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191.
192.
Resistance soldering of optical components is an upcoming technology following the trends towards automation and miniaturization with particularly high relevance for high optical power applications. A stress analysis is necessary in order to qualify this technology with regard to the component's optical behavior and its long-term stability. Analytical and FEM-simulative calculations are used to estimate the stresses within the optical element and the solder layer for extensively soldered components. Furthermore partially soldered components are being simulated and optically evaluated using polarization microscopy. To evaluate the long-term stability of the compound multiple series of thermal cycling were performed. 相似文献
193.
表面安装技术自80年代以来已在电子工业中得到了广泛应用和发展,文中就SMT设备未来的发展趋势作了初步分析,从中可以看出SMT设备与电子技术相互促进、协调发展密不可分的关系。 相似文献
194.
对在不同条件下处理T10钢进行了磨损试验,氧化试验、腐蚀试验和B-Al共渗层的结合强度测试.结果表明,在比较之下B-Al共渗层的耐磨性,抗氧化性、耐蚀性和结合强度都比较高. 相似文献
195.
Interface features of ultrasonic flip chip bonding and reflow soldering in microelectronic packaging
Ultrasonic features in the bonding area are of interest for researchers in the field of microelectronic packaging. In this study, the interface characteristics of bonding were examined using an XD7100 X‐ray instrument and a transmission electron microscope (TEM). It was seen that bubbles were usually detected at the interfaces of the reflow‐soldered flip chip (FC), but they were not found at the interfaces of ultrasonically formed FC, and so ultrasonic FC bonding is more reliable than reflow soldering. The strong mechanical effect of ultrasonic vibration activates the dislocations in the crystalline metal lattice. Dislocation diffusion is more prominent than crystal diffusion when the temperature is relatively low during ultrasonic bonding, and therefore the processes of ultrasonic bonding enhance by several orders of magnitude. This indicates that the mechanism of ultrasonic bonding is different from the melting mechanism of reflow soldering. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
196.
The Delco process is a major flip chip under-bump metallurgy process and its contact is soldered with the Ni-7wt.%V substrate;
there are, however, only a few studies on the interfacial reactions between solders and Ni-V alloys. This study examines the
interfacial reactions of the Sn-0.7wt.%Cu alloy with the Ni-7wt.%V, Ni-5wt.%V, and Ni-3wt.%V substrates at 250°C. It is found
that the interfacial reactions between Sn-0.7wt.%Cu and Ni-V alloys are different from those between Sn-0.7wt.%Cu and pure
Ni. In addition to the formation of the Cu6Sn5 phase, a new Sn-rich phase, denoted the Q phase, is found in the Ni-V substrate couples. Nucleation of the Ni3Sn4 phase is at a much earlier stage and the rates of consumption of Ni are much higher in Ni-V substrate couples than in Ni
substrate couples. Knowledge of these different reactions is important for proper assessment of the flip chip products. 相似文献
197.
LuJian-wei WANGWan-lu LIAOKe-jun WANGYong-tian LIUCHang-lin ZengQing-gao 《半导体光子学与技术》2005,11(1):61-64
Piezoresistive effect of carbon nanotube films was investigated by a three-point bending test. Carbon nanotubes were synthesized by hot filament chemical vapor deposition. The experimental results showed that the carbon nanotubes have a striking piezoresistive effect. The relative resistance was changed from 0 to 10.5 X 10-2 and 3.25 X 10-2 for doped and undoped films respectively at room temperature when the microstrain under stress from 0 to 500. The gauge factors for doped and undoped carbon nanotube films under 500 microstrain were about 220 and 67 at room temperature, respectively, exceeding that of polycrystalline silicon (30) at 35 ℃. The origin of the resistance changes in the films may be attributed to a strain-induced change in the band gap for the doped tubes and the defects for the undoped tubes. 相似文献
198.
Analysis of human behavior through visual information has been one of the active research areas in computer vision community during the last decade. Vision-based human action recognition (HAR) is a crucial part of human behavior analysis, which is also of great demand in a wide range of applications. HAR was initially performed via images from a conventional camera; however, depth sensors have recently embedded as an additional informative resource to cameras. In this paper, we have proposed a novel approach to largely improve the performance of human action recognition using Complex Network-based feature extraction from RGB-D information. Accordingly, the constructed complex network is employed for single-person action recognition from skeletal data consisting of 3D positions of body joints. The indirect features help the model cope with the majority of challenges in action recognition. In this paper, the meta-path concept in the complex network has been presented to lessen the unusual actions structure challenges. Further, it boosts recognition performance. The extensive experimental results on two widely adopted benchmark datasets, the MSR-Action Pairs, and MSR Daily Activity3D indicate the efficiency and validity of the method. 相似文献
199.
I. Allie 《Discrete Mathematics》2019,342(2):387-392
Let be a bridgeless cubic graph. Oddness (weak oddness) is defined as the minimum number of odd components in a 2-factor (an even factor) of , denoted as (Steffen, 2004) ( Lukot’ka and Mazák (2016)). Oddness and weak oddness have been referred to as measurements of uncolourability (Fiol et al., 2017, Lukot’ka and Mazák, 2016, Lukot’ka et al., 2015 and, Steffen, 2004), due to the fact that and if and only if is 3-edge-colourable. Another so-called measurement of uncolourability is resistance, defined as the minimum number of edges that can be removed from such that the resulting graph is 3-edge-colourable, denoted as (Steffen, 2004). It is easily shown that . While it has been shown that the difference between any two of these measures can be arbitrarily large, it has been conjectured that , and that if is a snark then (Fiol et al., 2017). In this paper, we disprove the latter by showing that the ratio of oddness to weak oddness can be arbitrarily large. We also offer some insights into the former conjecture by defining what we call resistance reducibility, and hypothesizing that almost all cubic graphs are such resistance reducible. 相似文献
200.
介绍了压接连接技术的概念和特点,比较了压接连接与锡焊连接的特点及优势;对电子产品中常用的各种冷压端子进行了归类,介绍了闭合压线筒端子、开式压线筒端子的压接方法、工艺技术要求及检验标准;总结了压接工艺中导线的选用与处理方法、工具的使用及要求以及导线端头的处理等通用工艺。 相似文献