全文获取类型
收费全文 | 9202篇 |
免费 | 1274篇 |
国内免费 | 707篇 |
专业分类
电工技术 | 818篇 |
综合类 | 1360篇 |
化学工业 | 633篇 |
金属工艺 | 248篇 |
机械仪表 | 662篇 |
建筑科学 | 700篇 |
矿业工程 | 184篇 |
能源动力 | 206篇 |
轻工业 | 239篇 |
水利工程 | 176篇 |
石油天然气 | 153篇 |
武器工业 | 117篇 |
无线电 | 1214篇 |
一般工业技术 | 1488篇 |
冶金工业 | 282篇 |
原子能技术 | 61篇 |
自动化技术 | 2642篇 |
出版年
2024年 | 35篇 |
2023年 | 116篇 |
2022年 | 149篇 |
2021年 | 244篇 |
2020年 | 336篇 |
2019年 | 333篇 |
2018年 | 357篇 |
2017年 | 370篇 |
2016年 | 457篇 |
2015年 | 409篇 |
2014年 | 523篇 |
2013年 | 657篇 |
2012年 | 674篇 |
2011年 | 678篇 |
2010年 | 479篇 |
2009年 | 526篇 |
2008年 | 505篇 |
2007年 | 585篇 |
2006年 | 491篇 |
2005年 | 428篇 |
2004年 | 397篇 |
2003年 | 384篇 |
2002年 | 307篇 |
2001年 | 278篇 |
2000年 | 250篇 |
1999年 | 170篇 |
1998年 | 153篇 |
1997年 | 160篇 |
1996年 | 121篇 |
1995年 | 91篇 |
1994年 | 95篇 |
1993年 | 62篇 |
1992年 | 69篇 |
1991年 | 42篇 |
1990年 | 42篇 |
1989年 | 31篇 |
1988年 | 28篇 |
1987年 | 15篇 |
1986年 | 16篇 |
1985年 | 12篇 |
1984年 | 9篇 |
1983年 | 5篇 |
1982年 | 11篇 |
1981年 | 15篇 |
1980年 | 8篇 |
1979年 | 8篇 |
1978年 | 7篇 |
1966年 | 5篇 |
1964年 | 13篇 |
1963年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
介绍一种微波高频段带通滤波器的设计方法,同时给出一个滤波器的设计实例和测试结果。利用制作简单的园棒内导体结构,采用梳状线与同轴腔相结合的方式,实现窄带带通滤波器,达到结构紧凑、性能优良、方便组件集成的使用效果。 相似文献
13.
As we approach 100 nm technology the interconnect issues are becoming one of the main concerns in the testing of gigahertz system-on-chips. Voltage distortion (noise) and delay violations (skew) contribute to the signal integrity loss and ultimately functional error, performance degradation and reliability problems. In this paper, we first define a model for integrity faults on the high-speed interconnects. Then, we present a BIST-based test methodology that includes two special cells to detect and measure noise and skew occurring on the interconnects of the gigahertz system-on-chips. Using an inexpensive test architecture the integrity information accumulated by these special cells can be scanned out for final test and reliability analysis. 相似文献
14.
Yong Xia Rongming Lin 《International journal for numerical methods in engineering》2004,59(1):153-172
Order reduction is a computationally efficient method to estimate some lowest eigenvalues and the corresponding eigenvectors of large structural systems by reducing the order of the original model to a smaller one. But its accuracy is limited to a small range of frequencies that depends on the selection of the retained degrees of freedom. This paper proposes a new iterative order reduction (IOR) technique to obtain accurately the eigensolutions of large structural systems. The technique retains all the inertia terms associated with the removed degrees of freedom. This hence leads to the reduced mass matrix being in an iterated form and the reduced stiffness matrix constant. From these mass and stiffness matrices, the eigensolutions of the reduced system can be obtained iteratively. On convergence the reduced system reproduces the eigensolutions of the original structure. A proof of the convergence property is also presented. Applications of the method to a practical GARTEUR structure as well as a plate have demonstrated that the proposed method is comparable to the commonly used Subspace Iteration method in terms of numerical accuracy. Moreover, it has been found that the proposed method is computationally more efficient than the Subspace Iteration method. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
15.
Rolf G. Kuehni 《Color research and application》2008,33(1):5-9
Some 100 years before Albert Munsell developed his color order system, French silk merchant and inventor of a technology for producing works of art in silk velours, Gaspard Grégoire, introduced a color order system based on the color attributes hue, (relative) chroma, and lightness. Conceived in the mid‐1780s, an atlas with 1350 samples was produced before 1813 and found use in French Royal manufacturing operations and educational institutions. It was followed a few years later by one with 343 samples. Grégoire's work was subsequently overshadowed by Michel‐Eugene Chevreul's more complicated and less intuitive hemispherical system of 1839. © 2007 Wiley Periodicals, Inc. Col Res Appl, 33, 5–9, 2008 相似文献
16.
17.
本文研究了具有典型分解特征的Al-Zn-Ce非晶合金的形成和晶化过程,探讨了各种相的生成顺序。XRD和DSC测试结果表明强烈的化合物短程序有利于Al-Zn-Ce非晶合金的形成。在Al-Zn-Ce非晶合金的晶化过程中存在复杂的相选择行为,多种相的竞争形核和有限生长使其具有复杂的结构特点。同时,结果也表明冷速对该体系非晶的形成有很大影响。 相似文献
18.
Delevoye-Turrell Yvonne; Giersch Anne; Wing Alan M.; Danion Jean-Marie 《Canadian Metallurgical Quarterly》2007,116(1):56
Many everyday activities depend on the capacity to organize and smoothly execute motor sequences. The authors tested the hypothesis that a sequencing deficit is associated with schizophrenia. They used a new method to distinguish between lower and higher order mechanisms for the impairment. The 1st task involved triggered sequences in which sensory information from 1 movement was the cue for initiation of the following movement. Results showed that the motor sequences were performed as fluently in patients as in controls. The 2nd and 3rd tasks involved sequences in which the entire movement sequence could be preplanned. Patients executed the sequences less fluently than controls but only under the condition where action sequences were required. Furthermore, the patients' fluency deficit increased with sequence complexity. The high discrimination power of Task 3 gave the authors a means to control for a potential psychometric confound involving differential discriminating power and to argue in favor of a specific higher order motor fluency deficit in patients with schizophrenia. It is suggested that basic lower order mechanisms that integrate sensory information with outgoing motor commands are preserved in schizophrenia, whereas higher order integrative mechanisms that are required for the smooth coordination of motor sequences are impaired. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
19.
已往库存论中的决策模型,它是把现实过程用数学的方法进行分析,得到决策值,但不能看到决策的过程,不能反映出现实生活中的不确定性、动态性。运用Delphi 7.0和SQL server 2000对销售过程进行了动态仿真,利用Newsboy模型的推广(S,s)订购策略来监控库存并做出决策,这样就体现出此过程的不确定性、动态性;且举出了一个仿真商品销售的实例,对其中的一些关键技术,如何仿真、算法的实现等进行了阐述。 相似文献
20.
In this report, we describe the nature of intermediate order in silicon as determined by recent measurements on thin films using transmission electron microscopy (TEM) and Raman scattering. The TEM images show in addition to the expected continuous random network (CRN), the presence of highly ordered quasi-one-dimensional “chain-like objects” (CLO's) that are 1–2 nm wide and tens of nm long that meander and show some evidence of cross-linking with each other. The presence of these objects correlate to a Raman feature centered at 490 cm−1 whose width is 35–40 cm−1, and is used to quantify the heterogeneity in terms of the CLO and CRN (=475 cm−1 scattering) concentrations. The 490 and 35 cm−1 values are consistent with bond angle deviations approaching 0°, and thus reinforces an association with the CLOs. We find that in reference quality a-Si:H (made using pure SiH4), the CLO concentration is about 5 vol%, while in state-of-the-art material using high H2 levels of dilution during processing, it increases to about 15%. Increased stability of such material to light-soaking is thus not mediated by a direct volumetric replacement of poor with high-quality components. Rather, an important characteristic of intermediate order in silicon is the low-dimensional aspect of its order, which allows it to influence more total volume than which it is itself composed. Consistent with these and other recent findings, we propose a tensegrity model of amorphous silicon. 相似文献