检测中仅对夹渣、未熔合、未焊透、气孔等缺陷均有评定标准,而对菜花状缺陷、树瘤状氧化缺陷、蓝脆现象、氧化现象等却没有评定方法及标准。为此,以不锈钢管的焊接试验为主鲒合不锈钢板的焊接,针对不锈钢在GTAW焊焊接中氧化缺陷的防止方法、氧化评定及检测标准提出几点看法,供行业界借鉴与批评指证。 相似文献
87.
The experimental researches on the chemical deposition of Ni-Mo-P amorphous alloys were carried out by adding Na2 MoO4 into acidic solutions. The optimum technology conditions were obtained by orthogonal design experiments. The structures and the relationship between compositions and their thermal stability were studied by energy spectrum (EC), scanning electron micrograph and X-ray diffraction spectrum. Compared with Ni-P amorphous alloys, the Ni-Mo-P amorphous alloys have high crystallization temperature and thermal stability, and the hardness reaches its peak when the annealing temperature is 500 ℃. With the increase of the heat treatment temperature, the surface morphology of the alloys changes. 相似文献
88.
在目前的生产条件下。通过大量的混联法物料衡算,定量地研究了供矿铝硅比、熟料铝硅比和拜年法赤泥铝硅比对混联法的制造成本、能耗和拜年法与烧结法的生产比例的影响规律,提出我国混联法生产进一步优化的方向和途径。并开发了研究和评价的计算软件。为混联法的生产和设计的进一步优化奠定基础。 相似文献
89.
90.