全文获取类型
收费全文 | 76247篇 |
免费 | 6857篇 |
国内免费 | 4075篇 |
专业分类
电工技术 | 4650篇 |
技术理论 | 4篇 |
综合类 | 5717篇 |
化学工业 | 12704篇 |
金属工艺 | 4176篇 |
机械仪表 | 4172篇 |
建筑科学 | 6332篇 |
矿业工程 | 2062篇 |
能源动力 | 2474篇 |
轻工业 | 5671篇 |
水利工程 | 1374篇 |
石油天然气 | 3893篇 |
武器工业 | 478篇 |
无线电 | 9056篇 |
一般工业技术 | 8879篇 |
冶金工业 | 3577篇 |
原子能技术 | 1005篇 |
自动化技术 | 10955篇 |
出版年
2024年 | 353篇 |
2023年 | 1355篇 |
2022年 | 2315篇 |
2021年 | 3254篇 |
2020年 | 2441篇 |
2019年 | 2316篇 |
2018年 | 2364篇 |
2017年 | 2622篇 |
2016年 | 2281篇 |
2015年 | 3057篇 |
2014年 | 3766篇 |
2013年 | 4499篇 |
2012年 | 4654篇 |
2011年 | 4942篇 |
2010年 | 4420篇 |
2009年 | 4225篇 |
2008年 | 4073篇 |
2007年 | 3794篇 |
2006年 | 3842篇 |
2005年 | 3209篇 |
2004年 | 2654篇 |
2003年 | 3093篇 |
2002年 | 3970篇 |
2001年 | 3214篇 |
2000年 | 1953篇 |
1999年 | 1725篇 |
1998年 | 1228篇 |
1997年 | 1047篇 |
1996年 | 1011篇 |
1995年 | 800篇 |
1994年 | 651篇 |
1993年 | 442篇 |
1992年 | 391篇 |
1991年 | 245篇 |
1990年 | 204篇 |
1989年 | 154篇 |
1988年 | 156篇 |
1987年 | 83篇 |
1986年 | 80篇 |
1985年 | 56篇 |
1984年 | 56篇 |
1983年 | 33篇 |
1982年 | 37篇 |
1981年 | 21篇 |
1980年 | 23篇 |
1979年 | 21篇 |
1976年 | 9篇 |
1975年 | 4篇 |
1965年 | 6篇 |
1959年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Yi‐Hung Chen Ching‐Yuan Chang Wei‐Ling Su Chun‐Yu Chiu Yue‐Hwa Yu Pen‐Chi Chiang Chiung‐Fen Chang Je‐Lueng Shie Chyow‐San Chiou Sally IM Chiang 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(1):68-75
This study investigates the ozonation of CI Reactive Black 5 (RB5) by using the rotating packed bed (RPB) and completely stirred tank reactor (CSTR) as ozone contactors. The RPB, which provides high gravitational force by adjusting the rotational speed, was employed as a novel ozone contactor. The same ozone dosage was separately introduced into either the RPB or the CSTR for the investigation, while the experimental solution was continuously circulated within the apparatus consisting of the RPB and CSTR. The decolorization and mineralization efficiencies of RB5 in the course of ozonation are compared for these two methods. Moreover, the dissolved and off‐gas ozone concentrations were simultaneously monitored for the further analysis. As a result, the ozone mass transfer rate per unit volume of the RPB was significantly higher because of its higher mass transfer coefficient and gas–liquid concentration driving force. Furthermore, ozonation kinetics was found to be independent of the gravitational magnitude of an ozone gas–liquid contactor. Therefore, the results suggest employing RPBs as ozone‐contacting devices with the advantage of volume reduction. The experimental results, which can be used for further modeling of the ozonation process in the RPB, also show the requirement of correct design for the RPB. Consequently, the present study is useful for the understanding of practical application of RPBs. Copyright © 2004 Society of Chemical Industry 相似文献
32.
33.
CHING-HUA Su YI-GAO Sha S. L Lehoczky F. R Szofran D. C Gillies S. D Cobb R. N Scripa 《Journal of Materials Science》1997,32(14):3765-3768
A series of Hg0.84Zn0.16 Te crystal ingots have been grown from pseudobinary melts by the Bridgmam–Stockbarger type directional solidification using
a Marshall Space Flight Center/Space Science Laboratory heat-pipe furnace and the ground control experiment laboratory furnace
of the crystal growth furnace which was flown on the first United States Microgravity Mission. A number of translation rates
and a series of hot- and cold-zone temperatures were employed to assess the influence of growth parameters on the crystal
properties for the purpose of optimizing the in-flight growth conditions.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
34.
RT-AGVS是物流管理中十分重要的课题,车辆位置监测网是其重要的组成部分。本文详细介绍了一个基于单片机系统的车辆位置实时监测网,本监测网设计先进,性能价格比高,它的设计方法和技术对其他许多领域有借鉴作用。 相似文献
35.
Han-Bin Lin Jung-Young Su Yu-Pin Liao Way-Seen Wang 《Quantum Electronics, IEEE Journal of》1995,31(6):1131-1139
By using micro-prisms, improved three-dimensional (3-D) bends of the embedded and buried waveguides of step-index profile are proposed. A simple phase compensation rule for the optimal design of the micro-prism is also presented. Through the simulation of 3-D semivectorial finite-difference beam propagation method, the transmission characteristics of the improved bends are shown to have been enhanced dramatically as compared with those of the conventional ones. Even for a bend angle of as large as 10°, the normalized transmitted power can still be greater than 95%. These results of 3-D bends are then compared with those of the two-dimensional (2-D) ones which are simplified from 3-D structures by the effective index method, and physical explanation of the discrepancy between the 3-D and 2-D results is introduced. The influences of waveguide structures and prism parameters on the transmission characteristics are discussed in detail. Some criteria for the design of large-angle low-loss 3-D improved bends are also accessed 相似文献
36.
随着汽车数量的迅速增加,汽车排放的有害废气也急剧增加,人们的健康受到威胁,解决这一问题的最好办法是发展清洁代用燃料汽车。介绍了天然气汽车和液化石油气汽车的主要优点,分析了目前我国清洁代用燃料汽车的发展现状,阐述了近期适宜发展我国清洁代用燃料汽车的机遇和面临的困难。最后就提高人们的环保意识、修改和完善汽车尾气污染控制法及排放标准、清洁代用燃料汽车的有关标准和安全措施。对发展这种汽车应给予优惠政策以及零部件生产和车辆改装企业的管理等方面,提出了建议。 相似文献
37.
38.
39.
Sarkar T.K. Su C. Adve R. Salazar-Palma M. Garcia-Castillo L. Boix R.R. 《Antennas and Propagation Magazine, IEEE》1998,40(5):49-68
The objective of this paper is to present the subject of wavelets from a filter-theory perspective, which is quite familiar to electrical engineers. Such a presentation provides both physical and mathematical insights into the problem. It is shown that taking the discrete wavelet transform of a function is equivalent to filtering it by a bank of constant-Q filters, the non-overlapping bandwidths of which differ by an octave. The discrete wavelets are presented, and a recipe is provided for generating such entities. One of the goals of this tutorial is to illustrate how the wavelet decomposition is carried out, starting from the fundamentals, and how the scaling functions and wavelets are generated from the filter-theory perspective. Examples (including image compression) are presented to illustrate the class of problems for which the discrete wavelet techniques are ideally suited. It is interesting to note that it is not necessary to generate the wavelets or the scaling functions in order to implement the discrete wavelet transform. Finally, it is shown how wavelet techniques can be used to solve operator/matrix equations. It is shown that the “orthogonal-transform property” of the discrete wavelet techniques does not hold in numerical computations 相似文献
40.
一种多径环境下基于四阶累积量的阵列扩展测向方法 总被引:3,自引:0,他引:3
本文分析了基于四阶累积量的测向方法不能正确测量多径信号方向的原因,提出了一种多径环境下的基于四阶累积量的新型测向方法。该方法利用零点领处理方法抑制多径信号,然后采用四阶累积量进行阵列扩展测向。计算机模拟结果表明该方法在多径环境下具有良好的性能并且可能实现对足够多的信号进行测向。 相似文献