全文获取类型
收费全文 | 216702篇 |
免费 | 15208篇 |
国内免费 | 9523篇 |
专业分类
电工技术 | 9010篇 |
技术理论 | 8篇 |
综合类 | 16435篇 |
化学工业 | 32428篇 |
金属工艺 | 12646篇 |
机械仪表 | 18602篇 |
建筑科学 | 31761篇 |
矿业工程 | 6170篇 |
能源动力 | 5186篇 |
轻工业 | 10634篇 |
水利工程 | 4895篇 |
石油天然气 | 6969篇 |
武器工业 | 2124篇 |
无线电 | 18941篇 |
一般工业技术 | 28915篇 |
冶金工业 | 6401篇 |
原子能技术 | 1808篇 |
自动化技术 | 28500篇 |
出版年
2024年 | 789篇 |
2023年 | 2992篇 |
2022年 | 4872篇 |
2021年 | 6014篇 |
2020年 | 5865篇 |
2019年 | 4955篇 |
2018年 | 4614篇 |
2017年 | 5772篇 |
2016年 | 6471篇 |
2015年 | 6914篇 |
2014年 | 13734篇 |
2013年 | 12182篇 |
2012年 | 14473篇 |
2011年 | 17006篇 |
2010年 | 13676篇 |
2009年 | 14659篇 |
2008年 | 12893篇 |
2007年 | 15047篇 |
2006年 | 12830篇 |
2005年 | 11340篇 |
2004年 | 9213篇 |
2003年 | 8544篇 |
2002年 | 7007篇 |
2001年 | 5339篇 |
2000年 | 4633篇 |
1999年 | 3697篇 |
1998年 | 2982篇 |
1997年 | 2440篇 |
1996年 | 2145篇 |
1995年 | 1677篇 |
1994年 | 1458篇 |
1993年 | 1045篇 |
1992年 | 820篇 |
1991年 | 686篇 |
1990年 | 463篇 |
1989年 | 440篇 |
1988年 | 312篇 |
1987年 | 247篇 |
1986年 | 203篇 |
1985年 | 160篇 |
1984年 | 166篇 |
1983年 | 127篇 |
1982年 | 145篇 |
1981年 | 62篇 |
1980年 | 77篇 |
1979年 | 59篇 |
1978年 | 25篇 |
1977年 | 29篇 |
1976年 | 24篇 |
1975年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
31.
32.
A.L. Pan H.G. ZhengZ.P. Yang F.X. Liu Z.J. Ding Y.T. Qian 《Materials Research Bulletin》2003,38(5):789-796
Small Ag particles or clusters dispersed mesoporous SiO2 composite films were prepared by a new method: First the matrix SiO2 films were prepared by sol-gel process combined with the dip-coating technique, then they were soaked in AgNO3 solutions followed by irradiation of γ-ray at room temperature and in ambient pressure. The structures of these films were examined by X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM), and optical absorption spectroscopy. It has been shown that the Ag particles grown within the porous SiO2 films are very small, and they are isolated and dispersed from each other with very narrow size distributions. With increasing the soaking concentration and an additional annealing, an opposite peakshift effect of the surface plasmon resonance (SPR) was observed in the optical absorption measurements. 相似文献
33.
提出了一种在SNMPv3体系结构下实现的计费模型,讨论了其PDU格式,计费过程和SNMP实体的结构,该模型对现有SNMPv3体系结构作了最小的改动,它的提出增强了SNMP的重要性,扩展了SNMP的应用范围。v 相似文献
34.
Frank te Beest Ad Peeters Kees van Berkel Hans Kerkhoff 《Journal of Electronic Testing》2003,19(4):397-406
Handshake circuits form a special class of asynchronous circuits that has enabled the industrial exploitation of the asynchronous potential such as low power, low electromagnetic emission, and increased cryptographic security. In this paper we present a test solution for handshake circuits that brings synchronous test-quality to asynchronous circuits. We add a synchronous mode of operation to handshake circuits that allows full controllability and observability during test. This technique is demonstrated on some industrial examples and gives over 99% stuck-at fault coverage, using test-pattern generators developed for synchronous circuits. The paper describes how such a full-scan mode can be achieved, including an approach to minimize the number of dummy latches in case latches are used in the data path of the handshake circuit. 相似文献
35.
优化项目管理MIS系统方案设计 总被引:2,自引:0,他引:2
按照工程项目“五制”管理的要求 ,以规范管理和提升工程质量为系统开发的基础和前提 ,探索适合本行业使用的项目MIS系统设计方案 ,并对其功能模型、数据规划、构造处理模型、数学模型进行分析 相似文献
36.
M. Kaiarov E. Rudnayov J. Koval
ík J. Dusza M. Hnatko P. ajgalík A. Merstallinger 《Materialwissenschaft und Werkstofftechnik》2003,34(4):338-342
In the presented work some properties of a recently developed Si3N4/SiC micro/nanocomposite have been investigated. The material was tested using a pin on disc configuration. Under unlubricated sliding conditions using Si3N4 pin at 50 % humidity, the friction coefficient was in the range of 0,6 ‐ 0,7. The reduction of humidity resulted in a lower coefficient of friction, in vacuum the coefficient of friction had a value of about 0,6. The wear resistance in vacuum was significantly lower then that in air. The wear patterns on the Si3N4+SiC disc revealed that mechanical fracture was the wear controlling mechanism. Creep tests were realized in four point bending configuration in the temperature interval 1200‐1400 °C at stresses 50,100 and 150 MPa and the minimal creep deformation rate was established for each stress level. The activation energy, established from the minimal creep deformation had a value of about 360 kJ/mol and the stress exponent values were in the range of 0.8‐1.28. From the achieved stress exponents it can be assumed that under the studied load/temperature conditions the diffusion creep was the most probable creep controlling mechanism. 相似文献
37.
激光水下成像技术及其进展 总被引:6,自引:0,他引:6
介绍了近年发展起来的三种主要的激光水下成像方法,即常规水下激光成像、高分辨率水下激光三维成像和偏振激光成像,分析了它们各自的工作原理、特点以及各自的发展状况。 相似文献
38.
39.
Over the last five years, many activities have focused on the unexploited field of carrying out reactions on small scales. Due to the rapid development of new components, this paper deals with recent developments only in a compressed form. An important point is the analysis of possible plant concepts for microreactors and whether these are a sensible option. Due to the enormous difference in size between the microchannels and the fluid periphera of possible components this is not just a technical question. It touches on the microtechnology concept as a whole. The direction in which the field should be developed and which measures can be taken to influence its development are questions that are addressed here with respect to the big industrial interest in microreactors. 相似文献
40.
600 A IGBT开关电路及其散热系统设计 总被引:1,自引:0,他引:1
采用IGBT开关电路,对大功率电阻带进行直流脉宽调制控制,实现了内燃机车大功率直流发电机负载实验中的负载大小的连续调节。为了避免在实验过程中IGBT器件的温度过高,采用独特的双管IGBT结构和双向强迫风冷的散热系统。实验表明该电路运行稳定、可靠。 相似文献