全文获取类型
收费全文 | 22640篇 |
免费 | 1463篇 |
国内免费 | 928篇 |
专业分类
电工技术 | 1403篇 |
综合类 | 1426篇 |
化学工业 | 1294篇 |
金属工艺 | 2638篇 |
机械仪表 | 1879篇 |
建筑科学 | 1805篇 |
矿业工程 | 486篇 |
能源动力 | 368篇 |
轻工业 | 1370篇 |
水利工程 | 250篇 |
石油天然气 | 1887篇 |
武器工业 | 266篇 |
无线电 | 2021篇 |
一般工业技术 | 2995篇 |
冶金工业 | 729篇 |
原子能技术 | 176篇 |
自动化技术 | 4038篇 |
出版年
2024年 | 71篇 |
2023年 | 202篇 |
2022年 | 307篇 |
2021年 | 442篇 |
2020年 | 464篇 |
2019年 | 396篇 |
2018年 | 420篇 |
2017年 | 594篇 |
2016年 | 685篇 |
2015年 | 892篇 |
2014年 | 1316篇 |
2013年 | 1263篇 |
2012年 | 1517篇 |
2011年 | 1647篇 |
2010年 | 1391篇 |
2009年 | 1360篇 |
2008年 | 1371篇 |
2007年 | 1514篇 |
2006年 | 1370篇 |
2005年 | 1232篇 |
2004年 | 1015篇 |
2003年 | 917篇 |
2002年 | 786篇 |
2001年 | 688篇 |
2000年 | 553篇 |
1999年 | 472篇 |
1998年 | 398篇 |
1997年 | 292篇 |
1996年 | 276篇 |
1995年 | 220篇 |
1994年 | 176篇 |
1993年 | 133篇 |
1992年 | 120篇 |
1991年 | 96篇 |
1990年 | 78篇 |
1989年 | 48篇 |
1988年 | 43篇 |
1987年 | 22篇 |
1986年 | 15篇 |
1985年 | 30篇 |
1984年 | 27篇 |
1983年 | 30篇 |
1982年 | 30篇 |
1981年 | 10篇 |
1978年 | 9篇 |
1965年 | 17篇 |
1962年 | 7篇 |
1959年 | 5篇 |
1957年 | 5篇 |
1955年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
主要讨论印刷电路板(PCB)移动探针测试中软件及检测中遇到特殊情况的处理,并对造成通短路现象的原因进行了分析,以达到保证PCB产品质量的目的。 相似文献
32.
W. Claeys V. Quintard S. Dilhaire D. Lewis Y. Danto 《Quality and Reliability Engineering International》1994,10(4):289-295
We have recently developed an optical contactless method for testing the quality of solder joints during accelerated thermal cycling ageing processes.1 The method was based upon the measurement of the dynamic thermal behaviour of the joint to short bursts of Joule heating. It has proved to be efficient in revealing the formation of cracks at the lead-solder interface. We present a method to evaluate ageing at a much earlier stage in the cycling process. We have observed in earlier work,1 that before cracks appear, structural changes occur in the solder at the lead-solder interface. The thermal response of the solder joint is recorded over time to a Peltier heat perturbation produced by flowing a current pulse through the interface where structural changes occur. The key point in this method is to discriminate the Peltier effect from the Joule thermal response because both effects generate heat. The variation of the early Peltier response in the thermal cycling ageing tests is seen as a quantitative signature of the structural changes in the lead-solder interface. 相似文献
33.
A new principle and arrangement for directly determining the angle of incidence of an optical beam on an object are proposed and demonstrated. The novelty of the approach lies in the realization of a ‘smart object’, which extracts a portion of the incident beam's power into an optical waveguide attached to the object's surface or embedded in its body for converting the angle of incidence into the position of a guided beam with finite lateral extent. This ‘integrated optical light pointer’ beam is accomplished by means of creating additional degrees of freedom on the target in two different ways. While a first type is based on introducing spatial variations of the waveguide thickness, a second type makes use of a chirp of the grating periodicity. The feasibility for practical applications has been experimentally demonstrated by a direct comparison with a commercial high-resolution encoder, resulting in an r.m.s. error of <30′'. Measurements have been performed for chips fabricated based on replicated polycarbonate substrates and with no external optics, showing the great potential of this approach for realizing low-cost yet high-performance miniature goniometers. 相似文献
34.
Contemporary approaches to the certification of measurement provision software are considered in domestic and overseas publications.
Normative documentation is analyzed and a scheme is proposed for certification that takes account of the features of programs
used for metrological purposes.
__________
Translated from Izmeritel’naya Tekhnika, No. 5, pp. 65–68, May, 2007. 相似文献
35.
振动采油工艺在稠油区的实验研究与应用 总被引:5,自引:2,他引:3
在天然地震的影响下,油井产量发生波动,使人们受到启示,从而引进了振动采油工艺技术。本文对振动增产的机理进行了探讨,指出振动增油机理在于加快地层中流体的流速;改变储集层内油、气、水的重新分布;改变岩石表面润湿性,有利于清除油层堵塞,提高渗透率。通过分析两个试验区的振动采油效果,总结出在不同扰动力、不同激振频率、不同振动周期下的增产效果和规律,对振动采油的实施具有一定的指导意义。 相似文献
36.
Seven hundred three members of the Society for Industrial and Organizational Psychology indicated agreement or disagreement with 49 propositions regarding cognitive ability tests in organizations. There was consensus that cognitive ability tests are valid and fair, that they provide good but incomplete measures, that different abilities are necessary for different jobs, and that diversity is valuable. Items dealing with the unique status of cognitive ability were most likely to generate polarized opinions. A 2-factor model, classifying items as those reflecting societal concerns over the consequences of ability testing and those reflecting an emphasis on the unique status of "g," fit the data well, and these factors proved especially important for predicting responses to the more controversial items. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
37.
利用双种群遗传算法进行数值试井自动拟合 总被引:7,自引:0,他引:7
遗传算法以随机化技术为指导,通过对整个解空间的高效搜索而得到全局最优解,当解空间较大时,常规遗传算法难以同时保证搜索速度和最优解的精度。针对这种缺陷提出了应用双种群遗传算法,即利用具有不同搜索策略的2个种群进行联合搜索,既保证了最优解的精度,又提高了搜索速度,将其应用于数值试井自动拟合解释,比常规遗传算法能节省50%以上的计算时间。 相似文献
38.
Power devices with high capability have been developed. 8‐kV/3.5‐kA‐class light‐triggered thyristors have the highest capability among power devices. These devices are used in the Kii Channel HVDC transmission system in Japan. In this paper, we report the extracted problems of conventional testing methods of 8‐kV/3.5‐kA‐class light‐triggered thyristors among manufacturers, and the proposed unified testing methods on the basis of element characteristics and operating conditions in the Kii Channel HVDC system. Furthermore, we propose a figure of merit for power devices for the practical use, and try to extract elements used at the Kii Channel HVDC system with small margins and low withstand capabilities. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 140(3): 61–70, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10024 相似文献
39.
小型密闭压力容器测试(MCPVT)法是安全工程领域中近几年发展起来的、评价有机过氧化物及自反应物质受热分解反应激烈程度的新方法。pmax是MCPVT方法中用来表征自反应物质受热分解反应激烈程度的物理量之一。文中通过大量实验,研究了样品容器容积V、升温速率R及样品质量M对pmax重复性误差的影响,研究了一系列典型的有机过氧化物和自反应物质在标准实验条件下pmax重复性误差。结果表明,小型密闭压力容器测试系统重复性好,测试结果可靠,从而为MCPVT法最终成为国际上评价自反应物质受热分解反应激烈程度标准方法奠定了基础。 相似文献
40.