全文获取类型
收费全文 | 32607篇 |
免费 | 2533篇 |
国内免费 | 1445篇 |
学科分类
工业技术 | 36585篇 |
出版年
2024年 | 93篇 |
2023年 | 346篇 |
2022年 | 575篇 |
2021年 | 813篇 |
2020年 | 838篇 |
2019年 | 691篇 |
2018年 | 727篇 |
2017年 | 964篇 |
2016年 | 1115篇 |
2015年 | 1357篇 |
2014年 | 1990篇 |
2013年 | 2079篇 |
2012年 | 2249篇 |
2011年 | 2485篇 |
2010年 | 2009篇 |
2009年 | 1890篇 |
2008年 | 1892篇 |
2007年 | 2102篇 |
2006年 | 1919篇 |
2005年 | 1659篇 |
2004年 | 1358篇 |
2003年 | 1199篇 |
2002年 | 1040篇 |
2001年 | 937篇 |
2000年 | 765篇 |
1999年 | 650篇 |
1998年 | 538篇 |
1997年 | 394篇 |
1996年 | 378篇 |
1995年 | 304篇 |
1994年 | 255篇 |
1993年 | 172篇 |
1992年 | 156篇 |
1991年 | 124篇 |
1990年 | 114篇 |
1989年 | 64篇 |
1988年 | 53篇 |
1987年 | 26篇 |
1986年 | 18篇 |
1985年 | 35篇 |
1984年 | 27篇 |
1983年 | 35篇 |
1982年 | 33篇 |
1981年 | 7篇 |
1980年 | 8篇 |
1979年 | 7篇 |
1978年 | 10篇 |
1965年 | 18篇 |
1962年 | 7篇 |
1959年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Toshihiko Hoshide Junpei Fujita 《Journal of Materials Engineering and Performance》2008,17(5):627-632
Strength of ground ceramics may be affected by residual stress as well as surface flaws induced by grinding. Strength prediction
for ground ceramics is convenient for mechanical design of ceramic components. In this article, a numerical procedure based
on fracture mechanics was proposed to estimate strength distribution of ground ceramics by considering grinding-induced residual
stress. Bending strength and residual stress of ground ceramics were measured for three grinding-conditions. By comparison
of simulated results with experimental ones, it was revealed that strength characteristics in experiments were well simulated
by using the proposed procedure. 相似文献
72.
Wang Xuegang Yan Fengjie Yan Qian Li Xingeng 《Frontiers of Materials Science in China》2007,1(2):225-227
An iron-based amorphous foil (FeNiCrSiB) was used as an interlayer for the amorphous diffusion bonding of low carbon steel
pipes under argon flux. The microstructure and mechanical properties of the joint were analyzed using an electron probe micro-analyzer
(EPMA), tensile test, bending test and impact test. The results show that the joint microstructure resembles that of the base
metal and no precipitates form at the joint. Melting point depressants (B, Si) diffuse far away from the joint and the base
metal element is homogenous across the joint. The joint impact toughness is greater than the base metal toughness and the
mechanical properties of the joint are similar around the pipe. 相似文献
73.
In this paper, the test results of liquid injection impact on the performance of new alternative refrigerant mixtures such as: R-410A, R-507, R-407C and R-404A are discussed, analysed and presented. The test results were obtained using an air-source heat pump set-up with enhanced surface tubing under various liquid injection ratios. Performance tests were conducted according to the ARI/ASHRAE standards. The performance data demonstrated that as liquid injection ratio increases, compressor head pressure and discharge temperature decrease. This has a positive effect in protecting the compressor. The effect of liquid injection on mixture behaviour varies from one mixture to another depending upon the mixture's composition. Furthermore, liquid injection appears to have a significant influence on R-410A behaviour compared to the other mixtures in question. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
74.
超声波流量计计量系统性能的主要影响因素 总被引:3,自引:1,他引:2
随着我国天然气工业的发展,已有大量超声波流量计用于高压、大流量的天然气计量。尽管我国已于2001年颁布并实施了气体超声波流量计使用方面的国家标准GB/T18604-2001,但是随着超声波流量计越来越广泛的使用,国内外对超声波流量计计量性能的影响因素已有了进一步的研究;而且,目前我国超声波流量计在天然气计量中的应用效果也还需要进一步改善。因此,根据目前国、内外最新研究成果,对噪声、脏污、压力及温度测量对超声波流量计计量系统性能的主要影响因素以及控制对策进行了分析探讨,以期改变虽经实验室检定合格、但用于现场却不能达到预期计量性能效果的情况,使超声波流量计在现场能够得到更好的应用。 相似文献
75.
76.
77.
介绍了安装在液压试验机上的一种集冲裁、切口作用于一体的复合冲裁模的设计,解决了没有压力机的情况下冲裁件的加工问题。 相似文献
78.
Reinforced concrete slabs are among the most common structural elements. In spite of the large number of slabs designed and built, the effect of their details on their behavior under impact loads are not always appreciated or properly taken into account. This experimental study was aimed at understanding the dynamic behavior of structural concrete slabs under impact loading to improve the state of the art of protective design. This study investigated the effects of different types of slab reinforcements and the applied impact loads on the dynamic response and behavior of reinforced concrete slabs. 相似文献
79.
80.