全文获取类型
收费全文 | 5634篇 |
免费 | 479篇 |
国内免费 | 187篇 |
专业分类
电工技术 | 228篇 |
技术理论 | 2篇 |
综合类 | 342篇 |
化学工业 | 1067篇 |
金属工艺 | 342篇 |
机械仪表 | 321篇 |
建筑科学 | 518篇 |
矿业工程 | 201篇 |
能源动力 | 133篇 |
轻工业 | 297篇 |
水利工程 | 92篇 |
石油天然气 | 407篇 |
武器工业 | 52篇 |
无线电 | 642篇 |
一般工业技术 | 686篇 |
冶金工业 | 274篇 |
原子能技术 | 33篇 |
自动化技术 | 663篇 |
出版年
2024年 | 28篇 |
2023年 | 107篇 |
2022年 | 169篇 |
2021年 | 252篇 |
2020年 | 205篇 |
2019年 | 170篇 |
2018年 | 182篇 |
2017年 | 213篇 |
2016年 | 182篇 |
2015年 | 234篇 |
2014年 | 283篇 |
2013年 | 382篇 |
2012年 | 386篇 |
2011年 | 404篇 |
2010年 | 338篇 |
2009年 | 299篇 |
2008年 | 293篇 |
2007年 | 267篇 |
2006年 | 314篇 |
2005年 | 241篇 |
2004年 | 171篇 |
2003年 | 138篇 |
2002年 | 128篇 |
2001年 | 101篇 |
2000年 | 98篇 |
1999年 | 135篇 |
1998年 | 124篇 |
1997年 | 109篇 |
1996年 | 79篇 |
1995年 | 63篇 |
1994年 | 49篇 |
1993年 | 38篇 |
1992年 | 28篇 |
1991年 | 20篇 |
1990年 | 15篇 |
1989年 | 14篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 2篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1971年 | 2篇 |
排序方式: 共有6300条查询结果,搜索用时 0 毫秒
61.
在工业中采用钛合金的微弧氧化 总被引:21,自引:0,他引:21
采用硬度测试,金相显微观察和透射电镜分析等方法,研究了微量稀土Er对高纯铝再结晶行为的影响,结果表明,弥散分布的细小Al3Er质点对位错和亚晶界具有钉扎作用,可以有效抑制再结晶,将高纯铝的再结晶温度提高50左右,同时还能显著细化再结晶晶粒,再结晶形核机制是亚晶聚合和亚昌长大双重机制。 相似文献
62.
63.
64.
敞开式阳极焙烧炉的烟气(一) 总被引:1,自引:2,他引:1
敞开式焙烧炉的烟气,在阳极焙烧的设计和生产中。是必须引起重视的要素。烟气量。污染物种类及含量,烟气的温度压力等参数,对确定焙烧炉的有关尺寸。净化方案的选择。以及净化装置的大小等都是至关重要的。 相似文献
65.
M. O. Pekguleryuz H. Kaplan R. Neelameggham J. Hryn E. Nyberg B. Powell G. Cole J. F. Nie 《JOM Journal of the Minerals, Metals and Materials Society》2002,54(8):18-21
Conclusion It is expected that the research in high-temperature alloy development will reach a critical mass in about five years. This
will not only raise the materials science of magnesium to a higher level but will also increase the confidence of the industry
in magnesium as a structural performance material. Currently, applications are being actively pursued in United States Council
for Automotive Research power train programs and European Council for Automotive R&D engine block programs to develop the
technology for elevated-temperature magnesium. More research is still needed in this interesting materials field. 相似文献
66.
H. -Y. Nie M. J. Walzak N. S. McIntyre 《Journal of Materials Engineering and Performance》2004,13(4):451-460
Atomic force microscopy (AFM) uses a very sharp pointed mechanical probe to collect real-space morphological information of
solid surfaces. AFM was used in this study to image the surface morphology of a biaxially oriented polypropylene film. The
polymer film is characterized by a nanometer-scale, fiberlike network structure, which reflects the drawing process used during
the fabrication of the film. AFM was used to study polymer-surface treatment to improve wettability by exposing the polymer
to ozone with or without ultraviolet (UV) irradiation. Surface-morphology changes observed by AFM are the result of the surface
oxidation induced by the treatment. Due to the topographic features of the polymer film, the fiberlike structure has been
used to check the performance of the AFM tip. An AFM image is a mixture of the surface morphology and the shape of the AFM
tip. Therefore, it is important to check the performance of a tip to ensure that the AFM image collected reflects the true
surface features of the sample, rather than contamination on the AFM tip. 相似文献
67.
68.
Bingbing Nie Taewung Kim Yan Wang Varun Bollapragada Tom Daniel Jeff R. Crandall 《Multibody System Dynamics》2016,38(3):297-316
Dimensional scaling approaches are widely used to develop multi-body human models in injury biomechanics research. Given the limited experimental data for any particular anthropometry, a validated model can be scaled to different sizes to reflect the biological variance of population and used to characterize the human response. This paper compares two scaling approaches at the whole-body level: one is the conventional mass-based scaling approach which assumes geometric similarity; the other is the structure-based approach which assumes additional structural similarity by using idealized mechanical models to account for the specific anatomy and expected loading conditions. Given the use of exterior body dimensions and a uniform Young’s modulus, the two approaches showed close values of the scaling factors for most body regions, with 1.5 % difference on force scaling factors and 13.5 % difference on moment scaling factors, on average. One exception was on the thoracic modeling, with 19.3 % difference on the scaling factor of the deflection. Two 6-year-old child models were generated from a baseline adult model as application example and were evaluated using recent biomechanical data from cadaveric pediatric experiments. The scaled models predicted similar impact responses of the thorax and lower extremity, which were within the experimental corridors; and suggested further consideration of age-specific structural change of the pelvis. Towards improved scaling methods to develop biofidelic human models, this comparative analysis suggests further investigation on interior anatomical geometry and detailed biological material properties associated with the demographic range of the population. 相似文献
69.
Nowadays, the road network has gained more and more attention in the research area of databases. Existing works mainly focus on standalone queries, such as k-nearest neighbor queries over a single type of objects (e.g., facility like restaurant or hotel). In this paper, we propose a k-multi-preference (kMP) query over road networks, involving complex query predicates and multiple facilities. In particular, given a query graph, a kMP query retrieves of the top-k groups of vertices (of k facility types) satisfying the label constraints and their aggregate distances are the smallest. A naïve solution to this problem is to enumerate all combinations of vertices with k possible facility types and then select the one with the minimum sum distance. This method, however, incurs rather high computation cost due to exponential possible combinations. In addition, the existing solutions to other standalone queries are for a single type of facilities and cannot be directly used to answer kMP queries. Therefore, in this paper, we propose an efficient approach to process a kMP query, which utilizes an index with bounded space and reduces the computation cost of the shortest path queries. We also design effective pruning techniques to filter out false alarms. Through our extensive experiments, we demonstrate the efficiency and effectiveness of our proposed solutions. 相似文献
70.