全文获取类型
收费全文 | 1405篇 |
免费 | 97篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 19篇 |
综合类 | 4篇 |
化学工业 | 391篇 |
金属工艺 | 16篇 |
机械仪表 | 26篇 |
建筑科学 | 54篇 |
矿业工程 | 2篇 |
能源动力 | 49篇 |
轻工业 | 170篇 |
水利工程 | 18篇 |
石油天然气 | 5篇 |
无线电 | 134篇 |
一般工业技术 | 228篇 |
冶金工业 | 203篇 |
原子能技术 | 22篇 |
自动化技术 | 162篇 |
出版年
2024年 | 8篇 |
2023年 | 28篇 |
2022年 | 55篇 |
2021年 | 65篇 |
2020年 | 46篇 |
2019年 | 42篇 |
2018年 | 45篇 |
2017年 | 56篇 |
2016年 | 45篇 |
2015年 | 38篇 |
2014年 | 62篇 |
2013年 | 89篇 |
2012年 | 68篇 |
2011年 | 78篇 |
2010年 | 79篇 |
2009年 | 55篇 |
2008年 | 73篇 |
2007年 | 64篇 |
2006年 | 43篇 |
2005年 | 40篇 |
2004年 | 38篇 |
2003年 | 29篇 |
2002年 | 29篇 |
2001年 | 18篇 |
2000年 | 18篇 |
1999年 | 10篇 |
1998年 | 46篇 |
1997年 | 44篇 |
1996年 | 29篇 |
1995年 | 16篇 |
1994年 | 10篇 |
1993年 | 21篇 |
1992年 | 8篇 |
1991年 | 7篇 |
1990年 | 11篇 |
1989年 | 10篇 |
1988年 | 12篇 |
1987年 | 7篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 10篇 |
1983年 | 4篇 |
1980年 | 2篇 |
1979年 | 7篇 |
1978年 | 7篇 |
1977年 | 4篇 |
1976年 | 7篇 |
1972年 | 2篇 |
1964年 | 2篇 |
1959年 | 1篇 |
排序方式: 共有1503条查询结果,搜索用时 15 毫秒
1.
Wireless Networks - Orthogonal frequency-division multiplexing with random multiple access (OFDRMA) is discussed for down-link communications, whereby a single base-station transmits information... 相似文献
2.
Gomes A. C. S. A. Costa L. C. Brito D. C. Frana R. J. Marques Mnica R. C. 《Polymer Bulletin》2020,77(4):1969-1981
Polymer Bulletin - In this study, we synthesized a new ion-imprinted polymer (IIP) based on introduction of amidoxime groups in acrylonitrile, complexation with Cd2+ ions and polymerization with... 相似文献
3.
Martin F. Falcone F. Bonache J. Marques R. Sorolla M. 《Microwave and Wireless Components Letters, IEEE》2003,13(12):511-513
A novel compact stop band filter consisting of a 50 /spl Omega/ coplanar waveguide (CPW) with split ring resonators (SRRs) etched in the back side of the substrate is presented. By aligning SRRs with the slots, a high inductive coupling between line and rings is achieved, with the result of a sharp and narrow rejection band in the vicinity of the resonant frequency of the rings. In order to widen the stop band of the filter, several ring pairs tuned at equally spaced frequencies within the desired gap are cascaded. The frequency response measured in the fabricated prototype device exhibits pronounced slopes at either side of the stop band and near 0 dBs insertion loss outside that band. Since SRR dimensions are much smaller than signal wavelength, the proposed filters are extremely compact and can be used to reject frequency parasitics in CPW structures by simply patterning properly tuned SRRs in the back side metal. Additional advantages are easy fabrication and compatibility with MMIC or PCB technology. 相似文献
4.
Marcos de Carvalho Barcellos Alcino Palermo de Aguiar Mônica Regina Marques Palermo de Aguiar Luiz Claudio de Santa Maria 《Polymer Bulletin》2005,55(1-2):61-70
Summary This article deals with the handy synthesis of sulfonyl resins, which were produced by the treatment of a commercial sulfonic resin (Lewatit VPOC1812® based at divinylbenzene (DVB) and styrene (STY). The preliminary chemical modification was based on the reaction of the Lewatit VPOC1812® with thionyl chloride aiming to produce the sulfonyl chloride groups. The best conditions to obtain the sulfonyl chloride groups were: SOCl2/SO3H (molar ratio) =13 at 79 °C during 72 h. The resin chlorinated was afterward treated with urea, thiourea or guanidine. The functionalized resins with urea, thiourea or guanidine were produced with 56, 68 and 93% yield, respectively. The commercial and modified resins were characterized by apparent density, swelling degree, elemental analysis (CHNS), FTIR, optical microscopy (OM) and scanning electron microscopy (SEM). 相似文献
5.
EF Bernstein FJ Sullivan JB Mitchell GD Salomon E Glatstein 《Canadian Metallurgical Quarterly》1993,20(3):435-453
Radiation therapy exerts both acute and chronic effects on normal tissue included within treatment fields. The physics of radiation therapy and treatment techniques to minimize deleterious effects of radiation are presented. Management of radiation-damaged skin is discussed. Radiation effect on tissue, wound healing, and tumorigenesis also are reviewed. 相似文献
6.
Salthouse Timothy A.; Mitchell Debora R.; Palmon Roni 《Canadian Metallurgical Quarterly》1989,4(4):480
Young and old adults were asked, in 3 experiments, to make decisions about the identity of line segment patterns after either adding or subtracting line segments from the original pattern. On some of the trials, the line segments from the initial display were presented again in the second display to minimize the necessity of remembering early information during the processing of later information. Although this manipulation presumably reduced the importance of memory in the tasks, it had little effect on the magnitude of the age differences in any of the experiments. Because the 2 groups were equivalent in accuracy of simple recognition judgments, but older adults were less accurate when the same types of decisions were required in the context of an ongoing task, the results suggested that older adults may be impaired in the ability to retain information while simultaneously processing the same or other information. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
7.
Marques N.A. Kamon M. Silveira L.M. White J.K. 《Advanced Packaging, IEEE Transactions on》2004,27(4):569-580
As very large scale integration (VLSI) circuit speeds and density continue to increase, the need to accurately model the effects of three-dimensional (3-D) interconnects has become essential for reliable chip and system design and verification. Since such models are commonly used inside standard circuit simulators for time or frequency domain computations, it is imperative that they be kept compact without compromising accuracy, and also retain relevant physical properties of the original system, such as passivity. In this paper, we describe an approach to generate accurate, compact, and guaranteed passive models of RLC interconnects and packaging structures. The procedure is based on a partial element equivalent circuit (PEEC)-like approach to modeling the impedance of interconnect structures accounting for both the charge accumulation on the surface of conductors and the current traveling in their interior. The resulting formulation, based on nodal or mixed nodal and mesh analysis, enables the application of existing model order reduction techniques. Compactness and passivity of the model are then ensured with a two-step reduction procedure where Krylov-subspace moment-matching methods are followed by a recently proposed, nearly optimal, passive truncated balanced realization-like algorithm. The proposed approach was used for extracting passive models for several industrial examples, whose accuracy was validated both in the frequency domain as well as against measured time-domain data. 相似文献
8.
Audiological tests were conducted on 34 patients before and after undergoing an operation in spinal anaesthesia. One of these patients developed a considerable unilateral hearing loss in the low-frequency range, which persisted until an epidural blood-patch was given. Unexpectedly, we also found a general small but significant threshold shift at 500 Hz, which has never before been described in the literature. The biological mechanism is discussed, and the results suggest that the explanation of the hearing loss could be a condition similar to endolymphatic hydrops, resulting from perilymphatic hypotension due to loss of liquor during and after the spinal anaesthesia. 相似文献
9.
Marques R. Rafii-El-Idrissi R. Mesa F. Medina F. 《Microwave Theory and Techniques》2002,50(8):1935-1941
The propagation of leaky forward magnetostatic (MS) volume waves along ferrite-loaded microstrip and slot lines is analyzed. This phenomenon is studied by means of a numerical approach based on the residue calculus technique because of its good numerical convergence and stability. The proposed method allows for a quick and accurate computation of the phase and attenuation constants of the leaky MS modes. A comparative analysis between both microstrip lines and slot lines is carried out, and some new physical effects, such as MS resonances in the radiation loss, are reported. The advantages of the proposed method of analysis over other numerical methods, such as Galerkin's or moment methods, are also discussed. 相似文献
10.