全文获取类型
收费全文 | 17408篇 |
免费 | 2177篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 1367篇 |
综合类 | 404篇 |
化学工业 | 8649篇 |
金属工艺 | 251篇 |
机械仪表 | 384篇 |
建筑科学 | 667篇 |
矿业工程 | 167篇 |
能源动力 | 94篇 |
轻工业 | 1814篇 |
水利工程 | 123篇 |
石油天然气 | 69篇 |
无线电 | 361篇 |
一般工业技术 | 2934篇 |
冶金工业 | 221篇 |
原子能技术 | 26篇 |
自动化技术 | 2058篇 |
出版年
2023年 | 624篇 |
2022年 | 333篇 |
2021年 | 682篇 |
2020年 | 670篇 |
2019年 | 582篇 |
2018年 | 560篇 |
2017年 | 392篇 |
2016年 | 621篇 |
2015年 | 809篇 |
2014年 | 837篇 |
2013年 | 1414篇 |
2012年 | 561篇 |
2011年 | 445篇 |
2010年 | 782篇 |
2009年 | 931篇 |
2008年 | 436篇 |
2007年 | 394篇 |
2006年 | 291篇 |
2005年 | 278篇 |
2004年 | 226篇 |
2003年 | 218篇 |
1998年 | 191篇 |
1997年 | 140篇 |
1996年 | 204篇 |
1995年 | 186篇 |
1994年 | 158篇 |
1993年 | 220篇 |
1992年 | 154篇 |
1991年 | 122篇 |
1990年 | 155篇 |
1989年 | 175篇 |
1988年 | 138篇 |
1987年 | 162篇 |
1986年 | 184篇 |
1985年 | 165篇 |
1984年 | 169篇 |
1983年 | 177篇 |
1982年 | 156篇 |
1981年 | 203篇 |
1980年 | 167篇 |
1979年 | 169篇 |
1977年 | 149篇 |
1976年 | 151篇 |
1975年 | 202篇 |
1974年 | 190篇 |
1973年 | 365篇 |
1972年 | 212篇 |
1971年 | 151篇 |
1970年 | 145篇 |
1968年 | 153篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
Ohne Zusammenfassung 相似文献
6.
E. Griese Prof. Dr.-Ing. 《e & i Elektrotechnik und Informationstechnik》2003,120(6):186-191
Optical interconnection technology on the printed circuit board level is a key technology for future microelectronic equipment. The consideration of functional, technological, and economical requirements results in a hybrid solution, where electrical and optical interconnects are integrated into one substrate called electrical optical printed circuit board. The significant part of the entire design process for electrical optical printed circuit boards is marked by the design supporting modelling and simulation of optical interconnects. Based on an abstract model for an entire optical interconnect a simulation model for optical multimode-waveguides is presented, taking into account all significant waveguide properties. Apart from that, the modeling of active components (laser- and photo-diodes) is addressed. 相似文献
7.
Fluvial processes of erosion, sediment transport and deposition determine the changing form and sedimentary structure of naturally adjusting riparian zones. Riparian sediment storage has both scientific and management importance in relation to: (i) the quantities of sediment that are involved; (ii) the quality of the sediment; and (iii) the dispersal of biological materials, notably the vegetation propagules that are transported and deposited in association with the sediment. After discussing the significance of riparian sedimentation processes, this paper reviews methods for quantifying contemporary sediment deposition within water bodies and their margins. Methods for investigating contemporary riparian sedimentation are given particular emphasis, and the extent to which different methods provide comparable estimates and have been used to support the analysis of different physical and chemical properties of the sediment are outlined. The importance of the following are stressed: (i) selecting a sampling method that is suited to the sedimentation environment; (ii) incorporating careful cross‐calibration if measurements from different methods are to be combined; and (iii) replicating measurements to give more robust estimates if small traps are employed. It is concluded that artificial turf mats provide a useful design of sediment trap across a range of environmental conditions because: (i) their surface roughness reduces problems of sediment removal by flood waters or rainfall; (ii) their pliability permits installation on irregular surfaces; (iii) they can be securely attached to the ground with metal pins to resist high shear stresses from river flows; (iv) they are robust and light and so easily manipulated in the field and laboratory; (v) it is possible to fully recover the deposited sediment to accurately determine the amount of sediment deposited and to support a range of other analyses. Results are presented to illustrate how artificial turf mats can be used to estimate the quantity and quality of deposited sediment and to explore the associated deposition of viable seeds. This provides one example of the important hydroecological role of riparian sedimentation processes and of the potential for the development of innovative, interdisciplinary research on riparian sediment dynamics. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
8.
9.
Dr.-Ing. Holger Boche 《Forschung im Ingenieurwesen》1996,62(10):291-299
Zusammenfassung Bei der praktischen Anwendung der analytischen Signale ist es erforderlich, die Ermittlung der Hilbert-Transformation numerisch
durchzuführen. Dazu wurden u.a. Verfahren von H.W. Schü?ler, R. Unbehauen und G. Wunsch vorgeschlagen. In der Arbeit werden
allgemeine Ergebnisse zur numerischen Umsetzung der Hilbert-Transformation dargestellt. Es wird gezeigt, da? alle praktisch
realisierbaren Verfahren für bestimmte Signale divergieren. Damit ist es m?glich, die in der Experimentalphysik schon l?nger
bekannten Schwierigkeiten bei der Umsetzung der Hilbert-Transformation zu erkl?ren. 相似文献
10.
Summary This paper presents the free vibration of thin doubly-curved shallow shells of rectangular planform. The study covers wide combinations of free, simply supported and clamped boundary conditions. Both positive and negative Gaussian curvatures (spherical and hyperbolic paraboloidal shells resepectively) are considered. Thepb-2 Ritz energy based approach, along with the in-plane and transverse deflections assumed in the form of a product of mathematically complete two-dimensional orthogonal polynomials and a basic function, is employed to model the vibratory characteristic of these shells. Numerical results have been established through convergence study and comparison with published data from the open literature. Extensive sets of new results for various ranges of aspect ratio, curvature ratio andx- andy-shallowness ratios have been presented for future reference. 相似文献