全文获取类型
收费全文 | 188289篇 |
免费 | 3345篇 |
国内免费 | 1465篇 |
专业分类
电工技术 | 4180篇 |
综合类 | 1067篇 |
化学工业 | 29410篇 |
金属工艺 | 8401篇 |
机械仪表 | 5863篇 |
建筑科学 | 5345篇 |
矿业工程 | 1198篇 |
能源动力 | 5024篇 |
轻工业 | 17134篇 |
水利工程 | 1962篇 |
石油天然气 | 3549篇 |
武器工业 | 176篇 |
无线电 | 21275篇 |
一般工业技术 | 34576篇 |
冶金工业 | 33625篇 |
原子能技术 | 4415篇 |
自动化技术 | 15899篇 |
出版年
2021年 | 1789篇 |
2019年 | 1551篇 |
2018年 | 2425篇 |
2017年 | 2460篇 |
2016年 | 2534篇 |
2015年 | 2091篇 |
2014年 | 3336篇 |
2013年 | 8426篇 |
2012年 | 5303篇 |
2011年 | 7240篇 |
2010年 | 5866篇 |
2009年 | 6658篇 |
2008年 | 6625篇 |
2007年 | 6587篇 |
2006年 | 5772篇 |
2005年 | 5294篇 |
2004年 | 4916篇 |
2003年 | 4456篇 |
2002年 | 4498篇 |
2001年 | 4526篇 |
2000年 | 4162篇 |
1999年 | 4226篇 |
1998年 | 10506篇 |
1997年 | 7525篇 |
1996年 | 5767篇 |
1995年 | 4377篇 |
1994年 | 3692篇 |
1993年 | 3628篇 |
1992年 | 2636篇 |
1991年 | 2559篇 |
1990年 | 2435篇 |
1989年 | 2454篇 |
1988年 | 2394篇 |
1987年 | 2134篇 |
1986年 | 2075篇 |
1985年 | 2373篇 |
1984年 | 2188篇 |
1983年 | 2014篇 |
1982年 | 1881篇 |
1981年 | 1945篇 |
1980年 | 1798篇 |
1979年 | 1819篇 |
1978年 | 1776篇 |
1977年 | 2108篇 |
1976年 | 2688篇 |
1975年 | 1557篇 |
1974年 | 1549篇 |
1973年 | 1607篇 |
1972年 | 1350篇 |
1971年 | 1262篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Stievano I.S. Maio I.A. Canavero F.G. Siviero C. 《Advanced Packaging, IEEE Transactions on》2006,29(1):31-38
This paper addresses the impact of device macromodels on the accuracy of signal integrity and performance predictions for critical digital interconnecting systems. It exploits nonlinear parametric models for both single-ended and differential devices, including the effects of power supply fluctuations and receiver bit detection. The analysis demonstrates that the use of well-designed macromodels dramatically speeds up the simulation as well it preserves timing accuracy even for long bit sequences. 相似文献
32.
It was found that vanadyl porphyrin complexes synthesized from petroleum metal porphyrin concentrates stimulated epoxidation during the olefin oxygenation process. The yields of obtained oxiranes turned out to be 38–75%, depending on the olefin structure. An epoxidation mechanism that suggests the formation of a protonated dioxygen adduct as an intermediate during oxygenation of olefins in the presence of vanadyl porphyrin complexes was proposed. An analogy is drawn between the epoxide formation reaction upon the catalytic oxygenation of olefins and the Prilezhaev reaction. 相似文献
33.
The Magnitogorsk Metallurgical Combine has conducted a study of the effect of technological factors on the hydrogen content
of chromium-nickel-molybdenum steel after vacuum degassing. It was established that the most important factor is the hydrogen
content of the steel before the degassing operation. The study also determined the effects of the circulation coefficient,
the duration of the degassing operation, and the vacuum used in the treatment.
__________
Translated from Metallurg, No. 7, pp. 68–69, July, 2006. 相似文献
34.
de Oliveira J.C. Hosseini M. Shirmohammadi S. Malric F. Nourian S. El Saddik A. Georganas N.D. 《Multimedia, IEEE》2003,10(3):18-29
Using Java-based tools in multimedia collaborative environments accessed over the Internet can increase an application's client base. Most operating systems support Java, and its "compile once-run everywhere" architecture is easy to maintain and update. The Java-based tools presented here let users share Internet resources, including resources originally designed for single use. 相似文献
35.
At some point in their careers, clinicians who work or consult in forensic and correctional settings will almost certainly encounter individuals who exhibit psychopathic personality features. Because of the widespread use of this disorder to inform legal and clinical decision making, psychologists should be exceedingly familiar with the relevant research literature on this topic before venturing into these settings. This article reviews the empirical bases of several clinically relevant claims and assertions regarding psychopathy and concludes that many areas of research are decidedly more equivocal in their findings than is commonly perceived. Although there is much to be gained by assessing psychopathy in various contexts, clinicians need to be cautious about drawing overzealous and empirically questionable conclusions about an important disorder that also has great potential for abuse. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
36.
The application of barrier discharges at atmospheric pressure in air expands on the market of plasma technology, because it is an ecological and cost‐effective alternative to other processes of surface treatment. These plasmas usually consist of a multitude of spatially and temporally localized filaments, whose distribution should be as even as possible for homogeneous treatment. This holds especially for the plasma treatment of sensitive goods such as wool or other textiles. In equipment for continuous pass of material the barrier arrangements often consist of a system cylinder – cylinder or cylinder – plane, whereby the gap width changes locally. Space distribution and intensity of filaments has been investigated by means of short‐time photography and spatially resolved measurement of current distribution and energy distribution derived from it. The local dependency found can be explained by means of a capacitive equivalent circuit. 相似文献
37.
Ciofi C. Crupi F. Pace C. Scandurra G. 《IEEE transactions on instrumentation and measurement》2003,52(5):1533-1536
Low-frequency noise measurements represent an interesting investigation technique for the characterization of the quality and reliability of microelectronic materials and devices. Performing meaningful noise measurements at low and very low (f<1 Hz) frequencies, however, may be quite challenging, particularly because of the many sources of interference that superimpose on the noise signal. For this reason, packaged samples are preferred because they allow accurate shielding from the external environment, and because keeping the sample in close proximity to the low-noise biasing system and amplifier reduces microphonic and electromagnetic disturbances. Notwithstanding this, the possibility of performing low-frequency noise measurements at wafer level would be quite interesting, both because of the ease of obtaining wafer-level samples from industries with respect to packaged samples, and because this would avoid possible packaging-process induced device degradation. The purpose of this work is to demonstrate that it is, in fact, possible to design and build a dedicated probe system for performing high-sensitivity, low-frequency noise measurements on metal-oxide-semiconductor devices at wafer level. 相似文献
38.
Piedade M. Sousa L. A. de Almeida T. M. Germano J. da Costa B. A. Lemos J. M. Freitas P. P. Ferreira H. A. Cardoso F. A. 《IEEE transactions on circuits and systems. I, Regular papers》2006,53(11):2384-2395
This paper presents a hand-held microsystem based on new fully integrated magnetoresistive biochips for biomolecular recognition (DNA hybridization, antibody antigen interaction, etc.). Magnetoresistive chip surfaces are chemically treated, enabling the immobilization of probe biomolecules such as DNA or antibodies. Fluid handling is also integrated in the biochip. The proposed microsystem not only integrates the biochip, which is an array of 16times16 magnetoresistive sensors, but it also provides all the electronic circuitry for addressing and reading out each transducer. The proposed architecture and circuits were specifically designed for achieving a compact, programmable and portable microsystem. The microsystem also integrates a hand-held analyzer connected through a wireless channel. A prototype of the system was already developed and detection of magnetic nanoparticles was obtained. This indicates that the system may be used for magnetic label based bioassays 相似文献
39.
1 Introduction
Along with the matureness of laser diode (LD) manufacturing technology, the performance of LD has been improved greatly since 1980s, so various kinds of laser devices based on LD have been developed rapidly, especially the all-solid state lasers. After early experiments and researches, the all-solid state lasers have been commercialized successfully. 相似文献
40.
Dell'Amico M. Maffioli F. Merani M.L. 《Wireless Communications, IEEE Transactions on》2004,3(4):1013-1017
This paper proposes some novel techniques to accommodate users with different rate requirements in a wideband code-division multiple-access system employing orthogonal variable spreading factor codes. Two simple static code assignment strategies are first considered, and an improvement based on multicode assignment. Then the new idea of tree partitioning is introduced and used to devise a dynamic code reassignment algorithm. The behavior of these different techniques is experimentally investigated, in terms of call blocking probability and number of required reassignments. The tree partitioning method exhibits very good performances. 相似文献