全文获取类型
收费全文 | 1426678篇 |
免费 | 24995篇 |
国内免费 | 6905篇 |
专业分类
电工技术 | 34002篇 |
综合类 | 6322篇 |
化学工业 | 267261篇 |
金属工艺 | 63257篇 |
机械仪表 | 39865篇 |
建筑科学 | 44358篇 |
矿业工程 | 11258篇 |
能源动力 | 50098篇 |
轻工业 | 101789篇 |
水利工程 | 14165篇 |
石油天然气 | 37476篇 |
武器工业 | 143篇 |
无线电 | 194062篇 |
一般工业技术 | 270370篇 |
冶金工业 | 124899篇 |
原子能技术 | 33794篇 |
自动化技术 | 165459篇 |
出版年
2021年 | 15410篇 |
2020年 | 11698篇 |
2019年 | 14465篇 |
2018年 | 14612篇 |
2017年 | 13885篇 |
2016年 | 20617篇 |
2015年 | 17140篇 |
2014年 | 28484篇 |
2013年 | 87420篇 |
2012年 | 33152篇 |
2011年 | 44372篇 |
2010年 | 40965篇 |
2009年 | 49860篇 |
2008年 | 41863篇 |
2007年 | 38670篇 |
2006年 | 42608篇 |
2005年 | 37201篇 |
2004年 | 39674篇 |
2003年 | 39673篇 |
2002年 | 39061篇 |
2001年 | 35315篇 |
2000年 | 34141篇 |
1999年 | 32523篇 |
1998年 | 32510篇 |
1997年 | 31686篇 |
1996年 | 30404篇 |
1995年 | 27889篇 |
1994年 | 26501篇 |
1993年 | 26383篇 |
1992年 | 25398篇 |
1991年 | 22366篇 |
1990年 | 22805篇 |
1989年 | 21858篇 |
1988年 | 20320篇 |
1987年 | 18690篇 |
1986年 | 18007篇 |
1985年 | 21364篇 |
1984年 | 21913篇 |
1983年 | 19870篇 |
1982年 | 18989篇 |
1981年 | 19037篇 |
1980年 | 17624篇 |
1979年 | 18254篇 |
1978年 | 17476篇 |
1977年 | 16722篇 |
1976年 | 16740篇 |
1975年 | 15802篇 |
1974年 | 15338篇 |
1973年 | 15391篇 |
1972年 | 12885篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
801.
The authors report the design of a new current-mode A/D converter, based on a modified successive-approximations model, in 1.2 μm CMOS technology. The proposed circuit is characterised by good accuracy and fast dynamic performance, low power consumption and small occupation area. SPICE simulations allow the design approach to be validated and the electrical performance of the ADC to be predicted 相似文献
802.
Recent progress in optical time-division-multiplexed (TDM) transmission technologies is reviewed including optical short pulse generation, time-division multiplexing/demultiplexing, timing extraction, and waveform measurement. The latest 400-Gbit/s transmission experiments based on optical signal processing are presented and the possibility of terabit/second TDM transmission is discussed 相似文献
803.
Weian Huang Fuhrmann D.R. Politte D.G. Thomas L.J. Jr. States D.J. 《IEEE transactions on bio-medical engineering》1998,45(4):422-428
In four-color fluorescence-based automated DNA sequencing, a 4×4 filter matrix parameterizes the relationship between the dye-intensity signals of interest and the data collected by an optical imaging system. The filter matrix is important because the estimated DNA sequence is based on the dye intensities that can only be recovered via inversion of the matrix. Here, the authors present a calibration method for the estimation of the columns of this matrix, using data generated through a special experiment in which DNA samples are labeled with only one fluorescent dye at a time. Simulations and applications of the method to real data are provided, with promising results 相似文献
804.
Presents the Satellite Communications Network Expert (SaNE), a knowledge-based aid designed to provide engineering support for fault diagnosis. The SaNE is composed of two elements: a satcom network model, which simulates the structure and functionality of a system based loosely upon a large military satcom network, and a diagnostic component, which uses knowledge- and model-based reasoning techniques to analyse system anomalies and diagnose possible causes for the alarms such networks generate. The development cycle is described, emphasising lessons learnt during development and testing and the advantages and disadvantages of the techniques applied. The goal of the SaNE project is primarily commercial acceptance rather than innovation. The authors illustrate how novel concepts can be implemented in a practical system without compromising this goal 相似文献
805.
806.
College readers read and answered questions on 12 short essays. Essays formatted so that points between phrases had fractional extra space added to them were comprehended better than normally formatted text. These improvements were specific to average readers. Practically, the results justify classroom research on the benefits of phrase-sensitive formatting; theoretically, the results add to existing evidence that poor to average readers specifically lack perceptual strategies for grouping word sequences into phrases. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
807.
An antenna array for wideband operation (up to 70%) is presented. The structure has low windloading area and consists of parallel printed circuit boards (PCB) with microstrip dipoles, feed network and metal fences placed between the PCBs. The low profile, low weight antenna array forms the main beam and three difference patterns for sidelobe cancellation. Experimental results are compared with calculations for both microstrip dipole and array 相似文献
808.
Kang-Ngee Chia Hea Joung Kim Lansing S. Mangione-Smith W.H. Villasensor J. 《Very Large Scale Integration (VLSI) Systems, IEEE Transactions on》1998,6(3):364-371
Under the Mojave configurable computing project, we have developed a system for achieving high performance on an automatic target recognition (ATR) application through the use of configurable computing technology. The ATR system studied here involves real-time image acquisition from a synthetic aperture radar (SAR). SAR images exhibit statistical properties which can be used to improve system performance. In this paper, the Mojave configurable computing system uses field programmable gate arrays (FPGA's) to implement highly specialized circuits while retaining the flexibility of programmable components. A controller sequences through a set of specialized circuits in response to real-time events. Computer-aided design (CAD) tools have been developed to support the automatic generation of these specialized circuits. The resulting configurable computing system achieves a significant performance advantage over the existing solution, which is based on application specific integrated circuit (ASIC) technology 相似文献
809.
810.
Thin microtomed samples from hot-tool butt welds of polypropylene pipes are subjected to uniaxial tensile stress using a specially built instrumented microtesting machine. The deformation of the interface between the weld and the bulk polymer is measured by an optical method. An analysis of these measurements is carried out using the finite element method, and contours of the effective stress are obtained. There is a steep stress gradient at the junction of the weld flash and the bulk polymer, although the stress concentration factor is relatively low. The stress is essentially constant in the bulk polymer apart from the region near the weld zone. Tests on samples without the weld flash show that the maximum stress occurs within the weld zone. This is consistent with long-term tests on larger samples, where the fracture is found to initiate within the weld. The method of analysis enables the stress-strain response of the weld material to be determined. 相似文献