全文获取类型
收费全文 | 1829篇 |
免费 | 27篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 97篇 |
综合类 | 3篇 |
化学工业 | 371篇 |
金属工艺 | 36篇 |
机械仪表 | 21篇 |
建筑科学 | 25篇 |
能源动力 | 55篇 |
轻工业 | 149篇 |
水利工程 | 6篇 |
石油天然气 | 1篇 |
无线电 | 206篇 |
一般工业技术 | 260篇 |
冶金工业 | 460篇 |
原子能技术 | 39篇 |
自动化技术 | 132篇 |
出版年
2023年 | 9篇 |
2021年 | 25篇 |
2020年 | 13篇 |
2019年 | 12篇 |
2018年 | 15篇 |
2017年 | 17篇 |
2016年 | 27篇 |
2015年 | 13篇 |
2014年 | 30篇 |
2013年 | 53篇 |
2012年 | 54篇 |
2011年 | 66篇 |
2010年 | 49篇 |
2009年 | 65篇 |
2008年 | 71篇 |
2007年 | 66篇 |
2006年 | 73篇 |
2005年 | 51篇 |
2004年 | 42篇 |
2003年 | 57篇 |
2002年 | 38篇 |
2001年 | 46篇 |
2000年 | 43篇 |
1999年 | 38篇 |
1998年 | 237篇 |
1997年 | 121篇 |
1996年 | 88篇 |
1995年 | 45篇 |
1994年 | 48篇 |
1993年 | 66篇 |
1992年 | 24篇 |
1991年 | 23篇 |
1990年 | 28篇 |
1989年 | 19篇 |
1988年 | 15篇 |
1987年 | 15篇 |
1986年 | 15篇 |
1985年 | 17篇 |
1984年 | 10篇 |
1983年 | 16篇 |
1982年 | 12篇 |
1981年 | 17篇 |
1980年 | 6篇 |
1979年 | 16篇 |
1978年 | 8篇 |
1977年 | 9篇 |
1976年 | 12篇 |
1974年 | 3篇 |
1973年 | 6篇 |
1969年 | 3篇 |
排序方式: 共有1861条查询结果,搜索用时 109 毫秒
51.
Yoshitaka Sawa Kenji Yamashita Takeshi Kitadani Daiji Noda Tadashi Hattori 《Microsystem Technologies》2010,16(8-9):1369-1375
The nickel electroforming method using a high-concentration nickel sulfamate bath is commonly used to fabricate micro metal molds in the LIGA process; however, this method does not produce micro metal molds of sufficient hardness. One means of improving the hardness of micro metal molds made using the nickel electroforming method is to include additives in the nickel plating solution. Another method is nickel alloy plating or a similar technique. In this research, we used a nickel–boron (Ni–B) electroless alloy plating method to obtain a hard nickel plated film having hardness of 832 Hv. It was also ascertained that Ni–B electroless alloy plated film retains its high hardness even during heat treatment in conditions of 250°C for 1 h. To deal with the high stresses developed in high-hardness plated films, we proposed double-layer nickel electroforming. This method is covered and used on conventional nickel electroforming layer by high hardness micro mold. High hardness micro metal mold using double-layer was fabricated by nickel electroforming and Ni–B electroless alloy plating method. 相似文献
52.
Hiroshige Matsuoka Koji Oka Yusuke Yamashita Fumihiro Saeki Shigehisa Fukui 《Microsystem Technologies》2011,17(5-7):983-990
Thermocapillary deformations of an ultra-thin liquid film caused by temperature distribution were three-dimensionally analyzed using the unsteady and linearized long wave equation considering the temperature and film thickness dependence of surface tension. The temperature and film thickness dependence equation for the surface tension of a liquid was firstly established. The temperature dependence of the surface tension was obtained experimentally using a surface tensiometer and the film thickness dependence was obtained theoretically from the corrected van der Waals pressure equation for a symmetric multilayer system. Time evolutions of depression and groove of the ultra-thin liquid film caused by local heating were obtained quantitatively. 相似文献
53.
54.
Recently, the size of solder bump interconnects have been significantly reduced with the advent of high-density packaging,
and thus the evaluation of electromigration in solder bumps has become necessary. The present paper proposes a simple method
to test the electromigration resistance of Pb-free solders. One of the key points of the present method is the fabrication
of a simple solder sample that can produce sufficient current density to cause electromigration. Moreover, the actual local
temperature of a small area subjected to electromigration in the sample was measured by a direct method. A right-angled diamond-shaped
hole was introduced in a thin film of solder using a focused-ion-beam system. A direct current was supplied to the film far
from the hole, perpendicular to the diagonal of the hole. In this way, the current density was concentrated near to the corner
of the hole, and the value of this was obtained through a theoretical analysis. It was noted that the steady temperature in
the film along a line extending from the diagonal, remained constant, although the current density decreased gradually far
from the corner. Therefore, the temperature at a position near the corner, where electromigration takes place, can easily
be found by measuring the temperature far from the corner. The temperature was measured directly under current flow conditions
by utilizing the chemical reagents with known melting points. Finally, by measuring the ratio of hillock volume to the time
for the current supply as a measure of the atomic flux divergence due to electromigration, the corresponding resistances of
some Pb-free solders to electromigration were evaluated. 相似文献
55.
Sarah Mostame Joonsuk Huh Christoph Kreisbeck Andrew J. Kerman Takatoshi Fujita Alexander Eisfeld Alán Aspuru-Guzik 《Quantum Information Processing》2017,16(2):44
With quantum computers being out of reach for now, quantum simulators are alternative devices for efficient and accurate simulation of problems that are challenging to tackle using conventional computers. Quantum simulators are classified into analog and digital, with the possibility of constructing “hybrid” simulators by combining both techniques. Here we focus on analog quantum simulators of open quantum systems and address the limit that they can beat classical computers. In particular, as an example, we discuss simulation of the chlorosome light-harvesting antenna from green sulfur bacteria with over 250 phonon modes coupled to each electronic state. Furthermore, we propose physical setups that can be used to reproduce the quantum dynamics of a standard and multiple-mode Holstein model. The proposed scheme is based on currently available technology of superconducting circuits consist of flux qubits and quantum oscillators. 相似文献
56.
57.
This paper presents a tabu search approach for scheduling jobs on identical parallel machines with the objective of minimizing the mean tardiness. Initially, we consider a basic tabu search that uses short term memory only. Local search is performed on a neighborhood defined by two types of moves. Insert moves consist of transferring each job from one machine to another and swap moves are those obtained by exchanging each pair of jobs between two machines. Next, we analyze the incorporation of two diversification strategies with the aim of exploring unvisited regions of the solution space. The first strategy uses long term memory to store the frequency of the moves executed throughout the search and the second makes use of influential moves. Computational tests are performed on problems with up to 10 machines and 150 jobs. The heuristic performance is evaluated through a lower bound given by Lagrangean relaxation. A comparison is also made with respect to the best constructive heuristic reported in the literature. 相似文献
58.
We investigate the static and dynamic behavior of vortices in a pin-free superconductor. A diffraction pattern is observed in the critical currentJ
cvs. applied fieldH
parallel to the surface of a granular Al film. When one vortex chain is formed in the film,J
cbecomes nearly equal to zero, which verifies that the sample is actually pin-free. An interaction between a radiofrequency current and moving vortices occurs, and theI–V curve shows peculiar nonlinear effects such as real negative resistance. The results are analogous to dc and ac Josephson effects. 相似文献
59.
A modified pulse-heating method is proposed to improve the accuracy of measurement of the hemispherical total emissivity, specific heat capacity, and electrical resistivity of electrically conductive materials at high temperatures. The proposed method is based on the analysis of a series of rapid resistive self-heating experiments on a sample heated at different temperature rates. The method is used to measure the three properties of the IG-110 grade of isotropic graphite at temperatures from 850 to 1800 K. The problem of the extrinsic heating-rate effect, which reduces the accuracy of the measurements, is successfully mitigated by compensating for the generally neglected experimental error associated with the electrical measurands (current and voltage). The results obtained by the proposed method can be validated by the linearity of measured quantities used in the property determinations. The results are in reasonably good agreement with previously published data, which demonstrate the suitability of the proposed method, in particular, to the resistivity and total emissivity measurements. An interesting result is the existence of a minimum in the emissivity of the isotropic graphite at around 1120 K, consistent with the electrical resistivity results. 相似文献
60.
Low-Ag-based Pb-free solder and its evaluation for electromigration (EM) reliability are research areas of active development. This paper studies the effect of adding Ni and Ge microelements on the EM behavior of low-Ag-based SnAgCu solder. Comparative measurements of the EM resistance of Sn1.0Ag0.5Cu (SAC) and Sn1.0Ag0.5Cu0.07Ni0.01Ge (SACNG) solders (in wt?%) were conducted. In these experiments, SACNG showed a higher EM resistance than SAC. It was concluded that adding Ni and Ge enhanced the EM resistance of low-Ag-based SnAgCu solders. This shows the same effect of Ni and Ge on the EM resistance as that which has been reported for Sn3.5Ag0.5Cu solder. An analysis of these observations suggests that grain boundary sliding plays a dominant role in stress relaxation and causes hillock growth. Based on this assumption, a possible mechanism was proposed to explain the effects of Ni and Ge on the EM resistance of SnAgCu solder. 相似文献