全文获取类型
收费全文 | 3528篇 |
免费 | 249篇 |
国内免费 | 183篇 |
专业分类
电工技术 | 129篇 |
综合类 | 196篇 |
化学工业 | 157篇 |
金属工艺 | 202篇 |
机械仪表 | 439篇 |
建筑科学 | 194篇 |
矿业工程 | 91篇 |
能源动力 | 46篇 |
轻工业 | 125篇 |
水利工程 | 131篇 |
石油天然气 | 117篇 |
武器工业 | 31篇 |
无线电 | 273篇 |
一般工业技术 | 451篇 |
冶金工业 | 289篇 |
原子能技术 | 157篇 |
自动化技术 | 932篇 |
出版年
2024年 | 5篇 |
2023年 | 25篇 |
2022年 | 43篇 |
2021年 | 80篇 |
2020年 | 82篇 |
2019年 | 45篇 |
2018年 | 65篇 |
2017年 | 70篇 |
2016年 | 87篇 |
2015年 | 120篇 |
2014年 | 215篇 |
2013年 | 186篇 |
2012年 | 277篇 |
2011年 | 309篇 |
2010年 | 235篇 |
2009年 | 216篇 |
2008年 | 199篇 |
2007年 | 222篇 |
2006年 | 217篇 |
2005年 | 198篇 |
2004年 | 170篇 |
2003年 | 166篇 |
2002年 | 122篇 |
2001年 | 76篇 |
2000年 | 83篇 |
1999年 | 93篇 |
1998年 | 73篇 |
1997年 | 47篇 |
1996年 | 45篇 |
1995年 | 31篇 |
1994年 | 32篇 |
1993年 | 16篇 |
1992年 | 17篇 |
1991年 | 16篇 |
1990年 | 16篇 |
1989年 | 10篇 |
1988年 | 12篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 7篇 |
1984年 | 4篇 |
1983年 | 7篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1975年 | 3篇 |
1971年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有3960条查询结果,搜索用时 15 毫秒
1.
Bin Feng Xin Jiang Guisheng Zou Wengan Wang Tianming Sun Heng Yang Guanlei Zhao Mingye Dong Yu Xiao Hongwei Zhu Lei Liu 《Advanced functional materials》2021,31(29):2102359
The realization of liquid metal-based wearable systems will be a milestone toward high-performance, integrated electronic skin. However, despite the revolutionary progress achieved in many other components of electronic skin, liquid metal-based flexible sensors still suffer from poor sensitivity due to the insufficient resistance change of liquid metal to deformation. Herein, a nacre-inspired architecture composed of a biphasic pattern (liquid metal with Cr/Cu underlayer) as “bricks” and strain-sensitive Ag film as “mortar” is developed, which breaks the long-standing sensitivity bottleneck of liquid metal-based electronic skin. With 2 orders of magnitude of sensitivity amplification while maintaining wide (>85%) working range, for the first time, liquid metal-based strain sensors rival the state-of-art counterparts. This liquid metal composite features spatially regulated cracking behavior. On the one hand, hard Cr cells locally modulate the strain distribution, which avoids premature cut-through cracks and prolongs the defect propagation in the adjacent Ag film. On the other hand, the separated liquid metal cells prevent unfavorable continuous liquid-metal paths and create crack-free regions during strain. Demonstrated in diverse scenarios, the proposed design concept may spark more applications of ultrasensitive liquid metal-based electronic skins, and reveals a pathway for sensor development via crack engineering. 相似文献
2.
《Measurement》2015
The evaluation of functional features of manufactured workpieces is based on GO- and NO-GO-test results, which are obtained by comparing measured geometric characteristics with nominal dimensions and tolerances specified by the designer. These geometrical specifications are based on a tolerancing system, which was originally defined for the function mating capability. Against the background of upcoming lots of other new functions (like reduction of flow resistance, light absorption, reduction of friction, diffraction of light, self-cleaning or mass transmission) are to be realized with our products – particularly by micro- and nano scaled features. If the verification process will deliver the prediction of the achievable degree of functionality, the usability of a part can be assessed more accurately and in consequence quality and economics can be improved. So, a new principle for tolerancing and verifying turns out to be necessary. In this paper the fundamental deficit of the actual tolerancing and specification systems GPS and ASME Y14.5 is derived and the path for enlarging the system by preposing a functional model is shown. To verify the functional capability of the workpieces an approach based on simulations done with the parameterized mathematical–physical model of the function is suggested. Advantages of this approach will be discussed and demonstrated by examples with microstructured inking rolls, crankshafts and injection valves. 相似文献
3.
Fatigue crack propagation of multiple coplanar cracks with the coupled extended finite element/fast marching method 总被引:1,自引:0,他引:1
A numerical technique for modeling fatigue crack propagation of multiple coplanar cracks is presented. The proposed method couples the extended finite element method (X-FEM) [Int. J. Numer. Meth. Engng. 48 (11) (2000) 1549] to the fast marching method (FMM) [Level Set Methods & Fast Marching Methods: Evolving Interfaces in Computational Geometry, Fluid Mechanics, Computer Vision, and Materials Science, Cambridge University Press, Cambridge, UK, 1999]. The entire crack geometry, including one or more cracks, is represented by a single signed distance (level set) function. Merging of distinct cracks is handled naturally by the FMM with no collision detection or mesh reconstruction required. The FMM in conjunction with the Paris crack growth law is used to advance the crack front. In the X-FEM, a discontinuous function and the two-dimensional asymptotic crack-tip displacement fields are added to the finite element approximation to account for the crack using the notion of partition of unity [Comput. Meth. Appl. Mech. Engng. 139 (1996) 289]. This enables the domain to be modeled by a single fixed finite element mesh with no explicit meshing of the crack surfaces. In an earlier study [Engng. Fract. Mech. 70 (1) (2003) 29], the methodology, algorithm, and implementation for three-dimensional crack propagation of single cracks was introduced. In this paper, simulations for multiple planar cracks are presented, with crack merging and fatigue growth carried out without any user-intervention or remeshing. 相似文献
4.
该工艺技术是在原三联作(TCP+MFE+JET)基础上,根据大港油田勘探试油(测试)的需要,研制开发出的又一新技术,与原三联作相比,一趟管柱不但完成求产、测压、泵排工作,而且还能进行酸化等措施,提高了资料品质,减少了作业成本。经过6井次现场应用,全部达到了设计要求,取得了工艺、资料、成本、速度的较大进步,具有较高推广应用价值。 相似文献
5.
将薄膜电容真空计的测量室接于被测密闭容器,静态真空室接于一个比较容器,即组成一台压差式漏率测试仪。首先使两容器压力平衡,真空计读数为零。当被测容器存在漏孔时,真空计薄膜两侧形成压差,真空计指示读数,继而计算出该容器的漏率。应用商品真空计在抽真空测试时,检测的最小可测漏率达10-4~10-5Pa·L/s;而在充压测试时,因受气体温度变化的影响,灵敏度会降低几个量级。该仪器有可能具备寻找漏孔位置和确定漏孔漏率的功能。 相似文献
6.
7.
介绍了质量流量计的工作原理有应用效果。这种新型质量流量计精度高,稳定性好,示值计量简便,可直接显示质量、流量、介质温度、密度等,维护量低,但必须正确安装、使用,才能发挥其应有的作用。 相似文献
8.
9.
The effects of the uncertainties associated ith the apparent strain and gauge factor data, given by the manufacturer, in the evaluation of principal strains are examined. Principal strains are obtained by a reduction of the strains measured ith electrical resistance strain gauge rectangular or delta rosettes. The theoretical analysis points out the relevance of the effects caused. 相似文献