全文获取类型
收费全文 | 21163篇 |
免费 | 953篇 |
国内免费 | 311篇 |
专业分类
电工技术 | 473篇 |
综合类 | 546篇 |
化学工业 | 3839篇 |
金属工艺 | 522篇 |
机械仪表 | 733篇 |
建筑科学 | 880篇 |
矿业工程 | 180篇 |
能源动力 | 573篇 |
轻工业 | 2214篇 |
水利工程 | 246篇 |
石油天然气 | 178篇 |
武器工业 | 27篇 |
无线电 | 2392篇 |
一般工业技术 | 2878篇 |
冶金工业 | 3711篇 |
原子能技术 | 170篇 |
自动化技术 | 2865篇 |
出版年
2023年 | 97篇 |
2022年 | 271篇 |
2021年 | 518篇 |
2020年 | 283篇 |
2019年 | 350篇 |
2018年 | 403篇 |
2017年 | 380篇 |
2016年 | 426篇 |
2015年 | 375篇 |
2014年 | 556篇 |
2013年 | 1048篇 |
2012年 | 836篇 |
2011年 | 1024篇 |
2010年 | 773篇 |
2009年 | 834篇 |
2008年 | 833篇 |
2007年 | 847篇 |
2006年 | 734篇 |
2005年 | 628篇 |
2004年 | 695篇 |
2003年 | 916篇 |
2002年 | 1204篇 |
2001年 | 1015篇 |
2000年 | 593篇 |
1999年 | 537篇 |
1998年 | 1334篇 |
1997年 | 861篇 |
1996年 | 637篇 |
1995年 | 428篇 |
1994年 | 318篇 |
1993年 | 350篇 |
1992年 | 196篇 |
1991年 | 152篇 |
1990年 | 145篇 |
1989年 | 133篇 |
1988年 | 131篇 |
1987年 | 109篇 |
1986年 | 112篇 |
1985年 | 150篇 |
1984年 | 85篇 |
1983年 | 90篇 |
1982年 | 83篇 |
1981年 | 102篇 |
1980年 | 98篇 |
1979年 | 61篇 |
1978年 | 49篇 |
1977年 | 100篇 |
1976年 | 192篇 |
1975年 | 51篇 |
1973年 | 52篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
131.
A. Witvrouw K. Maex W. De Ceuninck G. Lekens J. D'Haen L. De Schepper 《Microelectronics Reliability》1998,38(6-8)
The degradation due to stress induced voiding of nitride passivated Al-1 wt.% Si and Ti/TN/ Al-1wt.% Si-0.5 wt. % Cu/Ti/TN interconnects with widths ranging between 0.4 and 1.2 μm was studied by in-situ conventional
high resolution resistance measurements (HRRM) during storage at temperatures between 168 and 240°C. The conventional measurements on Al-Si lines, which lasted more than one year, clearly showed that the interconnect lifetime decreases with decreasing line width. With HRRM the degradation due to stress induced voiding can be detected much sooner and with much more detail. From the HRRM it is clear that the resistance changes during storage often happen in jumps and that the degradation has a rather complex alloy, line width and temperature dependence. Both for 0.4 and 0.6 μm wide Al---Si lines more degradation occurred for storage at 175 °C compared to storage at 200 °C. For the Al---Si---Cu stacks the degradation of 0.4 μm wide lines was worse for storage at 240°C compared to storage at 200 °C, but the opposite was true for the 0.6 μm wide lines. 相似文献
132.
Weikle R.M. II Kim M. Hacker J.B. De Lisio M.P. Popovic Z.B. Rutledge D.B. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1992,80(11):1800-1809
Although quasi-optical techniques are applicable to a large variety of solid-state devices, special attention is given to transistors, which are attractive because they can be used as either amplifiers or oscillators. Experimental results for MESFET bar-grid and planar grid oscillators are presented. A MESFET grid amplifier that receives only vertically polarized waves at the input and radiates horizontally polarized waves at the output is discussed. These planar grids can be scaled for operation at millimeter- and submillimeter-wave frequencies. By using modern IC fabrication technology, planar grid oscillators and amplifiers containing thousands of devices can be built, thereby realizing an efficient means for large-scale power combining 相似文献
133.
134.
Balasa F. Catthoor F. Hugo De Man 《Very Large Scale Integration (VLSI) Systems, IEEE Transactions on》1995,3(2):157-172
Memory cost is responsible for a large amount of the chip and/or board area of customized video and image processing system realizations. In this paper, we present a novel technique-founded on data-flow analysis which allows one to address the problem of background memory size evaluation for a given nonprocedural algorithm specification, operating on multidimensional signals with affine indexes. Most of the target applications are characterized by a huge number of signals, so a new polyhedral data-flow model operating on groups of scalar signals is proposed. These groups are obtained by a novel analytical partitioning technique, allowing to select a desired granularity, depending on the application complexity. The method incorporates a way to tradeoff memory size with computational and controller complexity 相似文献
135.
Pb1–x
Ca
x
[(Co0.5W0.5)0·05Ti0.95]O3 ceramics with x = 0.24, 0.30 and 0.35, are prepared by a solid state reaction of oxides. Deviations from nominal chemical compositions and formation of segregated phases different from modified lead titanate perovskites, are studied. Pyro- and non-pyroelectric currents excited in the material by a thermal wave are investigated and related to mobility of electrical charges in the materials. 相似文献
136.
To make exploring a locale's heritage a challenging and compelling experience, the Venice Game uses a handheld platform and educational software that leverages video game techniques. 相似文献
137.
The conclusions are put forward that are adopted by a discussion group preparing the framework for a limitation policy of the radon problem in Belgium. Existing and future situations are treated in a coherent policy that is adequate for practical implementation. An action level is defined, together with a hierachy of levels for new constructions. The decision logic for the acceptance of building materials is explained. 相似文献
138.
J. Buytaert L. De Boeck F. Verbeure
C. Bricman
F. Cao C. De Clercq L. Etienne B. Goorens J. Lemonne F. Stichelbaut S. Tavernier G. Van Beek C. Vander Velde W. Van Doninck L. Van Lancker J. WickensE. Daubie
F. Defontaines F. Grard J. Kesteman O. Pingot C. Poiret 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1991,310(3):596-606The layout and construction of the muon drift chambers equipping the end caps of the DELPHI detector are described. The performance of this forward muon detection system, determined from cosmic ray tests and data collected during the first year of LEP operation, is presented. 相似文献
139.
140.
An overview of FDA medical device regulation as it relates to deep brain stimulation devices. 总被引:1,自引:0,他引:1
Carlos Pe?a Kristen Bowsher Ann Costello Robert De Luca Sara Doll Khan Li Marie Schroeder Theodore Stevens 《IEEE transactions on neural systems and rehabilitation engineering》2007,15(3):421-424
The United States Food and Drug Administration (FDA) is charged with assuring the safety and effectiveness of a variety of medical products and the FDA's Center for Devices and Radiological Health is responsible for premarket and postmarket regulation of medical devices. In this paper, we review--from device classification and clinical studies to the final marketing application--FDA's premarket requirements and postmarket requirements as they relate to deep brain stimulation devices. 相似文献